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CLAUDE PLUGINS API MIGRATION WINDOW CLOSES - MOVE TO OUTPUT_CONFIG NOW
By RepoJournal · Filed · About Anthropic
The Messages API is sunsetting the top-level output_format field, and your structured outputs need to move to output_config.format before the transition period ends.
Claude plugins official just merged the security-guidance migration [1] that shifts structured output schema specification from the deprecated output_format field to the nested output_config.format field [2]. The old form still returns HTTP 200 on api-key and non-streaming auth, but that's a temporary window - the clock is ticking. This isn't optional polish. Simultaneously, the team shipped three consecutive fixes [3] [4] [5] for a critical Windows path-handling vulnerability in git invocations that bypassed quotePath protections on multiple git call sites. The latest patch moves core.quotePath=false to GIT_CMD globally rather than per-site, catching edge cases in rev-parse, reflog, and git show operations that the initial fix missed. On the infrastructure side, the defending-code reference harness got its first documentation pass [6], and the cargo-nix plugin switched test execution from runCommand to mkDerivation [7] for better extensibility and crate-root directory handling.
Action items
- → Audit all Claude plugin calls using output_format and migrate to output_config.format before transition period expires anthropics/claude-plugins-official [immediate]
- → Update git handling code to use core.quotePath=false globally via GIT_CMD if you have Windows deployments anthropics/claude-plugins-official [immediate]
- → Review defending-code reference harness docs for integration guidance anthropics/defending-code-reference-harness [plan]
References
- [1] security-guidance: migrate from deprecated output_format to output_config.format (#2098) anthropics/claude-plugins-official
- [2] Merge pull request #2105 from anthropics/fix-2098-output-config-format anthropics/claude-plugins-official
- [3] Merge pull request #2101 from anthropics/fix-2099-quotepath-global anthropics/claude-plugins-official
- [4] security-guidance: move core.quotePath=false to GIT_CMD globally (#2099 followup) anthropics/claude-plugins-official
- [5] Merge pull request #2100 from anthropics/fix-2099-text-true-pythonutf8 anthropics/claude-plugins-official
- [6] Merge pull request #1 from anthropics/mmolash/docs-updates anthropics/defending-code-reference-harness
- [7] Merge pull request #3 from Kranzes/mkdrv anthropics/cargo-nix-plugin
FAQ
- What changed in Anthropic on May 31, 2026?
- The Messages API is sunsetting the top-level output_format field, and your structured outputs need to move to output_config.format before the transition period ends.
- What should Anthropic teams do about it?
- Audit all Claude plugin calls using output_format and migrate to output_config.format before transition period expires • Update git handling code to use core.quotePath=false globally via GIT_CMD if you have Windows deployments • Review defending-code reference harness docs for integration guidance
- Which Anthropic repositories shipped on May 31, 2026?
- anthropics/claude-plugins-official, anthropics/defending-code-reference-harness, anthropics/cargo-nix-plugin