CST-agent/app/README.md

# app/ — the Qt front end

CST-agent's GUI: **Qt 6 + QML + the C engine, in one process**. No HTTP
server, no port, no token, no second process — the app creates a `cst_agent_t`
directly and drives it through `cst_agent.h`.

```
app/                         the GUI
  src/main.cpp               entry point, --workspace / --selftest
  src/core/AgentCore.*       QObject around cst_agent_t: turns, hooks, consent
  src/core/ToolProvider.h    how the front end hands tools to the engine
  src/platform/<os>/         platform tools the app implements itself
  qml/Main.qml               the window (chat, tool runs, consent dialog)
  tools/selftest.c           C smoke test of the embedding path (no Qt)
```

## Build

```sh
# engine + GUI + C smoke test
cmake -S app -B build-app -DCMAKE_BUILD_TYPE=Debug
cmake --build build-app -j
QT_QPA_PLATFORM=offscreen ctest --test-dir build-app   # cst-app-selftest

# the app alone
./build-app/cst-agent-app --workspace ~/notes
./build-app/cst-agent-app --size 480x900    # the narrow (drawer) layout
./build-app/cst-agent-app --uitest          # drive the window, exit code = failures
./build-app/cst-agent-app --selftest        # same checks as the C test
```

The standalone build is the supported one: `app/CMakeLists.txt` uses the
`cstcore` target when the parent project defines one, and otherwise builds
the engine itself from `../src` (TUI, `main.c` and the HTTP front end
excluded). Wiring it into the repository's `CMakeLists.txt` as
`-DCST_APP=ON` is on the list below.

Needs Qt 6.4+ with **Quick / Qml / QuickControls2** (`qt6.qtdeclarative`,
`qt6.qtquickcontrols2` on Nix; the online installer's "Qt 6.x Desktop" on
Windows/macOS). Without them the configure step warns and builds only the C
smoke test — that is deliberate: the embedding path stays verifiable
everywhere. Kirigami is not required yet; `qml/Main.qml` uses Qt Quick
Controls and keeps the layout in Kirigami's shape (single column, cards,
navigation drawer) so swapping in `org.kde.kirigami` later is a QML-only
change. Point the app at a Kirigami outside the Qt prefix with
`-DCST_APP_QML_IMPORT=/path/to/qml`.

## Install (Linux desktop)

The window installs itself: the binary, a launcher entry and the icon the
launcher draws for it. All three are one CMake component (`app`), so the CLI
keeps coming from `scripts/bootstrap_linux.sh` and the profile never holds two
`cst-agent` of different vintages; the files live in `app/linux/`.

```sh
# NixOS / nix users: PATH + menu entry + icon. The Qt apps hook bakes the
# plugin and QML module paths into the wrapper, so the app runs outside a
# nix-shell and nix-collect-garbage cannot pull Qt out from under it.
nix-build                       # ./result/bin/cst-agent-app, run it in place
nix profile add --file .        # or: ./result/bin/cst-agent-app
nix profile remove cst-agent    # uninstall

# anywhere with Qt 6 (Quick/Qml/QuickControls2) and libcurl:
cmake -B build-app -DCST_BUILD_APP=ON -DCMAKE_BUILD_TYPE=Release
cmake --build build-app -j
cmake --install build-app --component app --prefix ~/.local
```

Launched from a menu, the workspace is the directory the app starts in
(`$HOME` there), so sessions land in `~/.agent/sessions`; pass
`--workspace <dir>` to pin another one.

## Why in one process

The engine is a library, not a daemon: `libcstcore.a` (Makefile) / the
`cstcore` target (CMake). The app owns one `cst_agent_t` per window, so
there is no protocol to version, no socket to authenticate and no second
process to babysit — and the CLI, TUI and WebUI keep working off the same
source.

- `AgentCore::send()` runs `cst_agent_run_turn_ex()` on a worker thread;
  the `cst_agent_hooks_t` callbacks turn into Qt signals (assistant deltas,
  tool events, tool results, todo, turn end).
- Consent is a blocking hook: the worker waits on a `QWaitCondition`, the
  GUI answers, the turn goes on. `CST_PERM_DENY / ONCE / ALWAYS_TOOL /
  ALWAYS_PREFIX` map 1:1 onto the buttons, and `ALWAYS_*` still lands in
  `.agent/permissions.json`, so a desktop decision is visible to the TUI.
- `cancel()` is `cst_agent_request_cancel()`; the turn unwinds as a normal
  result, not an exception.

