Merge pull request 'heph-pwa: Login with Authentik (Authorization Code + PKCE)' (#9) from heph-pwa-oidc-login into main

Reviewed-on: #9

crates/hephd/src/auth.rs

@@ -49,6 +49,13 @@ pub trait TokenVerifier: Send + Sync {
     /// Validate `bearer` (the raw token, no `Bearer ` prefix) and return its
     /// claims, or an [`AuthError`].
     fn verify(&self, bearer: &str) -> Result<Claims, AuthError>;
+
+    /// The public OIDC parameters a browser client (the `heph-pwa`) needs to
+    /// start a login: `(issuer, client_id)`. Neither is a secret. `None` for
+    /// non-OIDC verifiers (e.g. test stubs).
+    fn oidc_config(&self) -> Option<(&str, &str)> {
+        None
+    }
 }
 
 /// What an OIDC provider's discovery document tells us (we only need the JWKS).
@@ -156,4 +163,9 @@ impl TokenVerifier for OidcVerifier {
             .map_err(|e| AuthError::Invalid(e.to_string()))?;
         Ok(data.claims)
     }
+
+    fn oidc_config(&self) -> Option<(&str, &str)> {
+        // The audience is the OIDC client id (Authentik sets `aud` to it).
+        Some((&self.issuer, &self.audience))
+    }
 }

crates/hephd/src/sync.rs

@@ -135,6 +135,10 @@ pub fn router_with_web(
         .route("/sync/push", post(push))
         .route("/rpc", post(rpc_call))
         .route_layer(middleware::from_fn_with_state(state.clone(), require_auth))
+        // Unauthenticated: the public OIDC params (issuer + client id) a browser
+        // client reads to start a PKCE login. Added after the auth `route_layer`
+        // so it is NOT gated — the app needs it *before* it has a token.
+        .route("/config", get(config))
         // The static shell is unauthenticated and lives behind the API routes.
         .fallback(serve_static)
         // Outermost: stamp CORS headers on every response and short-circuit the
@@ -174,6 +178,20 @@ async fn cors(request: Request, next: Next) -> AxumResponse {
     response
 }
 
+/// Public OIDC parameters for a browser client (the `heph-pwa`) to start a PKCE
+/// login: `{ "issuer", "client_id" }`. Unauthenticated — neither value is a
+/// secret. Returns an empty object `{}` when the hub runs without OIDC, so the
+/// app can detect that and fall back to a manually pasted token.
+async fn config(State(state): State<HubState>) -> Json<Value> {
+    let body = state
+        .verifier
+        .as_ref()
+        .and_then(|v| v.oidc_config())
+        .map(|(issuer, client_id)| serde_json::json!({ "issuer": issuer, "client_id": client_id }))
+        .unwrap_or_else(|| serde_json::json!({}));
+    Json(body)
+}
+
 /// Serve the PWA shell from `web_root` for any non-API path. Returns 404 when no
 /// `web_root` is configured. Unknown paths fall back to `index.html` so the SPA
 /// can own its own routing. Path traversal (`..`) is rejected.

crates/hephd/tests/web_serve.rs

@@ -12,10 +12,23 @@ use std::thread;
 use std::time::Duration;
 
 use heph_core::{FixedClock, LocalStore};
+use hephd::auth::{AuthError, Claims, TokenVerifier};
 use hephd::sync::{self, SharedStore};
 
