diff --git a/api/main.py b/api/main.py
index 7bf6be0..c148db3 100644
--- a/api/main.py
+++ b/api/main.py
@@ -114,6 +114,51 @@ class HealthResponse(BaseModel):
     preserve_dev_data: Optional[bool] = None
 
 
+class ReasoningMessage(BaseModel):
+    """Individual message in a reasoning conversation."""
+    message_index: int
+    role: str
+    content: str
+    summary: Optional[str] = None
+    tool_name: Optional[str] = None
+    tool_input: Optional[str] = None
+    timestamp: str
+
+
+class PositionSummary(BaseModel):
+    """Trading position summary."""
+    action_id: int
+    action_type: Optional[str] = None
+    symbol: Optional[str] = None
+    amount: Optional[int] = None
+    price: Optional[float] = None
+    cash_after: float
+    portfolio_value: float
+
+
+class TradingSessionResponse(BaseModel):
+    """Single trading session with positions and optional conversation."""
+    session_id: int
+    job_id: str
+    date: str
+    model: str
+    session_summary: Optional[str] = None
+    started_at: str
+    completed_at: Optional[str] = None
+    total_messages: Optional[int] = None
+    positions: List[PositionSummary]
+    conversation: Optional[List[ReasoningMessage]] = None
+
+
+class ReasoningResponse(BaseModel):
+    """Response body for GET /reasoning."""
+    sessions: List[TradingSessionResponse]
+    count: int
+    deployment_mode: str
+    is_dev_mode: bool
+    preserve_dev_data: Optional[bool] = None
+
+
 def create_app(
     db_path: str = "data/jobs.db",
     config_path: str = "/tmp/runtime_config.json" if Path("/tmp/runtime_config.json").exists() else "configs/default_config.json"
@@ -482,6 +527,182 @@ def create_app(
             logger.error(f"Failed to query results: {e}", exc_info=True)
             raise HTTPException(status_code=500, detail=f"Internal server error: {str(e)}")
 
+    @app.get("/reasoning", response_model=ReasoningResponse)
+    async def get_reasoning(
+        job_id: Optional[str] = Query(None, description="Filter by job ID"),
+        date: Optional[str] = Query(None, description="Filter by date (YYYY-MM-DD)"),
+        model: Optional[str] = Query(None, description="Filter by model signature"),
+        include_full_conversation: bool = Query(False, description="Include full conversation history")
+    ):
+        """
+        Query reasoning logs from trading sessions.
+
+        Supports filtering by job_id, date, and/or model.
+        Returns session summaries with positions and optionally full conversation history.
+
+        Args:
+            job_id: Optional job UUID filter
+            date: Optional date filter (YYYY-MM-DD)
+            model: Optional model signature filter
+            include_full_conversation: Include all messages (default: false, only returns summaries)
+
+        Returns:
+            List of trading sessions with positions and optional conversation
+
+        Raises:
+            HTTPException 400: Invalid date format
+            HTTPException 404: No sessions found matching filters
+        """
+        try:
+            # Validate date format if provided
+            if date:
+                try:
+                    datetime.strptime(date, "%Y-%m-%d")
+                except ValueError:
+                    raise HTTPException(
+                        status_code=400,
+                        detail=f"Invalid date format: {date}. Expected YYYY-MM-DD"
+                    )
+
+            conn = get_db_connection(app.state.db_path)
+            cursor = conn.cursor()
+
+            # Build query for trading sessions with filters
+            query = """
+                SELECT
+                    ts.id,
+                    ts.job_id,
+                    ts.date,
+                    ts.model,
+                    ts.session_summary,
+                    ts.started_at,
+                    ts.completed_at,
+                    ts.total_messages
+                FROM trading_sessions ts
+                WHERE 1=1
+            """
+            params = []
+
+            if job_id:
+                query += " AND ts.job_id = ?"
+                params.append(job_id)
+
+            if date:
+                query += " AND ts.date = ?"
+                params.append(date)
+
+            if model:
+                query += " AND ts.model = ?"
+                params.append(model)
+
+            query += " ORDER BY ts.date, ts.model"
+
+            cursor.execute(query, params)
+            session_rows = cursor.fetchall()
+
+            if not session_rows:
+                conn.close()
+                raise HTTPException(
+                    status_code=404,
+                    detail="No trading sessions found matching the provided filters"
+                )
+
+            sessions = []
+            for session_row in session_rows:
+                session_id = session_row[0]
+
+                # Fetch positions for this session
+                cursor.execute("""
+                    SELECT
+                        p.action_id,
+                        p.action_type,
+                        p.symbol,
+                        p.amount,
+                        p.price,
+                        p.cash,
+                        p.portfolio_value
+                    FROM positions p
+                    WHERE p.session_id = ?
