Add --disable-file-cache flag

CHANGELOG.md

@@ -22,6 +22,13 @@ Code v99.99.999
 
 ## Unreleased
 
+### Added
+
+- `--disable-file-cache` keeps workspace files out of the browser cache. It
+  stops the webview service worker from storing them in Cache Storage and
+  serves them from `/vscode-remote-resource` with `Cache-Control: no-store`.
+  Extension files stay cached.
+
 ## [4.143.1](https://github.com/coder/code-server/releases/tag/v4.143.1) - 2026-10-23
 
 Code v1.143.1

patches/disable-file-cache.diff

@@ -0,0 +1,188 @@
+Add option to keep workspace files out of the browser cache
+
+This patch adds support for a new CLI flag called `--disable-file-cache`. When
+set, workspace files are not stored on the client disk through two caches:
+
+- The webview resource loader sends no ETag for a resource outside the
+  webview's own extension, and the webview service worker only stores responses
+  that have an ETag, so these resources stay out of Cache Storage.
+- `/vscode-remote-resource` responds with `Cache-Control: no-store` for files
+  outside the extension directories.
+
+Extension resources keep their ETags so webviews still load extension code from
+the cache. The default value for this is `false`.
+
+To test, start code-server with `--disable-file-cache`, open a Markdown file
+that embeds an image from the workspace, and open the preview. In the browser
+dev tools, the `vscode-resource-cache-*` Cache Storage of the webview service
+worker should have no entry for the image, and a request to
+`/vscode-remote-resource?path=<image>` should respond with
+`Cache-Control: no-store`.
+
+Index: code-server/lib/vscode/src/vs/server/node/remoteExtensionHostAgentServer.ts
+===================================================================
+--- code-server.orig/lib/vscode/src/vs/server/node/remoteExtensionHostAgentServer.ts
++++ code-server/lib/vscode/src/vs/server/node/remoteExtensionHostAgentServer.ts
+@@ -177,15 +177,14 @@ class RemoteExtensionHostAgentServer ext
+
+ 			const requestOrigin = req.headers['origin'];
+ 			const responseHeaders = getRemoteResourceResponseHeaders(requestOrigin, origin => this._webEndpointOriginChecker.matches(origin));
+-			if (this._environmentService.isBuilt) {
+-				if (isEqualOrParent(filePath, this._environmentService.builtinExtensionsPath, !platform.isLinux)
+-					|| isEqualOrParent(filePath, this._environmentService.extensionsPath, !platform.isLinux)
+-				) {
+-					responseHeaders['Cache-Control'] = 'public, max-age=31536000';
+-				}
++			const isExtensionFile = isEqualOrParent(filePath, this._environmentService.builtinExtensionsPath, !platform.isLinux)
++				|| isEqualOrParent(filePath, this._environmentService.extensionsPath, !platform.isLinux);
++			if (this._environmentService.isBuilt && isExtensionFile) {
++				responseHeaders['Cache-Control'] = 'public, max-age=31536000';
+ 			}
+
+-			return serveFile(filePath, CacheControl.ETAG, this._logService, req, res, responseHeaders);
++			const cacheControl = this._environmentService.args['disable-file-cache'] && !isExtensionFile ? CacheControl.NO_CACHING : CacheControl.ETAG;
++			return serveFile(filePath, cacheControl, this._logService, req, res, responseHeaders);
+ 		}
+
+ 		// workbench web UI
+Index: code-server/lib/vscode/src/vs/server/node/serverEnvironmentService.ts
+===================================================================
+--- code-server.orig/lib/vscode/src/vs/server/node/serverEnvironmentService.ts
++++ code-server/lib/vscode/src/vs/server/node/serverEnvironmentService.ts
+@@ -37,6 +37,7 @@ export const serverOptions: OptionDescri
+ 	'auth': { type: 'string' },
+ 	'disable-file-downloads': { type: 'boolean' },
+ 	'disable-file-uploads': { type: 'boolean' },
++	'disable-file-cache': { type: 'boolean' },
+ 	'disable-getting-started-override': { type: 'boolean' },
+ 	'locale': { type: 'string' },
+ 	'link-protection-trusted-domains': { type: 'string[]' },
+@@ -139,6 +140,7 @@ export interface ServerParsedArgs {
+ 	'auth'?: string;
+ 	'disable-file-downloads'?: boolean;
+ 	'disable-file-uploads'?: boolean;
++	'disable-file-cache'?: boolean;
+ 	'disable-getting-started-override'?: boolean,
+ 	'locale'?: string
+ 	'link-protection-trusted-domains'?: string[],
+Index: code-server/lib/vscode/src/vs/server/node/webClientServer.ts
+===================================================================
+--- code-server.orig/lib/vscode/src/vs/server/node/webClientServer.ts
++++ code-server/lib/vscode/src/vs/server/node/webClientServer.ts
+@@ -442,6 +442,7 @@ export class WebClientServer {
+ 			userDataPath: this._environmentService.userDataPath,
+ 			isEnabledFileDownloads: !this._environmentService.args['disable-file-downloads'],
+ 			isEnabledFileUploads: !this._environmentService.args['disable-file-uploads'],
++			isEnabledFileCache: !this._environmentService.args['disable-file-cache'],
+ 			isEnabledCoderGettingStarted: !this._environmentService.args['disable-getting-started-override'],
+ 			_wrapWebWorkerExtHostInIframe,
+ 			developmentOptions: { enableSmokeTestDriver: this._environmentService.args['enable-smoke-test-driver'] ? true : undefined, logLevel: this._logService.getLevel() },
+Index: code-server/lib/vscode/src/vs/workbench/browser/web.api.ts
+===================================================================
