diff --git a/README.md b/README.md
index 36eed3eb..bee390ba 100644
--- a/README.md
+++ b/README.md
@@ -116,13 +116,15 @@ Advanced and source-build guides:
 | Provider | Setup Path | Notes |
 | --- | --- | --- |
 | OpenAI-compatible | `/provider` or env vars | Works with OpenAI, OpenRouter, DeepSeek, Groq, Mistral, LM Studio, and compatible local `/v1` servers |
-| Gemini | `/provider` or env vars | Google Gemini support through the runtime provider layer |
+| Gemini | `/provider` or env vars | Google Gemini support through the runtime provider layer (API key, access token, or local ADC) |
 | GitHub Models | `/onboard-github` | Interactive onboarding with saved credentials |
 | Codex | `/provider` | Uses existing Codex credentials when available |
 | Ollama | `/provider` or env vars | Local inference with no API key |
 | Atomic Chat | advanced setup | Local Apple Silicon backend |
 | Bedrock / Vertex / Foundry | env vars | Additional provider integrations for supported environments |
 
+For Gemini, `/provider` can now save either the API-key path, a securely stored access-token path, or a local ADC profile.
+
 ---
 
 ## What Works
diff --git a/src/commands/provider/provider.test.tsx b/src/commands/provider/provider.test.tsx
index 7f5560dc..c04c2d18 100644
--- a/src/commands/provider/provider.test.tsx
+++ b/src/commands/provider/provider.test.tsx
@@ -197,6 +197,23 @@ test('buildProfileSaveMessage maps provider fields without echoing secrets', ()
   expect(message).not.toContain('sk-secret-12345678')
 })
 
+test('buildProfileSaveMessage describes Gemini access token / ADC mode clearly', () => {
+  const message = buildProfileSaveMessage(
+    'gemini',
+    {
+      GEMINI_AUTH_MODE: 'access-token',
+      GEMINI_MODEL: 'gemini-2.5-flash',
+      GEMINI_BASE_URL: 'https://generativelanguage.googleapis.com/v1beta/openai',
+    },
+    'D:/codings/Opensource/openclaude/.openclaude-profile.json',
+  )
+
+  expect(message).toContain('Saved Google Gemini profile.')
+  expect(message).toContain('Model: gemini-2.5-flash')
+  expect(message).toContain('Credentials: access token (stored securely)')
+  expect(message).not.toContain('AIza')
+})
+
 test('buildCurrentProviderSummary redacts poisoned model and endpoint values', () => {
   const summary = buildCurrentProviderSummary({
     processEnv: {
diff --git a/src/commands/provider/provider.tsx b/src/commands/provider/provider.tsx
index b43b6c3d..6bf8a06c 100644
--- a/src/commands/provider/provider.tsx
+++ b/src/commands/provider/provider.tsx
@@ -36,6 +36,14 @@ import {
   type ProfileFile,
   type ProviderProfile,
 } from '../../utils/providerProfile.js'
+import {
+  getGeminiProjectIdHint,
+  mayHaveGeminiAdcCredentials,
+} from '../../utils/geminiAuth.js'
+import {
+  readGeminiAccessToken,
+  saveGeminiAccessToken,
+} from '../../utils/geminiCredentials.js'
 import {
   getGoalDefaultOpenAIModel,
   normalizeRecommendationGoal,
@@ -60,8 +68,14 @@ type Step =
       baseUrl: string | null
       defaultModel: string
     }
+  | { name: 'gemini-auth-method' }
   | { name: 'gemini-key' }
-  | { name: 'gemini-model'; apiKey: string }
+  | { name: 'gemini-access-token' }
+  | {
+      name: 'gemini-model'
+      apiKey?: string
+      authMode: 'api-key' | 'access-token' | 'adc'
+    }
   | { name: 'codex-check' }
 
 type CurrentProviderSummary = {
@@ -216,9 +230,13 @@ function buildSavedProfileSummary(
           env,
         ),
         credentialLabel:
-          maskSecretForDisplay(env.GEMINI_API_KEY) !== undefined
-            ? 'configured'
-            : undefined,
+          env.GEMINI_AUTH_MODE === 'access-token'
+            ? 'access token (stored securely)'
+            : env.GEMINI_AUTH_MODE === 'adc'
+              ? 'local ADC'
+            : maskSecretForDisplay(env.GEMINI_API_KEY) !== undefined
+              ? 'configured'
+              : undefined,
       }
     case 'codex':
       return {
@@ -427,7 +445,7 @@ function ProviderChooser({
     {
       label: 'Gemini',
       value: 'gemini',
-      description: 'Use a Google Gemini API key',
+      description: 'Use Google Gemini with API key, access token, or local ADC',
     },
     {
       label: 'Codex',
@@ -926,7 +944,7 @@ export function ProviderWizard({
                 defaultModel: defaults.openAIModel,
               })
             } else if (value === 'gemini') {
-              setStep({ name: 'gemini-key' })
+              setStep({ name: 'gemini-auth-method' })
             } else if (value === 'clear') {
               const filePath = deleteProfileFile()
               onDone(`Removed saved provider profile at ${filePath}. Restart OpenClaude to go back to normal startup.`, {
@@ -1066,12 +1084,76 @@ export function ProviderWizard({
         />
       )
 
+    case 'gemini-auth-method': {
+      const hasShellGeminiKey = Boolean(
+        process.env.GEMINI_API_KEY || process.env.GOOGLE_API_KEY,
+      )
+      const hasShellGeminiAccessToken = Boolean(process.env.GEMINI_ACCESS_TOKEN)
+      const hasStoredGeminiAccessToken = Boolean(readGeminiAccessToken())
+      const hasAdc = mayHaveGeminiAdcCredentials(process.env)
+      const projectHint = getGeminiProjectIdHint(process.env)
+
+      const options: OptionWithDescription[] = [
+        {
+          label: 'API key',
+          value: 'api-key',
+          description: hasShellGeminiKey
+            ? 'Use the current Gemini API key from this shell, or enter a new one'
+            : 'Use a Google Gemini API key',
+        },
+        {
+          label: 'Access token',
+          value: 'access-token',
+          description: hasShellGeminiAccessToken || hasStoredGeminiAccessToken
+            ? `Use ${
+                hasShellGeminiAccessToken
+                  ? 'the current GEMINI_ACCESS_TOKEN'
+                  : 'the securely stored Gemini access token'
+              }`
+            : 'Enter a Gemini access token and store it securely',
+        },
+        {
+          label: 'Local ADC',
+          value: 'adc',
+          description: hasAdc
+            ? `Use local Google ADC credentials${projectHint ? ` (project: ${projectHint})` : ''}`
+            : 'Use local Google ADC credentials after running gcloud auth application-default login',
+        },
+      ]
+
+      return (
+        <Dialog title="Gemini setup" onCancel={() => onDone()}>
+          <Box flexDirection="column" gap={1}>
+            <Text>Choose how this Gemini profile should authenticate.</Text>
+            <Select
+              options={options}
+              inlineDescriptions
+              visibleOptionCount={options.length}
+              onChange={value => {
+                if (value === 'api-key') {
+                  setStep({ name: 'gemini-key' })
+                } else if (value === 'access-token') {
+                  setStep({ name: 'gemini-access-token' })
+                } else {
+                  setStep({
+                    name: 'gemini-model',
+                    authMode: 'adc',
+                  })
+                }
+              }}
+              onCancel={() => setStep({ name: 'choose' })}
+            />
+          </Box>
+        </Dialog>
+      )
+    }
+
     case 'gemini-key':
       return (
         <TextEntryDialog
           resetStateKey={step.name}
           title="Gemini setup"
-          subtitle="Step 1 of 2"
+          subtitle="Step 1 of 3"
           description={
             process.env.GEMINI_API_KEY || process.env.GOOGLE_API_KEY
               ? 'Enter a Gemini API key, or leave this blank to reuse the current GEMINI_API_KEY/GOOGLE_API_KEY from this session.'
@@ -1089,25 +1171,95 @@ export function ProviderWizard({
               process.env.GEMINI_API_KEY ||
               process.env.GOOGLE_API_KEY ||
               ''
-            setStep({ name: 'gemini-model', apiKey })
+            setStep({ name: 'gemini-model', apiKey, authMode: 'api-key' })
           }}
-          onCancel={() => setStep({ name: 'choose' })}
+          onCancel={() => setStep({ name: 'gemini-auth-method' })}
         />
       )
 
