diff --git a/docs/consumers/pkg-promptkit.md b/docs/consumers/pkg-promptkit.md
index 50cb346..7c27c42 100644
--- a/docs/consumers/pkg-promptkit.md
+++ b/docs/consumers/pkg-promptkit.md
@@ -581,6 +581,59 @@ 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.
 
+## Bound Execution And Retain Prepared Details
+
+Select the optional controls on [RunRequest](../../types.go). The operation
+budget is separate from the provider timeout and cancellation is cooperative.
+Notification is conditional on reaching the prepared point, synchronous, and
+runs while admission is held; its caller-owned details can be retained even if
+generation later fails. Do not rely on notification for preparation or admission
+failures. The application owns any subsequent diagnostic handling.
+
+```go
+var details *promptkit.PreparedRun
+result, err := engine.Run(ctx, promptkit.RunRequest{
+	PromptID: "answer", OperationTimeout: 30 * time.Second,
+	OnPrepared: func(_ context.Context, prepared promptkit.PreparedRun) { details = &prepared },
+})
+if errors.Is(err, promptkit.ErrOperationTimeout) && errors.Is(err, context.DeadlineExceeded) {
+	// details is available only if the notification was reached.
+}
+```
+
+For coordinated turns, put the controls on each returned request. Assessment
+in the next-turn callback runs after the previous admission and child scope
+are released, so it can select its own budget:
+
+```go
+next := func(ctx context.Context, turn promptkit.ConversationTurn) (*promptkit.RunRequest, error) {
+	if turn.Result != nil {
+		_, err := engine.Run(ctx, promptkit.RunRequest{PromptID: "assessment", OperationTimeout: 10 * time.Second})
+		return nil, err
+	}
+	return &promptkit.RunRequest{PromptID: "answer", OperationTimeout: 30 * time.Second,
+		OnPrepared: func(_ context.Context, prepared promptkit.PreparedRun) { details = &prepared }}, nil
+}
+```
+
+For split execution, [PrepareExecution](../../engine.go) retains the controls
+without starting their timer; idle time does not count. Use the same caller
+deadline for both calls if preparation and execution need one shared bound.
+
+```go
+handle, err := engine.PrepareExecution(ctx, promptkit.RunRequest{
+	PromptID: "answer", OperationTimeout: 30 * time.Second,
+	OnPrepared: func(_ context.Context, prepared promptkit.PreparedRun) { details = &prepared },
+})
+if err != nil { return err }
+defer handle.Discard()
+result, err := engine.RunPrepared(ctx, handle)
+```
+
+See the [observation example](../../examples/go-library/observe/main.go) for an
+offline coordinated workflow and [ErrOperationTimeout](../../engine.go) for
+timeout attribution.
+
 ## Execute And Validate
 
 [`Engine.Run`](../../engine.go) performs the same preparation, invokes the
diff --git a/docs/internal/observation.md b/docs/internal/observation.md
index 0693c15..baba922 100644
--- a/docs/internal/observation.md
+++ b/docs/internal/observation.md
@@ -14,6 +14,9 @@ The public projection retains private operation-owner metadata separately from
 inspectable child causes. Terminal classification uses that owner, preserving
 context precedence and generation-specific transport/provider details rather
 than mistaking a collaborator's nested lookup error for the parent's operation.
+Timeout attribution is finalized and the child scope released before terminal
+delivery, so observer latency cannot change the already selected outcome.
+Prepared-content notification is a separate opt-in callback, not an event.
 
