Bug type

Regression (worked before, now fails)

Beta release blocker

No

Summary

After upgrading from OpenClaw 2026.4.24 to 2026.4.25, all ACP sessions_spawn calls fail instantly (~2s, 0 tokens) with AcpRuntimeError: Internal error / ACP_TURN_FAILED; gateway logs show a WS client sending sessions.list before the required connect frame, and the bundled acpx v0.6.1 backend registers but never reaches "ready."

Steps to reproduce

1. Upgrade OpenClaw from 2026.4.24 to 2026.4.25 (npm install -g [email protected]).
2. Restart gateway (openclaw gateway restart).
3. Spawn any ACP session: sessions_spawn({ task: "Say hello", runtime: "acp", agentId: "claude", mode: "run" }).
4. Observe instant failure (~2s, 0 tokens): AcpRuntimeError: Internal error.
5. Check gateway log: gateway connect failed: Error: gateway closed (1008): invalid handshake: first request must be connect.

Expected behavior

In 2026.4.24 (bundled acpx v0.5.3), ACP sessions spawned successfully. The acpx backend showed "registered" then "ready" within ~0.2s, and ACP turns completed normally with token output.

Actual behavior

In 2026.4.25 (bundled acpx v0.6.1), the acpx backend shows "registered" but never "ready." Every ACP turn fails in ~2s with 0 tokens processed. Gateway log shows:

[gateway/ws] cause: invalid-handshake, lastFrameMethod: sessions.list, handshakeError: invalid handshake: first request must be connect [ERROR] gateway connect failed: Error: gateway closed (1008): invalid handshake: first request must be connect [gateway] acp startup identity reconcile (renderer=v1): checked=22 resolved=0 failed=22

Reproduced across 6+ gateway restarts, fresh auth token, cleaned session state, and bumped maxConcurrentSessions to 100. Non-ACP subagent spawns work fine.

OpenClaw version

2026.4.25 (aa36ee6)

Operating system

macOS 15.4 (Darwin 25.4.0, arm64, Apple M5 Max)

Install method

npm global (nvm, Node v22.22.2)

Model

anthropic/claude-sonnet-4-6 (for the parent agent); ACP agents: claude-agent-acp v0.26.0, codex-acp

Provider / routing chain

openclaw -> anthropic (via claude-cli auth profile)

Additional provider/model setup details

• Auth profile: anthropic:claude-cli (OAuth, re-authed fresh during debugging — did not resolve the issue)
• OPENCLAW_ACPX_RUNTIME_STARTUP_PROBE: not set
• plugins.entries.acpx.config.permissionMode: approve-all
• plugins.entries.acpx.config.agents.claude.command: claude-agent-acp
• plugins.entries.acpx.config.agents.codex.command: codex-acp
• acp.maxConcurrentSessions: 100
• acp.runtime.ttlMinutes: 45
• Plugin runtime deps path: ~/.openclaw/plugin-runtime-deps/openclaw-2026.4.25-1674699698bd/ (acpx v0.6.1)
• Previous working: ~/.openclaw/plugin-runtime-deps/openclaw-2026.4.24-1674699698bd/ (acpx v0.5.3)

Logs, screenshots, and evidence

Gateway log (relevant lines across multiple boots on 2026-04-27):


2026-04-26T16:33:02 [plugins] embedded acpx runtime backend ready          ← last "ready" (2026.4.24)

2026-04-27T13:23:11 [plugins] embedded acpx runtime backend registered     ← first boot on 2026.4.25, never "ready"
2026-04-27T13:48:01 [plugins] embedded acpx runtime backend registered     ← second boot, never "ready"
2026-04-27T14:43:51 [plugins] embedded acpx runtime backend registered     ← third boot, never "ready"

2026-04-27T14:47:09 [ws] res ✗ agent errorCode=UNAVAILABLE errorMessage=AcpRuntimeError: Internal error code=ACP_TURN_FAILED
2026-04-27T14:48:42 [ws] res ✗ agent errorCode=UNAVAILABLE errorMessage=AcpRuntimeError: Internal error code=ACP_TURN_FAILED
2026-04-27T14:58:43 [ws] res ✗ agent errorCode=UNAVAILABLE errorMessage=AcpRuntimeError: Internal error code=ACP_TURN_FAILED
2026-04-27T15:08:16 [ws] res ✗ agent errorCode=UNAVAILABLE errorMessage=AcpRuntimeError: Internal error code=ACP_TURN_FAILED
2026-04-27T15:32:27 [ws] res ✗ agent errorCode=UNAVAILABLE errorMessage=AcpRuntimeError: Internal error code=ACP_TURN_FAILED


WS handshake failure (from /tmp/openclaw/openclaw-2026-04-27.log, structured fields):


{
  "cause": "invalid-handshake",
  "handshake": "failed",
  "lastFrameType": "req",
  "lastFrameMethod": "sessions.list",
  "handshakeError": "invalid handshake: first request must be connect",
  "host": "127.0.0.1:18789"
}



[ERROR] gateway connect failed: Error: gateway closed (1008): invalid handshake: first request must be connect
[WARN] acp startup identity reconcile (renderer=v1): checked=22 resolved=0 failed=22


openclaw doctor (relevant):


Model auth: anthropic:claude-cli expiring (8h)
Claude CLI: Binary ~/.local/bin/claude, workspace writable
Gateway service: PATH includes nvm, Node from version manager
Plugins: Loaded 12, Errors 0


openclaw gateway status:


Service: LaunchAgent (loaded)
Runtime: running, state active
Connectivity probe: ok
Listening: 127.0.0.1:18789


Standalone ACP agent test (works fine outside OpenClaw):


$ echo '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":1,...}}' | node claude-agent-acp/dist/index.js
→ {"jsonrpc":"2.0","id":1,"result":{"protocolVersion":1,"agentInfo":{"name":"@agentclientprotocol/claude-agent-acp","version":"0.26.0"}}}

Impact and severity

Affected: All ACP agent spawns (Claude Code, Codex) on this installation Severity: High — blocks all ACP-based coding agent workflows (Boris/Vlad delegation) Frequency: 100% — every ACP spawn fails, across 6+ gateway restarts and multiple debugging attempts Consequence: Cannot use ACP runtime for coding agents; forced to fall back to non-ACP subagent spawns which work but use a different execution model

Additional information

Last known good: 2026.4.24 (bundled acpx v0.5.3) — ACP working normally on 2026-04-26 First known bad: 2026.4.25 (bundled acpx v0.6.1) — ACP broken on first boot 2026-04-27

Ruled out during debugging:

• Auth: Claude CLI re-authed, fresh token (8h), same failure
• Session state: Cleaned 585 stale session files + 273 orphaned registry entries + 330 transcript files
• Concurrent limit: Bumped maxConcurrentSessions from 40 to 100
• ACP agents: Both claude-agent-acp and codex-acp work correctly standalone

Workaround: Use runtime="subagent" instead of runtime="acp" for agent spawns.