Changeset 0.28.6 (#192)

docs/ICD/tasks.md

@@ -65,8 +65,17 @@ POST /tasks
 ```
 
 `task_type`: `prompt` (direct LLM execution), `workflow` (deferred —
-not yet implemented; creation is rejected at the API), or `action`
-(no LLM — relay/webhook only; requires `task.action` permission).
+not yet implemented; creation is rejected at the API), `action`
+(no LLM — relay/webhook only; requires `task.action` permission),
+or `system` (v0.28.6 — built-in Go function, admin-only).
+
+System tasks require `system_function` — a registered function name
+from the platform's Go function registry. No LLM, no provider
+resolution, no channel needed. The function receives the store set
+and returns a result string. Designed for core platform ops
+(`session_cleanup`, `staleness_check`, `retention_sweep`, `health_prune`)
+that must not break from bad user code. Permanent track — not replaced
+by Starlark in v0.29.0.
 
 `schedule`: cron expression, `once`, or `webhook`. Supported cron
 patterns: `@hourly`, `@daily`, `@weekly`, `*/N * * * *` (every N
@@ -173,6 +182,26 @@ Returns `410 Gone` if the task is inactive.
 **Rate limiting:** Governed by global request rate limits. No per-task
 rate limiting in v0.28 — defer to a future version if needed.
 
+### Task-to-Task Chaining (v0.28.6)
+
+Tasks can trigger other tasks by setting the `webhook_url` of Task A
+to the trigger URL of Task B:
+
+1. Create **Task B** with `schedule: "webhook"`. Note the trigger URL
+   from the response (`/api/v1/hooks/t/{trigger_token}`).
+2. Create **Task A** with `output_mode: "webhook"` and set `webhook_url`
+   to Task B's trigger URL.
+3. When Task A completes, its output is POSTed to Task B's trigger URL.
+   Task B starts with Task A's output as its `trigger_payload`.
+
+This enables multi-step pipelines without external orchestration:
+- Task A: "Summarize today's news" (prompt, cron: 6am)
+- Task B: "Format and post to Slack" (action, webhook-triggered)
+
+The `webhook_secret` on Task A signs outbound payloads with HMAC-SHA256.
+Task B's trigger endpoint does not currently verify signatures (the
+trigger token itself is the auth mechanism).
+
 ## Team Tasks
 
 Team-scoped tasks visible to all team members, manageable by team admins.
@@ -240,6 +269,30 @@ DELETE /admin/tasks/:id
 
 **Auth:** Platform admin.
 
+### System Functions (v0.28.6)
+
+```
+GET /admin/system-functions → { "data": [SystemFuncInfo, ...] }
+```
+
+Returns all registered built-in system function names and descriptions.
+Used by the admin UI to populate the function dropdown when creating
+system tasks.
+
+**SystemFuncInfo:**
+
+```json
+{
+  "name": "session_cleanup",
+  "description": "Remove expired anonymous visitor sessions"
+}
+```
+
+Built-in functions (v0.28.6): `session_cleanup`, `staleness_check`,
+`retention_sweep`, `health_prune`.
+
+**Auth:** Platform admin.
+
 ## Task Object
 
 ```json
@@ -250,7 +303,8 @@ DELETE /admin/tasks/:id
   "name": "Morning News Digest",
   "description": "...",
   "scope": "personal|team|global",
-  "task_type": "prompt|workflow|action",
+  "task_type": "prompt|workflow|action|system",
+  "system_function": "session_cleanup",
   "persona_id": "uuid|null",
   "model_id": "claude-sonnet-4-20250514",
   "system_prompt": "...",