+                    ORDER BY p.action_id
+                """, (session_id,))
+
+                position_rows = cursor.fetchall()
+                positions = [
+                    PositionSummary(
+                        action_id=row[0],
+                        action_type=row[1],
+                        symbol=row[2],
+                        amount=row[3],
+                        price=row[4],
+                        cash_after=row[5],
+                        portfolio_value=row[6]
+                    )
+                    for row in position_rows
+                ]
+
+                # Optionally fetch full conversation
+                conversation = None
+                if include_full_conversation:
+                    cursor.execute("""
+                        SELECT
+                            rl.message_index,
+                            rl.role,
+                            rl.content,
+                            rl.summary,
+                            rl.tool_name,
+                            rl.tool_input,
+                            rl.timestamp
+                        FROM reasoning_logs rl
+                        WHERE rl.session_id = ?
+                        ORDER BY rl.message_index
+                    """, (session_id,))
+
+                    message_rows = cursor.fetchall()
+                    conversation = [
+                        ReasoningMessage(
+                            message_index=row[0],
+                            role=row[1],
+                            content=row[2],
+                            summary=row[3],
+                            tool_name=row[4],
+                            tool_input=row[5],
+                            timestamp=row[6]
+                        )
+                        for row in message_rows
+                    ]
+
+                sessions.append(
+                    TradingSessionResponse(
+                        session_id=session_row[0],
+                        job_id=session_row[1],
+                        date=session_row[2],
+                        model=session_row[3],
+                        session_summary=session_row[4],
+                        started_at=session_row[5],
+                        completed_at=session_row[6],
+                        total_messages=session_row[7],
+                        positions=positions,
+                        conversation=conversation
+                    )
+                )
+
+            conn.close()
+
+            # Get deployment mode info
+            deployment_info = get_deployment_mode_dict()
+
+            return ReasoningResponse(
+                sessions=sessions,
+                count=len(sessions),
+                **deployment_info
+            )
+
+        except HTTPException:
+            raise
+        except Exception as e:
+            logger.error(f"Failed to query reasoning logs: {e}", exc_info=True)
+            raise HTTPException(status_code=500, detail=f"Internal server error: {str(e)}")
+
     @app.get("/health", response_model=HealthResponse)
     async def health_check():
         """
diff --git a/tests/unit/test_api_reasoning_endpoint.py b/tests/unit/test_api_reasoning_endpoint.py
new file mode 100644
index 0000000..68b280f
--- /dev/null
+++ b/tests/unit/test_api_reasoning_endpoint.py
@@ -0,0 +1,317 @@
+"""
+Unit tests for GET /reasoning API endpoint.
+
+Coverage target: 95%+
+
+Tests verify:
+- Filtering by job_id, date, and model
+- Full conversation vs summaries only
+- Error handling (404, 400)
+- Deployment mode info in responses
+"""
+
+import pytest
+from datetime import datetime
+from api.database import get_db_connection
+
+
+@pytest.fixture
+def sample_trading_session(clean_db):
+    """Create a sample trading session with positions and reasoning logs."""
+    conn = get_db_connection(clean_db)
+    cursor = conn.cursor()
+
+    # Create job
+    cursor.execute("""
+        INSERT INTO jobs (job_id, config_path, status, date_range, models, created_at)
+        VALUES (?, ?, ?, ?, ?, ?)
+    """, (
+        "test-job-123",
+        "configs/test.json",
+        "completed",
+        '["2025-10-02"]',
+        '["gpt-5"]',
+        "2025-10-02T10:00:00Z"
+    ))
+
+    # Create trading session
+    cursor.execute("""
+        INSERT INTO trading_sessions (job_id, date, model, session_summary, started_at, completed_at, total_messages)
+        VALUES (?, ?, ?, ?, ?, ?, ?)
+    """, (
+        "test-job-123",
+        "2025-10-02",
+        "gpt-5",
+        "Analyzed AI infrastructure market. Bought NVDA and GOOGL based on secular AI trends.",
+        "2025-10-02T10:00:00Z",
+        "2025-10-02T10:05:23Z",
+        4
+    ))
+
+    session_id = cursor.lastrowid
+
+    # Create positions linked to session
+    cursor.execute("""
+        INSERT INTO positions (
+            job_id, date, model, action_id, action_type, symbol, amount, price,
+            cash, portfolio_value, daily_profit, daily_return_pct, session_id, created_at
+        )
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+    """, (
+        "test-job-123", "2025-10-02", "gpt-5", 1, "buy", "NVDA", 10, 189.60,
+        8104.00, 10000.00, 0.0, 0.0, session_id, "2025-10-02T10:05:00Z"
+    ))
+
+    cursor.execute("""
+        INSERT INTO positions (
+            job_id, date, model, action_id, action_type, symbol, amount, price,
+            cash, portfolio_value, daily_profit, daily_return_pct, session_id, created_at
+        )
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+    """, (
+        "test-job-123", "2025-10-02", "gpt-5", 2, "buy", "GOOGL", 6, 245.15,
+        6633.10, 10104.00, 104.00, 1.04, session_id, "2025-10-02T10:05:10Z"
+    ))
+
+    # Create reasoning logs
+    cursor.execute("""
+        INSERT INTO reasoning_logs (session_id, message_index, role, content, summary, timestamp)
+        VALUES (?, ?, ?, ?, ?, ?)
