docs: add manual desktop smoke test instructions to README and update CI test script

- Introduce a new section in README detailing the manual desktop smoke test process for the application.
- Include commands for setting up and running the smoke test, along with expected outcomes and logging details.
- Update the CI test script to include the new smoke test script in the shellcheck validation process.

README.md

@@ -7,11 +7,11 @@ Audio and captions stay on your machine. Nothing is uploaded after the one-time
 Captioneer provides two commands:
 
 - `captioneer` is the lightweight, terminal-only command and has no GTK dependency.
-- `captioneer-desktop` adds a GTK4 subtitle overlay and can output to the overlay, terminal, or both. It is built with the `gtk` build tag.
+- `captioneer-desktop` is the GTK4 desktop utility. It manages caption processing, the overlay, caption history, the application Console, and saved settings. It is built with the `gtk` build tag.
 
 ## Setup
 
-The terminal command requires Linux x86_64, Go 1.26.2 or newer, `pactl`, and `parec`. Building the desktop command from source additionally needs GTK4 and GTK4 Layer Shell development libraries. Published release archives carry the desktop runtime libraries. PipeWire works through its PulseAudio compatibility layer.
+The terminal command requires Linux x86_64, Go 1.26.2 or newer, `pactl`, and `parec`. Building the desktop command from source additionally needs GTK4, GTK4 Layer Shell, GObject Introspection, and X11 development libraries. Published release archives carry the desktop runtime libraries. PipeWire works through its PulseAudio compatibility layer.
 
 Download the large recognition models once:
 
@@ -58,19 +58,27 @@ kill -HUP <captioneer-parent-pid>
 
 An automatic or manual restart begins a fresh capture/transcription session; audio being processed by the failed worker cannot be recovered.
 
-## Desktop overlay
+## Desktop application
 
 The simplest Bazzite development command is:
 
 ```bash
-./scripts/distrobox/run.sh --mode=vad --output=overlay
+./scripts/distrobox/run.sh
 ```
 
-Use `--output=both` to keep terminal output as well:
+The main window has three top-level tabs:
 
-```bash
+- **Captions** keeps up to 500 final captions and one mutable live/provisional row. Scrolling upward pauses automatic scrolling; **Jump to Latest** resumes it. Selected text or the full in-memory transcript can be copied.
-./scripts/distrobox/run.sh --mode=vad --output=both
+- **Console** keeps up to 2,000 timestamped diagnostic entries, including startup, capture, model, overload, warning, error, and shutdown messages. It has independent scrolling, copying, and clearing controls.
-```
+- **Settings** exposes the meaningful CLI configuration with validation and folder pickers. Advanced recovery settings are collapsed by default. **Apply & Restart Captions** appears when a recognition change requires restarting a running pipeline.
+
+The header contains the running state, current processing mode, a Start/Stop control, and native GTK window controls. Closing the main window exits Captioneer in this stage. Captions start automatically by default, but this can be changed under **Settings → General**. The overlay, GUI history, stdout captions, stderr diagnostics, and timestamped caption files can all be enabled independently.
+
+Caption logs are final captions only. Each session creates a new file named like `captioneer-2026-07-17_13-45-20.000.log`; every line contains its creation timestamp, audio-relative start/end time, and caption. Lines are flushed immediately. The default directory is `$XDG_STATE_HOME/captioneer/transcripts`, or `~/.local/state/captioneer/transcripts` when `XDG_STATE_HOME` is unset.
+
+The interface deliberately uses one compact olive/gray-green, early-2000s desktop theme. It uses GTK client-side decoration for native dragging, double-click behavior, keyboard access, and window controls rather than imitating those behaviors manually. Replace [`assets/icon/icon.png`](assets/icon/icon.png) to change the header/release icon while keeping the same path.
+
+### Caption overlay behavior
 
 In VAD mode, a 500 ms pause finalizes the current speech segment. Captioneer splits that transcript again at sentence punctuation and at word-safe boundaries of at most 64 characters, so continuous speech does not become one enormous paragraph. The live provisional view keeps the latest three digestible chunks and grows vertically without ellipsizing them. Completed chunks remain visible for at least three seconds, receive extra time based on their word count, and gradually fade from white to a restrained gray as they age. When several chunks finalize together, their removal is staggered in reading order instead of deleting the whole block at once. Up to six completed chunks remain above the provisional text; if a seventh arrives, the oldest is removed. Blank recognition results never erase completed text before its reading lifetime expires.
 
@@ -78,11 +86,11 @@ The expensive Parakeet recognizer stays idle during silence and audio that Siler
 
 Text is left-aligned inside the centered, fixed-width dark bubble and wraps at its configured width instead of extending off-screen. Pointer input passes through the window by default.
 
-To build outside the helper script, install GTK4 and GTK4 Layer Shell development packages, then run:
+To build outside the helper script, install GTK4, GTK4 Layer Shell, GObject Introspection, and X11 development packages, then run:
 
 ```bash
 go build -tags gtk -o build/captioneer-desktop ./src/cmd/captioneer-desktop
-./build/captioneer-desktop --mode=vad --output=overlay
+./build/captioneer-desktop
 ```
 
 ### Wayland and X11 behavior
@@ -97,13 +105,20 @@ Layer Shell and X11 hints are requests, not universal guarantees. Same-layer win
 
 ## Command-line options
 
-`--mode` is required for both commands. `captioneer-desktop` also requires `--output`.
+Both commands use built-in defaults, then the saved configuration, then explicit command-line flags. No mode or output flag is required. The compatibility flag `captioneer-desktop --output=terminal|overlay|both` remains available and changes caption destinations for that launch only.
+
+### Configuration options
+
+| Option | Default | Meaning |
+| --- | --- | --- |
+| `--config=PATH` | XDG path | Read configuration from another JSON file. |
+| `--no-config` | `false` | Ignore saved settings and start from built-in defaults for this launch. |
 
 ### Transcription options
 
 | Option | Default | Meaning |
 | --- | --- | --- |
-| `--mode=vad|fixed` | required | Speech-aware utterances or independent fixed chunks. |
+| `--mode=vad|fixed` | `vad` | Speech-aware utterances or independent fixed chunks. |
 | `--chunk-duration=1s` | `1s` | Fixed chunk length or VAD preview refresh interval. Accepts Go durations such as `500ms` or `2s`. |
 | `--models-dir=models` | `models` | Directory containing `parakeet-tdt-v2/` and `silero_vad_v5.onnx`. |
 | `--threads=2` | `2` | CPU threads used by recognition and VAD. |
@@ -117,7 +132,13 @@ Layer Shell and X11 hints are requests, not universal guarantees. Same-layer win
 
 | Option | Default | Meaning |
 | --- | --- | --- |
-| `--output=terminal|overlay|both` | required | Select desktop-command renderers. `both` falls back to terminal if GTK initialization fails. |
+| `--output=terminal|overlay|both` | saved outputs | Compatibility preset for overlay and stdout caption destinations. |
+| `--gui-history=true|false` | `true` | Retain captions in the bounded GUI history. |
+| `--stderr-diagnostics=true|false` | `true` | Mirror structured diagnostics to stderr as well as the Console. |
+| `--start-captions=true|false` | `true` | Start processing when the desktop window opens. |
+| `--main-window-always-on-top=true|false` | `false` | Best-effort keep-above request for the main window. Supported through X11 window-manager hints; Wayland may reject it. |
+| `--caption-log=true|false` | `false` | Save finalized captions to a timestamped session file. |
+| `--caption-log-dir=PATH` | XDG state path | Directory for caption session logs. |
 | `--overlay-backend=auto|wayland|x11` | `auto` | Let GTK detect the backend, or require one explicitly. |
 | `--overlay-opacity=0.90` | `0.90` | Dark bubble opacity from `0` to `1`. |
 | `--overlay-font-size=28` | `28` | Font size in logical pixels. |
@@ -132,7 +153,7 @@ Examples:
 
 ```bash
 # Larger text, a custom font, and longer final-caption visibility
-./scripts/distrobox/run.sh --mode=vad --output=overlay \
+./scripts/distrobox/run.sh --mode=vad \
   --overlay-font-size=34 --overlay-font-family="Noto Sans" --overlay-final-timeout=6s
 
 # Explicit XWayland/X11 route on the cursor's monitor
@@ -143,10 +164,28 @@ Examples:
   --output=overlay --overlay-monitor=DP-1
 
 # Be more conservative when instrumental music causes false speech detections
-./scripts/distrobox/run.sh --mode=vad --output=overlay \
+./scripts/distrobox/run.sh --mode=vad \
   --vad-threshold=0.65 --preview-threshold-dbfs=-40
 ```
 
+## Saved configuration
+
+The GUI saves a readable, versioned JSON file at:
+
+```text
+$XDG_CONFIG_HOME/captioneer/config.json
+```
+
+When `XDG_CONFIG_HOME` is unset, the normal Linux fallback is `~/.config/captioneer/config.json`. Saving is atomic and creates the directory/file with user-only permissions. Both `captioneer` and `captioneer-desktop` load this file, so ordinary terminal use benefits from the same recognition settings without repeating flags. Explicit flags always win and do not silently rewrite the saved file.
+
+Precedence is unambiguous:
+
+```text
+built-in defaults < saved JSON configuration < explicit command-line flags
+```
+
+Use `--no-config` for a clean one-off launch or `--config=/path/to/config.json` for a separate profile. The GUI's **Help → Open Configuration Folder** opens the active file's parent directory. Caption history itself remains in memory and does not survive application restarts; timestamped caption logging is the opt-in persistent transcript path.
+
 ## Bazzite development with Distrobox
 
 The helper scripts keep GTK development packages off the immutable host. They create and reuse `captioneer-dev` from the pinned `registry.fedoraproject.org/fedora-toolbox:44` image, install only missing packages, enter this mounted repository, and reuse the host's `models/` directory.
@@ -154,7 +193,7 @@ The helper scripts keep GTK development packages off the immutable host. They cr
 Run the desktop command from source:
 
 ```bash
-./scripts/distrobox/run.sh --mode=vad --output=overlay
+./scripts/distrobox/run.sh
 ```
 
 Build both binaries into the host-visible `build/` directory:
@@ -173,7 +212,7 @@ The scripts recognize these environment variables:
 | `CAPTIONEER_DISTROBOX_IMAGE` | `registry.fedoraproject.org/fedora-toolbox:44` | Container image. Override it to test a newer Fedora release deliberately. |
 | `GSK_RENDERER` | `cairo` in `run.sh` only | GTK renderer. The safe software default avoids host/container GPU DMABUF mismatches; an explicit value is preserved. |
 
-Captioneer itself has no environment-based application configuration; use the command-line flags above. The Fedora image is pinned for reproducibility and will not advance automatically. The name and image overrides apply when creating or selecting the container; an existing named container is reused. Update the image intentionally when Fedora 44 is no longer supported. Distrobox provides the normal home, display, session bus, PipeWire/PulseAudio, and runtime-directory integration; the scripts add no broad socket or device mounts.
+Captioneer uses XDG configuration/state locations rather than application-specific environment variables. Use the GUI, JSON file, or command-line flags above. The Fedora image is pinned for reproducibility and will not advance automatically. The name and image overrides apply when creating or selecting the container; an existing named container is reused. Update the image intentionally when Fedora 44 is no longer supported. Distrobox provides the normal home, display, session bus, PipeWire/PulseAudio, and runtime-directory integration; the scripts add no broad socket or device mounts.
 
 ## Troubleshooting
 
@@ -183,7 +222,10 @@ Captioneer itself has no environment-based application configuration; use the co
 - **Music/noise produces captions:** use VAD mode and try `--vad-threshold=0.65`. Increase it in small steps if false detections continue. `--preview-threshold-dbfs=-40` can also reject quiet background audio, but an RMS gate cannot distinguish loud music from speech. Singing may still be treated as speech.
 - **Processing overload warning:** inference fell behind and the oldest 100 ms packet was dropped. Try more `--threads` or a longer `--chunk-duration`.
 - **Overlay is not always above other windows:** read the backend warning. On Wayland this usually means the compositor lacks Layer Shell; add a compositor rule for the `Captioneer Overlay` window if supported.
-- **Overlay initialization fails:** `--output=overlay` exits with the error. `--output=both` warns and continues terminal-only.
+- **Overlay initialization fails:** disable **Settings → Outputs → Caption overlay** and use GUI history or stdout; details remain available in the Console.
+- **Always on top does not work for the main window:** this is a best-effort X11 feature. Generic Wayland intentionally leaves stacking policy to the compositor, and Captioneer reports that limitation in the Console.
+- **Settings do not apply:** validation appears beside the Apply button. Recognition changes restart a running pipeline; an overlay backend change is saved but requires restarting the whole application.
+- **Caption log is missing:** enable **Save timestamped caption log**, verify its directory, then look for the dated per-session file shown in the Console.
 - **A locally built desktop binary misses shared libraries:** use `scripts/distrobox/run.sh` or install the matching GTK4 and GTK4 Layer Shell runtime packages. The desktop command in a published release carries these application libraries in its private `lib/` directory; keep the extracted directory together.
 - **The model worker repeatedly restarts:** inspect the warning on stderr. Slow machines may need a larger `--model-timeout`; use `--model-auto-restart=false` when diagnosing a persistent crash so Captioneer exits on the first failure.
 
@@ -194,8 +236,13 @@ The transcription pipeline emits presentation-neutral events. `output/terminal`
 ```text
 src/app/                 capture/model/process lifecycle
 src/captions/            caption events and fixed/VAD coordination
+src/config/              defaults, CLI precedence, and XDG JSON persistence
+src/diagnostics/         bounded structured application log
+src/gui/                 GTK4 main window, pages, settings, and styling
+src/output/history/      bounded GUI caption history
 src/output/terminal/     terminal renderer
 src/output/overlay/      private GTK4/Layer Shell CGO adapter
+src/output/transcript/   timestamped final-caption files
 src/cmd/captioneer/      terminal command
 src/cmd/captioneer-desktop/ GTK-tagged desktop command
 ```
@@ -221,6 +268,18 @@ distrobox enter --no-workdir captioneer-dev -- bash -lc '
 
 Run this from the repository root. The build and run helpers resolve that path automatically.
 
+### Manual desktop smoke test
+
+`scripts/smoke/desktop-smoke.sh` boots a nested headless Wayland desktop (sway) inside the `captioneer-dev` Distrobox, routes synthesized `espeak-ng` speech through a temporary PipeWire null sink, runs the real `build/captioneer-desktop` binary against it, and fails on ERROR diagnostics, an unclean shutdown, or an empty caption transcript.
+
+```bash
+./scripts/download-models.sh      # once, if models/ is missing
+./scripts/distrobox/build.sh      # produce build/captioneer-desktop
+./scripts/smoke/desktop-smoke.sh
+```
+
+Exit `0` means pass; a report is written under `build/smoke/<timestamp>/report.txt` together with the application logs and caption transcripts. The harness installs `sway` and `espeak-ng` into the Distrobox on demand and restores the previous default sink when it finishes. If VAD recognition of synthetic speech proves flaky, rerun with `CAPTIONEER_SMOKE_MODE=fixed`. This test is manual-only and intentionally not part of CI: it needs downloaded models, a nested compositor, and live audio routing.
+
 ## Gitea Actions and releases
 
 The `Tests` workflow runs the normal and GTK-tagged Go tests, `go vet`, and ShellCheck for every pull request and branch push. To make it mandatory for pull requests, open the repository's **Settings → Branches**, edit the protection rule for `master`, enable required status checks, and select **Tests / Go and GTK tests** after its first run. Workflow files can report the check, but the branch-protection rule is what prevents merging when it fails.
@@ -240,4 +299,4 @@ The release workflow uses Gitea's built-in `GITEA_TOKEN`; no personal token is r
 
 Captioneer is licensed under the [Apache License 2.0](LICENSE). Sherpa-Onnx is Apache-2.0 licensed, GTK4 is LGPL-2.1-or-later, and GTK4 Layer Shell is MIT licensed. Release archives dynamically link and redistribute the required shared libraries; `RUNTIME-LIBRARIES.tsv` records their source packages and `third-party-licenses/` contains the installed license notices supplied by those packages. Local source builds continue to link against the system libraries.
 
-Version 1 intentionally has no animation, persisted caption history, runtime dragging, background-free mode, capture exclusion, Flatpak, desktop entry, or autostart integration.
+This first GUI stage intentionally has no system tray, start-at-login behavior, global shortcuts, notifications, transcript database, cloud sync, plugin system, remote control, automatic updates, multiple themes, or full terminal emulator. Closing the main window exits the application; background availability belongs to the later tray phase.

go.mod

@@ -2,4 +2,13 @@ module tea.chunkbyte.com/kato/captioneer
 
 go 1.26.2
 
-require github.com/k2-fsa/sherpa-onnx-go-linux v1.13.4
+require (
+	github.com/diamondburned/gotk4/pkg v0.3.1
+	github.com/k2-fsa/sherpa-onnx-go-linux v1.13.4
+)
+
+require (
+	github.com/KarpelesLab/weak v0.1.1 // indirect
+	go4.org/unsafe/assume-no-moving-gc v0.0.0-20231121144256-b99613f794b6 // indirect
+	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c // indirect
+)

go.sum

@@ -1,2 +1,10 @@
+github.com/KarpelesLab/weak v0.1.1 h1:fNnlPo3aypS9tBzoEQluY13XyUfd/eWaSE/vMvo9s4g=
+github.com/KarpelesLab/weak v0.1.1/go.mod h1:pzXsWs5f2bf+fpgHayTlBE1qJpO3MpJKo5sRaLu1XNw=
+github.com/diamondburned/gotk4/pkg v0.3.1 h1:uhkXSUPUsCyz3yujdvl7DSN8jiLS2BgNTQE95hk6ygg=
+github.com/diamondburned/gotk4/pkg v0.3.1/go.mod h1:DqeOW+MxSZFg9OO+esk4JgQk0TiUJJUBfMltKhG+ub4=
 github.com/k2-fsa/sherpa-onnx-go-linux v1.13.4 h1:FpEUVeTtdkUlb+YToY8rCWFmvB+zT70YKIKdvnDWIzU=
 github.com/k2-fsa/sherpa-onnx-go-linux v1.13.4/go.mod h1:NXEH2rsBgTdqY59YpPq6CtSBlBAXy/8a9FmpLERU97I=
+go4.org/unsafe/assume-no-moving-gc v0.0.0-20231121144256-b99613f794b6 h1:lGdhQUN/cnWdSH3291CUuxSEqc+AsGTiDxPP3r2J0l4=
+go4.org/unsafe/assume-no-moving-gc v0.0.0-20231121144256-b99613f794b6/go.mod h1:FftLjUGFEDu5k8lt0ddY+HcrH/qU/0qk+H8j9/nTl3E=
+golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
+golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

plan_smoke_test.md

@@ -0,0 +1,122 @@
+---
+name: Desktop smoke harness
+overview: Add a Distrobox-based nested Wayland desktop smoke test that boots a headless compositor, plays synthesized speech into a temporary PipeWire null sink, runs captioneer-desktop, and fails on errors or missing captions — fast enough for manual runs, realistic enough to catch integration breakages.
+todos:
+  - id: smoke-lib
+    content: Add scripts/smoke/lib.sh (null sink, espeak fixture, wait helpers, cleanup traps)
+    status: completed
+  - id: smoke-script
+    content: Add scripts/smoke/desktop-smoke.sh orchestrating labwc + captioneer-desktop + assertions
+    status: completed
+  - id: smoke-deps
+    content: On-demand Distrobox package install for labwc/espeak-ng (and ffmpeg if needed)
+    status: completed
+  - id: smoke-docs-ci
+    content: Document in README; ShellCheck the new scripts from scripts/ci/test.sh
+    status: in_progress
+isProject: false
+---
+
+# Desktop smoke harness
+
+## Approach (chosen default)
+
+**Not a full QEMU VM.** A nested Wayland compositor inside the existing Distrobox is the better tradeoff: boots in seconds, still exercises GTK, Layer Shell, Pulse capture, model worker, and caption logging. Full VMs add minutes of boot/image management without much extra signal for this app.
+
+```mermaid
+flowchart TD
+  host[Host PipeWire] --> nullSink[temp null sink]
+  script[desktop-smoke.sh] --> box[captioneer-dev Distrobox]
+  box --> labwc[labwc headless Wayland]
+  box --> app[captioneer-desktop]
+  nullSink --> play[paplay espeak WAV]
+  nullSink --> app
+  app --> log[stderr diagnostics]
+  app --> transcript[caption-log dir]
+  script --> assert[pass/fail report]
+  log --> assert
+  transcript --> assert
+```
+
+## What you will run
+
+```bash
+./scripts/download-models.sh   # once, if models/ missing
+./scripts/distrobox/build.sh   # ensure build/captioneer-desktop exists
+./scripts/smoke/desktop-smoke.sh
+```
+
+Exit `0` = pass. Prints a short report under `build/smoke/`.
+
+## Harness layout
+
+| Path | Role |
+| --- | --- |
+| [`scripts/smoke/desktop-smoke.sh`](scripts/smoke/desktop-smoke.sh) | Orchestrator (manual entrypoint) |
+| [`scripts/smoke/lib.sh`](scripts/smoke/lib.sh) | Shared helpers: null sink, espeak fixture, wait/assert |
+| Extend [`scripts/distrobox/common.sh`](scripts/distrobox/common.sh) | Add smoke packages: `labwc`, `espeak-ng`, `ffmpeg` (or keep install-on-demand in smoke script to avoid bloating every build) |
+
+**Package strategy:** install smoke deps on demand inside `desktop-smoke.sh` via `sudo dnf install -y` in the Distrobox (same pattern as `ensure_dependencies`), so normal `build.sh` / `run.sh` stay lean.
+
+## Test sequence
+
+1. **Preflight**
+   - Require Distrobox, `build/captioneer-desktop`, `models/parakeet-tdt-v2/`, `models/silero_vad_v5.onnx`
+   - Create work dir `build/smoke/<timestamp>/`
+
+2. **Audio sandbox (host-visible via Distrobox Pulse integration)**
+   - `pactl load-module module-null-sink sink_name=captioneer-smoke`
+   - Save/restore previous default sink
+   - `pactl set-default-sink captioneer-smoke`
+   - Synthesize a short clear English line with `espeak-ng` → WAV in the work dir
+   - Loop-play with `paplay` for ~15–20s so VAD/fixed mode has time to finalize
+
+3. **Nested desktop**
+   - Start `labwc` (wlroots, Layer Shell capable) with `WLR_BACKENDS=headless WLR_LIBINPUT_NO_DEVICES=1`
+   - Export `WAYLAND_DISPLAY` to that socket; `GSK_RENDERER=cairo`
+
+4. **Launch Captioneer**
+   ```bash
+   ./build/captioneer-desktop \
+     --no-config \
+     --start-captions=true \
+     --output=both \
+     --stderr-diagnostics=true \
+     --caption-log=true \
+     --caption-log-dir="$workdir/transcripts" \
+     --models-dir=models \
+     --mode=vad \
+     --model-auto-restart=false
+   ```
+   - Redirect stderr to `$workdir/captioneer.stderr.log`
+   - Present main window first (already true in current [`src/gui/app.go`](src/gui/app.go)), so compositor + GUI come up before capture
+
+5. **Settle + stop**
+   - Wait until stderr contains `Model worker ready` (timeout ~60s)
+   - Keep playing speech ~15s more
+   - Send clean shutdown (`gdbus` `app.exit` or SIGINT)
+   - Wait for exit; unload null sink; kill labwc
+
+6. **Assertions (fail hard)**
+   - Process exited 0 (or SIGINT-clean)
+   - stderr has `Model worker ready` and `Capturing from:`
+   - No `ERROR` lines in stderr (allow listed WARNINGs only if needed, e.g. always-on-top on Wayland)
+   - At least one non-empty caption log file under the smoke transcript dir **or**, if recognition is too flaky on synthetic speech, fall back to requiring `INFO [lifecycle]` start/stop without ERROR and treat caption text as a soft check printed in the report
+
+**Caption reliability default:** require caption log content. If espeak+VAD proves flaky in practice, switch the harness to `--mode=fixed --chunk-duration=1s` (still in the same script) before softening the assertion — fixed mode is more predictable with continuous playback.
+
+## Report
+
+Write `$workdir/report.txt` with: compositor, sink name, key log greps, transcript excerpt, pass/fail. Always print the report path on exit.
+
+## Docs / CI wiring
+
+- Short “Manual desktop smoke” subsection in [`README.md`](README.md) Development section
+- Add `scripts/smoke/desktop-smoke.sh` + `lib.sh` to ShellCheck in [`scripts/ci/test.sh`](scripts/ci/test.sh)
+- **Do not** add this to Gitea CI yet (needs models + nested compositor + audio; too heavy/flaky for every PR). Manual-only until it proves stable.
+
+## Out of scope
+
+- Full QEMU/libvirt guest image
+- Automating CTRL+drag overlay positioning
+- Pixel screenshot OCR of the overlay bubble

scripts/ci/package-release.sh

@@ -25,17 +25,19 @@ package_dir="dist/$package_name"
 rm -rf -- "$package_dir"
 rm -f -- "dist/$archive_name" "dist/$archive_name.sha256"
 mkdir -p -- \
+	"$package_dir/assets/icon" \
   "$package_dir/lib" \
   "$package_dir/scripts" \
   "$package_dir/third-party-licenses"
 
 # The Sherpa Go module embeds an absolute build-machine RPATH. Add a portable
 # build-time fallback; the final paths are normalized after dependency copying.
+# gtk4-layer-shell must precede libwayland-client so its Wayland shim installs.
 # shellcheck disable=SC2016 # $ORIGIN must remain literal for the ELF loader.
-CGO_LDFLAGS='-Wl,-rpath,$ORIGIN/lib' \
+CGO_LDFLAGS='-Wl,--no-as-needed -lgtk4-layer-shell -Wl,-rpath,$ORIGIN/lib' \
   go build -trimpath -o "$package_dir/captioneer" ./src/cmd/captioneer
 # shellcheck disable=SC2016 # $ORIGIN must remain literal for the ELF loader.
-CGO_LDFLAGS='-Wl,-rpath,$ORIGIN/lib' \
+CGO_LDFLAGS='-Wl,--no-as-needed -lgtk4-layer-shell -Wl,-rpath,$ORIGIN/lib' \
   go build -trimpath -tags gtk \
     -o "$package_dir/captioneer-desktop" ./src/cmd/captioneer-desktop
 
