diff --git a/packages/server/src/process.ts b/packages/server/src/process.ts
index c3b01b0140..d1d7020180 100644
--- a/packages/server/src/process.ts
+++ b/packages/server/src/process.ts
@@ -10,6 +10,7 @@ import { HttpMiddleware, HttpRouter, HttpServer, HttpServerRequest, HttpServerRe
 import { randomUUID } from "node:crypto"
 import { createServer } from "node:http"
 import { ServerAuth } from "./auth"
+import { isAllowedCorsOrigin } from "./cors"
 import { authorizedRequest } from "./middleware/authorization"
 import { withoutParentSpan } from "./request-tracing"
 import { createRoutes } from "./routes"
@@ -48,7 +49,12 @@ export const start = Effect.fn("ServerProcess.start")(function* <E, R>(
   const application = yield* Ref.make(Option.none<App>())
   // Request fibers may continue inbound trace context, but must not inherit the server startup parent.
   yield* bound.http
-    .serve(dispatch(password, status, application, shutdown), HttpMiddleware.logger)
+    .serve(
+      dispatch(password, status, application, shutdown).pipe(
+        HttpMiddleware.cors({ allowedOrigins: isAllowedCorsOrigin, maxAge: 86_400 }),
+      ),
+      HttpMiddleware.logger,
+    )
     .pipe(withoutParentSpan)
   if (lifecycle)
     yield* lifecycle.onListen(bound.http.address, Deferred.succeed(shutdown, undefined).pipe(Effect.asVoid)).pipe(
diff --git a/packages/server/test/process.test.ts b/packages/server/test/process.test.ts
new file mode 100644
index 0000000000..eeec517e04
--- /dev/null
+++ b/packages/server/test/process.test.ts
@@ -0,0 +1,42 @@
+import { expect } from "bun:test"
+import { Effect } from "effect"
+import { HttpServer } from "effect/unstable/http"
+import { it } from "../../core/test/lib/effect"
+import { ServerProcess } from "../src/process"
+
+it.live("allows browser preflight requests without credentials", () =>
+  Effect.gen(function* () {
+    const server = yield* ServerProcess.start<never, never>({
+      hostname: "127.0.0.1",
+      port: 0,
+      password: "secret",
+      database: { path: ":memory:" },
+    })
+    const response = yield* Effect.promise(() =>
+      fetch(new URL("/api/health", HttpServer.formatAddress(server.address)), {
+        method: "OPTIONS",
+        headers: {
+          origin: "http://localhost:3000",
+          "access-control-request-method": "GET",
+          "access-control-request-headers": "authorization",
+        },
+      }),
+    )
+
+    expect(response.status).toBe(204)
+    expect(response.headers.get("access-control-allow-origin")).toBe("http://localhost:3000")
+    expect(response.headers.get("access-control-allow-headers")).toBe("authorization")
+
+    const health = yield* Effect.promise(() =>
+      fetch(new URL("/api/health", HttpServer.formatAddress(server.address)), {
+        headers: {
+          authorization: `Basic ${btoa("opencode:secret")}`,
+          origin: "http://localhost:3000",
+        },
+      }),
+    )
+
+    expect(health.status).toBe(200)
+    expect(health.headers.get("access-control-allow-origin")).toBe("http://localhost:3000")
+  }),
+)