[patrickbrandao]

Part of #105. Items 1 to 3 already landed in #107 (adapter headers win with a case-insensitive merge, invalid values rejected, accept/accept-encoding blocked); items 4 and 5 in #106. This PR does the optional backend nits from the #107 review.

What changed

• mergeExtraHeaders compared caller header names after trimming but emitted the untrimmed key. It now emits the trimmed name, and skips a blank name. (No current caller passes padded keys; the Playground sanitizer already trims.)
• ForwardOptions.extraHeaders documents that the adapter's headers win, with anthropic-beta appended instead.

The dashboard nits (shared validators, popover help text, live region reset, row warnings, <Index> regression test) are frontend.

Tests

• npx jest src/routing/proxy/__tests__/extra-headers src/playground: 225 passed (3 new cases).
• Full backend unit run: see comment below / results in the report.
• eslint on changed files: clean.

qa-docker: not needed (no observable change for current callers).

🤖 Generated with Claude Code

[patrickbrandao]

Full backend unit run (npx jest --maxWorkers=4): 9085/9087 passed; the 2 failures were timing-sensitive tests under machine load (score-request-advanced 1000-requests-in-500ms, secret-reencryption), unrelated to this diff, and pass in isolation (30/30).

[patrickbrandao]

Review: #154 fix(providers): emit trimmed extra header names and document adapter precedence

Reviewed git diff origin/main...7d8497c.

Blockers: none. Should-fix: none.

Checks

• packages/backend/src/routing/proxy/extra-headers.ts:44,57: the forwarded name is now the trimmed one, which is the name it was deduplicated by. A blank name is dropped. The adapter's headers (including auth) still win in any casing or padding, and anthropic-beta is still appended. A padded ' Authorization ' cannot override the adapter's credential, because the comparison was already trimmed.
• The change is on the proxy hot path and unit tests cover it (padding, case collision, blank name). It does not change error handling.
• No changeset. Acceptable: callers that send correct names see no change.
• CI on 7d8497c: all green. Docker build (linux/amd64) failed on an npm ECONNRESET and passed on rerun.
• qa-docker: not needed (agreed).

Head revisado: 7d8497c
Veredito: aprovado