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openclaw - 💡(How to fix) Fix ACP sessions_spawn fails with "spawnedBy is only supported for subagent:* sessions" [2 comments, 2 participants]

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openclaw/openclaw#43651•Fetched 2026-04-08 00:16:22
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Error Message

sessions_spawn with runtime="acp" consistently fails with error: 4. Error occurs consistently Error: "spawnedBy is only supported for subagent:* sessions"

  • The error suggests a session type/naming convention mismatch

Fix Action

Workaround

Direct Claude Code CLI usage works fine:

claude "your task here"

Code Example

spawnedBy is only supported for subagent:* sessions

---

claude "your task here"
RAW_BUFFERClick to expand / collapse

Bug Description

sessions_spawn with runtime="acp" consistently fails with error:

spawnedBy is only supported for subagent:* sessions

Environment

  • OpenClaw: 2026.3.8 (3caab92)
  • OS: Ubuntu 24.04.4 LTS (ARM64)
  • Node: v22.22.0
  • Platform: AWS EC2 (Graviton 3)

Configuration

  • acpx plugin: loaded and enabled (version 2026.3.8-beta.1)
  • acpx CLI: available (v0.1.15)
  • Claude Code CLI: working (v2.1.71)
  • ACP config: enabled=true, backend="acpx", agents=["claude","codex","gemini"]
  • Environment vars: CLAUDE_CODE_USE_BEDROCK=1, AWS_REGION=us-west-2

Reproduction Steps

  1. Configure ACP with acpx backend
  2. Ensure acpx plugin is loaded
  3. Call sessions_spawn(runtime="acp", agentId="claude", mode="run", task="test")
  4. Error occurs consistently

Expected Behavior

ACP session should spawn and execute the task using Claude Code

Actual Behavior

Error: "spawnedBy is only supported for subagent:* sessions"

Workaround

Direct Claude Code CLI usage works fine:

claude "your task here"

Additional Context

  • All ACP components appear to be correctly installed and configured
  • The error suggests a session type/naming convention mismatch
  • This affects the core ACP integration functionality

Investigation Done

  • Verified acpx plugin is loaded: openclaw plugins list
  • Verified Claude Code CLI works: claude --version returns 2.1.71
  • Verified environment variables are set in systemd override
  • Checked configuration multiple times

The issue appears to be in the OpenClaw core session spawning logic when routing to ACP runtime.

extent analysis

Fix Plan

To resolve the issue with sessions_spawn failing when using runtime="acp", we need to adjust the session spawning logic to correctly handle ACP runtime sessions.

Step-by-Step Solution

  1. Update Session Spawning Logic: Modify the sessions_spawn function to check for runtime="acp" and handle it accordingly.
  2. Use Subagent Session Type: When runtime="acp", use a subagent session type to spawn the session.

Example Code Changes

def sessions_spawn(runtime, agent_id, mode, task):
    if runtime == "acp":
        # Use subagent session type for ACP runtime
        session_type = "subagent:*"
        # Spawn session with updated session type
        session = spawn_session(session_type, agent_id, mode, task)
        return session
    else:
        # Handle other runtimes as before
        # ...

Verification

To verify the fix, follow these steps:

  • Call sessions_spawn with runtime="acp" and verify that the session is spawned correctly.
  • Check the session type used to spawn the session and ensure it is subagent:*.
  • Test the execution of the task using the spawned session.

Extra Tips

  • Ensure that the acpx plugin is loaded and enabled.
  • Verify that the Claude Code CLI is working correctly.
  • Check the environment variables and configuration settings to ensure they are set correctly.

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openclaw - 💡(How to fix) Fix ACP sessions_spawn fails with "spawnedBy is only supported for subagent:* sessions" [2 comments, 2 participants]