+    case 'gemini-access-token': {
+      const currentToken =
+        process.env.GEMINI_ACCESS_TOKEN || readGeminiAccessToken() || ''
+      return (
+        <TextEntryDialog
+          resetStateKey={step.name}
+          title="Gemini setup"
+          subtitle="Step 2 of 3"
+          description={
+            currentToken
+              ? 'Enter a Gemini access token, or leave this blank to reuse the current token from this session or secure storage.'
+              : 'Enter a Gemini access token. It will be stored securely for this profile.'
+          }
+          initialValue=""
+          placeholder="ya29...."
+          mask="*"
+          allowEmpty={Boolean(currentToken)}
+          validate={value => {
+            const token = value.trim() || currentToken
+            return token ? null : 'Enter a Gemini access token or go back and choose Local ADC.'
+          }}
+          onSubmit={value => {
+            const token = value.trim() || currentToken
+            const saved = saveGeminiAccessToken(token)
+            if (!saved.success) {
+              onDone(
+                `Failed to save Gemini access token: ${saved.warning ?? 'unknown error'}`,
+                {
+                  display: 'system',
+                },
+              )
+              return
+            }
+
+            setStep({
+              name: 'gemini-model',
+              authMode: 'access-token',
+            })
+          }}
+          onCancel={() => setStep({ name: 'gemini-auth-method' })}
+        />
+      )
+    }
+
     case 'gemini-model':
       return (
         <TextEntryDialog
           resetStateKey={step.name}
           title="Gemini setup"
-          subtitle="Step 2 of 2"
-          description={`Enter a Gemini model name. Leave blank for ${DEFAULT_GEMINI_MODEL}.`}
+          subtitle={
+            step.authMode === 'api-key'
+              ? 'Step 3 of 3'
+              : step.authMode === 'access-token'
+                ? 'Step 3 of 3'
+                : 'Step 2 of 2'
+          }
+          description={
+            step.authMode === 'api-key'
+              ? `Enter a Gemini model name. Leave blank for ${DEFAULT_GEMINI_MODEL}.`
+              : step.authMode === 'access-token'
+                ? `Enter a Gemini model name. Leave blank for ${DEFAULT_GEMINI_MODEL}. This profile will use the stored Gemini access token at runtime.`
+                : `Enter a Gemini model name. Leave blank for ${DEFAULT_GEMINI_MODEL}. This profile will use local Google ADC credentials at runtime.`
+          }
           initialValue={defaults.geminiModel}
           placeholder={DEFAULT_GEMINI_MODEL}
           allowEmpty
           onSubmit={value => {
+            if (
+              step.authMode === 'adc' &&
+              !mayHaveGeminiAdcCredentials(process.env)
+            ) {
+              onDone(
+                'Local ADC credentials were not detected. Run `gcloud auth application-default login` first, then save the Gemini ADC profile again.',
+                {
+                  display: 'system',
+                },
+              )
+              return
+            }
+
             const env = buildGeminiProfileEnv({
               apiKey: step.apiKey,
+              authMode: step.authMode,
               model: value.trim() || DEFAULT_GEMINI_MODEL,
               processEnv: {},
             })
@@ -1115,7 +1267,13 @@ export function ProviderWizard({
               finishProfileSave(onDone, 'gemini', env)
             }
           }}
-          onCancel={() => setStep({ name: 'gemini-key' })}
+          onCancel={() =>
+            step.authMode === 'api-key'
+              ? setStep({ name: 'gemini-key' })
+              : step.authMode === 'access-token'
+                ? setStep({ name: 'gemini-access-token' })
+                : setStep({ name: 'gemini-auth-method' })
+          }
         />
       )
 
diff --git a/src/entrypoints/cli.tsx b/src/entrypoints/cli.tsx
index 4f75d5c3..ee91304a 100644
--- a/src/entrypoints/cli.tsx
+++ b/src/entrypoints/cli.tsx
@@ -1,14 +1,12 @@
 import { feature } from 'bun:bundle';
-import {
-  isLocalProviderUrl,
-  resolveCodexApiCredentials,
-  resolveProviderRequest,
-} from '../services/api/providerConfig.js'
 import {
   applyProfileEnvToProcessEnv,
   buildStartupEnvFromProfile,
-  redactSecretValueForDisplay,
 } from '../utils/providerProfile.js'
+import {
+  getProviderValidationError,
+  validateProviderEnvOrExit,
+} from '../utils/providerValidation.js'
 
 // OpenClaude: disable experimental API betas by default.
 // Tool search (defer_loading), global cache scope, and context management
@@ -42,82 +40,6 @@ if (feature('ABLATION_BASELINE') && process.env.CLAUDE_CODE_ABLATION_BASELINE) {
   }
 }
 
-function isEnvTruthy(value: string | undefined): boolean {
-  if (!value) return false
-  const normalized = value.trim().toLowerCase()
-  return normalized !== '' && normalized !== '0' && normalized !== 'false' && normalized !== 'no'
-}
-
-function getProviderValidationError(
-  env: NodeJS.ProcessEnv = process.env,
-): string | null {
-  const useOpenAI = isEnvTruthy(env.CLAUDE_CODE_USE_OPENAI)
-  const useGithub = isEnvTruthy(env.CLAUDE_CODE_USE_GITHUB)
-
-  if (isEnvTruthy(env.CLAUDE_CODE_USE_GEMINI)) {
-    if (!(env.GEMINI_API_KEY ?? env.GOOGLE_API_KEY)) {
-      return 'GEMINI_API_KEY is required when CLAUDE_CODE_USE_GEMINI=1.'
-    }
-    return null
-  }
-
-  if (useGithub && !useOpenAI) {
-    const token = (env.GITHUB_TOKEN?.trim() || env.GH_TOKEN?.trim()) ?? ''
-    if (!token) {
-      return 'GITHUB_TOKEN or GH_TOKEN is required when CLAUDE_CODE_USE_GITHUB=1.'
-    }
-    return null
-  }
-
-  if (!useOpenAI) {
-    return null
-  }
-
-  const request = resolveProviderRequest({
-    model: env.OPENAI_MODEL,
-    baseUrl: env.OPENAI_BASE_URL,
-  })
-
-  if (env.OPENAI_API_KEY === 'SUA_CHAVE') {
-    return 'Invalid OPENAI_API_KEY: placeholder value SUA_CHAVE detected. Set a real key or unset for local providers.'
-  }
-
-  if (request.transport === 'codex_responses') {
-    const credentials = resolveCodexApiCredentials(env)
-    if (!credentials.apiKey) {
-      const authHint = credentials.authPath
-        ? ` or put auth.json at ${credentials.authPath}`
-        : ''
-      const safeModel =
-        redactSecretValueForDisplay(request.requestedModel, env) ??
-        'the requested model'
-      return `Codex auth is required for ${safeModel}. Set CODEX_API_KEY${authHint}.`
-    }
-    if (!credentials.accountId) {
-      return 'Codex auth is missing chatgpt_account_id. Re-login with Codex or set CHATGPT_ACCOUNT_ID/CODEX_ACCOUNT_ID.'
-    }
-    return null
-  }
-
-  if (!env.OPENAI_API_KEY && !isLocalProviderUrl(request.baseUrl)) {
-    const hasGithubToken = !!(env.GITHUB_TOKEN?.trim() || env.GH_TOKEN?.trim())
-    if (useGithub && hasGithubToken) {
-      return null
-    }
-    return 'OPENAI_API_KEY is required when CLAUDE_CODE_USE_OPENAI=1 and OPENAI_BASE_URL is not local.'
-  }
-
-  return null
-}
-
-function validateProviderEnvOrExit(): void {
-  const error = getProviderValidationError()
-  if (error) {
-    console.error(error)
-    process.exit(1)
-  }
-}
-
 /**
  * Bootstrap entrypoint - checks for special flags before loading the full CLI.
  * All imports are dynamic to minimize module evaluation for fast paths.
@@ -151,6 +73,8 @@ async function main(): Promise<void> {
     enableConfigs()
     const { applySafeConfigEnvironmentVariables } = await import('../utils/managedEnv.js')
     applySafeConfigEnvironmentVariables()
+    const { hydrateGeminiAccessTokenFromSecureStorage } = await import('../utils/geminiCredentials.js')
+    hydrateGeminiAccessTokenFromSecureStorage()
     const { hydrateGithubModelsTokenFromSecureStorage } = await import('../utils/githubModelsCredentials.js')
     hydrateGithubModelsTokenFromSecureStorage()
   }
@@ -159,7 +83,7 @@ async function main(): Promise<void> {
     processEnv: process.env,
   })
   if (startupEnv !== process.env) {
-    const startupProfileError = getProviderValidationError(startupEnv)
+    const startupProfileError = await getProviderValidationError(startupEnv)
     if (startupProfileError) {
       console.error(
         `Warning: ignoring saved provider profile. ${startupProfileError}`,
@@ -169,7 +93,7 @@ async function main(): Promise<void> {
     }
   }
 
-  validateProviderEnvOrExit()
+  await validateProviderEnvOrExit()
 