 const NOW: i64 = 1_704_067_200_000; // 2024-01-01T00:00:00Z
 
+/// A verifier that never admits a token but advertises OIDC params, so we can
+/// drive the unauthenticated `/config` route without a live IdP.
+struct StubOidc;
+impl TokenVerifier for StubOidc {
+    fn verify(&self, _bearer: &str) -> Result<Claims, AuthError> {
+        Err(AuthError::Missing)
+    }
+    fn oidc_config(&self) -> Option<(&str, &str)> {
+        Some(("https://idp.example/application/o/heph/", "heph"))
+    }
+}
+
 /// One parsed HTTP response: status line code, lowercased headers, and body.
 struct Resp {
     status: u16,
@@ -64,6 +77,15 @@ fn request(addr: &str, method: &str, path: &str) -> Resp {
 /// an ephemeral port; return its `host:port`. The server thread + temp dirs live
 /// for the test's duration.
 fn start(web_root: Option<std::path::PathBuf>) -> String {
+    start_with(None, web_root)
+}
+
+/// As [`start`], but with an explicit token verifier (to exercise the `/config`
+/// route, which reports the verifier's OIDC params).
+fn start_with(
+    verifier: Option<Arc<dyn TokenVerifier>>,
+    web_root: Option<std::path::PathBuf>,
+) -> String {
     let (tx, rx) = mpsc::channel();
     thread::spawn(move || {
         let rt = tokio::runtime::Builder::new_current_thread()
@@ -78,7 +100,7 @@ fn start(web_root: Option<std::path::PathBuf>) -> String {
             let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
             tx.send(listener.local_addr().unwrap()).unwrap();
             let _keep = dir;
-            let app = sync::router_with_web(shared, None, web_root);
+            let app = sync::router_with_web(shared, verifier, web_root);
             axum::serve(listener, app).await.unwrap();
         });
     });
@@ -161,3 +183,31 @@ fn no_web_root_yields_404_for_static_paths() {
     // Even the 404 carries CORS headers (it passed through the layer).
     assert_eq!(resp.header("access-control-allow-origin"), Some("*"));
 }
+
+#[test]
+fn config_is_empty_without_oidc() {
+    let addr = start(None);
+    let resp = request(&addr, "GET", "/config");
+    assert_eq!(resp.status, 200);
+    assert_eq!(resp.body.trim(), "{}");
+}
+
+#[test]
+fn config_reports_oidc_params_unauthenticated() {
+    // Even on an authed hub, /config is reachable without a token (it is added
+    // after the auth layer) and reports the issuer + public client id.
+    let addr = start_with(Some(Arc::new(StubOidc)), None);
+    let resp = request(&addr, "GET", "/config");
+    assert_eq!(resp.status, 200);
+    assert!(
+        resp.body
+            .contains("\"issuer\":\"https://idp.example/application/o/heph/\""),
+        "body was: {}",
+        resp.body
+    );
+    assert!(
+        resp.body.contains("\"client_id\":\"heph\""),
+        "body was: {}",
+        resp.body
+    );
+}

docs/changelog.d/heph-pwa-oidc-login.feature.md

@@ -0,0 +1 @@
+heph-pwa: added a **Login with Authentik** button — a proper browser OIDC sign-in (Authorization Code + PKCE) that replaces the manual bearer-token paste. The hub exposes an unauthenticated `GET /config` (`{issuer, client_id}`) so the app is zero-config when served from the hub; the PWA discovers the IdP endpoints, runs the PKCE redirect, exchanges the code for a token, and silently refreshes it (`offline_access`). The manual token field remains as a fallback. Requires the PWA origin registered as a redirect URI on the Authentik `heph` provider.

docs/how-to/host-heph-pwa.md

@@ -95,16 +95,19 @@ app defaults its hub URL to its own origin.
 1. Ensure the phone is on the tailnet (or can reach the proxy).
 2. Open the hub URL (`https://indri.<tailnet>.ts.net/`) and **Add to Home Screen**.
 3. The app defaults its **Hub URL** to the origin it loaded from — no typing.
-4. **Token:** the hub requires an OIDC bearer token, and the PWA does **not yet
-   implement the in-app device-code login** — paste a token into Settings →
-   Token for now. Obtain one via the device-code flow against the Authentik
-   client (the same flow the CLI uses; e.g. reuse the access token a logged-in
-   spoke cached, or run a one-off device-code grant). Tap **Test** to confirm.
+4. **Sign in:** open **Settings → Login with Authentik**. The app reads the
+   hub's `GET /config` for the issuer + client id (zero-config) and runs an
+   Authorization-Code + PKCE redirect to Authentik; after you approve it lands
+   back on the app, signed in, and silently refreshes the token from then on.
+   (A manual **Bearer token** field remains as a fallback for hubs without
+   OIDC, or for pasting a one-off token.)
 
-> **Known gap / next step:** wire the RFC 8628 device-code flow into the PWA's
-> Settings so login is in-app (open the verification URL, poll for the token,
-> store it, and refresh it) — removing the manual paste. Tracked as follow-up
-> work for `heph-pwa`.
+**Prerequisite — register the PWA redirect URI.** Browser PKCE needs the app's
+origin registered on the Authentik `heph` provider's **Redirect URIs** (Authentik
+also keys token-endpoint CORS off those origins). Add the PWA origin(s) with a
+trailing slash, e.g. `https://heph.ops.eblu.me/` (and `http://localhost:8787/`
+for local dev). In blumeops this is the `redirect_uris` list on the heph
+provider blueprint.
 