## Layout and input

One shell, three sizes (everything is styled from `qml/Theme.qml`):

- **Desktop**: the sidebar is docked and its divider can be dragged (double
  click restores the auto width). Hover states, tooltips, selectable text and
  a wheel-scrolled transcript.
- **Narrow window** (below `Theme.compactBreakpoint`, 880 px): the sidebar
  folds away, the header grows a `☰` button, and the settings slide in over
  the transcript with a scrim; the sidebar itself scrolls, because a phone
  window cannot show it all.
- **Touch**: controls keep a `Theme.touchTarget` (34 px) hit area, buttons do
  not depend on hover, the composer asks the platform keyboard not to
  autocorrect (`ImhNoPredictiveText`), and Enter/Shift+Enter still behave.

`--uitest` checks this without a human: it loads the window, clicks with
synthesized **mouse** events, taps with a synthesized **touch** device, types
into the composer, drives the session list, then narrows the window to 460 px
to assert the dock → drawer switch and opens/closes the drawer. One line per
check, non-zero exit on failure:

```sh
QT_QPA_PLATFORM=offscreen ./build-app/cst-agent-app --uitest
# ok   wide window: sidebar docked
# ok   mouse click on "general" reaches the engine
# ok   touch tap on "coding" reaches the engine
# ...
```

## Sessions

A GUI session is a directory in the workspace's store
(`.agent/sessions/<id>/session.jsonl`, with its `title`, its `attachments/` and
its sub-agent transcripts beside it), the same one the CLI, the TUI and the
WebUI use — `AgentCore::open()` resolves the workspace's current session before
the engine starts, so nothing is written next to the process's working
directory. A store an older version wrote (flat `<id>.jsonl` files) still
reads; `cst-agent --migrate-store` moves it in.

- The sidebar lists the store (newest first): title or first prompt, message
  count, "3h ago"; the open one is highlighted. `+ new` starts a session, `×`
  deletes one (the engine first moves off a session it has open, so it never
  sits on a file that is gone), and a click switches.
- Switching **replays** the transcript: `AgentCore::history()` walks the stored
  messages and returns the same rows the live signals build — messages,
  thoughts, notes, and one card per tool call, with its result paired by name
  (a call with no result keeps state `unfinished`, so no spinner runs
  forever). A reopened session therefore renders like the turn that wrote it.
- Session controls are disabled while a turn runs: switching would move the
  engine out from under it.

`--uitest` covers the flow end to end: `writeFixtureSession()` writes a small
session through the store API (a tool call with its result), the checks click
its row, assert the five replayed rows and the paired result, start two new
sessions (the view empties), delete one by its `×` (the open one stays), and
switch back.

`--uitest` uses a scratch workspace unless `--workspace` is given, since it
creates and deletes sessions. On a machine without a screen,
`CST_APP_SHOT=shot.png` makes the run save the window as a PNG when it is
done; `CST_APP_DUMP=1` prints how many session rows the visual tree holds.

Every line the run prints also goes to `uitest.log` in the workspace, and the
verdict is the last line of it. That is how a run *on a phone* is read back:
stdout reaches nobody there, an app started from adb cannot be handed
environment variables, and logcat does not carry this build's Qt messages --
so `--uitest --workspace /sdcard/cst-uitest` plus
`adb pull /sdcard/cst-uitest/uitest.log` is the whole round trip.

## Provider, model, key

The sidebar shows where the engine points (`provider · model`); the gear in the
header opens the dialog that changes it.

