diff --git a/docs/codebase/prompt-inbox-provenance.md b/docs/codebase/prompt-inbox-provenance.md
index a0dfda73c..47183c7a4 100644
--- a/docs/codebase/prompt-inbox-provenance.md
+++ b/docs/codebase/prompt-inbox-provenance.md
@@ -44,4 +44,4 @@ Each PR is at most **400 authored diff lines**, includes its own tests/docs with
 
 ## Limitations
 
-Pending retry UX and any cryptographic offline issuer still require design and tests; none may turn chunk/import history into authority. Session registration and its storage schema exist. SQLite records `local_creation_project` only on newly inserted CreateSession/StartSession rows. NULL means unknown/unverified for pre-migration, imported, rescued and remotely created sessions. A pulled upsert into a locally created session preserves its existing marker. Eligibility requires the current owner to match that stored creation owner exactly; identity repair preserves the nullable value. A store read returns current owner and local eligibility, not cloud authority. Cloud storage supports explicit immutable prompt pair claims against registered sessions, without deriving claims from chunks or prompt history. `ClaimPromptPair` assumes its caller has authenticated the actor and checked both project grants; it does not perform authorization. Authenticated registration and pair-claim routes exist; no verified delete admission or client handshake is implemented yet. The current cloud behavior does **not** enforce this RFC.
+Pending retry UX and any cryptographic offline issuer still require design and tests; none may turn chunk/import history into authority. Session registration and its storage schema exist. SQLite records `local_creation_project` only on newly inserted CreateSession/StartSession rows. Newly inserted keyed `AddPromptWithResult` rows also record their original session ID, inbox ID and prompt project; existing/replayed, idless, imported and pulled rows do not acquire this marker. The live-row read requires exact agreement with all three original values, including beta prompt ownership under an alpha session. This marker is local creation evidence, not cloud authority; it is not retained on deletion. NULL means unknown/unverified for pre-migration, imported, rescued and remotely created sessions. A pulled upsert into a locally created session preserves its existing marker. Eligibility requires the current owner to match that stored creation owner exactly; identity repair preserves the nullable value. A store read returns current owner and local eligibility, not cloud authority. Cloud storage supports explicit immutable prompt pair claims against registered sessions, without deriving claims from chunks or prompt history. `ClaimPromptPair` assumes its caller has authenticated the actor and checked both project grants; it does not perform authorization. Authenticated registration and pair-claim routes exist; no verified delete admission or client handshake is implemented yet. The current cloud behavior does **not** enforce this RFC.
diff --git a/internal/store/prompt_local_origin_test.go b/internal/store/prompt_local_origin_test.go
new file mode 100644
index 000000000..f3dc18cbe
--- /dev/null
+++ b/internal/store/prompt_local_origin_test.go
@@ -0,0 +1,166 @@
+package store
+
+import "testing"
+
+func TestLocalPromptCreationIdentity(t *testing.T) {
+	s := newTestStore(t)
+	if err := s.CreateSession("session", "alpha", "/work"); err != nil {
+		t.Fatal(err)
+	}
+	check := func(syncID, session, inbox, project string, eligible bool) {
+		t.Helper()
+		gotSession, gotInbox, gotProject, gotEligible, err := s.LocalPromptCreationIdentity(syncID)
