fix: eliminate event-loop-blocking sync calls in async FastAPI routes (#106)

* feat: add async DB wrapper and eliminate event-loop blocking

* fix: rewrite llm_client.py with native async httpx - removes urlopen and run_in_executor

* fix: rewrite routes/coach.py - replace all sync DB/HTTP with async (aiosqlite + httpx)

* fix: add async DB shutdown hook to lab_api.py

* feat: add aiosqlite>=0.19.0 to requirements

services/async_db.py

@@ -0,0 +1,220 @@
+"""Async SQLite wrapper for FastAPI — eliminates event-loop blocking.
+
+Drop-in async replacements for the sync helpers in services/database.py.
+Uses aiosqlite under the hood so every DB call yields back to the
+event loop instead of freezing it.
+
+Usage in route handlers:
+    from services.async_db import async_get_db, async_execute, async_fetchall
+
+    rows = await async_fetchall("SELECT * FROM decks")
+    row  = await async_fetchone("SELECT * FROM decks WHERE id = ?", (1,))
+    await async_execute("INSERT INTO ...", params)
+    await async_execute_commit("DELETE FROM ...", params)
+"""
+from __future__ import annotations
+
+import json
+import logging
+from pathlib import Path
+from typing import Any, Optional
+
+import aiosqlite
+
+log = logging.getLogger("commander_ai_lab.async_db")
+
+# Re-use the same DB path as the sync module
+COLLECTION_DB_PATH = Path(__file__).parent.parent / "collection.db"
+
+# Module-level connection (lazy-init, one per process)
+_aconn: Optional[aiosqlite.Connection] = None
+
+
+async def async_get_db() -> aiosqlite.Connection:
+    """Return (or create) the module-level async SQLite connection."""
+    global _aconn
+    if _aconn is None:
+        _aconn = await aiosqlite.connect(str(COLLECTION_DB_PATH))
+        _aconn.row_factory = aiosqlite.Row
+        await _aconn.execute("PRAGMA journal_mode=WAL")
+        log.info("Async SQLite connection opened: %s", COLLECTION_DB_PATH)
+    return _aconn
+
+
+async def async_close_db() -> None:
+    """Close the module-level connection (call on shutdown)."""
+    global _aconn
+    if _aconn is not None:
+        await _aconn.close()
+        _aconn = None
+        log.info("Async SQLite connection closed.")
+
+
+# ── Convenience helpers ─────────────────────────────────────────
+
+async def async_fetchall(
+    sql: str, params: tuple = (), *, conn: aiosqlite.Connection = None
+) -> list[dict]:
+    """Execute a SELECT and return all rows as dicts."""
+    db = conn or await async_get_db()
+    async with db.execute(sql, params) as cursor:
+        columns = [d[0] for d in cursor.description]
+        rows = await cursor.fetchall()
+        return [dict(zip(columns, row)) for row in rows]
+
+
+async def async_fetchone(
+    sql: str, params: tuple = (), *, conn: aiosqlite.Connection = None
+) -> Optional[dict]:
+    """Execute a SELECT and return one row as a dict (or None)."""
+    db = conn or await async_get_db()
+    async with db.execute(sql, params) as cursor:
+        columns = [d[0] for d in cursor.description]
+        row = await cursor.fetchone()
+        return dict(zip(columns, row)) if row else None
+
+
+async def async_execute(
+    sql: str, params: tuple = (), *, conn: aiosqlite.Connection = None
+) -> int:
+    """Execute a write statement. Returns lastrowid."""
+    db = conn or await async_get_db()
+    cursor = await db.execute(sql, params)
+    return cursor.lastrowid
+
+
+async def async_execute_commit(
+    sql: str, params: tuple = (), *, conn: aiosqlite.Connection = None
+) -> int:
+    """Execute a write statement and commit. Returns lastrowid."""
+    db = conn or await async_get_db()
+    cursor = await db.execute(sql, params)
+    await db.commit()
+    return cursor.lastrowid
+
+
+async def async_executemany_commit(
+    sql: str, params_seq, *, conn: aiosqlite.Connection = None
+) -> None:
+    """Execute many and commit."""
+    db = conn or await async_get_db()
+    await db.executemany(sql, params_seq)
+    await db.commit()
+
+
+async def async_commit(*, conn: aiosqlite.Connection = None) -> None:
+    """Commit the current transaction."""
+    db = conn or await async_get_db()
+    await db.commit()
+
+
+# ── JSON field helpers (mirrors database._row_to_dict) ──────────
+
+_JSON_FIELDS = ("category", "color_identity", "subtypes", "keywords")
+
+