   // Print the gradient startup screen before the Ink UI loads
   const { printStartupScreen } = await import('../components/StartupScreen.js')
diff --git a/src/services/api/openaiShim.test.ts b/src/services/api/openaiShim.test.ts
index 681755e3..be975650 100644
--- a/src/services/api/openaiShim.test.ts
+++ b/src/services/api/openaiShim.test.ts
@@ -6,10 +6,27 @@ type FetchType = typeof globalThis.fetch
 const originalEnv = {
   OPENAI_BASE_URL: process.env.OPENAI_BASE_URL,
   OPENAI_API_KEY: process.env.OPENAI_API_KEY,
+  OPENAI_MODEL: process.env.OPENAI_MODEL,
+  CLAUDE_CODE_USE_GEMINI: process.env.CLAUDE_CODE_USE_GEMINI,
+  GEMINI_API_KEY: process.env.GEMINI_API_KEY,
+  GOOGLE_API_KEY: process.env.GOOGLE_API_KEY,
+  GEMINI_ACCESS_TOKEN: process.env.GEMINI_ACCESS_TOKEN,
+  GEMINI_AUTH_MODE: process.env.GEMINI_AUTH_MODE,
+  GEMINI_BASE_URL: process.env.GEMINI_BASE_URL,
+  GEMINI_MODEL: process.env.GEMINI_MODEL,
+  GOOGLE_CLOUD_PROJECT: process.env.GOOGLE_CLOUD_PROJECT,
 }
 
 const originalFetch = globalThis.fetch
 
+function restoreEnv(key: string, value: string | undefined): void {
+  if (value === undefined) {
+    delete process.env[key]
+  } else {
+    process.env[key] = value
+  }
+}
+
 type OpenAIShimClient = {
   beta: {
     messages: {
@@ -52,11 +69,29 @@ function makeStreamChunks(chunks: unknown[]): string[] {
 beforeEach(() => {
   process.env.OPENAI_BASE_URL = 'http://example.test/v1'
   process.env.OPENAI_API_KEY = 'test-key'
+  delete process.env.OPENAI_MODEL
+  delete process.env.CLAUDE_CODE_USE_GEMINI
+  delete process.env.GEMINI_API_KEY
+  delete process.env.GOOGLE_API_KEY
+  delete process.env.GEMINI_ACCESS_TOKEN
+  delete process.env.GEMINI_AUTH_MODE
+  delete process.env.GEMINI_BASE_URL
+  delete process.env.GEMINI_MODEL
+  delete process.env.GOOGLE_CLOUD_PROJECT
 })
 
 afterEach(() => {
-  process.env.OPENAI_BASE_URL = originalEnv.OPENAI_BASE_URL
-  process.env.OPENAI_API_KEY = originalEnv.OPENAI_API_KEY
+  restoreEnv('OPENAI_BASE_URL', originalEnv.OPENAI_BASE_URL)
+  restoreEnv('OPENAI_API_KEY', originalEnv.OPENAI_API_KEY)
+  restoreEnv('OPENAI_MODEL', originalEnv.OPENAI_MODEL)
+  restoreEnv('CLAUDE_CODE_USE_GEMINI', originalEnv.CLAUDE_CODE_USE_GEMINI)
+  restoreEnv('GEMINI_API_KEY', originalEnv.GEMINI_API_KEY)
+  restoreEnv('GOOGLE_API_KEY', originalEnv.GOOGLE_API_KEY)
+  restoreEnv('GEMINI_ACCESS_TOKEN', originalEnv.GEMINI_ACCESS_TOKEN)
+  restoreEnv('GEMINI_AUTH_MODE', originalEnv.GEMINI_AUTH_MODE)
+  restoreEnv('GEMINI_BASE_URL', originalEnv.GEMINI_BASE_URL)
+  restoreEnv('GEMINI_MODEL', originalEnv.GEMINI_MODEL)
+  restoreEnv('GOOGLE_CLOUD_PROJECT', originalEnv.GOOGLE_CLOUD_PROJECT)
   globalThis.fetch = originalFetch
 })
 
@@ -308,6 +343,76 @@ test('preserves image tool results as placeholders in follow-up requests', async
   expect(toolMessage?.content).toContain('[image:image/png]')
 })
 
+test('uses GEMINI_ACCESS_TOKEN for Gemini OpenAI-compatible requests', async () => {
+  let capturedAuthorization: string | null = null
+  let capturedProject: string | null = null
+  let requestUrl: string | undefined
+
+  process.env.CLAUDE_CODE_USE_GEMINI = '1'
+  process.env.GEMINI_AUTH_MODE = 'access-token'
+  process.env.GEMINI_ACCESS_TOKEN = 'gemini-access-token'
+  process.env.GOOGLE_CLOUD_PROJECT = 'gemini-project'
+  process.env.GEMINI_BASE_URL =
+    'https://generativelanguage.googleapis.com/v1beta/openai'
+  process.env.GEMINI_MODEL = 'gemini-2.0-flash'
+  delete process.env.OPENAI_BASE_URL
+  delete process.env.OPENAI_API_KEY
+  delete process.env.GEMINI_API_KEY
+  delete process.env.GOOGLE_API_KEY
+
+  globalThis.fetch = (async (input, init) => {
+    requestUrl = typeof input === 'string' ? input : input.url
+    const headers = init?.headers as Record<string, string> | undefined
+    capturedAuthorization =
+      headers?.Authorization ?? headers?.authorization ?? null
+    capturedProject =
+      headers?.['x-goog-user-project'] ??
+      headers?.['X-Goog-User-Project'] ??
+      null
+
+    return new Response(
+      JSON.stringify({
+        id: 'chatcmpl-gemini',
+        model: 'gemini-2.0-flash',
+        choices: [
+          {
+            message: {
+              role: 'assistant',
+              content: 'ok',
+            },
+            finish_reason: 'stop',
+          },
+        ],
+        usage: {
+          prompt_tokens: 3,
+          completion_tokens: 1,
+          total_tokens: 4,
+        },
+      }),
+      {
+        headers: {
+          'Content-Type': 'application/json',
+        },
+      },
+    )
+  }) as FetchType
+
+  const client = createOpenAIShimClient({}) as OpenAIShimClient
+
+  await client.beta.messages.create({
+    model: 'gemini-2.0-flash',
+    messages: [{ role: 'user', content: 'hello' }],
+    max_tokens: 32,
+    stream: false,
+  })
+
+  expect(requestUrl).toBe(
+    'https://generativelanguage.googleapis.com/v1beta/openai/chat/completions',
+  )
+  expect(capturedAuthorization).toBe('Bearer gemini-access-token')
+  expect(capturedProject).toBe('gemini-project')
+})
+
 test('preserves Gemini tool call extra_content from streaming chunks', async () => {
   globalThis.fetch = (async (_input, _init) => {
     const chunks = makeStreamChunks([
diff --git a/src/services/api/openaiShim.ts b/src/services/api/openaiShim.ts
index 128b075d..29f0ce87 100644
--- a/src/services/api/openaiShim.ts
+++ b/src/services/api/openaiShim.ts
@@ -23,6 +23,8 @@
 
 import { APIError } from '@anthropic-ai/sdk'
 import { isEnvTruthy } from '../../utils/envUtils.js'
+import { resolveGeminiCredential } from '../../utils/geminiAuth.js'
+import { hydrateGeminiAccessTokenFromSecureStorage } from '../../utils/geminiCredentials.js'
 import { hydrateGithubModelsTokenFromSecureStorage } from '../../utils/githubModelsCredentials.js'
 import {
   codexStreamToAnthropic,
@@ -46,6 +48,7 @@ type SecretValueSource = Partial<{
   CODEX_API_KEY: string
   GEMINI_API_KEY: string
   GOOGLE_API_KEY: string
+  GEMINI_ACCESS_TOKEN: string
 }>
 
 const GITHUB_MODELS_DEFAULT_BASE = 'https://models.github.ai/inference'
@@ -893,7 +896,9 @@ class OpenAIShimMessages {
       ...(options?.headers ?? {}),
     }
 
-    const apiKey = this.providerOverride?.apiKey ?? process.env.OPENAI_API_KEY ?? ''
+    const isGemini = isEnvTruthy(process.env.CLAUDE_CODE_USE_GEMINI)
+    const apiKey =
+      this.providerOverride?.apiKey ?? process.env.OPENAI_API_KEY ?? ''
     // Detect Azure endpoints by hostname (not raw URL) to prevent bypass via
     // path segments like https://evil.com/cognitiveservices.azure.com/
     let isAzure = false
@@ -910,6 +915,14 @@ class OpenAIShimMessages {
       } else {
         headers.Authorization = `Bearer ${apiKey}`
       }
+    } else if (isGemini) {
+      const geminiCredential = await resolveGeminiCredential(process.env)
+      if (geminiCredential.kind !== 'none') {
+        headers.Authorization = `Bearer ${geminiCredential.credential}`
+        if (geminiCredential.projectId) {
+          headers['x-goog-user-project'] = geminiCredential.projectId
+        }
+      }
     }
 
     if (isGithub) {
@@ -1105,6 +1118,7 @@ export function createOpenAIShimClient(options: {
   reasoningEffort?: 'low' | 'medium' | 'high' | 'xhigh'
   providerOverride?: { model: string; baseURL: string; apiKey: string }
 }): unknown {
+  hydrateGeminiAccessTokenFromSecureStorage()
   hydrateGithubModelsTokenFromSecureStorage()
 