- The provider list is the engine's own preset table (`cst_provider_count()`),
  with each entry's base URL and where its key would come from: "key saved"
  (`.agent`-independent, `<config>/cst-agent/credentials`), "key from
  OPENAI_API_KEY", or "no key". A key itself is never sent to the QML side —
  the dialog only ever describes it. The window starts the engine without a
  key (`AgentCore::open()` is passed an empty one), so `open()` resolves it
  for the provider it starts on: saved key, then the provider's env variable,
  then `CST_API_KEY` — the same order the CLI uses in `main.c`. Without that
  the key sat in the file but never in the turn, and every start asked for it
  again.
- "Use this" calls `AgentCore::useProvider()`, which runs
  `cst_ps_switch_provider()` / `cst_ps_set_key()` on the engine's live config:
  a pasted key is verified against the provider's `/models` before it is saved
  (offline it is kept unverified and the header says so), the model is
  remembered in `settings.json`, and the **session is not touched**. Model
  candidates come from the provider entry, the fetched cache
  (`cst_ps_cached`, no network) and the remembered pick; the label next to the
  field is `cst_model_info` ("200K · text only").
- The dialog also reports the session's token use (`cst_agent_usage`).

`--uitest` checks it end to end: the presets are readable, an unknown provider
is refused, the gear opens the panel, the provider rows exist, a model typed
into the field reaches the engine when "Use this" is clicked, the note says so,
and Close puts the dialog away. The run points `XDG_CONFIG_HOME` at its scratch
directory, so settings and keys of the real user are never rewritten.

## Custom providers, model parameters

The dialog's **Advanced options** covers the two things the presets cannot:
a provider of your own, and what the model should do.

- A custom provider is an entry the engine keeps in
  `<config>/cst-agent/models.json` (layer 1 of the model registry, see
  `include/cst_models.h`) — the same file a hand-written override would go
  into, so the GUI and a text editor are interchangeable:

  ```json
  { "providers": { "myllm": { "api_base": "https://api.example.com/v1",
                              "key_env": "MYLLM_API_KEY",
                              "default_model": "m1",
                              "models": ["m1", "m2"] } } }
  ```

  `AgentCore::addProvider()` / `removeProvider()` write it
  (`cst_models_user_set_provider()` / `cst_models_user_drop_provider()`) and
  reload the registry, so the provider is in the list, in `models[]` on the
  wire and in `/provider` of the CLI at once. A name a preset uses overrides
  that preset (a self-hosted endpoint, a proxy); the other content of the file
  (model rules) is kept, and a file that is not a JSON object is never
  overwritten. The key is still a key: it is verified against `GET /models` of
  the new base URL before it is saved, and stored per provider name as before.
- The generation parameters — **temperature**, **top-p**, **max tokens** — are
  remembered per provider in `settings.json` (`"params": {...}`,
  `cst_settings_remember_params()`), and applied to the engine's config by
  `AgentCore::setGenParams()`, `AgentCore::useProvider()` and
  `cst_agent_create()` (so a CLI or TUI run sends what the window was set to).
  An **empty field is not sent at all** — that is not the same as sending 0,
  which is a real temperature; `cst_llm_build_body()` only adds a field that
  was set (`tests/test_llm_body.c:test_gen_params`).
- A long model list (a router lists hundreds) is filtered and capped at 40
  chips with "… +N more", and the whole dialog body scrolls: the buttons stay
  put and nothing can spill out of the frame.

## Attachments

The next prompt can carry files, and they arrive three ways:

- **📎 in the composer** opens a file picker (`QtQuick.Dialogs`).
- **Dropping files on the window** — a `DropArea` covers it; while something is
  dragged over, the border turns accent and says "drop to attach".
- **Ctrl+V** with an image on the clipboard. Text is left to the editor's own
  paste: the composer asks `AgentCore::clipboardHasImage()` first and only
  intercepts the keystroke when there is an image.

`AgentCore::attachFile()` / `attachClipboard()` call `cst_agent_attach_file()` /
`cst_agent_attach_bytes()`: the engine validates the file, copies it into the
session's own directory (`.agent/sessions/<id>/attachments/`), and the next
`run_turn` carries it — the
window only shows what the engine's `pending` list says, one chip per file in
the engine's own words ("note.txt (text/plain, 21 B)"), with "clear all"
(`cst_agent_pending_clear`). A prompt consumes the list, so the chips go away
with the turn. When the model cannot be shown images
(`cst_agent_sees_images() == 0`), the composer says so and the engine sends
them as text notes instead.

`--uitest` writes a file into its scratch workspace and checks the whole path:
`attachFile` succeeds, the engine reports one pending attachment, a missing file
is refused with a reason, the composer shows one chip, "clear all" empties the
list, and — with an 8×8 image put on the clipboard — `clipboardHasImage()` and
`attachClipboard()` behave.

