# Binary Hub Protocol (wire) — TODO

## Priority legend
- **P0** blocker · **P1** important · **P2** nice-to-have · **P3** idea

---

## TODO-01: SegmentBufferReader isolated unit tests
**Priority:** P1 · **Type:** Test coverage

Original `vast-brewing-moonbeam` refactor plan (chunked receive-path) listed these tests in its verification section; they were never written. Needed:
- `Write` / `TryAdvanceSegment` / `Complete` basic contract
- Producer-consumer concurrency (grow-buffer handoff race)
- Missed-signal double-check pattern under `ManualResetEventSlim` reset
- `Dispose` lifecycle (buffer pool return, old-buffer cleanup)

## TODO-02: Chunked protocol integration test
**Priority:** P1 · **Type:** Test coverage

End-to-end round-trip:
- `WriteMessageChunked(obj, AsyncSegment)` → bytes
- `TryParseMessage(bytes)` → reconstructed object
- Assert structural equality with original

Cover asymmetric cases:
- AsyncSegment sender, Segment receiver
- Bytes sender, AsyncSegment receiver
- WASM-downgraded sender (Segment), server AsyncSegment receiver

## TODO-03: `BinaryProtocolMode.Auto` wire-detection implementation
**Priority:** P3 · **Type:** Feature · **Related:** `SIGNALR_TODO.md#todo-04`

Client-side adaptive mode: on first received message, inspect first payload byte:
- `CHUNK_START (200)` → peer uses AsyncSegment → match it on subsequent sends (subject to local-platform constraint — WASM safety-net overrides to Segment)
- Non-chunked → stay with Segment/Bytes

Per-`HubConnection` state. Requires changes to `BinaryProtocolMode` enum + detection wiring in `TryParseMessage`.

## TODO-04: SignalR handshake-extension for upfront mode negotiation
**Priority:** P3 · **Type:** Feature · **Related:** TODO-03

Alternative to wire-detection: use SignalR handshake message's `extensions` JSON field to carry protocol-capability info — e.g.
```json
{ "protocol": "acbinary", "version": 1, "extensions": { "acbinary": { "preferredMode": "AsyncSegment" } } }
```
Zero first-message overhead, fully explicit. Both sides advertise their send-modes; pick intersection. Specification to be drafted; compatibility with non-AC clients (pure JSON etc.) must remain.