From 75978cf188c510c726144dcfec65a5b3ff48e29c Mon Sep 17 00:00:00 2001
From: Bohdan Triapitsyn <artmore@protonmail.com>
Date: Mon, 10 Aug 2026 20:23:45 +0300
Subject: [PATCH] fix(mcp): reliable OAuth across runtimes and honest
 pre-restart UI
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

MCP authorization was broken in several stacked ways. The browser return
leg landed on the SPA behind the auth gate, so the system browser saw a
login page instead of finishing; the pending-context store silently
saved nothing because its route had no JSON body parser; and the
callback-URL config write started deferring behind Apply & Restart, so
authorization ran against a runtime without the URL and dead-ended on
OpenCode's loopback listener.

The return leg is now completed entirely server-side by an
unauthenticated GET /mcp/oauth/callback that only forwards a code whose
state matches a parked context. Desktop with the local server and VS
Code switch to OpenCode's native flow over its fixed loopback port —
no config writes or restarts at all, with a one-time cleanup of the
previously written callback URL — and its completion signal drives the
page instead of blind status polling. Remote, hosted-web, and mobile
keep the server-callback flow, applying a queued callback-URL write
immediately since authorization cannot wait for a manual restart.

Also: a server queued behind Apply & Restart now shows an Awaiting
restart badge and explanation instead of connect/reauthorize buttons
that can only fail, and Reauthorize is offered only while the server is
actually connected.
---
 .../chat/work-status/WorkStatusMcpSection.tsx |   2 -
 .../ui/src/components/mcp/McpDropdown.tsx     |   2 -
 .../src/components/sections/mcp/McpPage.tsx   |  87 ++++++++++--
 .../sections/mcp/startMcpAuthorization.ts     | 103 +++++++++++++-
 .../ui/src/lib/i18n/messages/de.settings.ts   |   2 +
 .../ui/src/lib/i18n/messages/en.settings.ts   |   2 +
 .../ui/src/lib/i18n/messages/es.settings.ts   |   2 +
 .../ui/src/lib/i18n/messages/fr.settings.ts   |   2 +
 .../ui/src/lib/i18n/messages/ja.settings.ts   |   2 +
 .../ui/src/lib/i18n/messages/ko.settings.ts   |   2 +
 .../ui/src/lib/i18n/messages/pl.settings.ts   |   2 +
 .../src/lib/i18n/messages/pt-BR.settings.ts   |   2 +
 .../ui/src/lib/i18n/messages/uk.settings.ts   |   2 +
 .../src/lib/i18n/messages/zh-CN.settings.ts   |   2 +
 .../src/lib/i18n/messages/zh-TW.settings.ts   |   2 +
 packages/ui/src/stores/useMcpStore.ts         |  28 ++++
 .../lib/opencode/mcp-oauth-callback.test.js   | 111 +++++++++++++++
 packages/web/server/lib/opencode/proxy.js     |   4 +
 packages/web/server/lib/opencode/routes.js    | 129 +++++++++++++++++-
 19 files changed, 466 insertions(+), 22 deletions(-)
 create mode 100644 packages/web/server/lib/opencode/mcp-oauth-callback.test.js

diff --git a/packages/ui/src/components/chat/work-status/WorkStatusMcpSection.tsx b/packages/ui/src/components/chat/work-status/WorkStatusMcpSection.tsx
index 4c69249b..fcb68c75 100644
--- a/packages/ui/src/components/chat/work-status/WorkStatusMcpSection.tsx
+++ b/packages/ui/src/components/chat/work-status/WorkStatusMcpSection.tsx
@@ -5,7 +5,6 @@ import { useMcpStore } from '@/stores/useMcpStore';
 import { McpIcon } from '@/components/icons/McpIcon';
 import { runBackgroundNetworkTask } from '@/lib/background-network';
 import { toast } from 'sonner';
-import { isVSCodeRuntime } from '@/lib/desktop';
 import { startMcpAuthorization } from '@/components/sections/mcp/startMcpAuthorization';
 import { WorkStatusCollapsibleSection, WorkStatusRow, WorkStatusRowAction } from './WorkStatusPrimitives';
 import { useReportWorkStatusPresence } from './presenceContext';
@@ -54,7 +53,6 @@ export const WorkStatusMcpSection: React.FC<Props> = ({ directory }) => {
       const { opened } = await startMcpAuthorization({
         name,
         directory,
-        skipRedirectUriBootstrap: isVSCodeRuntime(),
       });
       if (!opened) {
         toast.error(t('chat.workStatus.mcp.authorizeOpenFailed'));
diff --git a/packages/ui/src/components/mcp/McpDropdown.tsx b/packages/ui/src/components/mcp/McpDropdown.tsx
index 75134f3d..8c84ffdb 100644
--- a/packages/ui/src/components/mcp/McpDropdown.tsx
+++ b/packages/ui/src/components/mcp/McpDropdown.tsx
@@ -22,7 +22,6 @@ import { McpIcon } from '@/components/icons/McpIcon';
 import { Icon } from "@/components/icon/Icon";
 import { useI18n } from '@/lib/i18n';
 import { toast } from 'sonner';
-import { isVSCodeRuntime } from '@/lib/desktop';
 import { startMcpAuthorization } from '@/components/sections/mcp/startMcpAuthorization';
 
 const statusTooltip = (
@@ -211,7 +210,6 @@ export const McpDropdownContent: React.FC<McpDropdownContentProps> = ({ active,
                       const { opened } = await startMcpAuthorization({
                         name: serverName,
                         directory,
-                        skipRedirectUriBootstrap: isVSCodeRuntime(),
                       });
                       if (!opened) {
                         toast.error(t('mcpDropdown.toast.authorizeOpenFailed'));
diff --git a/packages/ui/src/components/sections/mcp/McpPage.tsx b/packages/ui/src/components/sections/mcp/McpPage.tsx
index 14e41930..96409af2 100644
--- a/packages/ui/src/components/sections/mcp/McpPage.tsx
+++ b/packages/ui/src/components/sections/mcp/McpPage.tsx
@@ -18,6 +18,7 @@ import {
   applyImportedMcpToDraft,
 } from './mcpImport';
 import { useMcpStore } from '@/stores/useMcpStore';
+import { usePendingOpenCodeRestartStore } from '@/stores/usePendingOpenCodeRestartStore';
 import { useDirectoryStore } from '@/stores/useDirectoryStore';
 import { runtimeFetch } from '@/lib/runtime-fetch';
 import { cn } from '@/lib/utils';
@@ -439,6 +440,7 @@ const StatusBadge: React.FC<{
     failed: { text: 'text-[var(--status-error)]', bg: 'bg-[var(--status-error)]/10' },
     needs_auth: { text: 'text-[var(--status-warning)]', bg: 'bg-[var(--status-warning)]/10' },
     needs_client_registration: { text: 'text-[var(--status-warning)]', bg: 'bg-[var(--status-warning)]/10' },
+    awaiting_restart: { text: 'text-[var(--status-warning)]', bg: 'bg-[var(--status-warning)]/10' },
   };
 
