The #6199/#6561 commentary-phase filter (shouldDropResponsesCommentaryEvent)
was wired only into createSSEStream's PASSTHROUGH branch. The TRANSLATE-mode
loop (openai-responses upstream -> another client format, e.g. codex routes
streaming into Claude Code) called translateResponse() on every raw chunk
without checking phase, so internal commentary-phase scratchpad text leaked
into the client-visible content channel as duplicate prose and narrated
tool-call arguments.
Extends the same stateful filter into TRANSLATE mode via a small factory
(createTranslateCommentaryFilter) that owns its own item/index Sets, keeping
the wiring in stream.ts (a frozen file) to a single guarded line.
Fail->pass evidence:
- tests/unit/repro-6952-commentary.test.ts against origin/HEAD (pre-fix):
FAILED - "commentary-phase prose must not reach the translated client stream"
- Same test against the fix: PASSED (2/2)
94328d5cb2