pi-agent-integrated/pi-web/AGENTS.md

# Pi Web - Development Notes

## Quick Start

```bash
npm run dev   # port 30141
```

Typecheck: `node_modules/.bin/tsc --noEmit`  
Lint: `npm run lint`  
**Never run `next build` during dev** — pollutes `.next/` and breaks `npm run dev`.

---

## Architecture

```
Browser             Next.js frontend             Pi Agent Server
  │                       │                           │
  ├─ GET/POST /api/* ────▶│ rewrite to :30142 ─────▶│ Hono routes
  ├─ SSE connect ────────▶│ transparent proxy ─────▶│ AgentSession events
  │◀── data: {...} ───────│◀────────────────────────│
```

`pi-web/` owns only React/Next.js UI code. All filesystem access, authentication,
configuration, Pi packages, API routes, SSE streams, and AgentSession state live
in `../server/`. The frontend proxies `/api/*` through `next.config.ts`; restarting
or hot-reloading Next.js must not interrupt an active Agent session.

**Session browsing** (read-only): the backend reads `.jsonl` files through SDK
`SessionManager` helpers and `server/src/lib/session-reader.ts`.
**Sending a message**: `startRpcSession()` in `server/src/lib/rpc-manager.ts`
creates and retains the AgentSession in the standalone backend process.

---

## File Map

```
../server/src/
  index.ts             Hono server, health endpoint, route registration
  security.ts          host/origin gate for every /api request
  routes/agent.ts      Agent creation, commands, state, and SSE
  routes/auth.ts       OAuth/device-code and API-key routes
  routes/config.ts     extensions, MCP, vision, and plugin configuration
  routes/files.ts      guarded file reading, preview, download, and upload
  routes/misc.ts       cwd, runtime, file index, worktrees, and project trust
  routes/models.ts     Git state, models, discovery, catalog, and tests
  routes/sessions.ts   session listing, context, naming, export, and deletion
  routes/skills.ts     skill listing, search, install, and update
  lib/rpc-manager.ts   AgentSessionWrapper registry and startRpcSession()
  lib/session-reader.ts SessionManager wrappers and session path cache

lib/
  agent-client.ts      typed fetch helper for /api/agent commands
  draft-store.ts       local draft persistence helpers
  file-paths.ts        client-side path encoding helpers
  markdown.ts          shared markdown helpers
  pi-types.ts          structural copies of API/session types; no Pi dependency
  tool-presets.ts     PRESET_NONE/DEFAULT/FULL + getPresetFromTools()
  types.ts            shared TypeScript types
  normalize.ts        normalizeToolCalls() — field name mismatch between file format and our types

components/
  AppShell.tsx        layout + URL state + tab management
  SessionSidebar.tsx  session tree + FileExplorer
  ChatWindow.tsx      chat composition + completion sound wrapper
  ChatInput.tsx       input bar + model/thinking/tools/compact controls
  MessageView.tsx     renders one message (user/assistant/toolCall/toolResult)
  BranchNavigator.tsx in-session branch switcher
  ChatMinimap.tsx     scroll minimap alongside the message list
  MarkdownBody.tsx    markdown renderer
  ModelsConfig.tsx    modal for editing models.json (opened from sidebar bottom)
  PluginsConfig.tsx   modal for installed package plugins
  SkillsConfig.tsx    modal for loaded/search/installable skills
  FileExplorer.tsx    file tree inside sidebar
  FileIcons.tsx       file icon helpers
  FileViewer.tsx      file content in a tab
  TabBar.tsx          tab bar (Chat + open file tabs)

hooks/
  useAgentSession.ts  messages + streaming + SSE + fork/navigate/reconciliation logic
  useAudio.ts         completion sound + browser AudioContext unlock
  useDragDrop.ts      shared drag/drop state
  useIsMobile.ts      responsive breakpoint hook
  useTheme.ts         theme state
```

---

## Key Design Decisions & Traps

### AgentSession lifecycle (`server/src/lib/rpc-manager.ts`)
- One `AgentSessionWrapper` per session id, keyed in `globalThis.__piSessions`
- The standalone backend process survives Next.js hot reloads and restarts
- Idle timeout: 10 minutes. Concurrent `startRpcSession()` calls share a single start Promise (`globalThis.__piStartLocks`)

### Fork must destroy the wrapper immediately
`AgentSession.fork()` **mutates the wrapper's inner state in-place** — after fork, `inner.sessionId` is the *new* session's id. If the wrapper stays alive in the registry under the old id, the next request gets the already-forked state and subsequent forks produce a corrupt `parentSession` chain.

**Fix**: `send("fork")` captures `newSessionId`, then calls `this.destroy()` before returning. The next request for the original session reloads a clean AgentSession from the original file.

### Two kinds of branching — don't confuse them
- **Fork** (Fork button on user message): creates a new independent `.jsonl` file. Shown as a child in the sidebar tree via `parentSession` header field.
- **In-session branch** (Continue button / BranchNavigator): calls `navigate_tree` within the same file. Multiple entries share the same `parentId`. Switching between them calls `/api/sessions/[id]/context?leafId=`.

### Session files can be fully rewritten
`parentSession` in the header is **display metadata only** — has zero effect on chat content. Safe to `writeFileSync` the entire file (pi does this itself during migrations). Used when cascade-reparenting children on delete.

### ToolCall field normalization
Pi stores toolCall blocks as `{type:"toolCall", id, name, arguments}` but `ToolCallContent` uses `{toolCallId, toolName, input}`. `normalizeToolCalls()` in `lib/normalize.ts` handles this — called in both `session-reader.ts` (file load) and `ChatWindow.handleAgentEvent()` (streaming).

### New session tool preset
Tool names are passed at session creation (`POST /api/agent/new` → `toolNames[]`). For existing sessions, the active preset is inferred on mount via `get_tools` → `getPresetFromTools()`. When tools are fully disabled (`toolNames = []`), `rpc-manager.ts` passes an empty tool allow-list and forces `agent.state.systemPrompt = ""` after startup/reload/resource discovery.

### Model defaults for new sessions
`GET /api/models` returns `defaultModel` read from `~/.pi/agent/settings.json`. `ChatWindow` pre-selects this on mount for new sessions.

### SSE reconnect on page refresh mid-stream
On `ChatWindow` mount, `GET /api/agent/[id]` is called. If `state.isStreaming === true`, SSE is reconnected automatically. `thinkingLevel` and `isCompacting` are also synced from this response.

### Compaction SSE events
Newer pi emits `compaction_start` / `compaction_end`; older versions emitted `auto_compaction_start` / `auto_compaction_end`. `handleAgentEvent` accepts both sets to keep `isCompacting` in sync. Manual compact is a blocking POST — the button stays disabled until the response returns.

### Running state SSE + reconciliation
- The sidebar listens to `/api/agent/running/events`, backed by `subscribeRunningSessions()` in `server/src/lib/rpc-manager.ts`, so running badges update without polling.
- `useAgentSession` still treats per-session SSE as primary for chat events, but while a run is active it periodically calls `GET /api/agent/[id]` and also reconciles on `visibilitychange`/`online`. This fixes missed `agent_end` events from background tabs or half-open connections.
- Prompt runs use a monotonic run id; late SSE or slow reconciliation responses from an old run must be ignored so they cannot resurrect stale streaming bubbles.

### Worktrees and project grouping
- `server/src/lib/worktree.ts` resolves linked worktree top-levels back to the main repo `projectRoot`; `listAllSessions()` attaches that to each `SessionInfo` so all worktrees for one repo are grouped together in the sidebar.
- Worktree operations are served by `/api/worktrees` and guarded by the same allowed-root rules as `/api/files`.
- New worktrees are created under `<repoRoot>-worktrees/<sanitized-branch>`. Existing branches are reused; otherwise `git worktree add -b` creates the branch.
- Removing a dirty worktree returns `409` with `{ dirty: true }` so the UI can ask before retrying with `force`.
- Sessions whose cwd points at a removed worktree are inferred back into the main project instead of becoming a phantom project row.

