Trigger observability in the action graph

Harn projects trigger activity into both persisted run observability and the live dispatcher event stream. The current surface includes trigger, predicate, dispatch, a2a_hop, worker_enqueue, retry, and dlq nodes, plus the matching trigger_dispatch, predicate_gate, a2a_dispatch, retry, dlq_move, and replay_chain edges.

What lands in this change

• A synthetic trigger node is added when a run carries a trigger_event envelope in run.metadata.
• Workflow condition stages render as predicate nodes in observability.action_graph_nodes.
• Local dispatch attempts render as dispatch nodes.
• Remote A2A dispatch attempts render as a2a_hop nodes labelled with the resolved target_agent.
• worker://... queue handoffs render as worker_enqueue nodes with queue name, response topic, and job receipt metadata.
• Retry scheduling emits retry nodes with delay/error metadata.
• Exhausted deliveries emit dlq nodes with final-error metadata.
• Entry edges from the trigger node into the workflow render as trigger_dispatch.
• Trigger or predicate edges into a remote A2A hop render as a2a_dispatch.
• Transitions leaving a predicate on the workflow path render as predicate_gate.
• Replay-triggered dispatches add a visible replay_chain edge back to the original trigger event.
• trace_id propagates from the TriggerEvent onto the synthetic trigger node and every downstream action-graph node derived from that run, including A2A hops and worker queue receipts.
• A2A dispatches also send the same trace on the wire via the A2A-Trace-Id HTTP header in addition to the JSON envelope metadata.

The runtime streams these updates onto the shared event-log topic observability.action_graph. The portal subscribes to that topic for traced runs and merges live node/edge updates into the detail view while still showing the persisted run snapshot.

Portal view

The portal run detail now renders dedicated node cards instead of a plain edge dump:

• trigger cards show provider, event kind, signature status, and trace id
• predicate cards show pass/block state plus cost and latency
• A2A cards render with a dashed trust-boundary style and task metadata
• worker enqueue cards show queue and response-topic details
• DLQ and trigger cards expose a replay button that invokes harn trigger replay <event-id> through the portal backend

Node metadata

Each RunActionGraphNodeRecord now carries a metadata map so the portal and CLI consumers can render node-specific details without inventing a second schema. Representative fields include:

• trigger: provider, event_kind, dedupe_key, signature_status
• predicate: trigger_id, predicate, result, cost_usd, tokens, latency_ms, reason
• dispatch / a2a_hop / worker_enqueue: handler_kind, target_uri, attempt, plus route-specific fields like target_agent, task_id, queue_name, response_topic, and job_event_id
• retry: delay_ms, error
• dlq: attempt_count, final_error

Example

When a trigger is dispatched, the streamed action-graph updates now include records like:

{
  "kind": "trigger",
  "label": "cron:tick",
  "trace_id": "trace_123",
  "metadata": {
    "provider": "cron",
    "event_kind": "cron.tick",
    "signature_status": "unsigned"
  }
}

and:

{
  "kind": "worker_enqueue",
  "label": "worker://triage",
  "trace_id": "trace_123",
  "metadata": {
    "queue_name": "triage",
    "response_topic": "worker.triage.responses",
    "job_event_id": 42
  }
}

with edges such as:

{"kind": "trigger_dispatch", "from_id": "trigger:...", "to_id": "stage:..."}
{"kind": "predicate_gate", "label": "true"}
{"kind": "a2a_dispatch", "from_id": "predicate:...", "to_id": "a2a:..."}
{"kind": "retry", "from_id": "dispatch:...", "to_id": "retry:..."}
{"kind": "dlq_move", "from_id": "dispatch:...", "to_id": "dlq:..."}