diff --git a/macos/scripts/write-theme.mjs b/macos/scripts/write-theme.mjs
index 3eca2c63..7e3dbb25 100644
--- a/macos/scripts/write-theme.mjs
+++ b/macos/scripts/write-theme.mjs
@@ -121,18 +121,22 @@ const name = validateText(valueFor("name", "我的 Codex Dream Skin"), "name", 8
 const tagline = validateText(
   valueFor("tagline", "把喜欢的画面变成可交互的 Codex 工作台。"),
   "tagline",
-  160,
+  120,
   "把喜欢的画面变成可交互的 Codex 工作台。",
 );
 const quote = validateText(
   valueFor("quote", "MAKE SOMETHING WONDERFUL"),
   "quote",
-  80,
+  120,
   "MAKE SOMETHING WONDERFUL",
 );
 const appearance = validateChoice(valueFor("appearance", "auto"), "appearance", ["auto", "light", "dark"]);
 const safeArea = validateChoice(valueFor("safe-area", "auto"), "safe-area", ["auto", "left", "right", "center", "none"]);
-const taskMode = validateChoice(valueFor("task-mode", "auto"), "task-mode", ["auto", "ambient", "banner", "off"]);
+const taskMode = validateChoice(
+  valueFor("task-mode", "auto"),
+  "task-mode",
+  ["auto", "ambient", "banner", "full", "off"],
+);
 const focusX = hasValue("focus-x") ? validateUnit(valueFor("focus-x"), "focus-x") : null;
 const focusY = hasValue("focus-y") ? validateUnit(valueFor("focus-y"), "focus-y") : null;
 
diff --git a/macos/tests/write-theme-contract.test.mjs b/macos/tests/write-theme-contract.test.mjs
new file mode 100644
index 00000000..2151a8e5
--- /dev/null
+++ b/macos/tests/write-theme-contract.test.mjs
@@ -0,0 +1,60 @@
+import assert from "node:assert/strict";
+import { spawn } from "node:child_process";
+import fs from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import test from "node:test";
+import { fileURLToPath } from "node:url";
+
+import { loadTheme } from "../scripts/injector.mjs";
+
+const here = path.dirname(fileURLToPath(import.meta.url));
+const macosRoot = path.resolve(here, "..");
+const writer = path.join(macosRoot, "scripts", "write-theme.mjs");
+const fixtureImage = path.join(macosRoot, "assets", "portal-hero.png");
+
+function run(command, args) {
+  return new Promise((resolve, reject) => {
+    const child = spawn(command, args, { stdio: ["ignore", "pipe", "pipe"] });
+    let stdout = "";
+    let stderr = "";
+    child.stdout.on("data", (chunk) => { stdout += chunk; });
+    child.stderr.on("data", (chunk) => { stderr += chunk; });
+    child.once("error", reject);
+    child.once("close", (code) => {
+      if (code === 0) resolve({ stdout, stderr });
+      else reject(new Error(stderr || stdout || `${command} exited with ${code}`));
+    });
+  });
+}
+
+test("custom theme writer matches the injector text and task-mode contract", async () => {
+  const output = await fs.mkdtemp(path.join(os.tmpdir(), "dreamskin-write-contract."));
+  try {
+    await fs.copyFile(fixtureImage, path.join(output, "background.png"));
+    const longTagline = "界".repeat(130);
+    const longQuote = "光".repeat(130);
+    await run(process.execPath, [
+      writer,
+      "custom",
+      "--output-dir", output,
+      "--image", "background.png",
+      "--name", "Writer contract fixture",
+      "--tagline", longTagline,
+      "--quote", longQuote,
+      "--task-mode", "full",
+    ]);
+
+    const raw = JSON.parse(await fs.readFile(path.join(output, "theme.json"), "utf8"));
+    assert.equal(Array.from(raw.tagline).length, 120);
+    assert.equal(Array.from(raw.quote).length, 120);
+    assert.equal(raw.art.taskMode, "full");
+
+    const loaded = await loadTheme(output);
+    assert.equal(loaded.theme.tagline, "界".repeat(120));
+    assert.equal(loaded.theme.quote, "光".repeat(120));
+    assert.equal(loaded.theme.art.taskMode, "full");
+  } finally {
+    await fs.rm(output, { recursive: true, force: true });
+  }
+});