fix: use ANTHROPIC_DEFAULT_OPUS_MODEL env var for model selection

[simfor99]

Summary

• Fixed hardcoded model in chat session services that ignored ANTHROPIC_DEFAULT_OPUS_MODEL environment variable
• Now reads model from env var with fallback to default claude-opus-4-5-20251101
• Enables alternative API providers (e.g., GLM via z.ai, synthetic.new) to work correctly

Changes

Modified 3 files to read model from environment:

• server/services/expand_chat_session.py
• server/services/spec_chat_session.py
• server/services/assistant_chat_session.py

Problem

The model was hardcoded to "claude-opus-4-5-20251101", causing API errors when using alternative providers that don't support Claude model names.

Example error from Issue #51:

API Error: 400 {"error":"Your model name should start with an hf: prefix..."}

Solution

# Before
model="claude-opus-4-5-20251101",

# After
model = os.getenv("ANTHROPIC_DEFAULT_OPUS_MODEL", "claude-opus-4-5-20251101")

Test plan

• Verified fix applies to all three chat session services
• Test with alternative API provider (GLM/z.ai)
• Test default behavior (no env var set)

Fixes #51

🤖 Generated with Claude Code

Summary by CodeRabbit

Release Notes

• Chores
  • Updated chat session services to support dynamic AI model configuration through environment variables, enabling different model variants to be used without code changes.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Three chat session services are updated to dynamically read the Claude model name from the ANTHROPIC_DEFAULT_OPUS_MODEL environment variable instead of hardcoding it, enabling runtime model selection and support for alternative API backends.

Changes

Cohort / File(s)	Summary
Dynamic Model Configuration server/services/assistant_chat_session.py, server/services/expand_chat_session.py, server/services/spec_chat_session.py	Each file now reads ANTHROPIC_DEFAULT_OPUS_MODEL from environment (defaults to "claude-opus-4-5-20251101") and passes the resolved model name to ClaudeSDKClient instead of using hardcoded model strings. Enables alternative API model selection without code changes.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 Three services hop in sync,
Reading models from the .env brink,
No more hardcoded names in sight,
Alternative APIs now run just right!
Environment variables make things tight! 🎉

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	The PR partially addresses issue #51 by implementing environment variable support for ANTHROPIC_DEFAULT_OPUS_MODEL in three service files, but does not implement ANTHROPIC_DEFAULT_SONNET_MODEL and ANTHROPIC_DEFAULT_HAIKU_MODEL environment variables mentioned in the issue.	Complete the fix by also implementing ANTHROPIC_DEFAULT_SONNET_MODEL and ANTHROPIC_DEFAULT_HAIKU_MODEL environment variables in all relevant service files to fully resolve issue #51.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: using ANTHROPIC_DEFAULT_OPUS_MODEL environment variable for dynamic model selection instead of hardcoded values across three service files.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to implementing environment variable support for model selection across three chat session service files, with no unrelated modifications detected.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

---

🧹 Recent nitpick comments

server/services/assistant_chat_session.py (1)

158-164: Consider updating the docstring to reflect configurable model.

The class docstring mentions "Uses Claude Opus 4.5" but the model is now configurable via ANTHROPIC_DEFAULT_OPUS_MODEL. Consider generalizing this to avoid confusion.

📝 Suggested docstring update

 class AssistantChatSession:
     """
     Manages a read-only assistant conversation for a project.

-    Uses Claude Opus 4.5 with only read-only tools enabled.
+    Uses Claude (model configurable via ANTHROPIC_DEFAULT_OPUS_MODEL) with only read-only tools enabled.
     Persists conversation history to SQLite.
     """

📜 Recent review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 07c2010 and bc7970f.

📒 Files selected for processing (3)

• server/services/assistant_chat_session.py
• server/services/expand_chat_session.py
• server/services/spec_chat_session.py

🧰 Additional context used

📓 Path-based instructions (1)

**/*.py

📄 CodeRabbit inference engine (CLAUDE.md)

Use SQLite with SQLAlchemy ORM for database access and feature management

Files:

• server/services/spec_chat_session.py
• server/services/assistant_chat_session.py
• server/services/expand_chat_session.py

🧠 Learnings (1)

📚 Learning: 2026-01-10T08:23:04.012Z

Learnt from: CR
Repo: leonvanzyl/autocoder PR: 0
File: CLAUDE.md:0-0
Timestamp: 2026-01-10T08:23:04.012Z
Learning: Applies to *.py : Python backend should use the ClaudeSDKClient configuration in client.py with security hooks and MCP servers

Applied to files:

• server/services/spec_chat_session.py
• server/services/expand_chat_session.py

🔇 Additional comments (3)

server/services/expand_chat_session.py (1)

170-178: LGTM! Environment-driven model selection implemented correctly.

The change correctly reads the model from ANTHROPIC_DEFAULT_OPUS_MODEL with an appropriate fallback. The comment helpfully explains the rationale for alternative API support.

server/services/spec_chat_session.py (1)

172-179: LGTM! Consistent with the pattern used in other chat sessions.

The implementation correctly mirrors the approach in expand_chat_session.py, ensuring uniform behavior across all chat session services.

server/services/assistant_chat_session.py (1)

258-265: LGTM! Environment-driven model selection implemented correctly.

The change is consistent with the other chat session services and correctly enables alternative API backend support.

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[leonvanzyl]

Thank you