Fix: Prevent memory leak in responses.parse with bounded TypeAdapter …

[ishanrajsingh]

Description

Fixes memory leak in responses.parse() caused by unbounded TypeAdapter caching in multi-threaded environments.

Problem

The current implementation uses an unbounded lru_cache keyed by dynamically generated generic types (ParsedResponseOutputMessage[MyClass]). In multi-threaded scenarios, Pydantic regenerates these types with different hashes, preventing cache hits and causing infinite memory growth.

Solution

1. Bounded Cache: Limit cache size to 128 entries per thread
2. Stable Keys: Use fully-qualified type names instead of type object hashes
3. Thread Safety: Implement thread-local caching to prevent conflicts

Changes

• Added src/openai/lib/_parsing/_type_adapter_cache.py with thread-safe caching
• Modified src/openai/lib/_parsing/_completions.py to use new cache
• Added comprehensive tests in tests/test_type_adapter_cache.py

Testing

• Unit tests pass
• Memory leak reproduction test passes
• Multi-threaded scenarios tested
• No performance regression

Closes

Fixes #2672

Checklist

• Tests added/updated
• Documentation updated (if needed)
• Follows project coding standards