 ## Upgrades
 

heph-pwa/src/app.js

@@ -6,6 +6,7 @@
 // rpc.js). Context/KB is read-only here (no nvim editing surface).
 
 import { Client, loadSettings, saveSettings, RpcError } from "./rpc.js";
+import * as oauth from "./oauth.js";
 import { parse as quickParse } from "./quickadd.js";
 import { today, parseDate, toEpochMs } from "./datespec.js";
 import {
@@ -40,7 +41,29 @@ const state = {
   lastUndo: null, // { label, run }
 };
 
-state.client = new Client(state.settings);
+// Build the RPC client from the current settings, wiring an OIDC silent-refresh
+// hook: on a 401 the client calls this to renew the token (oauth.js) and retry
+// once before surfacing the error.
+function makeClient() {
+  return new Client({
+    baseUrl: state.settings.baseUrl,
+    token: state.settings.token,
+    refresh: async () => {
+      const tok = await oauth.ensureFreshToken(true);
+      applyToken(tok || "");
+      return tok;
+    },
+  });
+}
+
+// Adopt `token` as the active bearer: persist it and rebuild the client.
+function applyToken(token) {
+  state.settings.token = token || "";
+  saveSettings(state.settings);
+  state.client = makeClient();
+}
+
+state.client = makeClient();
 
 // --- tiny DOM helper --------------------------------------------------------
 
@@ -692,27 +715,62 @@ function openSettings() {
   const url = h("input", { class: "qa-input", type: "url", placeholder: "https://hub.example.com:8787", value: state.settings.baseUrl, autocomplete: "off", inputmode: "url" });
   const tok = h("input", { class: "qa-input", type: "password", placeholder: "Bearer token (optional)", value: state.settings.token, autocomplete: "off" });
   const test = h("div", { class: "settings-test" });
+  const setTest = (msg, ok) => {
+    test.textContent = msg;
+    test.className = "settings-test" + (ok === true ? " ok" : ok === false ? " bad" : "");
+  };
 
   const save = async () => {
     state.settings.baseUrl = url.value.trim();
     state.settings.token = tok.value.trim();
     saveSettings(state.settings);
-    state.client = new Client(state.settings);
+    state.client = makeClient();
     closeModal();
     reload();
   };
   const check = async () => {
-    test.textContent = "Checking…";
+    setTest("Checking…", null);
     const probe = new Client({ baseUrl: url.value.trim(), token: tok.value.trim() });
     try {
       const v = await probe.call("version", {});
-      test.textContent = `✓ Connected (hephd ${v.version})`;
-      test.className = "settings-test ok";
+      setTest(`✓ Connected (hephd ${v.version})`, true);
     } catch (e) {
-      test.textContent = `✗ ${e.message}`;
-      test.className = "settings-test bad";
+      setTest(`✗ ${e.message}`, false);
     }
   };
+  // Login with Authentik: read the hub's /config for the issuer + client id,
+  // then start the PKCE redirect (this navigates away and returns to init()).
+  const login = async () => {
+    const hub = url.value.trim() || state.settings.baseUrl;
+    if (!hub) return setTest("✗ Set the hub URL first.", false);
+    setTest("Contacting hub…", null);
+    const cfg = await oauth.fetchHubConfig(hub);
+    if (!cfg) {
+      return setTest("✗ Hub has no OIDC (/config) — paste a token, or enable OIDC on the hub.", false);
+    }
+    state.settings.baseUrl = hub;
+    saveSettings(state.settings); // persist before we navigate away
+    try {
+      await oauth.beginLogin(cfg);
+    } catch (e) {
+      setTest(`✗ ${e.message}`, false);
+    }
+  };
+  const logout = () => {
+    oauth.clearAuth();
+    applyToken("");
+    closeModal();
+    reload();
+  };
+
+  const authRow = oauth.loggedIn()
+    ? h(
+        "div",
+        { class: "settings-auth" },
+        h("span", { class: "settings-test ok" }, "✓ Signed in with Authentik"),
+        h("button", { class: "act", onclick: logout }, "Log out"),
+      )
+    : h("button", { class: "qa-add settings-login", onclick: login }, "Login with Authentik");
 