+--- code-server.orig/lib/vscode/src/vs/workbench/browser/web.api.ts
++++ code-server/lib/vscode/src/vs/workbench/browser/web.api.ts
+@@ -330,6 +330,11 @@ export interface IWorkbenchConstructionO
+ 	readonly isEnabledFileUploads?: boolean
+
+ 	/**
++	 * Whether the browser may cache workspace files.
++	 */
++	readonly isEnabledFileCache?: boolean
++
++	/**
+ 	 * Whether to use Coder's custom Getting Started text.
+ 	 */
+ 	readonly isEnabledCoderGettingStarted?: boolean
+Index: code-server/lib/vscode/src/vs/workbench/contrib/webview/browser/webviewElement.ts
+===================================================================
+--- code-server.orig/lib/vscode/src/vs/workbench/contrib/webview/browser/webviewElement.ts
++++ code-server/lib/vscode/src/vs/workbench/contrib/webview/browser/webviewElement.ts
+@@ -15,7 +15,7 @@ import { Lazy } from '../../../../base/c
+ import { Disposable, DisposableStore, IDisposable, MutableDisposable, toDisposable } from '../../../../base/common/lifecycle.js';
+ import { COI, Schemas } from '../../../../base/common/network.js';
+ import { observableValue } from '../../../../base/common/observable.js';
+-import { isEqualAuthority } from '../../../../base/common/resources.js';
++import { isEqualAuthority, isEqualOrParent } from '../../../../base/common/resources.js';
+ import { listenStream } from '../../../../base/common/stream.js';
+ import { URI } from '../../../../base/common/uri.js';
+ import { generateUuid } from '../../../../base/common/uuid.js';
+@@ -32,6 +32,7 @@ import { INotificationService } from '..
+ import { IRemoteAuthorityResolverService } from '../../../../platform/remote/common/remoteAuthorityResolver.js';
+ import { ITunnelService } from '../../../../platform/tunnel/common/tunnel.js';
+ import { WebviewPortMappingManager } from '../../../../platform/webview/common/webviewPortMapping.js';
++import { IBrowserWorkbenchEnvironmentService } from '../../../services/environment/browser/environmentService.js';
+ import { IWorkbenchEnvironmentService } from '../../../services/environment/common/environmentService.js';
+ import { IRemoteAgentService } from '../../../services/remote/common/remoteAgentService.js';
+ import { decodeAuthority, webviewGenericCspSource, webviewRootResourceAuthority } from '../common/webview.js';
+@@ -864,6 +865,8 @@ export class WebviewElement extends Disp
+ 					const rangeHeader = range
+ 						? `bytes ${range.start}-${rangeEnd}/${result.size}`
+ 						: undefined;
++					// The service worker only stores responses that have an etag.
++					const etag = this._isFileCacheAllowed(uri) ? result.etag : undefined;
+ 					if (WebviewElement._supportsTransferableStreams.value) {
+ 						let controller: ReadableStreamDefaultController<Uint8Array<ArrayBuffer>> | undefined;
+ 						let closed = false;
+@@ -915,7 +918,7 @@ export class WebviewElement extends Disp
+ 							status: range ? 206 : 200,
+ 							path: uri.path,
+ 							mime: result.mimeType,
+-							etag: result.etag,
++							etag,
+ 							mtime: result.mtime,
+ 							range: rangeHeader,
+ 							stream,
+@@ -927,7 +930,7 @@ export class WebviewElement extends Disp
+ 							status: range ? 206 : 200,
+ 							path: uri.path,
+ 							mime: result.mimeType,
+-							etag: result.etag,
++							etag,
+ 							mtime: result.mtime,
+ 							range: rangeHeader,
+ 						});
+@@ -984,6 +987,14 @@ export class WebviewElement extends Disp
+ 		});
+ 	}
+
++	private _isFileCacheAllowed(uri: URI): boolean {
++		if ((this._environmentService as IBrowserWorkbenchEnvironmentService).isEnabledFileCache) {
++			return true;
++		}
++		const extensionLocation = this.extension?.location;
++		return !!extensionLocation && isEqualOrParent(uri, extensionLocation);
++	}
++
+ 	private async localLocalhost(id: string, origin: string) {
+ 		const authority = this._environmentService.remoteAuthority;
+ 		const resolveAuthority = authority ? await this._remoteAuthorityResolverService.resolveAuthority(authority) : undefined;
+Index: code-server/lib/vscode/src/vs/workbench/services/environment/browser/environmentService.ts
+===================================================================
+--- code-server.orig/lib/vscode/src/vs/workbench/services/environment/browser/environmentService.ts
++++ code-server/lib/vscode/src/vs/workbench/services/environment/browser/environmentService.ts
+@@ -49,6 +49,11 @@ export interface IBrowserWorkbenchEnviro
+ 	readonly isEnabledFileUploads?: boolean;
+
+ 	/**
++	 * Allow the browser to cache workspace files.
++	 */
++	readonly isEnabledFileCache?: boolean;
++
++	/**
+ 	 * Enable Coder's custom getting started text.
+ 	 */
+ 	readonly isEnabledCoderGettingStarted?: boolean;
+@@ -145,6 +150,13 @@ export class BrowserWorkbenchEnvironment
+ 		return this.options.isEnabledFileUploads;
+ 	}
+
++	get isEnabledFileCache(): boolean {
++		if (typeof this.options.isEnabledFileCache === "undefined") {
++			throw new Error('isEnabledFileCache was not provided to the browser');
++		}
++		return this.options.isEnabledFileCache;
++	}
++
+ 	get isEnabledCoderGettingStarted(): boolean {
+ 		if (typeof this.options.isEnabledCoderGettingStarted === "undefined") {
+ 			throw new Error('isEnabledCoderGettingStarted was not provided to the browser');