   // When Gemini provider is active, map Gemini env vars to OpenAI-compatible ones
@@ -1113,8 +1127,11 @@ export function createOpenAIShimClient(options: {
     process.env.OPENAI_BASE_URL ??=
       process.env.GEMINI_BASE_URL ??
       'https://generativelanguage.googleapis.com/v1beta/openai'
-    process.env.OPENAI_API_KEY ??=
-      process.env.GEMINI_API_KEY ?? process.env.GOOGLE_API_KEY ?? ''
+    const geminiApiKey =
+      process.env.GEMINI_API_KEY ?? process.env.GOOGLE_API_KEY
+    if (geminiApiKey && !process.env.OPENAI_API_KEY) {
+      process.env.OPENAI_API_KEY = geminiApiKey
+    }
     if (process.env.GEMINI_MODEL && !process.env.OPENAI_MODEL) {
       process.env.OPENAI_MODEL = process.env.GEMINI_MODEL
     }
diff --git a/src/utils/geminiAuth.test.ts b/src/utils/geminiAuth.test.ts
new file mode 100644
index 00000000..8bb9a5c2
--- /dev/null
+++ b/src/utils/geminiAuth.test.ts
@@ -0,0 +1,186 @@
+import { afterEach, describe, expect, test } from 'bun:test'
+
+import {
+  getGeminiProjectIdHint,
+  mayHaveGeminiAdcCredentials,
+  resolveGeminiCredential,
+} from './geminiAuth.ts'
+
+const existingFilePath = import.meta.path
+
+const originalEnv = {
+  GEMINI_API_KEY: process.env.GEMINI_API_KEY,
+  GOOGLE_API_KEY: process.env.GOOGLE_API_KEY,
+  GEMINI_ACCESS_TOKEN: process.env.GEMINI_ACCESS_TOKEN,
+  GEMINI_AUTH_MODE: process.env.GEMINI_AUTH_MODE,
+  GOOGLE_APPLICATION_CREDENTIALS: process.env.GOOGLE_APPLICATION_CREDENTIALS,
+  GOOGLE_CLOUD_PROJECT: process.env.GOOGLE_CLOUD_PROJECT,
+  GCLOUD_PROJECT: process.env.GCLOUD_PROJECT,
+  GOOGLE_PROJECT_ID: process.env.GOOGLE_PROJECT_ID,
+  APPDATA: process.env.APPDATA,
+}
+
+function restoreEnv(key: string, value: string | undefined): void {
+  if (value === undefined) {
+    delete process.env[key]
+  } else {
+    process.env[key] = value
+  }
+}
+
+afterEach(() => {
+  restoreEnv('GEMINI_API_KEY', originalEnv.GEMINI_API_KEY)
+  restoreEnv('GOOGLE_API_KEY', originalEnv.GOOGLE_API_KEY)
+  restoreEnv('GEMINI_ACCESS_TOKEN', originalEnv.GEMINI_ACCESS_TOKEN)
+  restoreEnv('GEMINI_AUTH_MODE', originalEnv.GEMINI_AUTH_MODE)
+  restoreEnv(
+    'GOOGLE_APPLICATION_CREDENTIALS',
+    originalEnv.GOOGLE_APPLICATION_CREDENTIALS,
+  )
+  restoreEnv('GOOGLE_CLOUD_PROJECT', originalEnv.GOOGLE_CLOUD_PROJECT)
+  restoreEnv('GCLOUD_PROJECT', originalEnv.GCLOUD_PROJECT)
+  restoreEnv('GOOGLE_PROJECT_ID', originalEnv.GOOGLE_PROJECT_ID)
+  restoreEnv('APPDATA', originalEnv.APPDATA)
+})
+
+describe('resolveGeminiCredential', () => {
+  test('prefers GEMINI_API_KEY over other Gemini auth inputs', async () => {
+    process.env.GEMINI_API_KEY = 'gem-key'
+    process.env.GOOGLE_API_KEY = 'google-key'
+    process.env.GEMINI_ACCESS_TOKEN = 'token-123'
+
+    await expect(resolveGeminiCredential(process.env)).resolves.toEqual({
+      kind: 'api-key',
+      credential: 'gem-key',
+    })
+  })
+
+  test('uses GEMINI_ACCESS_TOKEN when no API key is configured', async () => {
+    delete process.env.GEMINI_API_KEY
+    delete process.env.GOOGLE_API_KEY
+    process.env.GEMINI_AUTH_MODE = 'access-token'
+    process.env.GEMINI_ACCESS_TOKEN = 'token-123'
+    process.env.GOOGLE_CLOUD_PROJECT = 'test-project'
+
+    await expect(resolveGeminiCredential(process.env)).resolves.toEqual({
+      kind: 'access-token',
+      credential: 'token-123',
+      projectId: 'test-project',
+    })
+  })
+
+  test('falls back to ADC when available', async () => {
+    delete process.env.GEMINI_API_KEY
+    delete process.env.GOOGLE_API_KEY
+    delete process.env.GEMINI_ACCESS_TOKEN
+    process.env.GEMINI_AUTH_MODE = 'adc'
+    process.env.GOOGLE_APPLICATION_CREDENTIALS = existingFilePath
+
+    const fakeAuth = {
+      async getClient() {
+        return {
+          async getAccessToken() {
+            return { token: 'adc-token' }
+          },
+        }
+      },
+      async getProjectId() {
+        return 'adc-project'
+      },
+    }
+
+    await expect(
+      resolveGeminiCredential(process.env, {
+        createGoogleAuth: async () => fakeAuth,
+      }),
+    ).resolves.toEqual({
+      kind: 'adc',
+      credential: 'adc-token',
+      projectId: 'adc-project',
+    })
+  })
+
+  test('returns none when no Gemini auth source is configured', async () => {
+    delete process.env.GEMINI_API_KEY
+    delete process.env.GOOGLE_API_KEY
+    delete process.env.GEMINI_ACCESS_TOKEN
+    delete process.env.GOOGLE_APPLICATION_CREDENTIALS
+
+    await expect(resolveGeminiCredential(process.env)).resolves.toEqual({
+      kind: 'none',
+    })
+  })
+
+  test('access-token mode does not silently fall back to ADC', async () => {
+    delete process.env.GEMINI_API_KEY
+    delete process.env.GOOGLE_API_KEY
+    delete process.env.GEMINI_ACCESS_TOKEN
+    process.env.GEMINI_AUTH_MODE = 'access-token'
+    process.env.GOOGLE_APPLICATION_CREDENTIALS = existingFilePath
+
+    const fakeAuth = {
+      async getClient() {
+        return {
+          async getAccessToken() {
+            return { token: 'adc-token' }
+          },
+        }
+      },
+    }
+
+    await expect(
+      resolveGeminiCredential(process.env, {
+        createGoogleAuth: async () => fakeAuth,
+      }),
+    ).resolves.toEqual({
+      kind: 'none',
+    })
+  })
+
+  test('adc mode ignores GEMINI_ACCESS_TOKEN and uses ADC credentials', async () => {
+    delete process.env.GEMINI_API_KEY
+    delete process.env.GOOGLE_API_KEY
+    process.env.GEMINI_AUTH_MODE = 'adc'
+    process.env.GEMINI_ACCESS_TOKEN = 'token-123'
+    process.env.GOOGLE_APPLICATION_CREDENTIALS = existingFilePath
+
+    const fakeAuth = {
+      async getClient() {
+        return {
+          async getAccessToken() {
+            return { token: 'adc-token' }
+          },
+        }
+      },
+      async getProjectId() {
+        return 'adc-project'
+      },
+    }
+
+    await expect(
+      resolveGeminiCredential(process.env, {
+        createGoogleAuth: async () => fakeAuth,
+      }),
+    ).resolves.toEqual({
+      kind: 'adc',
+      credential: 'adc-token',
+      projectId: 'adc-project',
+    })
+  })
+})
+
+describe('Gemini auth helpers', () => {
+  test('detects explicit project id hints', () => {
+    process.env.GOOGLE_PROJECT_ID = 'project-a'
+    expect(getGeminiProjectIdHint(process.env)).toBe('project-a')
+  })
+
+  test('only treats existing ADC paths as valid hints', () => {
+    process.env.GOOGLE_APPLICATION_CREDENTIALS = existingFilePath
+    expect(mayHaveGeminiAdcCredentials(process.env)).toBe(true)
+
+    process.env.GOOGLE_APPLICATION_CREDENTIALS = `${existingFilePath}.missing`
+    process.env.APPDATA = undefined
+    expect(mayHaveGeminiAdcCredentials(process.env)).toBe(false)
+  })
+})
diff --git a/src/utils/geminiAuth.ts b/src/utils/geminiAuth.ts
new file mode 100644
index 00000000..d22d0d2f
--- /dev/null
+++ b/src/utils/geminiAuth.ts
@@ -0,0 +1,216 @@
+import { existsSync } from 'node:fs'
+import { homedir } from 'node:os'
+import { join } from 'node:path'
+
+import { memoizeWithTTLAsync } from './memoize.js'
+
+const GEMINI_ADC_SCOPE = 'https://www.googleapis.com/auth/cloud-platform'
+const GEMINI_ADC_CACHE_TTL_MS = 5 * 60 * 1000
+
+export type GeminiAuthMode = 'api-key' | 'access-token' | 'adc'
+
+type GoogleAccessTokenResult =
+  | string
+  | null
+  | undefined
+  | {
+      token?: string | null
+    }
+
+type GoogleAuthClientLike = {
+  getAccessToken(): Promise<GoogleAccessTokenResult> | GoogleAccessTokenResult
+}
+
+type GoogleAuthLike = {
+  getClient(): Promise<GoogleAuthClientLike>
+  getProjectId?(): Promise<string>
+}
+
+export type GeminiResolvedCredential =
+  | {
+      kind: 'api-key'
+      credential: string
+    }
+  | {
+      kind: 'access-token' | 'adc'
+      credential: string
+      projectId?: string
+    }
+  | {
+      kind: 'none'
+    }
+
+type ResolveGeminiCredentialDeps = {
+  createGoogleAuth?: () => Promise<GoogleAuthLike>
+}
+
+function sanitizeCredential(value: string | undefined | null): string | undefined {
+  const trimmed = value?.trim()
+  return trimmed ? trimmed : undefined
+}
+
+export function getGeminiProjectIdHint(
+  env: NodeJS.ProcessEnv = process.env,
+): string | undefined {
+  return (
+    sanitizeCredential(env.GOOGLE_CLOUD_PROJECT) ??
+    sanitizeCredential(env.GCLOUD_PROJECT) ??