   openModal(
     h(
@@ -721,8 +779,14 @@ function openSettings() {
       h("div", { class: "modal-title" }, "Settings"),
       h("label", { class: "settings-label" }, "Hub URL"),
       url,
-      h("label", { class: "settings-label" }, "Token"),
+      h("label", { class: "settings-label" }, "Sign-in"),
+      authRow,
+      h(
+        "details",
+        { class: "settings-manual" },
+        h("summary", {}, "Or paste a bearer token"),
         tok,
+      ),
       test,
       h(
         "div",
@@ -730,7 +794,7 @@ function openSettings() {
         h("button", { class: "act", onclick: check }, "Test"),
         h("button", { class: "qa-add", onclick: save }, "Save"),
       ),
-      h("div", { class: "settings-hint" }, "The hub is your server-mode hephd. Leave the token blank if the hub runs without OIDC."),
+      h("div", { class: "settings-hint" }, "“Login with Authentik” needs OIDC enabled on the hub. Leave sign-in empty for a hub running without OIDC."),
     ),
   );
 }
@@ -802,6 +866,20 @@ async function init() {
     }
   });
 
+  // OIDC: finish a redirect callback (back from Authentik), or refresh an
+  // existing session, so the first reload() already carries a valid bearer.
+  if (oauth.isCallback()) {
+    try {
+      applyToken(await oauth.completeLogin());
+      toast("Signed in.");
+    } catch (e) {
+      toast(`Sign-in failed: ${e.message}`);
+    }
+  } else if (oauth.loggedIn()) {
+    const tok = await oauth.ensureFreshToken();
+    if (tok) applyToken(tok);
+  }
+
   render();
   reload();
 