patches/series

@@ -27,3 +27,4 @@ app-name.diff
 remote-storage.diff
 remote-secret-storage.diff
 csp-hashes.diff
+disable-file-cache.diff

src/node/cli.ts

@@ -51,6 +51,7 @@ export interface UserProvidedCodeArgs {
   "disable-update-check"?: boolean
   "disable-file-downloads"?: boolean
   "disable-file-uploads"?: boolean
+  "disable-file-cache"?: boolean
   "disable-workspace-trust"?: boolean
   "disable-getting-started-override"?: boolean
   "disable-proxy"?: boolean
@@ -193,6 +194,10 @@ export const options: Options<Required<UserProvidedArgs>> = {
     type: "boolean",
     description: "Disable file uploads.",
   },
+  "disable-file-cache": {
+    type: "boolean",
+    description: "Keep workspace files out of the browser cache.",
+  },
   "disable-workspace-trust": {
     type: "boolean",
     description: "Disable Workspace Trust feature. This switch only affects the current session.",

test/e2e/fileCache.test.ts

@@ -0,0 +1,132 @@
+import { promises as fs } from "fs"
+import * as path from "path"
+import { Page } from "playwright"
+import { clean, getMaybeProxiedCodeServer } from "../utils/helpers"
+import { describe, test, expect } from "./baseFixture"
+import { CodeServerPage } from "./models/CodeServer"
+
+// A 1x1 PNG.
+const png = Buffer.from(
+  "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNkYPhfDwAChwGA60e6kgAAAABJRU5ErkJggg==",
+  "base64",
+)
+
+/**
+ * Open a Markdown preview that embeds a PNG from the workspace and wait for
+ * the image to render.
+ */
+async function previewMarkdownWithImage(codeServerPage: CodeServerPage, imageName: string): Promise<Page> {
+  const dir = await codeServerPage.workspaceDir
+  await fs.writeFile(path.join(dir, imageName), png)
+  const markdown = path.join(dir, `${imageName}.md`)
+  await fs.writeFile(markdown, `# Preview\n\n![workspace image](${imageName})\n`)
+  await codeServerPage.openFile(markdown)
+  await codeServerPage.executeCommandViaMenus("Markdown: Open Preview to the Side")
+  await codeServerPage.waitForTab(`Preview ${markdown}`)
+
+  const image = codeServerPage.page
+    .frameLocator("iframe.webview.ready")
+    .frameLocator("#active-frame")
+    .locator(`img[alt="workspace image"]`)
+  await expect.poll(() => image.evaluate((img: HTMLImageElement) => img.naturalWidth)).toBeGreaterThan(0)
+  return codeServerPage.page
+}
+
+/**
+ * URLs in the webview service worker's Cache Storage.
+ */
+async function cachedWebviewUrls(page: Page): Promise<string[]> {
+  const frame = await (await page.locator("iframe.webview.ready").elementHandle())?.contentFrame()
+  if (!frame) {
+    throw new Error("webview frame not found")
+  }
+  return frame.evaluate(async () => {
+    const urls: string[] = []
+    for (const name of await caches.keys()) {
+      if (name.startsWith("vscode-resource-cache-")) {
+        for (const request of await (await caches.open(name)).keys()) {
+          urls.push(request.url)
+        }
+      }
+    }
+    return urls
+  })
+}
+
+async function fetchRemoteResource(codeServerPage: CodeServerPage, file: string) {
+  const address = await getMaybeProxiedCodeServer(codeServerPage)
+  const url = new URL(`vscode-remote-resource?path=${encodeURIComponent(file)}`, address)
+  return codeServerPage.page.request.get(url.toString())
+}
+
+/**
+ * Write a workspace file and a file in the user extensions directory.
+ */
+async function writeResourceFiles(codeServerPage: CodeServerPage, name: string) {
+  const dir = await codeServerPage.workspaceDir
+  const workspaceFile = path.join(dir, `${name}-workspace.txt`)
