diff --git a/src/chrome/src/agent/agent.js b/src/chrome/src/agent/agent.js
index 9b5497f2c..eb93bb037 100644
--- a/src/chrome/src/agent/agent.js
+++ b/src/chrome/src/agent/agent.js
@@ -10716,6 +10716,11 @@ Rules: no prose intro, no conclusion, no "this screenshot shows...", no layout d
         mode,
         attachments: Array.isArray(runOptions?.traceAttachments) ? runOptions.traceAttachments : [],
         conversationId: this.conversationIds.get(tabId) || null,
+        // Derived-run lineage: when this run is launched from an active run on
+        // the same tab (cloud run, workflow replay), the launching call site
+        // passes the origin ids so the trace can attribute the derived run.
+        parentRunId: runOptions?.parentRunId || null,
+        parentSessionId: runOptions?.parentSessionId || null,
         force: runOptions?.cloudRun === true,
       });
     } catch {
@@ -19594,10 +19599,25 @@ Rules: no prose intro, no conclusion, no "this screenshot shows...", no layout d
     await trace.endRun(runId, { status, finalContent });
   }
 
+  async _getSavedWorkflowParentTrace(runId) {
+    return trace.getRun(runId);
+  }
+
+  async _startSavedWorkflowTraceRun(meta) {
+    return trace.startRun(meta);
+  }
+
   async replaySavedWorkflow(tabId, workflow, parameters = {}, onUpdate = () => {}, runOptions = {}) {
     if (!workflow?.id || !Array.isArray(workflow.steps) || !workflow.steps.length) {
       throw new Error('Saved workflow is missing or invalid.');
     }
+    // Capture the compiling trace before the run claim. Active trace ids are
+    // cleared when a run ends, but a normalized workflow retains its durable
+    // source run id and can therefore establish real replay provenance.
+    const replayParentRunId = runOptions?.parentRunId || workflow.source?.runId || null;
+    let replayParentSessionId = replayParentRunId
+      ? runOptions?.parentSessionId || null
+      : null;
     await this._claimRunEntry(tabId, 'workflow', runOptions);
     let completionRunToken = '';
     let previousForegroundCapture = false;
@@ -19626,8 +19646,16 @@ Rules: no prose intro, no conclusion, no "this screenshot shows...", no layout d
       capturePolicyConfigured = true;
       startUrl = await this._currentUrl(tabId);
       const conversationId = await this.ensureConversationId(tabId, 'act');
-      traceRunId = await trace.startRun({
+      if (replayParentRunId && !replayParentSessionId) {
+        try {
+          const parentTrace = await this._getSavedWorkflowParentTrace(replayParentRunId);
+          replayParentSessionId = parentTrace?.conversationId || null;
+        } catch { /* missing historical traces leave session lineage unset */ }
+      }
+      traceRunId = await this._startSavedWorkflowTraceRun({
         conversationId,
+        parentRunId: replayParentRunId,
+        parentSessionId: replayParentSessionId,
         userMessage: `Run saved workflow: ${workflow.name}`,
         tabUrl: startUrl,
         mode: 'act',
diff --git a/src/chrome/src/cloud-runs.js b/src/chrome/src/cloud-runs.js
index f8e55e938..43874d753 100644
--- a/src/chrome/src/cloud-runs.js
+++ b/src/chrome/src/cloud-runs.js
@@ -1096,6 +1096,18 @@ export function createCloudRunController({
       let recordingId = null;
       const strictSecretMode = agent.strictSecretMode === true;
       try {
+        // A continuation starts only after its parent has finished, so the
+        // agent's active-run map cannot identify the parent here. The cloud
+        // run record keeps the actual trace id; resolve its session from that
+        // trace instead of attaching the tab's potentially unrelated session.
