Before Phase 6, each side's dual-path race ran independently and
committed to whichever transport completed first. When one side
picked Direct and the other picked Relay, they sent media to
different places — TX > 0 RX: 0 on both, completely silent call.
Phase 6 adds a negotiation step: after the local race completes,
each side sends a MediaPathReport { call_id, direct_ok, winner }
to the peer through the relay. Both wait for the other's report
before committing a transport to the CallEngine. The decision
rule is simple: if BOTH report direct_ok = true, use direct; if
EITHER reports false, BOTH use relay.
## Wire protocol
New `SignalMessage::MediaPathReport { call_id, direct_ok,
race_winner }`. The relay forwards it to the call peer via the
same signal_hub routing used for DirectCallOffer/Answer. The
cross-relay dispatcher also forwards it.
## dual_path::race restructured
Returns `RaceResult` instead of `(Arc<QuinnTransport>, WinningPath)`:
- `direct_transport: Option<Arc<QuinnTransport>>`
- `relay_transport: Option<Arc<QuinnTransport>>`
- `local_winner: WinningPath`
Both paths are run as spawned tasks. After the first completes,
a 1s grace period lets the loser also finish. The connect
command gets BOTH transports (when available) and picks the
right one based on the negotiation outcome. The unused transport
is dropped.
## connect command flow (revised)
1. Run race() → RaceResult with both transports
2. Send MediaPathReport to relay with our direct_ok
3. Install oneshot; wait for peer's report (3s timeout)
4. Decision: both direct_ok → use direct; else → use relay
5. Start CallEngine with the agreed transport
If the peer never responds (old build, timeout), falls back to
relay — backward compatible.
## Relay forwarding
MediaPathReport is forwarded like DirectCallOffer/Answer: via
signal_hub.send_to(peer_fp) for same-relay calls, and via
cross-relay dispatcher for federated calls.
## Debug log events
- `connect:dual_path_race_done` — local race result
- `connect:path_report_sent` — our report to the peer
- `connect:peer_report_received` — peer's report
- `connect:peer_report_timeout` — peer didn't respond (3s)
- `connect:path_negotiated` — final agreed path with reasons
Full workspace test: 423 passing (no regressions).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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