[selfcontained]

Problem

On a host with ~28k blocks, chat streams took 2–7 s to load. The feed's open-input lookup (FAILED_PARENT_INPUT_SQL in apps/server/src/chat/feed.ts, used by listOpenInputs and listBlockEntries) compared answer.id::text to the stored blockId. Postgres can't use blocks_pkey for that comparison, so it scanned every block once per parent-handled ask. One measured stream did 1,046 inner seq scans and took 6.94 s; that query accounted for 4.1 s of a 4.17 s composeStreamFeed call.

Fix

Compare answer.id as a uuid. Only canonical lowercase ids are cast, which is the same set the text comparison could match, so a malformed blockId still matches nothing instead of failing the query.

Validation

• New test: the failed-parent answer still shows as an open input, a malformed blockId doesn't break the feed, and with enable_seqscan = off the plan uses blocks_pkey on blocks answer. The test fails when the old ::text comparison is restored.
• Read-only EXPLAIN ANALYZE on a local production DB (20k blocks): 55.8 ms → 0.18 ms. On the slow host, a diagnostic version of this query ran in about 2 ms, against 6.94 s for the original.
• pnpm run check, plus vitest on stream-service.test.ts and test/chat: 299 passed.

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