fix(dashboard-api): tolerate evicted unresolved attempts during pixel chat result retrieval

[vaibhavsrv]

Why this matters

In ods/extensions/services/dashboard-api/routers/pixel.py, pixel_chat_result(...) queries durable attempt receipts for an owner via _result_state(store, key). If an attempt's state is "unresolved" (for example, after a worker crash or process restart), the handler calls pixel_chat_activity(...) to check whether the underlying run reached a terminal state, marks it interrupted via store.finish(key, "interrupted"), and re-queries the attempt row with row = store.get(key).

If the attempt row was evicted by retention policies, store capacity bounds, or concurrently purged between the terminal transition and store.get(key), row becomes None. The handler subsequently attempted to evaluate events = b"" if row["state"] == "active" else ..., which raised an unhandled TypeError: 'NoneType' object is not subscriptable and failed the endpoint with HTTP 500.

This surgical fix guards row following the unresolved terminal reconciliation check, returning {"state": "unknown", "events": ""} if the attempt row is no longer present in the store.

Validation

• Baseline reproduction: Tested retrieval of an unresolved attempt where the row was evicted after being marked interrupted on unpatched pixel.py; baseline crashed with TypeError: 'NoneType' object is not subscriptable.
• Post-fix behavior: Handler safely handles missing/evicted rows, returning {"state": "unknown", "events": ""}; all 20 chat result tests pass cleanly.
• Telemetry: pixel chat result suites: 20 passed. New-test syntax and diff checks pass; new regressions wired into test suite.

Overlap check

• fix(pixel-teams): stream UTF-8 chunks incrementally without splitting multi-byte sequences #5698 (fix(pixel-teams): stream UTF-8 chunks incrementally without splitting multi-byte sequences): Addresses agent team SSE streaming decoder; zero overlap with chat result retrieval in pixel.py.
• fix(pixel-settings): convert decode and protocol failures to unsafe-settings-source #5697 (fix(pixel-settings): convert decode and protocol failures to unsafe-settings-source): Hardens settings coordinator source parsing; zero overlap with chat results store.
• fix(pixel-settings): reject active token limits exceeding provider capacity #5696 (fix(pixel-settings): reject active token limits exceeding provider capacity): Enforces capability invariants in contract.py; zero overlap with chat result handlers.
• fix(dashboard-api): tolerate evicted or missing attempts during pixel chat cancel #5695 (fix(dashboard-api): tolerate evicted or missing attempts during pixel chat cancel): Hardened pixel_chat_cancel against missing attempts; this PR complements that protection for pixel_chat_result.

Risk / AI disclosure

AI-assisted investigation, implementation and CLI regressions. This strengthens missing-row null-safety in the chat result endpoint and does not alter store semantics or contract formats. Independent human review and platform/runtime qualification remain gates. No running configuration, deployment or upstream merge changed.

Follow-up integration evidence

Composed with #5698 at 35ec0d4e0 without conflicts. Production and test diffs passed together; result store and cancellation checks remain intact.
Backlog composition was local-only (production/test diffs, excluding workflow/Makefile wiring); it is not an upstream merge or independent human approval. Declared live-review gates remain open.

[Lightheartdevs]

Thanks for this contribution. public-beta was promoted into main on 2026-09-24 and no longer receives changes, so we're closing pull requests that target it. This isn't a judgment on the change itself. If it's still needed, please rebase onto main and open a focused PR. See #7253 for details and the contribution policy.