diff --git a/src/artifacts.rs b/src/artifacts.rs
index d4266acb..d9223588 100644
--- a/src/artifacts.rs
+++ b/src/artifacts.rs
@@ -887,6 +887,48 @@ impl ArtifactRunWriter {
         self.run.path()
     }
 
+    /// Reads one manifested artifact while sibling invocations may still own
+    /// scratch directories. The caller must retain exclusive access to this
+    /// writer throughout the read; no manifest update or append can interleave.
+    /// Run-wide checkpoint/resume/finalization boundaries still use their full
+    /// tree audits and require every scratch and poisoned append to be resolved.
+    pub(crate) fn read_authenticated(&self, relative: &Path, max_bytes: usize) -> Result<Vec<u8>> {
+        self.run_lock.verify(&self.run)?;
+        let result = (|| -> Result<Vec<u8>> {
+            let relative = validate_artifact_relative_path(relative)?;
+            if self
+                .outstanding_scratches
+                .keys()
+                .any(|scratch| artifact_path_starts_with(&relative, scratch))
+            {
+                bail!("artifact read path overlaps an outstanding scratch directory");
+            }
+            if self.poisoned_appends.contains(&relative) {
+                bail!("artifact read path is poisoned by an unrecovered prior append");
+            }
+            let record = self
+                .files
+                .get(&relative)
+                .context("artifact read path is not registered in the writer manifest")?;
+            let max_bytes = u64::try_from(max_bytes).context("artifact read limit overflow")?;
+            if record.bytes > max_bytes {
+                bail!("artifact file exceeds its configured {max_bytes} byte limit");
+            }
+
+            // Preserve the selected path's privacy and directory/lock identity
+            // checks without auditing unrelated, actively written scratch trees.
+            verify_writer_evidence(&self.writer_evidence, &self.run_root, &self.run)?;
+            let before = verify_private_artifact_read_path(&self.run, &relative)?;
+            let contents = read_and_verify_record_with_limit(&self.run, record, max_bytes)?;
+            if verify_private_artifact_read_path(&self.run, &relative)? != before {
+                bail!("artifact file identity changed during authenticated read");
+            }
+            verify_writer_evidence(&self.writer_evidence, &self.run_root, &self.run)?;
+            Ok(contents)
+        })();
+        finish_with_artifact_lock_verification(result, self.run_lock.verify(&self.run))
+    }
+
     /// Reserves one owner-private, child-writable scratch directory directly
     /// beneath this run. Only a canonical single-component name is accepted so
     /// cleanup can remain handle-relative and identity-bound. A launcher must
diff --git a/src/artifacts/part2.rs b/src/artifacts/part2.rs
index a1ddce96..759cb9b4 100644
--- a/src/artifacts/part2.rs
+++ b/src/artifacts/part2.rs
@@ -180,10 +180,37 @@ fn verify_manifest_contents<'a>(
 }
 
 fn read_and_verify_record(run: &SafeRoot, record: &ArtifactFileRecord) -> Result<Vec<u8>> {
+    read_and_verify_record_with_limit(run, record, MAX_ARTIFACT_FILE_BYTES)
+}
+
+fn verify_private_artifact_read_path(run: &SafeRoot, relative: &Path) -> Result<FileIdentity> {
+    ensure_private_directory(run.path())?;
+    let mut directory = run.path().to_path_buf();
+    if let Some(parent) = relative.parent() {
+        for component in parent.components() {
+            directory.push(component);
+            ensure_private_directory(&directory)?;
+            ensure_same_device(
+                &fs::symlink_metadata(&directory)?,
+                run.identity().device,
+                &directory,
+            )?;
+        }
+    }
+    let path = run.path().join(relative);
+    let identity = ensure_private_regular_file(&path)?;
+    ensure_same_device(&fs::symlink_metadata(&path)?, run.identity().device, &path)?;
+    Ok(identity)
+}
+
+fn read_and_verify_record_with_limit(
+    run: &SafeRoot,
+    record: &ArtifactFileRecord,
+    max_bytes: u64,
+) -> Result<Vec<u8>> {
     let (_parent, _file_name) = artifact_parent_and_name(run, &record.path, false)?;
     ensure_private_regular_file(&run.path().join(&record.path))?;
-    let contents =
-        BoundedRegularReader::read_relative(run.path(), &record.path, MAX_ARTIFACT_FILE_BYTES)?;
+    let contents = BoundedRegularReader::read_relative(run.path(), &record.path, max_bytes)?;
     if u64::try_from(contents.len()).unwrap_or(u64::MAX) != record.bytes
         || sha256_hex(&contents) != record.sha256
