[chiragjangiir]

Closes #102

Root Cause

MemoryBlock._ensure_loaded() in session/memory.py used an unprotected check-then-act pattern:

if not self._loaded:
    self._cache = store.get_memory(...)
    ...
    self._loaded = True

When multiple worker threads call get(), all(), or as_prompt_block() concurrently on the same MemoryBlock instance (such as in multi-worker sessions sharing memory blocks), both threads could enter the branch before self._loaded was set to True. This resulted in duplicate SQLite queries, duplicate ProjectMemory.load() calls, and redundant upserts.

Changes

1. Added self._load_lock = threading.Lock() in MemoryBlock.__init__.
2. Wrapped _ensure_loaded() using double-checked locking:
   • Early return if self._loaded is already True (zero lock contention on subsequent reads).
   • Acquire self._load_lock and verify not self._loaded before loading and populating self._cache.
3. Added test_ensure_loaded_concurrent_single_load in tests/test_phase12.py to verify that concurrent calls to _ensure_loaded() across multiple threads only call store.get_memory and pm.load exactly once.

Verification

• Ran test suite:

  python -m pytest tests/test_phase12.py tests/test_project_memory_concurrency.py

  All 32 tests passed.
• Ran linter:

  ruff check devagent/session/memory.py tests/test_phase12.py

  Passed with 0 violations.