diff --git a/workflows/__tests__/differ-adapter.test.ts b/workflows/__tests__/differ-adapter.test.ts
new file mode 100644
index 0000000..3ab1209
--- /dev/null
+++ b/workflows/__tests__/differ-adapter.test.ts
@@ -0,0 +1,150 @@
+import { mkdirSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+import { START } from "@uncaged/workflow-runtime";
+import { describe, expect, mock, test } from "bun:test";
+import { err, ok } from "@uncaged/workflow-util";
+import type { SpawnCliConfig } from "@uncaged/workflow-util-agent";
+import { differMetaSchema } from "@local/template-document-editor";
+import { createDifferAdapter } from "../adapters/differ-adapter.js";
+import type { ThreadContext } from "@uncaged/workflow-runtime";
+
+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(), `differ-test-${Date.now()}`);
+  mkdirSync(dir, { recursive: true });
+  return dir;
+}
+
+function makeCtx(officeMode: "generate" | "edit" | null): ThreadContext {
+  const steps =
+    officeMode === null
+      ? []
+      : [
+          {
+            role: "office",
+            meta:
+              officeMode === "edit"
+                ? { mode: "edit", outputDocx: "/tmp/modified.docx", sourceDocx: "/tmp/original.docx" }
+                : { mode: "generate", outputDocx: "/tmp/output.docx", sourceDocx: null },
+            contentHash: "",
+            refs: [],
+            timestamp: 0,
+          },
+        ];
+  return {
+    threadId: "t1",
+    depth: 0,
+    bundleHash: "",
+    start: { role: START, content: "", meta: {}, timestamp: 0, parentState: null },
+    steps,
+  } as unknown as ThreadContext;
+}
+
+async function runAdapter(
+  spawnFn: ReturnType<typeof makeSpawn>,
+  ctx: ThreadContext,
+  reportExists = true,
+) {
+  const dir = tempDir();
+  const outputDocx = join(dir, "modified.docx");
+  const sourceDocx = join(dir, "original.docx");
+  writeFileSync(outputDocx, "");
+  writeFileSync(sourceDocx, "");
+
+  const editCtx: ThreadContext = {
+    ...ctx,
+    steps: [
+      {
+        role: "office",
+        meta: { mode: "edit", outputDocx, sourceDocx },
+        contentHash: "",
+        refs: [],
+        timestamp: 0,
+      },
+    ],
+  } as unknown as ThreadContext;
+
+  if (reportExists) {
+    writeFileSync(join(dir, "diff_report.html"), "<html/>");
+  }
+
+  const adapter = createDifferAdapter({ command: "docx-diff", timeout: null }, spawnFn);
+  const roleFn = adapter("", differMetaSchema);
+  return roleFn(editCtx, {} as never);
+}
+
+describe("createDifferAdapter", () => {
+  test("returns DifferMeta on exit 0 (no changes)", async () => {
+    const spawn = makeSpawn(ok("") as MockSpawnResult);
+    const result = await runAdapter(spawn, makeCtx("edit"));
+    expect(result.meta.diffReport).toMatch(/diff_report\.html$/);
+    expect(result.childThread).toBeNull();
+  });
+
+  test("returns DifferMeta on exit 1 (has changes)", async () => {
+    const spawn = makeSpawn(
+      err({ kind: "non_zero_exit", exitCode: 1, stdout: "", stderr: "" }) as MockSpawnResult,
+    );
+    const result = await runAdapter(spawn, makeCtx("edit"));
+    expect(result.meta.diffReport).toMatch(/diff_report\.html$/);
+  });
+
+  test("throws on exit 2 (docx-diff error)", async () => {
+    const spawn = makeSpawn(
+      err({ kind: "non_zero_exit", exitCode: 2, stdout: "", stderr: "parse error" }) as MockSpawnResult,
+    );
+    await expect(runAdapter(spawn, makeCtx("edit"))).rejects.toThrow("docx-diff failed (exit 2)");
+  });
+
+  test("throws on timeout", async () => {
+    const spawn = makeSpawn(err({ kind: "timeout" }) as MockSpawnResult);
+    await expect(runAdapter(spawn, makeCtx("edit"))).rejects.toThrow("timed out");
+  });
+
+  test("throws on spawn_failed", async () => {
+    const spawn = makeSpawn(
+      err({ kind: "spawn_failed", message: "binary not found" }) as MockSpawnResult,
+    );
+    await expect(runAdapter(spawn, makeCtx("edit"))).rejects.toThrow("spawn failed");
+  });
+
+  test("throws when office step is missing from ctx.steps", async () => {
+    const spawn = makeSpawn(ok("") as MockSpawnResult);
