diff --git a/.github/workflows/pull_request.yaml b/.github/workflows/pull_request.yaml
index a7132b3..d29ae8f 100644
--- a/.github/workflows/pull_request.yaml
+++ b/.github/workflows/pull_request.yaml
@@ -49,6 +49,9 @@ jobs:
     - run: yarn install --frozen-lockfile --network-timeout 120000
     - run: yarn run typecheck
     - run: yarn run lint
+    # Windows checkouts get CRLF line endings, which prettier reports as unformatted.
+    - run: yarn run format:check
+      if: runner.os == 'Linux'
     - run: yarn run build
     - run: yarn run test
     # Sanity-check `npm pack` only once (Linux + Node 24) to avoid
diff --git a/.prettierignore b/.prettierignore
new file mode 100644
index 0000000..2e8551b
--- /dev/null
+++ b/.prettierignore
@@ -0,0 +1,4 @@
+.scoria/
+scoria.config.json
+dist/
+coverage/
diff --git a/.prettierrc b/.prettierrc
new file mode 100644
index 0000000..91a3517
--- /dev/null
+++ b/.prettierrc
@@ -0,0 +1,3 @@
+{
+  "printWidth": 160
+}
diff --git a/demo/App.vue b/demo/App.vue
index e05893e..dfe9989 100644
--- a/demo/App.vue
+++ b/demo/App.vue
@@ -36,12 +36,7 @@
     <div v-if="ViewComponent" class="bg-white rounded-lg p-5 mb-5 shadow-md">
       <h2 class="text-gray-600 text-xl mb-4">View Component</h2>
       <div class="border border-gray-200 rounded p-4">
-        <component
-          :is="ViewComponent"
-          :selectedResult="result"
-          :sendTextMessage="handleSendTextMessage"
-          @updateResult="handleUpdate"
-        />
+        <component :is="ViewComponent" :selectedResult="result" :sendTextMessage="handleSendTextMessage" @updateResult="handleUpdate" />
       </div>
       <div v-if="lastSentMessage" class="mt-4 p-3 bg-emerald-50 border border-emerald-200 rounded-md">
         <strong class="text-emerald-800 block mb-2">Sent Message:</strong>
diff --git a/demo/markdownArgs.ts b/demo/markdownArgs.ts
index 06a89fa..21fb257 100644
--- a/demo/markdownArgs.ts
+++ b/demo/markdownArgs.ts
@@ -1,7 +1,6 @@
 import type { MarkdownArgs } from "../src/core/types";
 
-const isRecord = (value: unknown): value is Record<string, unknown> =>
-  typeof value === "object" && value !== null && !Array.isArray(value);
+const isRecord = (value: unknown): value is Record<string, unknown> => typeof value === "object" && value !== null && !Array.isArray(value);
 
 export const isMarkdownArgs = (value: unknown): value is MarkdownArgs =>
   isRecord(value) &&
diff --git a/package.json b/package.json
index e869d2c..f8829c3 100644
--- a/package.json
+++ b/package.json
@@ -33,7 +33,9 @@
     "preview": "vite preview",
     "test": "tsx --test tests/*.test.ts",
     "quality": "scoria",
-    "test:coverage": "c8 yarn run test"
+    "test:coverage": "c8 yarn run test",
+    "format": "prettier --write \"{src,demo,tests}/**/*.{ts,tsx,vue,json,css}\" \"*.{ts,js,json}\"",
+    "format:check": "prettier --check \"{src,demo,tests}/**/*.{ts,tsx,vue,json,css}\" \"*.{ts,js,json}\""
   },
   "resolutions": {
     "minimatch": "^10.2.4"
@@ -53,6 +55,7 @@
     "eslint-plugin-vue": "^10.11.1",
     "globals": "^17.13.0",
     "gui-chat-protocol": "^2.3.0",
+    "prettier": "^3.9.10",
     "scoria": "^0.4.1",
     "tailwindcss": "^4.3.3",
     "tsx": "^4.23.15",
diff --git a/src/core/hostResponse.ts b/src/core/hostResponse.ts
index fd7412a..dd45986 100644
--- a/src/core/hostResponse.ts
+++ b/src/core/hostResponse.ts
@@ -7,29 +7,17 @@ export interface SaveImagesResponse {
   imageUrls?: Record<string, string>;
 }
 
-const isRecord = (value: unknown): value is Record<string, unknown> =>
-  typeof value === "object" && value !== null;
+const isRecord = (value: unknown): value is Record<string, unknown> => typeof value === "object" && value !== null;
 
