Wiring Probe Plan — Pi 4 ↔ RG40XXV Real-Time Bridge

# On Pi:
ping -c 20 100.119.202.114

# Expected: <10ms average over Tailscale mesh
# If >50ms: polling approach may feel laggy. Consider streaming.

# SSH into Pi
python3 --version
pip3 list | grep -E "fastapi|flask|requests|aiohttp|langgraph"
# What's already installed? What needs pip?

# RG runs a test script:
import requests, time
start = time.time()
r = requests.post("http://100.120.38.37:8000/ping", json={"test": "hello"}, timeout=5)
elapsed = time.time() - start
print(f"Roundtrip: {elapsed*1000:.0f}ms, response: {r.json()}")

# Pi runs a minimal FastAPI server:
from fastapi import FastAPI
app = FastAPI()
@app.post("/ping")
async def ping(data: dict):
    return {"pong": data}

# RG fetches a mock state of 36 nodes + 3 units
r = requests.get("http://100.120.38.37:8000/state")
elapsed = time.time() - start
state = r.json()
print(f"Fetch: {elapsed*1000:.0f}ms, payload: {len(r.content)} bytes, nodes: {len(state['nodes'])}")

# RG invokes a node (moves a unit), then polls until state changes
old_state = get_state()
invoke({"unit": "rif", "action": "move", "target": "17"})
while True:
    new_state = get_state()
    if new_state["nodes"]["17"]["status"] != old_state["nodes"]["17"]["status"]:
        break  # state changed — node completed
    time.sleep(0.5)
# Total time from invoke to state update visible

# LangGraph checkpointer automatically saves after every super-step
# No explicit "save" needed — state is always persisted

# Player can also create a named checkpoint:
graph.put_state(config, {"checkpoint_name": "Before design review"})

# Later: time-travel to that checkpoint
state = graph.get_state(config, checkpoint_id="Before design review")

Save → RG takes screenshot (640×480 pygame surface → PNG)
     → RG writes save metadata: {hex, unit, turn, timestamp}
     → RG sends "create checkpoint" to Pi → Pi names the checkpoint
     → RG shows: "Saved. Checkpoint: Turn 4, Rif at Hex 17."

┌─────────────────────────────────────────────────────────┐
│  RG40XXV                    │  Pi 4                      │
│                             │                            │
│  Wargame Engine             │  FastAPI (port 8000)       │
│  ├── Event loop             │  ├── GET  /state           │
│  ├── Hex grid rendering     │  │    → returns full state  │
│  ├── Sprite management      │  ├── POST /invoke          │
│  ├── Input → messaging      │  │    → runs graph, returns │
│  │   └── on_click(hex)      │  │      updated state      │
│  │       → POST /invoke     │  ├── POST /checkpoint      │
│  │       → poll GET /state  │  │    → creates named save  │
│  │       → re-render        │  ├── GET  /health          │
│  └── Save button            │  │    → connectivity check  │
│      → screenshot PNG       │  └── LangGraph graph       │
│      → POST /checkpoint     │      ├── 36 nodes          │
│                             │      ├── SqliteSaver        │
│                             │      └── Agent calls        │
└─────────────────────────────────────────────────────────┘

10 packets, 0% loss
min: 3.1ms | avg: 8.6ms | max: 49.6ms (first ping only)
Steady state: 3-5ms