## Images

What a session keeps as a picture is shown, not only stored: a file
`view_image` returned, an image an MCP server sent, a screenshot the user
attached or pasted. Each one appears as a thumbnail in the transcript -- a
prompt's pictures under the message, a tool's under its card -- with the name,
size and origin in the tooltip. The height is capped so a 4K screenshot cannot
push the conversation off the screen, and a file the store no longer has says
which image it was instead of leaving a hole.

The view never touches the filesystem on its own authority: the thumbnails
come from `image://cstattach/<stored name>` (`app/src/ui/SessionImages.cpp`),
where the name is the one the engine wrote next to the session and is checked
with the engine's own `cst_attach_rel_ok()`, so only the session's attachment
directory can be read. The picture is decoded at the size of its thumbnail
rather than at its full resolution, and the provider's directory follows the
session: `AgentCore::attachmentDir()` is re-read on every switch.

A document (PDF, UTF-8 text) still arrives as its name in the message text --
those are sent to the model as text, not as a picture.

## Files the agent delivers

The opposite direction: the engine's `deliver_file` tool (registered in
`src/tools/registry.c`, run in `src/tools/fs_tools.c`) copies a finished file
out of the workspace into the session's own store, and the transcript shows it
as a **file card** -- an extension badge, the file's name, its type and size,
and two buttons.

- The copy is marked `for_user` (`cst_attachment_t.for_user`,
  `cst_attach_import_artifact()`): any bytes up to `CST_ARTIFACT_MAX_BYTES`
  (64 MB), the name's extension decides the mime, and **no request ever
  contains it** -- `src/llm_openai.c` skips those entries when it builds the
  body, which is what keeps a delivered report from being pasted back into the
  context. `tests/test_artifacts.c` holds that down at the wire level.
- A card never invents a path. The row carries the stored file's name, and
  `AgentCore::openArtifact()` / `shareArtifact()` accept it only when one of
  the session's own messages carries that name (`artifactPathOf()`, plus the
  engine's `cst_attach_rel_ok()`), so a forged name is refused with a reason.
- **Open** hands the file to the system: Android builds a `content://` URI
  through the app's FileProvider, checks `resolveActivity()`, starts
  `ACTION_VIEW` and grants the reader permission; a desktop calls
  `QDesktopServices::openUrl`. **Share** uses the phone's share sheet; a
  desktop has none, so the path goes to the clipboard.
- `CST_APP_NO_OPEN=1` makes both do nothing but report the line they would
  write. `--uitest` sets it, so a test run never opens anything for real: it
  replays a session with a delivered `report.md`, checks the card and its two
  buttons, clicks Open (the header must say `opened report.md`), clicks Share
  and checks a name the session does not own is refused.

### Making one: `md_to_pdf`

The front end registers a tool of its own for this (`app/src/core/PdfTools.cpp`,
owner `app:qt`, `platforms = NULL` so every platform the window runs on gets
it): markdown, or a workspace `.md`/`.html` file, becomes an A4 PDF with 15 mm
margins in the workspace, and goes through the same
`cst_attach_import_artifact()` path as `deliver_file` -- so it arrives as a
file card the person can open, print or share, and its bytes never enter a
request. The markdown is rendered by the engine (`cst_web_md_document()`, the
same renderer the WebUI and `md_to_html` use) and Qt lays the HTML out
(`QTextDocument` + `QPdfWriter`, both QtGui); pagination is written here,
page rect by page rect, because `QPrinter`/PrintSupport is desktop-only and a
phone has no print subsystem. The tool runs on the turn's worker thread, and
`--uitest` runs it through the registry and checks the file starts with
`%PDF-`.

The card row on the phone is the same one a picture uses: the store keeps the
PDF next to the session, the image provider refuses it (it is not an image),
and the file card carries it.

