diff --git a/packages/viewer/src/server.ts b/packages/viewer/src/server.ts
index 2d4495d..97d4ed0 100644
--- a/packages/viewer/src/server.ts
+++ b/packages/viewer/src/server.ts
@@ -374,6 +374,16 @@ export function createViewerServer(opts: ServerOpts) {
     if (parts[0] !== "w" || !parts[1]) return send(res, 404, "not found");
     const wsid = parts[1];
     if (wsid === SHARES_WSID || wsid === TEMPLATES_WSID) return send(res, 404, "not found"); // reserved store wsids, never servable
+    // Trailing slash matters: index.html's relative assets (viewer.js/style.css) must resolve under
+    // /w/<wsid>/ — without it the browser fetches /w/viewer.js, which the SPA fallback answers with
+    // HTML, so the module load fails and the page is blank. Redirect the bare form so a hand-typed/
+    // clicked link without the slash still works (mirrors the /s/<token> redirect above). The URL
+    // fragment (#scope) is preserved by the browser across a fragment-less redirect.
+    if (parts.length === 2 && !url.pathname.endsWith("/")) {
+      res.writeHead(302, { location: `/w/${wsid}/${url.search}` });
+      res.end();
+      return;
+    }
     const action = parts[2] ?? "";
 
     // The built-in demo workspace is READ-ONLY and has no agent: every mutating endpoint is a POST
diff --git a/packages/viewer/test/server-static.test.ts b/packages/viewer/test/server-static.test.ts
index cd5e08a..ffe1db9 100644
--- a/packages/viewer/test/server-static.test.ts
+++ b/packages/viewer/test/server-static.test.ts
@@ -69,6 +69,23 @@ describe("static serving", () => {
     expect(await r.text()).toContain("VIEWER_INDEX");
   });
 
+  // A workspace URL without the trailing slash must redirect to the slashed form. Otherwise the
+  // browser resolves index.html's relative <script src="viewer.js"> against /w/ — fetching
+  // /w/viewer.js, which the SPA fallback answers with HTML, so the module load fails and the page
+  // is blank. (The /s/<token> share path already does this; /w/<wsid> must match.)
+  it("redirects /w/<wsid> (no trailing slash) to /w/<wsid>/", async () => {
+    const r = await fetch(`${base}/w/ws1`, { redirect: "manual" });
+    expect(r.status).toBe(302);
+    expect(r.headers.get("location")).toBe("/w/ws1/");
+  });
+
+  it("does not redirect the slashed workspace root or asset paths", async () => {
+    const root = await fetch(`${base}/w/ws1/`, { redirect: "manual" });
+    expect(root.status).toBe(200);
+    const asset = await fetch(`${base}/w/ws1/viewer-ABC123.js`, { redirect: "manual" });
+    expect(asset.status).toBe(200);
+  });
+
   it("does not serve files outside publicDir via traversal", async () => {
     const r = await fetch(`${base}/w/ws1/..%2f..%2fpackage.json`);
     expect(await r.text()).not.toContain("termchart-viewer");