-const isOptionalString = (value: unknown): value is string | undefined =>
-  value === undefined || typeof value === "string";
+const isOptionalString = (value: unknown): value is string | undefined => value === undefined || typeof value === "string";
 
-const isStringRecord = (value: unknown): value is Record<string, string> =>
-  isRecord(value) &&
-  Object.values(value).every((item) => typeof item === "string");
+const isStringRecord = (value: unknown): value is Record<string, string> => isRecord(value) && Object.values(value).every((item) => typeof item === "string");
 
-export const isGeneratedImageResponse = (
-  value: unknown,
-): value is GeneratedImageResponse =>
-  isRecord(value) &&
-  typeof value.success === "boolean" &&
-  isOptionalString(value.imageData);
+export const isGeneratedImageResponse = (value: unknown): value is GeneratedImageResponse =>
+  isRecord(value) && typeof value.success === "boolean" && isOptionalString(value.imageData);
 
-export const isSaveImagesResponse = (
-  value: unknown,
-): value is SaveImagesResponse =>
-  isRecord(value) &&
-  (value.imageUrls === undefined || isStringRecord(value.imageUrls));
+export const isSaveImagesResponse = (value: unknown): value is SaveImagesResponse =>
+  isRecord(value) && (value.imageUrls === undefined || isStringRecord(value.imageUrls));
 
 /** `loadBlankImageBase64` returns the reference image; anything else is "no reference". */
-export const readBlankImageBase64 = (value: unknown): string =>
-  typeof value === "string" ? value : "";
+export const readBlankImageBase64 = (value: unknown): string => (typeof value === "string" ? value : "");
diff --git a/src/core/plugin.ts b/src/core/plugin.ts
index 5cc87fa..d530cb4 100644
--- a/src/core/plugin.ts
+++ b/src/core/plugin.ts
@@ -1,19 +1,12 @@
 import type { ToolContext, ToolPluginCore } from "gui-chat-protocol";
 import type { MarkdownArgs, MarkdownToolData, MarkdownResult } from "./types";
-import {
-  isGeneratedImageResponse,
-  isSaveImagesResponse,
-  readBlankImageBase64,
-} from "./hostResponse";
+import { isGeneratedImageResponse, isSaveImagesResponse, readBlankImageBase64 } from "./hostResponse";
 import { TOOL_NAME, TOOL_DEFINITION } from "./definition";
 
 // context is nullable on purpose: hosts that run the plugin without client-side
 // state (MulmoClaude's server bridge) pass an empty or missing context, and
 // reading through it unguarded threw a TypeError instead of returning a result.
-export const presentDocument = async (
-  context: ToolContext | null | undefined,
-  args: MarkdownArgs,
-): Promise<MarkdownResult> => {
+export const presentDocument = async (context: ToolContext | null | undefined, args: MarkdownArgs): Promise<MarkdownResult> => {
   let { markdown } = args;
   const { title, filenameHint } = args;
   const app = context?.app;
@@ -34,9 +27,7 @@ export const presentDocument = async (
     const images: Record<string, string> = {};
 
     // Load blank image for aspect ratio reference
-    const blankImageBase64 = app.loadBlankImageBase64
-      ? readBlankImageBase64(await app.loadBlankImageBase64())
-      : "";
+    const blankImageBase64 = app.loadBlankImageBase64 ? readBlankImageBase64(await app.loadBlankImageBase64()) : "";
 
     // Generate images for each placeholder in parallel
     const imagePromises = matches.map(async (match, i) => {
@@ -44,11 +35,7 @@ export const presentDocument = async (
       const imageId = `image_${i}`;
 
       try {
-        const result = await app!.generateImageWithBackend!(
-          prompt,
-          blankImageBase64 ? [blankImageBase64] : [],
-          context,
-        );
+        const result = await app!.generateImageWithBackend!(prompt, blankImageBase64 ? [blankImageBase64] : [], context);
 
         if (isGeneratedImageResponse(result) && result.success && result.imageData) {
           images[imageId] = `data:image/png;base64,${result.imageData}`;
@@ -87,8 +74,7 @@ export const presentDocument = async (
       title,
       data: { markdown, filenameHint },
       uuid: docUuid,
-      instructions:
-        "Acknowledge that the document has been created and is displayed to the user.",
+      instructions: "Acknowledge that the document has been created and is displayed to the user.",
     };
   }
 
