diff --git a/src/commands/auth.ts b/src/commands/auth.ts
index 3c896a5..e70a1fa 100644
--- a/src/commands/auth.ts
+++ b/src/commands/auth.ts
@@ -357,8 +357,17 @@ async function persistSiteCredential(
 
   if (available) {
     const credentialRef = credentialRefForAlias(alias);
-    await store.set(credentialRef, staffTokenInput);
-    return { credentialRef };
+    try {
+      await store.set(credentialRef, staffTokenInput);
+      return { credentialRef };
+    } catch (err) {
+      if (!allowInsecureStorage) {
+        throw err;
+      }
+      // store.set() failed even though isAvailable() returned true (e.g. D-Bus
+      // service became unavailable between probe and write). Fall through to
+      // plaintext storage since --insecure-storage was explicitly requested.
+    }
   }
 
   if (!allowInsecureStorage) {
diff --git a/src/lib/credentials.ts b/src/lib/credentials.ts
index 1b5b9fc..6c226f1 100644
--- a/src/lib/credentials.ts
+++ b/src/lib/credentials.ts
@@ -176,7 +176,11 @@ function createLinuxAdapter(): CredentialStoreAdapter {
           LINUX_ATTR_REF,
           '__probe__',
         ]);
-        return probe.code === 0 || probe.code === 1;
+        // code 1 = credential not found (service healthy); code 0 = found.
+        // When the Secret Service is not activatable, secret-tool exits with a
+        // non-zero code AND writes a D-Bus error to stderr. A healthy "not found"
+        // response produces no stderr output, so any stderr indicates unavailability.
+        return (probe.code === 0 || probe.code === 1) && probe.stderr.trim() === '';
       } catch {
         return false;
       }
diff --git a/tests/credentials-and-security.test.ts b/tests/credentials-and-security.test.ts
index 1d8fa21..cfa0052 100644
--- a/tests/credentials-and-security.test.ts
+++ b/tests/credentials-and-security.test.ts
@@ -7,6 +7,7 @@ import { readUserConfig } from '../src/lib/config.js';
 import { setCredentialStoreForTests } from '../src/lib/credentials.js';
 import { ExitCode } from '../src/lib/errors.js';
 import {
+  createBrokenCredentialStore,
   createMemoryCredentialStore,
   createUnavailableCredentialStore,
 } from './helpers/mock-credentials.js';
@@ -136,6 +137,53 @@ describe('credential storage and security defaults', () => {
     expect(raw.sites?.myblog?.credentialRef).toBeUndefined();
   });
 
+  test('falls back to plaintext when store reports available but set throws and --insecure-storage is passed', async () => {
+    setCredentialStoreForTests(createBrokenCredentialStore());
+
+    await expect(
+      run([
+        'node',
+        'ghst',
+        'auth',
+        'login',
+        '--non-interactive',
+        '--url',
+        'https://myblog.ghost.io',
+        '--staff-token',
+        KEY,
+        '--site',
+        'myblog',
+        '--insecure-storage',
+      ]),
+    ).resolves.toBe(ExitCode.SUCCESS);
+
+    const raw = JSON.parse(await fs.readFile(path.join(configDir, 'config.json'), 'utf8')) as {
+      sites?: Record<string, { staffAccessToken?: string; credentialRef?: string }>;
+    };
+    expect(raw.sites?.myblog?.staffAccessToken).toBe(KEY);
+    expect(raw.sites?.myblog?.credentialRef).toBeUndefined();
+  });
+
+  test('re-throws store set error without --insecure-storage when store reports available but set throws', async () => {
+    setCredentialStoreForTests(createBrokenCredentialStore());
+
+    await expect(
+      run([
+        'node',
+        'ghst',
+        'auth',
+        'login',
+        '--non-interactive',
+        '--url',
+        'https://myblog.ghost.io',
+        '--staff-token',
+        KEY,
+        '--site',
+        'myblog',
+      ]),
+    ).resolves.toBe(ExitCode.GENERAL_ERROR);
+  });
+
   test('migrates plaintext staff tokens into secure store on read', async () => {
     const store = createMemoryCredentialStore();
     setCredentialStoreForTests(store);
diff --git a/tests/helpers/mock-credentials.ts b/tests/helpers/mock-credentials.ts
index 7be0870..fe7939f 100644
--- a/tests/helpers/mock-credentials.ts
+++ b/tests/helpers/mock-credentials.ts
@@ -27,3 +27,14 @@ export function createUnavailableCredentialStore(): CredentialStore {
     delete: async () => undefined,
   };
 }
+
+export function createBrokenCredentialStore(): CredentialStore {
+  return {
+    isAvailable: async () => true,
+    set: async () => {
+      throw new Error('Failed to store credential in Secret Service: secret-tool: The name is not activatable');
+    },
+    get: async () => null,
+    delete: async () => undefined,
+  };
+}
diff --git a/tests/lib-credentials.test.ts b/tests/lib-credentials.test.ts
index dcf317e..ccef911 100644
--- a/tests/lib-credentials.test.ts
+++ b/tests/lib-credentials.test.ts
@@ -179,6 +179,31 @@ describe.sequential('credential store adapters', () => {
     await expect(store.isAvailable()).resolves.toBe(false);
   });
 
+  test('linux adapter returns unavailable when probe exits code 1 with D-Bus stderr', async () => {
+    delete process.env.VITEST;
+    setPlatform('linux');
+    resetCredentialStoreCacheForTests();
+
+    queueSpawnOutcomes([
+      { code: 1, stderr: 'secret-tool: The name is not activatable\n' },
+    ]);
+
+    const store = getCredentialStore();
+    await expect(store.isAvailable()).resolves.toBe(false);
+  });
+
+  test('linux adapter considers service available only when probe exits cleanly with no stderr', async () => {
+    delete process.env.VITEST;
+    setPlatform('linux');
+    resetCredentialStoreCacheForTests();
+
+    // code 1 with no stderr = "not found" (service healthy)
+    queueSpawnOutcomes([{ code: 1, stderr: '' }]);
+
+    const store = getCredentialStore();
+    await expect(store.isAvailable()).resolves.toBe(true);
+  });
+
   test('linux adapter handles input piping and error branches', async () => {
     delete process.env.VITEST;
     setPlatform('linux');