diff --git a/.project-docs/30-worklog/tasks/20260831-diagnose-attachment-dns-7e41c9a2.md b/.project-docs/30-worklog/tasks/20260831-diagnose-attachment-dns-7e41c9a2.md
new file mode 100644
index 0000000..51b1a34
--- /dev/null
+++ b/.project-docs/30-worklog/tasks/20260831-diagnose-attachment-dns-7e41c9a2.md
@@ -0,0 +1,54 @@
+# Task: Diagnose attachment DNS download failure
+
+## Identity
+
+- Task ID: 20260831-diagnose-attachment-dns-7e41c9a2
+- Mode: Feature
+- Branch: main
+- Worktree: /Users/inmanx/Documents/lwltAPI
+- Base commit: 0da8b4f959032249b0e86f82db2aeff545fa7e82
+- Owner: codex
+- Status: Ready for integration
+
+## Scope
+
+- Inspect the user-supplied production control-plane log excerpt for the current internal AgentBus roster attachment failure.
+- Correlate the structured attachment milestones and stack trace with `control-plane/src/input-attachment.ts`.
+- Correct the pinned DNS `lookup` callback so it follows both Node single-address and `all: true` callback contracts.
+- Add focused regression coverage and run the full repository gates.
+
+## Intent And Constraints
+
+- Preserve accepted internal-network behavior: private, reserved, localhost, and internal DNS attachment targets remain allowed.
+- Preserve credential-free HTTPS, DNS resolution and pinning, redirect revalidation, timeout, byte limits, declared-size validation, optional SHA-256 verification, and privacy-safe diagnostics.
+- Do not log or persist attachment URLs, hostnames, IP addresses, file bytes, message text, or roster values.
+- Do not deploy, restart services, mutate Kubernetes, read secrets, access ERP, retry a live task, or send an external message.
+
+## Outcome
+
+- Confirmed from the supplied production log that the AgentBus frame was correlated correctly, one structured `.xls` attachment was accepted, metadata validation passed, and DNS resolution returned eight IPv4 addresses. The failure occurred only when the HTTPS connection consumed the selected pinned address.
+- Root cause is the custom `lookup` callback shape, not private-network rejection or DNS failure. Node invokes connection lookup with `options.all = true`; the old callback returned `(null, addressString, family)`, while that mode requires `(null, [{ address, family }])`. Node consequently raised `ERR_INVALID_IP_ADDRESS` before any HTTP response.
+- Reproduced the same failure locally with the bundled Node runtime: the request passed `{ all: true }`, the old scalar callback produced `ERR_INVALID_IP_ADDRESS`, and the stack matched the production failure boundary.
+- Added `createPinnedAttachmentLookup()`. It returns a single-element array for `all: true` and the scalar address/family pair otherwise, retaining a single previously validated address as the only connection candidate.
+- Replaced the unsafe `as never` callback cast with the typed lookup function and added regression coverage for both callback forms.
+- No internal-address blocking was restored or added. No deployment, restart, Kubernetes mutation, secret read, ERP access, live-task retry, or external message occurred.
+
+## Verification
+
+- Focused input-attachment tests: 8/8 passed, including the new Node lookup callback-shape regression.
+- `node --run check:repo`: 9/9 passed.
+- `node --run check`: passed.
+- `node --run test:control-plane`: 136/136 passed.
+- `node --run test:legacy`: 255/255 passed.
+- `node --run build`: passed.
+- `check_project_docs.py`: passed.
+- `git diff --check`: passed.
+
+## Follow-ups
+
+- The fix is not active on the server until a separately authorized image build/deployment/restart publishes the new revision.
+- After deployment, verify a real internal roster attachment reaches `agentbus.attachment_http_response` and `agentbus.attachment_download_completed`; `DEPLOYMENT_REVISION` should no longer be `unknown`.
