* docs(subagents): rewrite page for clarity with examples and Mintlify components - Add Quick Start section with natural language usage examples - Add step-by-step How It Works using <Steps> component - Break configuration into focused subsections with code examples - Add proper parameters table for sessions_spawn tool - Document model resolution order (verified against codebase) - Add interactive /subagents command examples in <AccordionGroup> - Fix inaccurate tool deny list: document all 11 denied tools (was 4) - Use <Tip>, <Note>, <Warning>, <Accordion> components throughout - Add cross-agent spawning config example - Add full configuration example in collapsible accordion - Add See Also links to related pages - All information preserved or verified against codebase * docs(subagents): correct behavior and config defaults - Fix model/thinking defaults to match runtime behavior - Clarify model and thinking resolution order for sessions_spawn - Remove incorrect claim that announce runs in child session - Replace ANNOUNCE_SKIP note with NO_REPLY behavior - Align announce status wording with runtime outcomes * docs(subagents): clarify NO_REPLY vs ANNOUNCE_SKIP (#12761) (thanks @sebslight)
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summary, read_when, title
| summary | read_when | title | ||
|---|---|---|---|---|
| Sub-agents: spawning isolated agent runs that announce results back to the requester chat |
|
Sub-Agents |
Sub-Agents
Sub-agents let you run background tasks without blocking the main conversation. When you spawn a sub-agent, it runs in its own isolated session, does its work, and announces the result back to the chat when finished.
Use cases:
- Research a topic while the main agent continues answering questions
- Run multiple long tasks in parallel (web scraping, code analysis, file processing)
- Delegate tasks to specialized agents in a multi-agent setup
Quick Start
The simplest way to use sub-agents is to ask your agent naturally:
"Spawn a sub-agent to research the latest Node.js release notes"
The agent will call the sessions_spawn tool behind the scenes. When the sub-agent finishes, it announces its findings back into your chat.
You can also be explicit about options:
"Spawn a sub-agent to analyze the server logs from today. Use gpt-5.2 and set a 5-minute timeout."
How It Works
The main agent calls `sessions_spawn` with a task description. The call is **non-blocking** — the main agent gets back `{ status: "accepted", runId, childSessionKey }` immediately. A new isolated session is created (`agent::subagent:`) on the dedicated `subagent` queue lane. When the sub-agent finishes, it announces its findings back to the requester chat. The main agent posts a natural-language summary. The sub-agent session is auto-archived after 60 minutes (configurable). Transcripts are preserved. Each sub-agent has its **own** context and token usage. Set a cheaper model for sub-agents to save costs — see [Setting a Default Model](#setting-a-default-model) below.Configuration
Sub-agents work out of the box with no configuration. Defaults:
- Model: target agent’s normal model selection (unless
subagents.modelis set) - Thinking: no sub-agent override (unless
subagents.thinkingis set) - Max concurrent: 8
- Auto-archive: after 60 minutes
Setting a Default Model
Use a cheaper model for sub-agents to save on token costs:
{
agents: {
defaults: {
subagents: {
model: "minimax/MiniMax-M2.1",
},
},
},
}
Setting a Default Thinking Level
{
agents: {
defaults: {
subagents: {
thinking: "low",
},
},
},
}
Per-Agent Overrides
In a multi-agent setup, you can set sub-agent defaults per agent:
{
agents: {
list: [
{
id: "researcher",
subagents: {
model: "anthropic/claude-sonnet-4",
},
},
{
id: "assistant",
subagents: {
model: "minimax/MiniMax-M2.1",
},
},
],
},
}
Concurrency
Control how many sub-agents can run at the same time:
{
agents: {
defaults: {
subagents: {
maxConcurrent: 4, // default: 8
},
},
},
}
Sub-agents use a dedicated queue lane (subagent) separate from the main agent queue, so sub-agent runs don't block inbound replies.
Auto-Archive
Sub-agent sessions are automatically archived after a configurable period:
{
agents: {
defaults: {
subagents: {
archiveAfterMinutes: 120, // default: 60
},
},
},
}
The sessions_spawn Tool
This is the tool the agent calls to create sub-agents.
Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
task |
string | (required) | What the sub-agent should do |
label |
string | — | Short label for identification |
agentId |
string | (caller's agent) | Spawn under a different agent id (must be allowed) |
model |
string | (optional) | Override the model for this sub-agent |
thinking |
string | (optional) | Override thinking level (off, low, medium, high, etc.) |
runTimeoutSeconds |
number | 0 (no limit) |
Abort the sub-agent after N seconds |
cleanup |
"delete" | "keep" |
"keep" |
"delete" archives immediately after announce |
Model Resolution Order
The sub-agent model is resolved in this order (first match wins):
- Explicit
modelparameter in thesessions_spawncall - Per-agent config:
agents.list[].subagents.model - Global default:
agents.defaults.subagents.model - Target agent’s normal model resolution for that new session
Thinking level is resolved in this order:
- Explicit
thinkingparameter in thesessions_spawncall - Per-agent config:
agents.list[].subagents.thinking - Global default:
agents.defaults.subagents.thinking - Otherwise no sub-agent-specific thinking override is applied
Cross-Agent Spawning
By default, sub-agents can only spawn under their own agent id. To allow an agent to spawn sub-agents under other agent ids:
{
agents: {
list: [
{
id: "orchestrator",
subagents: {
allowAgents: ["researcher", "coder"], // or ["*"] to allow any
},
},
],
},
}
Managing Sub-Agents (/subagents)
Use the /subagents slash command to inspect and control sub-agent runs for the current session:
| Command | Description |
|---|---|
/subagents list |
List all sub-agent runs (active and completed) |
/subagents stop <id|#|all> |
Stop a running sub-agent |
/subagents log <id|#> [limit] [tools] |
View sub-agent transcript |
/subagents info <id|#> |
Show detailed run metadata |
/subagents send <id|#> <message> |
Send a message to a running sub-agent |
You can reference sub-agents by list index (1, 2), run id prefix, full session key, or last.
