Sub-agents

Sub-agents are background agent runs spawned from an existing agent run. They run in their own session (agent:<agentId>:subagent:<uuid>) and, when finished, announce their result back to the requester chat channel. Each sub-agent run is tracked as a background task.

Primary goals:

• Parallelize "research / long task / slow tool" work without blocking the main run.
• Keep sub-agents isolated by default (session separation + optional sandboxing).
• Keep the tool surface hard to misuse: sub-agents do not get session tools by default.
• Support configurable nesting depth for orchestrator patterns.

Slash command

Use /subagents to inspect or control sub-agent runs for the current session:

/subagents list
/subagents kill <id|#|all>
/subagents log <id|#> [limit] [tools]
/subagents info <id|#>
/subagents send <id|#> <message>
/subagents steer <id|#> <message>
/subagents spawn <agentId> <task> [--model <model>] [--thinking <level>]

Use top-level /steer <message> to steer the current requester session's active run. Use /subagents steer <id|#> <message> when the target is a child run.

/subagents info shows run metadata (status, timestamps, session id, transcript path, cleanup). Use sessions_history for a bounded, safety-filtered recall view; inspect the transcript path on disk when you need the raw full transcript.

Thread binding controls

These commands work on channels that support persistent thread bindings. See Thread supporting channels below.

/focus <subagent-label|session-key|session-id|session-label>
/unfocus
/agents
/session idle <duration|off>
/session max-age <duration|off>

Spawn behavior

/subagents spawn starts a background sub-agent as a user command (not an internal relay) and sends one final completion update back to the requester chat when the run finishes.

- `Result` — latest visible `assistant` reply text, otherwise sanitized latest tool/toolResult text. Terminal failed runs do not reuse captured reply text.
- `Status` — `completed successfully` / `failed` / `timed out` / `unknown`.
- Compact runtime/token stats.
- A delivery instruction telling the requester agent to rewrite in normal assistant voice (not forward raw internal metadata).

Context modes

Native sub-agents start isolated unless the caller explicitly asks to fork the current transcript.

Use fork sparingly. It is for context-sensitive delegation, not a replacement for writing a clear task prompt.

Tool: sessions_spawn

Starts a sub-agent run with deliver: false on the global subagent lane, then runs an announce step and posts the announce reply to the requester chat channel.

Availability depends on the caller's effective tool policy. The coding and full profiles expose sessions_spawn by default. The messaging profile does not; add tools.alsoAllow: ["sessions_spawn", "sessions_yield", "subagents"] or use tools.profile: "coding" for agents that should delegate work. Channel/group, provider, sandbox, and per-agent allow/deny policies can still remove the tool after the profile stage. Use /tools from the same session to confirm the effective tool list.

Defaults:

• Model: inherits the caller unless you set agents.defaults.subagents.model (or per-agent agents.list[].subagents.model); an explicit sessions_spawn.model still wins.
• Thinking: inherits the caller unless you set agents.defaults.subagents.thinking (or per-agent agents.list[].subagents.thinking); an explicit sessions_spawn.thinking still wins.
• Run timeout: if sessions_spawn.runTimeoutSeconds is omitted, OpenClaw uses agents.defaults.subagents.runTimeoutSeconds when set; otherwise it falls back to 0 (no timeout).

Tool parameters

Thread-bound sessions

When thread bindings are enabled for a channel, a sub-agent can stay bound to a thread so follow-up user messages in that thread keep routing to the same sub-agent session.

Thread supporting channels

Discord is currently the only supported channel. It supports persistent thread-bound subagent sessions (sessions_spawn with thread: true), manual thread controls (/focus, /unfocus, /agents, /session idle, /session max-age), and adapter keys channels.discord.threadBindings.enabled, channels.discord.threadBindings.idleHours, channels.discord.threadBindings.maxAgeHours, and channels.discord.threadBindings.spawnSessions.

Quick flow

Manual controls

Config switches

• Global default: session.threadBindings.enabled, session.threadBindings.idleHours, session.threadBindings.maxAgeHours.
• Channel override and spawn auto-bind keys are adapter-specific. See Thread supporting channels above.

See Configuration reference and Slash commands for current adapter details.

Allowlist

If the requester session is sandboxed, sessions_spawn rejects targets that would run unsandboxed.

Discovery

Use agents_list to see which agent ids are currently allowed for sessions_spawn. The response includes each listed agent's effective model and embedded runtime metadata so callers can distinguish PI, Codex app-server, and other configured native runtimes.