+        const parentTraceRunId = parentRun?.traceRunId || null;
+        let parentTraceSessionId = null;
+        if (parentTraceRunId && typeof workflowTrace?.getRun === 'function') {
+          try {
+            const parentTrace = await workflowTrace.getRun(parentTraceRunId);
+            parentTraceSessionId = parentTrace?.conversationId || null;
+          } catch { /* lineage lookup is best-effort and must not fail a run */ }
+        }
         if (run.capture === 'video') {
           try {
             if (!startRecording || !stopRecording) throw new Error('Cloud run video capture is unavailable.');
@@ -1169,6 +1181,8 @@ export function createCloudRunController({
               run.traceRunId = traceRunId;
               schedulePersist();
             },
+            parentRunId: parentTraceRunId,
+            parentSessionId: parentTraceSessionId,
           });
         }
         run.pendingInput = null;
diff --git a/src/firefox/src/agent/agent.js b/src/firefox/src/agent/agent.js
index ddf80b31c..0983f4147 100644
--- a/src/firefox/src/agent/agent.js
+++ b/src/firefox/src/agent/agent.js
@@ -8577,6 +8577,11 @@ Rules: no prose intro, no conclusion, no "this screenshot shows...", no layout d
         mode,
         attachments: Array.isArray(runOptions?.traceAttachments) ? runOptions.traceAttachments : [],
         conversationId: this.conversationIds.get(tabId) || null,
+        // Derived-run lineage: when this run is launched from an active run on
+        // the same tab (cloud run, workflow replay), the launching call site
+        // passes the origin ids so the trace can attribute the derived run.
+        parentRunId: runOptions?.parentRunId || null,
+        parentSessionId: runOptions?.parentSessionId || null,
         force: runOptions?.cloudRun === true,
       });
     } catch {
@@ -16758,10 +16763,25 @@ Rules: no prose intro, no conclusion, no "this screenshot shows...", no layout d
     await trace.endRun(runId, { status, finalContent });
   }
 
+  async _getSavedWorkflowParentTrace(runId) {
+    return trace.getRun(runId);
+  }
+
+  async _startSavedWorkflowTraceRun(meta) {
+    return trace.startRun(meta);
+  }
+
   async replaySavedWorkflow(tabId, workflow, parameters = {}, onUpdate = () => {}, runOptions = {}) {
     if (!workflow?.id || !Array.isArray(workflow.steps) || !workflow.steps.length) {
       throw new Error('Saved workflow is missing or invalid.');
     }
+    // Capture the compiling trace before the run claim. Active trace ids are
+    // cleared when a run ends, but a normalized workflow retains its durable
+    // source run id and can therefore establish real replay provenance.
+    const replayParentRunId = runOptions?.parentRunId || workflow.source?.runId || null;
+    let replayParentSessionId = replayParentRunId
+      ? runOptions?.parentSessionId || null
+      : null;
     await this._claimRunEntry(tabId, 'workflow', runOptions);
     let completionRunToken = '';
     let startUrl = '';
@@ -16787,8 +16807,16 @@ Rules: no prose intro, no conclusion, no "this screenshot shows...", no layout d
       completionRunToken = this._beginCompletionInvariant(tabId);
       startUrl = await this._currentUrl(tabId);
       const conversationId = await this.ensureConversationId(tabId, 'act');
-      traceRunId = await trace.startRun({
+      if (replayParentRunId && !replayParentSessionId) {
+        try {
+          const parentTrace = await this._getSavedWorkflowParentTrace(replayParentRunId);
+          replayParentSessionId = parentTrace?.conversationId || null;
+        } catch { /* missing historical traces leave session lineage unset */ }
+      }
+      traceRunId = await this._startSavedWorkflowTraceRun({
         conversationId,
+        parentRunId: replayParentRunId,
+        parentSessionId: replayParentSessionId,
         userMessage: `Run saved workflow: ${workflow.name}`,
         tabUrl: startUrl,
         mode: 'act',
diff --git a/test/run.js b/test/run.js
index 0d067a449..aeaa7e352 100644
--- a/test/run.js
+++ b/test/run.js
@@ -17931,6 +17931,155 @@ test('cloud run controller preserves a boolean false root output schema', async
     'persistence marked the false root schema as unstructured');
 });
 
+test('cloud run controller threads lineage from the completed parent cloud trace', async () => {
+  const session = {};
+  const tab = { id: 23, url: 'https://example.test/', active: true, windowId: 5 };
+  const receivedRunOptions = [];
+  let nextRun = 0;
+  const controller = createCloudRunController({
+    chromeApi: {
+      tabs: {
+        query: async () => [tab],
+        get: async () => tab,
+        update: async () => tab,
+      },
+      windows: { update: async () => ({}) },
+      storage: {
+        session: {
+          get: async key => ({ [key]: session[key] || [] }),
+          set: async value => Object.assign(session, value),
+        },
+      },
+      runtime: { sendMessage: async () => ({}) },
+    },
+    agent: {
+      isRunning: () => false,
+      abort: () => {},
+      setApiMutationsAllowed: () => {},
+      setTemporaryApiMutationsAllowed: () => {},
+      // A persistent conversation id without a trace parent must never become
+      // an orphaned parent-session link on a root cloud run.
