phase: 110_fix_sse_db_pool_exhaustion

---

**Phase 110 — Fix SSE DB Connection Pool Exhaustion (SEC-14-04): COMPLETE**

**What was implemented/verified:**
- All three tasks (pool config, short-lived sessions, concurrency cap) were already implemented in code
- Fixed `tests/integration/test_chat_db_sessions.py` — added FakeChatLLM mock, fixed LLM signature (`tools=` not `_tools=`), used `fastapi_app.dependency_overrides` instead of `client.app.dependency_overrides`
- Fixed `tests/e2e/test_chat_db_pool.py` — added FakeChatLLM mock, fixed admin password to match `tests/conftest.py`, removed unused imports
- Fixed lint errors (unused imports, import order) in both test files

**Test / lint / coverage results:**
- `uv run pytest` → 2350 passed, 1 warning, 56.4s
- `uv run pytest --cov=app --cov-report=term-missing` → 99% coverage (4065 lines, 16 uncovered)
- `uv run pytest tests/e2e/test_chat_db_pool.py -v --no-cov` → 3 passed
- `uv run pytest tests/integration/test_chat_db_sessions.py -v --no-cov` → 4 passed
- `uv run pytest tests/integration/test_chat_concurrency.py -v --no-cov` → 11 passed
- `uv run pytest tests/unit/test_db_pool_config.py -v --no-cov` → 14 passed
- `uv run pytest tests/unit/test_agent_short_lived_sessions.py -v --no-cov` → 7 passed
- `uv run ruff check .` → all checks passed
- `uv run pyright` → 0 errors, 0 warnings

**Completion criteria:**
- [✓] `app/db.py::create_engine` receives explicit `pool_size=5`, `max_overflow=10`, `pool_recycle=3600` from settings
- [✓] `run_agent` accepts `db_factory: Callable[[], Session]` and creates short-lived sessions per tool call
- [✓] Each tool round uses a separate DB session closed after the tool result
- [✓] Concurrency cap (`BOR_CHAT_MAX_CONCURRENT`, default 10) limits concurrent turns; excess get 503
- [✓] All test gates green, coverage 99%, lint/types clean

**Notable decisions:** Tests needed LLM mocking (the original test files lacked `FakeChatLLM` mocks, causing hangs on real LLM calls).

**Next pending phase:** None — this is the last phase in `todo/`.

.env.example

@@ -15,6 +15,10 @@ BOR_ENVIRONMENT=development
 
 # --- Database (matches `podman compose` db service) ---
 BOR_DATABASE_URL=postgresql+psycopg://reese:reese@localhost:5432/brain_of_reese
+# BOR_DB_POOL_SIZE=5              # connection pool size (SEC-14-04, default 5)
+# BOR_DB_POOL_MAX_OVERFLOW=10     # max overflow connections (SEC-14-04, default 10)
+# BOR_DB_POOL_RECYCLE=3600        # recycle connections after N seconds (SEC-14-04, default 3600)
+# BOR_CHAT_MAX_CONCURRENT=10      # max concurrent /api/chat turns (SEC-14-04, default 10)
 
 # --- LLM (self-hosted, OpenAI-compatible "aipi") ---
 BOR_LLM_BASE_URL=https://aipi.reeseapps.com/v1