diff --git a/backend/__tests__/service/firstTaskCreditOnLostClaim.test.js b/backend/__tests__/service/firstTaskCreditOnLostClaim.test.js
new file mode 100644
index 0000000000..4309e28a0c
--- /dev/null
+++ b/backend/__tests__/service/firstTaskCreditOnLostClaim.test.js
@@ -0,0 +1,193 @@
+/**
+ * TASK-002 credit when the addressed agent LOSES the claim — executed against
+ * real PostgreSQL + MongoDB (Tier 1).
+ *
+ * The two halves shipped separately and are unit-tested separately:
+ *  - #2273: a native turn passes `answeringMessageId` (the trigger's own
+ *    messageId) on every post it makes, whether or not it won the claim;
+ *  - #2274: `postMessage` hands it to `completeFirstTaskOnAnswer` and to the
+ *    attention writer, and `humansAnsweredBy` counts its author when the
+ *    message is in the same pod.
+ *
+ * Neither unit suite can show the join. On production the case is a race:
+ * Scout's wake and the addressed agent's mention are queued about 150 ms apart
+ * and either can claim first (2 of 5 measured first asks, 2026-10-16), so it
+ * cannot be produced on demand. Here Scout holds the claim as a FIXTURE: a
+ * row written before the turn, not an agent acting.
+ *
+ * Only the model is mocked. The turn, the post, the PG write, the answer
+ * rule, the starter-task update and the attention writer are the shipped code.
+ */
+
+/* eslint-disable import/extensions, import/no-unresolved -- backend TypeScript
+   modules are required by path, as in the other tier-1 suites. */
+
+jest.mock('axios', () => ({ __esModule: true, default: { post: jest.fn() } }));
+// Typing indicators and live updates need a socket server; nothing here reads them.
+jest.mock('../../config/socket', () => {
+  const room = { emit: () => undefined };
+  return { getIO: () => ({ to: () => room, in: () => room, emit: () => undefined }) };
+});
+
+const mongoose = require('mongoose');
+const fs = require('fs');
+const path = require('path');
+const axios = require('axios').default;
+
+const { setupMongoDb, closeMongoDb } = require('../utils/testUtils');
+const { pool } = require('../../config/db-pg');
+const User = require('../../models/User');
+const Pod = require('../../models/Pod');
+const Task = require('../../models/Task');
+const AttentionItem = require('../../models/AttentionItem');
+const { AgentInstallation } = require('../../models/AgentRegistry');
+const PGMessage = require('../../models/pg/Message');
+const MessageClaimService = require('../../services/messageClaimService');
+const AgentMessageService = require('../../services/agentMessageService');
+const { FIRST_TASK_SOURCE_REF } = require('../../services/starterTaskService');
+const { runAgent } = require('../../services/nativeRuntimeService');
+
+const RUN = process.env.INTEGRATION_TEST === 'true';
+const d = RUN ? describe : describe.skip;
+
+const AGENT = 'join-agent';
+
+const toolCall = (content) => ({
+  status: 200,
+  headers: {},
+  data: {
+    choices: [{
+      message: {
+        role: 'assistant',
+        content: null,
+        tool_calls: [{ id: 'c1', type: 'function', function: { name: 'commonly_post_message', arguments: JSON.stringify({ content }) } }],
+      },
+    }],
+    usage: { prompt_tokens: 20, completion_tokens: 10, total_tokens: 30 },
+  },
+});
+const done = {
+  status: 200,
+  headers: {},
+  data: { choices: [{ message: { role: 'assistant', content: 'NO_REPLY' } }], usage: { prompt_tokens: 5, completion_tokens: 1, total_tokens: 6 } },
+};
+
+// completeFirstTaskOnAnswer is fire-and-forget after the post returns.