@@ -96,8 +82,7 @@ export const presentDocument = async (
     message: `Created markdown document: ${title}`,
     title,
     data: { markdown, filenameHint },
-    instructions:
-      "Acknowledge that the document has been created and is displayed to the user.",
+    instructions: "Acknowledge that the document has been created and is displayed to the user.",
   };
 };
 
@@ -105,8 +90,7 @@ export const pluginCore: ToolPluginCore<MarkdownToolData, unknown, MarkdownArgs>
   toolDefinition: TOOL_DEFINITION,
   execute: presentDocument,
   generatingMessage: "Creating document...",
-  waitingMessage:
-    "Tell the user that the document was created, will be presented to the user shortly.",
+  waitingMessage: "Tell the user that the document was created, will be presented to the user shortly.",
   isEnabled: () => true,
   backends: ["imageGen"],
 };
diff --git a/src/vue/View.vue b/src/vue/View.vue
index b50a8fa..ec0d50e 100644
--- a/src/vue/View.vue
+++ b/src/vue/View.vue
@@ -1,9 +1,6 @@
 <template>
   <div class="markdown-container">
-    <div
-      v-if="!selectedResult.data?.markdown"
-      class="min-h-full p-8 flex items-center justify-center"
-    >
+    <div v-if="!selectedResult.data?.markdown" class="min-h-full p-8 flex items-center justify-center">
       <div class="text-gray-500">No markdown content available</div>
     </div>
     <template v-else>
@@ -20,27 +17,14 @@
               </button>
             </div>
           </div>
-          <div
-            class="markdown-content prose prose-slate max-w-none"
-            v-html="renderedHtml"
-          ></div>
+          <div class="markdown-content prose prose-slate max-w-none" v-html="renderedHtml"></div>
         </div>
       </div>
 
       <details class="markdown-source">
         <summary>Edit Markdown Source</summary>
-        <textarea
-          v-model="editableMarkdown"
-          class="markdown-editor"
-          spellcheck="false"
-        ></textarea>
-        <button
-          @click="applyMarkdown"
-          class="apply-btn"
-          :disabled="!hasChanges"
-        >
-          Apply Changes
-        </button>
+        <textarea v-model="editableMarkdown" class="markdown-editor" spellcheck="false"></textarea>
+        <button @click="applyMarkdown" class="apply-btn" :disabled="!hasChanges">Apply Changes</button>
       </details>
     </template>
   </div>
diff --git a/src/vue/index.ts b/src/vue/index.ts
index 7f50e59..d9b58b9 100644
--- a/src/vue/index.ts
+++ b/src/vue/index.ts
@@ -34,11 +34,7 @@ export const plugin: ToolPlugin<MarkdownToolData, unknown, MarkdownArgs> = {
 
 export type { MarkdownToolData, MarkdownArgs, MarkdownResult } from "../core/types";
 
-export {
-  TOOL_DEFINITION,
-  executeMarkdown,
-  pluginCore,
-} from "../core/plugin";
+export { TOOL_DEFINITION, executeMarkdown, pluginCore } from "../core/plugin";
 
 export { samples } from "../core/samples";
 
diff --git a/tests/hostResponse.test.ts b/tests/hostResponse.test.ts
index 18f438d..669d9d1 100644
--- a/tests/hostResponse.test.ts
+++ b/tests/hostResponse.test.ts
@@ -7,18 +7,11 @@
 
 import { test, describe } from "node:test";
 import assert from "node:assert";
-import {
-  isGeneratedImageResponse,
-  isSaveImagesResponse,
-  readBlankImageBase64,
-} from "../src/core/hostResponse.js";
+import { isGeneratedImageResponse, isSaveImagesResponse, readBlankImageBase64 } from "../src/core/hostResponse.js";
 
 describe("isGeneratedImageResponse", () => {
   test("accepts a successful response carrying image data", () => {
-    assert.equal(
-      isGeneratedImageResponse({ success: true, imageData: "base64" }),
-      true,
-    );
+    assert.equal(isGeneratedImageResponse({ success: true, imageData: "base64" }), true);
   });
 
   test("accepts a failure response with no image data", () => {
@@ -31,21 +24,14 @@ describe("isGeneratedImageResponse", () => {
 
   test("rejects values that are not a response object", () => {
     [null, undefined, "ok", 7].forEach((value) => {
-      assert.equal(
-        isGeneratedImageResponse(value),
-        false,
-        `should reject ${JSON.stringify(value)}`,
-      );
+      assert.equal(isGeneratedImageResponse(value), false, `should reject ${JSON.stringify(value)}`);
     });
   });
 });
 
