diff --git a/README.en.md b/README.en.md
index 10118b39..f3ddbf55 100644
--- a/README.en.md
+++ b/README.en.md
@@ -109,6 +109,10 @@ Get the latest build from [Releases](https://github.com/blueberrycongee/Lumina-N
 - Slash command extension API
 - Developer guide: `docs/plugin-ecosystem.md`
 
+<h3 align="center">Optional: Lumina Cloud (paid)</h3>
+
+If you'd rather not configure your own API keys, Lumina Cloud is a license-based add-on. A one-time founders purchase or a monthly subscription unlocks the "Lumina Cloud" provider in AI settings — same models, paid-by-Lumina inference. Local-first stays the default; cloud features only activate when a license is present. Learn more at [lumina-note.com](https://lumina-note.com).
+
 ---
 
 <h2 align="center">Quick Start</h2>
diff --git a/README.zh-CN.md b/README.zh-CN.md
index aacd0c59..3abc7116 100644
--- a/README.zh-CN.md
+++ b/README.zh-CN.md
@@ -102,6 +102,10 @@
 - Slash Command 扩展 API
 - 开发文档：`docs/plugin-ecosystem.md`
 
+<h3 align="center">可选：Lumina Cloud（付费）</h3>
+
+如果你不想自己配置 API key，Lumina Cloud 是基于许可证的可选服务。一次性买断或月度订阅可解锁 AI 设置中的 "Lumina Cloud" provider，模型一致，推理由 Lumina 承担。Lumina Note 默认仍然是 local-first，只有持有许可证时云端功能才会启用。详情见 [lumina-note.com](https://lumina-note.com)。
+
 ---
 
 <h2 align="center">快速开始</h2>
diff --git a/cloud/TASKS.md b/cloud/TASKS.md
index 9355abf1..d2a90b7f 100644
--- a/cloud/TASKS.md
+++ b/cloud/TASKS.md
@@ -117,7 +117,7 @@
 - **Acceptance:** `npm test -- src/__tests__/luminaCloud.e2e.test.ts` passes.
 
 ### C13 — README mention (subtle, not pushy)
-- [ ] **Goal:** Add a small "Optional: Lumina Cloud (paid)" subsection under the Features section in `README.en.md` and `README.zh-CN.md` only.
+- [x] **Goal:** Add a small "Optional: Lumina Cloud (paid)" subsection under the Features section in `README.en.md` and `README.zh-CN.md` only.
 - **Tone:** Match the existing brand voice (quiet, precise — see `PRODUCT.md` §3). One paragraph max. Link to the marketing site (placeholder URL `https://lumina-note.com` for now).
 - **Acceptance:** Diff is ≤ 15 lines per file.
 
@@ -138,3 +138,4 @@
 [x] C12 — 2026-04-28 — 381004c — e2e test (license → setLicense → visible → mock chat → usage delta) + invalid-signature + lifetime-only-no-cloud_ai paths; 3 tests
 [x] C3 — 2026-04-28 — d684a85 — license storage via safeStorage + Linux 0600 fallback; 3 additive lines in ipc.ts; 16 tests (11 main, 5 renderer)
 [x] C10 — 2026-04-28 — 9873ab7 — Account tab mounted in SettingsModal between Network and System; locale strings in en/zh-CN/zh-TW/ja; 7 tests pass (existing modal tests + new account-tab assertion)
+[x] C13 — 2026-04-28 — 0a47e8f — Optional: Lumina Cloud subsection added to README.en.md and README.zh-CN.md (4 lines each, brand-voice paragraph)