The "do request → check err → defer close → forward headers → set
status → io.Copy → log mid-stream errors" tail was duplicated between
Upload and Download. Each handler had ~12 lines that differed only in:
- the op label in log messages ("upload" vs "download")
- the set of response headers to forward verbatim
(Upload: Content-Type only; Download: Content-Type +
Content-Length + Content-Disposition)
Hoist into ChatFilesHandler.streamWorkspaceResponse(c, op,
workspaceID, forwardURL, req, forwardHeaders). Each call site
reduces to one line. Future changes — request-id forwarding,
observability metric, response-size cap, bytes-streamed log —
go in ONE place rather than two.
Same drift-prevention rationale as resolveWorkspaceForwardCreds
(#2372) and readOrLazyHealInboundSecret (#2376), applied to the
response-streaming layer of the same handlers.
Behavior preserved: existing TestChatUpload_* and TestChatDownload_*
integration tests (8 across both handlers) all pass unchanged. The
log message format is consistent across both handlers now (single
"chat_files {op}: ..." string template) — operators can grep one
prefix for both features instead of separate prefixes per handler.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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