diff --git a/packages/workflow-agent-docx-diff/__tests__/agent.test.ts b/packages/workflow-agent-docx-diff/__tests__/agent.test.ts
new file mode 100644
index 0000000..c201f83
--- /dev/null
+++ b/packages/workflow-agent-docx-diff/__tests__/agent.test.ts
@@ -0,0 +1,22 @@
+import { describe, expect, test } from "bun:test";
+import { packageDescriptor } from "../src/package-descriptor.js";
+import { createDocxDiffAgent } from "../src/agent.js";
+
+describe("createDocxDiffAgent", () => {
+  test("returns an AdapterFn (function)", () => {
+    const agent = createDocxDiffAgent({ command: null });
+    expect(typeof agent).toBe("function");
+  });
+
+  test("AdapterFn returns a RoleFn (function)", () => {
+    const agent = createDocxDiffAgent({ command: null });
+    const roleFn = agent("", expect.anything() as never);
+    expect(typeof roleFn).toBe("function");
+  });
+});
+
+describe("packageDescriptor", () => {
+  test("has correct name", () => {
+    expect(packageDescriptor.name).toBe("@uncaged/workflow-agent-docx-diff");
+  });
+});
diff --git a/packages/workflow-agent-docx-diff/__tests__/runner.test.ts b/packages/workflow-agent-docx-diff/__tests__/runner.test.ts
new file mode 100644
index 0000000..3d7d2e0
--- /dev/null
+++ b/packages/workflow-agent-docx-diff/__tests__/runner.test.ts
@@ -0,0 +1,113 @@
+import { mkdirSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+import { describe, expect, mock, test } from "bun:test";
+import { ok, err } from "@uncaged/workflow-util";
+import type { SpawnCliConfig } from "@uncaged/workflow-util-agent";
+import { runDocxDiff } from "../src/runner.js";
+
+type MockSpawnResult = Awaited<ReturnType<typeof import("@uncaged/workflow-util-agent").spawnCli>>;
+
+function makeSpawn(result: MockSpawnResult) {
+  return mock(async (_cmd: string, _args: string[], _opts: SpawnCliConfig) => result);
+}
+
+function tempDir(): string {
+  const dir = join(tmpdir(), `diff-test-${Date.now()}`);
+  mkdirSync(dir, { recursive: true });
+  return dir;
+}
+
+describe("runDocxDiff", () => {
+  test("exit 0: success, returns DifferMeta JSON", async () => {
+    const dir = tempDir();
+    const sourceDocx = join(dir, "original.docx");
+    const modifiedDocx = join(dir, "modified.docx");
+    const diffDocx = join(dir, "diff.docx");
+    writeFileSync(sourceDocx, "");
+    writeFileSync(modifiedDocx, "");
+
+    const spawnFn = makeSpawn(ok("") as MockSpawnResult);
+    // simulate docx-diff creating the diff file
+    writeFileSync(diffDocx, "");
+
+    const raw = await runDocxDiff(
+      { command: "docx-diff" },
+      sourceDocx,
+      modifiedDocx,
+      diffDocx,
+      spawnFn,
+    );
+    const meta = JSON.parse(raw);
+    expect(meta.sourceDocx).toBe(sourceDocx);
+    expect(meta.modifiedDocx).toBe(modifiedDocx);
+    expect(meta.diffDocx).toBe(diffDocx);
+
+    expect(spawnFn.mock.calls[0][1]).toEqual([
+      sourceDocx,
+      modifiedDocx,
+      "--output",
+      "docx",
+      "--out-file",
+      diffDocx,
+    ]);
+  });
+
+  test("exit 1 (changes found): treated as success", async () => {
+    const dir = tempDir();
+    const sourceDocx = join(dir, "s.docx");
+    const modifiedDocx = join(dir, "m.docx");
+    const diffDocx = join(dir, "diff.docx");
+    writeFileSync(sourceDocx, "");
+    writeFileSync(modifiedDocx, "");
+    writeFileSync(diffDocx, "");
+
+    const spawnFn = makeSpawn(
+      err({ kind: "non_zero_exit", exitCode: 1, stdout: "", stderr: "" }) as MockSpawnResult,