     {
diff --git a/src/artifacts/tests.rs b/src/artifacts/tests.rs
index 3df8da93..b4bf6bf9 100644
--- a/src/artifacts/tests.rs
+++ b/src/artifacts/tests.rs
@@ -11,6 +11,101 @@ fn sha256_matches_standard_vector() {
     );
 }
 
+#[test]
+fn authenticated_file_read_refuses_its_own_poisoned_append_without_requiring_run_quiescence() {
+    let (_temp, repo) = committed_repo();
+    let mut writer = ArtifactRunWriter::reserve(
+        &repo,
+        RunArtifactFamily::Supervise,
+        RunId::new("authenticated-read-poison").unwrap(),
+        "supervise",
+    )
+    .unwrap();
+    let transcript = Path::new("logs/child-c.jsonl");
+    let sibling = Path::new("logs/child-a.jsonl");
+    for path in [transcript, sibling] {
+        writer
+            .write_bytes(
+                path,
+                b"completed\n",
+                ArtifactFileDisposition::PrivateEvidence,
+            )
+            .unwrap();
+    }
+    // Even if disk bytes happen to match the old manifest, an unrecovered
+    // append must not be treated as durable, authenticated evidence.
+    writer.poisoned_appends.insert(transcript.to_path_buf());
+    let error = writer.read_authenticated(transcript, 1024).unwrap_err();
+    assert!(error.to_string().contains("poisoned"));
+    assert!(writer.resume_binding().is_err());
+
+    writer.poisoned_appends.remove(transcript);
+    writer.poisoned_appends.insert(sibling.to_path_buf());
+    assert_eq!(
+        writer.read_authenticated(transcript, 1024).unwrap(),
+        b"completed\n"
+    );
+    assert!(writer.resume_binding().is_err());
+    let run = writer.run_dir().to_path_buf();
+    let error = writer.finalize(transcript, false).unwrap_err();
+    assert!(error.to_string().contains("poisoned append"));
+    assert!(!run.join(FINALIZATION_MARKER).exists());
+}
+
+#[cfg(unix)]
+#[test]
+fn authenticated_file_read_preserves_private_path_and_writer_lock_custody() {
+    use std::os::unix::fs::symlink;
+
+    let (_temp, repo) = committed_repo();
+    let mut writer = ArtifactRunWriter::reserve(
+        &repo,
+        RunArtifactFamily::Supervise,
+        RunId::new("authenticated-read-custody").unwrap(),
+        "supervise",
+    )
+    .unwrap();
+    let relative = Path::new("logs/child-c.jsonl");
+    writer
+        .write_bytes(
+            relative,
+            b"completed\n",
+            ArtifactFileDisposition::PrivateEvidence,
+        )
+        .unwrap();
+    let path = writer.run_dir().join(relative);
+    let parent = path.parent().unwrap();
+    fs::set_permissions(parent, fs::Permissions::from_mode(0o755)).unwrap();
+    assert!(writer
+        .read_authenticated(relative, 1024)
+        .unwrap_err()
+        .to_string()
+        .contains("owner-private"));
+    fs::set_permissions(parent, fs::Permissions::from_mode(0o700)).unwrap();
+    fs::set_permissions(&path, fs::Permissions::from_mode(0o644)).unwrap();
+    assert!(writer
+        .read_authenticated(relative, 1024)
+        .unwrap_err()
+        .to_string()
+        .contains("owner-private"));
+    fs::set_permissions(&path, fs::Permissions::from_mode(0o600)).unwrap();
+    let saved = parent.join("saved.jsonl");
+    fs::rename(&path, &saved).unwrap();
+    symlink(&saved, &path).unwrap();
+    assert!(writer.read_authenticated(relative, 1024).is_err());
+    fs::remove_file(&path).unwrap();
+    fs::rename(saved, &path).unwrap();
+    assert_eq!(
+        writer.read_authenticated(relative, 1024).unwrap(),
+        b"completed\n"
+    );
+
+    let lock_path = writer.run_dir().join(RUN_LOCK_FILE);
+    fs::rename(&lock_path, writer.run_dir().join("saved.lock")).unwrap();
+    fs::write(lock_path, b"replacement").unwrap();
+    assert!(writer.read_authenticated(relative, 1024).is_err());
+}
+
 #[test]
 fn supervisor_invocation_scratch_names_require_the_full_canonical_grammar() {
     let valid = [
diff --git a/src/supervise/assignment_execution.rs b/src/supervise/assignment_execution.rs
index decaaa2d..a017ab25 100644
--- a/src/supervise/assignment_execution.rs
+++ b/src/supervise/assignment_execution.rs
@@ -269,25 +269,13 @@ pub(super) fn read_authenticated_review_transcript(
     {
         bail!("review transcript artifact path is not canonical relative form");
     }
-    let before = writer
-        .resume_binding()
-        .context("failed to authenticate retained transcript artifact manifest before read")?;
-    let transcript_path = writer.run_dir().join(transcript_relative);
     // Authenticate and decode the complete retained evidence under the supervisor-report cap.
