chore(exp24): launch exp24, fix logging setup, update handoff

- Exp23 complete (mean 2000 steps / 408.6r, high variance confirms nose-first stuck issue)
- Unity 6000.4.4f1 rebuild done: Assembly-CSharp.dll updated with Car.cs raycast fix
- Rsync'd to runtime folder, sim restarted on port 9091
- Exp24 launched (PID 733053) — discrete(7), speed stuck, road regen
- Fix logging.basicConfig no-op: use file_log.addHandler() directly
- Monitor via /tmp/exp24.out (log file was 0 bytes with old approach)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

agent/SESSION_HANDOFF.md

@@ -1,6 +1,6 @@
 # RL Donkeycar Session Handoff
 
-Last updated: 2026-05-05 America/Toronto (updated during exp23)
+Last updated: 2026-05-05 20:09 America/Toronto (updated during exp24 launch)
 
 ## Autonomy Instruction
 
@@ -12,11 +12,12 @@ If the user says only `continue`, interpret it using the instruction above.
 
 ## Current Goal
 
-Run exp24 on `generated_road` with:
-- Discrete steering (7 bins) — smoother, less oscillation than continuous
-- Speed-based stuck detection — catches car pressed nose-first against barrier
-- Road regeneration — sim reconnects between segments so each eval is a fresh road
-- Unity raycast fix — Car.cs detects nose-first barrier contact via forward raycast
+Monitor exp24 on `generated_road`. All setup complete and running.
+
+- **Exp24 is RUNNING** (PID 733053) since 20:09 on 2026-05-05
+- Log: `agent/models/exp24-discrete/run_2026-05-05_200903_discrete.log`
+- All fixes are in effect: discrete steering (7 bins), speed-based stuck detection,
+  road regeneration, Unity raycast fix compiled into Assembly-CSharp.dll (20:05)
 
 ## Important Paths
 
@@ -101,29 +102,29 @@ to Unity physics non-determinism, NOT road variety.
 
 ## Current State
 
-### Exp 23 status
-- Running (PID 649531), at ~140k/200k steps as of last check
-- Will finish on its own — DO NOT kill it
-- Log: `agent/models/exp23-generated-road-clean/run_2026-05-05_160718_clean.log`
+### Exp 23 status — COMPLETE
+- Finished at 18:12 on 2026-05-05
+- Final mean: 2000 steps / 408.6 reward
+- High variance throughout: some crashes in 105–171 steps (nose-first barrier),
+  others ran 1684–1951 steps. Best eval: 403.8r / 2000s ✅ at ~40k steps.
+- This confirmed the nose-first stuck issue that exp24 is designed to fix.
 
-### Unity build status
-- **Needs rebuild** — Car.cs raycast fix not yet compiled
-- Car.cs was modified at:
-  `/mnt/c/Users/Paul/Documents/projects/sdsandbox/sdsim/Assets/Scripts/Car.cs`
+### Unity build status — DONE
+- Rebuilt with Unity 6000.4.4f1 at ~20:05 on 2026-05-05
+- Assembly-CSharp.dll updated: includes Car.cs forward raycast fix
+- Rsync'd to: `/mnt/c/Users/Paul/Downloads/DonkeySimWin/DonkeySimWin/`
+- Sim restarted on port 9091 with new binary
 
-### To launch exp24
-
-1. Wait for exp23 to finish (or confirm it has)
-2. Rebuild Unity (Car.cs raycast fix)
-3. Stop sim on port 9091
-4. Rsync build to runtime folders (both, or just the one on 9091)
-5. Restart sim on port 9091
-6. Launch exp24:
+### Exp 24 status — RUNNING
+- PID 733053, launched at 20:09 on 2026-05-05
+- Log: `agent/models/exp24-discrete/run_2026-05-05_200903_discrete.log`
+- Monitor with:
   ```bash
-   cd /home/paulh/projects/donkeycar-rl-autoresearch/agent
-   nohup python3 experiments/exp24_generated_road_discrete.py > /tmp/exp24.out 2>&1 &
-   tail -f /home/paulh/projects/donkeycar-rl-autoresearch/agent/models/exp24-discrete/run_*_discrete.log
+  tail -f /tmp/exp24.out
   ```
+  NOTE: The log file (run_*_discrete.log) is 0 bytes — logging.basicConfig() is a
+  no-op because gym_donkeycar already configured the root logger. All output goes
+  to /tmp/exp24.out via nohup. Fix in exp25: use `file_log.addHandler(FileHandler(...))` directly.
 
 ## Useful Commands
 
@@ -169,13 +170,19 @@ grep "Eval\|BEST" agent/models/exp23-generated-road-clean/run_2026-05-05_160718_
 
 ## Notes for Next Session
 
-- Unity rebuild is required before exp24 — Car.cs raycast fix won't be in effect
-  until the build is done and synced.
+- Unity rebuild is DONE. No rebuild needed unless Car.cs or other scripts change.
+- Assembly-CSharp.dll confirmed in runtime folder. Port 9091 sim uses new binary.
 - The second sim (port 9093) is not needed — only port 9091.
-- Do NOT kill exp23 — let it run to completion.
+- Exp24 is running. DO NOT kill it. Let it run to 200k steps.
 - Exp24's road regeneration adds ~5s per checkpoint = ~100s extra total. This is
   by design. The "Reconnecting for fresh road" log lines confirm it's working.
 - `info['speed']` from telemetry = `rb.velocity.magnitude / 8.0`. The
   `LOW_SPEED_THRESHOLD=0.5` corresponds to 4 Unity m/s, which is slow but not zero.
   A truly stuck car reads ~0.0. Tight corners might temporarily be 0.1–0.3.
   The 2-second timer provides enough grace for normal slow driving.
+- Unity version used: 6000.4.4f1 (NOT 2020.3.x — the project is on Unity 6).
+  Build command: `"/mnt/c/Program Files/Unity/Hub/Editor/6000.4.4f1/Editor/Unity.exe"
+  -quit -batchmode -projectPath "C:/Users/Paul/Documents/projects/sdsandbox/sdsim"
+  -executeMethod PlayerBuilder.WinBuild -logFile "C:/Users/Paul/AppData/Local/Temp/unity_rebuild.log"`
+- To kill/restart sim from WSL2: `taskkill.exe` is at `/mnt/c/Windows/System32/taskkill.exe`
+  (not in PATH — use full path). Restart: `/mnt/c/Windows/System32/cmd.exe /c start "" "C:\...\donkey_sim.exe" --port 9091`

agent/experiments/exp24_generated_road_discrete.py

@@ -168,12 +168,17 @@ log_path          = os.path.join(_SAVE_DIR, f'run_{run_tag}.log')
 best_model_path   = os.path.join(_SAVE_DIR, 'best_model.zip')
 
 import logging
-logging.basicConfig(
-    level=logging.INFO,
-    format='%(message)s',
-    handlers=[logging.FileHandler(log_path), logging.StreamHandler(sys.stdout)],
-)
+# logging.basicConfig is a no-op if the root logger already has handlers (e.g. from
+# gym_donkeycar/SB3 imports). Add handlers directly to avoid silent file-log loss.
+_file_handler = logging.FileHandler(log_path)
+_file_handler.setFormatter(logging.Formatter('%(message)s'))
+_stream_handler = logging.StreamHandler(sys.stdout)
+_stream_handler.setFormatter(logging.Formatter('%(message)s'))
 file_log = logging.getLogger('exp24')
+file_log.setLevel(logging.INFO)
+file_log.propagate = False
+file_log.addHandler(_file_handler)
+file_log.addHandler(_stream_handler)
 
 
 def flog(msg):