+    );
+
+    await expect(
+      runDocxDiff({ command: "docx-diff" }, sourceDocx, modifiedDocx, diffDocx, spawnFn),
+    ).resolves.toBeDefined();
+  });
+
+  test("exit 2: throws error", async () => {
+    const dir = tempDir();
+    const spawnFn = makeSpawn(
+      err({ kind: "non_zero_exit", exitCode: 2, stdout: "", stderr: "fatal error" }) as MockSpawnResult,
+    );
+
+    await expect(
+      runDocxDiff({ command: null }, "s.docx", "m.docx", "diff.docx", spawnFn),
+    ).rejects.toThrow("docx-diff failed");
+  });
+
+  test("timeout: throws error", async () => {
+    const spawnFn = makeSpawn(err({ kind: "timeout" }) as MockSpawnResult);
+
+    await expect(
+      runDocxDiff({ command: null }, "s.docx", "m.docx", "diff.docx", spawnFn),
+    ).rejects.toThrow("timed out");
+  });
+
+  test("throws when diff file not created", async () => {
+    const dir = tempDir();
+    const spawnFn = makeSpawn(ok("") as MockSpawnResult);
+    // do NOT create diffDocx
+
+    await expect(
+      runDocxDiff({ command: null }, "s.docx", "m.docx", join(dir, "missing.docx"), spawnFn),
+    ).rejects.toThrow("diff file not found");
+  });
+
+  test("uses PATH docx-diff when command is null", async () => {
+    const dir = tempDir();
+    const diffDocx = join(dir, "diff.docx");
+    writeFileSync(diffDocx, "");
+    const spawnFn = makeSpawn(ok("") as MockSpawnResult);
+
+    await runDocxDiff({ command: null }, "s.docx", "m.docx", diffDocx, spawnFn);
+
+    expect(spawnFn.mock.calls[0][0]).toBe("docx-diff");
+  });
+});
diff --git a/packages/workflow-agent-docx-diff/package.json b/packages/workflow-agent-docx-diff/package.json
index 311b9b3..1cbbf33 100644
--- a/packages/workflow-agent-docx-diff/package.json
+++ b/packages/workflow-agent-docx-diff/package.json
@@ -17,7 +17,11 @@
   "dependencies": {
     "@uncaged/workflow-runtime": "workspace:^",
     "@uncaged/workflow-util-agent": "workspace:^",
-    "@uncaged/workflow-template-document": "workspace:^"
+    "@uncaged/workflow-template-document": "workspace:^",
+    "zod": "^4.0.0"
+  },
+  "devDependencies": {
+    "@uncaged/workflow-util": "workspace:^"
   },
   "publishConfig": {
     "access": "public"
diff --git a/packages/workflow-agent-docx-diff/src/agent.ts b/packages/workflow-agent-docx-diff/src/agent.ts
new file mode 100644
index 0000000..4c9ea87
--- /dev/null
+++ b/packages/workflow-agent-docx-diff/src/agent.ts
@@ -0,0 +1,29 @@
+import * as z from "zod/v4";
+import { dirname, join } from "node:path";
+import type { AdapterFn, RoleResult, ThreadContext, WorkflowRuntime } from "@uncaged/workflow-runtime";
+import type { WriterMeta } from "@uncaged/workflow-template-document";
+import { runDocxDiff } from "./runner.js";
+import type { DocxDiffAgentConfig } from "./types.js";
+
+export function createDocxDiffAgent(config: DocxDiffAgentConfig): AdapterFn {
+  return <T>(_prompt: string, schema: z.ZodType<T>) =>
+    async (ctx: ThreadContext, _runtime: WorkflowRuntime): Promise<RoleResult<T>> => {
+      const writerStep = ctx.steps.find((s) => s.role === "writer");
+      if (writerStep === undefined) throw new Error("differ: no writer step found");
+
+      const writerMeta = writerStep.meta as WriterMeta;
+      if (writerMeta.mode !== "edit")
+        throw new Error("differ: writer did not run in edit mode");
+
+      const diffDocx = join(dirname(writerMeta.outputDocx), "diff.docx");
