diff --git a/src/core/services/cli-command.test.ts b/src/core/services/cli-command.test.ts
index 3935d24..7370c7a 100644
--- a/src/core/services/cli-command.test.ts
+++ b/src/core/services/cli-command.test.ts
@@ -39,6 +39,7 @@ function makeArgs(overrides: Partial<CliArgs> = {}): CliArgs {
     jellyfinSubtitleUrlsOnly: false,
     jellyfinPlay: false,
     jellyfinRemoteAnnounce: false,
+    jellyfinPreviewAuth: false,
     texthooker: false,
     help: false,
     autoStartOverlay: false,
diff --git a/src/core/services/startup-bootstrap.test.ts b/src/core/services/startup-bootstrap.test.ts
index dff7c40..3372d79 100644
--- a/src/core/services/startup-bootstrap.test.ts
+++ b/src/core/services/startup-bootstrap.test.ts
@@ -39,6 +39,7 @@ function makeArgs(overrides: Partial<CliArgs> = {}): CliArgs {
     jellyfinSubtitleUrlsOnly: false,
     jellyfinPlay: false,
     jellyfinRemoteAnnounce: false,
+    jellyfinPreviewAuth: false,
     texthooker: false,
     help: false,
     autoStartOverlay: false,
diff --git a/src/main.ts b/src/main.ts
index c9b34a8..89ef363 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1498,6 +1498,10 @@ const {
       listJellyfinItemsRuntime(session, clientInfo, params),
     listJellyfinSubtitleTracks: (session, clientInfo, itemId) =>
       listJellyfinSubtitleTracksRuntime(session, clientInfo, itemId),
+    writeJellyfinPreviewAuth: (responsePath, payload) => {
+      fs.mkdirSync(path.dirname(responsePath), { recursive: true });
+      fs.writeFileSync(responsePath, JSON.stringify(payload, null, 2), 'utf-8');
+    },
     logInfo: (message) => logger.info(message),
   },
   handleJellyfinPlayCommandMainDeps: {
diff --git a/src/main/runtime/composers/jellyfin-runtime-composer.test.ts b/src/main/runtime/composers/jellyfin-runtime-composer.test.ts
index 193c2f9..ed68a1d 100644
--- a/src/main/runtime/composers/jellyfin-runtime-composer.test.ts
+++ b/src/main/runtime/composers/jellyfin-runtime-composer.test.ts
@@ -111,6 +111,7 @@ test('composeJellyfinRuntimeHandlers returns callable jellyfin runtime handlers'
       listJellyfinLibraries: async () => [],
       listJellyfinItems: async () => [],
       listJellyfinSubtitleTracks: async () => [],
+      writeJellyfinPreviewAuth: () => {},
       logInfo: () => {},
     },
     handleJellyfinPlayCommandMainDeps: {
diff --git a/src/main/runtime/jellyfin-cli-main-deps.test.ts b/src/main/runtime/jellyfin-cli-main-deps.test.ts
index 66f8b08..780c5a0 100644
--- a/src/main/runtime/jellyfin-cli-main-deps.test.ts
+++ b/src/main/runtime/jellyfin-cli-main-deps.test.ts
@@ -31,6 +31,10 @@ test('jellyfin auth commands main deps builder maps callbacks', async () => {
 
 test('jellyfin list commands main deps builder maps callbacks', async () => {
   const calls: string[] = [];
+  const writes: Array<{
+    responsePath: string;
+    payload: { serverUrl: string; accessToken: string; userId: string };
+  }> = [];
   const deps = createBuildHandleJellyfinListCommandsMainDepsHandler({
     listJellyfinLibraries: async () => {
       calls.push('libraries');
@@ -44,14 +48,32 @@ test('jellyfin list commands main deps builder maps callbacks', async () => {
       calls.push('subtitles');
       return [];
     },
+    writeJellyfinPreviewAuth: (responsePath, payload) => {
+      writes.push({ responsePath, payload });
+    },
     logInfo: (message) => calls.push(`info:${message}`),
   })();
 
   await deps.listJellyfinLibraries({} as never, {} as never);
   await deps.listJellyfinItems({} as never, {} as never, { libraryId: '', limit: 1 });
   await deps.listJellyfinSubtitleTracks({} as never, {} as never, 'id');
+  deps.writeJellyfinPreviewAuth('/tmp/jellyfin-preview.json', {
+    serverUrl: 'https://example.test',
+    accessToken: 'token',
+    userId: 'user-id',
+  });
   deps.logInfo('done');
   assert.deepEqual(calls, ['libraries', 'items', 'subtitles', 'info:done']);
+  assert.deepEqual(writes, [
+    {
+      responsePath: '/tmp/jellyfin-preview.json',
+      payload: {
+        serverUrl: 'https://example.test',
+        accessToken: 'token',
+        userId: 'user-id',
+      },
+    },
+  ]);
 });
 
 test('jellyfin play command main deps builder maps callbacks', async () => {
diff --git a/src/main/runtime/jellyfin-cli-main-deps.ts b/src/main/runtime/jellyfin-cli-main-deps.ts
index 5f85d97..d0e163f 100644
--- a/src/main/runtime/jellyfin-cli-main-deps.ts
+++ b/src/main/runtime/jellyfin-cli-main-deps.ts
@@ -32,6 +32,8 @@ export function createBuildHandleJellyfinListCommandsMainDepsHandler(
       deps.listJellyfinItems(session, clientInfo, params),
     listJellyfinSubtitleTracks: (session, clientInfo, itemId) =>
       deps.listJellyfinSubtitleTracks(session, clientInfo, itemId),
+    writeJellyfinPreviewAuth: (responsePath, payload) =>
+      deps.writeJellyfinPreviewAuth(responsePath, payload),
     logInfo: (message: string) => deps.logInfo(message),
   });
 }