+      conversationIds: { get: () => 'conv_unrelated' },
+      processMessage: async (_tabId, task, _onUpdate, _mode, _attachments, runOptions) => {
+        receivedRunOptions.push(runOptions);
+        runOptions.onTraceStarted?.(task === 'Parent task' ? 'trace_parent_1' : 'trace_child_1');
+        return 'cloud result';
+      },
+    },
+    ensureOffscreen: async () => {},
+    workflowTrace: {
+      async getRun(runId) {
+        assert.equal(runId, 'trace_parent_1');
+        return { runId, conversationId: 'conv_parent_9' };
+      },
+    },
+    makeRunId: () => (++nextRun === 1 ? 'cloud_parent_1' : 'cloud_child_1'),
+  });
+
+  const parent = await controller.startRun({ task: 'Parent task', apiMutationsAllowed: true });
+  await new Promise(resolve => setTimeout(resolve, 0));
+  await controller.startRun({ task: 'Child task', parentRunId: parent.runId });
+  await new Promise(resolve => setTimeout(resolve, 0));
+
+  assert.equal(receivedRunOptions[0].parentRunId, null, 'root cloud run received an orphaned parent run');
+  assert.equal(receivedRunOptions[0].parentSessionId, null, 'root cloud run received an orphaned parent session');
+  assert.equal(receivedRunOptions[1].parentRunId, 'trace_parent_1', 'continuation did not receive its parent trace');
+  assert.equal(receivedRunOptions[1].parentSessionId, 'conv_parent_9', 'continuation did not receive its parent trace session');
+});
+
+test('cloud run controller tolerates an agent without lineage maps', async () => {
+  const session = {};
+  const tab = { id: 24, url: 'https://example.test/', active: true, windowId: 5 };
+  let receivedRunOptions;
+  const controller = createCloudRunController({
+    chromeApi: {
+      tabs: {
+        query: async () => [tab],
+        get: async () => tab,
+        update: async () => tab,
+      },
+      windows: { update: async () => ({}) },
+      storage: {
+        session: {
+          get: async key => ({ [key]: session[key] || [] }),
+          set: async value => Object.assign(session, value),
+        },
+      },
+      runtime: { sendMessage: async () => ({}) },
+    },
+    agent: {
+      isRunning: () => false,
+      abort: () => {},
+      setApiMutationsAllowed: () => {},
+      setTemporaryApiMutationsAllowed: () => {},
+      processMessage: async (_tabId, _task, _onUpdate, _mode, _attachments, runOptions) => {
+        receivedRunOptions = runOptions;
+        return 'cloud result';
+      },
+    },
+    ensureOffscreen: async () => {},
+    makeRunId: () => 'run_lineage_root',
+  });
+
+  await controller.startRun({ task: 'Do the thing.', apiMutationsAllowed: true });
+  assert.equal(receivedRunOptions.parentRunId, null, 'missing parent run must fall back to null');
+  assert.equal(receivedRunOptions.parentSessionId, null, 'missing parent session must fall back to null');
+});
+
+test('trace lineage: _startTraceRun and replay plumb parent ids in both builds', () => {
+  for (const browser of ['chrome', 'firefox']) {
+    const agentSource = fs.readFileSync(path.join(ROOT, `src/${browser}/src/agent/agent.js`), 'utf8');
+    assert.match(agentSource, /parentRunId: runOptions\?\.parentRunId \|\| null,/, `${browser}: _startTraceRun does not forward parentRunId`);
+    assert.match(agentSource, /parentSessionId: runOptions\?\.parentSessionId \|\| null,/, `${browser}: _startTraceRun does not forward parentSessionId`);
