diff --git a/packages/web/package.json b/packages/web/package.json
index 946ee2a..8309261 100644
--- a/packages/web/package.json
+++ b/packages/web/package.json
@@ -9,7 +9,7 @@
 		"preview": "vite preview",
 		"lint": "biome check src/",
 		"lint:fix": "biome check --write src/",
-		"test": "vitest run --passWithNoTests",
+		"test": "vitest run --passWithNoTests && node scripts/test-dev-proxy.mjs",
 		"test:coverage": "vitest run --coverage",
 		"test:e2e": "playwright test",
 		"generate:api": "openapi-typescript openapi.json -o src/api/schema.d.ts"
diff --git a/packages/web/scripts/test-dev-proxy.mjs b/packages/web/scripts/test-dev-proxy.mjs
new file mode 100644
index 0000000..80f9c32
--- /dev/null
+++ b/packages/web/scripts/test-dev-proxy.mjs
@@ -0,0 +1,41 @@
+// Run: node packages/web/scripts/test-dev-proxy.mjs
+import assert from "node:assert/strict";
+import { once } from "node:events";
+import { createServer as createHttpServer } from "node:http";
+import { test } from "node:test";
+import { fileURLToPath } from "node:url";
+import { createServer, loadConfigFromFile } from "vite";
+
+const root = fileURLToPath(new URL("../", import.meta.url));
+const loaded = await loadConfigFromFile(
+	{ command: "serve", mode: "development" },
+	`${root}vite.config.ts`,
+);
+const proxy = loaded.config.plugins.find((plugin) => plugin.name === "honcho-api-proxy");
+
+for (const base of ["/", "/honcho/"]) {
+	test(`dev proxy forwards requests under ${base}`, async () => {
+		const upstream = createHttpServer((req, res) => res.end(req.url));
+		upstream.listen(0, "127.0.0.1");
+		await once(upstream, "listening");
+		const vite = await createServer({
+			configFile: false,
+			root,
+			base,
+			plugins: [proxy],
+			optimizeDeps: { noDiscovery: true, include: [] },
+			server: { host: "127.0.0.1", port: 0, strictPort: false },
+		});
+		try {
+			await vite.listen();
+			const response = await fetch(
+				`http://127.0.0.1:${vite.httpServer.address().port}${base}api/v3/workspaces/list?limit=1`,
+				{ headers: { "X-Honcho-Upstream": `http://127.0.0.1:${upstream.address().port}` } },
+			);
+			assert.equal(await response.text(), "/v3/workspaces/list?limit=1");
+		} finally {
+			await vite.close();
+			await new Promise((resolve) => upstream.close(resolve));
+		}
+	});
+}
diff --git a/packages/web/vite.config.ts b/packages/web/vite.config.ts
index 4622347..760c815 100644
--- a/packages/web/vite.config.ts
+++ b/packages/web/vite.config.ts
@@ -34,7 +34,7 @@ function honchoApiProxy(): Plugin {
 	return {
 		name: "honcho-api-proxy",
 		configureServer(server) {
-			server.middlewares.use("/api", async (req, res) => {
+			server.middlewares.use(`${server.config.base.replace(/\/+$/, "")}/api`, async (req, res) => {
 				const upstream = req.headers[HEADER];
 				if (typeof upstream !== "string" || upstream.trim() === "") {
 					res.statusCode = 421;