## Transcript, tool calls, streaming text

- A tool call is a card of its own, and the call **id** is what pairs it with
  its result: the same tool may run twice in a turn, and pairing by name (what
  the window did before) hung the first card on "running" forever while the
  second one took its result. `AgentCore::toolEvent()` and `toolResult()` carry
  the id (`ctl_tool_call_t.id`), `AgentCore::history()` fills it from the
  session (`tool_call_id`, `tool_calls_json`), and only an id-less call from an
  old text-protocol session still falls back to the name.
- Nothing may keep spinning after a turn: `closeAllRows()` settles every open
  row when the turn ends, and a call with no result becomes "no result"
  (`unfinished`) instead of a spinner that runs forever.
- The answer is rendered **while it streams**: a 120 ms timer re-renders the
  open answer with the engine's own markdown renderer (`cst_web_md_html`, via
  `AgentCore::renderMarkdown()`), so a list or a code fence fills in formatted
  instead of turning into markdown when the turn is over. A replayed session
  renders once, when its rows are built.
- Every signal handler is a plain function on the window
  (`engineToolEvent`, `engineToolResult`, `engineTurnFinished`,
  `engineAssistant`, ...) so `--uitest` can drive the same path: it opens two
  calls of one tool, delivers one result, and asserts that the result landed on
  its own card and that the turn end settled the other one. `rowJson(i)` exists
  for that (a row as JSON — an object would not survive
  `QMetaObject::invokeMethod`).

## Icons, colors

- Icons come from the desktop's **icon theme** (Breeze on KDE), through
  `image://csttheme/<name>?color=%23rrggbb` (`app/src/ui/ThemeIcons.{h,cpp}`).
  Qt Quick has no icon provider of its own without Kirigami, so the window used
  unicode glyphs before (a clip emoji, a gear, a hamburger): those render in
  whichever font covers them — colour emoji in a grey toolbar — and are a box
  on a machine without that glyph. `app/qml/ThemeIcon.qml` is the one place
  that asks for an icon, and every use still names the old character as
  `glyph:`: a host with no icon theme degrades to what it looked like before
  rather than going blank.
- The provider fills Qt's theme search paths itself (XDG data dirs, `~/.icons`
  and, on NixOS, `/run/current-system/sw/share/icons`): Qt only builds them
  from XDG once a theme name is set. It then tries the theme the desktop chose,
  else `breeze-dark` (this window is dark), `breeze`, `hicolor`. Rasterising
  Breeze needs the Qt SVG image format plugin (`qt6.qtsvg` on Nix, part of a
  desktop Qt install) — without it the icons fall back to the glyphs instead of
  disappearing.
- `Theme.toolIcon(name)` maps a tool onto its icon: patch/write → pencil,
  read → text page, list/glob → folder, grep → magnifier, shell → braces,
  web → globe, plan → list, ask → question mark. Toolbar icons are 22 px
  (Breeze's toolbar size), card and row icons 14–16 px.
- `textFaint` is readable grey, not decoration (~5:1 on the card fill): it
  carries hints, secondary lines and provider URLs. Anything written *on* the
  accent fill (a selected provider row, the open session) uses `accentText`,
  `accentTextDim` and `okOnAccent` — green or faint grey on `accentDim` is
  unreadable. The names are not `onAccent…`: QML reads every `onFoo` property
  as a signal handler and refuses the assignment.
- The composer's frame is one `Theme.pad` around its column on **all** sides;
  with the top margin alone the clip and Send hung over the lower border.

## Tools the app provides

A tool implemented in the front end is registered with `cst_tool_register()`
and the owner `app:<name>`, exactly like a plugin or MCP server would:

```c
cst_tool_def_t def = {0};
def.name = "notification_send";
def.desc = "Send a system notification.";
def.perm = CST_TP_ASK;          /* class: drives the consent dialog */
def.perm_name = "notify";       /* policy: what the user is really granting */
def.platforms = ANDROID_ONLY;   /* NULL = everywhere */
def.available = probe;          /* 0 / -1 with a reason; cached */
def.run_ex = my_run;
def.ud = my_state;
def.owner = "app:android";
cst_tool_register(&def);
```

- `platforms` + `available` decide *whether* the tool exists here: an
  Android-only tool never reaches the prompt or `tools[]` on Linux, and
  `cst_tool_run()` refuses it with the reason if a model asks anyway.
- A front-end tool may take over the **name** of a built-in that cannot run
  on this host (the Android clipboard replacing the desktop `xclip` one);
  it may not shadow one that works.
- `cst_tool_unregister_owner("app:android")` drops them again — do it when a
  platform service goes away, then `cst_tool_meta_reload()`.
- `setenv("CST_PLATFORM", ...)` overrides the detected host name (tests, a
  launcher that knows better).

