[danbarua]

Problem

The agent's chat was a page of its own (/agent), reached from a link in the top bar, and its sessions opened in one folder the dev stack names (.labkit-dev/labkit-effect/workspace), whatever workspace the Trace Console showed. Its /new command reloaded the page. A session the address named that the agent could not reopen disabled the composer, so /new could not be sent. The gallery's failed-turn tiles logged "Maximum update depth exceeded".

Change

The chat in the Trace Console

• Right sidebar. In development, inside a workspace, the chat sits at the right of the page. A rail at the right edge stays when the chat is minimised; its chat button expands or minimises it. The top bar's agent link is removed.
• Session lifetime.
  • The session connects the first time the chat is expanded.
  • It stays connected while the chat is minimised; only its view is not drawn.
  • The address names it (?session=), so a reload or a link reopens it.
• Resizing. The border at the chat's left edge moves by drag, Left and Right (16 px), Home (320 px) and End (60% of the window). A double-click returns it to 400 px. The browser keeps the width.
• Motion. The chat slides open and shut over 220 ms, as the left sidebar does, and follows the pointer without the transition while its border is dragged.

Sessions open in the workspace's folder

• Resolver. readWorkspaceDirectories (src/server/workspace-directories.ts) reads workspaces.local.json and checks each entry. openRepositories opens the repository in each folder it returns. The API and the dev server both use it.
• Dev-server endpoint. The dev server answers GET /agent-workspace/<slug>:
  • with { "cwd": "<folder>" } for a workspace the file maps;
  • with { "cwd": null, "reason": "…" } for one it does not map.
    It reads the file on each request, so an edit needs no restart.
• The session's cwd. The chat sends that folder as the session's cwd. labkit-effect's ACP host roots each session's tools in its cwd, and filters session/list by it, so a workspace's sessions are its own.
• Unmapped workspace. A workspace with no folder has no chat. The rail's button is disabled, and its tooltip gives the reason.
• Leaving a workspace. On leaving a workspace, the session the address names is not reopened in the next one, and it leaves the address. Going home drops it too.

The agent's session, shared

• Components. useAgentSession and AgentChat (src/ui/agent/) hold what the /agent page did. A page passes the session to reopen and is told the id of each session started. The /agent page uses them too, keeps its own address scheme, and still opens its sessions in VITE_LABKIT_ACP_CWD.
• /new. Sending /new now connects a new session in place, without reloading the page.
• A failed open or reopen. If opening or reopening a session fails, the composer takes input again, and the error ends with "Send /new to start a new session."

A render loop in @labkit/ui. currentActivity makes a new object on each call. useLingering stored it from an effect that depends on it, so each render set state and drew again, until React stopped it with "Maximum update depth exceeded". An activity equal to the one held now keeps it (sameActivity). The loop affected a failed turn and a running one: the gallery's failed-turn tiles, and a chat whose session failed to reopen.

Controls

• Narrow windows. In a window 860 px wide or narrower, the chat is not a drawer: it takes its width from the page beside it. The left sidebar's drawer is unchanged.
• A new session on each visit. Once the chat has been expanded on a page, each workspace visited opens its own session, even while the chat is minimised. Going home and back opens another session in the same workspace. With the real agent, each one is a saved session. A session could wait to connect until the chat is expanded in each workspace; that is a small change if wanted.
• Where the folder comes from. The browser learns the folder from the dev server, and sends it to the agent as ACP's session/new requires. The server does not yet check that a session's cwd is the workspace's folder. That check is where the design is heading, and it is left for later.
• The /agent page, the sessions list and session replays still use VITE_LABKIT_ACP_CWD. Nothing links to them.
• A closed connection's DELETE can be answered 404. Closing a connection ends its event stream and then sends DELETE /acp. The ACP server (@agentclientprotocol/sdk 1.5.0) forgets a connection whose stream has ended (trackConnectionClose), so the DELETE can find nothing, and the browser logs the 404. The connection is closed either way. The browser tests excuse one such log line for each DELETE answered 404; any other 404 still fails a test.
• Seen in a browser. On :8850, a session opened in bonsai-2026 listed ~/Code/PyCharm/bonsai-2026's own root. I did not look at the layout myself.

Verification

• bun run check: exit 0, 1548 pass, 0 fail.
• bun run e2e with E2E_PORT_API=9019 E2E_PORT_DEV=8970 E2E_PORT_BUILT=8971: 161 passed, 7 skipped (the dev-only tests, in the built bundle).
• Unit tests:
  • tests/workspace-directories.test.ts: an absolute folder and a ~/ folder are mapped. A missing file, a file that is not a JSON object, and an entry that is not a string or not absolute are skipped, each with its log line.
  • tests/repositories.test.ts: a folder that holds a repository is opened, and one that does not is skipped with a warning.
  • packages/ui/tests/activity.test.tsx: two equal activities, including a failed turn's two new objects, are the same activity; another kind or tool label is not.
• e2e, dev server (the built bundle asserts the rail is absent):
  • The rail is at the page's right edge in a workspace, and absent at /app/.
  • Expanding the chat sends session/new with alpha's mapped folder as cwd, and names the session in the address.
  • Minimising and expanding again keeps the session. Opening another record keeps it in the address, and a reload reopens it.
  • In beta, which the e2e mapping file does not map, the button is disabled, and its tooltip says the file maps no folder to beta. Going home dropped the session from the address.
  • With ?session=no-such-session, the chat says the reopen failed and suggests /new. The composer is enabled, and /new starts a session that the address then names.
  • /agent starts a session and takes its address, and /new starts another without a reload.
  • Dragging the chat's border 100 px left widens it from 400 to 500 px, and a reload keeps 500. Right gives 484, Home 320, End 768 (60% of 1280), and a double-click 400.
  • The gallery draws every tile without an error.
• Before and after the render-loop fix, with 4 workers:
  • The stale-session test failed 8 of 8 runs before the fix.
  • A test that only opens the gallery failed 4 of 12 runs on main.
  • After the fix, the stale-session and gallery tests passed 16 of 16 runs.
  • The loop's stack, captured from React's warning, pointed at useLingering's effect.

Linked issues

None. This follows #669.

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