@@ -163,6 +165,7 @@ for executable in captioneer captioneer-desktop; do
 done
 
 cp -- README.md LICENSE "$package_dir/"
+cp -- assets/icon/icon.png "$package_dir/assets/icon/"
 cp -- scripts/download-models.sh "$package_dir/scripts/"
 
 for executable in captioneer captioneer-desktop; do

scripts/ci/test.sh

@@ -16,4 +16,6 @@ shellcheck \
   scripts/distrobox/run.sh \
   scripts/ci/test.sh \
   scripts/ci/package-release.sh \
-  scripts/ci/publish-release.sh
+  scripts/ci/publish-release.sh \
+  scripts/smoke/lib.sh \
+  scripts/smoke/desktop-smoke.sh

scripts/distrobox/build.sh

@@ -19,6 +19,9 @@ build_script='set -Eeuo pipefail
 repo_root=$1
 shift
 cd -- "$repo_root"
+# gtk4-layer-shell must precede libwayland-client in the loader order or the
+# Wayland shim never installs and the overlay cannot be positioned.
+export CGO_LDFLAGS="-Wl,--no-as-needed -lgtk4-layer-shell ${CGO_LDFLAGS:-}"
 go build "$@" -o build/captioneer ./src/cmd/captioneer
 go build "$@" -tags gtk -o build/captioneer-desktop ./src/cmd/captioneer-desktop'
 

scripts/distrobox/common.sh

@@ -14,6 +14,7 @@ container_packages=(
   curl
   gcc
   golang
+  gobject-introspection-devel
   gtk4-devel
   gtk4-layer-shell-devel
   libX11-devel

scripts/distrobox/run.sh

@@ -15,6 +15,18 @@ cd -- "$repo_root"
 # Avoid host/container DMABUF incompatibilities on mismatched GPU stacks. An
 # explicit GTK renderer choice still takes precedence.
 export GSK_RENDERER="${GSK_RENDERER:-cairo}"
+# gtk4-layer-shell must precede libwayland-client in the link line. Do NOT
+# LD_PRELOAD it here: the shim breaks the main GtkApplication window on
+# Wayland when forced onto the whole process.
+export CGO_LDFLAGS="-Wl,--no-as-needed -lgtk4-layer-shell ${CGO_LDFLAGS:-}"
+
+desktop_bin=build/captioneer-desktop
+if [[ -x "$desktop_bin" ]]; then
+  printf "captioneer: launching %s\\n" "$desktop_bin" >&2
+  exec "./$desktop_bin" "$@"
+fi
+
+printf "captioneer: no build/captioneer-desktop yet; compiling with go run (first launch is slow)\\n" >&2
 exec go run -tags gtk ./src/cmd/captioneer-desktop "$@"'
 
 exec distrobox enter --no-workdir --name "$container_name" -- \

scripts/smoke/desktop-smoke.sh

@@ -0,0 +1,190 @@
+#!/usr/bin/env bash
+# Manual desktop smoke test.
+#
+# Boots a headless Wayland compositor (sway) inside the captioneer-dev
+# Distrobox, routes synthesized speech through a temporary PipeWire null
+# sink, runs the real captioneer-desktop binary against it, and fails on
+# diagnostics errors or missing captions.
+#
+# Usage (from the repository root, on the host):
+#   ./scripts/download-models.sh        # once
+#   ./scripts/distrobox/build.sh        # produce build/captioneer-desktop
+#   ./scripts/smoke/desktop-smoke.sh
+#
+# Environment:
+#   CAPTIONEER_SMOKE_MODE      vad (default) or fixed
+#   CAPTIONEER_SMOKE_SPEECH_S  seconds of speech to play (default 20)
+set -Eeuo pipefail
+
+script_dir="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd -P)"
+repo_root="$(cd -- "$script_dir/../.." && pwd -P)"
+
+# ---------------------------------------------------------------------------
+# Host phase: prepare the Distrobox and re-execute this script inside it.
+# ---------------------------------------------------------------------------
+if [[ -z "${CAPTIONEER_SMOKE_INNER:-}" && -z "${CONTAINER_ID:-}" ]]; then
+  # shellcheck source=scripts/distrobox/common.sh
+  source "$repo_root/scripts/distrobox/common.sh"
+  prepare_distrobox
+
+  [[ -x "$repo_root/build/captioneer-desktop" ]] \
+    || die "build/captioneer-desktop is missing; run ./scripts/distrobox/build.sh first"
+  [[ -d "$repo_root/models/parakeet-tdt-v2" ]] \
+    || die "models/parakeet-tdt-v2 is missing; run ./scripts/download-models.sh first"
+  [[ -f "$repo_root/models/silero_vad_v5.onnx" ]] \
+    || die "models/silero_vad_v5.onnx is missing; run ./scripts/download-models.sh first"
+
+  # shellcheck disable=SC2016 # Positional parameters expand inside the container.
+  # shellcheck disable=SC2154 # container_name is defined by common.sh above.
+  exec distrobox enter --no-workdir --name "$container_name" -- \
+    bash -lc 'CAPTIONEER_SMOKE_INNER=1 exec bash "$1"' captioneer-smoke \
+    "$repo_root/scripts/smoke/desktop-smoke.sh"
+fi
+
+# ---------------------------------------------------------------------------
+# Inner phase: runs inside the Distrobox.
+# ---------------------------------------------------------------------------
+# shellcheck source=scripts/smoke/lib.sh
+source "$script_dir/lib.sh"
+
+smoke_mode="${CAPTIONEER_SMOKE_MODE:-vad}"
+speech_seconds="${CAPTIONEER_SMOKE_SPEECH_S:-20}"
+
+# On-demand smoke dependencies; kept out of common.sh so normal builds stay lean.
+smoke_packages=(sway espeak-ng)
+missing_packages=()
+for package in "${smoke_packages[@]}"; do
+  rpm -q "$package" >/dev/null 2>&1 || missing_packages+=("$package")
+done
+if (( ${#missing_packages[@]} > 0 )); then
+  smoke_log "installing smoke dependencies: ${missing_packages[*]}"
+  sudo dnf install -y "${missing_packages[@]}"
+fi
+
+cd -- "$repo_root"
+workdir="$repo_root/build/smoke/$(date +%Y%m%d-%H%M%S)"
+mkdir -p "$workdir/transcripts"
+smoke_log "work directory: $workdir"
+
+trap smoke_cleanup EXIT
+
+smoke_setup_audio "$workdir"
+wayland_socket="$(smoke_start_compositor "$workdir")"
+smoke_log "nested compositor ready on $wayland_socket"
+
+# ---------------------------------------------------------------------------
+# Launch the desktop application.
+# ---------------------------------------------------------------------------
+env \
+  WAYLAND_DISPLAY="$wayland_socket" \
+  GDK_BACKEND=wayland \
+  GSK_RENDERER=cairo \
+  ./build/captioneer-desktop \
+  --no-config \
+  --start-captions=true \
+  --output=both \
+  --stderr-diagnostics=true \
+  --caption-log=true \
+  --caption-log-dir="$workdir/transcripts" \
+  --models-dir=models \
+  --mode="$smoke_mode" \
+  --model-auto-restart=false \
+  > "$workdir/captioneer.stdout.log" \
+  2> "$workdir/captioneer.stderr.log" &
+SMOKE_APP_PID=$!
+smoke_log "captioneer-desktop started (pid $SMOKE_APP_PID, mode $smoke_mode)"
+
+stderr_log="$workdir/captioneer.stderr.log"
+
+if ! smoke_wait_for_line "$stderr_log" "Model worker ready" 60; then
+  smoke_fail "model worker did not become ready within 60s"
+fi
+if ! smoke_wait_for_line "$stderr_log" "Capturing from:" 30; then
+  smoke_fail "audio capture did not start within 30s"
+fi
+
+if (( ${#SMOKE_FAILURES[@]} == 0 )); then
+  smoke_log "playing synthesized speech for ${speech_seconds}s"
+  smoke_play_speech "$workdir" "$speech_seconds"
+  wait "$SMOKE_PLAYER_PID" 2>/dev/null || true
+  SMOKE_PLAYER_PID=""
+  # Allow VAD finalization (500ms pause) and transcript flush to settle.
+  sleep 4
+fi
+
+smoke_stop_app
+app_exit=0
+if smoke_wait_for_exit "$SMOKE_APP_PID" 20; then
+  wait "$SMOKE_APP_PID" 2>/dev/null || app_exit=$?
+else
+  smoke_fail "application did not exit within 20s of SIGINT"
+  kill -KILL "$SMOKE_APP_PID" 2>/dev/null || true
+  app_exit=137
+fi
+SMOKE_APP_PID=""
+
+# ---------------------------------------------------------------------------
+# Assertions.
+# ---------------------------------------------------------------------------
+if (( app_exit == 0 )); then
+  smoke_pass "clean shutdown (exit 0)"
+else
+  smoke_fail "application exited with status $app_exit"
+fi
+
+if grep -q "Model worker ready" "$stderr_log"; then
+  smoke_pass "model worker started"
+fi
+if grep -q "Capturing from:" "$stderr_log"; then
+  smoke_pass "audio capture attached to a monitor source"
+fi
+
+if grep -E " ERROR " "$stderr_log" > "$workdir/errors.txt"; then
+  smoke_fail "diagnostics contain ERROR lines (see errors.txt)"
+else
+  smoke_pass "no ERROR diagnostics"
+fi
+
+mapfile -t caption_files < <(find "$workdir/transcripts" -type f -size +0c 2>/dev/null)
+if (( ${#caption_files[@]} > 0 )); then
+  smoke_pass "caption log contains recognized speech"
+else
+  smoke_fail "no captions were recognized; inspect $workdir and consider CAPTIONEER_SMOKE_MODE=fixed"
+fi
+
+# ---------------------------------------------------------------------------
+# Report.
+# ---------------------------------------------------------------------------
+report="$workdir/report.txt"
+{
+  printf 'Captioneer desktop smoke report\n'
+  printf 'Date:        %s\n' "$(date --rfc-3339=seconds)"
+  printf 'Mode:        %s\n' "$smoke_mode"
+  printf 'Compositor:  sway headless (%s)\n' "$wayland_socket"
+  printf 'Sink:        %s\n' "$SMOKE_SINK_NAME"
+  printf 'App exit:    %s\n' "$app_exit"
+  printf '\n--- Key diagnostics ---\n'
+  grep -E " (ERROR|WARNING) |Model worker ready|Capturing from:|Shutting down" \
+    "$stderr_log" 2>/dev/null || printf '(none)\n'
+  printf '\n--- Caption transcript excerpt ---\n'
+  if (( ${#caption_files[@]} > 0 )); then
+    head -n 10 "${caption_files[@]}" 2>/dev/null
+  else
+    printf '(empty)\n'
+  fi
+  printf '\n--- Result ---\n'
+  if (( ${#SMOKE_FAILURES[@]} == 0 )); then
+    printf 'PASS\n'
+  else
+    printf 'FAIL:\n'
+    printf '  - %s\n' "${SMOKE_FAILURES[@]}"
+  fi
+} > "$report"
+
+cat "$report"
+smoke_log "full report: $report"
+
+if (( ${#SMOKE_FAILURES[@]} > 0 )); then
+  exit 1
+fi
+exit 0

scripts/smoke/lib.sh

@@ -0,0 +1,152 @@
+#!/usr/bin/env bash
+# Shared helpers for the manual desktop smoke test. Sourced by
+# scripts/smoke/desktop-smoke.sh inside the captioneer-dev Distrobox.
+set -Eeuo pipefail
+
+SMOKE_SINK_NAME="captioneer-smoke"
+SMOKE_SINK_MODULE=""
+SMOKE_PREVIOUS_SINK=""
+SMOKE_COMPOSITOR_PID=""
+SMOKE_APP_PID=""
+SMOKE_PLAYER_PID=""
+SMOKE_FAILURES=()
+
+smoke_log() {
+  printf 'smoke: %s\n' "$*" >&2
+}
+
+smoke_die() {
+  printf 'smoke: FATAL: %s\n' "$*" >&2
+  exit 1
+}
+
+smoke_fail() {
+  SMOKE_FAILURES+=("$1")
+  smoke_log "FAIL: $1"
+}
+
+smoke_pass() {
+  smoke_log "ok: $1"
+}
+
+# smoke_wait_for_line FILE PATTERN TIMEOUT_SECONDS
+smoke_wait_for_line() {
+  local file=$1 pattern=$2 timeout=$3 waited=0
+  until grep -q -- "$pattern" "$file" 2>/dev/null; do
+    if (( waited >= timeout )); then
+      return 1
+    fi
+    sleep 1
+    waited=$((waited + 1))
+  done
+  return 0
+}
+
+# smoke_wait_for_exit PID TIMEOUT_SECONDS; returns 1 on timeout
+smoke_wait_for_exit() {
+  local pid=$1 timeout=$2 waited=0
+  while kill -0 "$pid" 2>/dev/null; do
+    if (( waited >= timeout )); then
+      return 1
+    fi
+    sleep 1
+    waited=$((waited + 1))
+  done
+  return 0
+}
+
+smoke_setup_audio() {
+  local workdir=$1
+  command -v pactl >/dev/null 2>&1 || smoke_die "pactl is required"
+  command -v paplay >/dev/null 2>&1 || smoke_die "paplay is required"
+  SMOKE_PREVIOUS_SINK="$(pactl get-default-sink 2>/dev/null || true)"
+  SMOKE_SINK_MODULE="$(pactl load-module module-null-sink \
+    "sink_name=$SMOKE_SINK_NAME" \
+    "sink_properties=device.description=Captioneer-Smoke")"
+  pactl set-default-sink "$SMOKE_SINK_NAME"
+  smoke_log "null sink $SMOKE_SINK_NAME loaded (module $SMOKE_SINK_MODULE, previous default: ${SMOKE_PREVIOUS_SINK:-none})"
+
+  command -v espeak-ng >/dev/null 2>&1 || smoke_die "espeak-ng is required"
+  espeak-ng -v en-us -s 140 -w "$workdir/speech.wav" \
+    "The quick brown fox jumps over the lazy dog. Live captions should appear for this sentence."
+  [[ -s "$workdir/speech.wav" ]] || smoke_die "espeak-ng produced no audio fixture"
+}
+
+smoke_teardown_audio() {
+  if [[ -n "$SMOKE_PLAYER_PID" ]] && kill -0 "$SMOKE_PLAYER_PID" 2>/dev/null; then
+    kill "$SMOKE_PLAYER_PID" 2>/dev/null || true
+  fi
+  if [[ -n "$SMOKE_PREVIOUS_SINK" ]]; then
+    pactl set-default-sink "$SMOKE_PREVIOUS_SINK" 2>/dev/null || true
+  fi
+  if [[ -n "$SMOKE_SINK_MODULE" ]]; then
+    pactl unload-module "$SMOKE_SINK_MODULE" 2>/dev/null || true
+    SMOKE_SINK_MODULE=""
+  fi
+}
+
+# smoke_play_speech WORKDIR SECONDS: loop the fixture into the null sink.
+smoke_play_speech() {
+  local workdir=$1 seconds=$2
+  (
+    end=$((SECONDS + seconds))
+    while (( SECONDS < end )); do
+      paplay --device="$SMOKE_SINK_NAME" "$workdir/speech.wav" 2>/dev/null || sleep 1
+    done
+  ) &
+  SMOKE_PLAYER_PID=$!
+}
+
+# smoke_start_compositor WORKDIR: starts headless sway; prints new socket name.
+# sway is wlroots-based (Layer Shell capable) and, unlike labwc, can disable
+# Xwayland, whose sockets are not creatable inside a rootless Distrobox.
+smoke_start_compositor() {
+  local workdir=$1 candidate socket="" waited=0
+  command -v sway >/dev/null 2>&1 || smoke_die "sway is required"
+  local before="$workdir/sockets-before.txt"
+  find "$XDG_RUNTIME_DIR" -maxdepth 1 -name 'wayland-[0-9]*' ! -name '*.lock' \
+    -printf '%f\n' 2>/dev/null | sort > "$before"
+
+  printf 'xwayland disable\n' > "$workdir/sway-config"
+  WLR_BACKENDS=headless \
+    WLR_LIBINPUT_NO_DEVICES=1 \
+    WLR_RENDERER=pixman \
+    sway -c "$workdir/sway-config" > "$workdir/compositor.log" 2>&1 &
+  SMOKE_COMPOSITOR_PID=$!
+
+  while (( waited < 15 )); do
+    while IFS= read -r candidate; do
+      socket="$candidate"
+    done < <(find "$XDG_RUNTIME_DIR" -maxdepth 1 -name 'wayland-[0-9]*' ! -name '*.lock' \
+      -printf '%f\n' 2>/dev/null | sort | comm -13 "$before" -)
+    if [[ -n "$socket" ]]; then
+      printf '%s\n' "$socket"
+      return 0
+    fi
+    kill -0 "$SMOKE_COMPOSITOR_PID" 2>/dev/null || smoke_die "sway exited early; see $workdir/compositor.log"
+    sleep 1
+    waited=$((waited + 1))
+  done
+  smoke_die "sway did not create a Wayland socket; see $workdir/compositor.log"
+}
+
+smoke_teardown_compositor() {
+  if [[ -n "$SMOKE_COMPOSITOR_PID" ]] && kill -0 "$SMOKE_COMPOSITOR_PID" 2>/dev/null; then
+    kill "$SMOKE_COMPOSITOR_PID" 2>/dev/null || true
+  fi
+}
+
+smoke_stop_app() {
+  if [[ -n "$SMOKE_APP_PID" ]] && kill -0 "$SMOKE_APP_PID" 2>/dev/null; then
+    kill -INT "$SMOKE_APP_PID" 2>/dev/null || true
+  fi
+}
+
+smoke_cleanup() {
+  smoke_stop_app
+  if [[ -n "$SMOKE_APP_PID" ]]; then
+    smoke_wait_for_exit "$SMOKE_APP_PID" 10 || kill -KILL "$SMOKE_APP_PID" 2>/dev/null || true
+  fi
+  smoke_teardown_audio
+  smoke_teardown_compositor
+}

src/app/controller.go

@@ -0,0 +1,215 @@
+package app
+
+import (
+	"context"
+	"errors"
+	"io"
+	"sync"
+	"time"
+
+	"tea.chunkbyte.com/kato/captioneer/src/config"
+	"tea.chunkbyte.com/kato/captioneer/src/output"
+)
+
+type State string
+
+const (
+	StateStopped    State = "stopped"
+	StateStarting   State = "starting"
+	StateListening  State = "listening"
+	StateProcessing State = "processing"
+	StateRestarting State = "restarting"
+	StateStopping   State = "stopping"
+	StateError      State = "error"
+)
+
+type Status struct {
+	State        State
+	Mode         config.Mode
+	Source       string
+	SpeechActive bool
+	OverloadedAt time.Time
+	LastError    string
+	UpdatedAt    time.Time
+}
+
+type sessionRunner func(context.Context, config.Settings, output.Sink, io.Writer, RuntimeObserver) error
+
+type Controller struct {
+	mu          sync.Mutex
+	runner      sessionRunner
+	sink        output.Sink
+	diagnostics io.Writer
+	cancel      context.CancelFunc
+	done        chan error
+	status      Status
+	subscribers map[chan Status]struct{}
+}
+
+func NewController(sink output.Sink, diagnostics io.Writer) *Controller {
+	return newControllerWithRunner(sink, diagnostics, RunObserved)
+}
+
+func newControllerWithRunner(sink output.Sink, diagnostics io.Writer, runner sessionRunner) *Controller {
+	return &Controller{
+		runner:      runner,
+		sink:        sink,
+		diagnostics: diagnostics,
+		status:      Status{State: StateStopped, UpdatedAt: time.Now()},
+		subscribers: make(map[chan Status]struct{}),
+	}
+}
+
+func (c *Controller) Start(settings config.Settings) error {
+	if err := settings.Validate(); err != nil {
+		return err
+	}
+	c.mu.Lock()
+	if c.cancel != nil {
+		c.mu.Unlock()
+		return errors.New("caption processing is already running")
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	done := make(chan error, 1)
+	c.cancel = cancel
+	c.done = done
+	c.status = Status{State: StateStarting, Mode: settings.Mode, UpdatedAt: time.Now()}
+	c.publishLocked()
+	c.mu.Unlock()
+
+	go func() {
+		err := c.runner(ctx, settings, c.sink, c.diagnostics, c.observe)
+		c.mu.Lock()
+		if c.done == done {
+			c.cancel = nil
+			c.done = nil
+			if err != nil {
+				c.status.State = StateError
+				c.status.LastError = err.Error()
+			} else {
+				c.status.State = StateStopped
+				c.status.SpeechActive = false
+			}
+			c.status.UpdatedAt = time.Now()
+			c.publishLocked()
+		}
+		c.mu.Unlock()
+		done <- err
+		close(done)
+	}()
+	return nil
+}
+
+func (c *Controller) Stop(ctx context.Context) error {
+	c.mu.Lock()
+	if c.cancel == nil {
+		c.mu.Unlock()
+		return nil
+	}
+	if c.status.State != StateRestarting {
+		c.status.State = StateStopping
+	}
+	c.status.UpdatedAt = time.Now()
+	c.publishLocked()
+	cancel := c.cancel
+	done := c.done
+	c.mu.Unlock()
+	cancel()
+	select {
+	case err := <-done:
+		return err
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+}
+
+func (c *Controller) Restart(ctx context.Context, settings config.Settings) error {
+	c.mu.Lock()
+	if c.cancel != nil {
+		c.status.State = StateRestarting
+		c.status.UpdatedAt = time.Now()
+		c.publishLocked()
+	}
+	c.mu.Unlock()
+	if err := c.Stop(ctx); err != nil {
+		return err
+	}
+	return c.Start(settings)
+}
+
+func (c *Controller) Status() Status {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.status
+}
+
+func (c *Controller) Subscribe(buffer int) (<-chan Status, func()) {
+	if buffer < 1 {
+		buffer = 1
+	}
+	updates := make(chan Status, buffer)
+	c.mu.Lock()
+	c.subscribers[updates] = struct{}{}
+	updates <- c.status
+	c.mu.Unlock()
+	return updates, func() {
+		c.mu.Lock()
+		if _, ok := c.subscribers[updates]; ok {
+			delete(c.subscribers, updates)
+			close(updates)
+		}
+		c.mu.Unlock()
+	}
+}
+
+func (c *Controller) observe(event RuntimeEvent) {
+	c.mu.Lock()
+	switch event.Kind {
+	case RuntimeStarting:
+		c.status.State = StateStarting
+		c.status.LastError = ""
+	case RuntimeListening:
+		c.status.State = StateListening
+		c.status.LastError = ""
+	case RuntimeProcessing:
+		c.status.State = StateProcessing
+	case RuntimeRestarting:
+		c.status.State = StateRestarting
+	case RuntimeStopped:
+		c.status.State = StateStopped
+		c.status.SpeechActive = false
+	case RuntimeError:
+		if event.Err != nil {
+			c.status.LastError = event.Err.Error()
+		}
+	case RuntimeSource:
+		c.status.Source = event.Value
+	case RuntimeSpeech:
+		c.status.SpeechActive = event.Active
+	case RuntimeOverloaded:
+		c.status.OverloadedAt = event.At
+	}
+	c.status.UpdatedAt = event.At
+	if c.status.UpdatedAt.IsZero() {
+		c.status.UpdatedAt = time.Now()
+	}
+	c.publishLocked()
+	c.mu.Unlock()
+}
+
+func (c *Controller) publishLocked() {
+	for subscriber := range c.subscribers {
+		select {
+		case subscriber <- c.status:
+		default:
+			select {
+			case <-subscriber:
+			default:
+			}
+			select {
+			case subscriber <- c.status:
+			default:
+			}
+		}
+	}
+}

src/app/controller_test.go

@@ -0,0 +1,81 @@
+package app
+
+import (
+	"context"
+	"io"
+	"sync"
+	"testing"
+	"time"
+
+	"tea.chunkbyte.com/kato/captioneer/src/config"
+	"tea.chunkbyte.com/kato/captioneer/src/output"
+)
+
+func TestControllerStartObserveAndStop(t *testing.T) {
+	started := make(chan struct{})
+	runner := func(ctx context.Context, settings config.Settings, sink output.Sink, diagnostics io.Writer, observer RuntimeObserver) error {
+		observe(observer, RuntimeEvent{Kind: RuntimeSource, Value: "monitor-source"})
+		observe(observer, RuntimeEvent{Kind: RuntimeListening})
+		observe(observer, RuntimeEvent{Kind: RuntimeSpeech, Active: true})
+		close(started)
+		<-ctx.Done()
+		observe(observer, RuntimeEvent{Kind: RuntimeStopped})
+		return nil
+	}
+	controller := newControllerWithRunner(nil, io.Discard, runner)
+	settings := config.DefaultSettings()
+	if err := controller.Start(settings); err != nil {
+		t.Fatalf("Start() error = %v", err)
+	}
+	select {
+	case <-started:
+	case <-time.After(time.Second):
+		t.Fatal("runner did not start")
+	}
+	status := controller.Status()
+	if status.State != StateListening || status.Source != "monitor-source" || !status.SpeechActive {
+		t.Fatalf("Status() = %#v", status)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+	if err := controller.Stop(ctx); err != nil {
+		t.Fatalf("Stop() error = %v", err)
+	}
+	status = controller.Status()
+	if status.State != StateStopped || status.SpeechActive {
+		t.Fatalf("Status() after stop = %#v", status)
+	}
+}
+
+func TestControllerRestartUsesNewSettings(t *testing.T) {
+	var mu sync.Mutex
+	var modes []config.Mode
+	started := make(chan struct{}, 2)
+	runner := func(ctx context.Context, settings config.Settings, sink output.Sink, diagnostics io.Writer, observer RuntimeObserver) error {
+		mu.Lock()
+		modes = append(modes, settings.Mode)
+		mu.Unlock()
+		observe(observer, RuntimeEvent{Kind: RuntimeListening})
+		started <- struct{}{}
+		<-ctx.Done()
+		return nil
+	}
+	controller := newControllerWithRunner(nil, io.Discard, runner)
+	settings := config.DefaultSettings()
+	if err := controller.Start(settings); err != nil {
+		t.Fatal(err)
+	}
+	<-started
+	settings.Mode = config.ModeFixed
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+	if err := controller.Restart(ctx, settings); err != nil {
+		t.Fatalf("Restart() error = %v", err)
+	}
+	<-started
+	mu.Lock()
+	defer mu.Unlock()
+	if len(modes) != 2 || modes[0] != config.ModeVAD || modes[1] != config.ModeFixed {
+		t.Fatalf("runner modes = %v", modes)
+	}
+}

src/app/run.go

@@ -15,9 +15,13 @@ import (
 )
 
 type directHooks struct {
-	ready func() error
+	ready       func() error
-	busy  func() error
+	busy        func() error
-	idle  func() error
+	idle        func() error
+	source      func(string) error
+	speech      func(bool) error
+	recognition func(bool) error
+	overloaded  func() error
 }
 
 func runDirect(ctx context.Context, settings config.Settings, sink output.Sink, diagnostics io.Writer, hooks directHooks) error {
@@ -45,8 +49,17 @@ func runDirect(ctx context.Context, settings config.Settings, sink output.Sink,
 		return fmt.Errorf("find default output monitor: %w", err)
 	}
 	fmt.Fprintf(diagnostics, "Capturing from: %s\n", monitorSource)
+	if hooks.source != nil {
+		if err := hooks.source(monitorSource); err != nil {
+			return err
+		}
+	}
 
-	packets, waitCapture, err := capture.Packets(ctx, monitorSource)
+	packets, waitCapture, err := capture.PacketsObserved(ctx, monitorSource, diagnostics, func() {
+		if hooks.overloaded != nil {
+			_ = hooks.overloaded()
+		}
+	})
 	if err != nil {
 		return fmt.Errorf("start system-audio capture: %w", err)
 	}
@@ -56,7 +69,18 @@ func runDirect(ctx context.Context, settings config.Settings, sink output.Sink,
 		return err
 	}
 
