Observe claimed prepared executions

docs/consumers/pkg-promptkit.md

@@ -151,6 +151,14 @@ handling policy. The
 [engine operation GoDoc](../../engine.go) own exact lifecycle, engine-binding,
 credential, cancellation, timing, and error semantics.
 
+If the request supplied `Observer`, successful preparation retains that
+function for `RunPrepared`; preparation itself emits nothing. Observation
+starts only when the owning engine successfully claims the handle. Reused,
+discarded, foreign, and invalid handles emit nothing. `Discard` clears the
+retained callback without invoking it. The function's closure is retained by
+identity, so synchronize any shared state it uses. Prepared start events can
+include identities already resolved in the frozen snapshot.
+
 ## Execute And Validate
 
 [`Engine.Run`](../../engine.go) performs the same preparation, invokes the

docs/internal/observation.md

@@ -6,7 +6,10 @@ Its event values and callback type live in `internal/domain` so internal
 requests can carry them without depending on the recorder package. The
 recorder currently supplies run IDs to the runner and receives attempt and
 retry-delay measurements from the generation coordinator. Run lifecycle
-instrumentation from ordinary `Run` at the facade and runner boundaries.
+instrumentation for ordinary `Run` runs at the facade and runner boundaries.
+Prepared execution starts only after its private payload is atomically claimed;
+the facade receives that invocation's recorder privately and emits the terminal
+event after public error mapping. Failed claims and preparation emit nothing.
 
 A recorder keeps only counters, resolved identity fields, and the selected
 callback. It has no global history, queue, goroutine, or mutex held across a

docs/internal/runner.md

@@ -140,7 +140,8 @@ through context. Prompt and profile identities are enriched only after their
 respective resolutions succeed, before admission. The facade starts observation
 before request conversion and emits its terminal event after public error
 mapping and after the runner's deferred admission release. Preparation and
-prepared execution have no observation delivery yet.
+prepared execution follows the same terminal mapping after a successful claim;
+invalid or discarded handles do not acquire an observer.
 
 Validation preparation and execution honor cancellation at every
 Promptkit-controlled boundary and do not publish a partial plan or result.

docs/roadmap/implementation.md

@@ -407,6 +407,8 @@ guidance for ordinary observations only; run root and internal race tests; commi
 
 ## Stage 9 — Observe Prepared Execution Without Weakening Its Lifecycle
 
+**Completed:** 2026-09-23.
+
 Retain the adapted observer with the effective retries in the private prepared
 payload. Claim atomically before starting observation, release the claim mutex,
 install payload cleanup, then emit started. Preparation emits nothing; successful