+		if err != nil || gotSession != session || gotInbox != inbox || gotProject != project || gotEligible != eligible {
+			t.Fatalf("syncID %q: %q %q %q %v %v", syncID, gotSession, gotInbox, gotProject, gotEligible, err)
+		}
+	}
+	check("", "", "", "", false)
+	keyed := AddPromptParams{SessionID: "session", Project: "beta", SourceInboxID: "inbox", Content: "local"}
+	id, inserted, err := s.AddPromptWithResult(keyed)
+	if err != nil || !inserted {
+		t.Fatalf("insert: %v %v", inserted, err)
+	}
+	var localSyncID string
+	if err := s.DB().QueryRow(`SELECT sync_id FROM user_prompts WHERE id=?`, id).Scan(&localSyncID); err != nil {
+		t.Fatal(err)
+	}
+	check(localSyncID, "session", "inbox", "beta", true)
+	replay, inserted, err := s.AddPromptWithResult(keyed)
+	if err != nil || inserted || replay != id {
+		t.Fatalf("replay: %d %v %v", replay, inserted, err)
+	}
+	check(localSyncID, "session", "inbox", "beta", true)
+	if err := s.ApplyPulledMutation(DefaultSyncTargetKey, SyncMutation{Seq: 1, Entity: SyncEntityPrompt, EntityKey: "remote", Op: SyncOpUpsert, Payload: `{"sync_id":"remote","session_id":"session","source_inbox_id":"remote-key","project":"beta","content":"remote"}`, Source: SyncSourceRemote, Project: "beta"}); err != nil {
+		t.Fatal(err)
+	}
+	check("remote", "", "", "", false)
+	if err := s.ApplyPulledMutation(DefaultSyncTargetKey, SyncMutation{Seq: 2, Entity: SyncEntityPrompt, EntityKey: "remote", Op: SyncOpUpsert, Payload: `{"sync_id":"remote","session_id":"session","source_inbox_id":"remote-key","project":"beta","content":"changed"}`, Source: SyncSourceRemote, Project: "beta"}); err != nil {
+		t.Fatal(err)
+	}
+	check("remote", "", "", "", false)
+	if _, inserted, err := s.AddPromptWithResult(AddPromptParams{SessionID: "session", Project: "beta", SourceInboxID: "remote-key", Content: "collision"}); err != nil || inserted {
+		t.Fatalf("collision: %v %v", inserted, err)
+	}
+	check("remote", "", "", "", false)
+	if err := s.ApplyPulledMutation(DefaultSyncTargetKey, SyncMutation{Seq: 3, Entity: SyncEntityPrompt, EntityKey: "different", Op: SyncOpUpsert, Payload: `{"sync_id":"different","session_id":"session","source_inbox_id":"inbox","project":"beta","content":"collision"}`, Source: SyncSourceRemote, Project: "beta"}); err == nil {
+		t.Fatal("pulled collision accepted")
+	}
+	check(localSyncID, "session", "inbox", "beta", true)
+	backup, err := s.Export()
+	if err != nil {
+		t.Fatal(err)
+	}
+	imported := newTestStore(t)
+	if _, err := imported.Import(backup); err != nil {
+		t.Fatal(err)
+	}
+	session, inbox, project, eligible, err := imported.LocalPromptCreationIdentity(localSyncID)
+	if err != nil || session != "" || inbox != "" || project != "" || eligible {
+		t.Fatalf("import promoted identity: %q %q %q %v %v", session, inbox, project, eligible, err)
+	}
+	plain, inserted, err := s.AddPromptIfMissing(AddPromptParams{SessionID: "session", Project: "beta", Content: "plain"})
+	if err != nil || !inserted {
+		t.Fatalf("idless: %v %v", inserted, err)
+	}
+	var plainSyncID string
+	if err := s.DB().QueryRow(`SELECT sync_id FROM user_prompts WHERE id=?`, plain).Scan(&plainSyncID); err != nil {
+		t.Fatal(err)
+	}
+	check(plainSyncID, "", "", "", false)
+	idless, inserted, err := s.AddPromptWithResult(AddPromptParams{SessionID: "session", Project: "beta", Content: "another idless"})
+	if err != nil || !inserted {
+		t.Fatalf("idless AddPromptWithResult: %v %v", inserted, err)
+	}
+	var idlessSyncID string
+	if err := s.DB().QueryRow(`SELECT sync_id FROM user_prompts WHERE id=?`, idless).Scan(&idlessSyncID); err != nil {
+		t.Fatal(err)
+	}
