update

docs/spec.md

@@ -647,6 +647,41 @@ function fileserver_download_handler(
 
 ---
 
+## Implementation Files
+
+| File | Platform | Features | Notes |
+|------|----------|----------|-------|
+| [`src/NATSBridge.jl`](../src/NATSBridge.jl) | Julia | Full feature set, Arrow IPC, multiple dispatch | Ground truth implementation |
+| [`src/natsbridge_ssr.js`](../src/natsbridge_ssr.js) | Node.js | Arrow IPC, async/await | Server-side JavaScript |
+| [`src/natsbridge_csr.js`](../src/natsbridge_csr.js) | Browser | JSON table only, WebSocket NATS | Client-side rendering |
+| [`src/natsbridge.py`](../src/natsbridge.py) | Python | Arrow IPC, async/await | Desktop Python |
+| [`src/natsbridge_mpy.py`](../src/natsbridge_mpy.py) | MicroPython | Limited to direct transport | Memory-constrained |
+
+### Browser Implementation Notes
+
+The browser implementation ([`src/natsbridge_csr.js`](../src/natsbridge_csr.js)) has the following constraints:
+
+| Constraint | Reason | Workaround |
+|------------|--------|------------|
+| No Apache Arrow IPC | Browser-incompatible dependency | Use `jsontable` for tabular data |
+| WebSocket NATS only | Browser cannot use TCP directly | Use `ws://` or `wss://` broker URLs |
+| Fetch API for HTTP | Browser fetch() API only | Compatible with Plik and other HTTP servers |
+
+### Payload Type Availability by Platform
+
+| Payload Type | Julia | Node.js | Browser | Python | MicroPython |
+|--------------|-------|---------|---------|--------|-------------|
+| `text` | ✅ | ✅ | ✅ | ✅ | ✅ |
+| `dictionary` | ✅ | ✅ | ✅ | ✅ | ✅ |
+| `arrowtable` | ✅ | ✅ | ❌ | ✅ | ❌ |
+| `jsontable` | ✅ | ✅ | ✅ | ✅ | ⚠️ |
+| `image` | ✅ | ✅ | ✅ | ✅ | ✅ |
+| `audio` | ✅ | ✅ | ✅ | ✅ | ✅ |
+| `video` | ✅ | ✅ | ✅ | ✅ | ✅ |
+| `binary` | ✅ | ✅ | ✅ | ✅ | ✅ |
+
+---
+
 ## Message Flow
 
 ### Sending Flow