The previous commit's fix was too broad in one direction: excluding ALL CC-compatible relays from the native-Claude header block broke two pre-existing tests (cc-compatible-provider.test.ts, v3.6.6) that rely on that treatment for a 'vanilla' relay with no providerSpecificData.requestDefaults configured.
Refines the gate to this whole native-Claude header-replacement block: replace headers for real claude traffic, agentrouter's wire-image mimicry, OR a CC-relay with no requestDefaults at all — only a relay with EXPLICIT requestDefaults (context1m/redactThinking/summarizeThinking) gets to keep buildHeaders()'s own correctly-computed header set. A redact-thinking-beta strip (unconditional, a no-op when native treatment didn't apply) covers the one remaining gap: selectBetaFlags() force-includes it for a bare relay's opaque client, which a bare relay never explicitly opted into.
Verified against all three previously-conflicting pre-existing tests simultaneously: executor-default-base.test.ts's '1M beta' test, both cc-compatible-provider.test.ts SSE-forcing tests, and provider-request-failure-pipeline.test.ts's 'keeps request beta headers' test (the last of which was already broken by the raw agentrouter merge, confirmed via direct comparison against that exact commit).
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