   const colors = colorClassMap[status] ?? { text: 'text-muted-foreground', bg: '' };
@@ -584,6 +586,7 @@ export const McpPage: React.FC = () => {
   const completeAuthMcp = useMcpStore((state) => state.completeAuth);
   const clearAuthMcp = useMcpStore((state) => state.clearAuth);
   const testConnectionMcp = useMcpStore((state) => state.testConnection);
+  const pendingRestartChanges = usePendingOpenCodeRestartStore((state) => state.changes);
 
   const selectedServer = selectedMcpName ? getMcpByName(selectedMcpName) : null;
   const isNewServer = Boolean(mcpDraft && mcpDraft.name === selectedMcpName && !selectedServer);
@@ -1032,15 +1035,40 @@ export const McpPage: React.FC = () => {
       // One implementation for every surface that can authorise; the page
       // used to own this flow while the dropdown and the work-status panel
       // called plain `connect`, which cannot start OAuth at all.
-      const { authorizationUrl: nextAuthUrl, opened } = await startMcpAuthorization({
+      const { authorizationUrl: nextAuthUrl, opened, nativeFlow, completion } = await startMcpAuthorization({
         name: selectedMcpName,
         directory: currentDirectory,
-        // Only VS Code keeps OpenCode's own redirect. Skipping whenever some
-        // value was stored left a stale one — a dead loopback port from an
-        // earlier launch — unrepairable from this page; the bootstrap already
-        // rewrites nothing when the stored value is right.
-        skipRedirectUriBootstrap: isVSCodeAuthRuntime,
       });
+
+      if (nativeFlow) {
+        // OpenCode opened the browser and completes the flow itself; there is
+        // no URL or state to track. The completion promise is the authoritative
+        // end signal — status polling alone cannot tell a finished
+        // reauthorization from the still-connected state it started in.
+        if (runtimeActionKeyRef.current !== actionKey) return;
+        setAuthUrl(null);
+        setAuthStateKey(null);
+        setIsAuthPolling(true);
+        authPollAttemptsRef.current = 0;
+        toast.message(t('settings.mcp.page.toast.completeAuthorizationInBrowser'));
+        completion
+          ?.then(() => {
+            if (runtimeActionKeyRef.current !== actionKey) return;
+            setIsAuthPolling(false);
+            authPollAttemptsRef.current = 0;
+            authPollStartsFromNeedsAuthRef.current = false;
+            toast.success(t('settings.mcp.page.toast.authorizationCompleted'));
+          })
+          .catch((completionError) => {
+            if (runtimeActionKeyRef.current !== actionKey) return;
+            setIsAuthPolling(false);
+            authPollAttemptsRef.current = 0;
+            authPollStartsFromNeedsAuthRef.current = false;
+            toast.error(normalizeMcpAuthErrorMessage(completionError, t('settings.mcp.page.toast.authorizationFailed'), tUnsafe));
+          });
+        return;
+      }
+
       const stateKey = parseMcpOAuthCallbackStateKey(new URL(nextAuthUrl).searchParams);
       queuedStateKey = stateKey;
 
@@ -1269,6 +1297,12 @@ export const McpPage: React.FC = () => {
   const runtimeStatus = mcpStatus[selectedMcpName];
   const runtimeDiagnostic = selectedMcpName ? mcpDiagnostics[selectedMcpName] : undefined;
   const effectiveRuntimeStatus = runtimeStatus ?? runtimeDiagnostic;
+  // Saved into the config but queued behind Apply & Restart: OpenCode does not
+  // know this server yet, so every runtime action (connect, authorize, clear
+  // auth) can only fail with "server not found". The page says that instead of
+  // offering the buttons.
+  const isAwaitingRestart = !isNewServer && !effectiveRuntimeStatus
+    && pendingRestartChanges.some((change) => change.scope === 'mcp' && change.id.startsWith(`mcp:${selectedMcpName}:`));
   const isConnected = runtimeStatus?.status === 'connected';
   const needsAuthorization = runtimeStatus?.status === 'needs_auth' || runtimeStatus?.status === 'needs_client_registration';
   // Must be the very URI `startMcpAuthorization` writes into the config, not a
@@ -1305,6 +1339,8 @@ export const McpPage: React.FC = () => {
         return t('settings.mcp.page.status.label.needsAuth');
       case 'needs_client_registration':
         return t('settings.mcp.page.status.label.needsRegistration');
+      case 'awaiting_restart':
+        return t('settings.mcp.page.status.label.awaitingRestart');
       default:
         return status;
     }
@@ -1315,12 +1351,17 @@ export const McpPage: React.FC = () => {
       <SettingsPageLayout
         title={isNewServer ? t('settings.mcp.page.header.newServer') : selectedMcpName}
         titleAccessory={!isNewServer ? (
-          <StatusBadge status={effectiveRuntimeStatus?.status} enabled={enabled} getStatusLabel={getStatusLabel} variant="pill" />
+          <StatusBadge
+            status={isAwaitingRestart ? 'awaiting_restart' : effectiveRuntimeStatus?.status}
+            enabled={enabled}
+            getStatusLabel={getStatusLabel}
+            variant="pill"
+          />
         ) : undefined}
         description={isNewServer
           ? t('settings.mcp.page.header.configureNewServer')
           : t('settings.mcp.page.header.transport', { type: mcpType === 'local' ? t('settings.mcp.page.transport.local') : t('settings.mcp.page.transport.remote') })}
-        headerEnd={!isNewServer ? (
+        headerEnd={!isNewServer && !isAwaitingRestart ? (
           <div className="flex flex-wrap items-center gap-2">
           <Button
             variant={isConnected ? 'outline' : 'default'}
@@ -1340,11 +1381,15 @@ export const McpPage: React.FC = () => {
                 onClick={() => void handleStartAuthorization()}
                 disabled={isAuthorizing || !enabled}
               >
+                {/* "Reauthorize" only once a working authorization exists (the
+                    server is connected); every other state — needs_auth,
+                    failed, still unknown — reads "Authorize" so the label does
+                    not imply stored credentials that may not be there. */}
                 {isAuthorizing
                   ? t('settings.mcp.page.actions.starting')
-                  : needsAuthorization
-                    ? t('settings.mcp.page.actions.authorize')
-                    : t('settings.mcp.page.actions.reauthorize')}
+                  : isConnected
+                    ? t('settings.mcp.page.actions.reauthorize')
+                    : t('settings.mcp.page.actions.authorize')}
               </Button>
               <Button
                 variant="ghost"
@@ -1375,8 +1420,26 @@ export const McpPage: React.FC = () => {
 