+
+## Promotion Candidates
+
+- None. This fixes an implementation defect while preserving the already accepted `NETWORK-001` behavior and security boundaries.
diff --git a/control-plane/src/input-attachment.ts b/control-plane/src/input-attachment.ts
index 892eb2d..7750b1a 100644
--- a/control-plane/src/input-attachment.ts
+++ b/control-plane/src/input-attachment.ts
@@ -1,6 +1,6 @@
 import { lookup as dnsLookup } from 'node:dns/promises';
 import { request as httpsRequest } from 'node:https';
-import { isIP } from 'node:net';
+import { isIP, type LookupFunction } from 'node:net';
 import { basename } from 'node:path';
 import { sha256Bytes } from './crypto.js';
 import { diagnosticDurationMs } from './diagnostics.js';
@@ -207,6 +207,18 @@ export async function resolveAgentBusAttachmentAddresses(
   return addresses;
 }
 
+export function createPinnedAttachmentLookup(
+  address: { address: string; family: number }
+): LookupFunction {
+  return (_hostname, options, callback) => {
+    if (options.all) {
+      callback(null, [address]);
+      return;
+    }
+    callback(null, address.address, address.family);
+  };
+}
+
 async function downloadPinnedHttps(
   url: URL,
   address: { address: string; family: number },
@@ -217,9 +229,7 @@ async function downloadPinnedHttps(
       method: 'GET',
       headers: { Accept: 'application/vnd.ms-excel, application/vnd.openxmlformats-officedocument.spreadsheetml.sheet, application/octet-stream' },
       timeout: DOWNLOAD_TIMEOUT_MS,
-      lookup: ((_hostname: string, _options: unknown, callback: (error: NodeJS.ErrnoException | null, address: string, family: number) => void) => {
-        callback(null, address.address, address.family);
-      }) as never
+      lookup: createPinnedAttachmentLookup(address)
     }, (response) => {
       const statusCode = Number(response.statusCode || 0);
       const location = Array.isArray(response.headers.location) ? response.headers.location[0] : response.headers.location;
diff --git a/control-plane/test/input-attachment.test.ts b/control-plane/test/input-attachment.test.ts
index c7459f0..ca10533 100644
--- a/control-plane/test/input-attachment.test.ts
+++ b/control-plane/test/input-attachment.test.ts
@@ -4,6 +4,7 @@ import test from 'node:test';
 import { sha256Bytes } from '../src/crypto.js';
 import {
   InputAttachmentError,
+  createPinnedAttachmentLookup,
   decodeInlineInputAttachment,
   downloadAgentBusInputAttachment,
   parseAgentBusInputAttachment,
@@ -90,6 +91,35 @@ test('AgentBus attachment DNS accepts internal names and private literal address
   assert.ok(localhost.every((entry) => entry.family === 4 || entry.family === 6));
 });
 
+test('AgentBus attachment DNS pinning follows the Node lookup callback shape', async () => {
+  const address = { address: '10.0.0.8', family: 4 };
+  const lookup = createPinnedAttachmentLookup(address);
+  await new Promise<void>((resolve, reject) => {
+    lookup('internal.example', { all: true }, (error, addresses, family) => {
+      try {
+        assert.ifError(error);
+        assert.deepEqual(addresses, [address]);
+        assert.equal(family, undefined);
+        resolve();
+      } catch (assertionError) {
+        reject(assertionError);
+      }
+    });
+  });
+  await new Promise<void>((resolve, reject) => {
+    lookup('internal.example', { all: false }, (error, resolvedAddress, family) => {
+      try {
+        assert.ifError(error);
+        assert.equal(resolvedAddress, address.address);
+        assert.equal(family, address.family);
+        resolve();
+      } catch (assertionError) {
+        reject(assertionError);
+      }
+    });
+  });
+});
+
 test('AgentBus attachment diagnostics expose stages and codes without URL data', async () => {
   const events: Array<{ event: string; metadata: Record<string, unknown> }> = [];
   await assert.rejects(