Retry incomplete caption requests across processor slots

[devhims]

Summary

• retry empty, partial caption-track results through an alternate processor slot
• retry transcript NOT_FOUND responses through an alternate processor slot
• preserve genuine empty caption results and terminal transcript 404s after all slots agree
• keep unrelated resource 404s non-retryable

Root cause

YouTube can transiently return a playable player response without its caption catalog. The processor previously exposed that as either an empty partial 200 or a transcript 404, while the Worker only failed over on 502, 503, and 504. A healthy alternate processor slot was therefore never attempted.

Impact

Caption and transcript requests can recover transparently when one processor session receives an incomplete YouTube response, without changing the public contract for genuinely captionless videos.

Validation

• npm --prefix platform run build
• npm --prefix platform test
• focused processor-client regression suite: 9 tests passed
• full platform suite: 184 tests passed
• processor container suite: 7 tests passed
• git diff --check

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Project	Deployment	Actions	Updated (UTC)
video2ctx-web	Ready	Preview	Aug 19, 2026 10:19am