+    sanitizeCredential(env.GOOGLE_PROJECT_ID)
+  )
+}
+
+export function getGeminiAuthMode(
+  env: NodeJS.ProcessEnv = process.env,
+): GeminiAuthMode | undefined {
+  const normalized = sanitizeCredential(env.GEMINI_AUTH_MODE)?.toLowerCase()
+  if (
+    normalized === 'api-key' ||
+    normalized === 'access-token' ||
+    normalized === 'adc'
+  ) {
+    return normalized
+  }
+  return undefined
+}
+
+export function getGeminiAdcCredentialPaths(
+  env: NodeJS.ProcessEnv = process.env,
+): string[] {
+  const explicit = sanitizeCredential(env.GOOGLE_APPLICATION_CREDENTIALS)
+  const paths = new Set<string>()
+
+  if (explicit) {
+    paths.add(explicit)
+  }
+
+  paths.add(join(homedir(), '.config', 'gcloud', 'application_default_credentials.json'))
+
+  const appData = sanitizeCredential(env.APPDATA)
+  if (appData) {
+    paths.add(join(appData, 'gcloud', 'application_default_credentials.json'))
+  }
+
+  return [...paths]
+}
+
+export function mayHaveGeminiAdcCredentials(
+  env: NodeJS.ProcessEnv = process.env,
+): boolean {
+  return getGeminiAdcCredentialPaths(env).some(path => existsSync(path))
+}
+
+function normalizeAccessToken(
+  value: GoogleAccessTokenResult,
+): string | undefined {
+  if (typeof value === 'string') {
+    return sanitizeCredential(value)
+  }
+  return sanitizeCredential(value?.token)
+}
+
+async function createDefaultGoogleAuth(): Promise<GoogleAuthLike> {
+  const { GoogleAuth } = await import('google-auth-library')
+  return new GoogleAuth({
+    scopes: [GEMINI_ADC_SCOPE],
+  }) as GoogleAuthLike
+}
+
+async function resolveGeminiAdcCredentialUncached(
+  env: NodeJS.ProcessEnv,
+  deps: ResolveGeminiCredentialDeps,
+): Promise<Exclude<GeminiResolvedCredential, { kind: 'none' | 'api-key' | 'access-token' }> | { kind: 'none' }> {
+  if (!mayHaveGeminiAdcCredentials(env)) {
+    return { kind: 'none' }
+  }
+
+  try {
+    const auth = await (deps.createGoogleAuth ?? createDefaultGoogleAuth)()
+    const client = await auth.getClient()
+    const accessToken = normalizeAccessToken(await client.getAccessToken())
+    if (!accessToken) {
+      return { kind: 'none' }
+    }
+
+    const hintedProjectId = getGeminiProjectIdHint(env)
+    const resolvedProjectId =
+      hintedProjectId ??
+      (typeof auth.getProjectId === 'function'
+        ? sanitizeCredential(await auth.getProjectId().catch(() => undefined))
+        : undefined)
+
+    return {
+      kind: 'adc',
+      credential: accessToken,
+      ...(resolvedProjectId ? { projectId: resolvedProjectId } : {}),
+    }
+  } catch {
+    return { kind: 'none' }
+  }
+}
+
+const resolveDefaultGeminiAdcCredential = memoizeWithTTLAsync(
+  async (
+    googleApplicationCredentials: string | undefined,
+    appData: string | undefined,
+    home: string,
+    projectIdHint: string | undefined,
+  ) =>
+    resolveGeminiAdcCredentialUncached(
+      {
+        GOOGLE_APPLICATION_CREDENTIALS: googleApplicationCredentials,
+        APPDATA: appData,
+        GOOGLE_CLOUD_PROJECT: projectIdHint,
+        GCLOUD_PROJECT: projectIdHint,
+        GOOGLE_PROJECT_ID: projectIdHint,
+        HOME: home,
+      } as NodeJS.ProcessEnv,
+      {},
+    ),
+  GEMINI_ADC_CACHE_TTL_MS,
+)
+
+export async function resolveGeminiCredential(
+  env: NodeJS.ProcessEnv = process.env,
+  deps: ResolveGeminiCredentialDeps = {},
+): Promise<GeminiResolvedCredential> {
+  const authMode = getGeminiAuthMode(env)
+  const apiKey =
+    authMode === 'access-token' || authMode === 'adc'
+      ? undefined
+      : sanitizeCredential(env.GEMINI_API_KEY) ??
+        sanitizeCredential(env.GOOGLE_API_KEY)
+  if (apiKey && (authMode === undefined || authMode === 'api-key')) {
+    return {
+      kind: 'api-key',
+      credential: apiKey,
+    }
+  }
+
+  const accessToken =
+    authMode === 'api-key' || authMode === 'adc'
+      ? undefined
+      : sanitizeCredential(env.GEMINI_ACCESS_TOKEN)
+  if (accessToken && (authMode === undefined || authMode === 'access-token')) {
+    const projectId = getGeminiProjectIdHint(env)
+    return {
+      kind: 'access-token',
+      credential: accessToken,
+      ...(projectId ? { projectId } : {}),
+    }
+  }
+
+  if (authMode === 'api-key' || authMode === 'access-token') {
+    return { kind: 'none' }
+  }
+
+  if (deps.createGoogleAuth) {
+    return resolveGeminiAdcCredentialUncached(env, deps)
+  }
+
+  return resolveDefaultGeminiAdcCredential(
+    sanitizeCredential(env.GOOGLE_APPLICATION_CREDENTIALS),
+    sanitizeCredential(env.APPDATA),
+    homedir(),
+    getGeminiProjectIdHint(env),
+  )
+}
diff --git a/src/utils/geminiCredentials.test.ts b/src/utils/geminiCredentials.test.ts
new file mode 100644
index 00000000..87c5e4ca
--- /dev/null
+++ b/src/utils/geminiCredentials.test.ts
@@ -0,0 +1,31 @@
+import { afterEach, expect, test } from 'bun:test'
+
+import {
+  clearGeminiAccessToken,
+  readGeminiAccessToken,
+  saveGeminiAccessToken,
+} from './geminiCredentials.ts'
+
+const originalToken = process.env.GEMINI_ACCESS_TOKEN
+
+afterEach(() => {
+  if (originalToken === undefined) {
+    delete process.env.GEMINI_ACCESS_TOKEN
+  } else {
+    process.env.GEMINI_ACCESS_TOKEN = originalToken
+  }
+  clearGeminiAccessToken()
+})
+
+test('saveGeminiAccessToken stores and reads back the token', () => {
+  const result = saveGeminiAccessToken('token-123')
+  expect(result.success).toBe(true)
+  expect(readGeminiAccessToken()).toBe('token-123')
+})
+
+test('clearGeminiAccessToken removes the stored token', () => {
+  expect(saveGeminiAccessToken('token-123').success).toBe(true)
+  expect(clearGeminiAccessToken().success).toBe(true)
+  expect(readGeminiAccessToken()).toBeUndefined()
+})
+
diff --git a/src/utils/geminiCredentials.ts b/src/utils/geminiCredentials.ts
new file mode 100644
index 00000000..5f986a4d
--- /dev/null
+++ b/src/utils/geminiCredentials.ts
@@ -0,0 +1,76 @@
+import { isBareMode, isEnvTruthy } from './envUtils.js'
+import { getGeminiAuthMode } from './geminiAuth.js'
+import { getSecureStorage } from './secureStorage/index.js'
+
+export const GEMINI_TOKEN_STORAGE_KEY = 'gemini' as const
+
+export type GeminiCredentialBlob = {
+  accessToken: string
+}
+
+export function readGeminiAccessToken(): string | undefined {
+  if (isBareMode()) return undefined
+  try {
+    const data = getSecureStorage().read() as
+      | ({ gemini?: GeminiCredentialBlob } & Record<string, unknown>)
+      | null
+    const token = data?.gemini?.accessToken?.trim()
+    return token || undefined
+  } catch {
+    return undefined
+  }
+}
+
+export function hydrateGeminiAccessTokenFromSecureStorage(): void {
+  if (!isEnvTruthy(process.env.CLAUDE_CODE_USE_GEMINI)) {
+    return
+  }
+  const authMode = getGeminiAuthMode(process.env)
+  if (authMode && authMode !== 'access-token') {
+    return
+  }
+  if (process.env.GEMINI_ACCESS_TOKEN?.trim()) {
+    return
+  }
+  if (isBareMode()) {
+    return
+  }
+  const token = readGeminiAccessToken()
+  if (token) {
+    process.env.GEMINI_ACCESS_TOKEN = token
+  }
+}
+
+export function saveGeminiAccessToken(token: string): {
+  success: boolean
+  warning?: string
+} {
+  if (isBareMode()) {
+    return { success: false, warning: 'Bare mode: secure storage is disabled.' }
+  }
+  const trimmed = token.trim()
+  if (!trimmed) {
+    return { success: false, warning: 'Token is empty.' }
+  }
+  const secureStorage = getSecureStorage()
+  const previous = secureStorage.read() || {}
+  const next = {
+    ...(previous as Record<string, unknown>),
+    [GEMINI_TOKEN_STORAGE_KEY]: { accessToken: trimmed },
+  }
+  return secureStorage.update(next as typeof previous)
+}
+
+export function clearGeminiAccessToken(): {
+  success: boolean
+  warning?: string
+} {
+  if (isBareMode()) {
+    return { success: true }
+  }
+  const secureStorage = getSecureStorage()
+  const previous = secureStorage.read() || {}
+  const next = { ...(previous as Record<string, unknown>) }
+  delete next[GEMINI_TOKEN_STORAGE_KEY]
+  return secureStorage.update(next as typeof previous)
+}
diff --git a/src/utils/providerProfile.test.ts b/src/utils/providerProfile.test.ts
index 44f8cf94..e1da62c7 100644
--- a/src/utils/providerProfile.test.ts
+++ b/src/utils/providerProfile.test.ts
@@ -355,11 +355,38 @@ test('gemini profiles accept google api key fallback', () => {
   })
 
