Hermit/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

# 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.

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:

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 file in the workspace's store (.agent/sessions/<id>.jsonl), 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.

• 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.

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:

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 (-DCST_TUI=0, CST_NO_WEBUI=1); the app talks to Android APIs through Qt (JNI)	notification (Android), share sheet, clipboard, file picker
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).

Status

• engine as a library (libcstcore.a / cstcore), in-process embed API
• tool metadata: perm_name, platforms, available, shadowing rule
• AgentCore (turns, cancel, consent, todo) and the C smoke test
• 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
• session list in the sidebar: new / switch / delete, transcript replay
• a real turn driven through the window (needs a provider key)
• attachments (drag in, paste), settings page (provider, model, key)
• Kirigami (Breeze look), tray, global shortcuts
• Android APK (engine in-process, JNI platform tools)