Auto-archive

• Sub-agent sessions are automatically archived after agents.defaults.subagents.archiveAfterMinutes (default 60).
• Archive uses sessions.delete and renames the transcript to *.deleted.<timestamp> (same folder).
• cleanup: "delete" archives immediately after announce (still keeps the transcript via rename).
• Auto-archive is best-effort; pending timers are lost if the gateway restarts.
• runTimeoutSeconds does not auto-archive; it only stops the run. The session remains until auto-archive.
• Auto-archive applies equally to depth-1 and depth-2 sessions.
• Browser cleanup is separate from archive cleanup: tracked browser tabs/processes are best-effort closed when the run finishes, even if the transcript/session record is kept.

Nested sub-agents

By default, sub-agents cannot spawn their own sub-agents (maxSpawnDepth: 1). Set maxSpawnDepth: 2 to enable one level of nesting — the orchestrator pattern: main → orchestrator sub-agent → worker sub-sub-agents.

{
  agents: {
    defaults: {
      subagents: {
        maxSpawnDepth: 2, // allow sub-agents to spawn children (default: 1)
        maxChildrenPerAgent: 5, // max active children per agent session (default: 5)
        maxConcurrent: 8, // global concurrency lane cap (default: 8)
        runTimeoutSeconds: 900, // default timeout for sessions_spawn when omitted (0 = no timeout)
      },
    },
  },
}

Depth levels

Announce chain

Results flow back up the chain:

1. Depth-2 worker finishes → announces to its parent (depth-1 orchestrator).
2. Depth-1 orchestrator receives the announce, synthesizes results, finishes → announces to main.
3. Main agent receives the announce and delivers to the user.

Each level only sees announces from its direct children.

Tool policy by depth

• Role and control scope are written into session metadata at spawn time. That keeps flat or restored session keys from accidentally regaining orchestrator privileges.
• Depth 1 (orchestrator, when maxSpawnDepth >= 2): gets sessions_spawn, subagents, sessions_list, sessions_history so it can manage its children. Other session/system tools remain denied.
• Depth 1 (leaf, when maxSpawnDepth == 1): no session tools (current default behavior).
• Depth 2 (leaf worker): no session tools — sessions_spawn is always denied at depth 2. Cannot spawn further children.

Per-agent spawn limit

Each agent session (at any depth) can have at most maxChildrenPerAgent (default 5) active children at a time. This prevents runaway fan-out from a single orchestrator.

Cascade stop

Stopping a depth-1 orchestrator automatically stops all its depth-2 children:

• /stop in the main chat stops all depth-1 agents and cascades to their depth-2 children.
• /subagents kill <id> stops a specific sub-agent and cascades to its children.
• /subagents kill all stops all sub-agents for the requester and cascades.

Authentication

Sub-agent auth is resolved by agent id, not by session type:

• The sub-agent session key is agent:<agentId>:subagent:<uuid>.
• The auth store is loaded from that agent's agentDir.
• The main agent's auth profiles are merged in as a fallback; agent profiles override main profiles on conflicts.

The merge is additive, so main profiles are always available as fallbacks. Fully isolated auth per agent is not supported yet.

Announce

Sub-agents report back via an announce step:

• The announce step runs inside the sub-agent session (not the requester session).
• If the sub-agent replies exactly ANNOUNCE_SKIP, nothing is posted.
• If the latest assistant text is the exact silent token NO_REPLY / no_reply, announce output is suppressed even if earlier visible progress existed.

Delivery depends on requester depth:

• Top-level requester sessions use a follow-up agent call with external delivery (deliver=true).
• Nested requester subagent sessions receive an internal follow-up injection (deliver=false) so the orchestrator can synthesize child results in-session.
• If a nested requester subagent session is gone, OpenClaw falls back to that session's requester when available.

For top-level requester sessions, completion-mode direct delivery first resolves any bound conversation/thread route and hook override, then fills missing channel-target fields from the requester session's stored route. That keeps completions on the right chat/topic even when the completion origin only identifies the channel.

Child completion aggregation is scoped to the current requester run when building nested completion findings, preventing stale prior-run child outputs from leaking into the current announce. Announce replies preserve thread/topic routing when available on channel adapters.

Announce context

Announce context is normalized to a stable internal event block:

Terminal failed runs report failure status without replaying captured reply text. On timeout, if the child only got through tool calls, announce can collapse that history into a short partial-progress summary instead of replaying raw tool output.