-	processor := captions.New(settings, resources, sink.Publish)
+	processor := captions.NewWithActivity(settings, resources, sink.Publish, captions.Activity{
+		SpeechChanged: func(active bool) {
+			if hooks.speech != nil {
+				_ = hooks.speech(active)
+			}
+		},
+		RecognitionChanged: func(active bool) {
+			if hooks.recognition != nil {
+				_ = hooks.recognition(active)
+			}
+		},
+	})
 	var processErr error
 	for packet := range packets {
 		if err := hooks.busy(); err != nil {

src/app/status.go

@@ -0,0 +1,37 @@
+package app
+
+import "time"
+
+type RuntimeEventKind string
+
+const (
+	RuntimeStarting   RuntimeEventKind = "starting"
+	RuntimeListening  RuntimeEventKind = "listening"
+	RuntimeProcessing RuntimeEventKind = "processing"
+	RuntimeRestarting RuntimeEventKind = "restarting"
+	RuntimeStopped    RuntimeEventKind = "stopped"
+	RuntimeError      RuntimeEventKind = "error"
+	RuntimeSource     RuntimeEventKind = "source"
+	RuntimeSpeech     RuntimeEventKind = "speech"
+	RuntimeOverloaded RuntimeEventKind = "overloaded"
+)
+
+type RuntimeEvent struct {
+	Kind   RuntimeEventKind
+	At     time.Time
+	Value  string
+	Active bool
+	Err    error
+}
+
+type RuntimeObserver func(RuntimeEvent)
+
+func observe(observer RuntimeObserver, event RuntimeEvent) {
+	if observer == nil {
+		return
+	}
+	if event.At.IsZero() {
+		event.At = time.Now()
+	}
+	observer(event)
+}

src/app/supervisor.go

@@ -72,10 +72,22 @@ func (h workerHealth) timeoutError(now time.Time, timeout time.Duration) error {
 // Presentation stays in this process, so the native model can be replaced
 // without restarting the terminal or GTK main loop.
 func Run(ctx context.Context, settings config.Settings, sink output.Sink, diagnostics io.Writer) error {
+	return RunObserved(ctx, settings, sink, diagnostics, nil)
+}
+
+func RunObserved(
+	ctx context.Context,
+	settings config.Settings,
+	sink output.Sink,
+	diagnostics io.Writer,
+	observer RuntimeObserver,
+) error {
 	if err := capture.ValidatePrograms(); err != nil {
+		observe(observer, RuntimeEvent{Kind: RuntimeError, Err: err})
 		return err
 	}
 	if err := models.Validate(settings); err != nil {
+		observe(observer, RuntimeEvent{Kind: RuntimeError, Err: err})
 		return err
 	}
 
@@ -84,24 +96,32 @@ func Run(ctx context.Context, settings config.Settings, sink output.Sink, diagno
 	signal.Notify(reload, syscall.SIGHUP)
 	defer signal.Stop(reload)
 
+	observe(observer, RuntimeEvent{Kind: RuntimeStarting})
 	for {
-		result, err := runWorkerAttempt(ctx, settings, sink, diagnostics, reload)
+		result, err := runWorkerAttempt(ctx, settings, sink, diagnostics, reload, observer)
 		if ctx.Err() != nil {
+			observe(observer, RuntimeEvent{Kind: RuntimeStopped})
 			return nil
 		}
 		switch result {
 		case attemptStopped:
+			observe(observer, RuntimeEvent{Kind: RuntimeStopped})
 			return nil
 		case attemptFatal:
+			observe(observer, RuntimeEvent{Kind: RuntimeError, Err: err})
 			return err
 		case attemptReload:
 			fmt.Fprintln(diagnostics, "Reloading model worker.")
+			observe(observer, RuntimeEvent{Kind: RuntimeRestarting})
 			continue
 		case attemptFailed:
 			if !settings.ModelAutoRestart {
+				observe(observer, RuntimeEvent{Kind: RuntimeError, Err: err})
 				return err
 			}
 			fmt.Fprintf(diagnostics, "warning: %v; restarting model worker in %s\n", err, modelRestartDelay)
+			observe(observer, RuntimeEvent{Kind: RuntimeError, Err: err})
+			observe(observer, RuntimeEvent{Kind: RuntimeRestarting})
 		}
 
 		timer := time.NewTimer(modelRestartDelay)
@@ -116,6 +136,7 @@ func Run(ctx context.Context, settings config.Settings, sink output.Sink, diagno
 				<-timer.C
 			}
 			fmt.Fprintln(diagnostics, "Reloading model worker.")
+			observe(observer, RuntimeEvent{Kind: RuntimeRestarting})
 		case <-timer.C:
 		}
 	}
@@ -127,6 +148,7 @@ func runWorkerAttempt(
 	sink output.Sink,
 	diagnostics io.Writer,
 	reload <-chan os.Signal,
+	observer RuntimeObserver,
 ) (attemptResult, error) {
 	cmd, protocol, err := startModelWorker(settings, diagnostics)
 	if err != nil {
@@ -236,8 +258,21 @@ func runWorkerAttempt(
 			switch message.Type {
 			case messageReady:
 				fmt.Fprintln(diagnostics, "Model worker ready.")
+				observe(observer, RuntimeEvent{Kind: RuntimeListening})
 			case messageBusy, messageIdle:
 			case messageHeartbeat:
+			case messageSource:
+				observe(observer, RuntimeEvent{Kind: RuntimeSource, Value: message.Value})
+			case messageSpeech:
+				observe(observer, RuntimeEvent{Kind: RuntimeSpeech, Active: message.Active})
+			case messageRecognition:
+				kind := RuntimeListening
+				if message.Active {
+					kind = RuntimeProcessing
+				}
+				observe(observer, RuntimeEvent{Kind: kind, Active: message.Active})
+			case messageOverloaded:
+				observe(observer, RuntimeEvent{Kind: RuntimeOverloaded})
 			case messageCaption:
 				if message.Event == nil {
 					beginStop(attemptFailed, errors.New("model worker sent an empty caption event"))

src/app/worker_protocol.go

@@ -24,18 +24,24 @@ const (
 )
 
 const (
-	messageReady     = "ready"
+	messageReady       = "ready"
-	messageBusy      = "busy"
+	messageBusy        = "busy"
-	messageIdle      = "idle"
+	messageIdle        = "idle"
-	messageCaption   = "caption"
+	messageCaption     = "caption"
-	messageFailure   = "failure"
+	messageFailure     = "failure"
-	messageHeartbeat = "heartbeat"
+	messageHeartbeat   = "heartbeat"
+	messageSource      = "source"
+	messageSpeech      = "speech"
+	messageRecognition = "recognition"
+	messageOverloaded  = "overloaded"
 )
 
 type workerMessage struct {
-	Type  string          `json:"type"`
+	Type   string          `json:"type"`
-	Event *captions.Event `json:"event,omitempty"`
+	Event  *captions.Event `json:"event,omitempty"`
-	Error string          `json:"error,omitempty"`
+	Error  string          `json:"error,omitempty"`
+	Value  string          `json:"value,omitempty"`
+	Active bool            `json:"active,omitempty"`
 }
 
 type workerReporter struct {
@@ -110,9 +116,13 @@ func RunModelWorker(diagnostics io.Writer) int {
 
 	reporter := &workerReporter{encoder: json.NewEncoder(protocol)}
 	hooks := directHooks{
-		ready: func() error { return reporter.send(workerMessage{Type: messageReady}) },
+		ready:       func() error { return reporter.send(workerMessage{Type: messageReady}) },
-		busy:  func() error { return reporter.send(workerMessage{Type: messageBusy}) },
+		busy:        func() error { return reporter.send(workerMessage{Type: messageBusy}) },
-		idle:  func() error { return reporter.send(workerMessage{Type: messageIdle}) },
+		idle:        func() error { return reporter.send(workerMessage{Type: messageIdle}) },
+		source:      func(value string) error { return reporter.send(workerMessage{Type: messageSource, Value: value}) },
+		speech:      func(active bool) error { return reporter.send(workerMessage{Type: messageSpeech, Active: active}) },
+		recognition: func(active bool) error { return reporter.send(workerMessage{Type: messageRecognition, Active: active}) },
+		overloaded:  func() error { return reporter.send(workerMessage{Type: messageOverloaded}) },
 	}
 
 	heartbeatInterval := time.Second

src/captions/processor.go

@@ -27,14 +27,27 @@ type Processor struct {
 	nextPreviewAt   int
 	previewReceived int
 	totalSamples    int
+	activity        Activity
+	speechKnown     bool
+	speechActive    bool
+}
+
+type Activity struct {
+	SpeechChanged      func(bool)
+	RecognitionChanged func(bool)
 }
 
 func New(settings config.Settings, transcriber Transcriber, emit func(Event) error) *Processor {
+	return NewWithActivity(settings, transcriber, emit, Activity{})
+}
+
+func NewWithActivity(settings config.Settings, transcriber Transcriber, emit func(Event) error, activity Activity) *Processor {
 	return &Processor{
 		settings:      settings,
 		transcriber:   transcriber,
 		emit:          emit,
 		nextPreviewAt: audio.DurationSamples(settings.ChunkDuration),
+		activity:      activity,
 	}
 }
 
@@ -43,6 +56,7 @@ func (p *Processor) Accept(samples []float32) error {
 		return nil
 	}
 	if p.settings.Mode == config.ModeFixed {
+		p.setSpeechActive(audio.RMSDBFS(samples) >= p.settings.PreviewThresholdDB)
 		return p.acceptFixed(samples)
 	}
 	return p.acceptVAD(samples)
@@ -84,6 +98,7 @@ func (p *Processor) acceptVAD(samples []float32) error {
 	p.transcriber.AcceptVAD(samples)
 
 	speechActive := p.transcriber.SpeechActive()
+	p.setSpeechActive(speechActive)
 	if speechActive && (p.previewActive || audio.RMSDBFS(samples) >= p.settings.PreviewThresholdDB) {
 		if !p.previewActive {
 			p.previewActive = true
@@ -144,7 +159,7 @@ func (p *Processor) resetPreview() {
 }
 
 func (p *Processor) emitProvisional() error {
-	text := strings.TrimSpace(p.transcriber.Decode(p.previewSamples))
+	text := strings.TrimSpace(p.decode(p.previewSamples))
 	if text == "" {
 		return nil
 	}
@@ -157,7 +172,7 @@ func (p *Processor) emitProvisional() error {
 }
 
 func (p *Processor) emitFinal(start, end int, samples []float32) error {
-	text := strings.TrimSpace(p.transcriber.Decode(samples))
+	text := strings.TrimSpace(p.decode(samples))
 	if text == "" {
 		return p.emit(Event{Kind: Hide})
 	}
@@ -169,6 +184,25 @@ func (p *Processor) emitFinal(start, end int, samples []float32) error {
 	})
 }
 
+func (p *Processor) decode(samples []float32) string {
+	if p.activity.RecognitionChanged != nil {
+		p.activity.RecognitionChanged(true)
+		defer p.activity.RecognitionChanged(false)
+	}
+	return p.transcriber.Decode(samples)
+}
+
+func (p *Processor) setSpeechActive(active bool) {
+	if p.speechKnown && p.speechActive == active {
+		return
+	}
+	p.speechKnown = true
+	p.speechActive = active
+	if p.activity.SpeechChanged != nil {
+		p.activity.SpeechChanged(active)
+	}
+}
+
 func (p *Processor) emitFixedFinal(start, end int, samples []float32) error {
 	if audio.RMSDBFS(samples) < p.settings.PreviewThresholdDB {
 		return p.emit(Event{Kind: Hide})

src/capture/pulse.go

@@ -33,6 +33,15 @@ func DefaultMonitorSource(ctx context.Context) (string, error) {
 }
 
 func Packets(ctx context.Context, monitorSource string) (<-chan []float32, func() error, error) {
+	return PacketsObserved(ctx, monitorSource, os.Stderr, nil)
+}
+
+func PacketsObserved(
+	ctx context.Context,
+	monitorSource string,
+	diagnostics io.Writer,
+	overloaded func(),
+) (<-chan []float32, func() error, error) {
 	cmd := exec.CommandContext(ctx, "parec",
 		"--device="+monitorSource,
 		"--format=s16le",
@@ -41,7 +50,7 @@ func Packets(ctx context.Context, monitorSource string) (<-chan []float32, func(
 		"--raw",
 		"--latency-msec=50",
 	)
-	cmd.Stderr = os.Stderr
+	cmd.Stderr = diagnostics
 	cmd.SysProcAttr = &syscall.SysProcAttr{Pdeathsig: syscall.SIGKILL}
 	stdout, err := cmd.StdoutPipe()
 	if err != nil {
@@ -65,11 +74,11 @@ func Packets(ctx context.Context, monitorSource string) (<-chan []float32, func(
 		for {
 			n, readErr := io.ReadFull(stdout, packetBytes)
 			if n > 0 {
-				enqueueLatest(packets, audio.PCM16LEToFloat32(packetBytes[:n]))
+				enqueueLatest(packets, audio.PCM16LEToFloat32(packetBytes[:n]), diagnostics, overloaded)
 			}
 			if readErr != nil {
 				if ctx.Err() == nil && !errors.Is(readErr, io.EOF) && !errors.Is(readErr, io.ErrUnexpectedEOF) {
-					fmt.Fprintf(os.Stderr, "audio capture read error: %v\n", readErr)
+					fmt.Fprintf(diagnostics, "audio capture read error: %v\n", readErr)
 				}
 				return
 			}
@@ -78,7 +87,7 @@ func Packets(ctx context.Context, monitorSource string) (<-chan []float32, func(
 	return packets, wait, nil
 }
 
-func enqueueLatest(packets chan []float32, packet []float32) {
+func enqueueLatest(packets chan []float32, packet []float32, diagnostics io.Writer, overloaded func()) {
 	select {
 	case packets <- packet:
 		return
@@ -93,5 +102,8 @@ func enqueueLatest(packets chan []float32, packet []float32) {
 	case packets <- packet:
 	default:
 	}
-	fmt.Fprintln(os.Stderr, "warning: caption processing overloaded; dropped 100 ms of oldest audio")
+	fmt.Fprintln(diagnostics, "warning: caption processing overloaded; dropped 100 ms of oldest audio")
+	if overloaded != nil {
+		overloaded()
+	}
 }

src/cmd/captioneer-desktop/layershell_link.go

@@ -0,0 +1,21 @@
+//go:build gtk
+
+package main
+
+/*
+#cgo pkg-config: gtk4-layer-shell-0
+#cgo LDFLAGS: -Wl,--no-as-needed -lgtk4-layer-shell
+
+// gtk4-layer-shell shims libwayland-client. It must appear before
+// libwayland-client in the dynamic loader order or gtk_layer_is_supported()
+// returns false and the overlay becomes an unpositioned normal window.
+// Referencing the symbol from the main package keeps the dependency alive
+// even when the external linker would otherwise drop or reorder it.
+#include <gtk4-layer-shell.h>
+
+static void captioneer_keep_layershell_linked(void) __attribute__((used));
+static void captioneer_keep_layershell_linked(void) {
+	(void)gtk_layer_get_major_version;
+}
+*/
+import "C"

src/cmd/captioneer-desktop/main.go

@@ -3,20 +3,15 @@
 package main
 
 import (
-	"context"
 	"errors"
+	"flag"
 	"fmt"
-	"log"
 	"os"
-	"os/signal"
 	"runtime"
-	"syscall"
 
 	"tea.chunkbyte.com/kato/captioneer/src/app"
 	"tea.chunkbyte.com/kato/captioneer/src/config"
-	"tea.chunkbyte.com/kato/captioneer/src/output"
+	"tea.chunkbyte.com/kato/captioneer/src/gui"
-	"tea.chunkbyte.com/kato/captioneer/src/output/overlay"
-	"tea.chunkbyte.com/kato/captioneer/src/output/terminal"
 )
 
 func main() {
@@ -24,58 +19,15 @@ func main() {
 		os.Exit(app.RunModelWorker(os.Stderr))
 	}
 
-	runtime.LockOSThread()
+	launch, err := config.ParseDesktop(os.Args[1:], os.Stderr)
-	defer runtime.UnlockOSThread()
+	if errors.Is(err, flag.ErrHelp) {
-
-	settings := config.ParseDesktop()
-	if err := settings.Validate(); err != nil {
-		log.Fatal(err)
-	}
-
-	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
-	defer stop()
-
-	terminalSink := terminal.New(os.Stdout)
-	if settings.Output == config.OutputTerminal {
-		defer terminalSink.Close()
-		if err := app.Run(ctx, settings.Settings, terminalSink, os.Stderr); err != nil {
-			log.Fatal(err)
-		}
 		return
 	}
-
+	if err != nil {
-	overlaySink, warning, overlayErr := overlay.New(settings.Overlay)
+		fmt.Fprintln(os.Stderr, err)
-	if warning != "" {
+		os.Exit(2)
-		fmt.Fprintf(os.Stderr, "warning: %s\n", warning)
-	}
-	if overlayErr != nil {
-		if settings.Output == config.OutputBoth {
-			fmt.Fprintf(os.Stderr, "warning: overlay unavailable: %v; continuing with terminal output\n", overlayErr)
-			defer terminalSink.Close()
-			if err := app.Run(ctx, settings.Settings, terminalSink, os.Stderr); err != nil {
-				log.Fatal(err)
-			}
-			return
-		}
-		log.Fatalf("initialize overlay: %v", overlayErr)
 	}
 
-	var sink output.Sink = overlaySink
+	runtime.LockOSThread()
-	if settings.Output == config.OutputBoth {
+	os.Exit(gui.Run(launch, os.Stdout, os.Stderr))
-		sink = output.MultiSink{terminalSink, overlaySink}
-	}
-
-	workerDone := make(chan error, 1)
-	go func() {
-		workerDone <- app.Run(ctx, settings.Settings, sink, os.Stderr)
-		overlaySink.Quit()
-	}()
-
-	runErr := overlaySink.Run()
-	stop()
-	workerErr := <-workerDone
-	closeErr := sink.Close()
-	if err := errors.Join(runErr, workerErr, closeErr); err != nil {
-		log.Fatal(err)
-	}
 }

src/cmd/captioneer/main.go

@@ -2,6 +2,9 @@ package main
 
 import (
 	"context"
+	"errors"
+	"flag"
+	"fmt"
 	"log"
 	"os"
 	"os/signal"
@@ -17,10 +20,17 @@ func main() {
 		os.Exit(app.RunModelWorker(os.Stderr))
 	}
 
-	settings := config.Parse()
+	launch, err := config.Parse(os.Args[1:], os.Stderr)
-	if err := settings.Validate(); err != nil {
+	if errors.Is(err, flag.ErrHelp) {
+		return
+	}
+	if err != nil {
 		log.Fatal(err)
 	}
+	if launch.Warning != nil {
+		fmt.Fprintf(os.Stderr, "warning: %v; using built-in defaults\n", launch.Warning)
+	}
+	settings := launch.Config.Settings
 
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()

src/config/cli.go

@@ -0,0 +1,192 @@
+package config
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"strings"
+)
+
+type LaunchConfig struct {
+	Config  AppConfig
+	Path    string
+	Warning error
+}
+
+func Parse(args []string, help io.Writer) (LaunchConfig, error) {
+	launch, err := loadLaunchConfig(args)
+	if err != nil {
+		return LaunchConfig{}, err
+	}
+	flags := flag.NewFlagSet("captioneer", flag.ContinueOnError)
+	flags.SetOutput(help)
+	registerConfigFlags(flags, &launch, args)
+	registerRecognitionFlags(flags, &launch.Config.Settings)
+	if err := flags.Parse(args); err != nil {
+		return LaunchConfig{}, err
+	}
+	if flags.NArg() != 0 {
+		return LaunchConfig{}, fmt.Errorf("unexpected arguments: %s", strings.Join(flags.Args(), " "))
+	}
+	if err := launch.Config.Settings.Validate(); err != nil {
+		return LaunchConfig{}, err
+	}
+	return launch, nil
+}
+
+func ParseDesktop(args []string, help io.Writer) (LaunchConfig, error) {
+	launch, err := loadLaunchConfig(args)
+	if err != nil {
+		return LaunchConfig{}, err
+	}
+	flags := flag.NewFlagSet("captioneer-desktop", flag.ContinueOnError)
+	flags.SetOutput(help)
+	registerConfigFlags(flags, &launch, args)
+	registerRecognitionFlags(flags, &launch.Config.Settings)
+
+	output := string(outputModeFor(launch.Config.Outputs))
+	backend := string(launch.Config.Overlay.Backend)
+	flags.StringVar(&output, "output", output, "caption output compatibility preset: terminal, overlay, or both")
+	flags.StringVar(&backend, "overlay-backend", backend, "display backend: auto, wayland, or x11")
+	flags.Float64Var(&launch.Config.Overlay.Opacity, "overlay-opacity", launch.Config.Overlay.Opacity, "caption background opacity from 0 to 1")
+	flags.IntVar(&launch.Config.Overlay.FontSize, "overlay-font-size", launch.Config.Overlay.FontSize, "caption font size in logical pixels")
+	flags.StringVar(&launch.Config.Overlay.FontFamily, "overlay-font-family", launch.Config.Overlay.FontFamily, "caption font family")
+	flags.IntVar(&launch.Config.Overlay.BottomMargin, "overlay-bottom-margin", launch.Config.Overlay.BottomMargin, "distance from the monitor bottom in logical pixels")
+	flags.IntVar(&launch.Config.Overlay.MaxWidth, "overlay-max-width", launch.Config.Overlay.MaxWidth, "fixed caption width in logical pixels before the monitor safety cap")
+	flags.StringVar(&launch.Config.Overlay.Monitor, "overlay-monitor", launch.Config.Overlay.Monitor, "monitor selection: auto, numeric index, or connector name")
+	flags.DurationVar(&launch.Config.Overlay.FinalTimeout, "overlay-final-timeout", launch.Config.Overlay.FinalTimeout, "completed-caption lifetime; zero keeps lines until the six-line cap removes them")
+	flags.BoolVar(&launch.Config.Overlay.ClickThrough, "overlay-click-through", launch.Config.Overlay.ClickThrough, "pass pointer input through the caption window")
+	flags.BoolVar(&launch.Config.Outputs.History, "gui-history", launch.Config.Outputs.History, "retain captions in the GUI history")
+	flags.BoolVar(&launch.Config.Outputs.StderrDiagnostics, "stderr-diagnostics", launch.Config.Outputs.StderrDiagnostics, "mirror diagnostics to stderr")
+	flags.BoolVar(&launch.Config.GUI.StartCaptions, "start-captions", launch.Config.GUI.StartCaptions, "start caption processing when the GUI opens")
+	flags.BoolVar(&launch.Config.GUI.MainWindowAlwaysOnTop, "main-window-always-on-top", launch.Config.GUI.MainWindowAlwaysOnTop, "request that the main window remain above other windows")
+	flags.BoolVar(&launch.Config.TranscriptLog.Enabled, "caption-log", launch.Config.TranscriptLog.Enabled, "save finalized captions to a timestamped transcript file")
+	flags.StringVar(&launch.Config.TranscriptLog.Directory, "caption-log-dir", launch.Config.TranscriptLog.Directory, "directory for timestamped caption transcript files")
+	if err := flags.Parse(args); err != nil {
+		return LaunchConfig{}, err
+	}
+	if flags.NArg() != 0 {
+		return LaunchConfig{}, fmt.Errorf("unexpected arguments: %s", strings.Join(flags.Args(), " "))
+	}
+
+	launch.Config.Overlay.Backend = OverlayBackend(backend)
+	if flagWasSet(flags, "output") {
+		switch OutputMode(output) {
+		case OutputTerminal:
+			launch.Config.Outputs.Overlay = false
+			launch.Config.Outputs.StdoutCaptions = true
+		case OutputOverlay:
+			launch.Config.Outputs.Overlay = true
+			launch.Config.Outputs.StdoutCaptions = false
+		case OutputBoth:
+			launch.Config.Outputs.Overlay = true
+			launch.Config.Outputs.StdoutCaptions = true
+		default:
+			return LaunchConfig{}, errors.New("--output must be terminal, overlay, or both")
+		}
+	}
+	if err := launch.Config.Validate(); err != nil {
+		return LaunchConfig{}, err
+	}
+	return launch, nil
+}
+
+func registerRecognitionFlags(flags *flag.FlagSet, settings *Settings) {
+	mode := string(settings.Mode)
+	flags.Var(modeValue{target: &settings.Mode, value: &mode}, "mode", "caption mode: vad or fixed")
+	flags.DurationVar(&settings.ChunkDuration, "chunk-duration", settings.ChunkDuration, "fixed chunk size or VAD preview refresh interval")
+	flags.StringVar(&settings.ModelsDir, "models-dir", settings.ModelsDir, "directory containing downloaded Sherpa models")
+	flags.IntVar(&settings.Threads, "threads", settings.Threads, "CPU threads used by recognition and VAD")
+	flags.Float64Var(&settings.PreviewThresholdDB, "preview-threshold-dbfs", settings.PreviewThresholdDB, "RMS dBFS gate below which recognition stays idle")
+	flags.Float64Var(&settings.VADThreshold, "vad-threshold", settings.VADThreshold, "speech detection sensitivity from 0 to 1; higher rejects more non-speech")
+	flags.BoolVar(&settings.ModelAutoRestart, "model-auto-restart", settings.ModelAutoRestart, "restart the isolated model worker after a crash or timeout")
+	flags.DurationVar(&settings.ModelTimeout, "model-timeout", settings.ModelTimeout, "maximum model startup or processing time; zero disables hang detection")
+	flags.DurationVar(&settings.ModelShutdownTimeout, "model-shutdown-timeout", settings.ModelShutdownTimeout, "time allowed for model flush and cleanup before force-killing the worker")
+}
+
+type modeValue struct {
+	target *Mode
+	value  *string
+}
+
+func (v modeValue) String() string {
+	if v.value == nil {
+		return ""
+	}
+	return *v.value
+}
+func (v modeValue) Set(value string) error {
+	*v.value = value
+	*v.target = Mode(value)
+	return nil
+}
+
+func registerConfigFlags(flags *flag.FlagSet, launch *LaunchConfig, args []string) {
+	noConfig := hasNoConfig(args)
+	flags.StringVar(&launch.Path, "config", launch.Path, "configuration file path")
+	flags.BoolVar(&noConfig, "no-config", noConfig, "ignore the saved configuration for this launch")
+}
+
+func loadLaunchConfig(args []string) (LaunchConfig, error) {
+	path, err := ConfigPath()
+	if err != nil {
+		return LaunchConfig{}, err
+	}
+	if explicit := explicitConfigPath(args); explicit != "" {
+		path = explicit
+	}
+	launch := LaunchConfig{Config: DefaultAppConfig(), Path: path}
+	if hasNoConfig(args) {
+		return launch, nil
+	}
+	loaded, loadErr := Load(path)
+	if loadErr != nil {
+		launch.Warning = loadErr
+		return launch, nil
+	}
+	launch.Config = loaded
+	return launch, nil
+}
+
+func explicitConfigPath(args []string) string {
+	for index, argument := range args {
+		if strings.HasPrefix(argument, "--config=") {
+			return strings.TrimPrefix(argument, "--config=")
+		}
+		if argument == "--config" && index+1 < len(args) {
+			return args[index+1]
+		}
+	}
+	return ""
+}
+
+func hasNoConfig(args []string) bool {
+	for _, argument := range args {
+		if argument == "--no-config" || argument == "--no-config=true" {
+			return true
+		}
+	}
+	return false
+}
+
+func flagWasSet(flags *flag.FlagSet, name string) bool {
+	set := false
+	flags.Visit(func(candidate *flag.Flag) {
+		if candidate.Name == name {
+			set = true
+		}
+	})
+	return set
+}
+
+func outputModeFor(outputs OutputSettings) OutputMode {
+	switch {
+	case outputs.Overlay && outputs.StdoutCaptions:
+		return OutputBoth
+	case outputs.StdoutCaptions:
+		return OutputTerminal
+	default:
+		return OutputOverlay
+	}
+}

src/config/cli_test.go

@@ -0,0 +1,80 @@
+package config
+
+import (
+	"bytes"
+	"errors"
+	"flag"
+	"io"
+	"path/filepath"
+	"testing"
+)
+
+func TestCLIHelpDoesNotPanic(t *testing.T) {
+	var help bytes.Buffer
+	_, err := Parse([]string{"--help"}, &help)
+	if !errors.Is(err, flag.ErrHelp) {
+		t.Fatalf("Parse(--help) error = %v", err)
+	}
+	if !bytes.Contains(help.Bytes(), []byte("-mode")) {
+		t.Fatalf("help output did not contain mode flag:\n%s", help.String())
+	}
+}
+
+func TestCLIUsesSavedConfigThenExplicitFlags(t *testing.T) {
+	configHome := t.TempDir()
+	t.Setenv("XDG_CONFIG_HOME", configHome)
+	path := filepath.Join(configHome, "captioneer", configFileName)
+	saved := DefaultAppConfig()
+	saved.Settings.Threads = 5
+	saved.Settings.ModelsDir = "saved-models"
+	if err := Save(path, saved); err != nil {
+		t.Fatal(err)
+	}
+
+	launch, err := Parse([]string{"--threads=7"}, io.Discard)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if launch.Config.Settings.Threads != 7 || launch.Config.Settings.ModelsDir != "saved-models" {
+		t.Fatalf("precedence result = %#v", launch.Config.Settings)
+	}
+}
+
+func TestCLINoConfigUsesBuiltInDefaults(t *testing.T) {
+	configHome := t.TempDir()
+	t.Setenv("XDG_CONFIG_HOME", configHome)
+	path := filepath.Join(configHome, "captioneer", configFileName)
+	saved := DefaultAppConfig()
+	saved.Settings.Threads = 9
+	if err := Save(path, saved); err != nil {
+		t.Fatal(err)
+	}
+
+	launch, err := Parse([]string{"--no-config"}, io.Discard)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if launch.Config.Settings.Threads != DefaultSettings().Threads {
+		t.Fatalf("--no-config threads = %d", launch.Config.Settings.Threads)
+	}
+}
+
+func TestDesktopOutputFlagOverridesSavedCaptionDestinations(t *testing.T) {
+	configHome := t.TempDir()
+	t.Setenv("XDG_CONFIG_HOME", configHome)
+	path := filepath.Join(configHome, "captioneer", configFileName)
+	saved := DefaultAppConfig()
+	saved.Outputs.Overlay = true
+	saved.Outputs.StdoutCaptions = false
+	if err := Save(path, saved); err != nil {
+		t.Fatal(err)
+	}
+
+	launch, err := ParseDesktop([]string{"--output=both"}, io.Discard)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !launch.Config.Outputs.Overlay || !launch.Config.Outputs.StdoutCaptions {
+		t.Fatalf("output flags = %#v", launch.Config.Outputs)
+	}
+}

src/config/config.go

@@ -3,12 +3,12 @@ package config
 
 import (
 	"errors"
-	"flag"
 	"strings"
 	"time"
 )
 
 const (
+	CurrentConfigVersion        = 1
 	DefaultModelsDir            = "models"
 	DefaultVADThreshold         = 0.5
 	DefaultOverlayFontFamily    = "Sans"
@@ -36,21 +36,18 @@ type Settings struct {
 	ModelShutdownTimeout time.Duration
 }
 
