fix(ssh): write Windows ProxyCommand paths with forward slashes

CHANGELOG.md

@@ -23,6 +23,9 @@
   a backtick, `\`, `%` or a line break.
 - On Windows, a `coder.headerCommand` containing `"` was split into several
   arguments before it reached the CLI.
+- On Windows, the open source Remote - SSH extension 0.4.0 dropped every `\`
+  from the paths in the SSH `ProxyCommand`. Drive-letter paths are now written
+  with `/`.
 
 ## [v1.17.0](https://github.com/coder/vscode-coder/releases/tag/v1.17.0) 2026-10-13
 

src/common/strings.ts

@@ -57,3 +57,15 @@ export function escapeShellArg(arg: string): string {
 export function escapeProxyCommandArg(arg: string): string {
 	return /[$`\\%\r\n]/.test(arg) ? escapeShellArg(arg) : escapeCommandArg(arg);
 }
+
+/**
+ * {@link escapeProxyCommandArg} for a local path. Windows drive paths use `/`,
+ * which every runner accepts; open-remote-ssh 0.4.0 strips `\` as an escape.
+ */
+export function escapeProxyCommandPath(filePath: string): string {
+	const portable =
+		os.platform() === "win32" && /^[a-z]:\\/i.test(filePath)
+			? filePath.replaceAll("\\", "/")
+			: filePath;
+	return escapeProxyCommandArg(portable);
+}

src/remote/remote.ts

@@ -18,7 +18,7 @@ import { HttpStatusCode } from "../api/httpStatusCode";
 import { extractAgents } from "../api/models";
 import { version as cliVersion } from "../cli/cliExec";
 import { expandPath } from "../common/fs";
-import { escapeCommandArg } from "../common/strings";
+import { escapeCommandArg, escapeProxyCommandPath } from "../common/strings";
 import {
 	CONFIG_CHANGE_DEBOUNCE_MS,
 	watchConfigurationChanges,
@@ -865,7 +865,7 @@ export class Remote {
 		}
 		await fs.mkdir(logDir, { recursive: true });
 		this.logger.info("SSH proxy diagnostics are being written to", logDir);
-		return ["--log-dir", escapeCommandArg(logDir), "-v"];
+		return ["--log-dir", escapeProxyCommandPath(logDir), "-v"];
 	}
 
 	private getMainSshConfigPath(): string {
@@ -1114,7 +1114,7 @@ function coderCommand(
 		vscode.workspace.getConfiguration(),
 		options.cliAuth,
 	);
-	return `${escapeCommandArg(options.binaryPath)} ${globalFlags.join(" ")} ${subcommand} ${flags.join(" ")}`;
+	return `${escapeProxyCommandPath(options.binaryPath)} ${globalFlags.join(" ")} ${subcommand} ${flags.join(" ")}`;
 }
 
 /** ProxyCommand for CLIs that support wildcard hosts. */
@@ -1126,7 +1126,7 @@ export function buildSshProxyCommand(
 		"--stdio",
 		`--usage-app=${escapeCommandArg(options.sessionApp)}`,
 		"--network-info-dir",
-		escapeCommandArg(options.pathResolver.getNetworkInfoPath()),
+		escapeProxyCommandPath(options.pathResolver.getNetworkInfoPath()),
 		...options.logArgs,
 		"--ssh-host-prefix",
 		options.hostPrefix,
@@ -1145,12 +1145,12 @@ function buildVscodeSshProxyCommand(
 	const { pathResolver, label } = options;
 	return coderCommand(options, "vscodessh", [
 		"--network-info-dir",
-		escapeCommandArg(pathResolver.getNetworkInfoPath()),
+		escapeProxyCommandPath(pathResolver.getNetworkInfoPath()),
 		...options.logArgs,
 		"--session-token-file",
-		escapeCommandArg(pathResolver.getSessionTokenPath(label)),
+		escapeProxyCommandPath(pathResolver.getSessionTokenPath(label)),
 		"--url-file",
-		escapeCommandArg(pathResolver.getUrlPath(label)),
+		escapeProxyCommandPath(pathResolver.getUrlPath(label)),
 		"%h",
 	]);
 }

src/settings/cli.ts

@@ -1,7 +1,11 @@
 import os from "node:os";
 