 The facade masks inherited recorder and prepared-claim state when entering
 preparation or execution. Delegated calls from an injected collaborator retain
diff --git a/docs/internal/overview.md b/docs/internal/overview.md
index aa81388..acc054a 100644
--- a/docs/internal/overview.md
+++ b/docs/internal/overview.md
@@ -14,7 +14,7 @@ contributor workflow and validation.
 | Root `promptkit` package | Provides the supported engine facade, ConfigKit source helpers, collection and resource mapping conveniences, injection options, public requests and results, resource and requirement inspection and identity inventories, concrete-request validation, explicit smoke diagnostics, observation values, opaque prepared-execution handles, value conversion, redacted formatting, and typed capacity and generation error mapping. | [Package GoDoc](../../doc.go), [observations](../../observations.go), [prepared execution](../../prepared_execution.go), [backend API](../../backends.go), [engine facade](../../engine.go), [smoke diagnostics](../../smoke_diagnostics.go), [identity listing](../../listing.go), [requirement facade](../../requirements.go) |
 | `examples/go-library/prepare` | Demonstrates offline preparation from two explicitly selected synthetic collections, source-relative imported content, a scoped view, filtered listings, and operator inventory. It is not a public library package. | [Example program](../../examples/go-library/prepare/main.go), [collection inputs](../../examples/go-library/prepare/collections/support/collection.yaml) |
 | `examples/go-library/run` | Demonstrates an offline downstream consumer using a prompt file, programmatic profile, inline input, an injected deterministic model client, and `Run`. It is not a public library package. | [Example program](../../examples/go-library/run/main.go) |
-| `examples/go-library/observe` | Demonstrates offline built-in HTTP retry and synchronous metadata observation across structured proposal and assessment runs using embedded sources, two profiles on one finite backend, and an application decision. It is not a public library package. | [Example program](../../examples/go-library/observe/main.go) |
+| `examples/go-library/observe` | Demonstrates offline retry, observation, prepared notification, and separately budgeted coordinated proposal and assessment runs using two profiles on one finite backend. It is not a public library package. | [Example program](../../examples/go-library/observe/main.go) |
 | `internal/backend` | Holds a defensive, immutable lookup of final backend definitions, including diagnostic metadata, plus capacity policies validated by the configuration adapter. | [Backend registry](../../internal/backend/registry.go) |
 | `internal/configuration` | Loads root and namespaced resources through ConfigKit; validates final values, captures indexed resource views and source-relative prompt content, compiled templates, requirement metadata, identity inventories, backend and presence-aware execution profiles, and the read-only provenance inspection view. | [Typed loader](../../internal/configuration/load.go), [identity listing](../../internal/configuration/listing.go), [internal sources](sources.md#typed-configuration-loading) |
 | `internal/capacity` | Owns engine-local bounded execution admission and FIFO model-generation permits for limited backend IDs, including cancellation-safe waiter removal and client wrapping. | [Internal capacity management](capacity.md) |
diff --git a/docs/internal/runner.md b/docs/internal/runner.md
index 56ef8a2..3a8abea 100644
--- a/docs/internal/runner.md
+++ b/docs/internal/runner.md
@@ -209,6 +209,16 @@ mapping and after the runner's deferred admission release. Preparation and
 prepared execution follows the same terminal mapping after a successful claim;
 invalid or discarded handles do not acquire an observer.
 
+The facade establishes an optional operation scope for ordinary runs before
+observation and preparation. A claimed prepared execution establishes its own
+scope from the retained duration; preparation and idle time do not consume it.
+The shared scope finalizer marks only a context failure caused by that scope's
+own deadline, preserving its underlying operation and cause. The scope is
+released before terminal delivery. At the shared prepared execution boundary,
+the runner conditionally invokes the adapter for the actual prepared snapshot
+while admission is held, with context checks before and after notification.
+The facade adapter projects a detached public value only when selected.
+
 Validation preparation and execution honor cancellation at every
 Promptkit-controlled boundary and do not publish a partial plan or result.
 Schema reads are bounded and context-checked between chunks; JSON decoding,
diff --git a/docs/roadmap/implementation.md b/docs/roadmap/implementation.md
index c29a528..481e8fe 100644
--- a/docs/roadmap/implementation.md
+++ b/docs/roadmap/implementation.md
@@ -398,6 +398,8 @@ be redesigned solely because its ordinary run gained options.
 
 ## Stage 8: Document, Demonstrate, And Validate The Assembled Feature
 
+Status: complete.
+
 Outcome: the implementation and its supported consumer workflow are complete,
 with documentation in the canonical owners.
 
