fix(gemini): preserve authorization URL error messages

frontend/src/composables/__tests__/useGeminiOAuth.errors.spec.ts

@@ -0,0 +1,39 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { useGeminiOAuth } from '../useGeminiOAuth'
+
+const mocks = vi.hoisted(() => ({ generateAuthUrl: vi.fn(), showError: vi.fn() }))
+vi.mock('@/api/admin', () => ({ adminAPI: { gemini: { generateAuthUrl: mocks.generateAuthUrl } } }))
+vi.mock('@/stores/app', () => ({ useAppStore: () => ({ showError: mocks.showError }) }))
+vi.mock('vue-i18n', () => ({ useI18n: () => ({ t: (key: string) => key }) }))
+beforeEach(() => vi.resetAllMocks())
+
+describe('Gemini authorization URL errors', () => {
+  it.each([
+    [{ status: 400, message: 'Selected proxy is unavailable' }, 'Selected proxy is unavailable'],
+    [{ response: { data: { detail: 'OAuth is not configured' } } }, 'OAuth is not configured'],
+    [{}, 'admin.accounts.oauth.gemini.failedToGenerateUrl'],
+    [null, 'admin.accounts.oauth.gemini.failedToGenerateUrl']
+  ])('preserves useful API feedback for %j', async (error, expected) => {
+    mocks.generateAuthUrl.mockRejectedValue(error)
+    const oauth = useGeminiOAuth()
+    expect(await oauth.generateAuthUrl(7)).toBe(false)
+    expect(oauth.error.value).toBe(expected)
+    expect(mocks.showError).toHaveBeenCalledWith(expected)
+    expect(oauth.loading.value).toBe(false)
+    expect(oauth.authUrl.value).toBe('')
+  })
+
+  it('can retry successfully after an error', async () => {
+    mocks.generateAuthUrl.mockRejectedValueOnce({ message: 'Temporary failure' }).mockResolvedValueOnce({
+      auth_url: 'https://example.com/auth', session_id: 'session', state: 'state'
+    })
+    const oauth = useGeminiOAuth()
+    await oauth.generateAuthUrl(7)
+    expect(await oauth.generateAuthUrl(7, ' project ')).toBe(true)
+    expect(oauth.error.value).toBe('')
+    expect(oauth.authUrl.value).toBe('https://example.com/auth')
+    expect(oauth.sessionId.value).toBe('session')
+    expect(oauth.state.value).toBe('state')
+    expect(mocks.generateAuthUrl).toHaveBeenLastCalledWith({ proxy_id: 7, project_id: 'project' })
+  })
+})

frontend/src/composables/useGeminiOAuth.ts

@@ -2,6 +2,7 @@ import { ref } from 'vue'
 import { useI18n } from 'vue-i18n'
 import { useAppStore } from '@/stores/app'
 import { adminAPI } from '@/api/admin'
+import { extractApiErrorMessage } from '@/utils/apiError'
 import type { GeminiOAuthCapabilities } from '@/api/admin/gemini'
 
 export interface GeminiTokenInfo {
@@ -61,8 +62,8 @@ export function useGeminiOAuth() {
       sessionId.value = response.session_id
       state.value = response.state
       return true
-    } catch (err: any) {
-      error.value = err.response?.data?.detail || t('admin.accounts.oauth.gemini.failedToGenerateUrl')
+    } catch (err: unknown) {
+      error.value = extractApiErrorMessage(err, t('admin.accounts.oauth.gemini.failedToGenerateUrl'))
       appStore.showError(error.value)
       return false
     } finally {