WIP [ci skip]

docs/adr/0021-permanently-end-processes.md

@@ -0,0 +1,31 @@
+# 21. Permanently End Processes
+
+Date: 2024-08-07
+
+## Status
+
+Proposed
+
+- Amends [19. Automatic Process Creation](0019-automatic-process-creation.md)
+
+## Context
+
+When an event is routed to a process instance that has ended, the process
+instance is "restarted" with a new root value obtained from
+`ProcessMessageHandler.New()`.
+
+This behavior is surprising to users, and it is unclear how to handle events
+that arrive after the process has ended.
+
+## Decision
+
+We will change the specification such that an engine must not call
+`ProcessMessageHandler.HandleEvent()` with any event that is routed to an
+instance that has been ended.
+
+This ADR does not propose any chanes to the behavior of timeout messages, which
+are already discarded when a process ends.
+
+## Consequences
+
+TODO

docs/adr/README.md

@@ -31,3 +31,4 @@ the ADR documents.
 * [18. Compacting Projection Data](0018-projection-compaction.md)
 * [16. Automatic Process Creation](0019-automatic-process-creation.md)
 * [20. Constraints on Identifier Values](0020-identifier-constraints.md)
+* [21. Permanently End Processes](0021-permanently-end-processes.md)