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Claude Code v2.1.216

Credential Sentinels Now Substituted in Request Bodies

What

Masked credential sentinels (set up via sandbox.credentials.envVars) are now replaced with their real values in outgoing request bodies as well as headers. A streaming Transform walks the body for sentinel byte sequences and swaps them in place.

Details
  • Only applies to methods that send a body (POST, PUT, PATCH, etc.)
  • Skipped for requests with Content-Encoding headers (compressed bodies cannot be substituted safely; a warning is logged)
  • If any sentinel differs in length from its real value, the content-length header is removed so the stream can change size
  • Only sentinels where sentinel length equals real-value length preserve content-length intact
Evidence

Body substitution transform (search for "[body-substitution]" or "substitution skipped — a sentinel in this body").

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

See this entry in the whole of v2.1.216 →