fix: Address PR #206 review feedback for OpenAI thinking mode

[guunergooner]

Summary

Fixes review feedback from #206:

• afterEach env var leak: Use delete instead of assigning undefined when original env var was undefined, preventing state leak between tests
• Turn boundary detection for multimodal inputs: Treat non-text user inputs (e.g., images) as new turns, not just text content — fixes reasoning_content not being stripped for multimodal-only turns
• Improved test coverage: Extract buildOpenAIRequestBody() from queryModelOpenAI for testability; replace constant-assertion tests with real function output verification

Test plan

• All 94 OpenAI tests pass (0 fail)
• thinking.test.ts: 36 tests pass (was 20, now covers request body params)
• convertMessages.test.ts: 22 tests pass

Signed-off-by: guunergooner tongchao0923@gmail.com

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added support for OpenAI thinking mode to enable extended reasoning during model processing.
  • Automatic thinking mode activation for DeepSeek reasoner models.
  • Configurable thinking mode via environment-based control.

• Tests

  • Added test coverage for thinking mode functionality and multi-turn conversation behavior.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

This PR adds "thinking" mode support for OpenAI, particularly for DeepSeek reasoner models. It introduces helper functions to detect thinking enablement via environment variables or model name patterns, extends message conversion logic to preserve Anthropic thinking blocks as reasoning_content when thinking is enabled, and centralizes OpenAI request body construction with conditional thinking parameters.

Changes

Cohort / File(s)	Summary
Test Coverage src/services/api/openai/__tests__/convertMessages.test.ts, src/services/api/openai/__tests__/thinking.test.ts	New test suites validating isOpenAIThinkingEnabled() detection across environment variables and model names (DeepSeek reasoner/v3.2 variants), buildOpenAIRequestBody() with conditional thinking parameters, and anthropicMessagesToOpenAI() thinking block preservation/stripping behavior across message turns.
Message Conversion Logic src/services/api/openai/convertMessages.ts	Added ConvertMessagesOptions interface with enableThinking flag; extended anthropicMessagesToOpenAI() to accept options parameter and compute turn boundaries; modified assistant message conversion to preserve thinking blocks as reasoning_content when thinking is enabled.
OpenAI Service Core src/services/api/openai/index.ts	Added isOpenAIThinkingEnabled() helper for thinking mode detection via environment variable or model name auto-detection; added buildOpenAIRequestBody() helper that centralizes request construction with conditional DeepSeek thinking parameters; refactored queryModelOpenAI() to use new helpers.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~50 minutes

Poem

🐰 Whiskers twitch with delight divine,
As thinking thoughts now intertwine—
DeepSeek reasoners find their voice,
Wrapped in reasoning, a thoughtful choice!
✨ Hop forth with contentment fine! 🌟

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 57.14% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title 'fix: Address PR #206 review feedback for OpenAI thinking mode' clearly and specifically describes the main change: addressing review feedback for OpenAI thinking mode implementation.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[guunergooner]

Changes merged into #206 as a single commit.