fix: queue TTL + per-member send rate limit + size cap + no-recipient reject + ack.error

Broker (all need redeploy):
- sweepOrphanMessages: DELETE undelivered message_queue rows older
  than 7 days; hourly sweep. Stops unbounded growth when a sender
  typos a name (queued forever, never claimed).
- Per-member send rate limit: TokenBucket(60/min, burst 10) keyed on
  memberId so reconnecting can't bypass. Surfaces as queued=false,
  error='rate_limit: ...'.
- Pre-flight size cap: reject at handleSend if nonce+ciphertext+
  targetSpec exceeds env.MAX_MESSAGE_BYTES with a clear error
  instead of silent WSS frame-level kill.
- No-recipient reject: for direct sends, check any matching peer
  is connected BEFORE queueing. Kills the self-send silent drop
  (sending to your own pubkey when you only have one session
  connected) and typo-to-offline-peer silent drops.
- WSAckMessage.error field added for structured failure reasons.

CLI:
- ws-client ack handler reads msg.queued and msg.error; surfaces
  rate_limit / too_large / no_recipient to callers instead of
  returning ok:true with a dummy messageId.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/broker/src/broker.ts

@@ -293,6 +293,29 @@ export async function sweepStalePresences(): Promise<void> {
     );
 }
 
+/**
+ * Sweep undelivered message_queue rows older than 7 days.
+ *
+ * Messages sent to non-matching targetSpecs (e.g. typos, peer disconnected
+ * before claim) would otherwise sit in delivered_at=NULL forever — unbounded
+ * growth. 7d matches invite expiry, so any legitimately held message is
+ * already stale by then.
+ *
+ * Returns the number of rows deleted so the caller can log + meter.
+ */
+export async function sweepOrphanMessages(): Promise<number> {
+  const cutoff = new Date(Date.now() - 7 * 24 * 60 * 60 * 1000);
+  const result = await db.execute(sql`
+    DELETE FROM mesh.message_queue
+    WHERE delivered_at IS NULL
+      AND created_at < ${cutoff}
+    RETURNING id
+  `);
+  const rows = (result as unknown as { rows?: unknown[]; length?: number }).rows ?? result;
+  const count = Array.isArray(rows) ? rows.length : 0;
+  return count;
+}
+
 /** Sweep expired pending_status entries. */
 export async function sweepPendingStatuses(): Promise<void> {
   const cutoff = new Date(Date.now() - PENDING_TTL_MS);
@@ -1667,6 +1690,12 @@ export function startSweepers(): void {
       console.error("[broker] stale presence sweep:", e),
     );
   }, 30_000);
+  // Orphan-message sweep every hour; cheap, rows are all >7d at deletion time.
+  setInterval(() => {
+    sweepOrphanMessages()
+      .then((n) => { if (n > 0) console.log(`[broker] orphan msgs swept: ${n}`); })
+      .catch((e) => console.error("[broker] orphan msg sweep:", e));
+  }, 60 * 60_000).unref();
 }
 
 /** Stop background sweepers and mark all active presences disconnected. */

apps/broker/src/index.ts

@@ -483,6 +483,14 @@ const hookRateLimit = new TokenBucket(
   env.HOOK_RATE_LIMIT_PER_MIN,
 );
 
+/**
+ * Per-member send rate limit. Protects the mesh from a runaway peer
+ * dumping messages. Bucket is 60 msgs/min with a burst of 10 — generous
+ * for conversational use, tight enough that a loop bug surfaces in seconds.
+ * Configurable via env in a later pass.
+ */
+const sendRateLimit = new TokenBucket(60, 10);
+
 function sendToPeer(presenceId: string, msg: WSServerMessage): void {
   const conn = connections.get(presenceId);
   if (!conn) return;
@@ -1792,6 +1800,75 @@ async function handleSend(
   msg: Extract<WSClientMessage, { type: "send" }>,
   subtype?: "reminder",
 ): Promise<void> {
+  // Per-member rate limit (60/min, burst 10). Runaway peer → graceful ack
+  // failure instead of queue explosion. Uses member (not session) key so a
+  // peer can't dodge by reconnecting.
+  if (!sendRateLimit.take(conn.memberId)) {
+    metrics.messagesRejectedTotal.inc({ reason: "rate_limit" });
+    const errAck: WSServerMessage = {
+      type: "ack",
+      id: msg.id ?? "",
+      messageId: "",
+      queued: false,
+      error: "rate_limit: max 60 msg/min (burst 10) — slow down",
+    };
+    conn.ws.send(JSON.stringify(errAck));
+    return;
+  }
+
+  // Size cap — ws.maxPayload catches giants at the frame level, but we also
+  // reject verbose nonce+ciphertext combinations above env.MAX_MESSAGE_BYTES
+  // so clients get a clear error instead of a silent socket kill.
+  const approxBytes =
+    (msg.ciphertext?.length ?? 0) + (msg.nonce?.length ?? 0) + (msg.targetSpec?.length ?? 0);
+  if (approxBytes > env.MAX_MESSAGE_BYTES) {
+    metrics.messagesRejectedTotal.inc({ reason: "too_large" });
+    const errAck: WSServerMessage = {
+      type: "ack",
+      id: msg.id ?? "",
+      messageId: "",
+      queued: false,
+      error: `payload too large: ${approxBytes} bytes > MAX_MESSAGE_BYTES=${env.MAX_MESSAGE_BYTES}`,
+    };
+    conn.ws.send(JSON.stringify(errAck));
+    return;
+  }
+
+  // Pre-flight: for direct sends (not @group, not *), verify at least one
+  // matching connected peer exists BEFORE queueing. Prevents silent drops
+  // when a user sends to a typo, their own pubkey with no other session,
+  // or a peer who has disconnected. The CLI's resolveClient already guards
+  // name-based targets; this catches raw-pubkey and CLI-bypassing clients.
+  const isGroupTargetEarly = msg.targetSpec.startsWith("@");
+  const isBroadcastEarly =
+    msg.targetSpec === "*" ||
+    (isGroupTargetEarly && msg.targetSpec === "@all");
+  const isDirectEarly = !isGroupTargetEarly && !isBroadcastEarly && msg.targetSpec !== "*";
+  if (isDirectEarly) {
+    let hasRecipient = false;
+    for (const [pid, peer] of connections) {
+      if (peer.meshId !== conn.meshId) continue;
+      if (peer.ws === conn.ws) continue;
+      if (peer.memberPubkey === msg.targetSpec || peer.sessionPubkey === msg.targetSpec) {
+        hasRecipient = true;
+        break;
+      }
+      void pid;
+    }
+    if (!hasRecipient) {
+      metrics.messagesRejectedTotal.inc({ reason: "no_recipient" });
+      const errAck: WSServerMessage = {
+        type: "ack",
+        id: msg.id ?? "",
+        messageId: "",
+        queued: false,
+        error: `no connected peer for target (not online, or targetSpec is your own key without another session)`,
+      };
+      conn.ws.send(JSON.stringify(errAck));
+      return;
+    }
+  }
+
   const messageId = await queueMessage({
     meshId: conn.meshId,
     senderMemberId: conn.memberId,

apps/broker/src/types.ts

@@ -206,6 +206,8 @@ export interface WSAckMessage {
   id: string; // echoes client-side correlation id
   messageId: string;
   queued: boolean;
+  /** Populated when queued=false to explain why (rate_limit, too_large, etc.). */
+  error?: string;
   _reqId?: string;
 }