 
 
+        {/* Saved but queued behind Apply & Restart: dynamic status the user
+            must see, or the missing action buttons read as a broken page. */}
+        {isAwaitingRestart && (
+          <SettingsSection divider={false}>
+            <div className="rounded-lg border p-3 border-[var(--status-warning-border)] bg-[var(--status-warning-background)]">
+              <div className="min-w-0 space-y-1">
+                <div className="flex flex-wrap items-center gap-x-2 gap-y-1">
+                  <span className={SETTINGS_FIELD_LABEL_CLASS}>{t('settings.mcp.page.status.runtimeStatus')}</span>
+                  <StatusBadge status="awaiting_restart" enabled={enabled} getStatusLabel={getStatusLabel} />
+                </div>
+                <p className="typography-meta text-muted-foreground">
+                  {t('settings.mcp.page.status.description.awaitingRestart')}
+                </p>
+              </div>
+            </div>
+          </SettingsSection>
+        )}
+
         {/* Runtime Status - Simplified for connected, expanded for errors */}
-        {!isNewServer && shouldShowFullStatusCard(effectiveRuntimeStatus?.status, authUrl, needsAuthorization, isAuthPolling) && (
+        {!isNewServer && !isAwaitingRestart && shouldShowFullStatusCard(effectiveRuntimeStatus?.status, authUrl, needsAuthorization, isAuthPolling) && (
           <SettingsSection divider={false}>
             <div className={cn('rounded-lg border p-3', statusCardClass(effectiveRuntimeStatus?.status))}>
               <div className="space-y-4">
diff --git a/packages/ui/src/components/sections/mcp/startMcpAuthorization.ts b/packages/ui/src/components/sections/mcp/startMcpAuthorization.ts
index 62073752..512f9d92 100644
--- a/packages/ui/src/components/sections/mcp/startMcpAuthorization.ts
+++ b/packages/ui/src/components/sections/mcp/startMcpAuthorization.ts
@@ -1,7 +1,8 @@
 import { runtimeFetch } from '@/lib/runtime-fetch';
-import { getRuntimeApiBaseUrl } from '@/lib/runtime-switch';
+import { applyPendingOpenCodeRestart } from '@/lib/opencode/deferredRestart';
+import { getRuntimeApiBaseUrl, getRuntimeKey } from '@/lib/runtime-switch';
 import { openExternalUrl } from '@/lib/url';
-import { focusDesktopWindow, isDesktopShell } from '@/lib/desktop';
+import { focusDesktopWindow, isDesktopShell, isVSCodeRuntime } from '@/lib/desktop';
 import { useMcpConfigStore } from '@/stores/useMcpConfigStore';
 import { useMcpStore } from '@/stores/useMcpStore';
 import { MCP_OAUTH_CALLBACK_PATH, parseMcpOAuthCallbackStateKey } from './mcpOAuth';
@@ -32,6 +33,20 @@ type McpAuthorizationStart = {
   authorizationUrl: string;
   /** False when the runtime refused to open a browser; the caller then offers a manual paste. */
   opened: boolean;
+  /**
+   * True when OpenCode runs the whole flow itself over its fixed loopback
+   * listener: it opened the browser, waits for the callback, and exchanges the
+   * code. There is no URL to display and no state to correlate — callers watch
+   * runtime status until it turns `connected`.
+   */
+  nativeFlow?: boolean;
+  /**
+   * Native flow only: resolves when OpenCode finishes the whole exchange (or
+   * rejects when it fails) — the precise "authorization is over" signal, since
+   * runtime status alone cannot distinguish a completed reauthorization from
+   * the still-connected state it started in.
+   */
+  completion?: Promise<void>;
 };
 
 class McpAuthorizationError extends Error {}
@@ -105,6 +120,46 @@ const clearPendingContext = async (state: string | null): Promise<void> => {
     .catch(() => undefined);
 };
 
+/**
+ * One-time migration for the native desktop flow: earlier versions wrote this
+ * app's per-launch callback URL into the server's config, and OpenCode derives
+ * its listener from that field — pointed at OUR port, it either fails to bind
+ * or the callback lands on a flow that never registered it. Clearing the field
+ * returns OpenCode to its fixed default port. Applied immediately when the
+ * write gets queued behind Apply & Restart, for the same reason as the
+ * callback-URL write below: authorization runs against the live runtime.
+ */
+const clearCustomRedirectUriForNativeFlow = async (name: string): Promise<void> => {
+  if (!useMcpConfigStore.getState().getMcpByName(name)) {
+    await useMcpConfigStore.getState().loadMcpConfigs();
+  }
+  const configStore = useMcpConfigStore.getState();
+  const existing = configStore.getMcpByName(name);
+  const currentOAuth = existing && 'oauth' in existing && existing.oauth ? existing.oauth : null;
+  if (!existing || !currentOAuth?.redirectUri) return;
+
+  const saved = await configStore.updateMcp(name, {
+    oauthEnabled: true,
+    oauthClientId: currentOAuth.clientId ?? '',
+    oauthClientSecret: currentOAuth.clientSecret ?? '',
+    oauthScope: currentOAuth.scope ?? '',
+    oauthRedirectUri: '',
+  });
+  if (!saved.ok) {
+    throw new McpAuthorizationError(saved.message || 'Failed to reset the authorization callback URL');
+  }
+  if (saved.restartDeferred) {
+    const applied = await applyPendingOpenCodeRestart();
+    if (!applied.ok) {
+      throw new McpAuthorizationError(
+        applied.requiresManualRestart
+          ? 'The callback settings changed, but OpenCode must be restarted manually before authorization can start.'
+          : 'Failed to apply the callback settings. Use Apply & Restart, then authorize again.',
+      );
+    }
+  }
+};
+
 /** How long the user plausibly spends authorising before giving up on them. */
 const AUTHORIZATION_WATCH_MS = 3 * 60_000;
 const AUTHORIZATION_POLL_MS = 1_500;
@@ -129,14 +184,33 @@ const waitForAuthorizationThenFocus = async (name: string, directory: string | n
 export const startMcpAuthorization = async (input: {
   name: string;
   directory?: string | null;
-  /** VS Code cannot receive our callback route, so it keeps OpenCode's own redirect. */
-  skipRedirectUriBootstrap?: boolean;
 }): Promise<McpAuthorizationStart> => {
   const { name, directory } = input;
   let queuedState: string | null = null;
 