     // Only the later review-lens request is excerpted to its smaller, independent request limit.
-    let bytes = read_bounded_regular_file_nofollow(&transcript_path, MAX_SUPERVISOR_REPORT_BYTES)
-        .with_context(|| {
-        format!(
-            "failed to read retained child transcript {}",
-            transcript_path.display()
-        )
-    })?;
-    let after = writer
-        .resume_binding()
-        .context("failed to authenticate retained transcript artifact manifest after read")?;
-    if before != after {
-        bail!("retained transcript artifact manifest changed while it was read");
-    }
+    // The shared writer remains locked by the caller. Authenticate the exact bytes
+    // before allowing review to read them, independently of sibling scratch state.
+    let bytes = writer
+        .read_authenticated(transcript_relative, MAX_SUPERVISOR_REPORT_BYTES)
+        .context("failed to authenticate retained transcript artifact manifest before read")?;
     String::from_utf8(bytes).context("child transcript evidence is not valid UTF-8")
 }
 
diff --git a/src/supervise/tests/plan_runtime.rs b/src/supervise/tests/plan_runtime.rs
index d1325627..e07ff4e2 100644
--- a/src/supervise/tests/plan_runtime.rs
+++ b/src/supervise/tests/plan_runtime.rs
@@ -5239,6 +5239,32 @@ fn stacked_review_lenses_execute_every_configured_boundary_and_aggregate() {
     assert!(report.review_lens_usage.iter().all(|usage| {
         usage.observation == RoleUsageObservation::ProcessObserved && usage.usage.is_some()
     }));
+    let lens_usage = report
+        .review_lens_usage
+        .iter()
+        .map(|row| (row.lens_id.as_str(), row.usage))
+        .collect::<BTreeMap<_, _>>();
+    assert_eq!(
+        lens_usage,
+        BTreeMap::from([
+            (
+                "diff-security",
+                Some(Usage {
+                    input_tokens: 100,
+                    output_tokens: 20,
+                    total_tokens: 120,
+                }),
+            ),
+            (
+                "report-consistency",
+                Some(Usage {
+                    input_tokens: 200,
+                    output_tokens: 40,
+                    total_tokens: 240,
+                }),
+            ),
+        ])
+    );
     assert_eq!(
         report.review_lens_total_usage,
         Some(Usage {
diff --git a/src/supervise/tests/run_artifacts.rs b/src/supervise/tests/run_artifacts.rs
index 19d6564b..3b8c3317 100644
--- a/src/supervise/tests/run_artifacts.rs
+++ b/src/supervise/tests/run_artifacts.rs
@@ -5142,6 +5142,58 @@ fn retained_review_transcript_refuses_input_above_supervisor_report_limit() {
     )));
 }
 
+#[test]
+fn retained_review_transcript_authenticates_while_sibling_invocation_scratch_is_open() {
+    let (_temp, repo_path) = injected_repository();
+    let mut writer = ArtifactRunWriter::reserve(
+        &repo_path,
+        RunArtifactFamily::Supervise,
+        RunId::new("review-transcript-live-sibling").unwrap(),
+        "supervise-test",
+    )
+    .expect("reserve shared artifact writer");
+    let transcript_relative = Path::new("logs/child-c.jsonl");
+    let transcript = "completed child-c transcript\n";
+    writer
+        .write_bytes(
+            transcript_relative,
+            transcript.as_bytes(),
+            ArtifactFileDisposition::PrivateEvidence,
+        )
+        .expect("retain child-c transcript");
+    let mut journal = None;
+    let mut autonomy_kpis = AutonomyKpiCollector::default();
+    let artifacts = Mutex::new(SharedSupervisorArtifacts {
+        writer: &mut writer,
+        journal: &mut journal,
+        autonomy_kpis: &mut autonomy_kpis,
+        checkpoint: None,
+    });
+    let sibling_scratch = with_supervisor_artifacts(&artifacts, |writer, _| {
+        writer.create_supervisor_invocation_scratch_dir("capture-assignment-0000-attempt-01")
+    })
+    .expect("hold child-a invocation scratch open");
+    fs::write(sibling_scratch.path().join("stdout.jsonl"), b"in flight")
