feat(subagents): add multi-turn subagent session runtime

README.md

@@ -793,6 +793,35 @@ Or via tools:
 {"name":"council.run","args":{"task":"design a 30-day plan to cut CI flakiness by 50%"}}
 ```
 
+### Subagent Sessions (`subagent.*` tools)
+
+Flynn now supports multi-turn child agent sessions scoped to the current parent session.
+
+Available tools:
+
+- `subagent.spawn` — create a child session from an `agent_configs.<name>` profile
+- `subagent.send` — send follow-up work to an existing child session
+- `subagent.list` — list active child sessions
+- `subagent.cancel` — request cancellation for a running child turn
+- `subagent.delete` — remove a child session and clear its history
+
+Example flow:
+
+```json
+{"name":"subagent.spawn","args":{"agent":"research","subagent_id":"plan-research","task":"Survey backup strategies for a 3-node homelab."}}
+{"name":"subagent.send","args":{"subagent_id":"plan-research","message":"Now compare operational risk and recovery-time tradeoffs."}}
+{"name":"subagent.list","args":{}}
+```
+
+Config controls:
+
+```yaml
+agents:
+  subagents:
+    enabled: true
+    max_active_sessions: 6
+```
+
 ## Running as Service
 
 ### Ollama (Recommended)