## Summary
- Added Codex subscription-login onboarding as a first-class provider path.
- Hardened the OpenAI-compatible runtime path and improved request handling.
- Fixed two user-facing protocol bugs: Gemini thought-signature replay on newer thinking models and Signal duplicate-field payload parsing.
- Refreshed docs and release surfaces to match the current stable line.

## Breaking Changes
- None.

## Migration Steps
- No manual migration is required for the stable path from `v0.2.x` to `v0.3.0`.
- As usual before upgrading, create a backup:
  - `cara backup --output ./carapace-backup.tar.gz`
- After upgrade, verify the install:
  - `cara verify --outcome auto`
  - `cara verify --outcome autonomy`

## Rollback Steps
- Reinstall the previous known-good binary, for example `v0.2.0`.
- Restore the backup created before upgrade:
  - `cara restore --path ./carapace-backup.tar.gz`
- Re-run:
  - `cara status --port 18789`
  - `cara verify --outcome auto --port 18789`
  - `cara verify --outcome autonomy --port 18789`

## Security
- Preserved Gemini/Vertex `thoughtSignature` metadata across turns so newer Gemini thinking-model tool loops continue to work correctly.
- Tightened CI and dependency surfaces with current workflow/dependency updates.
- Continued fail-closed updater/release-signing path remains in effect for published artifacts.

## Verification
- Verify published artifacts and Sigstore bundles:
  - `RELEASE_TAG=v0.3.0 ./scripts/smoke/verify-release-artifacts.sh`
- Use pinned release URLs in automation and production environments.

## Known Caveats
- Anthropic, Bedrock, and Vertex onboarding work is still in progress beyond the newly shipped Codex path.
- Filesystem tool TOCTOU limitations remain documented accepted risk in the current cross-platform pathname-based design.