+  const extensionDir = path.join(dir, "extensions", `${name}-extension`)
+  const extensionFile = path.join(extensionDir, "resource.txt")
+  await fs.writeFile(workspaceFile, "workspace")
+  await fs.mkdir(extensionDir, { recursive: true })
+  await fs.writeFile(extensionFile, "extension")
+  return { workspaceFile, extensionFile }
+}
+
+describe("File cache (enabled)", ["--disable-workspace-trust"], {}, async () => {
+  const testName = "file-cache-enabled"
+  test.beforeAll(async () => {
+    await clean(testName)
+  })
+
+  test("should cache workspace files in the webview Cache Storage", async ({ codeServerPage }) => {
+    const page = await previewMarkdownWithImage(codeServerPage, "cache-enabled.png")
+    await expect
+      .poll(async () => (await cachedWebviewUrls(page)).filter((url) => url.includes("cache-enabled.png")))
+      .toHaveLength(1)
+  })
+
+  test("should serve /vscode-remote-resource with an ETag and without no-store", async ({ codeServerPage }) => {
+    const { workspaceFile, extensionFile } = await writeResourceFiles(codeServerPage, "enabled")
+    for (const file of [workspaceFile, extensionFile]) {
+      const response = await fetchRemoteResource(codeServerPage, file)
+      expect(response.status()).toBe(200)
+      expect(response.headers()["etag"]).toBeTruthy()
+      expect(response.headers()["cache-control"] ?? "").not.toContain("no-store")
+    }
+  })
+})
+
+describe("File cache (disabled)", ["--disable-workspace-trust", "--disable-file-cache"], {}, async () => {
+  const testName = "file-cache-disabled"
+  test.beforeAll(async () => {
+    await clean(testName)
+  })
+
+  test("should keep workspace files out of the webview Cache Storage but cache extension files", async ({
+    codeServerPage,
+  }) => {
+    const page = await previewMarkdownWithImage(codeServerPage, "cache-disabled.png")
+    // Cached extension files show that the flag, not a cache failure, keeps the image out.
+    await expect
+      .poll(async () => (await cachedWebviewUrls(page)).filter((url) => url.includes("markdown-language-features")))
+      .not.toHaveLength(0)
+    expect((await cachedWebviewUrls(page)).filter((url) => url.includes("cache-disabled.png"))).toHaveLength(0)
+  })
+
+  test("should serve /vscode-remote-resource with no-store for workspace files and an ETag for extension files", async ({
+    codeServerPage,
+  }) => {
+    const { workspaceFile, extensionFile } = await writeResourceFiles(codeServerPage, "disabled")
+
+    const workspaceResponse = await fetchRemoteResource(codeServerPage, workspaceFile)
+    expect(workspaceResponse.status()).toBe(200)
+    expect(workspaceResponse.headers()["cache-control"]).toBe("no-store")
+    expect(workspaceResponse.headers()["etag"]).toBeUndefined()
+
+    const extensionResponse = await fetchRemoteResource(codeServerPage, extensionFile)
+    expect(extensionResponse.status()).toBe(200)
+    expect(extensionResponse.headers()["etag"]).toBeTruthy()
+    expect(extensionResponse.headers()["cache-control"] ?? "").not.toContain("no-store")
+  })
+})

test/unit/node/cli.test.ts

@@ -109,6 +109,8 @@ describe("parser", () => {
 
           "--disable-file-downloads",
 
+          "--disable-file-cache",
+
           "--disable-getting-started-override",
 
           "--disable-proxy",
@@ -137,6 +139,7 @@ describe("parser", () => {
       cert: {
         value: path.resolve("path/to/cert"),
       },
+      "disable-file-cache": true,
       "disable-file-downloads": true,
       "disable-getting-started-override": true,
       "disable-proxy": true,