+    """, (
+        session_id, 0, "user",
+        "Please analyze and update today's (2025-10-02) positions.",
+        None,
+        "2025-10-02T10:00:00Z"
+    ))
+
+    cursor.execute("""
+        INSERT INTO reasoning_logs (session_id, message_index, role, content, summary, timestamp)
+        VALUES (?, ?, ?, ?, ?, ?)
+    """, (
+        session_id, 1, "assistant",
+        "Key intermediate steps\n\n- Read yesterday's positions...",
+        "Analyzed market conditions and decided to buy NVDA (10 shares) and GOOGL (6 shares).",
+        "2025-10-02T10:05:20Z"
+    ))
+
+    cursor.execute("""
+        INSERT INTO reasoning_logs (session_id, message_index, role, content, summary, tool_name, tool_input, timestamp)
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?)
+    """, (
+        session_id, 2, "tool",
+        "Successfully bought 10 shares of NVDA at $189.60",
+        None,
+        "trade",
+        '{"action": "buy", "symbol": "NVDA", "amount": 10}',
+        "2025-10-02T10:05:21Z"
+    ))
+
+    cursor.execute("""
+        INSERT INTO reasoning_logs (session_id, message_index, role, content, summary, tool_name, tool_input, timestamp)
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?)
+    """, (
+        session_id, 3, "tool",
+        "Successfully bought 6 shares of GOOGL at $245.15",
+        None,
+        "trade",
+        '{"action": "buy", "symbol": "GOOGL", "amount": 6}',
+        "2025-10-02T10:05:22Z"
+    ))
+
+    conn.commit()
+    conn.close()
+
+    return {
+        "session_id": session_id,
+        "job_id": "test-job-123",
+        "date": "2025-10-02",
+        "model": "gpt-5"
+    }
+
+
+@pytest.fixture
+def multiple_sessions(clean_db):
+    """Create multiple trading sessions for testing filters."""
+    conn = get_db_connection(clean_db)
+    cursor = conn.cursor()
+
+    # Create job
+    cursor.execute("""
+        INSERT INTO jobs (job_id, config_path, status, date_range, models, created_at)
+        VALUES (?, ?, ?, ?, ?, ?)
+    """, (
+        "test-job-456",
+        "configs/test.json",
+        "completed",
+        '["2025-10-03", "2025-10-04"]',
+        '["gpt-5", "claude-4"]',
+        "2025-10-03T10:00:00Z"
+    ))
+
+    # Session 1: gpt-5, 2025-10-03
+    cursor.execute("""
+        INSERT INTO trading_sessions (job_id, date, model, session_summary, started_at, completed_at, total_messages)
+        VALUES (?, ?, ?, ?, ?, ?, ?)
+    """, (
+        "test-job-456", "2025-10-03", "gpt-5",
+        "Session 1 summary", "2025-10-03T10:00:00Z", "2025-10-03T10:05:00Z", 2
+    ))
+    session1_id = cursor.lastrowid
+
+    # Session 2: claude-4, 2025-10-03
+    cursor.execute("""
+        INSERT INTO trading_sessions (job_id, date, model, session_summary, started_at, completed_at, total_messages)
+        VALUES (?, ?, ?, ?, ?, ?, ?)
+    """, (
+        "test-job-456", "2025-10-03", "claude-4",
+        "Session 2 summary", "2025-10-03T10:00:00Z", "2025-10-03T10:05:00Z", 2
+    ))
+    session2_id = cursor.lastrowid
+
+    # Session 3: gpt-5, 2025-10-04
+    cursor.execute("""
+        INSERT INTO trading_sessions (job_id, date, model, session_summary, started_at, completed_at, total_messages)
+        VALUES (?, ?, ?, ?, ?, ?, ?)
