openclaw - 💡(How to fix) Fix Discord thread-bound ACP sessions (mode=session) deliver each response twice [1 participants]

Summary

Thread-bound ACP sessions (sessions_spawn with runtime: "acp", thread: true, mode: "session") send every response twice to the Discord thread, ~300–800ms apart. Both messages are identical and delivered via the same webhook persona.

Environment

• OpenClaw: 2026.4.2 (d74a122)
• acpx: bundled
• ACP agent: Claude Code (OAuth, claude-opus-4-6)
• Channel: Discord (gateway bot)
• OS: macOS 26.4 (arm64)

Reproduction

1. Enable thread-bound ACP spawns:

   "channels.discord.threadBindings.spawnAcpSessions": true,
   "channels.discord.threadBindings.enabled": true,
   "acp.enabled": true

2. Agent definition (agents.list[]):

   {
     "id": "claude",
     "runtime": { "type": "acp", "acp": { "agent": "claude", "backend": "acpx", "mode": "persistent" } }
   }

3. From a main session, spawn an ACP session with sessions_spawn(runtime: "acp", agentId: "claude", thread: true, mode: "session", task: "...")
4. Send any message in the resulting Discord thread
5. Every response appears twice (~300–800ms gap, identical content, same webhook)

Evidence

Discord thread 1489899150219808790 shows consistent duplication:

Both messages come from the same webhook (id: 1489559854879080528, username: 🤖 claude).

Gateway log shows an announce run alongside the normal inline delivery:

[ws] ⇄ res ✓ agent 119ms runId=announce:v1:agent:claude:acp:66d6895d-...:015b9656-...

Analysis

Two delivery paths fire for the same response:

1. Inline delivery (deliver: true): resolveAcpSpawnBootstrapDeliveryPlan sets useInlineDelivery = true when spawnMode === "session" and requester origin channel exists. The gateway auto-reply sends the response directly to the thread via the webhook.

2. Announce delivery: After the turn completes, the subagent announce machinery (deliverSubagentAnnouncement) fires. The Discord subagent_delivery_target hook resolves the thread binding and delivers a second copy to the same thread.

For mode: "session", shouldKeepThreadBindingAfterRun returns true (preventing lifecycle hooks), but the per-turn announce still fires because each user message triggers a new agent turn that completes.

Key code paths:

• resolveAcpSpawnBootstrapDeliveryPlan (line ~21874): sets useInlineDelivery for session mode
• resolveSpawnMode$1 (line ~21548): thread: true + no explicit mode → defaults to "session"
• runSubagentAnnounceDispatch (line ~10490): dispatches announce after turn

Expected behavior

Each response should be delivered exactly once to the Discord thread.

Workarounds

• Set channels.discord.threadBindings.spawnAcpSessions: false (disables thread-bound ACP entirely)
• Spawn with explicit mode: "run" instead of mode: "session" (loses persistent conversation)
• No config-only fix exists to keep mode: "session" without duplication

Config (relevant subset)

{
  "acp": {
    "enabled": true,
    "backend": "acpx",
    "defaultAgent": "claude",
    "allowedAgents": ["claude", "codex"],
    "maxConcurrentSessions": 8
  },
  "channels": {
    "discord": {
      "threadBindings": {
        "enabled": true,
        "spawnAcpSessions": true
      }
    }
  },
  "session": {
    "threadBindings": {
      "enabled": true,
      "idleHours": 24,
      "maxAgeHours": 0
    }
  }
}

No duplicate bindings or routes exist; only one Discord account is configured.