   assert.deepEqual(env, {
+    GEMINI_AUTH_MODE: 'api-key',
     GEMINI_MODEL: 'gemini-2.0-flash',
     GEMINI_API_KEY: 'gem-live',
   })
 })
 
+test('gemini profiles support access-token auth mode without persisting a key', () => {
+  const env = buildGeminiProfileEnv({
+    authMode: 'access-token',
+    model: 'gemini-2.5-flash',
+    processEnv: {},
+  })
+
+  assert.deepEqual(env, {
+    GEMINI_AUTH_MODE: 'access-token',
+    GEMINI_MODEL: 'gemini-2.5-flash',
+  })
+})
+
+test('gemini profiles support adc auth mode without persisting a key', () => {
+  const env = buildGeminiProfileEnv({
+    authMode: 'adc',
+    model: 'gemini-2.5-flash',
+    processEnv: {},
+  })
+
+  assert.deepEqual(env, {
+    GEMINI_AUTH_MODE: 'adc',
+    GEMINI_MODEL: 'gemini-2.5-flash',
+  })
+})
+
 test('gemini profiles require a key', () => {
   const env = buildGeminiProfileEnv({
     processEnv: {},
@@ -405,6 +432,39 @@ test('buildStartupEnvFromProfile applies persisted gemini settings when no provi
   assert.equal(env.GEMINI_MODEL, 'gemini-2.5-flash')
 })
 
+test('buildStartupEnvFromProfile rehydrates stored Gemini access token for access-token profile mode', async () => {
+  const env = await buildStartupEnvFromProfile({
+    persisted: profile('gemini', {
+      GEMINI_AUTH_MODE: 'access-token',
+      GEMINI_MODEL: 'gemini-2.5-flash',
+    }),
+    processEnv: {},
+    readGeminiAccessToken: () => 'token-live',
+  })
+
+  assert.equal(env.CLAUDE_CODE_USE_GEMINI, '1')
+  assert.equal(env.GEMINI_AUTH_MODE, 'access-token')
+  assert.equal(env.GEMINI_ACCESS_TOKEN, 'token-live')
+  assert.equal(env.GEMINI_API_KEY, undefined)
+  assert.equal(env.GEMINI_MODEL, 'gemini-2.5-flash')
+})
+
+test('buildStartupEnvFromProfile does not inject stored access token for adc profile mode', async () => {
+  const env = await buildStartupEnvFromProfile({
+    persisted: profile('gemini', {
+      GEMINI_AUTH_MODE: 'adc',
+      GEMINI_MODEL: 'gemini-2.5-flash',
+    }),
+    processEnv: {},
+    readGeminiAccessToken: () => 'token-live',
+  })
+
+  assert.equal(env.CLAUDE_CODE_USE_GEMINI, '1')
+  assert.equal(env.GEMINI_AUTH_MODE, 'adc')
+  assert.equal(env.GEMINI_ACCESS_TOKEN, undefined)
+  assert.equal(env.GEMINI_API_KEY, undefined)
+})
+
 test('buildStartupEnvFromProfile leaves explicit provider selections untouched', async () => {
   const processEnv = {
     CLAUDE_CODE_USE_GEMINI: '1',
diff --git a/src/utils/providerProfile.ts b/src/utils/providerProfile.ts
index 42da7412..6a61a758 100644
--- a/src/utils/providerProfile.ts
+++ b/src/utils/providerProfile.ts
@@ -12,6 +12,7 @@ import {
   normalizeRecommendationGoal,
   type RecommendationGoal,
 } from './providerRecommendation.ts'
+import { readGeminiAccessToken } from './geminiCredentials.ts'
 import { getOllamaChatBaseUrl } from './providerDiscovery.ts'
 
 export const PROFILE_FILE_NAME = '.openclaude-profile.json'
@@ -32,6 +33,8 @@ const PROFILE_ENV_KEYS = [
   'CHATGPT_ACCOUNT_ID',
   'CODEX_ACCOUNT_ID',
   'GEMINI_API_KEY',
+  'GEMINI_AUTH_MODE',
+  'GEMINI_ACCESS_TOKEN',
   'GEMINI_MODEL',
   'GEMINI_BASE_URL',
   'GOOGLE_API_KEY',
@@ -54,6 +57,7 @@ export type ProfileEnv = {
   CHATGPT_ACCOUNT_ID?: string
   CODEX_ACCOUNT_ID?: string
   GEMINI_API_KEY?: string
+  GEMINI_AUTH_MODE?: 'api-key' | 'access-token' | 'adc'
   GEMINI_MODEL?: string
   GEMINI_BASE_URL?: string
 }
@@ -220,19 +224,22 @@ export function buildGeminiProfileEnv(options: {
   model?: string | null
   baseUrl?: string | null
   apiKey?: string | null
+  authMode?: 'api-key' | 'access-token' | 'adc'
   processEnv?: NodeJS.ProcessEnv
 }): ProfileEnv | null {
   const processEnv = options.processEnv ?? process.env
+  const authMode = options.authMode ?? 'api-key'
   const key = sanitizeApiKey(
     options.apiKey ??
       processEnv.GEMINI_API_KEY ??
       processEnv.GOOGLE_API_KEY,
   )
-  if (!key) {
+  if (authMode === 'api-key' && !key) {
     return null
   }
 