+const settled = async (read, accept, ms = 4000) => {
+  const until = Date.now() + ms;
+  let value = await read();
+  while (!accept(value) && Date.now() < until) {
+    // eslint-disable-next-line no-await-in-loop
+    await new Promise((resolve) => { setTimeout(resolve, 100); });
+    // eslint-disable-next-line no-await-in-loop
+    value = await read();
+  }
+  return value;
+};
+
+d('TASK-002 credit when the addressed agent lost the claim (real PG + Mongo)', () => {
+  let owner;
+  let pod;
+  let installation;
+  let seq = 0;
+
+  beforeAll(async () => {
+    await setupMongoDb();
+    await pool.query(fs.readFileSync(path.join(__dirname, '../../config/schema.sql'), 'utf8'));
+    process.env.LITELLM_BASE_URL = 'http://litellm.test';
+    process.env.LITELLM_MASTER_KEY = 'test-key';
+  });
+
+  afterAll(async () => {
+    await pool.query('DELETE FROM message_claims').catch(() => undefined);
+    await pool.end();
+    await closeMongoDb();
+  });
+
+  beforeEach(async () => {
+    jest.clearAllMocks();
+    seq += 1;
+    owner = await User.create({
+      username: `owner${seq}x`, email: `owner${seq}x@example.test`, password: 'not-a-real-password-1', isBot: false,
+    });
+    pod = await Pod.create({
+      name: `Join ${seq}`, type: 'chat', createdBy: owner._id, members: [owner._id], 
+    });
+    await pool.query('INSERT INTO users (_id, username) VALUES ($1, $2) ON CONFLICT (_id) DO NOTHING', [String(owner._id), owner.username]);
+    await pool.query(
+      'INSERT INTO pods (id, name, type, created_by) VALUES ($1, $2, \'chat\', $3) ON CONFLICT (id) DO NOTHING',
+      [String(pod._id), pod.name, String(owner._id)],
+    );
+    installation = await AgentInstallation.create({
+      agentName: AGENT,
+      instanceId: 'default',
+      podId: pod._id,
+      version: '1.0.0',
+      installedBy: owner._id,
+      status: 'active',
+      displayName: 'Join Agent',
+      config: { runtime: { runtimeType: 'native' }, tools: ['commonly_post_message'], model: 'test/model' },
+    });
+    await Task.create({
+      podId: pod._id, taskNum: 2, taskId: 'TASK-002', title: 'Give your agent its first task', status: 'pending', sourceRef: FIRST_TASK_SOURCE_REF,
+    });
+  });
+
+  const ownerAsks = async () => PGMessage.create(String(pod._id), String(owner._id), `@${AGENT} what is this pod for?`, 'text');
+  const holdAsScout = async (messageId) => {
+    const held = await MessageClaimService.claim({
+      messageId: String(messageId), podId: String(pod._id), agentName: 'scout', instanceId: `u-scout-${seq}`,
+    });
+    expect(held.claimed).toBe(true);
+  };
+  const firstTask = () => Task.findOne({ podId: pod._id, sourceRef: FIRST_TASK_SOURCE_REF }).lean();
+  const ownerRows = () => AttentionItem.find({ recipientUserId: owner._id, kind: 'mention' }).lean();
+
+  test('beaten to the claim by Scout, the agent\'s answer completes TASK-002 and opens no needs-you row', async () => {
+    const ask = await ownerAsks();
+    await holdAsScout(ask.id);
+    // The answer names the owner, so the attention writer has a row to open
+    // unless the answer rule says this post answers them.
+    axios.post.mockResolvedValueOnce(toolCall(`@${owner.username} This pod is for planning the launch.`)).mockResolvedValueOnce(done);
+
+    await runAgent(installation.toObject(), {
+      type: 'chat.mention',
+      eventId: new mongoose.Types.ObjectId().toString(),
+      payload: { messageId: String(ask.id), userId: String(owner._id), content: `@${AGENT} what is this pod for?` },
+    });
+
+    const posted = await pool.query('SELECT id FROM messages WHERE pod_id = $1 AND content LIKE $2', [String(pod._id), '%planning the launch%']);
+    expect(posted.rows).toHaveLength(1);
+    // Still held by Scout: the agent ran unclaimed, which is the case under test.
+    const claim = await pool.query('SELECT claimed_by FROM message_claims WHERE message_id = $1', [String(ask.id)]);
+    expect(claim.rows[0]?.claimed_by).toBe('scout');
+
+    const task = await settled(firstTask, (t) => t?.status === 'done');
+    expect(task.status).toBe('done');
+    expect(task.updates.at(-1).text).toMatch(/answered your first request/);
+    expect(await ownerRows()).toHaveLength(0);
+  });
+
+  test('CONTROL: the same unclaimed answer without the answering id leaves TASK-002 open and opens the row', async () => {
+    const ask = await ownerAsks();
+    await holdAsScout(ask.id);
+
+    // What the turn sent before #2273: no claim held, no reply edge, no id.
+    await AgentMessageService.postMessage({
+      agentName: AGENT,
+      instanceId: 'default',
+      podId: String(pod._id),
+      content: `@${owner.username} This pod is for planning the launch.`,
+      messageType: 'text',
+      displayName: 'Join Agent',
+      installationConfig: installation.config,
+      metadata: { source: 'native-runtime' },
+    });
+
+    const rows = await settled(ownerRows, (r) => r.length > 0);
+    expect(rows).toHaveLength(1);
+    // Give the fire-and-forget completion the same time it gets above.
+    const task = await settled(firstTask, (t) => t?.status === 'done', 2000);
+    expect(task.status).toBe('pending');
+  });
+});
diff --git a/backend/services/messageClaimService.ts b/backend/services/messageClaimService.ts
index 96e01fecc8..8e7c09413b 100644
--- a/backend/services/messageClaimService.ts
+++ b/backend/services/messageClaimService.ts
@@ -20,6 +20,12 @@
  * The kernel NEVER refuses an unclaimed post (D3). This service only answers
  * "who holds the lease?" — enforcement is the driver's job, and only for
  * drivers we ship. "Forgot to claim" must not become "agent is silent".
+ *
+ * The table is not a history. A completed claim's row is deleted on release;
+ * a declined or refused one, and a lapsed lease, about an hour later
+ * (HANDOFF_HISTORY_RETENTION_SECONDS, pruned on claim traffic). Who claimed a
+ * message cannot be read back from here after the fact; the agent events and
+ * runtime logs are the record.
  */
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports