AGENTS.md

1### Data Flow
2 
31. Optional composer helpers such as `core/input-polish` can rewrite the local draft before submission, and `core/voice-input` can transcribe browser microphone input into that same local draft; confirmed user input then flows to thread hooks (`core/threads/hooks.ts`) → LangGraph SDK streaming
42. Stream events update thread state (messages, artifacts, todos, goal). The main thread stream uses the LangGraph SDK's `throttle: true` mode so updates received in the same macrotask coalesce before React is notified; do not replace it with a numeric delay without validating the SDK's trailing-debounce behavior on a continuous stream.
5   File-tool artifact auto-open work must run in an effect with timer cleanup; never schedule timers while rendering streamed `write_file` or `str_replace` updates.
6   `ThreadState.artifacts` remains the authoritative artifact list. The artifacts provider persists only thread-scoped panel UI state (`open`, selected path, and a refresh bootstrap cache) in session storage; an initial empty stream value must not overwrite that restored state before history finishes loading.
7   Formal artifact content is refreshed once when the run finishes; transient `write-file:` previews remain message-driven.
8   The detail view exposes explicit editing only for an already-opened formal UTF-8 text artifact under `/mnt/user-data/outputs`. Drafts stay in provider memory until Save so switching right-side panels cannot discard them, render in Markdown/HTML preview, and are protected from remote refreshes by the loaded SHA-256 revision. Saving is disabled during an active run; a changed revision preserves the draft and surfaces a conflict instead of overwriting agent output.
9   Regular artifact text loads request at most the first 1 MiB through an HTTP
10   byte range. A truncated preview must stay lightweight and expose an explicit
11   full-file action; do not mount CodeMirror for that artifact until the user
12   requests and receives the complete content. The Gateway retains range
13   ownership and returns 206/416 through `FileResponse`.
143. `useThreadHistory` loads persisted conversation pages from `GET /api/threads/{id}/messages/page`, preserving the backend's thread-global event `seq`; rendering overlays checkpoint/live copies at their matching canonical identities (a summarized checkpoint may contain a protected early input plus a recent tail). Context-compaction rescue diffs every retained visible identity rather than slicing at the first anchor, and keeps a run-scoped ledger of committed visible messages so replacement updates and repeated rolling checkpoint windows cannot erase an already displayed step. The resolver suppresses checkpoint/transient prefixes whose canonical position is still behind an unloaded cursor page instead of collapsing that unknown gap before a recent anchor, then adds optimistic messages without timestamp re-sorting. History invalidation preserves already-loaded pages so their established ordering positions are not discarded. Dynamic context re-keys the submitted user message from `X` to `X__user`; UI identity matching normalizes that reserved suffix only for human messages so the submitted frame and checkpoint replacement remain one visible turn. A locally submitted turn also records its pre-submit identity baseline: if `messages-tuple` publishes new AI/tool steps before `values` publishes that turn's human message, render ordering moves only those non-baseline visible steps behind the new human while leaving history, hidden controls, and reconnected runs untouched. Keep that local order anchor through finish, stop, and stream error because the SDK's settled frame can retain transient event order; replace it on the next local submit and clear it on thread switch or replay-gap recovery.
154. Stop actions call the LangGraph SDK stream stop path; `core/threads/hooks.ts` invalidates current-thread, thread-history, token-usage, and sidebar/search caches immediately and schedules one follow-up refetch because SDK stop may finish via abort + fire-and-forget cancel before backend title finalization commits
165. TanStack Query manages server state; localStorage stores user settings. The
17   Settings > Tools MCP switch calls the targeted `PATCH /api/mcp/config`
18   mutation, disables switches until that mutation's success refetch completes,
19   displays the backend error `detail` through a toast, and invalidates
20   `["mcpConfig"]` only after success.
21   Settings > Integrations uses a local generation only to suppress stale React
22   callbacks; server-issued Lark flow generations must be passed through every
23   config/auth completion and across switch-or-register to authorization chains
24   so backend cross-tab ordering remains authoritative.
256. Components subscribe to thread state and render updates
26 
27The chat header's context-window control is intentionally persistent: while `context_usage` is unavailable, `ContextUsageBadge` renders a gauge placeholder rather than unmounting; once data arrives, the same position shows the percentage. `useThreadTokenUsage` retains placeholder data only when the response `thread_id` still matches the active route, so same-thread refetches do not flicker and cross-thread navigation never displays the previous chat's usage.
28 
29Run duration is run-scoped UI metadata even though the compatibility field `additional_kwargs.turn_duration` is repeated on historical AI messages. `core/messages/run-duration.ts` folds those copies into one display anchored after the run's last visible message group. `MessageList` owns the temporary client-side duration for a just-completed live turn until authoritative history arrives. The duration is total run wall-clock time, not per-message reasoning time; reasoning disclosure and run activity/duration are rendered separately.
30 
31The workspace-change card follows the same rule: it is resolved from `(threadId, runId)` alone, so every AI message of a run would render an identical copy. A run ends in more than one terminal assistant bubble whenever the model emits answer text that never gains a tool call, so `core/messages/workspace-change-anchor.ts` picks the run's last assistant bubble and `MessageListItem` renders the badge only for that anchor (#4555). Any future run-scoped display belongs in the same place — do not hang one off every message. The two anchor helpers deliberately differ in which group types they accept as a run's last position, because an anchor is only useful where the display is actually rendered: run duration is emitted by `MessageList` around every group, so it accepts any type, while the workspace-change card comes from `MessageListItem` and so restricts to `assistant`. Keep a new helper's candidate set matched to its own render site rather than unifying them.
32 
33Composer drafts are tab-scoped browser state. `core/threads/composer-draft.ts` stores only text plus the selected slash-skill name in `sessionStorage`, keyed by user, agent, and logical conversation scope. New-chat pages pass the stable scope `"new"` because their runtime `threadId` is a fresh UUID on every reload; established conversations use their real thread ID. `InputBox` waits for enabled skills before restoring a skill chip, degrades a missing/disabled skill back to editable slash text, and clears the stored draft through `SendMessageOptions.onSent` only after the send passes the in-flight guard. Attachments, sidecar quotes, voice state, and polish undo state are not persisted.
34 
35Auth UI note: the login page's "keep me signed in" option submits only `remember_me` to the Gateway and may persist only the email address through `core/auth/remember-login.ts`. Passwords and tokens must never be stored in frontend storage; the `HttpOnly access_token` and readable `csrf_token` cookies remain Gateway-owned.
36 
37`/goal` and `/compact` are built-in composer commands, not skill activations. `src/components/workspace/input-box.tsx` intercepts `/goal`, `/goal clear`, and `/goal <condition>` before normal chat submission, calling Gateway `GET/PUT/DELETE /api/threads/{thread_id}/goal`. Setting `/goal <condition>` also submits the condition text as the next user task so the agent starts running immediately; status and clear do not start a run. Goal and compact requests are tied to the current `threadId` with an `AbortController`, so switching threads or unmounting the composer aborts in-flight requests and stale responses cannot update the new thread's composer state. The chat pages render `GoalStatus` above the composer from `AgentThreadState.goal`, with local optimistic state until the next stream `values` update arrives. `/compact` calls `POST /api/threads/{thread_id}/compact` to summarize older active context while leaving the full visible chat history intact; it is skipped on new/empty threads and blocked server-side while a run is in flight. Thread rename uses the same serialized state-write route; the rename dialog stays open and surfaces the server error when an active run returns 409.
38 
39The `/` skill list stays reachable after a skill is selected: typing `/` in the editable text beside the chip reopens it, and picking an entry swaps the chip rather than adding a second one, because the wire format carries exactly one leading `/skill`. That list offers skills only while a chip is selected — a builtin command owns the whole composer line, so `/goal` behind a selected skill would submit as chat text instead of running the command. The trigger itself is unchanged: a slash only opens the list at the start of the input (`getLeadingSlashSkillQuery`), pinned by `tests/e2e/chat.spec.ts`.
