Event Runtime

AxEventRuntime is the protocol-neutral layer for autonomous work:

source → inbox → explicit route → AxGen/AxAgent/AxFlow → persisted output → sinks

MCP subscriptions, UCP webhooks, timers, queues, and application events all use the same envelope, trust policy, continuation, cancellation, and tracing model. Source callbacks publish events; they never call a model directly.

For MCP, the endpoint catalog and managed resource policy are separate from the wake route. See MCP Subscriptions.

flowchart LR
  Source["Source or protocol adapter"] --> Inbox["Event inbox"]
  Inbox --> Policy["Route action and trust gate"]
  Policy -->|observe| Store["Persist event"]
  Policy -->|invalidate| Cache["Refresh catalog or cache"]
  Policy -->|wake or resume| Program["AxGen, AxAgent, or AxFlow"]
  Program --> Output["Persist output"]
  Output --> Sinks["Retry sinks independently"]

Wake

A wake route starts a typed target. The program signature is the destination contract: segment-safe eventPath descriptors project or rename selected event values, and invalid or missing fields dead-letter before invocation. Ax never fabricates a user message from event data. Use multiple matching routes when one event should wake multiple Agents so each keeps independent authorization, ordering, retries, and run records.

Source

Python

runtime.start()
if not completed.wait(60):
runtime.close()

Resume

A resume route atomically consumes an identity-scoped continuation. State envelopes carry schema and program versions; unsupported migrations dead-letter instead of crossing program versions silently.

Targets can declare different .wakeInput() and .resumeInput() plans. The action-specific plan wins and neither action silently falls back to the other. .waitFor(kind, path) creates a continuation from verified ingress without putting protocol data into a user message.

Source

Python

runtime.start()
started.publish(
if not completed.wait(60):

UCP Webhooks

The application owns HTTP hosting. AxUCPWebhookEventSource.ingest(request) verifies the signer profile, RFC 9421 signature, freshness, digest, and replay state before enqueue. Application identity mapping happens afterward and remains outside the business payload.

Source

Python

const receipt = await source.ingest(request);
  if (!receipt.accepted) return new Response(null, { status: 503 });

Store Guarantees

AxInMemoryEventStore is volatile and single-worker. It is useful for development and retries within one process, but it makes no crash-recovery claim.

The Node-only SQLite store supplies transactional enqueue, output persistence, leases, fencing, compare-and-set state, and cooperating-process recovery for workers sharing a local SQLite file. It is not recommended on a network filesystem. Other stores must pass the event-store conformance kit before advertising persistent or multi-worker capability.

Output is persisted before sink dispatch. Sink retries use (runId, sinkId) idempotency keys and never repeat a completed model call. A possible post-side-effect crash becomes outcome_unknown rather than an automatic replay.

Generated Python, Java, C++, Go, and Rust packages provide a deterministic inline single-worker runtime. Sources publish into the runtime and due deliveries invoke targets automatically; there is no hidden worker thread. Their shared lifecycle conformance covers retry, state restoration, continuations, cooperative cancellation, dead letters, and sink-only redrive.

See MCP and the Event Runtime maintainer guide.