+	check(idlessSyncID, "", "", "", false)
+	check("missing", "", "", "", false)
+	if _, err := s.DB().Exec(`UPDATE user_prompts SET project='gamma' WHERE id=?`, id); err != nil {
+		t.Fatal(err)
+	}
+	check(localSyncID, "", "", "", false)
+	if _, err := s.DB().Exec(`UPDATE user_prompts SET project='beta', source_inbox_id='other' WHERE id=?`, id); err != nil {
+		t.Fatal(err)
+	}
+	check(localSyncID, "", "", "", false)
+	if err := s.CreateSession("other", "alpha", "/work"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := s.DB().Exec(`UPDATE user_prompts SET source_inbox_id='inbox', session_id='other' WHERE id=?`, id); err != nil {
+		t.Fatal(err)
+	}
+	check(localSyncID, "", "", "", false)
+	deleteID, inserted, err := s.AddPromptWithResult(AddPromptParams{SessionID: "session", Project: "beta", SourceInboxID: "delete-inbox", Content: "delete"})
+	if err != nil || !inserted {
+		t.Fatalf("delete insert: %v %v", inserted, err)
+	}
+	var deleteSyncID string
+	if err := s.DB().QueryRow(`SELECT sync_id FROM user_prompts WHERE id=?`, deleteID).Scan(&deleteSyncID); err != nil {
+		t.Fatal(err)
+	}
+	check(deleteSyncID, "session", "delete-inbox", "beta", true)
+	if err := s.DeletePrompt(deleteID); err != nil {
+		t.Fatal(err)
+	}
+	check(deleteSyncID, "", "", "", false)
+}
+
+func TestLocalPromptCreationIdentityDuplicateSyncID(t *testing.T) {
+	s := newTestStore(t)
+	if err := s.CreateSession("session", "alpha", "/work"); err != nil {
+		t.Fatal(err)
+	}
+	id, _, err := s.AddPromptWithResult(AddPromptParams{SessionID: "session", Project: "beta", SourceInboxID: "key", Content: "first"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	var syncID string
+	if err := s.DB().QueryRow(`SELECT sync_id FROM user_prompts WHERE id=?`, id).Scan(&syncID); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := s.DB().Exec(`INSERT INTO user_prompts(sync_id,session_id,source_inbox_id,project,content) VALUES (?,'session','duplicate','beta','second')`, syncID); err != nil {
+		t.Fatal(err)
+	}
+	session, inbox, project, eligible, err := s.LocalPromptCreationIdentity(syncID)
+	if err != nil || session != "" || inbox != "" || project != "" || eligible {
+		t.Fatalf("duplicate promoted identity: %q %q %q %v %v", session, inbox, project, eligible, err)
+	}
+}
+
+func TestLocalPromptCreationIdentityMigration(t *testing.T) {
+	cfg := FallbackConfig(t.TempDir())
+	s, err := New(cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err = s.DB().Exec(`INSERT INTO sessions(id,project,directory) VALUES ('old','alpha','/work')`); err != nil {
+		t.Fatal(err)
+	}
+	if _, err = s.DB().Exec(`INSERT INTO user_prompts(sync_id,session_id,source_inbox_id,project,content) VALUES ('old-prompt','old','key','beta','old')`); err != nil {
+		t.Fatal(err)
+	}
+	if _, err = s.DB().Exec(`ALTER TABLE user_prompts DROP COLUMN local_creation_session_id`); err != nil {
+		t.Fatal(err)
+	}
+	if _, _, _, _, err = s.LocalPromptCreationIdentity("old-prompt"); err == nil {
+		t.Fatal("missing column should fail closed")
+	}
+	if err = s.Close(); err != nil {
+		t.Fatal(err)
+	}
+	s, err = New(cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		if err := s.Close(); err != nil {
+			t.Error(err)
+		}
+	}()
+	session, inbox, project, eligible, err := s.LocalPromptCreationIdentity("old-prompt")
+	if err != nil || session != "" || inbox != "" || project != "" || eligible {
+		t.Fatalf("migration: %q %q %q %v %v", session, inbox, project, eligible, err)
+	}
+}
diff --git a/internal/store/store.go b/internal/store/store.go
index b1aeaedf0..5d04f9ce5 100644
--- a/internal/store/store.go
+++ b/internal/store/store.go
@@ -1254,6 +1254,9 @@ func (s *Store) migrate() error {