40 
41Human input requests are a structured message protocol layered on normal chat history. The backend writes request payloads to `ToolMessage.artifact.human_input`, `src/core/messages/human-input.ts` owns the runtime validators/types, and `src/components/workspace/messages/human-input-card.tsx` renders the reusable card. The protocol is versioned on the request side only: v1 covers `free_text` / `choice_with_other`, and v2 adds `form` (typed fields — text/textarea/number/select/multi_select/checkbox/date — with required-field validation in the card). Replies deliberately stay on the v1 response protocol: the form card submits a `response_kind: "text"` reply whose value is the human-readable summary plus one JSON block keyed by stable field names (`buildHumanInputFormSubmissionValue` — the readable part alone is ambiguous because labels/values may contain the separators), so the model can reconstruct the submitted mapping without a structured response kind. The validators reject unknown versions/modes (and field names colliding with JS `Object.prototype` members) so future protocol bumps degrade to the plain-text ToolMessage fallback rather than rendering a broken card. Form values are read through own-property access only (`readHumanInputFormValue`); select fields stay controlled from their empty-string placeholder state through selection; checkbox fields are native `<input type="checkbox">` controls seeded to an explicit `false` (`buildInitialHumanInputFormValues`) so an untouched checkbox submits as "no" while a `required` checkbox keeps must-agree semantics (no HTML `required` attribute — native constraint validation would intercept the custom submit path), and form controls carry label/`htmlFor`, `aria-required` plus a visually-hidden localized "required" marker, and `aria-invalid`/error associations whose error node stays mounted while any field is still invalid. Composer-bypass closure: `deriveHumanInputThreadState` treats a visible plain human message as answering the latest unanswered request opened before it (only the latest — nothing guarantees a single outstanding request across runs, and closing all would silently swallow older decisions; an older request left open simply becomes the active card again). This lets current users bypass a structured form through the normal composer and preserves compatibility with old v1-only frontends that degrade a v2 request to plain text. `MessageList` owns answered/latest/pending state for visible cards, but derives answered responses from raw `thread.messages` because replies are hidden; pending cards clear when the hidden reply appears, when dispatch is dropped, or when a new `thread.error` reports an async stream failure. Page-level card submit callbacks must send a normal human message and put `hide_from_ui: true` plus the response payload in the fourth `sendMessage(..., options)` argument as `options.additionalKwargs`; the third argument remains run context such as `{ agent_name }`. Composer entry points remain enabled while a human-input request is open; a normal visible message intentionally bypasses the card and starts the next run without structured response metadata.
42 
43Tool-calling AI messages can contain user-visible text as well as `tool_calls`. `core/messages/utils.ts` keeps these turns in an `assistant:processing` group, and `components/workspace/messages/message-group.tsx` must render the visible text as a processing step instead of treating the message as only tool metadata. This preserves provider text such as error explanations or "trying another approach" notes during tool-heavy runs.
44While the current turn is still loading, a content-only AI message after the latest visible human input also stays in that processing group until the turn settles: a provider may append tool-call chunks to the same message later, and classifying it as a final assistant bubble too early makes the text jump into the steps panel. `MessageGroup` therefore renders processing text even before the first tool call arrives.
45The same rule applies after an earlier tool call: a later content-only AI message remains visible after the current last tool-call step while streaming, because that message may itself gain another tool call before the turn settles.
46Because the same message is rendered by two different components over its lifetime, reasoning must sit above the answer text in both. `MessageListItem` paints the settled bubble's `<Reasoning>` disclosure above its content, so `MessageGroup` puts the trailing reasoning disclosure above the assistant text that follows it and `convertToSteps` emits a message's reasoning step before its content step — otherwise the two swap places the instant the turn settles (#4576). Assistant text emitted _before_ that reasoning keeps its earlier position; only the answer the reasoning produced moves below it.
47 
48Edit-and-rerun is deliberately latest-turn-only. `core/messages/utils.ts::getLatestEditableTurn()` exposes a human turn only when the transcript is idle and the most recent visible turn ends in a terminal assistant message. `core/threads/hooks.ts::editAndRegenerateMessage()` calls `POST /api/threads/{id}/runs/edit-regenerate/prepare`, submits the returned replacement message/checkpoint/metadata through the same LangGraph stream path as regenerate, optimistically hides the superseded message ids, and clears the optimistic replacement once the persisted replacement arrives.
49 
50`MessageGroup` builds its tool-result and browser-preview lookups once per processing group before converting messages to steps. The lookup preserves the first non-empty result and first screenshot-bearing browser view for each tool-call ID, matching the streamed-message display semantics without repeatedly scanning the full group for every tool call.
