Add orchestration send_event support

[andystaples]

Summary

• add synchronous OrchestrationContext.send_event(instance_id, event_name, *, data=None) for one-way orchestration-to-orchestration events
• emit deterministic SendEventAction records using the configured data converter and reconcile EventSent history during replay using .NET-compatible event-name matching
• record and deliver sent events in the in-memory backend without duplicate replay delivery, while dropping events for missing or terminal targets
• cover action creation, validation, custom and externalized payloads, replay nondeterminism, legacy entity-history compatibility, and end-to-end delivery

Validation

• python -m nox -s ci -- 3.14
• python -m nox -R -s core_tests-3.14 -- tests\durabletask\test_orchestration_executor.py tests\durabletask\test_orchestration_e2e.py tests\durabletask\test_large_payload.py -q
• python -m nox -R -s lint
• python -m nox -R -s typecheck_core-3.10

Closes #32

[Copilot]

Pull request overview

Adds orchestration-to-orchestration one-way event sending to the core Durable Task Python SDK, including deterministic action emission and replay reconciliation, plus in-memory backend delivery behavior and coverage.

Changes:

• Introduces OrchestrationContext.send_event(instance_id, event_name, *, data=None) and emits SendEventAction records using the configured DataConverter.
• Reconciles EventSent history during replay (including case-insensitive event-name matching) and wires action-type name resolution for sendEvent.
• Extends the in-memory backend to persist EventSent history and deliver/drop sent events safely without duplicate replay delivery; adds unit/E2E/large-payload tests and a changelog entry.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/durabletask/test_orchestration_executor.py	Adds unit tests covering send-event action creation, converter usage, validation, and replay nondeterminism behavior.
tests/durabletask/test_orchestration_e2e.py	Adds E2E coverage for orchestration-to-orchestration event delivery and replay-safe non-duplication behavior.
tests/durabletask/test_large_payload.py	Verifies large send-event payloads are externalized.
durabletask/worker.py	Implements send_event, reconciles EventSent during replay, and maps sendEvent actions to the correct method name.
durabletask/testing/in_memory_backend.py	Records EventSent history and delivers/drops send-event actions in the in-memory backend.
durabletask/task.py	Declares the public send_event API on OrchestrationContext.
durabletask/internal/helpers.py	Adds helpers to build SendEventAction and enrich EventSent history with an event name.
CHANGELOG.md	Documents the new OrchestrationContext.send_event() API under Unreleased/ADDED.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

durabletask/worker.py:3006

• When reconciling legacy entity EventSent history, a target-instance mismatch currently raises _get_wrong_action_type_error(..., task.get_name(ctx.send_event), ...), which produces a misleading NonDeterminismError message (it reports send_event even though the pending action is an entity call/signal/lock). This makes debugging replay mismatches harder.

Consider raising a NonDeterminismError that explicitly describes the instanceId mismatch and uses _get_method_name_for_action(action) (entity method) for the method name.

                    if entity_target != event.eventSent.instanceId:
                        raise _get_wrong_action_type_error(
                            event.eventId,
                            task.get_name(ctx.send_event),
                            action,
                        )

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

durabletask/worker.py:3375

• The NonDeterminismError text in this function uses "it's history" (contraction) instead of the possessive "its history"; this is user-facing and shows up in replay mismatch failures.

    )

[berndverst]

Re-reviewed at c09493d. Target-instance changes now fail replay deterministically, the public ABC remains backward compatible, and terminal event cleanup remains correct.