+    """, (
+        "test-job-456", "2025-10-04", "gpt-5",
+        "Session 3 summary", "2025-10-04T10:00:00Z", "2025-10-04T10:05:00Z", 2
+    ))
+    session3_id = cursor.lastrowid
+
+    # Add positions for each session
+    for session_id, date, model in [(session1_id, "2025-10-03", "gpt-5"),
+                                     (session2_id, "2025-10-03", "claude-4"),
+                                     (session3_id, "2025-10-04", "gpt-5")]:
+        cursor.execute("""
+            INSERT INTO positions (
+                job_id, date, model, action_id, action_type, symbol, amount, price,
+                cash, portfolio_value, session_id, created_at
+            )
+            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+        """, (
+            "test-job-456", date, model, 1, "buy", "AAPL", 5, 250.00,
+            8750.00, 10000.00, session_id, f"{date}T10:05:00Z"
+        ))
+
+    conn.commit()
+    conn.close()
+
+    return {
+        "job_id": "test-job-456",
+        "session_ids": [session1_id, session2_id, session3_id]
+    }
+
+
+@pytest.mark.unit
+class TestGetReasoningEndpoint:
+    """Test GET /reasoning endpoint."""
+
+    def test_get_reasoning_with_job_id_filter(self, client, sample_trading_session):
+        """Should return sessions filtered by job_id."""
+        response = client.get(f"/reasoning?job_id={sample_trading_session['job_id']}")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["count"] == 1
+        assert len(data["sessions"]) == 1
+        assert data["sessions"][0]["job_id"] == sample_trading_session["job_id"]
+        assert data["sessions"][0]["date"] == sample_trading_session["date"]
+        assert data["sessions"][0]["model"] == sample_trading_session["model"]
+        assert data["sessions"][0]["session_summary"] is not None
+        assert len(data["sessions"][0]["positions"]) == 2
+
+    def test_get_reasoning_with_date_filter(self, client, multiple_sessions):
+        """Should return sessions filtered by date."""
+        response = client.get("/reasoning?date=2025-10-03")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["count"] == 2  # Both gpt-5 and claude-4 on 2025-10-03
+        assert all(s["date"] == "2025-10-03" for s in data["sessions"])
+
+    def test_get_reasoning_with_model_filter(self, client, multiple_sessions):
+        """Should return sessions filtered by model."""
+        response = client.get("/reasoning?model=gpt-5")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["count"] == 2  # gpt-5 on both dates
+        assert all(s["model"] == "gpt-5" for s in data["sessions"])
+
+    def test_get_reasoning_with_full_conversation(self, client, sample_trading_session):
+        """Should include full conversation when requested."""
+        response = client.get(
+            f"/reasoning?job_id={sample_trading_session['job_id']}&include_full_conversation=true"
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["count"] == 1
+
+        session = data["sessions"][0]
+        assert session["conversation"] is not None
+        assert len(session["conversation"]) == 4  # 1 user + 1 assistant + 2 tool messages
+
+        # Verify message structure
+        messages = session["conversation"]
+        assert messages[0]["role"] == "user"
+        assert messages[0]["message_index"] == 0
+        assert messages[0]["summary"] is None
+
+        assert messages[1]["role"] == "assistant"
+        assert messages[1]["message_index"] == 1
+        assert messages[1]["summary"] is not None
+
+        assert messages[2]["role"] == "tool"
+        assert messages[2]["message_index"] == 2
+        assert messages[2]["tool_name"] == "trade"
+        assert messages[2]["tool_input"] is not None
+
+    def test_get_reasoning_summaries_only(self, client, sample_trading_session):
+        """Should not include conversation when include_full_conversation=false (default)."""
+        response = client.get(f"/reasoning?job_id={sample_trading_session['job_id']}")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["count"] == 1
+
+        session = data["sessions"][0]
+        assert session["conversation"] is None
+        assert session["session_summary"] is not None
+        assert session["total_messages"] == 4
+
+    def test_get_reasoning_no_results_returns_404(self, client, clean_db):
+        """Should return 404 when no sessions match filters."""
+        response = client.get("/reasoning?job_id=nonexistent-job")
+
+        assert response.status_code == 404
+        assert "No trading sessions found" in response.json()["detail"]
+
+    def test_get_reasoning_invalid_date_returns_400(self, client, clean_db):
+        """Should return 400 for invalid date format."""
+        response = client.get("/reasoning?date=invalid-date")
+
+        assert response.status_code == 400
+        assert "Invalid date format" in response.json()["detail"]
+
+    def test_get_reasoning_includes_deployment_mode(self, client, sample_trading_session):
+        """Should include deployment mode info in response."""
+        response = client.get(f"/reasoning?job_id={sample_trading_session['job_id']}")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert "deployment_mode" in data
+        assert "is_dev_mode" in data
+        assert isinstance(data["is_dev_mode"], bool)
+
+
+@pytest.fixture
+def client(clean_db):
+    """Create FastAPI test client with clean database."""
+    from fastapi.testclient import TestClient
+    from api.main import create_app
+
+    app = create_app(db_path=clean_db)
+    app.state.test_mode = True  # Prevent background worker from starting
+
+    return TestClient(app)