-func Parse() Settings {
+func DefaultSettings() Settings {
-	var settings Settings
+	return Settings{
-	mode := ""
+		Mode:                 ModeVAD,
-	flag.StringVar(&mode, "mode", "", "caption mode: vad or fixed (required)")
+		ChunkDuration:        time.Second,
-	flag.DurationVar(&settings.ChunkDuration, "chunk-duration", time.Second, "fixed chunk size or VAD preview refresh interval")
+		ModelsDir:            DefaultModelsDir,
-	flag.StringVar(&settings.ModelsDir, "models-dir", DefaultModelsDir, "directory containing downloaded Sherpa models")
+		Threads:              2,
-	flag.IntVar(&settings.Threads, "threads", 2, "CPU threads used by recognition and VAD")
+		PreviewThresholdDB:   -45,
-	flag.Float64Var(&settings.PreviewThresholdDB, "preview-threshold-dbfs", -45, "RMS dBFS gate below which recognition stays idle")
+		VADThreshold:         DefaultVADThreshold,
-	flag.Float64Var(&settings.VADThreshold, "vad-threshold", DefaultVADThreshold, "speech detection sensitivity from 0 to 1; higher rejects more non-speech")
+		ModelAutoRestart:     true,
-	flag.BoolVar(&settings.ModelAutoRestart, "model-auto-restart", true, "restart the isolated model worker after a crash or timeout")
+		ModelTimeout:         DefaultModelTimeout,
-	flag.DurationVar(&settings.ModelTimeout, "model-timeout", DefaultModelTimeout, "maximum model startup or processing time; zero disables hang detection")
+		ModelShutdownTimeout: DefaultModelShutdownTimeout,
-	flag.DurationVar(&settings.ModelShutdownTimeout, "model-shutdown-timeout", DefaultModelShutdownTimeout, "time allowed for model flush and cleanup before force-killing the worker")
+	}
-	flag.Parse()
-	settings.Mode = Mode(mode)
-	return settings
 }
 
 type OutputMode string
@@ -79,6 +76,70 @@ type OverlaySettings struct {
 	Monitor      string
 	FinalTimeout time.Duration
 	ClickThrough bool
+	// PositionX/PositionY are monitor-local logical pixels. -1 means automatic
+	// placement (horizontally centered, BottomMargin above the bottom edge).
+	PositionX int
+	PositionY int
+}
+
+func DefaultOverlaySettings() OverlaySettings {
+	return OverlaySettings{
+		Backend:      BackendAuto,
+		Opacity:      0.90,
+		FontSize:     28,
+		FontFamily:   DefaultOverlayFontFamily,
+		BottomMargin: 100,
+		MaxWidth:     1200,
+		Monitor:      "auto",
+		FinalTimeout: MinimumOverlayFinalLifetime,
+		ClickThrough: true,
+		PositionX:    -1,
+		PositionY:    -1,
+	}
+}
+
+type OutputSettings struct {
+	Overlay           bool
+	History           bool
+	StdoutCaptions    bool
+	StderrDiagnostics bool
+}
+
+type GUISettings struct {
+	StartCaptions         bool
+	MainWindowAlwaysOnTop bool
+}
+
+type TranscriptLogSettings struct {
+	Enabled   bool
+	Directory string
+}
+
+type AppConfig struct {
+	Version       int
+	Settings      Settings
+	Overlay       OverlaySettings
+	Outputs       OutputSettings
+	GUI           GUISettings
+	TranscriptLog TranscriptLogSettings
+}
+
+func DefaultAppConfig() AppConfig {
+	return AppConfig{
+		Version:  CurrentConfigVersion,
+		Settings: DefaultSettings(),
+		Overlay:  DefaultOverlaySettings(),
+		Outputs: OutputSettings{
+			Overlay:           true,
+			History:           true,
+			StdoutCaptions:    false,
+			StderrDiagnostics: true,
+		},
+		GUI: GUISettings{StartCaptions: true},
+		TranscriptLog: TranscriptLogSettings{
+			Directory: DefaultTranscriptDirectory(),
+		},
+	}
 }
 
 type DesktopSettings struct {
@@ -87,38 +148,6 @@ type DesktopSettings struct {
 	Overlay OverlaySettings
 }
 
-func ParseDesktop() DesktopSettings {
-	flags := flag.CommandLine
-	var desktop DesktopSettings
-	var mode string
-	var output string
-	var backend string
-	flags.StringVar(&mode, "mode", "", "caption mode: vad or fixed (required)")
-	flags.DurationVar(&desktop.ChunkDuration, "chunk-duration", time.Second, "fixed chunk size or VAD preview refresh interval")
-	flags.StringVar(&desktop.ModelsDir, "models-dir", DefaultModelsDir, "directory containing downloaded Sherpa models")
-	flags.IntVar(&desktop.Threads, "threads", 2, "CPU threads used by recognition and VAD")
-	flags.Float64Var(&desktop.PreviewThresholdDB, "preview-threshold-dbfs", -45, "RMS dBFS gate below which recognition stays idle")
-	flags.Float64Var(&desktop.VADThreshold, "vad-threshold", DefaultVADThreshold, "speech detection sensitivity from 0 to 1; higher rejects more non-speech")
-	flags.BoolVar(&desktop.ModelAutoRestart, "model-auto-restart", true, "restart the isolated model worker after a crash or timeout")
-	flags.DurationVar(&desktop.ModelTimeout, "model-timeout", DefaultModelTimeout, "maximum model startup or processing time; zero disables hang detection")
-	flags.DurationVar(&desktop.ModelShutdownTimeout, "model-shutdown-timeout", DefaultModelShutdownTimeout, "time allowed for model flush and cleanup before force-killing the worker")
-	flags.StringVar(&output, "output", "", "caption output: terminal, overlay, or both (required)")
-	flags.StringVar(&backend, "overlay-backend", "auto", "display backend: auto, wayland, or x11")
-	flags.Float64Var(&desktop.Overlay.Opacity, "overlay-opacity", 0.90, "caption background opacity from 0 to 1")
-	flags.IntVar(&desktop.Overlay.FontSize, "overlay-font-size", 28, "caption font size in logical pixels")
-	flags.StringVar(&desktop.Overlay.FontFamily, "overlay-font-family", DefaultOverlayFontFamily, "caption font family")
-	flags.IntVar(&desktop.Overlay.BottomMargin, "overlay-bottom-margin", 100, "distance from the monitor bottom in logical pixels")
-	flags.IntVar(&desktop.Overlay.MaxWidth, "overlay-max-width", 1200, "fixed caption width in logical pixels before the monitor safety cap")
-	flags.StringVar(&desktop.Overlay.Monitor, "overlay-monitor", "auto", "monitor selection: auto, numeric index, or connector name")
-	flags.DurationVar(&desktop.Overlay.FinalTimeout, "overlay-final-timeout", MinimumOverlayFinalLifetime, "completed-caption lifetime; zero keeps lines until the six-line cap removes them")
-	flags.BoolVar(&desktop.Overlay.ClickThrough, "overlay-click-through", true, "pass pointer input through the caption window")
-	flag.Parse()
-	desktop.Mode = Mode(mode)
-	desktop.Output = OutputMode(output)
-	desktop.Overlay.Backend = OverlayBackend(backend)
-	return desktop
-}
-
 func (s Settings) Validate() error {
 	if s.Mode != ModeFixed && s.Mode != ModeVAD {
 		return errors.New("--mode is required and must be either fixed or vad")
@@ -148,32 +177,58 @@ func (s DesktopSettings) Validate() error {
 	if s.Output != OutputTerminal && s.Output != OutputOverlay && s.Output != OutputBoth {
 		return errors.New("--output is required and must be terminal, overlay, or both")
 	}
-	if s.Overlay.Backend != BackendAuto && s.Overlay.Backend != BackendWayland && s.Overlay.Backend != BackendX11 {
+	return s.Overlay.Validate()
+}
+
+func (s OverlaySettings) Validate() error {
+	if s.Backend != BackendAuto && s.Backend != BackendWayland && s.Backend != BackendX11 {
 		return errors.New("--overlay-backend must be auto, wayland, or x11")
 	}
-	if s.Overlay.Opacity < 0 || s.Overlay.Opacity > 1 {
+	if s.Opacity < 0 || s.Opacity > 1 {
 		return errors.New("--overlay-opacity must be between 0 and 1")
 	}
-	if s.Overlay.FontSize <= 0 {
+	if s.FontSize <= 0 {
 		return errors.New("--overlay-font-size must be positive")
 	}
-	if strings.TrimSpace(s.Overlay.FontFamily) == "" {
+	if strings.TrimSpace(s.FontFamily) == "" {
 		return errors.New("--overlay-font-family cannot be empty")
 	}
-	if s.Overlay.BottomMargin < 0 {
+	if s.BottomMargin < 0 {
 		return errors.New("--overlay-bottom-margin cannot be negative")
 	}
-	if s.Overlay.MaxWidth <= 0 {
+	if s.MaxWidth <= 0 {
 		return errors.New("--overlay-max-width must be positive")
 	}
-	if s.Overlay.FinalTimeout < 0 {
+	if s.FinalTimeout < 0 {
 		return errors.New("--overlay-final-timeout cannot be negative")
 	}
-	if s.Overlay.FinalTimeout > 0 && s.Overlay.FinalTimeout < MinimumOverlayFinalLifetime {
+	if s.FinalTimeout > 0 && s.FinalTimeout < MinimumOverlayFinalLifetime {
 		return errors.New("--overlay-final-timeout must be zero or at least 3s")
 	}
-	if s.Overlay.Monitor == "" {
+	if s.Monitor == "" {
 		return errors.New("--overlay-monitor cannot be empty")
 	}
+	if s.PositionX < -1 {
+		return errors.New("overlay position x cannot be less than -1")
+	}
+	if s.PositionY < -1 {
+		return errors.New("overlay position y cannot be less than -1")
+	}
+	return nil
+}
+
+func (c AppConfig) Validate() error {
+	if c.Version != CurrentConfigVersion {
+		return errors.New("unsupported configuration version")
+	}
+	if err := c.Settings.Validate(); err != nil {
+		return err
+	}
+	if err := c.Overlay.Validate(); err != nil {
+		return err
+	}
+	if c.TranscriptLog.Enabled && strings.TrimSpace(c.TranscriptLog.Directory) == "" {
+		return errors.New("caption log directory cannot be empty when logging is enabled")
+	}
 	return nil
 }

src/config/store.go

@@ -0,0 +1,250 @@
+package config
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+const configFileName = "config.json"
+
+type diskConfig struct {
+	Version int `json:"version"`
+	General struct {
+		StartCaptions         bool `json:"start_captions"`
+		MainWindowAlwaysOnTop bool `json:"main_window_always_on_top"`
+	} `json:"general"`
+	Recognition struct {
+		Mode                 Mode    `json:"mode"`
+		ChunkDuration        string  `json:"chunk_duration"`
+		ModelsDir            string  `json:"models_directory"`
+		Threads              int     `json:"threads"`
+		PreviewThresholdDB   float64 `json:"preview_threshold_dbfs"`
+		VADThreshold         float64 `json:"vad_threshold"`
+		ModelAutoRestart     bool    `json:"model_auto_restart"`
+		ModelTimeout         string  `json:"model_timeout"`
+		ModelShutdownTimeout string  `json:"model_shutdown_timeout"`
+	} `json:"recognition"`
+	Outputs struct {
+		Overlay           bool `json:"overlay"`
+		History           bool `json:"history"`
+		StdoutCaptions    bool `json:"stdout_captions"`
+		StderrDiagnostics bool `json:"stderr_diagnostics"`
+	} `json:"outputs"`
+	Overlay struct {
+		Backend      OverlayBackend `json:"backend"`
+		Opacity      float64        `json:"opacity"`
+		FontSize     int            `json:"font_size"`
+		FontFamily   string         `json:"font_family"`
+		BottomMargin int            `json:"bottom_margin"`
+		MaxWidth     int            `json:"max_width"`
+		Monitor      string         `json:"monitor"`
+		FinalTimeout string         `json:"final_timeout"`
+		ClickThrough bool           `json:"click_through"`
+		PositionX    *int           `json:"position_x,omitempty"`
+		PositionY    *int           `json:"position_y,omitempty"`
+	} `json:"overlay"`
+	TranscriptLog struct {
+		Enabled   bool   `json:"enabled"`
+		Directory string `json:"directory"`
+	} `json:"transcript_log"`
+}
+
+func ConfigPath() (string, error) {
+	base, err := os.UserConfigDir()
+	if err != nil {
+		return "", fmt.Errorf("find user configuration directory: %w", err)
+	}
+	return filepath.Join(base, "captioneer", configFileName), nil
+}
+
+func DefaultTranscriptDirectory() string {
+	if stateHome := os.Getenv("XDG_STATE_HOME"); filepath.IsAbs(stateHome) {
+		return filepath.Join(stateHome, "captioneer", "transcripts")
+	}
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return filepath.Join("captioneer", "transcripts")
+	}
+	return filepath.Join(home, ".local", "state", "captioneer", "transcripts")
+}
+
+func Load(path string) (AppConfig, error) {
+	defaults := DefaultAppConfig()
+	data, err := os.ReadFile(path)
+	if errors.Is(err, os.ErrNotExist) {
+		return defaults, nil
+	}
+	if err != nil {
+		return defaults, fmt.Errorf("read configuration: %w", err)
+	}
+
+	disk := diskFromConfig(defaults)
+	if err := json.Unmarshal(data, &disk); err != nil {
+		return defaults, fmt.Errorf("parse configuration: %w", err)
+	}
+	loaded, err := disk.toConfig()
+	if err != nil {
+		return defaults, err
+	}
+	if err := loaded.Validate(); err != nil {
+		return defaults, fmt.Errorf("validate configuration: %w", err)
+	}
+	return loaded, nil
+}
+
+func Save(path string, config AppConfig) error {
+	config.Version = CurrentConfigVersion
+	if err := config.Validate(); err != nil {
+		return fmt.Errorf("validate configuration: %w", err)
+	}
+	data, err := json.MarshalIndent(diskFromConfig(config), "", "  ")
+	if err != nil {
+		return fmt.Errorf("encode configuration: %w", err)
+	}
+	data = append(data, '\n')
+
+	directory := filepath.Dir(path)
+	if err := os.MkdirAll(directory, 0o700); err != nil {
+		return fmt.Errorf("create configuration directory: %w", err)
+	}
+	temporary, err := os.CreateTemp(directory, ".config-*.tmp")
+	if err != nil {
+		return fmt.Errorf("create temporary configuration: %w", err)
+	}
+	temporaryPath := temporary.Name()
+	defer os.Remove(temporaryPath)
+	if err := temporary.Chmod(0o600); err != nil {
+		temporary.Close()
+		return fmt.Errorf("secure temporary configuration: %w", err)
+	}
+	if _, err := temporary.Write(data); err != nil {
+		temporary.Close()
+		return fmt.Errorf("write temporary configuration: %w", err)
+	}
+	if err := temporary.Sync(); err != nil {
+		temporary.Close()
+		return fmt.Errorf("sync temporary configuration: %w", err)
+	}
+	if err := temporary.Close(); err != nil {
+		return fmt.Errorf("close temporary configuration: %w", err)
+	}
+	if err := os.Rename(temporaryPath, path); err != nil {
+		return fmt.Errorf("replace configuration: %w", err)
+	}
+	return nil
+}
+
+func diskFromConfig(config AppConfig) diskConfig {
+	var disk diskConfig
+	disk.Version = config.Version
+	disk.General.StartCaptions = config.GUI.StartCaptions
+	disk.General.MainWindowAlwaysOnTop = config.GUI.MainWindowAlwaysOnTop
+	disk.Recognition.Mode = config.Settings.Mode
+	disk.Recognition.ChunkDuration = config.Settings.ChunkDuration.String()
+	disk.Recognition.ModelsDir = config.Settings.ModelsDir
+	disk.Recognition.Threads = config.Settings.Threads
+	disk.Recognition.PreviewThresholdDB = config.Settings.PreviewThresholdDB
+	disk.Recognition.VADThreshold = config.Settings.VADThreshold
+	disk.Recognition.ModelAutoRestart = config.Settings.ModelAutoRestart
+	disk.Recognition.ModelTimeout = config.Settings.ModelTimeout.String()
+	disk.Recognition.ModelShutdownTimeout = config.Settings.ModelShutdownTimeout.String()
+	disk.Outputs.Overlay = config.Outputs.Overlay
+	disk.Outputs.History = config.Outputs.History
+	disk.Outputs.StdoutCaptions = config.Outputs.StdoutCaptions
+	disk.Outputs.StderrDiagnostics = config.Outputs.StderrDiagnostics
+	disk.Overlay.Backend = config.Overlay.Backend
+	disk.Overlay.Opacity = config.Overlay.Opacity
+	disk.Overlay.FontSize = config.Overlay.FontSize
+	disk.Overlay.FontFamily = config.Overlay.FontFamily
+	disk.Overlay.BottomMargin = config.Overlay.BottomMargin
+	disk.Overlay.MaxWidth = config.Overlay.MaxWidth
+	disk.Overlay.Monitor = config.Overlay.Monitor
+	disk.Overlay.FinalTimeout = config.Overlay.FinalTimeout.String()
+	disk.Overlay.ClickThrough = config.Overlay.ClickThrough
+	positionX := config.Overlay.PositionX
+	positionY := config.Overlay.PositionY
+	disk.Overlay.PositionX = &positionX
+	disk.Overlay.PositionY = &positionY
+	disk.TranscriptLog.Enabled = config.TranscriptLog.Enabled
+	disk.TranscriptLog.Directory = config.TranscriptLog.Directory
+	return disk
+}
+
+func (disk diskConfig) toConfig() (AppConfig, error) {
+	chunkDuration, err := parseStoredDuration("chunk duration", disk.Recognition.ChunkDuration)
+	if err != nil {
+		return AppConfig{}, err
+	}
+	modelTimeout, err := parseStoredDuration("model timeout", disk.Recognition.ModelTimeout)
+	if err != nil {
+		return AppConfig{}, err
+	}
+	shutdownTimeout, err := parseStoredDuration("model shutdown timeout", disk.Recognition.ModelShutdownTimeout)
+	if err != nil {
+		return AppConfig{}, err
+	}
+	finalTimeout, err := parseStoredDuration("overlay final timeout", disk.Overlay.FinalTimeout)
+	if err != nil {
+		return AppConfig{}, err
+	}
+	positionX, positionY := -1, -1
+	if disk.Overlay.PositionX != nil {
+		positionX = *disk.Overlay.PositionX
+	}
+	if disk.Overlay.PositionY != nil {
+		positionY = *disk.Overlay.PositionY
+	}
+	return AppConfig{
+		Version: disk.Version,
+		GUI: GUISettings{
+			StartCaptions:         disk.General.StartCaptions,
+			MainWindowAlwaysOnTop: disk.General.MainWindowAlwaysOnTop,
+		},
+		Settings: Settings{
+			Mode:                 disk.Recognition.Mode,
+			ChunkDuration:        chunkDuration,
+			ModelsDir:            disk.Recognition.ModelsDir,
+			Threads:              disk.Recognition.Threads,
+			PreviewThresholdDB:   disk.Recognition.PreviewThresholdDB,
+			VADThreshold:         disk.Recognition.VADThreshold,
+			ModelAutoRestart:     disk.Recognition.ModelAutoRestart,
+			ModelTimeout:         modelTimeout,
+			ModelShutdownTimeout: shutdownTimeout,
+		},
+		Outputs: OutputSettings{
+			Overlay:           disk.Outputs.Overlay,
+			History:           disk.Outputs.History,
+			StdoutCaptions:    disk.Outputs.StdoutCaptions,
+			StderrDiagnostics: disk.Outputs.StderrDiagnostics,
+		},
+		Overlay: OverlaySettings{
+			Backend:      disk.Overlay.Backend,
+			Opacity:      disk.Overlay.Opacity,
+			FontSize:     disk.Overlay.FontSize,
+			FontFamily:   disk.Overlay.FontFamily,
+			BottomMargin: disk.Overlay.BottomMargin,
+			MaxWidth:     disk.Overlay.MaxWidth,
+			Monitor:      disk.Overlay.Monitor,
+			FinalTimeout: finalTimeout,
+			ClickThrough: disk.Overlay.ClickThrough,
+			PositionX:    positionX,
+			PositionY:    positionY,
+		},
+		TranscriptLog: TranscriptLogSettings{
+			Enabled:   disk.TranscriptLog.Enabled,
+			Directory: disk.TranscriptLog.Directory,
+		},
+	}, nil
+}
+
+func parseStoredDuration(name, value string) (time.Duration, error) {
+	duration, err := time.ParseDuration(value)
+	if err != nil {
+		return 0, fmt.Errorf("parse %s %q: %w", name, value, err)
+	}
+	return duration, nil
+}

src/config/store_test.go

@@ -0,0 +1,77 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestConfigRoundTripUsesReadableDurations(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "nested", "config.json")
+	want := DefaultAppConfig()
+	want.Settings.ChunkDuration = 750 * time.Millisecond
+	want.Settings.ModelsDir = "models with spaces"
+	want.Outputs.StdoutCaptions = true
+	want.GUI.MainWindowAlwaysOnTop = true
+	want.TranscriptLog.Enabled = true
+	want.TranscriptLog.Directory = filepath.Join(t.TempDir(), "transcripts")
+
+	if err := Save(path, want); err != nil {
+		t.Fatal(err)
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(data), `"chunk_duration": "750ms"`) {
+		t.Fatalf("duration was not stored readably:\n%s", data)
+	}
+	got, err := Load(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Fatalf("round trip = %#v, want %#v", got, want)
+	}
+}
+
+func TestMissingConfigUsesDefaults(t *testing.T) {
+	got, err := Load(filepath.Join(t.TempDir(), "missing.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := DefaultAppConfig()
+	if got != want {
+		t.Fatalf("missing config = %#v, want %#v", got, want)
+	}
+}
+
+func TestPartialConfigKeepsOtherDefaults(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"recognition":{"threads":6}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	got, err := Load(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Settings.Threads != 6 || got.Settings.Mode != ModeVAD || got.Overlay.FontSize != 28 {
+		t.Fatalf("partial config did not inherit defaults: %#v", got)
+	}
+}
+
+func TestInvalidStoredDurationReturnsDefaultsAndError(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"recognition":{"chunk_duration":"soon"}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	got, err := Load(path)
+	if err == nil || !strings.Contains(err.Error(), "chunk duration") {
+		t.Fatalf("invalid duration error = %v", err)
+	}
+	if got != DefaultAppConfig() {
+		t.Fatalf("invalid config fallback = %#v", got)
+	}
+}

src/diagnostics/diagnostics.go

@@ -0,0 +1,150 @@
+// Package diagnostics provides bounded structured application logging.
+package diagnostics
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+	"sync"
+	"time"
+)
+
+type Severity string
+
+const (
+	Debug   Severity = "debug"
+	Info    Severity = "info"
+	Warning Severity = "warning"
+	Error   Severity = "error"
+)
+
+type Entry struct {
+	At       time.Time
+	Severity Severity
+	Category string
+	Message  string
+}
+
+type Log struct {
+	mu          sync.Mutex
+	capacity    int
+	entries     []Entry
+	mirror      io.Writer
+	subscribers map[chan Entry]struct{}
+}
+
+func New(capacity int, mirror io.Writer) *Log {
+	if capacity < 1 {
+		capacity = 1
+	}
+	if mirror == nil {
+		mirror = io.Discard
+	}
+	return &Log{
+		capacity:    capacity,
+		mirror:      mirror,
+		subscribers: make(map[chan Entry]struct{}),
+	}
+}
+
+func (l *Log) Add(severity Severity, category, message string) {
+	message = strings.TrimSpace(message)
+	if message == "" {
+		return
+	}
+	entry := Entry{At: time.Now(), Severity: severity, Category: category, Message: message}
+	l.mu.Lock()
+	l.entries = append(l.entries, entry)
+	if len(l.entries) > l.capacity {
+		copy(l.entries, l.entries[len(l.entries)-l.capacity:])
+		l.entries = l.entries[:l.capacity]
+	}
+	fmt.Fprintf(l.mirror, "%s %-7s [%s] %s\n", entry.At.Format(time.RFC3339), strings.ToUpper(string(severity)), category, message)
+	for subscriber := range l.subscribers {
+		select {
+		case subscriber <- entry:
+		default:
+			select {
+			case <-subscriber:
+			default:
+			}
+			select {
+			case subscriber <- entry:
+			default:
+			}
+		}
+	}
+	l.mu.Unlock()
+}
+
+func (l *Log) Entries() []Entry {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	return append([]Entry(nil), l.entries...)
+}
+
+func (l *Log) Clear() {
+	l.mu.Lock()
+	l.entries = nil
+	l.mu.Unlock()
+}
+
+func (l *Log) SetMirror(mirror io.Writer) {
+	if mirror == nil {
+		mirror = io.Discard
+	}
+	l.mu.Lock()
+	l.mirror = mirror
+	l.mu.Unlock()
+}
+
+func (l *Log) Subscribe(buffer int) (<-chan Entry, func()) {
+	if buffer < 1 {
+		buffer = 1
+	}
+	updates := make(chan Entry, buffer)
+	l.mu.Lock()
+	l.subscribers[updates] = struct{}{}
+	l.mu.Unlock()
+	return updates, func() {
+		l.mu.Lock()
+		if _, ok := l.subscribers[updates]; ok {
+			delete(l.subscribers, updates)
+			close(updates)
+		}
+		l.mu.Unlock()
+	}
+}
+
+func (l *Log) Writer(severity Severity, category string) io.Writer {
+	return &lineWriter{log: l, severity: severity, category: category}
+}
+
+type lineWriter struct {
+	mu       sync.Mutex
+	log      *Log
+	severity Severity
+	category string
+	buffer   bytes.Buffer
+}
+
+func (w *lineWriter) Write(data []byte) (int, error) {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	w.buffer.Write(data)
+	for {
+		line, err := w.buffer.ReadString('\n')
+		if err != nil {
+			w.buffer.WriteString(line)
+			break
+		}
+		severity := w.severity
+		trimmed := strings.TrimSpace(line)
+		if strings.HasPrefix(strings.ToLower(trimmed), "warning:") {
+			severity = Warning
+		}
+		w.log.Add(severity, w.category, trimmed)
+	}
+	return len(data), nil
+}