+  // Runtimes where the system browser provably lives on the same machine as
+  // OpenCode — desktop with the LOCAL embedded server, and VS Code (the
+  // extension always spawns its own local OpenCode): OpenCode's own flow works
+  // end-to-end over its FIXED loopback port (19876) — no config writes, no
+  // OpenCode restarts, no dependence on this app's per-launch port. The custom
+  // callback URL below stays for every case where the browser cannot reach
+  // OpenCode's loopback: remote instances, hosted web, mobile — and the plain
+  // web runtime too, because same-origin says nothing about the browser being
+  // on the server's machine.
+  if (isVSCodeRuntime() || (isDesktopShell() && getRuntimeKey() === 'local')) {
+    await clearCustomRedirectUriForNativeFlow(name);
+    const completion = useMcpStore.getState().authenticate(name, directory ?? null);
+    completion
+      .then(() => focusDesktopWindow())
+      .catch(() => {
+        // Recorded as a runtime diagnostic by the store; the status card and
+        // the caller's completion handling surface it.
+      });
+    return { authorizationUrl: '', opened: true, nativeFlow: true, completion };
+  }
+
   try {
-    if (!input.skipRedirectUriBootstrap) {
+    {
       // The config has to be loaded before its absence can mean anything. On
       // the first authorization after launch the store is often still empty,
       // and reading it then reported "no redirect URI" for a server that had
@@ -176,6 +250,25 @@ export const startMcpAuthorization = async (input: {
             saved.message || 'Failed to save the authorization callback URL',
           );
         }
+        // Config mutations accumulate behind Apply & Restart now, but the
+        // authorization flow runs against the LIVE OpenCode runtime: with the
+        // write still queued, OpenCode hands out its own loopback redirect and
+        // the callback never reaches us. The user just clicked Authorize —
+        // explicit intent — so apply the queued changes right away and start
+        // the flow against the runtime that actually has our callback URL.
+        if (saved.restartDeferred) {
+          const applied = await applyPendingOpenCodeRestart();
+          if (applied.requiresManualRestart) {
+            throw new McpAuthorizationError(
+              'The callback URL was saved, but OpenCode must be restarted manually before authorization can start.',
+            );
+          }
+          if (!applied.ok) {
+            throw new McpAuthorizationError(
+              'Failed to apply the saved callback URL. Use Apply & Restart, then authorize again.',
+            );
+          }
+        }
       }
     }
 