+    const adapter = createDifferAdapter({ command: "docx-diff", timeout: null }, spawn);
+    const roleFn = adapter("", differMetaSchema);
+    const emptyCtx = makeCtx(null);
+    await expect(roleFn(emptyCtx, {} as never)).rejects.toThrow("office step not found");
+  });
+
+  test("throws when report file is not created by docx-diff", async () => {
+    const spawn = makeSpawn(ok("") as MockSpawnResult);
+    await expect(runAdapter(spawn, makeCtx("edit"), false)).rejects.toThrow("report file not found");
+  });
+
+  test("uses 'docx-diff' when command is null", async () => {
+    const spawn = makeSpawn(ok("") as MockSpawnResult);
+    const dir = tmpdir();
+    const outputDocx = join(dir, `mod-${Date.now()}.docx`);
+    const sourceDocx = join(dir, `src-${Date.now()}.docx`);
+    writeFileSync(outputDocx, "");
+    writeFileSync(sourceDocx, "");
+    writeFileSync(join(dir, "diff_report.html"), "<html/>");
+    const ctx: ThreadContext = {
+      threadId: "t2",
+      depth: 0,
+      bundleHash: "",
+      start: { role: START, content: "", meta: {}, timestamp: 0, parentState: null },
+      steps: [{ role: "office", meta: { mode: "edit", outputDocx, sourceDocx }, contentHash: "", refs: [], timestamp: 0 }],
+    } as unknown as ThreadContext;
+    const adapter = createDifferAdapter({ command: null, timeout: null }, spawn);
+    const roleFn = adapter("", differMetaSchema);
+    await roleFn(ctx, {} as never);
+    expect(spawn.mock.calls[0][0]).toBe("docx-diff");
+  });
+});
diff --git a/workflows/adapters/differ-adapter.ts b/workflows/adapters/differ-adapter.ts
new file mode 100644
index 0000000..aae8695
--- /dev/null
+++ b/workflows/adapters/differ-adapter.ts
@@ -0,0 +1,63 @@
+import { stat } from "node:fs/promises";
+import { dirname, join } from "node:path";
+import { spawnCli } from "@uncaged/workflow-util-agent";
+import type { AdapterFn, RoleResult, ThreadContext, WorkflowRuntime } from "@uncaged/workflow-runtime";
+import * as z from "zod/v4";
+
+export type DifferAdapterConfig = {
+  command: string | null;
+  timeout: number | null;
+};
+
+type SpawnCliFn = typeof spawnCli;
+
+export function createDifferAdapter(
+  config: DifferAdapterConfig,
+  spawnCliFn: SpawnCliFn = spawnCli,
+): AdapterFn {
+  const command = config.command ?? "docx-diff";
+  return <T>(_systemPrompt: string, schema: z.ZodType<T>) =>
+    async (ctx: ThreadContext, _runtime: WorkflowRuntime): Promise<RoleResult<T>> => {
+      const officeStep = ctx.steps.find((s) => s.role === "office");
+      if (officeStep === undefined) {
+        throw new Error("differ: office step not found in ctx.steps (invariant violation)");
+      }
+
+      const officeMeta = officeStep.meta as { mode: string; outputDocx: string; sourceDocx: string | null };
+      if (officeMeta.mode !== "edit" || officeMeta.sourceDocx === null) {
+        throw new Error("differ: office step is not in edit mode");
+      }
+
+      const { outputDocx, sourceDocx } = officeMeta;
+      const reportPath = join(dirname(outputDocx), "diff_report.html");
+
+      const result = await spawnCliFn(
+        command,
+        [sourceDocx, outputDocx, "-o", "html", "--out-file", reportPath],
+        { cwd: null, timeoutMs: config.timeout },
+      );
+
+      if (!result.ok) {
+        const e = result.error;
+        if (e.kind === "non_zero_exit" && e.exitCode === 1) {
+          // exit 1 means "documents differ" — the normal success case for docx-diff
+        } else if (e.kind === "non_zero_exit") {
+          throw new Error(`differ: docx-diff failed (exit ${e.exitCode}): ${e.stderr}`);
+        } else if (e.kind === "timeout") {
+          throw new Error("differ: timed out");
+        } else {
+          throw new Error(`differ: spawn failed: ${(e as { message: string }).message}`);
+        }
+      }
+
+      try {
+        await stat(reportPath);
+      } catch {
+        throw new Error(`differ: report file not found: ${reportPath}`);
+      }
+
+      const raw = JSON.stringify({ outputDocx, sourceDocx, diffReport: reportPath });
+      const meta = schema.parse(JSON.parse(raw)) as T;
+      return { meta, childThread: null };
+    };
+}