+      const raw = await runDocxDiff(
+        config,
+        writerMeta.sourceDocx,
+        writerMeta.outputDocx,
+        diffDocx,
+      );
+
+      const meta = schema.parse(JSON.parse(raw)) as T;
+      return { meta, childThread: null };
+    };
+}
diff --git a/packages/workflow-agent-docx-diff/src/index.ts b/packages/workflow-agent-docx-diff/src/index.ts
index cb0ff5c..1dcc0a3 100644
--- a/packages/workflow-agent-docx-diff/src/index.ts
+++ b/packages/workflow-agent-docx-diff/src/index.ts
@@ -1 +1,3 @@
-export {};
+export { createDocxDiffAgent } from "./agent.js";
+export { packageDescriptor } from "./package-descriptor.js";
+export type { DocxDiffAgentConfig } from "./types.js";
diff --git a/packages/workflow-agent-docx-diff/src/package-descriptor.ts b/packages/workflow-agent-docx-diff/src/package-descriptor.ts
new file mode 100644
index 0000000..60c9925
--- /dev/null
+++ b/packages/workflow-agent-docx-diff/src/package-descriptor.ts
@@ -0,0 +1,17 @@
+import type { PackageDescriptor } from "@uncaged/workflow-runtime";
+
+export const packageDescriptor: PackageDescriptor = {
+  name: "@uncaged/workflow-agent-docx-diff",
+  version: "0.1.0",
+  capabilities: ["docx-diff-cli", "docx-diff-report"],
+  configSchema: {
+    type: "object",
+    properties: {
+      command: {
+        anyOf: [{ type: "string" }, { type: "null" }],
+        description: "Path to docx-diff CLI binary; null uses PATH.",
+      },
+    },
+    additionalProperties: false,
+  },
+};
diff --git a/packages/workflow-agent-docx-diff/src/runner.ts b/packages/workflow-agent-docx-diff/src/runner.ts
new file mode 100644
index 0000000..f29f5e4
--- /dev/null
+++ b/packages/workflow-agent-docx-diff/src/runner.ts
@@ -0,0 +1,47 @@
+import { stat } from "node:fs/promises";
+import { spawnCli } from "@uncaged/workflow-util-agent";
+import type { SpawnCliError } from "@uncaged/workflow-util-agent";
+import type { DocxDiffAgentConfig } from "./types.js";
+
+type SpawnCliFn = typeof spawnCli;
+
+function throwSpawnError(e: SpawnCliError): never {
+  if (e.kind === "non_zero_exit")
+    throw new Error(`docx-diff failed (exit ${e.exitCode}): ${e.stderr}`);
+  if (e.kind === "timeout")
+    throw new Error("docx-diff: timed out");
+  throw new Error(`docx-diff: spawn failed: ${e.message}`);
+}
+
+export async function runDocxDiff(
+  config: DocxDiffAgentConfig,
+  sourceDocx: string,
+  modifiedDocx: string,
+  diffDocx: string,
+  spawnCliFn: SpawnCliFn = spawnCli,
+): Promise<string> {
+  const command = config.command ?? "docx-diff";
+  const result = await spawnCliFn(
+    command,
+    [sourceDocx, modifiedDocx, "--output", "docx", "--out-file", diffDocx],
+    { cwd: null, timeoutMs: null },
+  );
+
+  if (!result.ok) {
+    const e = result.error;
+    // exit 1 = changes found (normal for docx-diff)
+    if (e.kind === "non_zero_exit" && e.exitCode === 1) {
+      // fall through to file check
+    } else {
+      throwSpawnError(e);
+    }
+  }
+
+  try {
+    await stat(diffDocx);
+  } catch {
+    throw new Error(`docx-diff: diff file not found: ${diffDocx}`);
+  }
+
+  return JSON.stringify({ sourceDocx, modifiedDocx, diffDocx });
+}
diff --git a/packages/workflow-agent-docx-diff/src/types.ts b/packages/workflow-agent-docx-diff/src/types.ts
new file mode 100644
index 0000000..4bcc174
--- /dev/null
+++ b/packages/workflow-agent-docx-diff/src/types.ts
@@ -0,0 +1,3 @@
+export type DocxDiffAgentConfig = {
+  command: string | null;
+};