The dashboard's card thumbnail image, streamed same-origin.
Streams the newest usable whole-dashboard PNG render for the dashboard's current version — a small default-viewport (1280×800) screenshot kept fresh by a background sweeper (DVT-1205), never wider than 25 days old. The API fetches the artifact from R2 itself and streams the bytes back same-origin, so the dashboards page card grid never needs the object-storage host in img-src — the R2 host is deliberately NOT allowlisted there; see web/src/media-safety.ts ALLOWED_MEDIA_HOSTS and the lockstep assertion in web/src/csp.test.ts (no CSP change). Supports conditional GET via If-None-Match/ETag (the render id). Returns 404 when no thumbnail-eligible render exists yet (e.g. a brand-new dashboard the sweeper hasn't reached) or the R2 object is no longer available — callers should fall back to a placeholder, not treat it as an error.
An optional ?revision=N (DVT-1466 stage 3) pins the lookup to a specific past revision instead of the dashboard's current version — used by the activity feed's before/after edit thumbnails (ActivityEvent.beforeThumbUrl/afterThumbUrl). Resolves to the newest succeeded render at or before revision N (nearest-older fallback, same 25-day artifact horizon); still never re-renders — a missing artifact is a 404, not a fresh render of old history (ADR-0011).
An optional ?page=P (DVT-1483, 0-based) prefers a succeeded render of that page at or before the resolved revision over the sweeper's page-0 render, which previously always won regardless of which page was edited. Falls back to the page-0 render (never a 404) when page P has no qualifying artifact yet. Only takes effect alongside ?revision=N — ?page=P with no ?revision= is accepted (validated, never 400) but has no effect on the current-version lookup, which is always the sweeper's page-0 render.
Request
- Base URL: http://localhost:8080
- URL: http://localhost:8080/v1/dashboards/{id}/thumbnail
- Auth: one of:
- API key in cookie dvt_session
- HTTP bearer
Query parameters
Pin the lookup to this revision (or the newest succeeded render at or before it) instead of the dashboard's current version. Must be a positive integer; a non-integer or value < 1 is rejected with 400.
Prefer a render of this 0-based page over the page-0 default when resolving ?revision=N (DVT-1483); falls back to the page-0 render when no page-P render qualifies. Must be a non-negative integer; a non-integer or negative value is rejected with 400. No effect without ?revision=N.
Headers
Conditional-GET revalidation tag (DVT-3724). Unlike the shared If-None-Match semantics elsewhere in this API, this route compares the supplied value EXACTLY against the current quoted, strong render-id ETag — no W/-prefix weakening, no comma-separated list, no * wildcard. An exact match yields 304; anything else gets a normal 200 with a fresh ETag.
Response
The thumbnail PNG bytes.
Changes
No recorded changes to this operation across all 1 revision of this API.