heph-pwa/src/oauth.js

@@ -0,0 +1,204 @@
+// Browser OIDC sign-in for the PWA: Authorization Code + PKCE (RFC 7636) against
+// the hub's IdP (Authentik). Unlike the CLI's device-code flow, a browser SPA
+// uses a redirect + PKCE — no client secret, no polling. The resulting access
+// token is the same bearer the hub's OidcVerifier checks (iss / aud=client_id /
+// RS256 / exp), so once signed in the app talks to /rpc exactly as a pasted
+// token would. We also keep a refresh token (offline_access) to renew silently.
+//
+// Zero-config: the hub serves GET /config -> { issuer, client_id }, so the app
+// learns the IdP without the user typing anything when served from the hub.
+
+const AUTH_KEY = "heph-pwa:auth"; // localStorage: { issuer, clientId, access, refresh, expiresAt }
+const PKCE_KEY = "heph-pwa:pkce"; // sessionStorage: in-flight { verifier, state, ... }
+
+// --- persistence ------------------------------------------------------------
+
+export function loadAuth() {
+  try {
+    return JSON.parse(localStorage.getItem(AUTH_KEY) || "null");
+  } catch {
+    return null;
+  }
+}
+function saveAuth(a) {
+  localStorage.setItem(AUTH_KEY, JSON.stringify(a));
+}
+export function clearAuth() {
+  localStorage.removeItem(AUTH_KEY);
+}
+export function loggedIn() {
+  return !!loadAuth();
+}
+
+// --- PKCE helpers -----------------------------------------------------------
+
+function b64url(bytes) {
+  return btoa(String.fromCharCode(...new Uint8Array(bytes)))
+    .replace(/\+/g, "-")
+    .replace(/\//g, "_")
+    .replace(/=+$/, "");
+}
+function randomString(nbytes = 32) {
+  const a = new Uint8Array(nbytes);
+  crypto.getRandomValues(a);
+  return b64url(a);
+}
+async function challengeOf(verifier) {
+  const digest = await crypto.subtle.digest("SHA-256", new TextEncoder().encode(verifier));
+  return b64url(digest);
+}
+
+// The redirect URI is the app's own base directory (query/hash stripped), so it
+// is stable across the login start and the callback. Register this exact value
+// (with trailing slash) on the Authentik provider, e.g. https://heph.ops.eblu.me/.
+function redirectUri() {
+  return new URL(".", location.href).href;
+}
+
+// --- discovery --------------------------------------------------------------
+
+async function discover(issuer) {
+  const url = issuer.replace(/\/+$/, "") + "/.well-known/openid-configuration";
+  const r = await fetch(url);
+  if (!r.ok) throw new Error(`OIDC discovery failed (HTTP ${r.status}).`);
+  const d = await r.json();
+  if (!d.authorization_endpoint || !d.token_endpoint) {
+    throw new Error("OIDC discovery is missing authorization/token endpoints.");
+  }
+  return { authorize: d.authorization_endpoint, token: d.token_endpoint };
+}
+
+/** Read the hub's public OIDC params. Returns { issuer, clientId } or null. */
+export async function fetchHubConfig(baseUrl) {
+  try {
+    const r = await fetch(baseUrl.replace(/\/+$/, "") + "/config");
+    if (!r.ok) return null;
+    const d = await r.json();
+    if (!d.issuer || !d.client_id) return null;
+    return { issuer: d.issuer, clientId: d.client_id };
+  } catch {
+    return null;
+  }
+}
+
+// --- login (redirect away) --------------------------------------------------
+
+/** Begin a PKCE login: stash the verifier+state and redirect to the IdP. */
+export async function beginLogin({ issuer, clientId }) {
+  const { authorize } = await discover(issuer);
+  const verifier = randomString(48);
+  const state = randomString(16);
+  const redirect_uri = redirectUri();
+  sessionStorage.setItem(
+    PKCE_KEY,
+    JSON.stringify({ verifier, state, issuer, clientId, redirect_uri }),
+  );
+  const params = new URLSearchParams({
+    response_type: "code",
+    client_id: clientId,
+    redirect_uri,
+    scope: "openid offline_access",
+    state,
+    code_challenge: await challengeOf(verifier),
+    code_challenge_method: "S256",
+  });
+  location.assign(`${authorize}?${params}`);
+}
+
+// --- callback (back from the IdP) -------------------------------------------
+
+/** True when the current URL is an OAuth redirect callback. */
+export function isCallback() {
+  const p = new URLSearchParams(location.search);
+  return (p.has("code") && p.has("state")) || p.has("error");
+}
+
+/** Exchange the callback code for tokens. Always cleans the URL. Returns the
+ *  access token on success; throws on failure. */
+export async function completeLogin() {
+  const p = new URLSearchParams(location.search);
+  const cleanUrl = () => history.replaceState(null, "", redirectUri());
+  let pkce = null;
+  try {
+    pkce = JSON.parse(sessionStorage.getItem(PKCE_KEY) || "null");
+  } catch {
+    pkce = null;
+  }
+  sessionStorage.removeItem(PKCE_KEY);
+
+  if (p.get("error")) {
+    cleanUrl();
+    throw new Error(p.get("error_description") || p.get("error"));
+  }
+  if (!pkce || pkce.state !== p.get("state")) {
+    cleanUrl();
+    throw new Error("Login state mismatch — please try again.");
+  }
+
+  const { token } = await discover(pkce.issuer);
+  const body = new URLSearchParams({
+    grant_type: "authorization_code",
+    code: p.get("code"),
+    client_id: pkce.clientId,
+    redirect_uri: pkce.redirect_uri,
+    code_verifier: pkce.verifier,
+  });
+  const r = await fetch(token, {
+    method: "POST",
+    headers: { "Content-Type": "application/x-www-form-urlencoded" },
+    body,
+  });
+  cleanUrl();
+  if (!r.ok) throw new Error(`Token exchange failed (HTTP ${r.status}).`);
+  const t = await r.json();
+  saveAuth({
+    issuer: pkce.issuer,
+    clientId: pkce.clientId,
+    access: t.access_token,
+    refresh: t.refresh_token || null,
+    expiresAt: Date.now() + (t.expires_in || 3600) * 1000,
+  });
+  return t.access_token;
+}
+
+// --- token lifecycle --------------------------------------------------------
+
+/** Return a usable access token, refreshing if it is near expiry (or `force`).
+ *  Returns null when not logged in or when a refresh fails (caller re-prompts). */
+export async function ensureFreshToken(force = false) {
+  const a = loadAuth();
+  if (!a) return null;
+  const stillFresh = a.expiresAt - Date.now() > 60_000;
+  if (!force && stillFresh) return a.access;
+  if (!a.refresh) return force ? null : a.access;
+  try {
+    const { token } = await discover(a.issuer);
+    const body = new URLSearchParams({
+      grant_type: "refresh_token",
+      refresh_token: a.refresh,
+      client_id: a.clientId,
+    });
+    const r = await fetch(token, {
+      method: "POST",
+      headers: { "Content-Type": "application/x-www-form-urlencoded" },
+      body,
+    });
+    if (!r.ok) {
+      // Refresh token rejected (expired/revoked) — drop the session so the UI
+      // shows "signed out" and the user can log in again.
+      clearAuth();
+      return null;
+    }
+    const t = await r.json();
+    saveAuth({
+      ...a,
+      access: t.access_token,
+      refresh: t.refresh_token || a.refresh,
+      expiresAt: Date.now() + (t.expires_in || 3600) * 1000,
+    });
+    return t.access_token;
+  } catch {
+    // Network blip — keep the (possibly stale) token; the RPC layer will retry.
+    return a.access;
+  }
+}

