Summary

• What changed:
  • Removed event-driven reasoning stripping in two user flows where history is restored or model context changes.
  • Updated regression expectations to assert reasoning/thought content is preserved in those flows.
• Why it changed:
  • Align with maintainer decision in BUG: DeepSeek API 400 error — reasoning_content in thinking mode must be passed back #3579: strip-on-event was identified as the wrong fix direction and should be removed.
• Reviewer focus:
  • Confirm no thought stripping occurs in the targeted flows.
  • Confirm regression tests now enforce preservation behavior.

Validation

• Commands run:

  cd packages/core && npx vitest run src/config/config.test.ts
  cd packages/cli && npx vitest run src/ui/hooks/slashCommandProcessor.test.ts

• Prompts / inputs used:
  • Model-switch flow regression expectation.
  • History-load flow regression expectation.
• Expected result:
  • Targeted tests pass and preserve-reasoning assertions hold.
• Observed result:
  • Both test files passed locally (98/98, 39/39).
• Quickest reviewer verification path:
  • Run the two commands above.
• Evidence (output, logs, screenshots, video, JSON, before/after, etc.):
  • Vitest outputs show all targeted tests passing.

Scope / Risk

• Main risk or tradeoff:
  • Strict provider wire-format compatibility is not handled by history mutation anymore.
• Not covered / not validated:
  • Provider-specific request-boundary sanitization work is not part of this PR.
• Breaking changes / migration notes:
  • None intended.

Testing Matrix

Testing matrix notes:

• Verified with targeted npx vitest run in Linux environment only.

Linked Issues / Bugs

• Related: BUG: DeepSeek API 400 error — reasoning_content in thinking mode must be passed back #3579
• Related: Bug: Switching models mid-session causes API failures. #3304
• Related: Deepseek V4 调用错误 API Error: 400 和 reasoning_content有关 #3619