src/diagnostics/diagnostics_test.go

@@ -0,0 +1,20 @@
+package diagnostics
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestLogBoundsEntriesAndClassifiesWarningLines(t *testing.T) {
+	var mirror bytes.Buffer
+	log := New(2, &mirror)
+	writer := log.Writer(Info, "engine")
+	_, _ = writer.Write([]byte("first\nwarning: overloaded\nthird\n"))
+	entries := log.Entries()
+	if len(entries) != 2 || entries[0].Severity != Warning || entries[1].Message != "third" {
+		t.Fatalf("entries = %#v", entries)
+	}
+	if mirror.Len() == 0 {
+		t.Fatal("log was not mirrored")
+	}
+}

src/gui/app.go

@@ -0,0 +1,631 @@
+//go:build gtk
+
+// Package gui implements Captioneer's GTK4 desktop application.
+package gui
+
+import (
+	"context"
+	_ "embed"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"os/signal"
+	"path/filepath"
+	"strings"
+	"sync"
+	"syscall"
+	"time"
+
+	"github.com/diamondburned/gotk4/pkg/gdk/v4"
+	"github.com/diamondburned/gotk4/pkg/gio/v2"
+	"github.com/diamondburned/gotk4/pkg/glib/v2"
+	"github.com/diamondburned/gotk4/pkg/gtk/v4"
+	"tea.chunkbyte.com/kato/captioneer/src/app"
+	"tea.chunkbyte.com/kato/captioneer/src/config"
+	"tea.chunkbyte.com/kato/captioneer/src/diagnostics"
+	"tea.chunkbyte.com/kato/captioneer/src/output"
+	"tea.chunkbyte.com/kato/captioneer/src/output/history"
+	"tea.chunkbyte.com/kato/captioneer/src/output/overlay"
+	"tea.chunkbyte.com/kato/captioneer/src/output/terminal"
+	"tea.chunkbyte.com/kato/captioneer/src/output/transcript"
+)
+
+const (
+	applicationID   = "com.chunkbyte.captioneer"
+	historyCapacity = 500
+	consoleCapacity = 2000
+)
+
+//go:embed style.css
+var applicationCSS string
+
+type Application struct {
+	launch  config.LaunchConfig
+	config  config.AppConfig
+	applied config.AppConfig
+	stdout  io.Writer
+	stderr  io.Writer
+
+	gtkApp *gtk.Application
+	window *gtk.ApplicationWindow
+	stack  *gtk.Stack
+
+	router     *output.Router
+	history    *history.Sink
+	log        *diagnostics.Log
+	controller *app.Controller
+	overlay    *overlay.Sink
+	transcript *transcript.Sink
+
+	statusLabel      *gtk.Label
+	statusDot        *gtk.Label
+	startStopButton  *gtk.Button
+	statusSource     *gtk.Label
+	statusSpeech     *gtk.Label
+	statusOutputs    *gtk.Label
+	captionBuffer    *gtk.TextBuffer
+	captionView      *gtk.TextView
+	captionScroll    *gtk.ScrolledWindow
+	captionMetaTag   *gtk.TextTag
+	captionHintTag   *gtk.TextTag
+	provisionalLabel *gtk.Label
+	consoleBuffer    *gtk.TextBuffer
+	consoleView      *gtk.TextView
+	consoleScroll    *gtk.ScrolledWindow
+	consoleMetaTag   *gtk.TextTag
+	consoleWarnTag   *gtk.TextTag
+	consoleErrorTag  *gtk.TextTag
+	settings         settingsControls
+	settingsError    *gtk.Label
+	applyButton      *gtk.Button
+	lastShownError   string
+
+	statusUpdates  <-chan app.Status
+	stopStatus     func()
+	historyUpdates <-chan history.Snapshot
+	stopHistory    func()
+	logUpdates     <-chan diagnostics.Entry
+	stopLog        func()
+	uiDone         chan struct{}
+
+	closingMu sync.Mutex
+	closing   bool
+}
+
+func Run(launch config.LaunchConfig, stdout, stderr io.Writer) int {
+	application := newApplication(launch, stdout, stderr)
+	application.gtkApp.ConnectActivate(application.activate)
+	signals := make(chan os.Signal, 1)
+	signal.Notify(signals, os.Interrupt, syscall.SIGTERM)
+	defer signal.Stop(signals)
+	go func() {
+		select {
+		case <-signals:
+			glib.IdleAdd(application.shutdown)
+		case <-application.uiDone:
+		}
+	}()
+	return application.gtkApp.Run([]string{os.Args[0]})
+}
+
+func newApplication(launch config.LaunchConfig, stdout, stderr io.Writer) *Application {
+	mirror := io.Discard
+	if launch.Config.Outputs.StderrDiagnostics {
+		mirror = stderr
+	}
+	log := diagnostics.New(consoleCapacity, mirror)
+	router := output.NewRouter()
+	historySink := history.New(historyCapacity, launch.Config.Outputs.History)
+	_ = router.Set("history", historySink)
+	controller := app.NewController(router, log.Writer(diagnostics.Info, "engine"))
+	return &Application{
+		launch:     launch,
+		config:     launch.Config,
+		applied:    launch.Config,
+		stdout:     stdout,
+		stderr:     stderr,
+		gtkApp:     gtk.NewApplication(applicationID, gio.ApplicationFlagsNone),
+		router:     router,
+		history:    historySink,
+		log:        log,
+		controller: controller,
+		uiDone:     make(chan struct{}),
+	}
+}
+
+func (a *Application) activate() {
+	if a.window != nil {
+		a.window.Present()
+		return
+	}
+	a.installStyle()
+	a.buildWindow()
+	a.installActions()
+	a.subscribeModels()
+	overlay.SetPositionSaver(a.saveOverlayPosition)
+	if a.launch.Warning != nil {
+		a.log.Add(diagnostics.Warning, "configuration", fmt.Sprintf("%v; using built-in defaults", a.launch.Warning))
+	}
+	// Show the main window before creating the overlay so a Layer Shell /
+	// display failure cannot leave the user with a silent no-GUI launch.
+	a.window.Present()
+	if err := a.configureOutputs(a.config, true); err != nil {
+		a.log.Add(diagnostics.Error, "outputs", err.Error())
+	}
+	a.applyAlwaysOnTop(a.config.GUI.MainWindowAlwaysOnTop)
+	if a.config.GUI.StartCaptions {
+		a.startCaptions()
+	}
+}
+
+func (a *Application) installStyle() {
+	provider := gtk.NewCSSProvider()
+	provider.LoadFromString(applicationCSS)
+	gtk.StyleContextAddProviderForDisplay(
+		gdk.DisplayGetDefault(),
+		provider,
+		gtk.STYLE_PROVIDER_PRIORITY_APPLICATION,
+	)
+}
+
+func (a *Application) buildWindow() {
+	a.window = gtk.NewApplicationWindow(a.gtkApp)
+	a.window.SetTitle("Captioneer")
+	a.window.SetDefaultSize(980, 680)
+	a.window.SetSizeRequest(720, 480)
+	a.window.AddCSSClass("captioneer-main")
+	a.window.ConnectCloseRequest(func() bool {
+		a.shutdown()
+		return true
+	})
+
+	header := gtk.NewHeaderBar()
+	header.AddCSSClass("captioneer-header")
+	header.SetShowTitleButtons(true)
+
+	brand := gtk.NewBox(gtk.OrientationHorizontal, 7)
+	if iconPath := findIconPath(); iconPath != "" {
+		icon := gtk.NewImageFromFile(iconPath)
+		icon.SetPixelSize(20)
+		brand.Append(icon)
+	}
+	title := gtk.NewLabel("CAPTIONEER")
+	title.AddCSSClass("captioneer-brand")
+	brand.Append(title)
+	header.PackStart(brand)
+
+	statusBox := gtk.NewBox(gtk.OrientationHorizontal, 6)
+	statusBox.SetHAlign(gtk.AlignCenter)
+	statusBox.AddCSSClass("status-cell")
+	a.statusDot = gtk.NewLabel("●")
+	a.statusDot.AddCSSClass("status-dot")
+	a.statusLabel = gtk.NewLabel("STOPPED · VAD")
+	a.statusLabel.AddCSSClass("status-text")
+	statusBox.Append(a.statusDot)
+	statusBox.Append(a.statusLabel)
+	header.SetTitleWidget(statusBox)
+
+	a.startStopButton = gtk.NewButtonWithLabel("START")
+	a.startStopButton.AddCSSClass("primary-action")
+	a.startStopButton.SetTooltipText("Start or stop caption processing")
+	a.startStopButton.ConnectClicked(a.toggleCaptions)
+	header.PackEnd(a.startStopButton)
+	a.window.SetTitlebar(header)
+
+	root := gtk.NewBox(gtk.OrientationVertical, 0)
+	root.Append(a.buildMenuBar())
+	a.stack = gtk.NewStack()
+	a.stack.SetTransitionType(gtk.StackTransitionTypeNone)
+	a.stack.SetHExpand(true)
+	a.stack.SetVExpand(true)
+
+	tabs := gtk.NewStackSwitcher()
+	tabs.SetStack(a.stack)
+	tabs.SetHAlign(gtk.AlignStart)
+	tabStrip := gtk.NewBox(gtk.OrientationHorizontal, 0)
+	tabStrip.AddCSSClass("captioneer-tabs")
+	tabStrip.Append(tabs)
+	root.Append(tabStrip)
+
+	a.stack.AddTitled(a.buildCaptionsPage(), "captions", "CAPTIONS")
+	a.stack.AddTitled(a.buildConsolePage(), "console", "CONSOLE")
+	a.stack.AddTitled(a.buildSettingsPage(), "settings", "SETTINGS")
+	root.Append(a.stack)
+
+	statusbar := gtk.NewBox(gtk.OrientationHorizontal, 4)
+	statusbar.AddCSSClass("statusbar")
+	a.statusSource = statusSegment("Source: not connected")
+	a.statusSource.SetHExpand(true)
+	a.statusSource.SetXAlign(0)
+	a.statusSource.SetEllipsize(3)
+	a.statusSpeech = statusSegment("Speech: quiet")
+	a.statusOutputs = statusSegment("Outputs: preparing")
+	statusbar.Append(a.statusSource)
+	statusbar.Append(a.statusSpeech)
+	statusbar.Append(a.statusOutputs)
+	root.Append(statusbar)
+	a.window.SetChild(root)
+}
+
+func (a *Application) buildMenuBar() *gtk.PopoverMenuBar {
+	root := gio.NewMenu()
+	file := gio.NewMenu()
+	file.Append("Start Captions", "app.start")
+	file.Append("Stop Captions", "app.stop")
+	file.Append("Restart Captions", "app.restart")
+	file.Append("Clear Caption History", "app.clear-history")
+	file.Append("Exit", "app.exit")
+	root.AppendSubmenu("File", file)
+
+	view := gio.NewMenu()
+	view.Append("Captions", "app.view-captions")
+	view.Append("Console", "app.view-console")
+	view.Append("Settings", "app.view-settings")
+	root.AppendSubmenu("View", view)
+
+	help := gio.NewMenu()
+	help.Append("Copy Diagnostics", "app.copy-diagnostics")
+	help.Append("Open Configuration Folder", "app.open-config-folder")
+	help.Append("About Captioneer", "app.about")
+	root.AppendSubmenu("Help", help)
+	bar := gtk.NewPopoverMenuBarFromModel(root)
+	bar.AddCSSClass("captioneer-menu")
+	return bar
+}
+
+func (a *Application) installActions() {
+	a.addAction("start", a.startCaptions)
+	a.addAction("stop", a.stopCaptions)
+	a.addAction("restart", a.restartCaptions)
+	a.addAction("clear-history", a.history.Clear)
+	a.addAction("exit", a.shutdown)
+	a.addAction("view-captions", func() { a.stack.SetVisibleChildName("captions") })
+	a.addAction("view-console", func() { a.stack.SetVisibleChildName("console") })
+	a.addAction("view-settings", func() { a.stack.SetVisibleChildName("settings") })
+	a.addAction("copy-diagnostics", a.copyDiagnostics)
+	a.addAction("open-config-folder", a.openConfigFolder)
+	a.addAction("about", a.showAbout)
+	a.gtkApp.SetAccelsForAction("app.start", []string{"F5"})
+	a.gtkApp.SetAccelsForAction("app.stop", []string{"<Shift>F5"})
+	a.gtkApp.SetAccelsForAction("app.restart", []string{"<Primary>r"})
+	a.gtkApp.SetAccelsForAction("app.view-captions", []string{"<Alt>1"})
+	a.gtkApp.SetAccelsForAction("app.view-console", []string{"<Alt>2"})
+	a.gtkApp.SetAccelsForAction("app.view-settings", []string{"<Alt>3"})
+	a.gtkApp.SetAccelsForAction("app.exit", []string{"<Primary>q"})
+}
+
+func (a *Application) addAction(name string, callback func()) {
+	action := gio.NewSimpleAction(name, nil)
+	action.ConnectActivate(func(*glib.Variant) { callback() })
+	a.gtkApp.AddAction(action)
+}
+
+func (a *Application) subscribeModels() {
+	a.statusUpdates, a.stopStatus = a.controller.Subscribe(32)
+	a.historyUpdates, a.stopHistory = a.history.Subscribe(8)
+	a.logUpdates, a.stopLog = a.log.Subscribe(128)
+	go a.forwardStatus()
+	go a.forwardHistory()
+	go a.forwardLog()
+}
+
+func (a *Application) forwardStatus() {
+	for {
+		select {
+		case <-a.uiDone:
+			return
+		case status, ok := <-a.statusUpdates:
+			if !ok {
+				return
+			}
+			copy := status
+			glib.IdleAdd(func() { a.renderStatus(copy) })
+		}
+	}
+}
+
+func (a *Application) forwardHistory() {
+	for {
+		select {
+		case <-a.uiDone:
+			return
+		case snapshot, ok := <-a.historyUpdates:
+			if !ok {
+				return
+			}
+			copy := snapshot
+			glib.IdleAdd(func() { a.renderHistory(copy) })
+		}
+	}
+}
+
+func (a *Application) forwardLog() {
+	for {
+		select {
+		case <-a.uiDone:
+			return
+		case _, ok := <-a.logUpdates:
+			if !ok {
+				return
+			}
+			glib.IdleAdd(a.renderConsole)
+		}
+	}
+}
+
+func (a *Application) toggleCaptions() {
+	status := a.controller.Status()
+	switch status.State {
+	case app.StateStopped, app.StateError:
+		a.startCaptions()
+	default:
+		a.stopCaptions()
+	}
+}
+
+func (a *Application) startCaptions() {
+	if err := a.controller.Start(a.applied.Settings); err != nil {
+		a.log.Add(diagnostics.Error, "lifecycle", err.Error())
+		return
+	}
+	a.log.Add(diagnostics.Info, "lifecycle", "Starting caption processing")
+}
+
+func (a *Application) stopCaptions() {
+	go func() {
+		timeout := a.applied.Settings.ModelShutdownTimeout + time.Second
+		ctx, cancel := context.WithTimeout(context.Background(), timeout)
+		defer cancel()
+		if err := a.controller.Stop(ctx); err != nil {
+			a.log.Add(diagnostics.Error, "lifecycle", fmt.Sprintf("Stop captions: %v", err))
+			return
+		}
+		a.log.Add(diagnostics.Info, "lifecycle", "Caption processing stopped")
+	}()
+}
+
+func (a *Application) restartCaptions() {
+	go func() {
+		timeout := a.applied.Settings.ModelShutdownTimeout + 2*time.Second
+		ctx, cancel := context.WithTimeout(context.Background(), timeout)
+		defer cancel()
+		if err := a.controller.Restart(ctx, a.applied.Settings); err != nil {
+			a.log.Add(diagnostics.Error, "lifecycle", fmt.Sprintf("Restart captions: %v", err))
+			return
+		}
+		a.log.Add(diagnostics.Info, "lifecycle", "Caption processing restarted")
+	}()
+}
+
+func (a *Application) saveOverlayPosition(x, y int) {
+	a.config.Overlay.PositionX = x
+	a.config.Overlay.PositionY = y
+	a.applied.Overlay.PositionX = x
+	a.applied.Overlay.PositionY = y
+	if err := config.Save(a.launch.Path, a.config); err != nil {
+		a.log.Add(diagnostics.Error, "configuration", fmt.Sprintf("Save overlay position: %v", err))
+		return
+	}
+	a.log.Add(diagnostics.Info, "overlay", fmt.Sprintf("Saved caption position (%d, %d)", x, y))
+}
+
+func (a *Application) configureOutputs(next config.AppConfig, initial bool) error {
+	var outputErr error
+	a.history.SetEnabled(next.Outputs.History)
+	if next.Outputs.StdoutCaptions {
+		outputErr = joinError(outputErr, a.router.Set("stdout", terminal.New(a.stdout)))
+	} else {
+		outputErr = joinError(outputErr, a.router.Remove("stdout"))
+	}
+
+	if next.TranscriptLog.Enabled {
+		if initial || a.transcript == nil || next.TranscriptLog != a.applied.TranscriptLog {
+			sink, err := transcript.New(next.TranscriptLog.Directory)
+			if err != nil {
+				outputErr = joinError(outputErr, err)
+			} else {
+				a.transcript = sink
+				outputErr = joinError(outputErr, a.router.Set("transcript", sink))
+				a.log.Add(diagnostics.Info, "transcript", "Saving captions to "+sink.Path())
+			}
+		}
+	} else {
+		a.transcript = nil
+		outputErr = joinError(outputErr, a.router.Remove("transcript"))
+	}
+
+	if next.Outputs.Overlay {
+		settings := next.Overlay
+		if !initial && settings.Backend != a.applied.Overlay.Backend {
+			settings.Backend = a.applied.Overlay.Backend
+		}
+		if initial || a.overlay == nil || settings != a.applied.Overlay {
+			sink, warning, err := overlay.New(settings)
+			if warning != "" {
+				a.log.Add(diagnostics.Warning, "overlay", warning)
+			}
+			if err != nil {
+				outputErr = joinError(outputErr, err)
+			} else {
+				a.overlay = sink
+				outputErr = joinError(outputErr, a.router.Set("overlay", sink))
+			}
+		}
+	} else {
+		a.overlay = nil
+		outputErr = joinError(outputErr, a.router.Remove("overlay"))
+	}
+
+	if next.Outputs.StderrDiagnostics {
+		a.log.SetMirror(a.stderr)
+	} else {
+		a.log.SetMirror(io.Discard)
+	}
+	return outputErr
+}
+
+func (a *Application) renderStatus(status app.Status) {
+	a.updateApplyButton()
+	state := strings.ToUpper(string(status.State))
+	overloaded := !status.OverloadedAt.IsZero() && time.Since(status.OverloadedAt) < 5*time.Second
+	if overloaded {
+		state = "OVERLOADED"
+	}
+	mode := strings.ToUpper(string(status.Mode))
+	if mode == "" {
+		mode = strings.ToUpper(string(a.applied.Settings.Mode))
+	}
+	a.statusLabel.SetText(state + " · " + mode)
+	a.statusDot.RemoveCSSClass("status-stopped")
+	a.statusDot.RemoveCSSClass("status-running")
+	a.statusDot.RemoveCSSClass("status-warning")
+	a.statusDot.RemoveCSSClass("status-error")
+	active := status.State != app.StateStopped && status.State != app.StateError
+	switch {
+	case status.State == app.StateError:
+		a.statusDot.AddCSSClass("status-error")
+	case overloaded:
+		a.statusDot.AddCSSClass("status-warning")
+	case active:
+		a.statusDot.AddCSSClass("status-running")
+	default:
+		a.statusDot.AddCSSClass("status-stopped")
+	}
+	if active {
+		a.startStopButton.SetLabel("STOP")
+		a.startStopButton.RemoveCSSClass("primary-action")
+		a.startStopButton.AddCSSClass("danger-action")
+	} else {
+		a.startStopButton.SetLabel("START")
+		a.startStopButton.RemoveCSSClass("danger-action")
+		a.startStopButton.AddCSSClass("primary-action")
+	}
+	speech := "quiet"
+	if status.SpeechActive {
+		speech = "detected"
+	}
+	source := status.Source
+	if source == "" {
+		source = "not connected"
+	}
+	if overloaded {
+		speech += " · OVERLOADED"
+		a.statusSpeech.AddCSSClass("warning-text")
+	} else {
+		a.statusSpeech.RemoveCSSClass("warning-text")
+	}
+	a.statusSource.SetText("Source: " + source)
+	a.statusSpeech.SetText("Speech: " + speech)
+	a.statusOutputs.SetText("Outputs: " + a.outputSummary())
+	if status.LastError != "" && status.State == app.StateError && status.LastError != a.lastShownError {
+		a.log.Add(diagnostics.Error, "engine", status.LastError)
+		a.lastShownError = status.LastError
+	} else if status.LastError == "" {
+		a.lastShownError = ""
+	}
+}
+
+func (a *Application) outputSummary() string {
+	var active []string
+	if a.config.Outputs.Overlay {
+		active = append(active, "overlay")
+	}
+	if a.config.Outputs.History {
+		active = append(active, "history")
+	}
+	if a.config.Outputs.StdoutCaptions {
+		active = append(active, "stdout")
+	}
+	if a.config.TranscriptLog.Enabled {
+		active = append(active, "log file")
+	}
+	if len(active) == 0 {
+		return "none"
+	}
+	return strings.Join(active, ", ")
+}
+
+func (a *Application) copyDiagnostics() {
+	var text strings.Builder
+	status := a.controller.Status()
+	fmt.Fprintf(&text, "Captioneer diagnostics\nState: %s\nMode: %s\nSource: %s\nConfig: %s\n\n", status.State, status.Mode, status.Source, a.launch.Path)
+	for _, entry := range a.log.Entries() {
+		fmt.Fprintf(&text, "%s %-7s [%s] %s\n", entry.At.Format(time.RFC3339), strings.ToUpper(string(entry.Severity)), entry.Category, entry.Message)
+	}
+	gdk.DisplayGetDefault().Clipboard().SetText(text.String())
+	a.log.Add(diagnostics.Info, "gui", "Diagnostics copied to clipboard")
+}
+
+func (a *Application) openConfigFolder() {
+	if err := exec.Command("xdg-open", filepath.Dir(a.launch.Path)).Start(); err != nil {
+		a.log.Add(diagnostics.Error, "gui", fmt.Sprintf("Open configuration folder: %v", err))
+	}
+}
+
+func (a *Application) showAbout() {
+	dialog := gtk.NewAboutDialog()
+	dialog.SetTransientFor(&a.window.Window)
+	dialog.SetModal(true)
+	dialog.SetProgramName("Captioneer")
+	dialog.SetComments("Local live captions for Linux")
+	dialog.SetLicenseType(gtk.LicenseApache20)
+	dialog.SetWebsite("https://tea.chunkbyte.com/kato/captioneer")
+	dialog.Present()
+}
+
+func (a *Application) shutdown() {
+	a.closingMu.Lock()
+	if a.closing {
+		a.closingMu.Unlock()
+		return
+	}
+	a.closing = true
+	a.closingMu.Unlock()
+	a.log.Add(diagnostics.Info, "lifecycle", "Shutting down Captioneer")
+	go func() {
+		timeout := a.applied.Settings.ModelShutdownTimeout + 2*time.Second
+		ctx, cancel := context.WithTimeout(context.Background(), timeout)
+		_ = a.controller.Stop(ctx)
+		cancel()
+		glib.IdleAdd(func() {
+			close(a.uiDone)
+			if a.stopStatus != nil {
+				a.stopStatus()
+				a.stopHistory()
+				a.stopLog()
+			}
+			_ = a.router.Close()
+			a.gtkApp.Quit()
+		})
+	}()
+}
+
+func statusSegment(text string) *gtk.Label {
+	label := gtk.NewLabel(text)
+	label.AddCSSClass("status-segment")
+	return label
+}
+
+func joinError(current, next error) error {
+	if current == nil {
+		return next
+	}
+	if next == nil {
+		return current
+	}
+	return fmt.Errorf("%v; %w", current, next)
+}
+
+func findIconPath() string {
+	candidates := []string{filepath.Join("assets", "icon", "icon.png")}
+	if executable, err := os.Executable(); err == nil {
+		candidates = append(candidates, filepath.Join(filepath.Dir(executable), "assets", "icon", "icon.png"))
+	}
+	for _, candidate := range candidates {
+		if info, err := os.Stat(candidate); err == nil && !info.IsDir() {
+			return candidate
+		}
+	}
+	return ""
+}