diff --git a/packages/ui/src/lib/i18n/messages/de.settings.ts b/packages/ui/src/lib/i18n/messages/de.settings.ts
index f405d959..1800c860 100644
--- a/packages/ui/src/lib/i18n/messages/de.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/de.settings.ts
@@ -1417,6 +1417,8 @@ export const settingsDict = {
   'settings.mcp.page.status.label.failed': 'Fehlgeschlagen',
   'settings.mcp.page.status.label.needsAuth': 'Autorisierung erforderlich',
   'settings.mcp.page.status.label.needsRegistration': 'Registrierung erforderlich',
+  'settings.mcp.page.status.label.awaitingRestart': 'Wartet auf Neustart',
+  'settings.mcp.page.status.description.awaitingRestart': 'Dieser Server ist gespeichert, aber noch nicht übernommen. Verwenden Sie „Apply & Restart“, damit OpenCode ihn lädt — danach sind Verbindung und Autorisierung verfügbar.',
   'settings.mcp.page.status.description.connected': 'Verbunden und bereit, Tools und Ressourcen zu entdecken.',
   'settings.mcp.page.status.description.failedDefault': 'OpenCode konnte diesen MCP-Server nicht erreichen.',
   'settings.mcp.page.status.description.needsAuth': 'Dieser entfernte MCP-Server erfordert Autorisierung, bevor eine Verbindung hergestellt werden kann.',
diff --git a/packages/ui/src/lib/i18n/messages/en.settings.ts b/packages/ui/src/lib/i18n/messages/en.settings.ts
index e43c5bee..0352de56 100644
--- a/packages/ui/src/lib/i18n/messages/en.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/en.settings.ts
@@ -1482,6 +1482,8 @@ export const settingsDict = {
   'settings.mcp.page.status.label.failed': 'Failed',
   'settings.mcp.page.status.label.needsAuth': 'Needs auth',
   'settings.mcp.page.status.label.needsRegistration': 'Needs registration',
+  'settings.mcp.page.status.label.awaitingRestart': 'Awaiting restart',
+  'settings.mcp.page.status.description.awaitingRestart': 'This server is saved but not applied yet. Use Apply & Restart to load it into OpenCode — connect and authorization become available after that.',
   'settings.mcp.page.status.description.connected': 'Connected and ready for OpenCode to discover tools and resources.',
   'settings.mcp.page.status.description.failedDefault': 'OpenCode could not reach this MCP server.',
   'settings.mcp.page.status.description.needsAuth': 'This remote MCP server requires authorization before it can connect.',
diff --git a/packages/ui/src/lib/i18n/messages/es.settings.ts b/packages/ui/src/lib/i18n/messages/es.settings.ts
index 3fcf7cf0..3bd93da2 100644
--- a/packages/ui/src/lib/i18n/messages/es.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/es.settings.ts
@@ -1459,6 +1459,8 @@ export const settingsDict = {
   "settings.mcp.page.status.label.failed": "Fallido",
   "settings.mcp.page.status.label.needsAuth": "Necesita autenticación",
   "settings.mcp.page.status.label.needsRegistration": "Necesita registro",
+  "settings.mcp.page.status.label.awaitingRestart": "Esperando reinicio",
+  "settings.mcp.page.status.description.awaitingRestart": "Este servidor está guardado pero aún no aplicado. Usa «Apply & Restart» para cargarlo en OpenCode; después estarán disponibles la conexión y la autorización.",
   "settings.mcp.page.status.description.connected": "Conectado y listo para que OpenCode descubra herramientas y recursos.",
   "settings.mcp.page.status.description.failedDefault": "OpenCode no pudo alcanzar este servidor MCP.",
   "settings.mcp.page.status.description.needsAuth": "Este servidor MCP remoto requiere autorización antes de poder conectarse.",
diff --git a/packages/ui/src/lib/i18n/messages/fr.settings.ts b/packages/ui/src/lib/i18n/messages/fr.settings.ts
index d5f08239..8537e2d0 100644
--- a/packages/ui/src/lib/i18n/messages/fr.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/fr.settings.ts
@@ -1377,6 +1377,8 @@ export const settingsDict = {
   'settings.mcp.page.status.label.failed': 'Échoué',
   'settings.mcp.page.status.label.needsAuth': 'Nécessite une authentification',
   'settings.mcp.page.status.label.needsRegistration': 'Nécessite une inscription',
+  'settings.mcp.page.status.label.awaitingRestart': 'En attente de redémarrage',
+  'settings.mcp.page.status.description.awaitingRestart': 'Ce serveur est enregistré mais pas encore appliqué. Utilisez « Apply & Restart » pour le charger dans OpenCode — la connexion et l\'autorisation seront ensuite disponibles.',
   'settings.mcp.page.status.description.connected': 'Connecté et prêt pour OpenCode pour découvrir des outils et des ressources.',
   'settings.mcp.page.status.description.failedDefault': 'OpenCode n\'a pas pu atteindre ce serveur MCP.',
   'settings.mcp.page.status.description.needsAuth': 'Ce serveur MCP distant nécessite une autorisation avant de pouvoir se connecter.',
diff --git a/packages/ui/src/lib/i18n/messages/ja.settings.ts b/packages/ui/src/lib/i18n/messages/ja.settings.ts
index ce1c06d5..4a17e635 100644
--- a/packages/ui/src/lib/i18n/messages/ja.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/ja.settings.ts
@@ -1492,6 +1492,8 @@ export const settingsDict = {
   'settings.mcp.page.status.label.failed': '失敗',
   'settings.mcp.page.status.label.needsAuth': '認証が必要',
   'settings.mcp.page.status.label.needsRegistration': '登録が必要',
+  'settings.mcp.page.status.label.awaitingRestart': '再起動待ち',
+  'settings.mcp.page.status.description.awaitingRestart': 'このサーバーは保存されていますが、まだ適用されていません。「Apply & Restart」で OpenCode に読み込むと、接続と認可が利用できるようになります。',
   'settings.mcp.page.status.description.connected': '接続済み。OpenCode がツールとリソースを検出できます。',
   'settings.mcp.page.status.description.failedDefault': 'OpenCode がこの MCP サーバーに到達できませんでした。',
   'settings.mcp.page.status.description.needsAuth': 'このリモート MCP サーバーは接続する前に認証が必要です。',
diff --git a/packages/ui/src/lib/i18n/messages/ko.settings.ts b/packages/ui/src/lib/i18n/messages/ko.settings.ts
index 1ca7fa88..47772407 100644
--- a/packages/ui/src/lib/i18n/messages/ko.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/ko.settings.ts
@@ -1459,6 +1459,8 @@ export const settingsDict = {
   'settings.mcp.page.status.label.failed': '실패',
   'settings.mcp.page.status.label.needsAuth': '인증 필요',
   'settings.mcp.page.status.label.needsRegistration': '등록 필요',
+  'settings.mcp.page.status.label.awaitingRestart': '재시작 대기 중',
+  'settings.mcp.page.status.description.awaitingRestart': '이 서버는 저장되었지만 아직 적용되지 않았습니다. Apply & Restart를 사용해 OpenCode에 불러오면 연결과 인증을 사용할 수 있습니다.',
   'settings.mcp.page.status.description.connected': '연결되었습니다. OpenCode가 도구와 리소스를 찾을 준비가 됐습니다.',
