{
  "id": "hook-surface:claude.subagent-start",
  "_kind": "HookSurface",
  "_file": "channels-hooks/hook-surfaces/native/claude-code-extended-hooks.yaml",
  "_cluster": "channels-hooks",
  "attributes": {
    "eventName": "SubagentStart (Claude Code)",
    "displayName": "SubagentStart (Claude Code)",
    "kind": "native",
    "originVendor": "Anthropic",
    "direction": "pre",
    "blocking": false,
    "family": "observer",
    "payloadSchema": {
      "type": "object",
      "required": [
        "hook_event_name",
        "agent_type",
        "agent_id",
        "prompt"
      ],
      "properties": {
        "hook_event_name": {
          "type": "string",
          "const": "SubagentStart"
        },
        "agent_type": {
          "type": "string"
        },
        "agent_id": {
          "type": "string"
        },
        "prompt": {
          "type": "string"
        }
      }
    },
    "description": "Fires when a subagent is spawned. Output limited to additionalContext\nvisible only to the user (not the subagent or parent). Used for UI\nindicators / telemetry. Matchable by agent_type.\n"
  },
  "outgoingEdges": [],
  "incomingEdges": [
    {
      "from": "agent-core-impl:claude-code.core@1.x",
      "to": "hook-surface:claude.subagent-start",
      "kind": "fires_hook",
      "attributes": {}
    },
    {
      "from": "agent-runtime-impl:claude-code.runtime@1.x",
      "to": "hook-surface:claude.subagent-start",
      "kind": "exposes",
      "attributes": {}
    },
    {
      "from": "hook-mapping:claude-subagent-start",
      "to": "hook-surface:claude.subagent-start",
      "kind": "maps_hook",
      "attributes": {}
    }
  ]
}