Problem

sessions_spawn with mode="session" unconditionally requires thread: true:

if (spawnMode === "session" && !requestThreadBinding) return {
    status: "error",
    error: "mode=\"session\" requires thread=true so the ACP session can stay bound to a thread."
};

If the channel does not support thread bindings (e.g. Feishu, Signal, WhatsApp), the request fails with:

Thread bindings are unavailable for <channel>.

This makes persistent ACP sessions (and persistent subagent sessions) unusable on any channel without native thread support.

Why this coupling is unnecessary

Thread binding and persistent sessions serve two independent purposes:

Thread binding is a delivery optimization — it lets users talk directly to a sub-session in a thread. But the session itself does not need a thread to exist. The parent agent can perfectly well relay messages to the session using sessions_send(label=...) or sessions_send(sessionKey=...).

Current user experience

On channels without thread support:

• mode="session" → error → only mode="run" available → no multi-turn sessions
• Workaround: use mode="run" with file-based state passing between invocations, which loses all session context

On channels with thread support (Discord):

• Works as expected

Proposed behavior

Allow mode="session" without thread: true:

When mode="session" and thread is not set:

• Create the persistent session normally
• Return the childSessionKey / label so the caller can use sessions_send to continue the conversation
• Deliver output back to the parent session (or the originating chat, same as mode="run")

Use cases unlocked

1. Agent-as-orchestrator: Parent agent manages multi-turn sub-sessions programmatically (Feishu, WhatsApp, Signal, etc.)
2. Multi-persona routing: Parent agent routes to different persistent sub-sessions based on context — this is a routing decision, not a thread decision
3. Iterative coding workflows: Spawn a persistent Kiro/Claude/Codex session, send incremental instructions, accumulate context — on any channel

Environment

• OpenClaw version: latest (checked source in dist/plugin-sdk/thread-bindings-SYAnWHuW.js)
• Affected channels: all channels without native thread support (Feishu, Signal, WhatsApp, Google Chat, Line, etc.)
• Works on: Discord (has native threads)