+        .expect("sibling is still producing evidence");
+    let authenticated = with_supervisor_artifacts(&artifacts, |writer, _| {
+        assert!(
+            writer.resume_binding().is_err(),
+            "checkpoint must still refuse live scratch"
+        );
+        read_authenticated_review_transcript(writer, transcript_relative)
+    });
+    with_supervisor_artifacts(&artifacts, |writer, _| {
+        writer.discard_scratch(&sibling_scratch)?;
+        writer.resume_binding()?;
+        Ok(())
+    })
+    .expect("quiescent writer becomes resumable");
+    assert_eq!(
+        authenticated.expect("parent review authenticates child-c independently"),
+        transcript
+    );
+}
+
 #[test]
 fn retained_review_transcript_manifest_authentication_refuses_tampering() {
     let (_temp, repo_path) = injected_repository();
@@ -5168,14 +5220,35 @@ fn retained_review_transcript_manifest_authentication_refuses_tampering() {
         transcript
     );
 
+    for tampered in [b"truncated".to_vec(), vec![b'f'; transcript.len()]] {
+        fs::write(writer.run_dir().join(transcript_relative), tampered)
+            .expect("tamper transcript fixture");
+        let error = read_authenticated_review_transcript(&mut writer, transcript_relative)
+            .expect_err("length or hash mismatch must be refused before review reads it");
+        assert!(error
+            .to_string()
+            .contains("failed to authenticate retained transcript artifact manifest before read"));
+        assert!(format!("{error:#}").contains("digest/length does not match its manifest"));
+    }
+
+    let unregistered = Path::new("logs/forged.jsonl");
+    fs::write(writer.run_dir().join(unregistered), b"forged transcript")
+        .expect("write unregistered transcript");
+    let error = read_authenticated_review_transcript(&mut writer, unregistered)
+        .expect_err("unregistered transcript must be refused before read");
+    assert!(error.to_string().contains("before read"));
+    assert!(format!("{error:#}").contains("not registered"));
+
+    let scratch = writer.create_scratch_dir("still-writing").unwrap();
     fs::write(
-        writer.run_dir().join(transcript_relative),
-        b"tampered transcript",
+        scratch.path().join("stdout.jsonl"),
+        b"unfinished transcript",
     )
-    .expect("tamper transcript fixture");
-    let error = read_authenticated_review_transcript(&mut writer, transcript_relative)
-        .expect_err("tampered transcript must be refused");
-    assert!(error
-        .to_string()
-        .contains("failed to authenticate retained transcript artifact manifest before read"));
+    .unwrap();
+    let error =
+        read_authenticated_review_transcript(&mut writer, Path::new("still-writing/stdout.jsonl"))
+            .expect_err("live scratch transcript must be refused before read");
+    assert!(error.to_string().contains("before read"));
+    assert!(format!("{error:#}").contains("outstanding scratch"));
+    writer.discard_scratch(&scratch).unwrap();
 }
diff --git a/src/supervise/tests/scheduler.rs b/src/supervise/tests/scheduler.rs
index a40d8ea1..db8e6f5f 100644
--- a/src/supervise/tests/scheduler.rs
+++ b/src/supervise/tests/scheduler.rs
@@ -901,7 +901,9 @@ fn semantic_block_claims_follow_actual_dispatch_order_with_overlap_scan_ahead()
     skip_without_containment!();
     #[derive(Default)]
     struct BlockState {
+        child_a_started: bool,
         child_c_started: bool,
+        child_c_parent_review_started: bool,
     }
 
     let (temp, repo_path) = injected_repository();
@@ -927,7 +929,9 @@ fn semantic_block_claims_follow_actual_dispatch_order_with_overlap_scan_ahead()
     let runner = {
         let assignments = assignments.clone();
         let state = Arc::clone(&state);
-        move |command: &ExternalAgentCommand| {
+        move |command: &ExternalAgentCommand,
+              cancellation: &ProcessCancellation,
+              _review_runtime: Option<ExternalPreActionReviewRuntime<'_>>| {
             let id = injected_command_assignment_id(command);