   'settings.mcp.page.status.description.failedDefault': 'OpenCode가 이 MCP 서버에 연결할 수 없습니다.',
   'settings.mcp.page.status.description.needsAuth': '이 원격 MCP 서버는 연결 전에 권한 부여가 필요합니다.',
diff --git a/packages/ui/src/lib/i18n/messages/pl.settings.ts b/packages/ui/src/lib/i18n/messages/pl.settings.ts
index 238fbec3..ccbb2355 100644
--- a/packages/ui/src/lib/i18n/messages/pl.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/pl.settings.ts
@@ -503,6 +503,8 @@ export const settingsDict = {
   'settings.mcp.page.status.label.failed': 'Błąd',
   'settings.mcp.page.status.label.needsAuth': 'Wymaga autoryzacji',
   'settings.mcp.page.status.label.needsRegistration': 'Wymaga rejestracji',
+  'settings.mcp.page.status.label.awaitingRestart': 'Oczekuje na restart',
+  'settings.mcp.page.status.description.awaitingRestart': 'Ten serwer został zapisany, ale nie został jeszcze zastosowany. Użyj Apply & Restart, aby OpenCode go wczytał — potem będą dostępne połączenie i autoryzacja.',
   'settings.mcp.page.status.projectScopedTo': 'Ograniczony do projektu w {directory}',
   'settings.mcp.page.status.runtimeStatus': 'Status uruchomieniowy',
   'settings.mcp.page.status.userScoped': 'Konfiguracja użytkownika',
diff --git a/packages/ui/src/lib/i18n/messages/pt-BR.settings.ts b/packages/ui/src/lib/i18n/messages/pt-BR.settings.ts
index f78f4611..1a10c763 100644
--- a/packages/ui/src/lib/i18n/messages/pt-BR.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/pt-BR.settings.ts
@@ -1459,6 +1459,8 @@ export const settingsDict = {
   "settings.mcp.page.status.label.failed": "Falhou",
   "settings.mcp.page.status.label.needsAuth": "Precisa de autenticação",
   "settings.mcp.page.status.label.needsRegistration": "Precisa de registro",
+  "settings.mcp.page.status.label.awaitingRestart": "Aguardando reinício",
+  "settings.mcp.page.status.description.awaitingRestart": "Este servidor foi salvo, mas ainda não aplicado. Use Apply & Restart para carregá-lo no OpenCode — depois disso, conexão e autorização ficam disponíveis.",
   "settings.mcp.page.status.description.connected": "Conectado e pronto para que OpenCode descubra ferramentas e recursos.",
   "settings.mcp.page.status.description.failedDefault": "OpenCode não conseguiu acessar este servidor MCP.",
   "settings.mcp.page.status.description.needsAuth": "Este servidor MCP remoto exige autorização antes de poder se conectar.",
diff --git a/packages/ui/src/lib/i18n/messages/uk.settings.ts b/packages/ui/src/lib/i18n/messages/uk.settings.ts
index 01d82066..e1dd276f 100644
--- a/packages/ui/src/lib/i18n/messages/uk.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/uk.settings.ts
@@ -1459,6 +1459,8 @@ export const settingsDict = {
   "settings.mcp.page.status.label.failed": "Не вдалося",
   "settings.mcp.page.status.label.needsAuth": "Потрібна авторизація",
   "settings.mcp.page.status.label.needsRegistration": "Потрібна реєстрація",
+  "settings.mcp.page.status.label.awaitingRestart": "Очікує перезапуску",
+  "settings.mcp.page.status.description.awaitingRestart": "Сервер збережено, але ще не застосовано. Натисніть Apply & Restart, щоб OpenCode його завантажив — після цього стануть доступні підключення та авторизація.",
   "settings.mcp.page.status.description.connected": "Підключено, OpenCode може відкривати інструменти й ресурси.",
   "settings.mcp.page.status.description.failedDefault": "OpenCode не вдалося отримати доступ до цього сервера MCP.",
   "settings.mcp.page.status.description.needsAuth": "Цей віддалений сервер MCP потребує авторизації, перш ніж він зможе підключитися.",
diff --git a/packages/ui/src/lib/i18n/messages/zh-CN.settings.ts b/packages/ui/src/lib/i18n/messages/zh-CN.settings.ts
index b8ecdb1a..bad265d7 100644
--- a/packages/ui/src/lib/i18n/messages/zh-CN.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-CN.settings.ts
@@ -1459,6 +1459,8 @@ export const settingsDict = {
   'settings.mcp.page.status.label.failed': '失败',
   'settings.mcp.page.status.label.needsAuth': '需要授权',
   'settings.mcp.page.status.label.needsRegistration': '需要注册',
+  'settings.mcp.page.status.label.awaitingRestart': '等待重启',
+  'settings.mcp.page.status.description.awaitingRestart': '该服务器已保存但尚未生效。使用 Apply & Restart 让 OpenCode 加载它——之后即可进行连接和授权。',
   'settings.mcp.page.status.description.connected': '已连接，OpenCode 可发现工具和资源。',
   'settings.mcp.page.status.description.failedDefault': 'OpenCode 无法连接到此 MCP 服务器。',
   'settings.mcp.page.status.description.needsAuth': '此远程 MCP 服务器在连接前需要授权。',
diff --git a/packages/ui/src/lib/i18n/messages/zh-TW.settings.ts b/packages/ui/src/lib/i18n/messages/zh-TW.settings.ts
index 116827ad..0ea5f711 100644
--- a/packages/ui/src/lib/i18n/messages/zh-TW.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-TW.settings.ts
@@ -1365,6 +1365,8 @@
   'settings.mcp.page.status.label.failed': '失敗',
   'settings.mcp.page.status.label.needsAuth': '需要授權',
   'settings.mcp.page.status.label.needsRegistration': '需要註冊',
+  'settings.mcp.page.status.label.awaitingRestart': '等待重新啟動',
+  'settings.mcp.page.status.description.awaitingRestart': '該伺服器已儲存但尚未生效。使用 Apply & Restart 讓 OpenCode 載入它——之後即可進行連線與授權。',
   'settings.mcp.page.status.description.connected': '已連線，OpenCode 可發現工具和資源。',
   'settings.mcp.page.status.description.failedDefault': 'OpenCode 無法連線到此 MCP 伺服器。',
   'settings.mcp.page.status.description.needsAuth': '此遠端 MCP 伺服器在連線前需要授權。',
diff --git a/packages/ui/src/stores/useMcpStore.ts b/packages/ui/src/stores/useMcpStore.ts
index 834f5e2a..1f9d2867 100644
--- a/packages/ui/src/stores/useMcpStore.ts
+++ b/packages/ui/src/stores/useMcpStore.ts
@@ -72,6 +72,12 @@ interface McpStore {
   connect: (name: string, directory?: string | null) => Promise<void>;
   disconnect: (name: string, directory?: string | null) => Promise<void>;
   startAuth: (name: string, directory?: string | null) => Promise<string>;
+  /**
+   * OpenCode's native full OAuth flow: OpenCode opens the browser, receives
+   * the callback on its own fixed loopback listener, and exchanges the code
+   * itself. Resolves only when the whole flow finishes (minutes, not ms).
+   */
+  authenticate: (name: string, directory?: string | null) => Promise<void>;
   completeAuth: (name: string, code: string, directory?: string | null) => Promise<void>;
   clearAuth: (name: string, directory?: string | null) => Promise<void>;
   testConnection: (name: string, directory?: string | null) => Promise<TestConnectionResult>;
@@ -178,6 +184,28 @@ export const useMcpStore = create<McpStore>()(
     },
 