 				id         INTEGER PRIMARY KEY AUTOINCREMENT,
 				sync_id    TEXT,
 				source_inbox_id TEXT,
+				local_creation_session_id TEXT,
+				local_creation_inbox_id TEXT,
+				local_creation_project TEXT,
 				session_id TEXT    NOT NULL,
 			content    TEXT    NOT NULL,
 			project    TEXT,
@@ -1410,6 +1413,11 @@ func (s *Store) migrate() error {
 	if err := s.addColumnIfNotExists("user_prompts", "source_inbox_id", "TEXT"); err != nil {
 		return err
 	}
+	for _, column := range []string{"local_creation_session_id", "local_creation_inbox_id", "local_creation_project"} {
+		if err := s.addColumnIfNotExists("user_prompts", column, "TEXT"); err != nil {
+			return err
+		}
+	}
 	if err := s.addColumnIfNotExists("prompt_tombstones", "source_inbox_id", "TEXT"); err != nil {
 		return err
 	}
@@ -3854,12 +3862,17 @@ func (s *Store) AddPromptWithResult(p AddPromptParams) (int64, bool, error) {
 			}
 		}
 		syncID := newSyncID("prompt")
-		query := `INSERT INTO user_prompts (sync_id, session_id, content, project, source_inbox_id) VALUES (?, ?, ?, ?, ?)`
+		query := `INSERT INTO user_prompts (sync_id, session_id, content, project, source_inbox_id, local_creation_session_id, local_creation_inbox_id, local_creation_project) VALUES (?, ?, ?, ?, ?, ?, ?, ?)`
 		if p.SourceInboxID != "" {
 			query += ` ON CONFLICT(session_id, source_inbox_id) WHERE source_inbox_id IS NOT NULL DO NOTHING`
 		}
+		var creationSession, creationProject any
+		if p.SourceInboxID != "" {
+			creationSession, creationProject = p.SessionID, nullableString(p.Project)
+		}
 		res, err := s.execHook(tx, query,
-			syncID, p.SessionID, content, nullableString(p.Project), nullableString(p.SourceInboxID))
+			syncID, p.SessionID, content, nullableString(p.Project), nullableString(p.SourceInboxID),
+			creationSession, nullableString(p.SourceInboxID), creationProject)
 		if err != nil {
 			return err
 		}
@@ -3899,6 +3912,38 @@ func (s *Store) AddPromptWithResult(p AddPromptParams) (int64, bool, error) {
 	return promptID, inserted, nil
 }
 
+// LocalPromptCreationIdentity returns a live locally inserted keyed identity by sync ID.
+// Unknown, ambiguous and mismatched identities fail closed; deleted rows have no fallback.
+func (s *Store) LocalPromptCreationIdentity(syncID string) (session, inbox, project string, eligible bool, err error) {
+	if syncID == "" {
+		return "", "", "", false, nil
+	}
+	rows, err := s.db.Query(`SELECT local_creation_session_id, local_creation_inbox_id, local_creation_project,
+		ifnull(session_id,''), ifnull(source_inbox_id,''), ifnull(project,'') FROM user_prompts WHERE sync_id=? LIMIT 2`, syncID)
+	if err != nil {
+		return "", "", "", false, err
+	}
+	defer func() { _ = rows.Close() }()
+	if !rows.Next() {
+		return "", "", "", false, rows.Err()
+	}
+	var originalSession, originalInbox, originalProject sql.NullString
+	if err := rows.Scan(&originalSession, &originalInbox, &originalProject, &session, &inbox, &project); err != nil {
+		return "", "", "", false, err
+	}
+	if rows.Next() {
+		return "", "", "", false, nil
+	}
+	if err := rows.Err(); err != nil {
+		return "", "", "", false, err
+	}
+	if originalSession.String == "" || originalInbox.String == "" || originalProject.String == "" ||
+		originalSession.String != session || originalInbox.String != inbox || originalProject.String != project {
+		return "", "", "", false, nil
+	}
+	return session, inbox, project, true, nil
+}
+
 func (s *Store) AddPromptIfMissing(p AddPromptParams) (int64, bool, error) {
 	p.Project, _ = NormalizeProject(p.Project)
 	content, _ := s.prepareStoredContent(p.Content)