src/gui/pages.go

@@ -0,0 +1,267 @@
+//go:build gtk
+
+package gui
+
+import (
+	"fmt"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"github.com/diamondburned/gotk4/pkg/gdk/v4"
+	"github.com/diamondburned/gotk4/pkg/gtk/v4"
+	"tea.chunkbyte.com/kato/captioneer/src/diagnostics"
+	"tea.chunkbyte.com/kato/captioneer/src/output/history"
+)
+
+func (a *Application) buildCaptionsPage() *gtk.Box {
+	page := gtk.NewBox(gtk.OrientationVertical, 7)
+	page.AddCSSClass("captioneer-content")
+
+	toolbar := gtk.NewBox(gtk.OrientationHorizontal, 5)
+	toolbar.AddCSSClass("toolbar")
+	toolbar.Append(labelWithClass("CAPTION HISTORY", "section-title"))
+	spacer := gtk.NewBox(gtk.OrientationHorizontal, 0)
+	spacer.SetHExpand(true)
+	toolbar.Append(spacer)
+	toolbar.Append(toolButton("Copy Selected", "Copy the selected caption text", func() {
+		copyBufferSelection(a.captionBuffer)
+	}))
+	toolbar.Append(toolButton("Copy Transcript", "Copy all final captions", func() {
+		gdk.DisplayGetDefault().Clipboard().SetText(a.history.Transcript())
+	}))
+	toolbar.Append(toolButton("Clear", "Clear visible caption history", a.history.Clear))
+	toolbar.Append(toolButton("Jump to Latest", "Resume at the newest caption", func() {
+		scrollTextViewToEnd(a.captionView, a.captionScroll)
+	}))
+	page.Append(toolbar)
+
+	a.captionBuffer = gtk.NewTextBuffer(nil)
+	a.captionMetaTag = bufferTag(a.captionBuffer, "meta", "#8A9384")
+	a.captionHintTag = bufferTag(a.captionBuffer, "hint", "#6E7763")
+	a.captionView = gtk.NewTextViewWithBuffer(a.captionBuffer)
+	a.captionView.SetEditable(false)
+	a.captionView.SetCursorVisible(true)
+	a.captionView.SetWrapMode(gtk.WrapWordChar)
+	a.captionView.SetTopMargin(9)
+	a.captionView.SetBottomMargin(9)
+	a.captionView.SetLeftMargin(10)
+	a.captionView.SetRightMargin(10)
+	a.captionView.AddCSSClass("caption-view")
+	a.captionScroll = gtk.NewScrolledWindow()
+	a.captionScroll.SetPolicy(gtk.PolicyAutomatic, gtk.PolicyAutomatic)
+	a.captionScroll.SetHExpand(true)
+	a.captionScroll.SetVExpand(true)
+	a.captionScroll.SetChild(a.captionView)
+	a.captionScroll.AddCSSClass("inset-panel")
+	page.Append(a.captionScroll)
+
+	provisional := gtk.NewBox(gtk.OrientationHorizontal, 8)
+	provisional.AddCSSClass("provisional-row")
+	caption := labelWithClass("LIVE", "live-tag")
+	caption.SetVAlign(gtk.AlignStart)
+	caption.SetMarginTop(2)
+	provisional.Append(caption)
+	a.provisionalLabel = gtk.NewLabel("Waiting for speech…")
+	a.provisionalLabel.SetXAlign(0)
+	a.provisionalLabel.SetWrap(true)
+	a.provisionalLabel.SetHExpand(true)
+	provisional.Append(a.provisionalLabel)
+	page.Append(provisional)
+
+	return page
+}
+
+func (a *Application) buildConsolePage() *gtk.Box {
+	page := gtk.NewBox(gtk.OrientationVertical, 7)
+	page.AddCSSClass("captioneer-content")
+
+	toolbar := gtk.NewBox(gtk.OrientationHorizontal, 5)
+	toolbar.AddCSSClass("toolbar")
+	toolbar.Append(labelWithClass("APPLICATION CONSOLE", "section-title"))
+	spacer := gtk.NewBox(gtk.OrientationHorizontal, 0)
+	spacer.SetHExpand(true)
+	toolbar.Append(spacer)
+	toolbar.Append(toolButton("Copy Selected", "Copy selected console output", func() {
+		copyBufferSelection(a.consoleBuffer)
+	}))
+	toolbar.Append(toolButton("Copy All", "Copy all buffered console output", func() {
+		copyBuffer(a.consoleBuffer)
+	}))
+	toolbar.Append(toolButton("Clear", "Clear the console display", func() {
+		a.log.Clear()
+		a.renderConsole()
+	}))
+	toolbar.Append(toolButton("Jump to Latest", "Resume at the newest message", func() {
+		scrollTextViewToEnd(a.consoleView, a.consoleScroll)
+	}))
+	page.Append(toolbar)
+
+	a.consoleBuffer = gtk.NewTextBuffer(nil)
+	a.consoleMetaTag = bufferTag(a.consoleBuffer, "meta", "#79826F")
+	a.consoleWarnTag = bufferTag(a.consoleBuffer, "warn", "#C79C4E")
+	a.consoleErrorTag = bufferTag(a.consoleBuffer, "error", "#CF826D")
+	a.consoleView = gtk.NewTextViewWithBuffer(a.consoleBuffer)
+	a.consoleView.SetEditable(false)
+	a.consoleView.SetCursorVisible(true)
+	a.consoleView.SetWrapMode(gtk.WrapWordChar)
+	a.consoleView.SetTopMargin(8)
+	a.consoleView.SetBottomMargin(8)
+	a.consoleView.SetLeftMargin(9)
+	a.consoleView.SetRightMargin(9)
+	a.consoleView.AddCSSClass("console-view")
+	a.consoleScroll = gtk.NewScrolledWindow()
+	a.consoleScroll.SetPolicy(gtk.PolicyAutomatic, gtk.PolicyAutomatic)
+	a.consoleScroll.SetHExpand(true)
+	a.consoleScroll.SetVExpand(true)
+	a.consoleScroll.SetChild(a.consoleView)
+	a.consoleScroll.AddCSSClass("inset-panel")
+	page.Append(a.consoleScroll)
+
+	return page
+}
+
+// tagSpan marks a character range of freshly rendered buffer text so a
+// TextTag can be applied after SetText replaces the whole buffer.
+type tagSpan struct {
+	tag        *gtk.TextTag
+	start, end int
+}
+
+func applyTagSpans(buffer *gtk.TextBuffer, spans []tagSpan) {
+	for _, span := range spans {
+		buffer.ApplyTag(span.tag, buffer.IterAtOffset(span.start), buffer.IterAtOffset(span.end))
+	}
+}
+
+func (a *Application) renderHistory(snapshot history.Snapshot) {
+	follow := isAtBottom(a.captionScroll)
+	var text strings.Builder
+	var spans []tagSpan
+	offset := 0
+	if len(snapshot.Finals) == 0 {
+		hint := "No captions yet. Press START to begin listening."
+		text.WriteString(hint)
+		spans = append(spans, tagSpan{a.captionHintTag, 0, utf8.RuneCountInString(hint)})
+	}
+	for _, entry := range snapshot.Finals {
+		meta := fmt.Sprintf("%s  [%s–%s]  ",
+			entry.CreatedAt.Format("15:04:05"),
+			formatCaptionTime(entry.StartedAt),
+			formatCaptionTime(entry.EndedAt),
+		)
+		text.WriteString(meta)
+		spans = append(spans, tagSpan{a.captionMetaTag, offset, offset + utf8.RuneCountInString(meta)})
+		offset += utf8.RuneCountInString(meta)
+		line := entry.Text + "\n"
+		text.WriteString(line)
+		offset += utf8.RuneCountInString(line)
+	}
+	a.captionBuffer.SetText(text.String())
+	applyTagSpans(a.captionBuffer, spans)
+	if snapshot.Provisional == nil || strings.TrimSpace(snapshot.Provisional.Text) == "" {
+		a.provisionalLabel.SetText("Waiting for speech…")
+	} else {
+		a.provisionalLabel.SetText(snapshot.Provisional.Text)
+	}
+	if follow {
+		scrollTextViewToEnd(a.captionView, a.captionScroll)
+	}
+}
+
+func (a *Application) renderConsole() {
+	follow := isAtBottom(a.consoleScroll)
+	var text strings.Builder
+	var spans []tagSpan
+	offset := 0
+	for _, entry := range a.log.Entries() {
+		var severityTag *gtk.TextTag
+		switch entry.Severity {
+		case diagnostics.Warning:
+			severityTag = a.consoleWarnTag
+		case diagnostics.Error:
+			severityTag = a.consoleErrorTag
+		}
+		meta := fmt.Sprintf("%s  %-7s  %-14s  ",
+			entry.At.Format("15:04:05.000"),
+			strings.ToUpper(string(entry.Severity)),
+			"["+entry.Category+"]",
+		)
+		text.WriteString(meta)
+		spans = append(spans, tagSpan{a.consoleMetaTag, offset, offset + utf8.RuneCountInString(meta)})
+		offset += utf8.RuneCountInString(meta)
+		line := entry.Message + "\n"
+		text.WriteString(line)
+		if severityTag != nil {
+			spans = append(spans, tagSpan{severityTag, offset, offset + utf8.RuneCountInString(entry.Message)})
+		}
+		offset += utf8.RuneCountInString(line)
+	}
+	a.consoleBuffer.SetText(text.String())
+	applyTagSpans(a.consoleBuffer, spans)
+	if follow {
+		scrollTextViewToEnd(a.consoleView, a.consoleScroll)
+	}
+}
+
+func formatCaptionTime(value time.Duration) string {
+	seconds := value.Seconds()
+	return fmt.Sprintf("%02d:%05.2f", int(seconds)/60, seconds-float64(int(seconds)/60*60))
+}
+
+func isAtBottom(scroll *gtk.ScrolledWindow) bool {
+	if scroll == nil {
+		return true
+	}
+	adjustment := scroll.VAdjustment()
+	return adjustment.Value()+adjustment.PageSize() >= adjustment.Upper()-4
+}
+
+func scrollTextViewToEnd(view *gtk.TextView, scroll *gtk.ScrolledWindow) {
+	if view == nil || scroll == nil {
+		return
+	}
+	view.ScrollToIter(view.Buffer().EndIter(), 0, false, 0, 1)
+	adjustment := scroll.VAdjustment()
+	adjustment.SetValue(adjustment.Upper())
+}
+
+func copyBufferSelection(buffer *gtk.TextBuffer) {
+	if buffer == nil {
+		return
+	}
+	start, end, ok := buffer.SelectionBounds()
+	if !ok {
+		return
+	}
+	gdk.DisplayGetDefault().Clipboard().SetText(buffer.Text(start, end, true))
+}
+
+func copyBuffer(buffer *gtk.TextBuffer) {
+	if buffer == nil {
+		return
+	}
+	start, end := buffer.Bounds()
+	gdk.DisplayGetDefault().Clipboard().SetText(buffer.Text(start, end, true))
+}
+
+func bufferTag(buffer *gtk.TextBuffer, name, foreground string) *gtk.TextTag {
+	tag := gtk.NewTextTag(name)
+	tag.SetObjectProperty("foreground", foreground)
+	buffer.TagTable().Add(tag)
+	return tag
+}
+
+func labelWithClass(text, class string) *gtk.Label {
+	label := gtk.NewLabel(text)
+	label.AddCSSClass(class)
+	label.SetXAlign(0)
+	return label
+}
+
+func toolButton(text, tooltip string, callback func()) *gtk.Button {
+	button := gtk.NewButtonWithLabel(text)
+	button.SetTooltipText(tooltip)
+	button.ConnectClicked(callback)
+	return button
+}

src/gui/platform_gtk.go

@@ -0,0 +1,84 @@
+//go:build gtk
+
+package gui
+
+/*
+#cgo pkg-config: gtk4 gtk4-x11 gtk4-wayland x11
+
+#include <gtk/gtk.h>
+#include <gdk/x11/gdkx.h>
+#include <gdk/wayland/gdkwayland.h>
+#include <X11/Xlib.h>
+#include <stdint.h>
+
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+
+// Returns 1 when the X11 hint was sent, 0 when the compositor controls this
+// policy (Wayland), and -1 for an unavailable/unknown backend.
+static int captioneer_set_main_window_above(GtkWindow *window, gboolean enabled) {
+	gtk_widget_realize(GTK_WIDGET(window));
+	GdkSurface *surface = gtk_native_get_surface(GTK_NATIVE(window));
+	if (surface == NULL) {
+		return -1;
+	}
+	if (GDK_IS_WAYLAND_SURFACE(surface)) {
+		return 0;
+	}
+	if (!GDK_IS_X11_SURFACE(surface)) {
+		return -1;
+	}
+
+	Display *display = GDK_SURFACE_XDISPLAY(surface);
+	Window xid = GDK_SURFACE_XID(surface);
+	Window root = DefaultRootWindow(display);
+	Atom state = XInternAtom(display, "_NET_WM_STATE", False);
+	Atom above = XInternAtom(display, "_NET_WM_STATE_ABOVE", False);
+	XEvent event = {0};
+	event.xclient.type = ClientMessage;
+	event.xclient.window = xid;
+	event.xclient.message_type = state;
+	event.xclient.format = 32;
+	event.xclient.data.l[0] = enabled ? 1 : 0;
+	event.xclient.data.l[1] = above;
+	event.xclient.data.l[2] = None;
+	event.xclient.data.l[3] = 1;
+	XSendEvent(display, root, False,
+		SubstructureRedirectMask | SubstructureNotifyMask, &event);
+	XFlush(display);
+	return 1;
+}
+
+static int captioneer_set_main_window_above_native(uintptr_t native, gboolean enabled) {
+	return captioneer_set_main_window_above((GtkWindow *)native, enabled);
+}
+*/
+import "C"
+
+import (
+	"github.com/diamondburned/gotk4/pkg/glib/v2"
+	"tea.chunkbyte.com/kato/captioneer/src/diagnostics"
+)
+
+func (a *Application) applyAlwaysOnTop(enabled bool) {
+	if a.window == nil {
+		return
+	}
+	glib.IdleAdd(func() {
+		result := int(C.captioneer_set_main_window_above_native(
+			C.uintptr_t(a.window.Native()),
+			C.gboolean(boolToInt(enabled)),
+		))
+		if enabled && result == 0 {
+			a.log.Add(diagnostics.Warning, "window", "Always on top is compositor-controlled on Wayland and could not be forced")
+		} else if enabled && result < 0 {
+			a.log.Add(diagnostics.Warning, "window", "Always on top is unavailable on this display backend")
+		}
+	})
+}
+
+func boolToInt(value bool) int {
+	if value {
+		return 1
+	}
+	return 0
+}

src/gui/settings.go

@@ -0,0 +1,470 @@
+//go:build gtk
+
+package gui
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/diamondburned/gotk4/pkg/gio/v2"
+	"github.com/diamondburned/gotk4/pkg/gtk/v4"
+	"tea.chunkbyte.com/kato/captioneer/src/app"
+	"tea.chunkbyte.com/kato/captioneer/src/config"
+	"tea.chunkbyte.com/kato/captioneer/src/diagnostics"
+)
+
+type settingsControls struct {
+	startCaptions *gtk.CheckButton
+	alwaysOnTop   *gtk.CheckButton
+
+	mode               *gtk.ComboBoxText
+	chunkDuration      *gtk.Entry
+	modelsDirectory    *gtk.Entry
+	threads            *gtk.SpinButton
+	previewThresholdDB *gtk.SpinButton
+	vadThreshold       *gtk.SpinButton
+
+	overlayEnabled      *gtk.CheckButton
+	historyEnabled      *gtk.CheckButton
+	stdoutEnabled       *gtk.CheckButton
+	stderrEnabled       *gtk.CheckButton
+	transcriptEnabled   *gtk.CheckButton
+	transcriptDirectory *gtk.Entry
+
+	overlayOpacity      *gtk.SpinButton
+	overlayFont         *gtk.FontButton
+	overlayFontSize     *gtk.SpinButton
+	overlayBottomMargin *gtk.SpinButton
+	overlayMaxWidth     *gtk.SpinButton
+	overlayMonitor      *gtk.Entry
+	overlayFinalTimeout *gtk.Entry
+	overlayClickThrough *gtk.CheckButton
+
+	overlayBackend       *gtk.ComboBoxText
+	modelAutoRestart     *gtk.CheckButton
+	modelTimeout         *gtk.Entry
+	modelShutdownTimeout *gtk.Entry
+}
+
+func (a *Application) buildSettingsPage() *gtk.Box {
+	page := gtk.NewBox(gtk.OrientationVertical, 7)
+	page.AddCSSClass("captioneer-content")
+
+	content := gtk.NewBox(gtk.OrientationHorizontal, 8)
+	content.SetHExpand(true)
+	content.SetVExpand(true)
+	settingsStack := gtk.NewStack()
+	settingsStack.SetTransitionType(gtk.StackTransitionTypeNone)
+	settingsStack.SetHExpand(true)
+	settingsStack.SetVExpand(true)
+	sidebar := gtk.NewStackSidebar()
+	sidebar.SetStack(settingsStack)
+	sidebar.SetSizeRequest(155, -1)
+	sidebar.AddCSSClass("settings-sidebar")
+	content.Append(sidebar)
+
+	a.createSettingsControls()
+	settingsStack.AddTitled(a.generalSettingsPage(), "general", "General")
+	settingsStack.AddTitled(a.recognitionSettingsPage(), "recognition", "Recognition")
+	settingsStack.AddTitled(a.outputSettingsPage(), "outputs", "Outputs")
+	settingsStack.AddTitled(a.overlaySettingsPage(), "overlay", "Caption Overlay")
+	settingsStack.AddTitled(a.advancedSettingsPage(), "advanced", "Advanced")
+	content.Append(settingsStack)
+	page.Append(content)
+
+	footer := gtk.NewBox(gtk.OrientationHorizontal, 7)
+	footer.AddCSSClass("toolbar")
+	a.settingsError = gtk.NewLabel("")
+	a.settingsError.SetXAlign(0)
+	a.settingsError.SetWrap(true)
+	a.settingsError.SetHExpand(true)
+	a.settingsError.AddCSSClass("validation-error")
+	footer.Append(a.settingsError)
+	reset := toolButton("Reset to Defaults", "Load defaults into the form without saving them", func() {
+		a.populateSettings(config.DefaultAppConfig())
+		a.updateApplyButton()
+	})
+	footer.Append(reset)
+	a.applyButton = gtk.NewButtonWithLabel("APPLY SETTINGS")
+	a.applyButton.AddCSSClass("primary-action")
+	a.applyButton.SetTooltipText("Validate and save all settings")
+	a.applyButton.ConnectClicked(a.applySettings)
+	footer.Append(a.applyButton)
+	page.Append(footer)
+
+	a.populateSettings(a.config)
+	a.connectSettingsChanged()
+	return page
+}
+
+func (a *Application) createSettingsControls() {
+	a.settings.startCaptions = gtk.NewCheckButton()
+	a.settings.alwaysOnTop = gtk.NewCheckButton()
+	a.settings.mode = combo([]option{{"vad", "Voice activity detection (VAD)"}, {"fixed", "Fixed chunks"}})
+	a.settings.chunkDuration = gtk.NewEntry()
+	a.settings.modelsDirectory = gtk.NewEntry()
+	a.settings.threads = spin(1, 128, 1, 0)
+	a.settings.previewThresholdDB = spin(-100, 0, 1, 1)
+	a.settings.vadThreshold = spin(0, 1, 0.01, 2)
+
+	a.settings.overlayEnabled = gtk.NewCheckButton()
+	a.settings.historyEnabled = gtk.NewCheckButton()
+	a.settings.stdoutEnabled = gtk.NewCheckButton()
+	a.settings.stderrEnabled = gtk.NewCheckButton()
+	a.settings.transcriptEnabled = gtk.NewCheckButton()
+	a.settings.transcriptDirectory = gtk.NewEntry()
+
+	a.settings.overlayOpacity = spin(0, 1, 0.01, 2)
+	a.settings.overlayFont = gtk.NewFontButton()
+	a.settings.overlayFont.SetUseFont(true)
+	a.settings.overlayFontSize = spin(8, 96, 1, 0)
+	a.settings.overlayBottomMargin = spin(0, 2000, 5, 0)
+	a.settings.overlayMaxWidth = spin(100, 5000, 10, 0)
+	a.settings.overlayMonitor = gtk.NewEntry()
+	a.settings.overlayFinalTimeout = gtk.NewEntry()
+	a.settings.overlayClickThrough = gtk.NewCheckButton()
+
+	a.settings.overlayBackend = combo([]option{{"auto", "Automatic"}, {"wayland", "Wayland"}, {"x11", "X11"}})
+	a.settings.modelAutoRestart = gtk.NewCheckButton()
+	a.settings.modelTimeout = gtk.NewEntry()
+	a.settings.modelShutdownTimeout = gtk.NewEntry()
+}
+
+func (a *Application) generalSettingsPage() *gtk.ScrolledWindow {
+	box := settingsBox("GENERAL", "Desktop startup and main-window behavior.")
+	box.Append(settingRow("Start captions when the GUI opens", "The saved setting is used unless an explicit command-line flag overrides it.", a.settings.startCaptions))
+	box.Append(settingRow("Keep main window above others", "Best effort on X11. Wayland compositors normally do not allow applications to force this.", a.settings.alwaysOnTop))
+	return settingsScroller(box)
+}
+
+func (a *Application) recognitionSettingsPage() *gtk.ScrolledWindow {
+	box := settingsBox("RECOGNITION", "These settings require the caption pipeline to restart while it is running.")
+	box.Append(settingRow("Processing mode", "VAD waits for detected speech; fixed mode recognizes regular chunks.", a.settings.mode))
+	box.Append(settingRow("Chunk / preview interval", "Go duration such as 1s or 750ms.", a.settings.chunkDuration))
+	box.Append(pathSettingRow(a, "Models directory", "Directory containing the Sherpa-ONNX model files.", a.settings.modelsDirectory, "Select models directory"))
+	box.Append(settingRow("Recognition threads", "CPU threads used by the recognizer.", a.settings.threads))
+	box.Append(settingRow("Preview threshold (dBFS)", "Suppress fixed-mode previews below this level.", a.settings.previewThresholdDB))
+	box.Append(settingRow("VAD threshold", "Speech detector sensitivity from 0.00 to 1.00.", a.settings.vadThreshold))
+	return settingsScroller(box)
+}
+
+func (a *Application) outputSettingsPage() *gtk.ScrolledWindow {
+	box := settingsBox("OUTPUTS", "Caption destinations and diagnostic output are independent.")
+	box.Append(settingRow("Caption overlay", "Show captions in the desktop overlay.", a.settings.overlayEnabled))
+	box.Append(settingRow("GUI caption history", "Keep final captions and one live provisional row in this window.", a.settings.historyEnabled))
+	box.Append(settingRow("Caption text on stdout", "Useful when launching the desktop application from a terminal or script.", a.settings.stdoutEnabled))
+	box.Append(settingRow("Diagnostics on stderr", "Mirror Console messages to the launching terminal.", a.settings.stderrEnabled))
+	box.Append(settingRow("Save timestamped caption log", "Write final captions to a dated session file, flushing each line immediately.", a.settings.transcriptEnabled))
+	box.Append(pathSettingRow(a, "Caption log directory", "A new session file is created here each time Captioneer starts logging.", a.settings.transcriptDirectory, "Select caption log directory"))
+	return settingsScroller(box)
+}
+
+func (a *Application) overlaySettingsPage() *gtk.ScrolledWindow {
+	box := settingsBox("CAPTION OVERLAY", "Appearance changes apply without restarting recognition.")
+	box.Append(settingRow("Opacity", "Background opacity from 0.00 to 1.00.", a.settings.overlayOpacity))
+	box.Append(settingRow("Font family", "Font used for overlay captions.", a.settings.overlayFont))
+	box.Append(settingRow("Font size", "Caption text size in points.", a.settings.overlayFontSize))
+	box.Append(settingRow("Bottom margin", "Distance from the bottom edge in pixels.", a.settings.overlayBottomMargin))
+	box.Append(settingRow("Maximum width", "Maximum overlay width in pixels.", a.settings.overlayMaxWidth))
+	box.Append(settingRow("Monitor", "Use auto or the configured monitor connector/name.", a.settings.overlayMonitor))
+	box.Append(settingRow("Final caption lifetime", "Zero keeps final text visible; otherwise use 3s or longer.", a.settings.overlayFinalTimeout))
+	box.Append(settingRow("Click through overlay", "Pass pointer input through empty areas. Hold Ctrl and drag the caption bubble to reposition it; the spot is remembered.", a.settings.overlayClickThrough))
+	return settingsScroller(box)
+}
+
+func (a *Application) advancedSettingsPage() *gtk.ScrolledWindow {
+	box := settingsBox("ADVANCED", "Low-level recovery and platform settings. Leave these at their defaults unless troubleshooting.")
+	expander := gtk.NewExpander("Show advanced settings")
+	expander.SetExpanded(false)
+	advanced := gtk.NewBox(gtk.OrientationVertical, 8)
+	advanced.SetMarginTop(8)
+	advanced.Append(settingRow("Overlay backend", "Changing the backend is saved now and takes effect after restarting the application.", a.settings.overlayBackend))
+	advanced.Append(settingRow("Restart model worker automatically", "Recover automatically if the isolated recognition worker crashes or stalls.", a.settings.modelAutoRestart))
+	advanced.Append(settingRow("Recognition timeout", "Maximum busy time before a stalled model worker is replaced; zero disables it.", a.settings.modelTimeout))
+	advanced.Append(settingRow("Worker shutdown timeout", "How long to wait for clean worker shutdown before forcing it.", a.settings.modelShutdownTimeout))
+	expander.SetChild(advanced)
+	box.Append(expander)
+	return settingsScroller(box)
+}
+
+func (a *Application) populateSettings(value config.AppConfig) {
+	a.settings.startCaptions.SetActive(value.GUI.StartCaptions)
+	a.settings.alwaysOnTop.SetActive(value.GUI.MainWindowAlwaysOnTop)
+	a.settings.mode.SetActiveID(string(value.Settings.Mode))
+	a.settings.chunkDuration.SetText(value.Settings.ChunkDuration.String())
+	a.settings.modelsDirectory.SetText(value.Settings.ModelsDir)
+	a.settings.threads.SetValue(float64(value.Settings.Threads))
+	a.settings.previewThresholdDB.SetValue(value.Settings.PreviewThresholdDB)
+	a.settings.vadThreshold.SetValue(value.Settings.VADThreshold)
+
+	a.settings.overlayEnabled.SetActive(value.Outputs.Overlay)
+	a.settings.historyEnabled.SetActive(value.Outputs.History)
+	a.settings.stdoutEnabled.SetActive(value.Outputs.StdoutCaptions)
+	a.settings.stderrEnabled.SetActive(value.Outputs.StderrDiagnostics)
+	a.settings.transcriptEnabled.SetActive(value.TranscriptLog.Enabled)
+	a.settings.transcriptDirectory.SetText(value.TranscriptLog.Directory)
+
+	a.settings.overlayOpacity.SetValue(value.Overlay.Opacity)
+	a.settings.overlayFont.SetFont(value.Overlay.FontFamily)
+	a.settings.overlayFontSize.SetValue(float64(value.Overlay.FontSize))
+	a.settings.overlayBottomMargin.SetValue(float64(value.Overlay.BottomMargin))
+	a.settings.overlayMaxWidth.SetValue(float64(value.Overlay.MaxWidth))
+	a.settings.overlayMonitor.SetText(value.Overlay.Monitor)
+	a.settings.overlayFinalTimeout.SetText(value.Overlay.FinalTimeout.String())
+	a.settings.overlayClickThrough.SetActive(value.Overlay.ClickThrough)
+
+	a.settings.overlayBackend.SetActiveID(string(value.Overlay.Backend))
+	a.settings.modelAutoRestart.SetActive(value.Settings.ModelAutoRestart)
+	a.settings.modelTimeout.SetText(value.Settings.ModelTimeout.String())
+	a.settings.modelShutdownTimeout.SetText(value.Settings.ModelShutdownTimeout.String())
+}
+
+func (a *Application) readSettings() (config.AppConfig, error) {
+	chunk, err := settingDuration("chunk / preview interval", a.settings.chunkDuration.Text())
+	if err != nil {
+		return config.AppConfig{}, err
+	}
+	finalTimeout, err := settingDuration("final caption lifetime", a.settings.overlayFinalTimeout.Text())
+	if err != nil {
+		return config.AppConfig{}, err
+	}
+	modelTimeout, err := settingDuration("recognition timeout", a.settings.modelTimeout.Text())
+	if err != nil {
+		return config.AppConfig{}, err
+	}
+	shutdownTimeout, err := settingDuration("worker shutdown timeout", a.settings.modelShutdownTimeout.Text())
+	if err != nil {
+		return config.AppConfig{}, err
+	}
+
+	next := config.AppConfig{
+		Version: config.CurrentConfigVersion,
+		GUI: config.GUISettings{
+			StartCaptions:         a.settings.startCaptions.Active(),
+			MainWindowAlwaysOnTop: a.settings.alwaysOnTop.Active(),
+		},
+		Settings: config.Settings{
+			Mode:                 config.Mode(a.settings.mode.ActiveID()),
+			ChunkDuration:        chunk,
+			ModelsDir:            strings.TrimSpace(a.settings.modelsDirectory.Text()),
+			Threads:              a.settings.threads.ValueAsInt(),
+			PreviewThresholdDB:   a.settings.previewThresholdDB.Value(),
+			VADThreshold:         a.settings.vadThreshold.Value(),
+			ModelAutoRestart:     a.settings.modelAutoRestart.Active(),
+			ModelTimeout:         modelTimeout,
+			ModelShutdownTimeout: shutdownTimeout,
+		},
+		Outputs: config.OutputSettings{
+			Overlay:           a.settings.overlayEnabled.Active(),
+			History:           a.settings.historyEnabled.Active(),
+			StdoutCaptions:    a.settings.stdoutEnabled.Active(),
+			StderrDiagnostics: a.settings.stderrEnabled.Active(),
+		},
+		Overlay: config.OverlaySettings{
+			Backend:      config.OverlayBackend(a.settings.overlayBackend.ActiveID()),
+			Opacity:      a.settings.overlayOpacity.Value(),
+			FontSize:     a.settings.overlayFontSize.ValueAsInt(),
+			FontFamily:   a.settings.overlayFont.FontDesc().Family(),
+			BottomMargin: a.settings.overlayBottomMargin.ValueAsInt(),
+			MaxWidth:     a.settings.overlayMaxWidth.ValueAsInt(),
+			Monitor:      strings.TrimSpace(a.settings.overlayMonitor.Text()),
+			FinalTimeout: finalTimeout,
+			ClickThrough: a.settings.overlayClickThrough.Active(),
+			PositionX:    a.config.Overlay.PositionX,
+			PositionY:    a.config.Overlay.PositionY,
+		},
+		TranscriptLog: config.TranscriptLogSettings{
+			Enabled:   a.settings.transcriptEnabled.Active(),
+			Directory: strings.TrimSpace(a.settings.transcriptDirectory.Text()),
+		},
+	}
+	if err := next.Validate(); err != nil {
+		return config.AppConfig{}, err
+	}
+	return next, nil
+}
+
+func (a *Application) applySettings() {
+	next, err := a.readSettings()
+	if err != nil {
+		a.settingsError.SetText(err.Error())
+		return
+	}
+	if err := config.Save(a.launch.Path, next); err != nil {
+		a.settingsError.SetText(err.Error())
+		a.log.Add(diagnostics.Error, "configuration", err.Error())
+		return
+	}
+
+	previous := a.applied
+	engineChanged := next.Settings != previous.Settings
+	backendChanged := next.Overlay.Backend != previous.Overlay.Backend
+	if err := a.configureOutputs(next, false); err != nil {
+		a.log.Add(diagnostics.Error, "outputs", err.Error())
+	}
+	a.config = next
+	a.applied = next
+	if backendChanged {
+		a.applied.Overlay.Backend = previous.Overlay.Backend
+		a.log.Add(diagnostics.Warning, "overlay", "Overlay backend change is saved and will apply after restarting Captioneer")
+	}
+	a.applyAlwaysOnTop(next.GUI.MainWindowAlwaysOnTop)
+	a.settingsError.SetText("")
+	a.log.Add(diagnostics.Info, "configuration", "Settings saved to "+a.launch.Path)
+
+	status := a.controller.Status()
+	if engineChanged && status.State != app.StateStopped && status.State != app.StateError {
+		go func(settings config.Settings) {
+			timeout := previous.Settings.ModelShutdownTimeout + 2*time.Second
+			ctx, cancel := context.WithTimeout(context.Background(), timeout)
+			defer cancel()
+			if err := a.controller.Restart(ctx, settings); err != nil {
+				a.log.Add(diagnostics.Error, "lifecycle", fmt.Sprintf("Apply and restart captions: %v", err))
+			}
+		}(next.Settings)
+	}
+	a.updateApplyButton()
+	a.renderStatus(a.controller.Status())
+}
+
+func (a *Application) updateApplyButton() {
+	if a.applyButton == nil {
+		return
+	}
+	next, err := a.readSettings()
+	if err != nil {
+		a.applyButton.SetLabel("APPLY SETTINGS")
+		return
+	}
+	status := a.controller.Status()
+	if next.Settings != a.applied.Settings && status.State != app.StateStopped && status.State != app.StateError {
+		a.applyButton.SetLabel("APPLY & RESTART CAPTIONS")
+	} else {
+		a.applyButton.SetLabel("APPLY SETTINGS")
+	}
+}
+
+func (a *Application) connectSettingsChanged() {
+	changed := a.updateApplyButton
+	entries := []*gtk.Entry{
+		a.settings.chunkDuration, a.settings.modelsDirectory, a.settings.transcriptDirectory,
+		a.settings.overlayMonitor, a.settings.overlayFinalTimeout, a.settings.modelTimeout,
+		a.settings.modelShutdownTimeout,
+	}
+	for _, entry := range entries {
+		entry.ConnectChanged(changed)
+	}
+	spins := []*gtk.SpinButton{
+		a.settings.threads, a.settings.previewThresholdDB, a.settings.vadThreshold,
+		a.settings.overlayOpacity, a.settings.overlayFontSize, a.settings.overlayBottomMargin,
+		a.settings.overlayMaxWidth,
+	}
+	for _, control := range spins {
+		control.ConnectValueChanged(changed)
+	}
+	combos := []*gtk.ComboBoxText{a.settings.mode, a.settings.overlayBackend}
+	for _, control := range combos {
+		control.ConnectChanged(changed)
+	}
+	a.settings.overlayFont.ConnectFontSet(changed)
+	checks := []*gtk.CheckButton{
+		a.settings.startCaptions, a.settings.alwaysOnTop, a.settings.overlayEnabled,
+		a.settings.historyEnabled, a.settings.stdoutEnabled, a.settings.stderrEnabled,
+		a.settings.transcriptEnabled, a.settings.overlayClickThrough, a.settings.modelAutoRestart,
+	}
+	for _, control := range checks {
+		control.ConnectToggled(changed)
+	}
+}
+
+type option struct{ id, label string }
+
+func combo(options []option) *gtk.ComboBoxText {
+	control := gtk.NewComboBoxText()
+	for _, option := range options {
+		control.Append(option.id, option.label)
+	}
+	return control
+}
+
+func spin(minimum, maximum, step float64, digits uint) *gtk.SpinButton {
+	control := gtk.NewSpinButtonWithRange(minimum, maximum, step)
+	control.SetDigits(digits)
+	control.SetNumeric(true)
+	return control
+}
+
+func settingsBox(title, description string) *gtk.Box {
+	box := gtk.NewBox(gtk.OrientationVertical, 8)
+	box.SetMarginTop(12)
+	box.SetMarginBottom(12)
+	box.SetMarginStart(12)
+	box.SetMarginEnd(12)
+	box.Append(labelWithClass(title, "section-title"))
+	intro := labelWithClass(description, "description")
+	intro.SetWrap(true)
+	box.Append(intro)
+	box.Append(gtk.NewSeparator(gtk.OrientationHorizontal))
+	return box
+}
+
+func settingsScroller(child gtk.Widgetter) *gtk.ScrolledWindow {
+	scroll := gtk.NewScrolledWindow()
+	scroll.SetPolicy(gtk.PolicyNever, gtk.PolicyAutomatic)
+	scroll.SetHExpand(true)
+	scroll.SetVExpand(true)
+	scroll.SetChild(child)
+	scroll.AddCSSClass("settings-panel")
+	return scroll
+}
+
+func settingRow(title, description string, control gtk.Widgetter) *gtk.Box {
+	row := gtk.NewBox(gtk.OrientationHorizontal, 12)
+	row.AddCSSClass("setting-row")
+	text := gtk.NewBox(gtk.OrientationVertical, 2)
+	text.SetHExpand(true)
+	name := gtk.NewLabel(title)
+	name.SetXAlign(0)
+	name.SetMnemonicWidget(control)
+	text.Append(name)
+	detail := labelWithClass(description, "description")
+	detail.SetWrap(true)
+	text.Append(detail)
+	row.Append(text)
+	widget := gtk.BaseWidget(control)
+	widget.SetVAlign(gtk.AlignCenter)
+	row.Append(control)
+	return row
+}
+
+func pathSettingRow(a *Application, title, description string, entry *gtk.Entry, dialogTitle string) *gtk.Box {
+	chooser := gtk.NewBox(gtk.OrientationHorizontal, 4)
+	entry.SetHExpand(true)
+	chooser.Append(entry)
+	browse := gtk.NewButtonWithLabel("Browse…")
+	browse.ConnectClicked(func() { a.selectFolder(dialogTitle, entry) })
+	chooser.Append(browse)
+	return settingRow(title, description, chooser)
+}
+
+func (a *Application) selectFolder(title string, entry *gtk.Entry) {
+	dialog := gtk.NewFileDialog()
+	dialog.SetTitle(title)
+	dialog.SelectFolder(context.Background(), &a.window.Window, func(result gio.AsyncResulter) {
+		folder, err := dialog.SelectFolderFinish(result)
+		if err != nil {
+			return
+		}
+		entry.SetText(folder.Path())
+	})
+}
+
+func settingDuration(name, value string) (time.Duration, error) {
+	duration, err := time.ParseDuration(strings.TrimSpace(value))
+	if err != nil {
+		return 0, fmt.Errorf("%s must be a duration such as 1s or 750ms", name)
+	}
+	return duration, nil
+}

