feat(studio): Chats core surface + Playwright e2e infrastructure

.github/workflows/studio.yml

@@ -61,3 +61,30 @@ jobs:
             echo "Proprietary SPDX headers are not allowed in studio/" >&2
             exit 1
           fi
+
+  # Browser smoke over the real proxy tier against the fixture daemon.
+  # Separate job so a browser-infra flake never masks the checks above.
+  e2e:
+    name: Playwright (fixture daemon)
+    runs-on: ubuntu-24.04
+    timeout-minutes: 20
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+
+      - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
+        with:
+          node-version-file: studio/.nvmrc
+          cache: npm
+          cache-dependency-path: studio/package-lock.json
+
+      - name: Install
+        working-directory: studio
+        run: |
+          npm ci --ignore-scripts
+          npx playwright install --with-deps chromium
+
+      - name: Build and test
+        working-directory: studio
+        run: npm run test:e2e

docs/adr/0289-studio-server-backed-chats.md

@@ -0,0 +1,96 @@
+# ADR 0289 — Studio's chat list is the daemon's session store
+
+- Status: Accepted
+- Date: 2026-08-18
+- Scope: `studio/` — where a chat's existence, title, and transcript live, and which
+  client actions are server calls
+
+> History: re-lands the unmerged draft from PR #615 (numbered 0227 there before
+> that id was taken on main), adapted to the Atrium workspace UI.
+
+## Context
+
+The prototype Studio descended from kept its chat list in browser state — first
+a `localStorage` key, then mock fixtures mirrored in module scope. `mecated`
+persisted the same sessions the whole time: the daemon already exposed
+`GET /v1/sessions`, `GET /v1/sessions/{id}/transcript`,
+`POST /v1/sessions/{id}/rename`, and `POST /v1/sessions/{id}/delete` — and the
+client called none of them.
+
+Every consequence followed from that one gap:
+
+- A second browser, or a second machine, saw nothing. The daemon held the work;
+  the client that opened it held the only record of what the work was called.
+- Renaming a chat renamed a local label that no other client would ever see.
+- Deleting a chat dropped the client's copy and left the session in the store
+  forever — "delete" quietly meant "hide".
+- A reload during a run orphaned it. `mecated` keeps running after the page
+  that started it goes away, but the client had no way back to the result: the
+  run streams off the `POST /prompt` response body, and that body is gone.
+- The client also minted its own session ids and mapped them lazily onto daemon
+  sessions, so the daemon's record and the sidebar disagreed about what even
+  existed.
+
+The persistence was never missing. It was unused.
+
+## Decision
+
+The daemon's session store is the record of which chats exist, what each is
+called, and what was said in each. Studio reads and writes that record, and
+**the sidebar id IS the daemon session id** — there is no client-side session
+mapping.
+
+- **The chat list is the session inventory.** Studio walks `GET /v1/sessions`
+  when the daemon becomes reachable and on a slow poll, and merges the result
+  into its list. A row is removed only when a COMPLETE walk proves it gone —
+  a partial walk updates what it saw and never deletes. Rows whose one
+  not-a-chat reason is `inspect_only_kind` (subagents, team members, scheduled
+  fires) are filtered by the decoder, not by id-prefix guessing.
+- **Rename is `POST …/rename`.** The local update is optimistic and rolls back
+  if the daemon refuses. Studio adopts the title the daemon actually stored,
+  which is clamped, rather than the one it asked for.
+- **Delete is `POST …/delete`.** A refusal keeps the row: the chat still
+  exists, and hiding it locally is the exact failure this ADR is about. Only a
+  404 — the daemon saying it has no such session — removes a row without a
+  witnessed walk.
+- **Opening a chat reads `GET …/transcript`.** The authoritative message-level
+  snapshot, which also covers scheduler-tick fires whose conversation never
+  reached the durable event log, and works identically in external mode. A
+  transcript the daemon cannot prove whole says so in the UI.
+- **Eligibility is the daemon's, not Studio's.** Each inventory row carries
+  `capabilities` plus a closed machine-readable reason per disabled action.
+  Studio renders the reason; it does not re-derive who may rename or delete
+  what, so tightening the rule server-side needs no client change.
+- **A new chat is a draft.** No daemon session is created until the first
+  prompt is sent; the mint happens then, and the route adopts the daemon's id.
+  Empty sessions never accumulate in the store from idle "new chat" clicks.
+
+## Consequences
+
+A chat renamed or deleted on one machine is renamed or deleted on every
+machine, and survives clearing the browser. Sessions can finally be removed
+from the store through the UI. A reload during a run no longer loses it: the
+inventory row shows the session still running on the daemon, and the
+transcript is read back when it ends.
+
+The costs, stated plainly:
+
+- **The list reorders on rename.** A rename advances the daemon's stored
+  mtime, and that mtime is the only ordering every client can agree on.
+- **A rehydrated transcript is not identical to the live one.** The transcript
+  endpoint returns the model's conversation, which includes the harness's own
+  synthetic continuations as user-role messages with no provenance to
+  distinguish them. Fixing this needs a provenance field on the daemon's
+  `ConversationMessage`, not string-sniffing in the client.
+- **Reattaching to a LIVE run rides the durable session watch.** A tab that
+  did not start the run follows it via `GET /v1/sessions/{id}/watch`
+  ([ADR 0250](./0250-durable-cursors-and-watch.md)), landing later in this
+  series. The honest residual: the driving tab's own `POST …/prompt` stream
+  still cancels the run on disconnect.
+- **Polling.** The list reconciles on an interval rather than a push, so a
+  change made elsewhere appears within seconds, not instantly.
+
+## See also
+
+- [ADR 0287](./0288-studio-atrium-module.md) — the Studio module and its
+  daemon-only posture

docs/adr/README.md

@@ -217,6 +217,7 @@ Documentation/citation conventions are in [`docs/design/README.md`](../design/RE
 - [0088 — Explicit daemon.yaml (listener topology config)](./0088-daemon-config-file.md)
 - [0222 — mecatui: ctrl+t routes by ask type; full-screen ask-args view](./0222-mecatui-ask-args-view.md)
 - [0288 — Studio: the Atrium workspace as mecatl's daemon-only web client](./0288-studio-atrium-module.md)
+- [0289 — Studio's chat list is the daemon's session store](./0289-studio-server-backed-chats.md)
 - [0247 — mecatui generated status lines](./0247-mecatui-status-line.md)
 - [0280 — Automatic light theme selection in mecatui](./0280-mecatui-light-theme-autodetect.md)
 

docs/design/PRODUCTION-READINESS.md

@@ -46,7 +46,7 @@ record; current behaviour is in the linked [architecture](../architecture.md) do
 | mecak8s (storage-free k8s-native agent) | ✅ shipped (MVP) · ✅ OPT-IN `/metrics` loopback scrape + OTLP push (ADR 0098) · ✅ verified external Redis TLS/ACL with transactional projected-file reload + last-valid generations (ADR 0240) · ✅ Helm 0.3.0 secure real-provider in-pod TLS+OIDC or edge-terminated TLS+OIDC (ClusterIP h2c), nullable spend ceilings, and pod scheduling controls · ⛔ CRD/Operator · ⛔ HPA (custom-metrics on active-runs) · ⛔ managed Redis provisioning (ElastiCache/MemoryStore — endpoint only) · ⛔ fix `mecated`'s unbounded `GracefulStop` (pre-existing, follow-up) | [mecak8s.md](../adr/0048-mecak8s.md) · [0098](../adr/0098-headless-telemetry.md) · [0240](../adr/0240-mecak8s-credential-reload-and-chart-security.md) · [0278](../adr/0278-mecak8s-edge-terminated-tls.md) · [MECAK8S-PLAN.md](./MECAK8S-PLAN.md) | [overview](../architecture.md) |
 | ACP adapter (editor stdio surface) | ✅ Phase 1+2 + bounded Phase 3 + multimodal shipped · ⛔ Phase 3 long-tail (rule persistence, grep-over-buffers, fs/* on resume) | [0001-acp-adapter.md](../adr/0001-acp-adapter.md) | [api surface](../architecture/api-surface.md) |
 | Conversation fork (peer session from a history snapshot) | ✅ shipped · ✅ effort override (mid-conversation effort switch, keeps the transcript — [0068](../adr/0068-effort-change-via-fork.md)) · ⛔ cross-provider/model fork (v2: replay-blob stripping) · ⛔ workspace-branching fork · ⛔ fork-from-event-log-at-arbitrary-point · ⛔ fork lineage (`forked_from` label) | [0065-conversation-fork.md](../adr/0065-conversation-fork.md) | [overview](../architecture.md) |
-| Studio (web client) | 🚧 landing as a stacked PR series: ✅ module foundation (vendored Atrium UI kit, root chrome, npm/Biome/knip/vitest toolchain, CI checks incl. the license-header gate) · ⛔ server tier (proxy + managed-mode controller) · ⛔ protocol seam + harness · ⛔ the five surfaces (Chats · Scheduled · Skills · Memory · Settings) · ⛔ browser e2e | [0288](../adr/0288-studio-atrium-module.md) | [overview](../architecture.md) |
+| Studio (web client) | 🚧 landing as a stacked PR series: ✅ module foundation (vendored Atrium UI kit, toolchain, CI gates) · ✅ server tier (trusted proxy + managed-mode controller core, hermetic suite) · ✅ protocol seam + harness transport · ✅ workspace shell + runtime status · ✅ Chats core + hermetic browser e2e (fixture daemon) · ⛔ Scheduled · Skills · Memory · Settings surfaces · ⛔ advanced chat tiers (attachments, steer/queue, threads, re-attach, modes, mobile) | [0288](../adr/0288-studio-atrium-module.md) · [0289](../adr/0289-studio-server-backed-chats.md) | [overview](../architecture.md) |
 | _Historical / retired_ | — | [ARCHITECTURE.md](../adr/0004-v1-architecture.md) · [STEP-CHAIN.md](../adr/0006-v1-step-chain.md) · [TWELVE-PATTERNS-AUDIT.md](../adr/0007-twelve-patterns-audit.md) · [REPOMAP-TREE-SITTER.md](../adr/0029-repomap-tree-sitter.md) | — |
 
 ## Security