Root Cause

Problem

When extracting changes from a messy PR, I blindly copied a fix to retry.py without questioning whether it was needed.

The signature preservation fix was for pydantic-ai tool schema generation. retry_on_json_error is a JSON parsing utility - it never gets passed to pydantic-ai's Tool(). The fix there was a shim.

Root Cause

Cargo culting. "The original PR had it, so I included it."

Lesson

Before applying any fix, ask: "Does this code path actually hit the problem?"

For the signature preservation bug specifically:

• pydantic-ai uses inspect.signature() to generate JSON schemas for tools
• Only wrappers that produce functions passed to Tool() need the fix
• retry_on_json_error wraps JSON parsers, not pydantic-ai tools

Rule

If you encounter a shim, fix it. Don't care who made it. Don't propagate it.

Files That Actually Needed The Fix

1. research_agent.py - ProgressTracker.wrap_tool() wraps tools for pydantic-ai
2. decorators.py - base_tool() and file_tool() wrap tools for pydantic-ai
3. present_plan.py - create_present_plan_tool() creates a pydantic-ai tool

Files That Did NOT Need The Fix

• retry.py - wraps JSON parsers, not pydantic-ai tools