fix: Exchange public keys during Braid subscription handshake

Peers now send X-Public-Key header when subscribing, so the receiving
node can verify consensus signatures immediately without waiting for
Redis discovery.

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

src/transport/braid-peer-manager.ts

@@ -221,6 +221,7 @@ export class BraidPeerManager extends EventEmitter {
   private handleSyncSubscribe(req: Request, res: Response): void {
     const subscribe = req.headers['subscribe'];
     const nodeId = req.headers['x-node-id'] as string;
+    const publicKey = req.headers['x-public-key'] as string;
 
     if (!nodeId) {
       res.status(400).json({ error: 'Missing X-Node-Id header' });
@@ -241,6 +242,9 @@ export class BraidPeerManager extends EventEmitter {
         'X-Node-Id': this.config.nodeId,
       });
 
+      // Flush headers by writing an initial empty comment line
+      res.write('\r\n');
+
       // Track subscriber
       this.subscribers.set(nodeId, {
         nodeId,
@@ -248,13 +252,23 @@ export class BraidPeerManager extends EventEmitter {
         connectedAt: Date.now(),
       });
 
-      // Register as connected peer
+      // Register as connected peer and update knownPeers with public key
+      const peerInfo = this.knownPeers.get(nodeId);
+      const endpoint = peerInfo?.endpoint ?? `http://${nodeId}:${this.config.port}`;
+
+      // Store/update peer info so getPeerInfo() returns the public key
+      if (publicKey && (!peerInfo || !peerInfo.publicKey || peerInfo.publicKey === '0x' + '0'.repeat(64))) {
+        this.knownPeers.set(nodeId, {
+          nodeId,
+          publicKey,
+          endpoint,
+          lastSeen: Date.now(),
+        });
+      }
+
       if (!this.peers.has(nodeId)) {
-        const peerInfo = this.knownPeers.get(nodeId);
+        this.peers.set(nodeId, new BraidPeer(nodeId, endpoint));
-        if (peerInfo) {
+        this.emit('peer:connected', nodeId);
-          this.peers.set(nodeId, new BraidPeer(nodeId, peerInfo.endpoint));
-          this.emit('peer:connected', nodeId);
-        }
       }
 
       // Trigger initial sync
@@ -477,6 +491,8 @@ export class BraidPeerManager extends EventEmitter {
   async subscribeToPeer(peerInfo: BraidPeerInfo): Promise<void> {
     if (this.outboundSubs.has(peerInfo.nodeId)) return;
 
+    logger.info({ nodeId: peerInfo.nodeId, endpoint: peerInfo.endpoint }, 'Attempting Braid subscription');
+
     const controller = new AbortController();
     const endpoint = peerInfo.endpoint;
 
@@ -493,6 +509,7 @@ export class BraidPeerManager extends EventEmitter {
         headers: {
           'Subscribe': 'keep-alive',
           'X-Node-Id': this.config.nodeId,
+          'X-Public-Key': this.config.publicKey,
           'Accept': 'application/octet-stream',
         },
         signal: controller.signal,
@@ -549,35 +566,18 @@ export class BraidPeerManager extends EventEmitter {
 
   /**
    * Parse and handle an incoming Braid update from a subscription stream.
+   *
+   * The Braid subscription stream is used for:
+   * - Peer liveness (keeping the connection open)
+   * - Simpleton JSON state updates (future)
+   *
+   * Automerge binary sync goes through HTTP POST (SYNC_RESPONSE messages),
+   * NOT through this text stream — binary data gets corrupted in text mode.
    */
   private handleBraidUpdate(nodeId: string, chunk: string): void {
-    try {
+    // Currently the stream is used for liveness only.
-      // Extract headers and body from the Braid update
+    // Automerge sync messages are exchanged via HTTP POST to /braid/consensus.
-      const headerEnd = chunk.indexOf('\r\n\r\n');
+    logger.debug({ nodeId, chunkLen: chunk.length }, 'Received Braid stream update');
-      if (headerEnd === -1) {
-        // Body might be right after headers with a single newline separation
-        const lines = chunk.split('\r\n');
-        const bodyStartIdx = lines.findIndex(l => l === '');
-        if (bodyStartIdx === -1) return;
-
-        // Everything after the empty line is body
-        const bodyLines = lines.slice(bodyStartIdx + 1);
-        const body = bodyLines.join('\r\n');
-        if (body.length > 0) {
-          const data = new Uint8Array(Buffer.from(body, 'binary'));
-          this.emit('message:sync_response', nodeId, data);
-        }
-        return;
-      }
-
-      const body = chunk.slice(headerEnd + 4);
-      if (body.length > 0) {
-        const data = new Uint8Array(Buffer.from(body, 'binary'));
-        this.emit('message:sync_response', nodeId, data);
-      }
-    } catch (error) {
-      logger.error({ nodeId, error }, 'Failed to parse Braid update');
-    }
   }
 
   // --- Redis-based peer discovery (reused from WebSocket version) ---