 describe("isSaveImagesResponse", () => {
   test("accepts a map of image id to url", () => {
-    assert.equal(
-      isSaveImagesResponse({ imageUrls: { image_0: "/a.png", image_1: "/b.png" } }),
-      true,
-    );
+    assert.equal(isSaveImagesResponse({ imageUrls: { image_0: "/a.png", image_1: "/b.png" } }), true);
   });
 
   test("accepts a response with no imageUrls key", () => {
@@ -58,11 +44,7 @@ describe("isSaveImagesResponse", () => {
 
   test("rejects values that are not a response object", () => {
     [null, undefined, "ok", 7].forEach((value) => {
-      assert.equal(
-        isSaveImagesResponse(value),
-        false,
-        `should reject ${JSON.stringify(value)}`,
-      );
+      assert.equal(isSaveImagesResponse(value), false, `should reject ${JSON.stringify(value)}`);
     });
   });
 });
diff --git a/tests/plugin.test.ts b/tests/plugin.test.ts
index 3111bfa..effd50a 100644
--- a/tests/plugin.test.ts
+++ b/tests/plugin.test.ts
@@ -23,14 +23,8 @@ const CONTEXTS: [string, unknown][] = [
 describe("GUIChatPluginMarkdown - host provides no context", () => {
   CONTEXTS.forEach(([label, context]) => {
     test(`returns a result instead of throwing when context is ${label}`, async () => {
-      const result = await pluginCore.execute(
-        context as never,
-        ARGS as never,
-      );
-      assert.ok(
-        result && typeof result === "object",
-        "execute must resolve to a ToolResult rather than throw",
-      );
+      const result = await pluginCore.execute(context as never, ARGS as never);
+      assert.ok(result && typeof result === "object", "execute must resolve to a ToolResult rather than throw");
     });
   });
 });
diff --git a/tsconfig.eslint.json b/tsconfig.eslint.json
index 2d3f8e8..dd7ce28 100644
--- a/tsconfig.eslint.json
+++ b/tsconfig.eslint.json
@@ -7,17 +7,6 @@
     "declarationDir": null,
     "jsx": "react-jsx"
   },
-  "include": [
-    "*.ts",
-    "src/**/*.ts",
-    "src/**/*.tsx",
-    "src/**/*.vue",
-    "demo/**/*.ts",
-    "demo/**/*.tsx",
-    "demo/**/*.vue"
-  ],
-  "exclude": [
-    "node_modules",
-    "dist"
-  ]
+  "include": ["*.ts", "src/**/*.ts", "src/**/*.tsx", "src/**/*.vue", "demo/**/*.ts", "demo/**/*.tsx", "demo/**/*.vue"],
+  "exclude": ["node_modules", "dist"]
 }
diff --git a/vite.config.ts b/vite.config.ts
index ba79970..2342c4d 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -14,8 +14,7 @@ export default defineConfig({
       },
       name: "GUIChatPluginMarkdown",
       formats: ["es", "cjs"],
-      fileName: (format, entryName) =>
-        `${entryName}.${format === "es" ? "js" : "cjs"}`,
+      fileName: (format, entryName) => `${entryName}.${format === "es" ? "js" : "cjs"}`,
     },
     rollupOptions: {
       external: ["vue"],
diff --git a/yarn.lock b/yarn.lock
index 872c4be..11614f7 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3000,6 +3000,11 @@ prelude-ls@^1.2.1:
   resolved "https://registry.yarnpkg.com/prelude-ls/-/prelude-ls-1.2.1.tgz#debc6489d7a6e6b0e7611888cec880337d316396"
   integrity sha512-vkcDPrRZo1QZLbn5RLGPpg/WmIQ65qoWWhcGKf/b5eplkkarX0m9z8ppCat4mlOqUsWpyNuYgO3VRyrYHSzX5g==
 
+prettier@^3.9.10:
+  version "3.9.10"
+  resolved "https://registry.yarnpkg.com/prettier/-/prettier-3.9.10.tgz#ac378e432f1a7381518f2e080816bbaefa38d585"
+  integrity sha512-skGHTH1Yb9QvaTC4hWnRTzEYtCpApF0UMBPz+t/0ZPzP8ihefo/btKd+QA7pUE0fEwA1SbS/NmhyEcstdXOIdA==
+
 pretty-ms@^7.0.1:
   version "7.0.1"
   resolved "https://registry.yarnpkg.com/pretty-ms/-/pretty-ms-7.0.1.tgz#7d903eaab281f7d8e03c66f867e239dc32fb73e8"