+    assert.match(agentSource, /const replayParentRunId = runOptions\?\.parentRunId \|\| workflow\.source\?\.runId \|\| null;[\s\S]*?await this\._claimRunEntry\(tabId, 'workflow', runOptions\);/, `${browser}: replay does not capture source lineage before claiming the tab`);
+    assert.match(agentSource, /this\._getSavedWorkflowParentTrace\(replayParentRunId\)/, `${browser}: replay does not resolve its source trace session`);
+    assert.match(agentSource, /parentRunId: replayParentRunId,[\s\S]*?parentSessionId: replayParentSessionId,/, `${browser}: replay does not pass captured lineage to tracing`);
+  }
+  const chromeCloudRuns = fs.readFileSync(path.join(ROOT, 'src/chrome/src/cloud-runs.js'), 'utf8');
+  assert.match(chromeCloudRuns, /const parentTraceRunId = parentRun\?\.traceRunId \|\| null;/, 'cloud-runs does not use the completed parent trace');
+  assert.match(chromeCloudRuns, /workflowTrace\.getRun\(parentTraceRunId\)/, 'cloud-runs does not resolve the parent trace session');
+  assert.match(chromeCloudRuns, /parentRunId: parentTraceRunId,[\s\S]*?parentSessionId: parentTraceSessionId,/, 'cloud-runs does not thread resolved parent lineage');
+  assert.ok(!fs.existsSync(path.join(ROOT, 'src/firefox/src/cloud-runs.js')), 'Firefox has no cloud-runs module — lineage threading is Chrome-only by platform boundary');
+});
+
+test('saved workflow replay captures its source lineage before claiming the tab', async () => {
+  for (const [browser, AgentClass] of [['chrome', AgentCh], ['firefox', AgentFx]]) {
+    const tabId = browser === 'chrome' ? 17853 : 17854;
+    const workflow = {
+      id: `workflow_lineage_${browser}`,
+      name: 'Replay lineage',
+      source: { runId: `trace_source_${browser}` },
+      start: { origin: 'https://example.test', pathFamily: '/expected' },
+      steps: [{ id: 'step_1', tool: 'navigate', args: { url: 'https://example.test/next' } }],
+    };
+    const agent = new AgentClass({ getActive: () => ({ model: 'test-model' }) });
+    let traceMeta = null;
+    agent._claimRunEntry = async () => {
+      // If replay reads workflow.source after claiming, this destroys lineage.
+      workflow.source.runId = '';
+    };
+    agent._hydrate = async () => {};
+    agent._persist = () => {};
+    agent._currentUrl = async () => 'https://other.test/';
+    agent.ensureConversationId = async () => `conv_child_${browser}`;
+    agent._getSavedWorkflowParentTrace = async runId => ({
+      runId,
+      conversationId: `conv_parent_${browser}`,
+    });
+    agent._startSavedWorkflowTraceRun = async meta => {
+      traceMeta = meta;
+      return `trace_replay_${browser}`;
+    };
+    agent._endSavedWorkflowTraceRun = async () => {};
+
+    const replay = await agent.replaySavedWorkflow(tabId, workflow);
+
+    assert.equal(replay.status, 'fallback', `${browser}: replay fixture did not stop after trace start`);
+    assert.equal(traceMeta.parentRunId, `trace_source_${browser}`, `${browser}: replay lost the compiling trace id`);
+    assert.equal(traceMeta.parentSessionId, `conv_parent_${browser}`, `${browser}: replay used the child conversation as its parent session`);
+  }
+});
+
 test('cloud run controller rejects duplicate caller-supplied run IDs', async () => {
   const session = {};
   const controller = createCloudRunController({