   const env: ProfileEnv = {
+    GEMINI_AUTH_MODE: authMode,
     GEMINI_MODEL:
       sanitizeProviderConfigValue(options.model, { GEMINI_API_KEY: key }, processEnv) ||
       sanitizeProviderConfigValue(
@@ -241,7 +248,10 @@ export function buildGeminiProfileEnv(options: {
         processEnv,
       ) ||
       DEFAULT_GEMINI_MODEL,
-    GEMINI_API_KEY: key,
+  }
+
+  if (authMode === 'api-key' && key) {
+    env.GEMINI_API_KEY = key
   }
 
   const baseUrl =
@@ -422,6 +432,7 @@ export async function buildLaunchEnv(options: {
   resolveOllamaDefaultModel?: (goal: RecommendationGoal) => Promise<string>
   getAtomicChatChatBaseUrl?: (baseUrl?: string) => string
   resolveAtomicChatDefaultModel?: () => Promise<string | null>
+  readGeminiAccessToken?: () => string | undefined
 }): Promise<NodeJS.ProcessEnv> {
   const processEnv = options.processEnv ?? process.env
   const persistedEnv =
@@ -460,11 +471,16 @@ export async function buildLaunchEnv(options: {
     processEnv.GEMINI_BASE_URL,
     processEnv,
   )
+  const shellGeminiAccessToken =
+    processEnv.GEMINI_ACCESS_TOKEN?.trim() || undefined
+  const storedGeminiAccessToken =
+    options.readGeminiAccessToken?.() ?? readGeminiAccessToken()
 
   const shellGeminiKey = sanitizeApiKey(
     processEnv.GEMINI_API_KEY ?? processEnv.GOOGLE_API_KEY,
   )
   const persistedGeminiKey = sanitizeApiKey(persistedEnv.GEMINI_API_KEY)
+  const persistedGeminiAuthMode = persistedEnv.GEMINI_AUTH_MODE
 
   if (options.profile === 'gemini') {
     const env: NodeJS.ProcessEnv = {
@@ -484,12 +500,29 @@ export async function buildLaunchEnv(options: {
       persistedGeminiBaseUrl ||
       DEFAULT_GEMINI_BASE_URL
 
+    const geminiAuthMode =
+      persistedGeminiAuthMode === 'access-token' ||
+      persistedGeminiAuthMode === 'adc'
+        ? persistedGeminiAuthMode
+        : 'api-key'
     const geminiKey = shellGeminiKey || persistedGeminiKey
-    if (geminiKey) {
+    if (geminiAuthMode === 'api-key' && geminiKey) {
       env.GEMINI_API_KEY = geminiKey
     } else {
       delete env.GEMINI_API_KEY
     }
+    env.GEMINI_AUTH_MODE = geminiAuthMode
+    if (geminiAuthMode === 'access-token') {
+      const geminiAccessToken =
+        shellGeminiAccessToken || storedGeminiAccessToken
+      if (geminiAccessToken) {
+        env.GEMINI_ACCESS_TOKEN = geminiAccessToken
+      } else {
+        delete env.GEMINI_ACCESS_TOKEN
+      }
+    } else {
+      delete env.GEMINI_ACCESS_TOKEN
+    }
 
     delete env.GOOGLE_API_KEY
     delete env.OPENAI_BASE_URL
@@ -510,6 +543,8 @@ export async function buildLaunchEnv(options: {
   delete env.CLAUDE_CODE_USE_GEMINI
   delete env.CLAUDE_CODE_USE_GITHUB
   delete env.GEMINI_API_KEY
+  delete env.GEMINI_AUTH_MODE
+  delete env.GEMINI_ACCESS_TOKEN
   delete env.GEMINI_MODEL
   delete env.GEMINI_BASE_URL
   delete env.GOOGLE_API_KEY
@@ -624,6 +659,7 @@ export async function buildStartupEnvFromProfile(options?: {
   processEnv?: NodeJS.ProcessEnv
   getOllamaChatBaseUrl?: (baseUrl?: string) => string
   resolveOllamaDefaultModel?: (goal: RecommendationGoal) => Promise<string>
+  readGeminiAccessToken?: () => string | undefined
 }): Promise<NodeJS.ProcessEnv> {
   const processEnv = options?.processEnv ?? process.env
   if (hasExplicitProviderSelection(processEnv)) {
@@ -645,6 +681,7 @@ export async function buildStartupEnvFromProfile(options?: {
     getOllamaChatBaseUrl:
       options?.getOllamaChatBaseUrl ?? getOllamaChatBaseUrl,
     resolveOllamaDefaultModel: options?.resolveOllamaDefaultModel,
+    readGeminiAccessToken: options?.readGeminiAccessToken,
   })
 }
 