51 
52### Key Patterns
53 
54- **Server Components by default**, `"use client"` only for interactive components
55- **Static root boundary** — `src/app/layout.tsx` must not read cookies or import
56  chat-only KaTeX/Streamdown styles. Auth and workspace layouts own the cookie-derived
57  locale provider; docs derive locale from their route, and blog owns its preference
58  cookie. Public server routes load one dictionary at a time through
59  `core/i18n/translations.ts`; the interactive auth/workspace client provider owns both
60  formatter-bearing dictionaries because functions cannot cross the RSC boundary.
61  Keep public `/` static and keep rich-content CSS on the routes that render it.
62- **Thread hooks** (`useThreadStream`, `useSubmitThread`, `useThreads`) are the primary API interface
63- **Thread routes** — construct Web UI chat paths through `core/threads/utils.ts::pathOfThread()`, which percent-encodes both custom agent names and thread IDs before inserting them into route segments
64- **LangGraph client** is a singleton obtained via `getAPIClient()` in `core/api/`
65- **Run stream options** are sanitized by `core/api/stream-mode.ts`: the Gateway-supported set is `values`, `messages-tuple`, `updates`, `debug`, `tasks`, `checkpoints`, and `custom`; any request containing an unsupported mode throws before HTTP instead of being partially forwarded or silently defaulting to `values`. `streamResumable` is retained by thread hooks only for SDK-side reconnect bookkeeping but stripped before the HTTP request because the Gateway does not accept that request option; actual replay uses the SSE `Last-Event-ID` cursor. Keep this boundary aligned with the backend request schema; `messages` and `events` are not supported and must not be forwarded.
66- **SSE replay gaps** are handled in `core/api/api-client.ts`, which wraps both initial and joined run streams because the upstream SDK ignores unknown event names. An id-less backend `gap` control frame clears stale reconnect metadata, emits an internal `stream_replay_gap` custom event, reloads durable thread values, and rejoins after the server-provided retained tail, with up to five recovery rejoins after the original stream (six total stream calls on an all-gap exhaustion path). The wrapper remains a lazy async iterable because the SDK consumes it with `for await`. `core/threads/hooks.ts` clears optimistic/transient/subtask state, invalidates durable history caches, and shows the localized recovery warning; never let a gap fall through as a normal stream finish or cancel the still-running backend run.
67- **Streaming Markdown rendering** is owned by `core/streamdown`: Streamdown's `animated` / `isAnimating` API handles incremental word animation, while the shared `streamdownRenderingPlugins` config registers the named code-highlighting and Mermaid plugins required by Streamdown 2.5. Keep wrappers and derived configs wired to that shared object; do not reintroduce a rehype plugin that wraps every word, because reparsing a growing block remounts old words and replays their animation.
68- Citation links in message and artifact Markdown must derive their `citation:` label from the full `ReactNode` children tree, since Streamdown may provide element or array children during streaming rather than a plain string.
69- **Environment validation** uses `@t3-oss/env-nextjs` with Zod schemas (`src/env.js`). Skip with `SKIP_ENV_VALIDATION=1`
70- **Subtask step history and runtime metadata** (`core/tasks/`) — the subtask card shows a subagent's full step timeline (#3779): its assistant reasoning turns interleaved with the tools it ran. `Subtask.steps[]` is accumulated live from `task_running` events (appended via `mergeSteps`, not overwritten) and backfilled on expand for historical runs by `fetchSubtaskSteps`, which pages the events endpoint scoped to one task (GET `/runs/{runId}/events?event_types=subagent.step&task_id=…&after_seq=…`) until a short page, so the run-wide limit can't truncate the timeline. `task_started` carries the effective `model_name`; `task_running` carries a cumulative usage snapshot after each completed LLM call. `core/tasks/lifecycle.ts` normalizes these additive events, and `computeNextSubtask` keeps the largest cumulative total so replayed or late SSE frames cannot double-count or roll the folded card backward. Terminal ToolMessage metadata (`subagent_model_name` / `subagent_token_usage`) restores the same values from normal history after reload; no per-card event fetch is needed. `core/tasks/steps.ts` is the pure step model: `messageToStep` (live), `eventsToSteps` (reload), `mergeSteps` (dedup by `message_index`), and `stepsForDisplay` (what the card renders — keeps tool steps + AI steps with text, drops the trailing final-answer AI step when completed since it's shown as `result`). `core/tasks/context.tsx`'s `useUpdateSubtask` applies updates against a `tasksRef` mirroring the latest state (not a closure snapshot), so a late-resolving `fetchSubtaskSteps` backfill merges into current state instead of clobbering SSE steps or sibling subtasks that arrived meanwhile. The owning `run_id` is carried onto history content messages in `buildVisibleHistoryMessages` so the card can resolve the events endpoint.