 
+    authenticate: async (name, directory) => {
+      const normalized = normalizeDirectory(directory ?? useDirectoryStore.getState().currentDirectory);
+      const key = toKey(normalized);
+      const api = getMcpApiClient(normalized);
+      try {
+        await api.mcp.auth.authenticate({ name }, { throwOnError: true });
+      } catch (error) {
+        const message = error instanceof Error ? error.message : 'Authorization failed';
+        set((state) => ({
+          diagnosticsByDirectory: {
+            ...state.diagnosticsByDirectory,
+            [key]: {
+              ...(state.diagnosticsByDirectory[key] ?? {}),
+              [name]: { status: 'failed', error: message },
+            },
+          },
+        }));
+        throw error;
+      }
+      await get().refresh({ directory: normalized, silent: true });
+    },
+
     completeAuth: async (name, code, directory) => {
       const normalized = normalizeDirectory(directory ?? useDirectoryStore.getState().currentDirectory);
       const api = getMcpApiClient(normalized);
diff --git a/packages/web/server/lib/opencode/mcp-oauth-callback.test.js b/packages/web/server/lib/opencode/mcp-oauth-callback.test.js
new file mode 100644
index 00000000..4588922c
--- /dev/null
+++ b/packages/web/server/lib/opencode/mcp-oauth-callback.test.js
@@ -0,0 +1,111 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import express from 'express';
+import request from 'supertest';
+import { registerOpenCodeRoutes } from './routes.js';
+
+// No global body parser on purpose: the real server parses JSON per-route, so
+// these tests must fail if the pending route loses its own parser again.
+const createApp = (overrides = {}) => {
+  const app = express();
+  const dependencies = {
+    buildOpenCodeUrl: (path) => `http://opencode.local${path}`,
+    getOpenCodeAuthHeaders: () => ({ 'x-opencode-auth': 'test' }),
+    ...overrides,
+  };
+  registerOpenCodeRoutes(app, dependencies);
+  return { app, dependencies };
+};
+
+const queuePending = (app, { state, name, directory = null, origin = null }) =>
+  request(app)
+    .post('/api/mcp/auth/pending')
+    .send({ state, name, directory, origin })
+    .expect(200);
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+});
+
+describe('MCP OAuth browser callback route', () => {
+  it('completes authorization server-side for a parked state and clears it', async () => {
+    const upstreamFetch = vi.fn(async () => new Response(JSON.stringify({ success: true }), { status: 200 }));
+    vi.stubGlobal('fetch', upstreamFetch);
+    const { app } = createApp();
+    await queuePending(app, { state: 'state-1', name: 'linear', directory: '/projects/demo', origin: 'desktop' });
+
+    const response = await request(app)
+      .get('/mcp/oauth/callback')
+      .query({ state: 'state-1', code: 'auth-code', server: 'linear' })
+      .expect(200);
+
+    expect(upstreamFetch).toHaveBeenCalledTimes(1);
+    const [url, init] = upstreamFetch.mock.calls[0];
+    expect(String(url)).toBe('http://opencode.local/mcp/linear/auth/callback?directory=%2Fprojects%2Fdemo');
+    expect(init.method).toBe('POST');
+    expect(JSON.parse(init.body)).toEqual({ code: 'auth-code' });
+    expect(init.headers['x-opencode-auth']).toBe('test');
+
+    expect(response.text).toContain('Authorization Complete');
+    // Started from the desktop shell: the page hands control back via deep link.
+    expect(response.text).toContain('openchamber://focus/mcp-auth');
+
+    await request(app).get('/api/mcp/auth/pending').query({ state: 'state-1' }).expect(404);
+  });
+
+  it('never forwards a code whose state is unknown', async () => {
+    const upstreamFetch = vi.fn();
+    vi.stubGlobal('fetch', upstreamFetch);
+    const { app } = createApp();
+
+    const response = await request(app)
+      .get('/mcp/oauth/callback')
+      .query({ state: 'forged', code: 'attacker-code', server: 'linear' })
+      .expect(400);
+
+    expect(upstreamFetch).not.toHaveBeenCalled();
+    expect(response.text).toContain('Authorization Failed');
+  });
+
+  it('omits the desktop deep link for flows started outside the desktop shell', async () => {
+    vi.stubGlobal('fetch', vi.fn(async () => new Response('{}', { status: 200 })));
+    const { app } = createApp();
+    await queuePending(app, { state: 'state-web', name: 'linear' });
+
+    const response = await request(app)
+      .get('/mcp/oauth/callback')
+      .query({ state: 'state-web', code: 'auth-code' })
+      .expect(200);
+
+    expect(response.text).not.toContain('openchamber://');
+  });
+
+  it('reports a provider error without contacting OpenCode', async () => {
+    const upstreamFetch = vi.fn();
+    vi.stubGlobal('fetch', upstreamFetch);
+    const { app } = createApp();
+    await queuePending(app, { state: 'state-2', name: 'linear' });
+
+    const response = await request(app)
+      .get('/mcp/oauth/callback')
+      .query({ state: 'state-2', error: 'access_denied', error_description: 'User <denied> access' })
+      .expect(400);
+
+    expect(upstreamFetch).not.toHaveBeenCalled();
+    // Interpolated provider text is escaped, not rendered as markup.
+    expect(response.text).toContain('User &lt;denied&gt; access');
+    await request(app).get('/api/mcp/auth/pending').query({ state: 'state-2' }).expect(404);
+  });
+
+  it('surfaces an OpenCode rejection as a failed page', async () => {
+    vi.stubGlobal('fetch', vi.fn(async () => new Response(JSON.stringify({ error: 'invalid code' }), { status: 400 })));
+    const { app } = createApp();
+    await queuePending(app, { state: 'state-3', name: 'linear' });
+
+    const response = await request(app)
+      .get('/mcp/oauth/callback')
+      .query({ state: 'state-3', code: 'stale-code' })
+      .expect(502);
+
+    expect(response.text).toContain('invalid code');
+  });
+});
diff --git a/packages/web/server/lib/opencode/proxy.js b/packages/web/server/lib/opencode/proxy.js
index 9d1be85b..48a14f38 100644
--- a/packages/web/server/lib/opencode/proxy.js
+++ b/packages/web/server/lib/opencode/proxy.js
@@ -839,5 +839,9 @@ export const registerOpenCodeProxy = (app, deps) => {
 