diff --git a/engine.go b/engine.go
index 009441e..c1c3c5f 100644
--- a/engine.go
+++ b/engine.go
@@ -63,6 +63,9 @@ var (
 	// ErrOperationTimeout identifies expiration of the timeout selected by
 	// RunRequest.OperationTimeout. Such errors also match context.DeadlineExceeded
 	// and retain their underlying operation and collaborator identities.
+	// Earlier parent cancellation or deadlines and provider-only deadlines do
+	// not acquire this identity. A completed result remains completed even if
+	// a terminal observer outlasts the selected budget.
 	ErrOperationTimeout = errors.New("operation timeout exceeded")
 	// ErrLLMGenerate identifies a model-client failure or a nil successful
 	// response. A built-in OpenAI-compatible non-2xx response is available as a
@@ -390,6 +393,7 @@ func (e *Engine) InspectBackend(ctx context.Context, backendID string) (*Backend
 // reported in the applicable operation category; no general errors.Is
 // relationship to ctx.Err is promised. Prepare returns no partial result on
 // error. It validates RunRequest.TransientRetries but makes no model attempts.
+// RunRequest.OperationTimeout and RunRequest.OnPrepared have no effect here.
 func (e *Engine) Prepare(ctx context.Context, req RunRequest) (*PreparedRun, error) {
 	prepared, err := e.prepareRequest(ctx, req)
 	if err != nil {
@@ -411,6 +415,7 @@ func (e *Engine) Prepare(ctx context.Context, req RunRequest) (*PreparedRun, err
 // matching ErrInvalidConfig when the Engine is nil. Success does not guarantee
 // provider acceptance or later execution success. Use [Engine.PrepareExecution]
 // when execution must use the snapshot produced by preparation.
+// Execution-only controls do not start a timer or invoke a notification here.
 func (e *Engine) ValidateRequest(ctx context.Context, req RunRequest) error {
 	_, err := e.prepareRequest(ctx, req)
 	return err
@@ -453,6 +458,8 @@ func (e *Engine) prepareRequest(ctx context.Context, req RunRequest) (*domain.Pr
 // ErrInvalidConfig. The effective transient retry budget is frozen privately
 // for RunPrepared and is absent from Details. A supplied Observer is retained
 // privately for RunPrepared; preparation itself emits no events.
+// RunRequest.OperationTimeout and RunRequest.OnPrepared are retained without
+// starting a timer or invoking the notification during preparation.
 func (e *Engine) PrepareExecution(ctx context.Context, req RunRequest) (*PreparedExecution, error) {
 	ctx = observation.WithoutExecutionState(ctx)
 	if e == nil || e.internal == nil {
@@ -483,6 +490,9 @@ func (e *Engine) PrepareExecution(ctx context.Context, req RunRequest) (*Prepare
 // returns the final failed validation result with cumulative usage and actual
 // repair attempts. An inability to generate or validate returns an error and
 // no partial result.
+// RunRequest.OperationTimeout selects a cooperative whole-operation deadline;
+// RunRequest.OnPrepared selects conditional notification before generation.
+// The outcome and timeout attribution are fixed before terminal observation.
 //
 // The built-in client retries eligible provider statuses using the effective
 // Config or request budget. With R additional transient attempts and P repair
@@ -600,6 +610,9 @@ func (e *Engine) run(ctx context.Context, req RunRequest) (*RunResult, error) {
 // mapping. Invalid, foreign, discarded, or reused handles emit no events.
 // Callbacks run outside the handle and capacity locks; panics propagate and
 // do not promise a terminal event.
+// The retained RunRequest.OperationTimeout starts after claim; the retained
+// RunRequest.OnPrepared is notified only if execution reaches its prepared
+// point. Final timeout attribution precedes terminal observation.
 func (e *Engine) RunPrepared(ctx context.Context, prepared *PreparedExecution) (*RunResult, error) {
 	ctx = observation.WithoutExecutionState(ctx)
 	if e == nil || e.internal == nil {
diff --git a/examples/go-library/observe/main.go b/examples/go-library/observe/main.go
index ab2575d..80fe960 100644
--- a/examples/go-library/observe/main.go
+++ b/examples/go-library/observe/main.go
@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"os"
 	"strings"
+	"time"
 
 	"go.maximumdirect.net/configkit"
 	"go.maximumdirect.net/promptkit"
@@ -79,6 +80,8 @@ type summary struct {
 	ExhaustedOutcome           promptkit.CoordinationOutcome `json:"exhausted_outcome"`
 	GroupMembers               int                           `json:"group_members"`
 	GroupAttempts              uint64                        `json:"group_attempts"`
+	PreparedMessages           int                           `json:"prepared_messages"`
+	PreparedParentMatches      bool                          `json:"prepared_parent_matches"`
 }
 