Note `run_ex` runs on the worker thread while the turn is going: touch the
GUI only through queued signals.

## Platform notes

| Platform | How the engine gets built | Platform tools |
|---|---|---|
| Linux | `cmake -S app -B build-app` (libcurl via pkg-config) | clipboard (shell helpers), notification (`notify-send` / D-Bus) |
| Windows | Qt's MinGW kit, `cmake -G Ninja -DCMAKE_PREFIX_PATH=<Qt>/lib/cmake`; the engine needs libcurl for Windows (see `docs/README-windows.md`) | notification via the WinRT/tray API, clipboard through the core's Win32 path |
| Android | engine compiled with the NDK inside the APK (`scripts/build_apk_android.sh`, `-DCST_TUI=0`, `CST_NO_WEBUI=1`); no port, QML talks to `AgentCore` in-process | notification (`Notifier.java`: channel + permission probe), clipboard (`QClipboard` under the engine's own tool names), share sheet (`ACTION_SEND` + chooser), and the file card's open/share through the app's FileProvider (`AndroidTools.cpp`) |
| macOS | Qt from the installer, libcurl from the system | notification (`osascript`), clipboard (`pbpaste`/`pbcopy`) |

Android's long-term shape: the core lives in the APK (no Termux needed), the
platform tools are Kotlin/JNI behind the same `cst_tool_register()` contract.
The build flag that keeps Unix helpers out of the picture is
`CST_PLATFORM=android` (or the `__ANDROID__` detection inside the engine).
A Java class is added by dropping it in `app/android/src/<package>/`:
androiddeployqt copies `app/android/` with the rest of the package source and
Qt's Gradle template puts its `src/` on `java.srcDirs`, so no build-script
change is needed (`Notifier.java` is the first one; a Java helper is the only
way to catch a throwable where the platform throws instead of returning).
`CstService.java` (the foreground service that holds a phone awake while a
turn runs) went in the same way; it is started by `app::holdForeground()`
when a turn begins and stopped by `app::releaseForeground()` when it ends,
so nothing about it is visible when the app is idle.

## Status

- [x] engine as a library (`libcstcore.a` / `cstcore`), in-process embed API
- [x] tool metadata: `perm_name`, `platforms`, `available`, shadowing rule
- [x] `AgentCore` (turns, cancel, consent, todo) and the C smoke test
- [x] QML shell: transcript cards, tool cards with diff coloring, thinking
      blocks, consent/ask dialogs, sidebar, responsive dock/drawer layout,
      `--uitest` for mouse, touch and small-screen checks
- [x] session list in the sidebar: new / switch / delete, transcript replay
- [x] settings dialog: provider, model, key (`cst_ps_*`), token counters
- [x] attachments: picker, drop on the window, Ctrl+V image paste
- [x] icons from the desktop's icon theme (Breeze), with a glyph fallback
- [x] contrast pass: faint text and selected rows are readable
- [x] images in the transcript: tool results and attachments are drawn as
      thumbnails (`image://cstattach/<stored name>`, see the Images section)
- [x] Android APK: the engine is linked in (no port), builds, installs under
      `xyz.whcself.cstagent` and runs on the device (see `docs/android.md`)
- [x] the saved provider key reaches the engine on every start (`AgentCore::open()`
      resolves it: saved key, provider environment, `CST_API_KEY`)
- [x] delivered files: `deliver_file` stores the copy next to the session and the
      transcript draws a file card with Open and Share (see the Files section)
- [x] Android platform tools (JNI: notification, clipboard, share sheet) and the
      file card's open/share through the app's FileProvider
- [x] a turn keeps running with the app off screen (Android foreground service
      + wake lock; nothing to do on a desktop)
- [x] desktop install: launcher entry + icon, `nix profile add --file .`
- [ ] a real turn driven through the window (needs a provider key)
- [ ] SAF file picker, the back gesture, the icon glyphs on the phone
- [ ] Kirigami (the rest of the Breeze look: colors, controls), tray,
      global shortcuts