Observe claimed prepared executions

internal/domain/domain.go

@@ -71,6 +71,7 @@ type RunRequest struct {
 	Validation       *OutputContract
 	AppendedMessages []RenderedMessage
 	TransientRetries *int
+	Observer         ExecutionObserver `json:"-"`
 }
 
 // RunResult represents the complete result of a prompt execution run.

internal/observation/recorder.go

@@ -202,6 +202,21 @@ func FromContext(ctx context.Context) *Recorder {
 	return recorder
 }
 
+type claimSinkKey struct{}
+
+// WithClaimSink lets the facade learn which invocation actually claimed a
+// prepared handle, so it can emit the terminal event after public mapping.
+func WithClaimSink(ctx context.Context, sink **Recorder) context.Context {
+	return context.WithValue(ctx, claimSinkKey{}, sink)
+}
+
+// RegisterClaim records an invocation after its prepared handle is claimed.
+func RegisterClaim(ctx context.Context, recorder *Recorder) {
+	if sink, ok := ctx.Value(claimSinkKey{}).(**Recorder); ok && sink != nil {
+		*sink = recorder
+	}
+}
+
 type usageField struct {
 	value           int
 	known, complete bool

internal/usecase/prepared_execution.go

@@ -34,6 +34,7 @@ type preparedExecutionPayload struct {
 	validation       validate.PreparedValidation
 	directKey        string
 	transientRetries uint64
+	observer         domain.ExecutionObserver
 }
 
 // PrepareExecution completes preparation without generation or admission and
@@ -68,6 +69,7 @@ func (r *Runner) PrepareExecution(ctx context.Context, req domain.RunRequest) (*
 			validation:       operation.validation,
 			directKey:        state.effectiveModel.APIKey,
 			transientRetries: state.transientRetries,
+			observer:         req.Observer,
 		},
 	}, nil
 }
@@ -115,9 +117,28 @@ func (r *Runner) RunPrepared(ctx context.Context, prepared *PreparedExecution) (
 	}
 	defer payload.clear()
 
-	runID, err := observation.NewRunID()
-	if err != nil {
-		return nil, fmt.Errorf("failed to create run id: %w", err)
+	var recorder *observation.Recorder
+	var runID string
+	if payload.observer != nil {
+		var idErr error
+		recorder, idErr = observation.New(payload.observer)
+		observation.RegisterClaim(ctx, recorder)
+		ctx = observation.WithRecorder(ctx, recorder)
+		selected := payload.prepared
+		recorder.UpdateSelection(observation.Selection{PromptID: selected.PromptID,
+			PromptVersion: selected.PromptVersion, ProfileID: selected.SelectedProfileID,
+			BackendID: selected.SelectedBackendID, Model: selected.EffectiveModelParams.Model})
+		recorder.Start()
+		if idErr != nil {
+			return nil, fmt.Errorf("failed to create run id: %w", idErr)
+		}
+		runID = recorder.RunID()
+	} else {
+		var err error
+		runID, err = observation.NewRunID()
+		if err != nil {
+			return nil, fmt.Errorf("failed to create run id: %w", err)
+		}
 	}
 	start := time.Now().UTC()
 
@@ -173,6 +194,7 @@ func (p *preparedExecutionPayload) clear() {
 	p.validation = nil
 	p.directKey = ""
 	p.transientRetries = 0
+	p.observer = nil
 }
 
 type noOpPreparedValidation struct {