The console sends ETags back and patches lease renewals in place #916

Part of #905.

Scope

The console sends back the ETag of each route's last answer, so an unchanged answer costs no download and no re-render. A lease renewal updates the lease's deadline in place, with no read.

In short

An idle page's polls mostly come back 304 Not Modified. A renewal moves the lease's "ends in" time at once on the Leases page and on its worker's page, with no request. When that lease was in the Inbox as ending, or its drawer is open, that data is read once, in the same burst window as any event.

flowchart LR
  Q[query read] --> A["ApiClient.get + If-None-Match (new)"]
  A -->|304| K[keep last data]
  A -->|200| N[new data + tag]
  E[lease.renewed] --> P["patch ttlDeadline (new)"]

If it goes wrong: a lease shows an old deadline, or a page shows data older than the server's.

Technical spec

Facts

Modules touched

ui/src/data/api.ts (get(path, { tag }): with a tag it returns { notModified: true, date } on 304 or { body, date, tag } on 200; without one its return type stays ApiResponse<T> so getJson and mode.ts are unchanged), ui/src/data/live/connection.ts (read passes the tag; a 304 corrects the offset from its Date and counts as the daemon answering, F8), the ApiClient fakes (ui/src/state/test-support.tsx, ui/src/data/live/test-support.ts), every console browser stub that calls route.fetch() (F9: it drops If-None-Match before fetching, so the stub always edits a full answer), ui/src/state/queries.ts (keeps the last tag per key; on 304 returns the cached data object), ui/src/model/renewal.ts (new, pure: the match rule, proven through the query-layer tests), ui/src/state/queries.ts event handling for lease.renewed, api.test.ts and queries.test.ts. Searches: api.get(, getJson( (the latter keeps no tag), lease.renewed in ui/src (none today).

Contract and event changes

None. Reads If-None-Match/ETag (#919) and workerLeaseId (#913).

Other code on the same state

• The event map (The console reads per page through a query cache, and events mark data stale #914) maps lease.renewed to no key; this task adds the patch beside it.
• A read of ['leases'] or ['workers'] can land after a patch with the old deadline (F7). The console keeps each renewal's deadline for 60 s and applies it to every later answer: a record's ttlDeadline is the later of the answer's and the kept one.
• The worker page reads leases from ['workers'] (F6): the patch applies there too, matched by the event's workerId (gateway) and the worker's own lease id.
• lastRenewedAt becomes the event's timestamp and ttlMs becomes newDeadline − timestamp (F10).
  Searches: setQueryData, ttlDeadline in ui/src/state (hits in leases.ts, inbox.ts).

Failure modes

Rules in play

• ADR 0044 §2 (renewals) and §3 (ETag): complies.

Tests

Seams: ui/src/data/api.test.ts for the client; the query layer of #914 (ui/src/state/queries.test.ts) for the cache, its observers built with the same options as useRouteQuery.

• A re-read of an unchanged route: the second read sends the first tag; 304 → the observer gets the same data object and no update; 200 → new data; 304 after the data was dropped → one read without a tag.
• A renewal patches its lease: worker event (no workerId) matches by id; gateway event matches workerId + workerLeaseId in ['leases'] and workerId + lease id in ['workers']; lastRenewedAt and ttlMs follow; a later answer with the old deadline keeps the new one; no match → no change; 20 renewals of ending leases in 1 s → one inbox read; ['lease', id] observed → one read; otherwise no request.

Done when

• pnpm vitest run ui/src passes with the new tests.
• The console browser lane passes with the stubs of F9 dropping If-None-Match.

Out of scope

Patching any other event's data in place.

Depends on

• Unchanged JSON answers under /v1 are 304 with an ETag #919
• One lease is read directly, and gateway leases name the worker's lease id #913
• The console reads per page through a query cache, and events mark data stale #914 (its query layer, event map and burst window) (decided in delivery, accepted by the maintainer 2026-10-23)
• The daemon says what needs the operator: GET /v1/inbox #915 (its inbox with the ending item) (decided in delivery, accepted by the maintainer 2026-10-23)
• The daemon says what needs the operator: GET /v1/inbox #915

Written by an agent.