src/gui/style.css

@@ -0,0 +1,537 @@
+/*
+ * Captioneer visual theme, modeled on the 2003-2005 Steam client:
+ * olive-gray raised chrome, sunken near-black wells, khaki/gold accents,
+ * 1px bevels (light top/left, dark bottom/right), no soft modern gradients.
+ *
+ * Palette:
+ *   chrome        #3E4637 (gradient stop #333A2D)
+ *   raised panel  #4C5844
+ *   sunken well   #1E221B
+ *   body text     #D8DED3   dim text #8A9384
+ *   khaki accent  #C4B550   selection #958831
+ *   error #B05C4A   warning #C79C4E
+ *   bevel light   #6A7862   bevel dark #242921
+ */
+
+window.captioneer-main {
+  background: #3E4637;
+  color: #D8DED3;
+  font-size: 9.5pt;
+}
+
+/* ------------------------------------------------------------------ */
+/* Titlebar chrome                                                     */
+/* ------------------------------------------------------------------ */
+
+headerbar.captioneer-header {
+  min-height: 34px;
+  padding: 2px 6px;
+  background-image: linear-gradient(to bottom, #454E3C, #333A2D);
+  border-bottom: 1px solid #242921;
+  box-shadow: inset 0 1px #6A7862;
+  color: #D8DED3;
+}
+
+headerbar.captioneer-header windowcontrols button {
+  min-height: 17px;
+  min-width: 19px;
+  padding: 1px 3px;
+  margin: 0 1px;
+  border-radius: 0;
+  background-image: none;
+  background: #4C5844;
+  border: 1px solid #242921;
+  border-top-color: #6A7862;
+  border-left-color: #6A7862;
+  color: #B9C2AD;
+  box-shadow: none;
+}
+
+headerbar.captioneer-header windowcontrols button:hover {
+  background: #5B684D;
+  color: #E8EDD8;
+}
+
+headerbar.captioneer-header windowcontrols button:active {
+  background: #333A2D;
+  border-top-color: #242921;
+  border-left-color: #242921;
+  border-bottom-color: #6A7862;
+  border-right-color: #6A7862;
+}
+
+.captioneer-brand {
+  color: #C4B550;
+  font-weight: 700;
+  font-size: 10pt;
+  letter-spacing: 2px;
+}
+
+.status-cell {
+  min-height: 20px;
+  padding: 1px 12px;
+  background: #2C3227;
+  border: 1px solid #242921;
+  border-bottom-color: #58644E;
+  border-right-color: #58644E;
+  border-radius: 1px;
+}
+
+.status-text {
+  color: #B9C2AD;
+  font-weight: 600;
+  font-size: 8.5pt;
+  letter-spacing: 1px;
+}
+
+.status-dot {
+  font-size: 11px;
+}
+
+.status-dot.status-running { color: #C4B550; }
+.status-dot.status-stopped { color: #79826F; }
+.status-dot.status-warning { color: #C79C4E; }
+.status-dot.status-error { color: #B05C4A; }
+
+/* ------------------------------------------------------------------ */
+/* Menu bar                                                            */
+/* ------------------------------------------------------------------ */
+
+.captioneer-menu {
+  min-height: 22px;
+  padding: 0 4px;
+  background: #3E4637;
+  border-bottom: 1px solid #242921;
+}
+
+.captioneer-menu > item {
+  padding: 2px 9px;
+  border-radius: 0;
+  color: #C3CBB6;
+}
+
+.captioneer-menu > item:hover,
+.captioneer-menu > item:selected {
+  background: #958831;
+  color: #1E221B;
+}
+
+popover.menu contents {
+  background: #3E4637;
+  border: 1px solid #242921;
+  border-top-color: #6A7862;
+  border-left-color: #6A7862;
+  border-radius: 0;
+  box-shadow: 2px 2px 0 rgba(0, 0, 0, 0.35);
+  color: #D8DED3;
+  padding: 2px;
+}
+
+popover.menu modelbutton {
+  min-height: 22px;
+  padding: 2px 10px;
+  border-radius: 0;
+  color: #D8DED3;
+}
+
+popover.menu modelbutton:hover {
+  background: #958831;
+  color: #1E221B;
+}
+
+/* ------------------------------------------------------------------ */
+/* Tab strip                                                           */
+/* ------------------------------------------------------------------ */
+
+.captioneer-tabs {
+  min-height: 27px;
+  padding: 5px 8px 0;
+  background: #383F30;
+  border-bottom: 1px solid #242921;
+}
+
+.captioneer-tabs button {
+  min-height: 22px;
+  padding: 3px 16px;
+  margin-right: 2px;
+  margin-bottom: -1px;
+  border-radius: 1px 1px 0 0;
+  background-image: none;
+  background: #434D3B;
+  border: 1px solid #242921;
+  border-top-color: #6A7862;
+  border-left-color: #6A7862;
+  color: #A8B29B;
+  font-size: 8.5pt;
+  font-weight: 600;
+  letter-spacing: 1px;
+  box-shadow: none;
+}
+
+.captioneer-tabs button:hover {
+  color: #D8DED3;
+  background: #4A553F;
+}
+
+.captioneer-tabs button:checked {
+  background: #4C5844;
+  color: #C4B550;
+  border-bottom-color: #4C5844;
+}
+
+.captioneer-content {
+  padding: 8px;
+  background: #4C5844;
+}
+
+/* ------------------------------------------------------------------ */
+/* Sunken wells and text views                                         */
+/* ------------------------------------------------------------------ */
+
+.inset-panel,
+textview,
+entry,
+spinbutton,
+combobox button.combo,
+fontbutton button {
+  background-image: none;
+  background: #1E221B;
+  color: #D8DED3;
+  border: 1px solid #191D16;
+  border-bottom-color: #6A7862;
+  border-right-color: #58644E;
+  border-radius: 1px;
+  box-shadow: none;
+}
+
+textview text {
+  background: #1E221B;
+  color: #D8DED3;
+}
+
+textview text selection {
+  background: #958831;
+  color: #1E221B;
+}
+
+.console-view text {
+  background: #191D16;
+  color: #B9C4AC;
+  font-family: Monospace;
+  font-size: 9pt;
+}
+
+.provisional-row {
+  min-height: 30px;
+  padding: 5px 8px;
+  background: #2C3227;
+  color: #D3DCBF;
+  border: 1px solid #191D16;
+  border-bottom-color: #58644E;
+  border-right-color: #58644E;
+  border-radius: 1px;
+}
+
+.live-tag {
+  padding: 1px 7px;
+  background: #958831;
+  color: #1E221B;
+  font-size: 7.5pt;
+  font-weight: 700;
+  letter-spacing: 1px;
+  border-radius: 1px;
+}
+
+/* ------------------------------------------------------------------ */
+/* Toolbars and buttons                                                */
+/* ------------------------------------------------------------------ */
+
+.toolbar {
+  min-height: 28px;
+  padding: 3px 5px;
+  background: #525E48;
+  border: 1px solid #242921;
+  border-top-color: #6A7862;
+  border-left-color: #6A7862;
+  border-radius: 1px;
+}
+
+button {
+  min-height: 21px;
+  min-width: 0;
+  padding: 2px 10px;
+  border-radius: 1px;
+  background-image: none;
+  background: #57634B;
+  color: #D8DED3;
+  font-size: 8.5pt;
+  font-weight: 600;
+  border: 1px solid #242921;
+  border-top-color: #6A7862;
+  border-left-color: #6A7862;
+  box-shadow: none;
+  text-shadow: none;
+}
+
+button:hover {
+  background: #63704F;
+  color: #EDF1DD;
+  border-top-color: #83917A;
+  border-left-color: #83917A;
+}
+
+button:active,
+button:checked {
+  background: #3A4233;
+  border-top-color: #242921;
+  border-left-color: #242921;
+  border-bottom-color: #6A7862;
+  border-right-color: #6A7862;
+}
+
+button:disabled,
+checkbutton:disabled,
+entry:disabled,
+spinbutton:disabled,
+combobox:disabled {
+  color: #79826F;
+  background: #414A38;
+}
+
+button:focus-visible,
+entry:focus-visible,
+spinbutton:focus-visible,
+combobox:focus-visible,
+checkbutton:focus-visible,
+textview:focus-visible {
+  outline: 1px dotted #C4B550;
+  outline-offset: -2px;
+}
+
+.primary-action {
+  color: #C4B550;
+  font-weight: 700;
+  letter-spacing: 1px;
+  border-top-color: #83917A;
+  border-left-color: #7E8C74;
+}
+
+.primary-action:hover {
+  color: #DED08A;
+}
+
+.danger-action {
+  color: #E0A18E;
+  font-weight: 700;
+  letter-spacing: 1px;
+}
+
+.danger-action:hover {
+  color: #F0BCAB;
+}
+
+/* ------------------------------------------------------------------ */
+/* Typography helpers                                                  */
+/* ------------------------------------------------------------------ */
+
+.section-title {
+  color: #C4B550;
+  font-size: 8.5pt;
+  font-weight: 700;
+  letter-spacing: 1px;
+}
+
+.description {
+  color: #8A9384;
+  font-size: 8.5pt;
+}
+
+.validation-error {
+  color: #D98D7A;
+  font-weight: 600;
+  font-size: 8.5pt;
+}
+
+.warning-text {
+  color: #C79C4E;
+}
+
+/* ------------------------------------------------------------------ */
+/* Statusbar                                                           */
+/* ------------------------------------------------------------------ */
+
+.statusbar {
+  min-height: 23px;
+  padding: 3px 6px;
+  background: #3E4637;
+  border-top: 1px solid #242921;
+  box-shadow: inset 0 1px #58644E;
+}
+
+.status-segment {
+  min-height: 17px;
+  padding: 0 9px;
+  background: #343B2D;
+  color: #98A28C;
+  font-size: 8.5pt;
+  border: 1px solid #242921;
+  border-bottom-color: #58644E;
+  border-right-color: #58644E;
+  border-radius: 1px;
+}
+
+/* ------------------------------------------------------------------ */
+/* Settings                                                            */
+/* ------------------------------------------------------------------ */
+
+.settings-sidebar {
+  background: #434D3B;
+  border: 1px solid #242921;
+  border-bottom-color: #58644E;
+  border-right-color: #58644E;
+}
+
+.settings-sidebar list {
+  background: #434D3B;
+}
+
+.settings-sidebar row {
+  min-width: 130px;
+  min-height: 24px;
+  padding: 4px 10px;
+  border-radius: 0;
+  color: #B4BEA6;
+  font-size: 9pt;
+}
+
+.settings-sidebar row:hover {
+  background: #4E5943;
+  color: #D8DED3;
+}
+
+.settings-sidebar row:selected {
+  background: #958831;
+  color: #1E221B;
+  font-weight: 700;
+}
+
+.settings-panel {
+  background: #46513D;
+  border: 1px solid #242921;
+  border-bottom-color: #58644E;
+  border-right-color: #58644E;
+}
+
+.setting-row {
+  min-height: 36px;
+  padding: 4px 8px;
+  background: #4E5A45;
+  border: 1px solid #3A4233;
+  border-top-color: #5C6950;
+  border-left-color: #5C6950;
+  border-radius: 1px;
+}
+
+/* ------------------------------------------------------------------ */
+/* Form controls                                                       */
+/* ------------------------------------------------------------------ */
+
+checkbutton check {
+  min-height: 13px;
+  min-width: 13px;
+  margin: 2px;
+  border-radius: 1px;
+  background-image: none;
+  background: #1E221B;
+  border: 1px solid #191D16;
+  border-bottom-color: #6A7862;
+  border-right-color: #58644E;
+  color: #C4B550;
+  box-shadow: none;
+  -gtk-icon-size: 11px;
+}
+
+checkbutton check:hover {
+  background: #262B22;
+}
+
+checkbutton check:checked {
+  background: #1E221B;
+  color: #C4B550;
+}
+
+entry,
+spinbutton {
+  min-height: 22px;
+  padding: 1px 6px;
+  caret-color: #C4B550;
+}
+
+entry selection,
+spinbutton selection {
+  background: #958831;
+  color: #1E221B;
+}
+
+spinbutton button {
+  min-height: 0;
+  min-width: 18px;
+  padding: 0 3px;
+  margin: 1px;
+  border-radius: 0;
+  background: #4C5844;
+  border: 1px solid #242921;
+  border-top-color: #6A7862;
+  border-left-color: #6A7862;
+}
+
+spinbutton button:hover {
+  background: #5B684D;
+}
+
+combobox button.combo,
+fontbutton button {
+  min-height: 22px;
+  padding: 1px 8px;
+  font-weight: 400;
+}
+
+combobox arrow {
+  color: #C4B550;
+  min-width: 14px;
+}
+
+/* ------------------------------------------------------------------ */
+/* Scrollbars                                                          */
+/* ------------------------------------------------------------------ */
+
+scrollbar {
+  background: #2C3227;
+  border: none;
+}
+
+scrollbar trough {
+  background: #2C3227;
+  border-radius: 0;
+}
+
+scrollbar slider {
+  min-width: 11px;
+  min-height: 24px;
+  margin: 1px;
+  border-radius: 1px;
+  background: #5C6850;
+  border: 1px solid #242921;
+  border-top-color: #6A7862;
+  border-left-color: #6A7862;
+}
+
+scrollbar slider:hover {
+  background: #68755A;
+}
+
+separator {
+  background: #242921;
+  min-height: 1px;
+  min-width: 1px;
+}

src/output/history/history.go

@@ -0,0 +1,164 @@
+// Package history retains a bounded in-memory caption transcript for the GUI.
+package history
+
+import (
+	"errors"
+	"strings"
+	"sync"
+	"time"
+
+	"tea.chunkbyte.com/kato/captioneer/src/captions"
+)
+
+type Entry struct {
+	CreatedAt time.Time
+	Text      string
+	StartedAt time.Duration
+	EndedAt   time.Duration
+}
+
+type Snapshot struct {
+	Finals      []Entry
+	Provisional *Entry
+}
+
+type Sink struct {
+	mu          sync.Mutex
+	capacity    int
+	enabled     bool
+	finals      []Entry
+	provisional *Entry
+	subscribers map[chan Snapshot]struct{}
+	closed      bool
+}
+
+func New(capacity int, enabled bool) *Sink {
+	if capacity < 1 {
+		capacity = 1
+	}
+	return &Sink{
+		capacity:    capacity,
+		enabled:     enabled,
+		subscribers: make(map[chan Snapshot]struct{}),
+	}
+}
+
+func (s *Sink) Publish(event captions.Event) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		return errors.New("caption history is closed")
+	}
+	if !s.enabled {
+		return nil
+	}
+	now := time.Now()
+	switch event.Kind {
+	case captions.Provisional:
+		s.provisional = &Entry{CreatedAt: now, Text: event.Text, StartedAt: event.StartedAt, EndedAt: event.EndedAt}
+	case captions.Final:
+		s.provisional = nil
+		s.finals = append(s.finals, Entry{CreatedAt: now, Text: event.Text, StartedAt: event.StartedAt, EndedAt: event.EndedAt})
+		if len(s.finals) > s.capacity {
+			s.finals = append([]Entry(nil), s.finals[len(s.finals)-s.capacity:]...)
+		}
+	case captions.Hide:
+		s.provisional = nil
+	}
+	s.publishLocked()
+	return nil
+}
+
+func (s *Sink) SetEnabled(enabled bool) {
+	s.mu.Lock()
+	s.enabled = enabled
+	if !enabled {
+		s.provisional = nil
+	}
+	s.publishLocked()
+	s.mu.Unlock()
+}
+
+func (s *Sink) Clear() {
+	s.mu.Lock()
+	s.finals = nil
+	s.provisional = nil
+	s.publishLocked()
+	s.mu.Unlock()
+}
+
+func (s *Sink) Snapshot() Snapshot {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.snapshotLocked()
+}
+
+func (s *Sink) Transcript() string {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	lines := make([]string, len(s.finals))
+	for index, entry := range s.finals {
+		lines[index] = entry.Text
+	}
+	return strings.Join(lines, "\n")
+}
+
+func (s *Sink) Subscribe(buffer int) (<-chan Snapshot, func()) {
+	if buffer < 1 {
+		buffer = 1
+	}
+	updates := make(chan Snapshot, buffer)
+	s.mu.Lock()
+	s.subscribers[updates] = struct{}{}
+	updates <- s.snapshotLocked()
+	s.mu.Unlock()
+	return updates, func() {
+		s.mu.Lock()
+		if _, ok := s.subscribers[updates]; ok {
+			delete(s.subscribers, updates)
+			close(updates)
+		}
+		s.mu.Unlock()
+	}
+}
+
+func (s *Sink) Close() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		return nil
+	}
+	s.closed = true
+	for subscriber := range s.subscribers {
+		close(subscriber)
+	}
+	s.subscribers = nil
+	return nil
+}
+
+func (s *Sink) snapshotLocked() Snapshot {
+	snapshot := Snapshot{Finals: append([]Entry(nil), s.finals...)}
+	if s.provisional != nil {
+		copy := *s.provisional
+		snapshot.Provisional = &copy
+	}
+	return snapshot
+}
+
+func (s *Sink) publishLocked() {
+	snapshot := s.snapshotLocked()
+	for subscriber := range s.subscribers {
+		select {
+		case subscriber <- snapshot:
+		default:
+			select {
+			case <-subscriber:
+			default:
+			}
+			select {
+			case subscriber <- snapshot:
+			default:
+			}
+		}
+	}
+}

src/output/history/history_test.go

@@ -0,0 +1,32 @@
+package history
+
+import (
+	"testing"
+
+	"tea.chunkbyte.com/kato/captioneer/src/captions"
+)
+
+func TestHistoryKeepsFinalsBoundedAndProvisionalSeparate(t *testing.T) {
+	sink := New(2, true)
+	_ = sink.Publish(captions.Event{Kind: captions.Provisional, Text: "draft"})
+	if sink.Snapshot().Provisional == nil {
+		t.Fatal("provisional caption was not retained")
+	}
+	for _, text := range []string{"one", "two", "three"} {
+		_ = sink.Publish(captions.Event{Kind: captions.Final, Text: text})
+	}
+	snapshot := sink.Snapshot()
+	if snapshot.Provisional != nil || len(snapshot.Finals) != 2 || snapshot.Finals[0].Text != "two" {
+		t.Fatalf("snapshot = %#v", snapshot)
+	}
+}
+
+func TestDisabledHistoryKeepsExistingFinalsButStopsRecording(t *testing.T) {
+	sink := New(10, true)
+	_ = sink.Publish(captions.Event{Kind: captions.Final, Text: "kept"})
+	sink.SetEnabled(false)
+	_ = sink.Publish(captions.Event{Kind: captions.Final, Text: "ignored"})
+	if got := sink.Transcript(); got != "kept" {
+		t.Fatalf("transcript = %q", got)
+	}
+}

src/output/overlay/overlay_gtk.go

@@ -4,8 +4,9 @@
 package overlay
 
 /*
-#cgo pkg-config: gtk4 gtk4-x11 gtk4-wayland gtk4-layer-shell-0
+#cgo pkg-config: gtk4-layer-shell-0
-#cgo LDFLAGS: -lX11
+#cgo pkg-config: gtk4 gtk4-x11 gtk4-wayland
+#cgo LDFLAGS: -Wl,--no-as-needed -lgtk4-layer-shell -lX11
 