+def row_to_dict_parsed(row: dict) -> dict:
+    """Parse JSON string columns into Python lists (same as database._row_to_dict)."""
+    if row is None:
+        return None
+    d = dict(row)
+    for f in _JSON_FIELDS:
+        if f in d and isinstance(d[f], str):
+            try:
+                d[f] = json.loads(d[f])
+            except (json.JSONDecodeError, TypeError):
+                d[f] = []
+    return d
+
+
+# ── Coach session async helpers ─────────────────────────────────
+
+async def async_save_coach_session(session_data: dict) -> int:
+    """Insert or update a coach session. Returns row id."""
+    db = await async_get_db()
+    existing = await async_fetchone(
+        "SELECT id FROM coach_sessions WHERE session_id = ?",
+        (session_data["session_id"],),
+    )
+    if existing:
+        await db.execute(
+            """UPDATE coach_sessions SET
+                deck_id=?, timestamp=?, model_used=?, prompt_tokens=?,
+                completion_tokens=?, summary=?, goals_json=?, cuts_json=?,
+                adds_json=?, heuristic_hints_json=?, mana_base_advice=?,
+                raw_text=?
+            WHERE session_id=?""",
+            (
+                session_data.get("deck_id", ""),
+                session_data.get("timestamp", ""),
+                session_data.get("model_used", ""),
+                session_data.get("prompt_tokens", 0),
+                session_data.get("completion_tokens", 0),
+                session_data.get("summary", ""),
+                session_data.get("goals_json", "{}"),
+                session_data.get("cuts_json", "[]"),
+                session_data.get("adds_json", "[]"),
+                session_data.get("heuristic_hints_json", "[]"),
+                session_data.get("mana_base_advice", ""),
+                session_data.get("raw_text", ""),
+                session_data["session_id"],
+            ),
+        )
+        await db.commit()
+        return existing["id"]
+    else:
+        cursor = await db.execute(
+            """INSERT INTO coach_sessions
+                (session_id, deck_id, timestamp, model_used, prompt_tokens,
+                 completion_tokens, summary, goals_json, cuts_json, adds_json,
+                 heuristic_hints_json, mana_base_advice, raw_text)
+            VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?)""",
+            (
+                session_data["session_id"],
+                session_data.get("deck_id", ""),
+                session_data.get("timestamp", ""),
+                session_data.get("model_used", ""),
+                session_data.get("prompt_tokens", 0),
+                session_data.get("completion_tokens", 0),
+                session_data.get("summary", ""),
+                session_data.get("goals_json", "{}"),
+                session_data.get("cuts_json", "[]"),
+                session_data.get("adds_json", "[]"),
+                session_data.get("heuristic_hints_json", "[]"),
+                session_data.get("mana_base_advice", ""),
+                session_data.get("raw_text", ""),
+            ),
+        )
+        await db.commit()
+        return cursor.lastrowid
+
+
+async def async_load_coach_session(session_id: str) -> Optional[dict]:
+    """Load a single coach session by session_id."""
+    return await async_fetchone(
+        "SELECT * FROM coach_sessions WHERE session_id = ?", (session_id,)
+    )
+
+
+async def async_list_coach_sessions(deck_id: str = None) -> list[dict]:
+    """List coach sessions, optionally filtered by deck_id."""
+    if deck_id:
+        return await async_fetchall(
+            "SELECT session_id, deck_id, timestamp, summary, created_at "
+            "FROM coach_sessions WHERE deck_id = ? ORDER BY timestamp DESC",
+            (deck_id,),
+        )
+    return await async_fetchall(
+        "SELECT session_id, deck_id, timestamp, summary, created_at "
+        "FROM coach_sessions ORDER BY timestamp DESC"
+    )
+
+
+async def async_delete_coach_session(session_id: str) -> bool:
+    """Delete a coach session. Returns True if a row was deleted."""
+    db = await async_get_db()
+    cursor = await db.execute(
+        "DELETE FROM coach_sessions WHERE session_id = ?", (session_id,)
+    )
+    await db.commit()
+    return cursor.rowcount > 0