   app.use('/api', applyProxyResponseDeadline);
   app.post('/api/provider/:providerID/oauth/callback', interactiveOAuthProxy);
+  // OpenCode's native MCP OAuth flow: the request blocks until the user
+  // finishes authorization in the browser (up to OpenCode's 5-minute callback
+  // timeout), so it needs the interactive-OAuth deadline, not the default one.
+  app.post('/api/mcp/:name/auth/authenticate', interactiveOAuthProxy);
   app.use('/api', apiProxy);
 };
diff --git a/packages/web/server/lib/opencode/routes.js b/packages/web/server/lib/opencode/routes.js
index 617e9667..b72bdd1e 100644
--- a/packages/web/server/lib/opencode/routes.js
+++ b/packages/web/server/lib/opencode/routes.js
@@ -1,3 +1,4 @@
+import express from 'express';
 import { createProjectIdFromPath } from '../projects/project-id.js';
 import fs from 'fs';
 import os from 'os';
@@ -46,6 +47,46 @@ export const registerOpenCodeRoutes = (app, dependencies) => {
     return trimmed || null;
   };
 
+  const escapeHtml = (value) => String(value)
+    .replace(/&/g, '&amp;')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;')
+    .replace(/"/g, '&quot;')
+    .replace(/'/g, '&#39;');
+
+  // Self-contained page for the OAuth return leg: the system browser has no UI
+  // session, so it cannot load the SPA behind the auth gate — everything it
+  // needs ships inline. `openchamber://focus/mcp-auth` raises the desktop app;
+  // the link stays visible because some browsers only follow custom-protocol
+  // URLs from a user gesture.
+  const renderMcpOAuthCallbackPage = ({ title, message, desktopReturn }) => `<!doctype html>
+<html lang="en">
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width, initial-scale=1">
+<title>${escapeHtml(title)} — OpenChamber</title>
+<style>
+  :root { color-scheme: light dark; }
+  body { margin: 0; min-height: 100vh; display: flex; align-items: center; justify-content: center;
+         font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
+         background: Canvas; color: CanvasText; }
+  main { max-width: 34rem; padding: 2.5rem 2rem; text-align: center; }
+  h1 { font-size: 1.25rem; margin: 0 0 0.75rem; }
+  p { margin: 0; line-height: 1.5; opacity: 0.85; }
+  a.return { display: inline-block; margin-top: 1.5rem; padding: 0.5rem 1.25rem; border-radius: 0.5rem;
+             border: 1px solid color-mix(in srgb, CanvasText 25%, transparent); color: inherit; text-decoration: none; }
+</style>
+</head>
+<body>
+<main>
+<h1>${escapeHtml(title)}</h1>
+<p>${escapeHtml(message)}</p>
+${desktopReturn ? `<a class="return" href="openchamber://focus/mcp-auth">Return to OpenChamber</a>
+<script>window.location.href = 'openchamber://focus/mcp-auth';</script>` : ''}
+</main>
+</body>
+</html>`;
+
   const readOpenCodeCurrentVersion = async () => {
     const healthResponse = await fetch(buildOpenCodeUrl('/global/health', ''), {
       method: 'GET',
@@ -341,7 +382,10 @@ export const registerOpenCodeRoutes = (app, dependencies) => {
     }
   });
 
-  app.post('/api/mcp/auth/pending', async (req, res) => {
+  // The body parser is per-route on this server; without it req.body is
+  // undefined here, the state read as absent, and the "parked" context was
+  // silently never stored — the callback then always failed as unknown.
+  app.post('/api/mcp/auth/pending', express.json({ limit: '16kb' }), async (req, res) => {
     try {
       pruneExpiredPendingMcpAuthContexts();
 
@@ -417,6 +461,89 @@ export const registerOpenCodeRoutes = (app, dependencies) => {
     }
   });
 
+  // Browser return leg of the MCP OAuth flow, completed entirely server-side.
+  //
+  // The provider redirects the SYSTEM browser here, and that browser has no
+  // OpenChamber UI session — the SPA route this path used to land on sits
+  // behind the client-side auth gate, so the user saw a login page instead of
+  // a finished authorization. No session can be required on this path.
+  //
+  // Safe without auth because it acts only on a code+state pair whose `state`
+  // matches a context parked by an authenticated start call: `state` is the
+  // OAuth CSRF secret, generated per flow and known only to the initiating
+  // client and the provider. Without a match the code is NOT forwarded, so an
+  // unauthenticated caller cannot bind this server's MCP entry to a foreign
+  // account by fabricating a callback. The endpoint reads nothing and mutates
+  // nothing else.
+  app.get('/mcp/oauth/callback', async (req, res) => {
+    const queryValue = (key) => normalizePendingString(Array.isArray(req.query?.[key]) ? req.query[key][0] : req.query?.[key]);
+    const state = queryValue('state');
+    const code = queryValue('code');
+    const providerError = queryValue('error');
+    const providerErrorDescription = queryValue('error_description');
+
+    pruneExpiredPendingMcpAuthContexts();
+    const context = state ? pendingMcpAuthContextByState.get(state) ?? null : null;
+    const startedFromDesktop = context?.origin === 'desktop';
+
+    const finish = (status, { title, message }) => {
+      if (state) pendingMcpAuthContextByState.delete(state);
+      res.status(status).type('html').send(renderMcpOAuthCallbackPage({
+        title,
+        message,
+        // Browsers only follow custom-protocol links from a user gesture in
+        // some configurations, so the page both tries the jump and keeps a
+        // visible link as the fallback.
+        desktopReturn: startedFromDesktop,
+      }));
+    };
+
+    if (providerError) {
+      return finish(400, {
+        title: 'Authorization Failed',
+        message: providerErrorDescription || providerError,
+      });
+    }
+    if (!code) {
+      return finish(400, {
+        title: 'Authorization Failed',
+        message: 'The provider did not return an authorization code. Start authorization again from MCP Settings.',
+      });
+    }
+    if (!context?.name) {
+      return finish(400, {
+        title: 'Authorization Failed',
+        message: 'This authorization session has expired or is unknown to the running app. Return to OpenChamber and click Authorize again.',
+      });
+    }
+
+    try {
+      const callbackUrl = new URL(buildOpenCodeUrl(`/mcp/${encodeURIComponent(context.name)}/auth/callback`, ''));
+      if (context.directory) callbackUrl.searchParams.set('directory', context.directory);
+      const upstream = await fetch(callbackUrl, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json', Accept: 'application/json', ...getOpenCodeAuthHeaders() },
+        body: JSON.stringify({ code }),
+      });
+      if (!upstream.ok) {
+        const payload = await upstream.json().catch(() => null);
+        return finish(502, {
+          title: 'Authorization Failed',
+          message: payload?.error || payload?.message || `OpenCode rejected the authorization code (${upstream.status}). Start authorization again from MCP Settings.`,
+        });
+      }
+      return finish(200, {
+        title: 'Authorization Complete',
+        message: 'You can close this tab and return to OpenChamber.',
+      });
+    } catch (error) {
+      return finish(502, {
+        title: 'Authorization Failed',
+        message: error?.message || 'Failed to complete MCP authorization.',
+      });
+    }
+  });
+
   app.get('/api/provider/:providerId/source', async (req, res) => {
     try {
       const { providerId } = req.params;