diff --git a/src/utils/providerValidation.test.ts b/src/utils/providerValidation.test.ts
new file mode 100644
index 00000000..3917638f
--- /dev/null
+++ b/src/utils/providerValidation.test.ts
@@ -0,0 +1,73 @@
+import { afterEach, expect, test } from 'bun:test'
+
+import { getProviderValidationError } from './providerValidation.ts'
+
+const originalEnv = {
+  CLAUDE_CODE_USE_GEMINI: process.env.CLAUDE_CODE_USE_GEMINI,
+  GEMINI_API_KEY: process.env.GEMINI_API_KEY,
+  GOOGLE_API_KEY: process.env.GOOGLE_API_KEY,
+  GEMINI_ACCESS_TOKEN: process.env.GEMINI_ACCESS_TOKEN,
+  GEMINI_AUTH_MODE: process.env.GEMINI_AUTH_MODE,
+  GOOGLE_APPLICATION_CREDENTIALS: process.env.GOOGLE_APPLICATION_CREDENTIALS,
+}
+
+function restoreEnv(key: string, value: string | undefined): void {
+  if (value === undefined) {
+    delete process.env[key]
+  } else {
+    process.env[key] = value
+  }
+}
+
+afterEach(() => {
+  restoreEnv('CLAUDE_CODE_USE_GEMINI', originalEnv.CLAUDE_CODE_USE_GEMINI)
+  restoreEnv('GEMINI_API_KEY', originalEnv.GEMINI_API_KEY)
+  restoreEnv('GOOGLE_API_KEY', originalEnv.GOOGLE_API_KEY)
+  restoreEnv('GEMINI_ACCESS_TOKEN', originalEnv.GEMINI_ACCESS_TOKEN)
+  restoreEnv('GEMINI_AUTH_MODE', originalEnv.GEMINI_AUTH_MODE)
+  restoreEnv(
+    'GOOGLE_APPLICATION_CREDENTIALS',
+    originalEnv.GOOGLE_APPLICATION_CREDENTIALS,
+  )
+})
+
+test('accepts GEMINI_ACCESS_TOKEN as valid Gemini auth', async () => {
+  process.env.CLAUDE_CODE_USE_GEMINI = '1'
+  process.env.GEMINI_AUTH_MODE = 'access-token'
+  delete process.env.GEMINI_API_KEY
+  delete process.env.GOOGLE_API_KEY
+  process.env.GEMINI_ACCESS_TOKEN = 'token-123'
+
+  await expect(getProviderValidationError(process.env)).resolves.toBeNull()
+})
+
+test('accepts ADC credentials for Gemini auth', async () => {
+  process.env.CLAUDE_CODE_USE_GEMINI = '1'
+  process.env.GEMINI_AUTH_MODE = 'adc'
+  delete process.env.GEMINI_API_KEY
+  delete process.env.GOOGLE_API_KEY
+  delete process.env.GEMINI_ACCESS_TOKEN
+
+  await expect(
+    getProviderValidationError(process.env, {
+      resolveGeminiCredential: async () => ({
+        kind: 'adc',
+        credential: 'adc-token',
+        projectId: 'adc-project',
+      }),
+    }),
+  ).resolves.toBeNull()
+})
+
+test('still errors when no Gemini credential source is available', async () => {
+  process.env.CLAUDE_CODE_USE_GEMINI = '1'
+  process.env.GEMINI_AUTH_MODE = 'access-token'
+  delete process.env.GEMINI_API_KEY
+  delete process.env.GOOGLE_API_KEY
+  delete process.env.GEMINI_ACCESS_TOKEN
+  delete process.env.GOOGLE_APPLICATION_CREDENTIALS
+
+  await expect(getProviderValidationError(process.env)).resolves.toBe(
+    'GEMINI_API_KEY, GOOGLE_API_KEY, GEMINI_ACCESS_TOKEN, or Google ADC credentials are required when CLAUDE_CODE_USE_GEMINI=1.',
+  )
+})
diff --git a/src/utils/providerValidation.ts b/src/utils/providerValidation.ts
new file mode 100644
index 00000000..a24ccf76
--- /dev/null
+++ b/src/utils/providerValidation.ts
@@ -0,0 +1,96 @@
+import {
+  isLocalProviderUrl,
+  resolveCodexApiCredentials,
+  resolveProviderRequest,
+} from '../services/api/providerConfig.js'
+import {
+  type GeminiResolvedCredential,
+  resolveGeminiCredential,
+} from './geminiAuth.js'
+import { redactSecretValueForDisplay } from './providerProfile.js'
+
+function isEnvTruthy(value: string | undefined): boolean {
+  if (!value) return false
+  const normalized = value.trim().toLowerCase()
+  return normalized !== '' && normalized !== '0' && normalized !== 'false' && normalized !== 'no'
+}
+
+export async function getProviderValidationError(
+  env: NodeJS.ProcessEnv = process.env,
+  options?: {
+    resolveGeminiCredential?: (
+      env: NodeJS.ProcessEnv,
+    ) => Promise<GeminiResolvedCredential>
+  },
+): Promise<string | null> {
+  const useOpenAI = isEnvTruthy(env.CLAUDE_CODE_USE_OPENAI)
+  const useGithub = isEnvTruthy(env.CLAUDE_CODE_USE_GITHUB)
+
+  if (isEnvTruthy(env.CLAUDE_CODE_USE_GEMINI)) {
+    const geminiCredential = await (
+      options?.resolveGeminiCredential ?? resolveGeminiCredential
+    )(env)
+    if (geminiCredential.kind === 'none') {
+      return 'GEMINI_API_KEY, GOOGLE_API_KEY, GEMINI_ACCESS_TOKEN, or Google ADC credentials are required when CLAUDE_CODE_USE_GEMINI=1.'
+    }
+    return null
+  }
+
+  if (useGithub && !useOpenAI) {
+    const token = (env.GITHUB_TOKEN?.trim() || env.GH_TOKEN?.trim()) ?? ''
+    if (!token) {
+      return 'GITHUB_TOKEN or GH_TOKEN is required when CLAUDE_CODE_USE_GITHUB=1.'
+    }
+    return null
+  }
+
+  if (!useOpenAI) {
+    return null
+  }
+
+  const request = resolveProviderRequest({
+    model: env.OPENAI_MODEL,
+    baseUrl: env.OPENAI_BASE_URL,
+  })
+
+  if (env.OPENAI_API_KEY === 'SUA_CHAVE') {
+    return 'Invalid OPENAI_API_KEY: placeholder value SUA_CHAVE detected. Set a real key or unset for local providers.'
+  }
+
+  if (request.transport === 'codex_responses') {
+    const credentials = resolveCodexApiCredentials(env)
+    if (!credentials.apiKey) {
+      const authHint = credentials.authPath
+        ? ` or put auth.json at ${credentials.authPath}`
+        : ''
+      const safeModel =
+        redactSecretValueForDisplay(request.requestedModel, env) ??
+        'the requested model'
+      return `Codex auth is required for ${safeModel}. Set CODEX_API_KEY${authHint}.`
+    }
+    if (!credentials.accountId) {
+      return 'Codex auth is missing chatgpt_account_id. Re-login with Codex or set CHATGPT_ACCOUNT_ID/CODEX_ACCOUNT_ID.'
+    }
+    return null
+  }
+
+  if (!env.OPENAI_API_KEY && !isLocalProviderUrl(request.baseUrl)) {
+    const hasGithubToken = !!(env.GITHUB_TOKEN?.trim() || env.GH_TOKEN?.trim())
+    if (useGithub && hasGithubToken) {
+      return null
+    }
+    return 'OPENAI_API_KEY is required when CLAUDE_CODE_USE_OPENAI=1 and OPENAI_BASE_URL is not local.'
+  }
+
+  return null
+}
+
+export async function validateProviderEnvOrExit(
+  env: NodeJS.ProcessEnv = process.env,
+): Promise<void> {
+  const error = await getProviderValidationError(env)
+  if (error) {
+    console.error(error)
+    process.exit(1)
+  }
+}
diff --git a/src/utils/secureStorage/platformStorage.test.ts b/src/utils/secureStorage/platformStorage.test.ts
index eb68edd1..059e2035 100644
--- a/src/utils/secureStorage/platformStorage.test.ts
+++ b/src/utils/secureStorage/platformStorage.test.ts
@@ -25,24 +25,24 @@ describe("Secure Storage Platform Implementations", () => {
     process.env = originalEnv;
   });
 
-  const testData = { 
-    mcpOAuth: { 
-      "test-server": { 
-        accessToken: "secret-token", 
-        expiresAt: 123456789, 
-        serverName: "test", 
-        serverUrl: "http://test" 
-      } 
-    } 
+  const testData = {
+    mcpOAuth: {
+      "test-server": {
+        accessToken: "secret-token",
+        expiresAt: 123456789,
+        serverName: "test",
+        serverUrl: "http://test"
+      }
+    }
   };
 
   describe("Config-Dir Isolation", () => {
     test("service name changes with CLAUDE_CONFIG_DIR", () => {
       const defaultName = getSecureStorageServiceName(CREDENTIALS_SERVICE_SUFFIX);
-      
+
       process.env.CLAUDE_CONFIG_DIR = "/tmp/other-config";
       const otherName = getSecureStorageServiceName(CREDENTIALS_SERVICE_SUFFIX);
-      
+
       expect(otherName).not.toBe(defaultName);
       expect(otherName).toContain("Claude Code");
       expect(otherName).toContain(CREDENTIALS_SERVICE_SUFFIX);
@@ -51,9 +51,9 @@ describe("Secure Storage Platform Implementations", () => {
     test("Linux storage uses scoped service name", () => {
       process.env.CLAUDE_CONFIG_DIR = "/tmp/linux-scoped";
       const expectedName = getSecureStorageServiceName(CREDENTIALS_SERVICE_SUFFIX);
-      
+
       linuxSecretStorage.update(testData);
-      
+
       const args = mockExecaSync.mock.calls[0];
       expect(args[1]).toContain(expectedName);
     });
@@ -61,9 +61,9 @@ describe("Secure Storage Platform Implementations", () => {
     test("Windows storage uses scoped resource name", () => {
       process.env.CLAUDE_CONFIG_DIR = "/tmp/win-scoped";
       const expectedName = getSecureStorageServiceName(CREDENTIALS_SERVICE_SUFFIX);
-      
+
       windowsCredentialStorage.update(testData);
-      
+
       const script = mockExecaSync.mock.calls[0][1][1];
       expect(script).toContain(expectedName);
       expect(script).toContain("Add-Type -AssemblyName System.Runtime.WindowsRuntime");
@@ -72,19 +72,19 @@ describe("Secure Storage Platform Implementations", () => {
 
   describe("Windows PowerShell Escaping", () => {
     test("escapes single quotes and prevents $ expansion", () => {
-      const dataWithDollar = { 
-        mcpOAuth: { 
-          "server": { 
+      const dataWithDollar = {
+        mcpOAuth: {
+          "server": {
             accessToken: "token-with-$env:USERNAME",
             expiresAt: 123,
             serverName: "s",
             serverUrl: "u"
-          } 
-        } 
+          }
+        }
       };
-      
+
       windowsCredentialStorage.update(dataWithDollar);
-      
+
       const script = mockExecaSync.mock.calls[0][1][1];
       // Should use single quotes for the payload
       expect(script).toMatch(/'\{.*\}'/);
@@ -92,7 +92,7 @@ describe("Secure Storage Platform Implementations", () => {
       expect(script).not.toContain("'token-with-$env:USERNAME'");
       // But since it's JSON, the value will be "token-with-$env:USERNAME" inside the single-quoted string
       // The JSON itself shouldn't have single quotes unless the data has them.
-      
+
       const dataWithQuote = { mcpOAuth: { "s": { accessToken: "token'quote", expiresAt: 1, serverName: "s", serverUrl: "u" } } };
       windowsCredentialStorage.update(dataWithQuote);
       const script2 = mockExecaSync.mock.calls[1][1][1];
@@ -117,7 +117,7 @@ describe("Secure Storage Platform Implementations", () => {
   describe("Linux secret-tool Interaction", () => {
     test("update passes payload via stdin", () => {
       linuxSecretStorage.update(testData);
-      
+
       const options = mockExecaSync.mock.calls[0][2];
       expect(options.input).toContain("secret-token");
     });
@@ -125,7 +125,7 @@ describe("Secure Storage Platform Implementations", () => {
     test("read parses stdout", () => {
       mockExecaSync.mockReturnValue({ exitCode: 0, stdout: JSON.stringify(testData) });
       const result = linuxSecretStorage.read();
-      
+
       expect(result).toEqual(testData);
     });
   });