 func run() (summary, error) {
@@ -123,17 +126,18 @@ func run() (summary, error) {
 		return summary{}, err
 	}
 	var assessmentLog eventLog
+	var preparedDetails promptkit.PreparedRun
 	decision := "rejected"
 	coordination, err := engine.Coordinate(context.Background(), promptkit.CoordinateRequest{
 		Start: proposal.Exchange, AdditionalTurns: 1, Observer: executions.Observe,
 		Next: func(ctx context.Context, turn promptkit.ConversationTurn) (*promptkit.RunRequest, error) {
 			if turn.Result == nil {
-				return &promptkit.RunRequest{PromptID: "example.proposal", Inputs: map[string]promptkit.ArtifactRef{"idea": promptkit.Inline("Refine the proposal.")}}, nil
+				return &promptkit.RunRequest{PromptID: "example.proposal", Inputs: map[string]promptkit.ArtifactRef{"idea": promptkit.Inline("Refine the proposal.")}, OperationTimeout: 10 * time.Second, OnPrepared: func(_ context.Context, details promptkit.PreparedRun) { preparedDetails = details }}, nil
 			}
 			if !turn.Result.Validation.IsValid {
 				return nil, fmt.Errorf("follow-up failed structural validation")
 			}
-			assessment, err := engine.Run(ctx, promptkit.RunRequest{PromptID: "example.assessment", Inputs: map[string]promptkit.ArtifactRef{"proposal": promptkit.Inline(turn.Result.RawOutput)}, Observer: promptkit.ComposeObservers(assessmentLog.record, executions.Observe)})
+			assessment, err := engine.Run(ctx, promptkit.RunRequest{PromptID: "example.assessment", Inputs: map[string]promptkit.ArtifactRef{"proposal": promptkit.Inline(turn.Result.RawOutput)}, OperationTimeout: 10 * time.Second, Observer: promptkit.ComposeObservers(assessmentLog.record, executions.Observe)})
 			if err != nil {
 				return nil, err
 			}
@@ -183,6 +187,8 @@ func run() (summary, error) {
 		ExhaustedOutcome:           exhausted.Outcome,
 		GroupMembers:               len(group.Members),
 		GroupAttempts:              group.Attempts,
+		PreparedMessages:           len(preparedDetails.Messages),
+		PreparedParentMatches:      preparedDetails.ParentRunID == proposal.RunID,
 	}, nil
 }
 