heph-pwa/src/rpc.js

@@ -49,8 +49,10 @@ export class Client {
     return !!this.settings.baseUrl;
   }
 
-  /** Low-level call: returns the `result` value, or throws RpcError. */
-  async call(method, params = {}) {
+  /** Low-level call: returns the `result` value, or throws RpcError. On a 401,
+   *  tries the optional `settings.refresh()` hook once (OIDC silent refresh) and
+   *  retries before surfacing the error. */
+  async call(method, params = {}, _retried = false) {
     if (!this.configured) {
       throw new RpcError("No hub configured — open Settings and set the hub URL.", 0);
     }
@@ -68,7 +70,16 @@ export class Client {
     } catch (e) {
       throw new RpcError(`Cannot reach hub at ${base} (${e.message}).`, 0);
     }
-    if (resp.status === 401) throw new RpcError("Unauthorized — set or refresh your token.", 401);
+    if (resp.status === 401) {
+      if (!_retried && typeof this.settings.refresh === "function") {
+        const fresh = await this.settings.refresh();
+        if (fresh) {
+          this.settings.token = fresh;
+          return this.call(method, params, true);
+        }
+      }
+      throw new RpcError("Unauthorized — sign in again (Settings).", 401);
+    }
     if (resp.status === 403) throw new RpcError("Forbidden — this token does not own the hub.", 403);
     if (!resp.ok) throw new RpcError(`Hub returned HTTP ${resp.status}.`, resp.status);
 

heph-pwa/styles.css

@@ -435,6 +435,26 @@ body {
   font-size: 12px;
   color: var(--fg-dim);
 }
+.settings-login {
+  align-self: stretch;
+}
+.settings-auth {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+}
+.settings-auth .settings-test {
+  flex: 1;
+}
+.settings-manual > summary {
+  font-size: 13px;
+  color: var(--fg-dim);
+  cursor: pointer;
+  margin-bottom: 6px;
+}
+.settings-manual[open] > summary {
+  margin-bottom: 10px;
+}
 
 /* --- Search --- */
 .search-pane {

heph-pwa/sw.js

@@ -1,7 +1,7 @@
 // Service worker: cache the app shell so heph launches offline. Data is never
 // cached — every /rpc call must hit the live hub (and POSTs aren't cacheable
 // anyway). Bump CACHE when shell assets change to evict the old set.
-const CACHE = "heph-pwa-v3";
+const CACHE = "heph-pwa-v4";
 const SHELL = [
   "./",
   "./index.html",
@@ -9,6 +9,7 @@ const SHELL = [
   "./manifest.webmanifest",
   "./src/app.js",
   "./src/rpc.js",
+  "./src/oauth.js",
   "./src/quickadd.js",
   "./src/datespec.js",
   "./src/fmt.js",
@@ -31,8 +32,10 @@ self.addEventListener("activate", (e) => {
 self.addEventListener("fetch", (e) => {
   const req = e.request;
   // Only cache same-origin GETs (the shell). Everything else (RPC, cross-origin)
-  // goes straight to the network.
-  if (req.method !== "GET" || new URL(req.url).origin !== self.location.origin) {
+  // goes straight to the network. Skip URLs with a query string too, so the OAuth
+  // redirect callback (`/?code=…&state=…`) is never cached or served from cache.
+  const u = new URL(req.url);
+  if (req.method !== "GET" || u.origin !== self.location.origin || u.search) {
     return;
   }
   e.respondWith(