 import { expandPath } from "../common/fs";
-import { escapeCommandArg, escapeProxyCommandArg } from "../common/strings";
+import {
+	escapeCommandArg,
+	escapeProxyCommandArg,
+	escapeProxyCommandPath,
+} from "../common/strings";
 import { validateDeploymentUrl } from "../common/validation";
 
 import { getHeaderArgs } from "./headers";
@@ -52,7 +56,13 @@ export function getGlobalShellFlags(
 	validateDeploymentUrl(auth.url);
 	return [
 		escapeCommandArg("--token="),
-		...buildGlobalFlags(configs, auth, escapeCommandArg, escapeProxyCommandArg),
+		...buildGlobalFlags(
+			configs,
+			auth,
+			escapeCommandArg,
+			escapeProxyCommandArg,
+			escapeProxyCommandPath,
+		),
 	];
 }
 
@@ -61,7 +71,7 @@ export function getGlobalFlags(
 	configs: Pick<WorkspaceConfiguration, "get">,
 	auth: CliAuth,
 ): string[] {
-	return buildGlobalFlags(configs, auth, identity, identity);
+	return buildGlobalFlags(configs, auth, identity, identity, identity);
 }
 
 const identity = (s: string) => s;
@@ -88,6 +98,7 @@ function buildGlobalFlags(
 	auth: CliAuth,
 	escUserFlag: (s: string) => string,
 	escValue: (s: string) => string,
+	escPath: (s: string) => string,
 ): string[] {
 	// Escape after stripping so expansion whitespace stays in one shell token.
 	// User flags keep shell expansion (e.g. `$VAR`); the auth values and
@@ -97,7 +108,7 @@ function buildGlobalFlags(
 		auth.store === "extension",
 	).map(escUserFlag);
 	if (auth.store === "extension") {
-		flags.push("--global-config", escValue(auth.configDir));
+		flags.push("--global-config", escPath(auth.configDir));
 	}
 	flags.push("--url", escValue(auth.url));
 	if (auth.useKeyring !== undefined) {

test/unit/common/strings.test.ts

@@ -4,6 +4,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import {
 	escapeCommandArg,
 	escapeProxyCommandArg,
+	escapeProxyCommandPath,
 	escapeShellArg,
 } from "@/common/strings";
 
@@ -123,3 +124,22 @@ describe("escapeProxyCommandArg", () => {
 		expect(escapeProxyCommandArg(value)).toBe(escape(value));
 	});
 });
+
+describe("escapeProxyCommandPath", () => {
+	const platformSpy = vi.spyOn(os, "platform");
+	afterEach(() => platformSpy.mockReset());
+
+	it.each([
+		[
+			"win32",
+			String.raw`C:\Users\John Doe\coder.exe`,
+			'"C:/Users/John Doe/coder.exe"',
+		],
+		["win32", String.raw`d:\a\b`, "d:/a/b"],
+		["win32", String.raw`\\server\share\x`, String.raw`"\\server\share\x"`],
+		["linux", String.raw`C:\x`, String.raw`'C:\x'`],
+	] as const)("on %s writes %j as %s", (platform, value, expected) => {
+		platformSpy.mockReturnValue(platform);
+		expect(escapeProxyCommandPath(value)).toBe(expected);
+	});
+});

test/unit/remote/remote.test.ts

@@ -403,7 +403,10 @@ describe("Remote", () => {
 		// OpenSSH runs the command with `sh -c` on Unix; Win32-OpenSSH passes it
 		// to CreateProcessW, so the program's argv parser splits it.
 		it("reaches the CLI unchanged through this platform's OpenSSH", () => {
-			const configDir = "/Users/me/Library/Application Support/coder";
+			// A drive path on Windows reaches the CLI with `/`.
+			const configDir = isWindows()
+				? String.raw`C:\Users\John Doe\AppData\coder`
+				: "/Users/me/Library/Application Support/coder";
 			const headerCommand = 'echo "X: $TOKEN" "C:\\a b\\" `id`';
 			const pathResolver = new PathResolver("/mock/global", "/mock/log");
 			new MockConfigurationProvider().set("coder.headerCommand", headerCommand);
@@ -435,7 +438,7 @@ describe("Remote", () => {
 			expect(JSON.parse(result.stdout)).toStrictEqual([
 				"--token=",
 				"--global-config",
-				configDir,
+				configDir.replaceAll("\\", "/"),
 				"--url",
 				CLI_AUTH.url,
 				"--header-command",