diff --git a/examples/go-library/observe/main_test.go b/examples/go-library/observe/main_test.go
index 7f331a1..e986bf2 100644
--- a/examples/go-library/observe/main_test.go
+++ b/examples/go-library/observe/main_test.go
@@ -12,23 +12,25 @@ func TestObserveExample(t *testing.T) {
 		t.Fatal(err)
 	}
 	var got struct {
-		ProposalAttempts    *int   `json:"proposal_attempts"`
-		ProposalRetries     *int   `json:"proposal_transient_retries"`
-		UsageComplete       *bool  `json:"proposal_usage_complete"`
-		AssessmentAttempts  *int   `json:"assessment_attempts"`
-		AssessmentRetries   *int   `json:"assessment_transient_retries"`
-		Outcome             string `json:"assessment_outcome"`
-		CoordinationOutcome string `json:"coordination_outcome"`
-		ExhaustedOutcome    string `json:"exhausted_outcome"`
-		GroupMembers        int    `json:"group_members"`
-		GroupAttempts       int    `json:"group_attempts"`
+		ProposalAttempts      *int   `json:"proposal_attempts"`
+		ProposalRetries       *int   `json:"proposal_transient_retries"`
+		UsageComplete         *bool  `json:"proposal_usage_complete"`
+		AssessmentAttempts    *int   `json:"assessment_attempts"`
+		AssessmentRetries     *int   `json:"assessment_transient_retries"`
+		Outcome               string `json:"assessment_outcome"`
+		CoordinationOutcome   string `json:"coordination_outcome"`
+		ExhaustedOutcome      string `json:"exhausted_outcome"`
+		GroupMembers          int    `json:"group_members"`
+		GroupAttempts         int    `json:"group_attempts"`
+		PreparedMessages      int    `json:"prepared_messages"`
+		PreparedParentMatches bool   `json:"prepared_parent_matches"`
 	}
 	if err := json.Unmarshal(output.Bytes(), &got); err != nil {
 		t.Fatal(err)
 	}
 	if got.ProposalAttempts == nil || *got.ProposalAttempts != 2 || got.ProposalRetries == nil || *got.ProposalRetries != 1 ||
 		got.UsageComplete == nil || *got.UsageComplete || got.AssessmentAttempts == nil || *got.AssessmentAttempts != 1 ||
-		got.AssessmentRetries == nil || *got.AssessmentRetries != 0 || got.Outcome != "accepted" || got.CoordinationOutcome != "stopped" || got.ExhaustedOutcome != "exhausted" || got.GroupMembers != 3 || got.GroupAttempts != 4 {
+		got.AssessmentRetries == nil || *got.AssessmentRetries != 0 || got.Outcome != "accepted" || got.CoordinationOutcome != "stopped" || got.ExhaustedOutcome != "exhausted" || got.GroupMembers != 3 || got.GroupAttempts != 4 || got.PreparedMessages < 3 || !got.PreparedParentMatches {
 		t.Fatalf("unexpected observation summary: %+v", got)
 	}
 }
diff --git a/execution_timeout_contract_test.go b/execution_timeout_contract_test.go
index d9ba559..a64c296 100644
--- a/execution_timeout_contract_test.go
+++ b/execution_timeout_contract_test.go
@@ -79,3 +79,22 @@ func TestPreparedExecutionRespectsCallerDeadline(t *testing.T) {
 		}
 	})
 }
+
+func TestPreparedExecutionDoesNotTimePreparation(t *testing.T) {
+	synctest.Test(t, func(t *testing.T) {
+		release := make(chan struct{})
+		reader := &capacityArtifactReader{entered: make(chan struct{}, 1), release: release}
+		engine := newBackendCapacityEngine(t, newCapacityGateClient(closedCapacityChannel(), 1), 1, capacityInt(0), reader)
+		req := capacityInputRequest("http://example.invalid/v1")
+		req.OperationTimeout = time.Second
+		go func() { time.Sleep(2 * time.Second); close(release) }()
+		start := time.Now()
+		handle, err := engine.PrepareExecution(context.Background(), req)
+		if err != nil || time.Since(start) != 2*time.Second {
+			t.Fatalf("prepare elapsed=%v error=%v", time.Since(start), err)
+		}
+		if _, err = engine.RunPrepared(context.Background(), handle); err != nil {
+			t.Fatalf("execution after preparation: %v", err)
+		}
+	})
+}
diff --git a/prepared_execution.go b/prepared_execution.go
index 48e8e0f..9e43956 100644
--- a/prepared_execution.go
+++ b/prepared_execution.go
@@ -18,6 +18,9 @@ const preparedExecutionString = "promptkit.PreparedExecution{opaque}"
 // It also retains RunRequest.CaptureExchange and RunRequest.ContinueFrom for
 // execution of the frozen snapshot. Only RunPrepared can produce its completed
 // [Exchange]; preparation alone does not.
+// RunRequest.OperationTimeout and RunRequest.OnPrepared are retained as
+// selections without an active idle timer; their execution lifecycle is
+// described on those fields.
 type PreparedExecution struct {
 	internal *usecase.PreparedExecution
 }
diff --git a/types.go b/types.go
index 1978073..64ea93e 100644
--- a/types.go
+++ b/types.go
@@ -89,7 +89,10 @@ type RunRequest struct {
 	// applies it across preparation and execution; PrepareExecution retains it
 	// for RunPrepared, without counting preparation or idle time. Zero or a
 	// negative value selects no additional timeout. This is independent of the
-	// provider generation timeout. Cancellation remains cooperative.
+	// provider generation timeout and respects earlier parent cancellation or
+	// deadlines. Local timeout failures match ErrOperationTimeout and
+	// context.DeadlineExceeded. Cancellation remains cooperative; callbacks or
+	// collaborators that ignore context cannot be forcibly interrupted.
 	OperationTimeout time.Duration `json:"-" yaml:"-"`
 	// OnPrepared synchronously receives detached, credential-redacted details of
 	// the logical request after preparation and admission, before generation,
@@ -182,7 +185,8 @@ type RunRequest struct {
 
 // PreparedRun contains prepared prompt execution state returned by
 // [Engine.Prepare] or [PreparedExecution.Details]. It does not include resolved
-// API key values, model output, validation results, or internal target presence
+// API key values. RunRequest.OnPrepared also supplies this detached value.
+// It does not include model output, validation results, or internal target presence
 // metadata. PreparedRun has a stable JSON representation.
 //
 // All maps, slices, pointers, and schema values are caller-owned copies. JSON