Callback Registration¶
Delegation protocol — instantiates Cue-Triggered Intention Execution
Delegates cue-watching to an external system by registering a handler it will invoke — with context — the moment the awaited event completes.
Callback Registration hands the whole burden of watching to somebody else. Instead of holding an intention and looking out for its cue, you package the deferred action as a handler, register it with the system that owns the event, and walk away. When the event fires, that system calls you back — you never watched at all. Its defining move is this inversion of control: the actor who wants the action done does not monitor the cue and does not decide when to run; the party that detects the event does, and it re-supplies whatever context the handler needs to act. That is what separates it from the reminder and monitor mechanisms, which keep the watching on your own side of the fence. Callback Registration relocates the trigger's ownership entirely.
Example¶
A payments team needs to send a receipt email, but only after a charge has actually cleared the processor — which can take seconds or, for some banks, days. Polling the processor on a loop would be wasteful and fragile. Instead the team registers a webhook: they tell the processor, "when a charge with this ID reaches the settled state, POST to this URL." Now nobody on the team is watching anything. The intention — "send the receipt" — sleeps entirely inside the processor's own event machinery. Days later the bank confirms, the processor fires the webhook, and the request arrives carrying the full charge object: amount, customer, timestamp, idempotency key. The handler has everything it needs to send the right receipt without ever having kept the pending charge in mind. It sends the email, returns 200 OK, and the processor marks the callback delivered.
How it works¶
- Register, don't rehearse. The actor submits a handler (a URL, a function reference, a queue subscription) plus the event pattern it should fire on. Registration is the entire act of remembering; after it, the intention lives in the other system.
- Carry context in the invocation. A good callback is not a bare ping — it delivers a payload rich enough that the handler can act cold, having forgotten why it was ever registered.
- Acknowledge and consume. The handler's successful return closes the loop; the registration is typically one-shot (consumed on fire) or explicitly re-armed, so it neither leaks nor double-fires.
Tuning parameters¶
- Payload richness — a bare event name versus a full context object. Richer payloads let the handler act statelessly but couple it to the sender's schema and leak more data.
- Delivery guarantee — at-most-once, at-least-once, or exactly-once. Stronger guarantees cost acknowledgement round-trips and retry bookkeeping; weaker ones risk a silently dropped callback.
- Registration lifetime — one-shot versus durable subscription, and whether stale registrations expire. Durable ones catch repeat events but accumulate as debt if never de-registered.
- Failure handling — what the owning system does when the handler errors or times out: drop, retry with backoff, or dead-letter.
When it helps, and when it misleads¶
Its strength is that it eliminates watching altogether for the delegating party — no polling, no rehearsal, no attention spent on an event that may be far off. It scales to millions of pending intentions because each one costs only a registration record, and it wakes precisely on the event rather than on a schedule. The Hollywood principle — "don't call us, we'll call you" — captures exactly this relief.[n1]
Its failure mode is that you have handed control away. If the owning system never fires — the event is lost, the subscription silently expires, the webhook endpoint was misconfigured — your intention simply never runs, and because you stopped watching, nothing on your side notices. Callbacks that arrive without enough context force the handler to reconstruct state it no longer has, and duplicate deliveries run the action twice. The discipline is to make handlers idempotent, to instrument the owning system for undelivered callbacks, and to pair long-lived registrations with an independent staleness sweep rather than trusting the delegate absolutely.
How it implements the components¶
Callback Registration fills the delegation-and-handoff side of the machinery:
delegated_trigger_owner— registration transfers cue-ownership wholesale: the external system becomes responsible for detecting the event and invoking the handler.context_reinstatement_prompt— the callback invocation carries a payload that re-supplies the intention's context, so the handler acts without having held anything in memory.action_closure_signal— the handler's acknowledged return records execution and consumes the one-shot registration, keeping the loop from re-firing.
It does not itself watch a condition or decide whether to run — the continuous parallel_cue_monitor and the retrieval_and_execution_gate are the Event Listener or Monitoring Daemon's, which keeps the watching on its own side rather than delegating it.
Related¶
- Instantiates: Cue-Triggered Intention Execution — it supplies the delegated-ownership variant, where the environment's other actor does the retrieval work.
- Sibling mechanisms: Event Listener or Monitoring Daemon · Event-Based Reminder · Execution Acknowledgement Loop · Time-Based Reminder · Cue Disambiguation Test · Deferred-Action Checklist Marker · Environmental Prompt Placement · Missed Trigger Review
Editorial Notes¶
Form Classification¶
Form family: Protocol, Workflow & Routine
Rationale: The actor registers an event pattern, handler, context payload, acknowledgement, and consumption behavior with an external system, so its operative form is a callback protocol.
Nearest alternative: Control, Automation & Runtime — The external system invokes the handler automatically, but the mechanism described is the registration and handoff enactment.
Review outcome: Adjudicated after independent review; high confidence.
Origin Attribution¶
Primary origin: Computer Science & Software Engineering
Origin pattern: Single lineage
Present-day reach: Specialized
Rationale: Event-driven software and inversion-of-control frameworks established handler registration for later contextual invocation by the event owner.
Review resolution: Computer science is primary because event loops and inversion-of-control systems register handlers that later receive completion context. The recognizable method is specialized software infrastructure even though the delegation pattern is metaphorically portable.
Review outcome: Reconciled after independent review; high confidence.
Notes¶
[n1] Inversion of control (colloquially the "Hollywood principle": "don't call us, we'll call you") — a design in which a framework or external system, rather than your own code, decides when to invoke your handler. Registering a callback is the canonical instance: control over when the action runs is inverted to the party that owns the event. ↩