             if let Some(assignment) = assignments
                 .iter()
@@ -939,6 +943,16 @@ fn semantic_block_claims_follow_actual_dispatch_order_with_overlap_scan_ahead()
                     &command.output_last_message,
                     &injected_auditor_report(assignment, &child),
                 );
+                if assignment.id == "child-c" {
+                    let (lock, condvar) = &*state;
+                    let mut block = lock.lock().unwrap_or_else(|poisoned| poisoned.into_inner());
+                    assert!(
+                        block.child_a_started,
+                        "sibling invocation scratch must be live"
+                    );
+                    block.child_c_parent_review_started = true;
+                    condvar.notify_all();
+                }
                 return injected_verified_run(command);
             }
             let (lock, condvar) = &*state;
@@ -946,12 +960,37 @@ fn semantic_block_claims_follow_actual_dispatch_order_with_overlap_scan_ahead()
             if id == "child-c" {
                 block.child_c_started = true;
                 condvar.notify_all();
+                // C may reach its runner before A's thread is scheduled. Do
+                // not let it complete until A owns live invocation scratches.
+                block = wait_for_fixture_state(
+                    condvar,
+                    block,
+                    |block| block.child_a_started,
+                    "semantic_block_claims_follow_actual_dispatch_order_with_overlap_scan_ahead",
+                    "semantic-block-dispatch-order",
+                    "child-a holds invocation scratch",
+                    Duration::from_secs(120),
+                );
             } else if id == "child-a" {
-                while !block.child_c_started {
-                    block = condvar
-                        .wait(block)
+                block.child_a_started = true;
+                condvar.notify_all();
+                // Keep A's invocation scratch live until C has authenticated its
+                // completed transcript and entered parent review. Cancellation
+                // also releases A if authentication fails, so the old behavior
+                // produces a failed report rather than a deadlocked fixture.
+                let deadline = Instant::now() + Duration::from_secs(120);
+                while !block.child_c_parent_review_started && !cancellation.is_cancelled() {
+                    if Instant::now() >= deadline {
+                        if !block.child_c_started {
+                            panic!("child-c runner did not start");
+                        }
+                        panic!("child-c parent review did not start");
+                    }
+                    (block, _) = condvar
+                        .wait_timeout(block, Duration::from_millis(25))
                         .unwrap_or_else(|poisoned| poisoned.into_inner());
                 }
+                assert!(block.child_c_started || cancellation.is_cancelled());
             }
             drop(block);
             let assignment = assignments
@@ -967,7 +1006,7 @@ fn semantic_block_claims_follow_actual_dispatch_order_with_overlap_scan_ahead()
         #[cfg(target_os = "linux")]
         let _selected_fixture = selected_concurrent_injected_fixture(&plan, &options, &temp)
             .expect("hold explicit selected concurrent fixture");
-        run_supervisor_plan_with_concurrent_runner(
+        run_supervisor_plan_with_concurrent_cancellable_runner(
             plan,
             SupervisorConsultantPlan::default(),
             options,
@@ -977,6 +1016,7 @@ fn semantic_block_claims_follow_actual_dispatch_order_with_overlap_scan_ahead()
     }
     .expect("run deterministic semantic Block scheduling");
     assert!(report.success, "unexpected failed report: {report:#?}");
+    assert!(state.0.lock().unwrap().child_c_parent_review_started);
     assert_eq!(
         report
             .released_semantic_intents