71 
72### Interaction Ownership
73 
74- `src/app/workspace/chats/[thread_id]/page.tsx` owns composer busy-state wiring.
75- `src/app/workspace/chats/[thread_id]/page.tsx` owns branch-from-turn submission and navigation; sidecar `MessageList` instances do not receive the branch action.
76- `src/app/workspace/chats/[thread_id]/page.tsx` and `src/app/workspace/agents/[agent_name]/chats/[thread_id]/page.tsx` own edit-and-rerun submission wiring because the page must preserve normal/custom-agent run context; `MessageList` only detects the latest editable user turn and renders the inline editor.
77- `src/app/workspace/chats/[thread_id]/page.tsx` gates the Workspace Browser trigger and browser right panel on `/api/features -> browser_control.enabled`; `src/app/workspace/agents/[agent_name]/chats/[thread_id]/page.tsx` applies the same capability gate and additionally requires the Custom Agent's tool groups to be unrestricted or include `browser`. Default/failed feature discovery hides the browser control so optional backend installs do not show a dead Live socket.
78- `src/app/workspace/chats/[thread_id]/page.tsx` and `src/app/workspace/agents/[agent_name]/chats/[thread_id]/page.tsx` own active-goal display state for their composer overlays.
79- `src/components/workspace/messages/message-list.tsx` owns human-input card answered/latest/pending gating; entry pages only translate a submitted card response into `sendMessage` calls.
80- `src/components/workspace/browser-view/browser-view-panel.tsx` forwards each physical pointer click as one `click` input; do not also emit `down`/`up` for the same gesture because the remote Playwright click would run twice.
81- `src/components/workspace/browser-view/use-browser-stream.ts` requests binary JPEG
82  frames with `frame_format=binary`; status, URL, tabs, and navigation rejection
83  messages remain JSON. `LatestBrowserFrameBuffer` keeps only the newest pending
84  frame, publishes through `useSyncExternalStore` at most once per animation
85  frame, and owns object-URL revocation. Keep the Gateway's legacy JSON/base64
86  frame path for older clients.
87- `src/core/threads/hooks.ts` owns pre-submit upload state and thread submission.
88- `src/components/workspace/chats/chat-box.tsx` owns the desktop right-panel layout, and **all three** right panels (artifacts, sidecar, browser) share one `ResizablePanelGroup` — do not fork a non-resizable branch per panel kind, which is how the artifacts divider silently lost its drag handle (#4465). Open/close is `collapse()` / `resize()` on the side panel's imperative handle, not conditional rendering, so the width can animate. Three constraints hold that together: the size transition is applied from the group as `[&>[data-panel]]:transition-[flex-grow]` because the sized flex item is the library's own `[data-panel]` element rather than the child `className` lands on; it is applied only while an open/close is in flight, so a drag is not interpolated frame by frame; and during the animation the panel content is held at its final width in `cqw` and clipped, because a reflowing message list re-runs its scroll-to-bottom (pinned by `tests/e2e/sidecar-chat.spec.ts`'s no-animated-scroll test) and a re-wrapping composer changes which responsive labels it shows. Because the panel is `collapsible`, the library can also collapse it to `0%` on its own when a drag crosses `minSize`, without going through the state that owns it. `onResize` records the last positive size while the pointer moves, but the owning `sidecar` / `browserView` / `artifactsOpen` state must only mirror a final `0%` layout from `onLayoutChanged`, after pointer release; closing on the first `0%` resize frame breaks a continuous drag that reaches the edge and then reverses before release.
89