### File access allow-list
- `/api/files` is intentionally not a general filesystem browser. Allowed roots come from session cwds, their resolved project roots, `~/pi-cwd-*`, and roots explicitly added with `allowFileRoot()`.
- `/api/cwd/validate`, `/api/default-cwd`, and `/api/worktrees` call `allowFileRoot()` when they make a new location browsable.

### Plugins and skills
- `/api/plugins` uses pi's `SettingsManager` + `DefaultPackageManager` for global/project package install, remove, update, enable, and disable. Disabling writes empty `extensions/skills/prompts/themes` arrays for that package entry.
- `/api/skills` uses `DefaultResourceLoader` so settings paths, package skills, and project `.agents/skills` are listed the same way the runtime sees them.
- Skill toggling edits only the `disable-model-invocation` frontmatter key on the target `SKILL.md`; keep that surgical so user formatting survives.
- `/api/skills/install` shells through `npx skills add ... --agent pi`; project installs run with the selected cwd.

### Auth and model config
- `ModelsConfig` combines models from `~/.pi/agent/models.json` with provider auth status from pi's `AuthStorage`/`ModelRegistry`.
- OAuth/device-code/manual-code flows are streamed by `GET /api/auth/login/[provider]`; manual code responses POST back with a short-lived token stored in `globalThis.__piLoginCallbacks`.
- API-key routes store and remove keys through `AuthStorage`. Status endpoints must never return the raw key.
- The model test endpoint is registered in `server/src/routes/models.ts` as `/api/models-config/test`; `/api/models/test` is not a real route.

### Completion sound
- `hooks/useAudio.ts` stores the toggle in `localStorage` as `pi-sound-enabled` and reuses one `AudioContext`.
- Browser autoplay policy means sound must be unlocked from a user gesture; `ChatInput` calls the unlock hook from interactive controls, and `ChatWindow` plays the tone from `onAgentEnd`.

### Exported session HTML
- `/api/sessions/[id]/export` delegates to pi's export helper, then patches recursive tree helpers in the generated HTML to iterative versions so very deep linear sessions do not overflow the browser call stack.

## Pi Session File Format

Location: `~/.pi/agent/sessions/<encoded-cwd>/<timestamp>_<uuid>.jsonl`

```jsonl
{"type":"session","version":3,"id":"<uuid>","timestamp":"...","cwd":"/path","parentSession":"/abs/path/to/parent.jsonl"}
{"type":"model_change","id":"<8hex>","parentId":null,"provider":"zenmux","modelId":"claude-sonnet-4-6","timestamp":"..."}
{"type":"message","id":"<8hex>","parentId":"<8hex>","message":{"role":"user","content":"..."}}
{"type":"message","id":"<8hex>","parentId":"<8hex>","message":{"role":"assistant","content":[...],...}}
{"type":"message","id":"<8hex>","parentId":"<8hex>","message":{"role":"toolResult","toolCallId":"...","content":[...]}}
{"type":"compaction","id":"<8hex>","parentId":"<8hex>","summary":"...","firstKeptEntryId":"<8hex>","tokensBefore":N}
{"type":"session_info","id":"...","parentId":"...","name":"user-defined name"}
```

`entryIds[]` in `SessionContext` is a parallel array to `messages[]` — maps each displayed message back to its `.jsonl` entry id, used for fork and navigate_tree calls.

---

## CSS Variables (`app/globals.css`)

```
--bg --bg-panel --bg-hover --bg-selected --border
--text --text-muted --text-dim
--accent --user-bg --tool-bg
--font-mono
```