```
🧭 Subagents (current session)
Active: 1 · Done: 2
1) ✅ · research logs · 2m31s · run a1b2c3d4 · agent:main:subagent:...
2) ✅ · check deps · 45s · run e5f6g7h8 · agent:main:subagent:...
3) 🔄 · deploy staging · 1m12s · run i9j0k1l2 · agent:main:subagent:...
```
```
/subagents stop 3
```
```
⚙️ Stop requested for deploy staging.
```
```
/subagents info 1
```
```
ℹ️ Subagent info
Status: ✅
Label: research logs
Task: Research the latest server error logs and summarize findings
Run: a1b2c3d4-...
Session: agent:main:subagent:...
Runtime: 2m31s
Cleanup: keep
Outcome: ok
```
```
/subagents log 1 10
```
Shows the last 10 messages from the sub-agent's transcript. Add `tools` to include tool call messages:
```
/subagents log 1 10 tools
```
```
/subagents send 3 "Also check the staging environment"
```
Sends a message into the running sub-agent's session and waits up to 30 seconds for a reply.
Announce (How Results Come Back)
When a sub-agent finishes, it goes through an announce step:
- The sub-agent's final reply is captured
- A summary message is sent to the main agent's session with the result, status, and stats
- The main agent posts a natural-language summary to your chat
Announce replies preserve thread/topic routing when available (Slack threads, Telegram topics, Matrix threads).
Announce Stats
Each announce includes a stats line with:
- Runtime duration
- Token usage (input/output/total)
- Estimated cost (when model pricing is configured via
models.providers.*.models[].cost) - Session key, session id, and transcript path
Announce Status
The announce message includes a status derived from the runtime outcome (not from model output):
- successful completion (
ok) — task completed normally - error — task failed (error details in notes)
- timeout — task exceeded
runTimeoutSeconds - unknown — status could not be determined
Tool Policy
By default, sub-agents get all tools except a set of denied tools that are unsafe or unnecessary for background tasks:
| Denied tool | Reason | |-------------|--------| | `sessions_list` | Session management — main agent orchestrates | | `sessions_history` | Session management — main agent orchestrates | | `sessions_send` | Session management — main agent orchestrates | | `sessions_spawn` | No nested fan-out (sub-agents cannot spawn sub-agents) | | `gateway` | System admin — dangerous from sub-agent | | `agents_list` | System admin | | `whatsapp_login` | Interactive setup — not a task | | `session_status` | Status/scheduling — main agent coordinates | | `cron` | Status/scheduling — main agent coordinates | | `memory_search` | Pass relevant info in spawn prompt instead | | `memory_get` | Pass relevant info in spawn prompt instead |Customizing Sub-Agent Tools
You can further restrict sub-agent tools:
{
tools: {
subagents: {
tools: {
// deny always wins over allow
deny: ["browser", "firecrawl"],
},
},
},
}
To restrict sub-agents to only specific tools:
{
tools: {
subagents: {
tools: {
allow: ["read", "exec", "process", "write", "edit", "apply_patch"],
// deny still wins if set
},
},
},
}
Authentication
Sub-agent auth is resolved by agent id, not by session type:
- The auth store is loaded from the target agent's
agentDir - The main agent's auth profiles are merged in as a fallback (agent profiles win on conflicts)
- The merge is additive — main profiles are always available as fallbacks
Context and System Prompt
Sub-agents receive a reduced system prompt compared to the main agent:
- Included: Tooling, Workspace, Runtime sections, plus
AGENTS.mdandTOOLS.md - Not included:
SOUL.md,IDENTITY.md,USER.md,HEARTBEAT.md,BOOTSTRAP.md
The sub-agent also receives a task-focused system prompt that instructs it to stay focused on the assigned task, complete it, and not act as the main agent.
Stopping Sub-Agents
| Method | Effect |
|---|---|
/stop in the chat |
Aborts the main session and all active sub-agent runs spawned from it |
/subagents stop <id> |
Stops a specific sub-agent without affecting the main session |
runTimeoutSeconds |
Automatically aborts the sub-agent run after the specified time |
Full Configuration Example
```json5 { agents: { defaults: { model: { primary: "anthropic/claude-sonnet-4" }, subagents: { model: "minimax/MiniMax-M2.1", thinking: "low", maxConcurrent: 4, archiveAfterMinutes: 30, }, }, list: [ { id: "main", default: true, name: "Personal Assistant", }, { id: "ops", name: "Ops Agent", subagents: { model: "anthropic/claude-sonnet-4", allowAgents: ["main"], // ops can spawn sub-agents under "main" }, }, ], }, tools: { subagents: { tools: { deny: ["browser"], // sub-agents can't use the browser }, }, }, } ```Limitations
- **Best-effort announce:** If the gateway restarts, pending announce work is lost. - **No nested spawning:** Sub-agents cannot spawn their own sub-agents. - **Shared resources:** Sub-agents share the gateway process; use `maxConcurrent` as a safety valve. - **Auto-archive is best-effort:** Pending archive timers are lost on gateway restart.See Also
- Session Tools — details on
sessions_spawnand other session tools - Multi-Agent Sandbox and Tools — per-agent tool restrictions and sandboxing
- Configuration —
agents.defaults.subagentsreference - Queue — how the
subagentlane works