Stats line

Announce payloads include a stats line at the end (even when wrapped):

• Runtime (e.g. runtime 5m12s).
• Token usage (input/output/total).
• Estimated cost when model pricing is configured (models.providers.*.models[].cost).
• sessionKey, sessionId, and transcript path so the main agent can fetch history via sessions_history or inspect the file on disk.

Internal metadata is meant for orchestration only; user-facing replies should be rewritten in normal assistant voice.

Why prefer sessions_history

sessions_history is the safer orchestration path:

• Assistant recall is normalized first: thinking tags stripped; <relevant-memories> / <relevant_memories> scaffolding stripped; plain-text tool-call XML payload blocks (<tool_call>, <function_call>, <tool_calls>, <function_calls>) stripped, including truncated payloads that never close cleanly; downgraded tool-call/result scaffolding and historical-context markers stripped; leaked model control tokens (<|assistant|>, other ASCII <|...|>, full-width <｜...｜>) stripped; malformed MiniMax tool-call XML stripped.
• Credential/token-like text is redacted.
• Long blocks can be truncated.
• Very large histories can drop older rows or replace an oversized row with [sessions_history omitted: message too large].
• Raw on-disk transcript inspection is the fallback when you need the full byte-for-byte transcript.

Tool policy

Sub-agents use the same profile and tool-policy pipeline as the parent or target agent first. After that, OpenClaw applies the sub-agent restriction layer.

With no restrictive tools.profile, sub-agents get all tools except session tools and system tools:

• sessions_list
• sessions_history
• sessions_send
• sessions_spawn

sessions_history remains a bounded, sanitized recall view here too — it is not a raw transcript dump.

When maxSpawnDepth >= 2, depth-1 orchestrator sub-agents additionally receive sessions_spawn, subagents, sessions_list, and sessions_history so they can manage their children.

Override via config

{
  agents: {
    defaults: {
      subagents: {
        maxConcurrent: 1,
      },
    },
  },
  tools: {
    subagents: {
      tools: {
        // deny wins
        deny: ["gateway", "cron"],
        // if allow is set, it becomes allow-only (deny still wins)
        // allow: ["read", "exec", "process"]
      },
    },
  },
}

tools.subagents.tools.allow is a final allow-only filter. It can narrow the already-resolved tool set, but it cannot add back a tool removed by tools.profile. For example, tools.profile: "coding" includes web_search/web_fetch but not the browser tool. To let coding-profile sub-agents use browser automation, add browser at the profile stage:

{
  tools: {
    profile: "coding",
    alsoAllow: ["browser"],
  },
}

Use per-agent agents.list[].tools.alsoAllow: ["browser"] when only one agent should get browser automation.

Concurrency

Sub-agents use a dedicated in-process queue lane:

• Lane name: subagent
• Concurrency: agents.defaults.subagents.maxConcurrent (default 8)

Liveness and recovery

OpenClaw does not treat endedAt absence as permanent proof that a sub-agent is still alive. Unended runs older than the stale-run window stop counting as active/pending in /subagents list, status summaries, descendant completion gating, and per-session concurrency checks.

After a gateway restart, stale unended restored runs are pruned unless their child session is marked abortedLastRun: true. Those restart-aborted child sessions remain recoverable through the sub-agent orphan recovery flow, which sends a synthetic resume message before clearing the aborted marker.

Automatic restart recovery is bounded per child session. If the same sub-agent child is accepted for orphan recovery repeatedly inside the rapid re-wedge window, OpenClaw persists a recovery tombstone on that session and stops auto-resuming it on later restarts. Run openclaw tasks maintenance --apply to reconcile the task record, or openclaw doctor --fix to clear stale aborted recovery flags on tombstoned sessions.

Stopping

• Sending /stop in the requester chat aborts the requester session and stops any active sub-agent runs spawned from it, cascading to nested children.
• /subagents kill <id> stops a specific sub-agent and cascades to its children.

Limitations

• Sub-agent announce is best-effort. If the gateway restarts, pending "announce back" work is lost.
• Sub-agents still share the same gateway process resources; treat maxConcurrent as a safety valve.
• sessions_spawn is always non-blocking: it returns { status: "accepted", runId, childSessionKey } immediately.
• Sub-agent context only injects AGENTS.md + TOOLS.md (no SOUL.md, IDENTITY.md, USER.md, HEARTBEAT.md, or BOOTSTRAP.md).
• Maximum nesting depth is 5 (maxSpawnDepth range: 1–5). Depth 2 is recommended for most use cases.
• maxChildrenPerAgent caps active children per session (default 5, range 1–20).

Related

• ACP agents
• Agent send
• Background tasks
• Multi-agent sandbox tools