diff --git a/scripts/mosaic-task.mjs b/scripts/mosaic-task.mjs
index e59c1a2c..8eb96ce9 100755
--- a/scripts/mosaic-task.mjs
+++ b/scripts/mosaic-task.mjs
@@ -234,7 +234,7 @@ function writeOnce(file, content) {
   }
 }
 
-function runTask(taskFile) {
+function runTask(taskFile, options = {}) {
   const resolved = JSON.parse(
     spawnSync(process.execPath, [path.join(PROJECT_ROOT, "scripts", "mosaic-config.mjs"), "validate"], {
       cwd: PROJECT_ROOT,
@@ -345,6 +345,7 @@ function runTask(taskFile) {
     request: task.prompt,
     response,
     expectedExact: expected,
+    ...(options.retriedFrom ? { retriedFrom: options.retriedFrom } : {}),
     workspace: task.workspace,
     tools: task.tools,
     session: task.session,
@@ -455,6 +456,24 @@ function retryRun(runId) {
     fail(4, `run task snapshot unreadable: ${runId}`);
   }
 
+  // Relative mission paths in a snapshot resolve against the ORIGINAL task
+  // location, which no longer exists here — rewrite them to the run's own
+  // recorded mission.json so retries stay faithful.
+  let snapshotDoc;
+  try {
+    snapshotDoc = JSON.parse(snapshot);
+  } catch {
+    fail(4, `run task snapshot is not valid JSON: ${runId}`);
+  }
+  if (snapshotDoc.mission && !path.isAbsolute(snapshotDoc.mission)) {
+    const recordedMission = path.join(dir, "mission.json");
+    if (!fs.existsSync(recordedMission)) {
+      fail(4, `cannot retry ${runId}: relative mission path but no mission.json snapshot in run dir`);
+    }
+    snapshotDoc.mission = recordedMission;
+    snapshot = `${JSON.stringify(snapshotDoc, null, 2)}\n`;
+  }
+
   // A retry is a brand-new run: replay the recorded task snapshot through
   // the ordinary run path; existing run records stay untouched.
   const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "mosaic-retry-"));
@@ -467,7 +486,7 @@ function retryRun(runId) {
       // Best-effort cleanup only.
     }
   });
-  runTask(tempTaskFile);
+  runTask(tempTaskFile, { retriedFrom: runId });
 }
 
 const operation = process.argv[2];
diff --git a/scripts/test-task.sh b/scripts/test-task.sh
index b4333391..d50a0302 100755
--- a/scripts/test-task.sh
+++ b/scripts/test-task.sh
@@ -142,6 +142,21 @@ EOF
         && grep -q 'Seam directive A.' "$SANDBOX/data/system-prompt.md" \
         && check "mission section injected into generated prompt" 0 \
         || check "mission section injected into generated prompt" 1
+
+    # retry lineage + relative mission path resolution
+    expect_exit "retry of mission run succeeds" 0 -- \
+        env MOSAIC_CONFIG="$SANDBOX/mock-adapters.json" MOSAIC_MOCK_RESPONSE=MOCKED \
+        node scripts/mosaic-task.mjs retry "$(ls -dt "$SANDBOX/data/runs"/r-* | head -1 | xargs basename)"
+    RT="$(ls -dt "$SANDBOX/data/runs"/r-* | head -1 | xargs basename)"
+    ORIG="$(ls -dt "$SANDBOX/data/runs"/r-* | sed -n 2p | xargs basename)"
+    node -e 'const r=JSON.parse(require("fs").readFileSync(process.argv[1],"utf8"));process.exit(r.retriedFrom===process.argv[2]?0:1)' \
+        "$SANDBOX/data/runs/$RT/result.json" "$ORIG" \
+        && check "retriedFrom lineage recorded" 0 || check "retriedFrom lineage recorded" 1
+    grep -q 'MISSION (runtime)' "$SANDBOX/data/system-prompt.md" \
+        && check "mission section present after retry (relative path resolved)" 0 \
+        || check "mission section present after retry (relative path resolved)" 1
+    expect_exit "retry of missing run exits 4" 4 -- \
+        env MOSAIC_CONFIG="$SANDBOX/mock-adapters.json" node scripts/mosaic-task.mjs retry r-missing
 else
     echo "skip adapter seam cases (docker daemon unavailable)"
 fi