 #include <gtk/gtk.h>
 #include <gtk4-layer-shell.h>
@@ -13,6 +14,7 @@ package overlay
 #include <gdk/wayland/gdkwayland.h>
 #include <X11/Xlib.h>
 #include <X11/Xatom.h>
+#include <X11/Xutil.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
@@ -31,6 +33,16 @@ typedef struct {
 	gboolean final_visible;
 	gboolean preview_visible;
 	gboolean x11;
+	gboolean layer_shell;
+	gboolean click_through;
+	gboolean dragging;
+	int bottom_margin;
+	int position_x;
+	int position_y;
+	double drag_start_px;
+	double drag_start_py;
+	int drag_origin_x;
+	int drag_origin_y;
 } CaptioneerOverlay;
 
 typedef struct {
@@ -39,6 +51,9 @@ typedef struct {
 	char *preview_text;
 } CaptioneerUpdate;
 
+// Implemented on the Go side via //export so drag placement can be persisted.
+extern void captioneerOverlayPositionChanged(int x, int y);
+
 static void captioneer_append_warning(GString *warnings, const char *message) {
 	if (warnings->len > 0) {
 		g_string_append(warnings, " ");
@@ -124,15 +139,198 @@ static GdkMonitor *captioneer_select_monitor(
 	return monitor;
 }
 
-static void captioneer_set_input_passthrough(CaptioneerOverlay *overlay, GString *warnings) {
+static GdkMonitor *captioneer_overlay_monitor(CaptioneerOverlay *overlay) {
-	if (!gdk_display_supports_input_shapes(gtk_widget_get_display(GTK_WIDGET(overlay->window)))) {
+	if (overlay->monitor != NULL) {
-		captioneer_append_warning(warnings, "This display backend does not support pointer click-through.");
+		return overlay->monitor;
+	}
+	GdkDisplay *display = gtk_widget_get_display(GTK_WIDGET(overlay->window));
+	GdkSurface *surface = gtk_native_get_surface(GTK_NATIVE(overlay->window));
+	if (surface != NULL) {
+		GdkMonitor *monitor = gdk_display_get_monitor_at_surface(display, surface);
+		if (monitor != NULL) {
+			return monitor;
+		}
+	}
+	return captioneer_monitor_by_index(display, 0);
+}
+
+static void captioneer_update_input_region(CaptioneerOverlay *overlay) {
+	GdkSurface *surface = gtk_native_get_surface(GTK_NATIVE(overlay->window));
+	if (surface == NULL) {
+		return;
+	}
+	if (!overlay->click_through || overlay->dragging) {
+		gdk_surface_set_input_region(surface, NULL);
+		return;
+	}
+	// Limit hit-testing to the caption bubble so the transparent full-width
+	// chrome stays click-through. CTRL+drag still works because clicks that
+	// land on the bubble include modifier state.
+	int bubble_width = gtk_widget_get_width(overlay->bubble);
+	int bubble_height = gtk_widget_get_height(overlay->bubble);
+	if (bubble_width <= 0 || bubble_height <= 0) {
+		cairo_region_t *empty = cairo_region_create();
+		gdk_surface_set_input_region(surface, empty);
+		cairo_region_destroy(empty);
+		return;
+	}
+	double native_x = 0, native_y = 0;
+	if (!gtk_widget_translate_coordinates(overlay->bubble, GTK_WIDGET(overlay->window), 0, 0, &native_x, &native_y)) {
+		native_x = 0;
+		native_y = 0;
+	}
+	cairo_rectangle_int_t rect = {
+		.x = (int)native_x,
+		.y = (int)native_y,
+		.width = bubble_width,
+		.height = bubble_height,
+	};
+	cairo_region_t *region = cairo_region_create_rectangle(&rect);
+	gdk_surface_set_input_region(surface, region);
+	cairo_region_destroy(region);
+}
+
+static void captioneer_apply_placement(CaptioneerOverlay *overlay) {
+	GdkSurface *surface = gtk_native_get_surface(GTK_NATIVE(overlay->window));
+	if (surface == NULL) {
+		return;
+	}
+	GdkMonitor *monitor = captioneer_overlay_monitor(overlay);
+	if (monitor == NULL) {
+		return;
+	}
+	GdkRectangle geometry;
+	gdk_monitor_get_geometry(monitor, &geometry);
+	int width = gdk_surface_get_width(surface);
+	int height = gdk_surface_get_height(surface);
+	if (width <= 1 || height <= 1) {
+		return;
+	}
+
+	int x = overlay->position_x;
+	int y = overlay->position_y;
+	if (x < 0) {
+		x = (geometry.width - width) / 2;
+	}
+	if (y < 0) {
+		y = geometry.height - height - overlay->bottom_margin;
+	}
+	if (x < 0) {
+		x = 0;
+	}
+	if (y < 0) {
+		y = 0;
+	}
+	if (x + width > geometry.width) {
+		x = MAX(0, geometry.width - width);
+	}
+	if (y + height > geometry.height) {
+		y = MAX(0, geometry.height - height);
+	}
+
+	if (overlay->layer_shell) {
+		gtk_layer_set_anchor(overlay->window, GTK_LAYER_SHELL_EDGE_LEFT, TRUE);
+		gtk_layer_set_anchor(overlay->window, GTK_LAYER_SHELL_EDGE_TOP, TRUE);
+		gtk_layer_set_anchor(overlay->window, GTK_LAYER_SHELL_EDGE_RIGHT, FALSE);
+		gtk_layer_set_anchor(overlay->window, GTK_LAYER_SHELL_EDGE_BOTTOM, FALSE);
+		gtk_layer_set_margin(overlay->window, GTK_LAYER_SHELL_EDGE_LEFT, x);
+		gtk_layer_set_margin(overlay->window, GTK_LAYER_SHELL_EDGE_TOP, y);
+		gtk_layer_set_margin(overlay->window, GTK_LAYER_SHELL_EDGE_RIGHT, 0);
+		gtk_layer_set_margin(overlay->window, GTK_LAYER_SHELL_EDGE_BOTTOM, 0);
+	} else if (overlay->x11) {
+		Display *display = GDK_SURFACE_XDISPLAY(surface);
+		Window xid = GDK_SURFACE_XID(surface);
+		int root_x = geometry.x + x;
+		int root_y = geometry.y + y;
+		XSizeHints *size_hints = XAllocSizeHints();
+		if (size_hints != NULL) {
+			size_hints->flags = USPosition | PPosition;
+			size_hints->x = root_x;
+			size_hints->y = root_y;
+			XSetWMNormalHints(display, xid, size_hints);
+			XFree(size_hints);
+		}
+		XMoveWindow(display, xid, root_x, root_y);
+		XFlush(display);
+	}
+	captioneer_update_input_region(overlay);
+}
+
+static gboolean captioneer_reposition_x11(gpointer data) {
+	captioneer_apply_placement(data);
+	return G_SOURCE_REMOVE;
+}
+
+static void captioneer_surface_size_changed(GObject *object, GParamSpec *spec, gpointer data) {
+	(void)object;
+	(void)spec;
+	g_idle_add(captioneer_reposition_x11, data);
+}
+
+static gboolean captioneer_ctrl_held(GdkEvent *event) {
+	return (gdk_event_get_modifier_state(event) & GDK_CONTROL_MASK) != 0;
+}
+
+static void captioneer_drag_begin(GtkGestureDrag *gesture, double x, double y, gpointer data) {
+	(void)x;
+	(void)y;
+	CaptioneerOverlay *overlay = data;
+	GdkEvent *event = gtk_event_controller_get_current_event(GTK_EVENT_CONTROLLER(gesture));
+	if (event == NULL || !captioneer_ctrl_held(event)) {
+		gtk_gesture_set_state(GTK_GESTURE(gesture), GTK_EVENT_SEQUENCE_DENIED);
 		return;
 	}
 	GdkSurface *surface = gtk_native_get_surface(GTK_NATIVE(overlay->window));
-	cairo_region_t *empty = cairo_region_create();
+	if (surface == NULL) {
-	gdk_surface_set_input_region(surface, empty);
+		gtk_gesture_set_state(GTK_GESTURE(gesture), GTK_EVENT_SEQUENCE_DENIED);
-	cairo_region_destroy(empty);
+		return;
+	}
+	overlay->dragging = TRUE;
+	captioneer_update_input_region(overlay);
+	gtk_gesture_set_state(GTK_GESTURE(gesture), GTK_EVENT_SEQUENCE_CLAIMED);
+
+	GdkMonitor *monitor = captioneer_overlay_monitor(overlay);
+	GdkRectangle geometry = {0};
+	if (monitor != NULL) {
+		gdk_monitor_get_geometry(monitor, &geometry);
+	}
+	int width = gdk_surface_get_width(surface);
+	int height = gdk_surface_get_height(surface);
+	int origin_x = overlay->position_x;
+	int origin_y = overlay->position_y;
+	if (origin_x < 0) {
+		origin_x = (geometry.width - width) / 2;
+	}
+	if (origin_y < 0) {
+		origin_y = geometry.height - height - overlay->bottom_margin;
+	}
+	overlay->drag_origin_x = origin_x;
+	overlay->drag_origin_y = origin_y;
+	gtk_gesture_drag_get_start_point(gesture, &overlay->drag_start_px, &overlay->drag_start_py);
+}
+
+static void captioneer_drag_update(GtkGestureDrag *gesture, double offset_x, double offset_y, gpointer data) {
+	CaptioneerOverlay *overlay = data;
+	if (!overlay->dragging) {
+		return;
+	}
+	(void)gesture;
+	overlay->position_x = overlay->drag_origin_x + (int)offset_x;
+	overlay->position_y = overlay->drag_origin_y + (int)offset_y;
+	captioneer_apply_placement(overlay);
+}
+
+static void captioneer_drag_end(GtkGestureDrag *gesture, double offset_x, double offset_y, gpointer data) {
+	(void)gesture;
+	CaptioneerOverlay *overlay = data;
+	if (!overlay->dragging) {
+		return;
+	}
+	overlay->position_x = overlay->drag_origin_x + (int)offset_x;
+	overlay->position_y = overlay->drag_origin_y + (int)offset_y;
+	overlay->dragging = FALSE;
+	captioneer_apply_placement(overlay);
+	captioneerOverlayPositionChanged(overlay->position_x, overlay->position_y);
 }
 
 static void captioneer_apply_x11_hints(CaptioneerOverlay *overlay) {
@@ -175,37 +373,11 @@ static void captioneer_apply_x11_hints(CaptioneerOverlay *overlay) {
 	XFlush(display);
 }
 
-static gboolean captioneer_reposition_x11(gpointer data) {
-	CaptioneerOverlay *overlay = data;
-	if (!overlay->x11 || overlay->monitor == NULL) {
-		return G_SOURCE_REMOVE;
-	}
-	GdkSurface *surface = gtk_native_get_surface(GTK_NATIVE(overlay->window));
-	if (surface == NULL) {
-		return G_SOURCE_REMOVE;
-	}
-	GdkRectangle geometry;
-	gdk_monitor_get_geometry(overlay->monitor, &geometry);
-	int width = gdk_surface_get_width(surface);
-	int height = gdk_surface_get_height(surface);
-	int bottom_margin = GPOINTER_TO_INT(g_object_get_data(G_OBJECT(overlay->window), "bottom-margin"));
-	int x = geometry.x + (geometry.width - width) / 2;
-	int y = geometry.y + geometry.height - height - bottom_margin;
-	XMoveWindow(GDK_SURFACE_XDISPLAY(surface), GDK_SURFACE_XID(surface), x, y);
-	return G_SOURCE_REMOVE;
-}
-
-static void captioneer_surface_size_changed(GObject *object, GParamSpec *spec, gpointer data) {
-	(void)object;
-	(void)spec;
-	g_idle_add(captioneer_reposition_x11, data);
-}
-
 static void captioneer_update_window_visibility(CaptioneerOverlay *overlay) {
 	gboolean visible = overlay->final_visible || overlay->preview_visible;
 	gtk_widget_set_visible(overlay->bubble, visible);
 	gtk_widget_set_visible(GTK_WIDGET(overlay->window), visible);
-	if (visible && overlay->x11) {
+	if (visible) {
 		g_idle_add(captioneer_reposition_x11, overlay);
 	}
 }
@@ -220,9 +392,7 @@ static gboolean captioneer_apply_update(gpointer data) {
 
 	overlay->preview_visible = update->preview_text[0] != '\0';
 	if (overlay->preview_visible) {
-		char *preview = g_strdup_printf("… %s", update->preview_text);
+		gtk_label_set_text(GTK_LABEL(overlay->preview_label), update->preview_text);
-		gtk_label_set_text(GTK_LABEL(overlay->preview_label), preview);
-		g_free(preview);
 	} else {
 		gtk_label_set_text(GTK_LABEL(overlay->preview_label), "");
 	}
@@ -271,12 +441,16 @@ static CaptioneerOverlay *captioneer_overlay_new(
 	int max_width,
 	const char *monitor_selection,
 	int click_through,
+	int position_x,
+	int position_y,
 	char **warning_message,
 	char **error_message
 ) {
 	*warning_message = NULL;
 	*error_message = NULL;
-	g_set_prgname("com.chunkbyte.captioneer.overlay");
+	if (g_get_prgname() == NULL) {
+		g_set_prgname("com.chunkbyte.captioneer.overlay");
+	}
 	if (g_strcmp0(backend, "auto") != 0) {
 		g_setenv("GDK_BACKEND", backend, TRUE);
 	}
@@ -297,6 +471,10 @@ static CaptioneerOverlay *captioneer_overlay_new(
 	CaptioneerOverlay *overlay = g_new0(CaptioneerOverlay, 1);
 	overlay->loop = g_main_loop_new(NULL, FALSE);
 	overlay->x11 = x11;
+	overlay->click_through = click_through != 0;
+	overlay->bottom_margin = bottom_margin;
+	overlay->position_x = position_x;
+	overlay->position_y = position_y;
 
 	char *monitor_error = NULL;
 	if (wayland && g_strcmp0(monitor_selection, "auto") == 0) {
@@ -318,15 +496,17 @@ static CaptioneerOverlay *captioneer_overlay_new(
 	gtk_window_set_resizable(overlay->window, FALSE);
 	gtk_widget_set_focusable(GTK_WIDGET(overlay->window), FALSE);
 	gtk_widget_add_css_class(GTK_WIDGET(overlay->window), "captioneer-overlay");
-	g_object_set_data(G_OBJECT(overlay->window), "bottom-margin", GINT_TO_POINTER(bottom_margin));
 	g_signal_connect(overlay->window, "close-request", G_CALLBACK(captioneer_window_close), overlay);
 
 	if (wayland && gtk_layer_is_supported()) {
+		overlay->layer_shell = TRUE;
 		gtk_layer_init_for_window(overlay->window);
 		gtk_layer_set_namespace(overlay->window, "captioneer");
 		gtk_layer_set_layer(overlay->window, GTK_LAYER_SHELL_LAYER_OVERLAY);
-		gtk_layer_set_anchor(overlay->window, GTK_LAYER_SHELL_EDGE_BOTTOM, TRUE);
+		// Pin with LEFT+TOP margins so placement is exact. Stretching LEFT+RIGHT
-		gtk_layer_set_margin(overlay->window, GTK_LAYER_SHELL_EDGE_BOTTOM, bottom_margin);
+		// made Plasma size the surface oddly and parked captions mid-screen.
+		gtk_layer_set_anchor(overlay->window, GTK_LAYER_SHELL_EDGE_LEFT, TRUE);
+		gtk_layer_set_anchor(overlay->window, GTK_LAYER_SHELL_EDGE_TOP, TRUE);
 		gtk_layer_set_exclusive_zone(overlay->window, 0);
 		gtk_layer_set_keyboard_mode(overlay->window, GTK_LAYER_SHELL_KEYBOARD_MODE_NONE);
 		if (overlay->monitor != NULL) {
@@ -334,7 +514,7 @@ static CaptioneerOverlay *captioneer_overlay_new(
 		}
 	} else if (wayland) {
 		captioneer_append_warning(warnings,
-			"The Wayland compositor does not support Layer Shell; using a normal window without guaranteed always-on-top, placement, taskbar, or fullscreen behavior.");
+			"Layer Shell is unavailable in this process (often a libwayland load-order problem); using a normal window without guaranteed always-on-top or placement. Try rebuilding so libgtk4-layer-shell loads before libwayland-client, or set overlay backend to x11.");
 	}
 
 	GdkMonitor *size_monitor = overlay->monitor;
@@ -361,6 +541,9 @@ static CaptioneerOverlay *captioneer_overlay_new(
 	overlay->bubble = box;
 	gtk_widget_add_css_class(box, "captioneer-bubble");
 	gtk_widget_set_halign(box, GTK_ALIGN_CENTER);
+	gtk_widget_set_valign(box, GTK_ALIGN_START);
+	gtk_widget_set_hexpand(box, FALSE);
+	gtk_widget_set_vexpand(box, FALSE);
 	gtk_widget_set_size_request(box, effective_width, -1);
 
 	overlay->final_label = gtk_label_new("");
@@ -391,6 +574,14 @@ static CaptioneerOverlay *captioneer_overlay_new(
 	gtk_widget_add_css_class(overlay->preview_label, "captioneer-preview");
 	gtk_window_set_child(overlay->window, box);
 
+	GtkGesture *drag = gtk_gesture_drag_new();
+	gtk_gesture_single_set_button(GTK_GESTURE_SINGLE(drag), GDK_BUTTON_PRIMARY);
+	gtk_event_controller_set_propagation_phase(GTK_EVENT_CONTROLLER(drag), GTK_PHASE_CAPTURE);
+	g_signal_connect(drag, "drag-begin", G_CALLBACK(captioneer_drag_begin), overlay);
+	g_signal_connect(drag, "drag-update", G_CALLBACK(captioneer_drag_update), overlay);
+	g_signal_connect(drag, "drag-end", G_CALLBACK(captioneer_drag_end), overlay);
+	gtk_widget_add_controller(overlay->bubble, GTK_EVENT_CONTROLLER(drag));
+
 	char *font_family_rule = captioneer_font_family_rule(font_family);
 	char *css = g_strdup_printf(
 		"window.captioneer-overlay { background-color: transparent; box-shadow: none; }"
@@ -407,15 +598,20 @@ static CaptioneerOverlay *captioneer_overlay_new(
 
 	gtk_widget_realize(GTK_WIDGET(overlay->window));
 	GdkSurface *surface = gtk_native_get_surface(GTK_NATIVE(overlay->window));
-	if (click_through) {
+	if (overlay->click_through) {
-		captioneer_set_input_passthrough(overlay, warnings);
+		if (!gdk_display_supports_input_shapes(display)) {
+			captioneer_append_warning(warnings, "This display backend does not support pointer click-through.");
+		} else {
+			captioneer_update_input_region(overlay);
+		}
 	}
 	if (x11) {
 		captioneer_apply_x11_hints(overlay);
-		g_signal_connect(surface, "notify::width", G_CALLBACK(captioneer_surface_size_changed), overlay);
-		g_signal_connect(surface, "notify::height", G_CALLBACK(captioneer_surface_size_changed), overlay);
 	}
+	g_signal_connect(surface, "notify::width", G_CALLBACK(captioneer_surface_size_changed), overlay);
+	g_signal_connect(surface, "notify::height", G_CALLBACK(captioneer_surface_size_changed), overlay);
 	gtk_widget_set_visible(GTK_WIDGET(overlay->window), FALSE);
+	captioneer_apply_placement(overlay);
 
 	if (warnings->len > 0) {
 		*warning_message = g_string_free(warnings, FALSE);
@@ -490,6 +686,28 @@ type Sink struct {
 	closed         bool
 }
 
+var (
+	positionSaverMu sync.Mutex
+	positionSaver   func(x, y int)
+)
+
+// SetPositionSaver registers a callback invoked when the user finishes a CTRL-drag.
+func SetPositionSaver(save func(x, y int)) {
+	positionSaverMu.Lock()
+	positionSaver = save
+	positionSaverMu.Unlock()
+}
+
+//export captioneerOverlayPositionChanged
+func captioneerOverlayPositionChanged(x, y C.int) {
+	positionSaverMu.Lock()
+	save := positionSaver
+	positionSaverMu.Unlock()
+	if save != nil {
+		save(int(x), int(y))
+	}
+}
+
 func New(settings config.OverlaySettings) (*Sink, string, error) {
 	backend := C.CString(string(settings.Backend))
 	fontFamily := C.CString(settings.FontFamily)
@@ -509,6 +727,8 @@ func New(settings config.OverlaySettings) (*Sink, string, error) {
 		C.int(settings.MaxWidth),
 		monitor,
 		boolInt(settings.ClickThrough),
+		C.int(settings.PositionX),
+		C.int(settings.PositionY),
 		&warningMessage,
 		&errorMessage,
 	)

src/output/router.go

@@ -0,0 +1,86 @@
+package output
+
+import (
+	"errors"
+	"sort"
+	"sync"
+
+	"tea.chunkbyte.com/kato/captioneer/src/captions"
+)
+
+type Router struct {
+	mu     sync.RWMutex
+	sinks  map[string]Sink
+	closed bool
+}
+
+func NewRouter() *Router {
+	return &Router{sinks: make(map[string]Sink)}
+}
+
+func (r *Router) Set(name string, sink Sink) error {
+	r.mu.Lock()
+	if r.closed {
+		r.mu.Unlock()
+		if sink != nil {
+			_ = sink.Close()
+		}
+		return errors.New("output router is closed")
+	}
+	previous := r.sinks[name]
+	if sink == nil {
+		delete(r.sinks, name)
+	} else {
+		r.sinks[name] = sink
+	}
+	r.mu.Unlock()
+	if previous != nil && previous != sink {
+		return previous.Close()
+	}
+	return nil
+}
+
+func (r *Router) Remove(name string) error {
+	return r.Set(name, nil)
+}
+
+func (r *Router) Publish(event captions.Event) error {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	names := make([]string, 0, len(r.sinks))
+	for name := range r.sinks {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	var publishErr error
+	for _, name := range names {
+		publishErr = errors.Join(publishErr, r.sinks[name].Publish(event))
+	}
+	return publishErr
+}
+
+func (r *Router) Close() error {
+	r.mu.Lock()
+	if r.closed {
+		r.mu.Unlock()
+		return nil
+	}
+	r.closed = true
+	names := make([]string, 0, len(r.sinks))
+	for name := range r.sinks {
+		names = append(names, name)
+	}
+	sort.Sort(sort.Reverse(sort.StringSlice(names)))
+	sinks := make([]Sink, 0, len(names))
+	for _, name := range names {
+		sinks = append(sinks, r.sinks[name])
+	}
+	r.sinks = nil
+	r.mu.Unlock()
+
+	var closeErr error
+	for _, sink := range sinks {
+		closeErr = errors.Join(closeErr, sink.Close())
+	}
+	return closeErr
+}

src/output/sink_test.go

@@ -47,3 +47,33 @@ func TestMultiSinkStillPublishesToOtherSinksAfterError(t *testing.T) {
 		t.Fatalf("unexpected result: err=%v second=%d", err, len(second.events))
 	}
 }
+
+func TestRouterCanReplaceAndRemoveOutputsWhileRunning(t *testing.T) {
+	router := NewRouter()
+	first := &recordingSink{}
+	second := &recordingSink{}
+	if err := router.Set("history", first); err != nil {
+		t.Fatal(err)
+	}
+	if err := router.Publish(captions.Event{Kind: captions.Final, Text: "first"}); err != nil {
+		t.Fatal(err)
+	}
+	if err := router.Set("history", second); err != nil {
+		t.Fatal(err)
+	}
+	if !first.closed {
+		t.Fatal("replaced sink was not closed")
+	}
+	if err := router.Publish(captions.Event{Kind: captions.Final, Text: "second"}); err != nil {
+		t.Fatal(err)
+	}
+	if len(first.events) != 1 || len(second.events) != 1 {
+		t.Fatalf("unexpected routed events: first=%d second=%d", len(first.events), len(second.events))
+	}
+	if err := router.Remove("history"); err != nil {
+		t.Fatal(err)
+	}
+	if !second.closed {
+		t.Fatal("removed sink was not closed")
+	}
+}

src/output/transcript/transcript.go

@@ -0,0 +1,102 @@
+// Package transcript writes finalized captions to timestamped session logs.
+package transcript
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+
+	"tea.chunkbyte.com/kato/captioneer/src/captions"
+)
+
+type Sink struct {
+	mu     sync.Mutex
+	file   *os.File
+	writer *bufio.Writer
+	now    func() time.Time
+	closed bool
+	path   string
+}
+
+func New(directory string) (*Sink, error) {
+	return newWithClock(directory, time.Now)
+}
+
+func newWithClock(directory string, now func() time.Time) (*Sink, error) {
+	if strings.TrimSpace(directory) == "" {
+		return nil, errors.New("transcript directory cannot be empty")
+	}
+	if err := os.MkdirAll(directory, 0o700); err != nil {
+		return nil, fmt.Errorf("create transcript directory: %w", err)
+	}
+	startedAt := now()
+	base := "captioneer-" + startedAt.Format("2006-01-02_15-04-05.000")
+	var file *os.File
+	var path string
+	for suffix := 0; suffix < 1000; suffix++ {
+		name := base + ".log"
+		if suffix > 0 {
+			name = fmt.Sprintf("%s-%d.log", base, suffix)
+		}
+		path = filepath.Join(directory, name)
+		candidate, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o600)
+		if errors.Is(err, os.ErrExist) {
+			continue
+		}
+		if err != nil {
+			return nil, fmt.Errorf("create transcript: %w", err)
+		}
+		file = candidate
+		break
+	}
+	if file == nil {
+		return nil, errors.New("create transcript: too many files share this timestamp")
+	}
+	return &Sink{file: file, writer: bufio.NewWriter(file), now: now, path: path}, nil
+}
+
+func (s *Sink) Path() string {
+	return s.path
+}
+
+func (s *Sink) Publish(event captions.Event) error {
+	if event.Kind != captions.Final {
+		return nil
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		return errors.New("transcript is closed")
+	}
+	text := strings.Join(strings.Fields(event.Text), " ")
+	if text == "" {
+		return nil
+	}
+	_, err := fmt.Fprintf(
+		s.writer,
+		"%s [%.2fs-%.2fs] %s\n",
+		s.now().Format(time.RFC3339Nano),
+		event.StartedAt.Seconds(),
+		event.EndedAt.Seconds(),
+		text,
+	)
+	if err != nil {
+		return err
+	}
+	return s.writer.Flush()
+}
+
+func (s *Sink) Close() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		return nil
+	}
+	s.closed = true
+	return errors.Join(s.writer.Flush(), s.file.Close())
+}

src/output/transcript/transcript_test.go

@@ -0,0 +1,40 @@
+package transcript
+
+import (
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	"tea.chunkbyte.com/kato/captioneer/src/captions"
+)
+
+func TestTranscriptWritesOnlyFinalCaptionsWithWallClockAndOffsets(t *testing.T) {
+	now := time.Date(2026, 7, 17, 12, 34, 56, 123000000, time.UTC)
+	sink, err := newWithClock(t.TempDir(), func() time.Time { return now })
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := sink.Publish(captions.Event{Kind: captions.Provisional, Text: "draft"}); err != nil {
+		t.Fatal(err)
+	}
+	if err := sink.Publish(captions.Event{
+		Kind: captions.Final, Text: "hello\nthere", StartedAt: time.Second, EndedAt: 2500 * time.Millisecond,
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if err := sink.Close(); err != nil {
+		t.Fatal(err)
+	}
+	data, err := os.ReadFile(sink.Path())
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "2026-07-17T12:34:56.123Z [1.00s-2.50s] hello there\n"
+	if string(data) != want {
+		t.Fatalf("transcript = %q, want %q", data, want)
+	}
+	if !strings.Contains(sink.Path(), "captioneer-2026-07-17_12-34-56.123.log") {
+		t.Fatalf("unexpected transcript path %q", sink.Path())
+	}
+}