diff --git a/src/components/providers/utils.ts b/src/components/providers/utils.ts
index f45f41e..5221472 100644
--- a/src/components/providers/utils.ts
+++ b/src/components/providers/utils.ts
@@ -63,6 +63,21 @@ export const buildOpenAIChatCompletionsEndpoint = (baseUrl: string): string => {
   return `${trimmed}/chat/completions`;
 };
 
+export const buildCodexResponsesEndpoint = (baseUrl: string): string => {
+  const trimmed = normalizeUpstreamBaseUrl(baseUrl);
+  if (!trimmed) return '';
+  if (/\/v1\/responses$/i.test(trimmed)) {
+    return trimmed;
+  }
+  if (/\/v1\/models$/i.test(trimmed)) {
+    return trimmed.replace(/\/models$/i, '/responses');
+  }
+  if (/\/v1$/i.test(trimmed)) {
+    return `${trimmed}/responses`;
+  }
+  return `${trimmed}/v1/responses`;
+};
+
 export const buildClaudeMessagesEndpoint = (baseUrl: string): string => {
   const trimmed = normalizeUpstreamBaseUrl(baseUrl, 'https://api.anthropic.com');
   if (!trimmed) return '';
diff --git a/src/features/providers/descriptors.ts b/src/features/providers/descriptors.ts
index 29cfab5..505e6bb 100644
--- a/src/features/providers/descriptors.ts
+++ b/src/features/providers/descriptors.ts
@@ -54,7 +54,7 @@ export const PROVIDER_DESCRIPTORS: Record<ProviderBrand, ProviderDescriptor> = {
     supportsHeaders: true,
     supportsExcludedModels: true,
     supportsPriority: true,
-    supportsTestModel: false,
+    supportsTestModel: true,
     supportsWebsockets: true,
     supportsCloak: false,
     supportsApiKeyEntries: false,
diff --git a/src/features/providers/sheets/forms/BaseProviderForm.tsx b/src/features/providers/sheets/forms/BaseProviderForm.tsx
index 5b3cecc..a5979a3 100644
--- a/src/features/providers/sheets/forms/BaseProviderForm.tsx
+++ b/src/features/providers/sheets/forms/BaseProviderForm.tsx
@@ -86,7 +86,10 @@ function buildInitialForm(
           : undefined,
       experimentalCchSigning: brand === 'claude' ? false : undefined,
       testModel:
-        brand === 'openaiCompatibility' || brand === 'claude' || brand === 'gemini'
+        brand === 'openaiCompatibility' ||
+        brand === 'codex' ||
+        brand === 'claude' ||
+        brand === 'gemini'
           ? ''
           : undefined,
       apiKeyEntries: brand === 'openaiCompatibility' ? [emptyApiKeyEntry()] : undefined,
@@ -173,7 +176,7 @@ function buildInitialForm(
       brand === 'claude'
         ? (cfg as ProviderKeyConfig).experimentalCchSigning === true
         : undefined,
-    testModel: brand === 'claude' || brand === 'gemini' ? '' : undefined,
+    testModel: brand === 'codex' || brand === 'claude' || brand === 'gemini' ? '' : undefined,
   };
 }
 
@@ -448,7 +451,9 @@ export function BaseProviderForm({
     brand === 'openaiCompatibility';
   const supportsOpenAIModelOptions = brand === 'openaiCompatibility';
   const singleConnectivity =
-    brand === 'gemini'
+    brand === 'codex'
+      ? { status: connectivity.codexStatus, run: connectivity.runCodex }
+      : brand === 'gemini'
       ? { status: connectivity.geminiStatus, run: connectivity.runGemini }
       : brand === 'claude'
         ? { status: connectivity.claudeStatus, run: connectivity.runClaude }
@@ -630,7 +635,7 @@ export function BaseProviderForm({
           <div className={styles.field}>
             <label className={styles.label} htmlFor={`${fid}-testModel`}>
               {t('providersPage.form.testModel')}
-              {brand === 'claude' || brand === 'gemini' ? (
+              {brand === 'codex' || brand === 'claude' || brand === 'gemini' ? (
                 <span className={styles.labelHint}>
                   {' '}
                   · {t('providersPage.form.testModelClaudeHint')}
diff --git a/src/features/providers/sheets/forms/useConnectivityTest.ts b/src/features/providers/sheets/forms/useConnectivityTest.ts
index 0eb4ad3..dbe60ba 100644
--- a/src/features/providers/sheets/forms/useConnectivityTest.ts
+++ b/src/features/providers/sheets/forms/useConnectivityTest.ts
@@ -1,6 +1,7 @@
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import { apiCallApi, getApiCallErrorMessage } from '@/services/api';
 import {
+  buildCodexResponsesEndpoint,
   buildClaudeMessagesEndpoint,
   buildGeminiGenerateContentEndpoint,
   buildOpenAIChatCompletionsEndpoint,
@@ -73,11 +74,13 @@ export interface ConnectivityErrorMessages {
 
 export interface UseConnectivityTestResult {
   openaiStatuses: ConnectivityStatus[];
+  codexStatus: ConnectivityStatus;
   geminiStatus: ConnectivityStatus;
   claudeStatus: ConnectivityStatus;
   isTestingAny: boolean;
   runOpenAIKey: (idx: number) => Promise<boolean>;
   runOpenAIAllKeys: () => Promise<void>;
+  runCodex: () => Promise<void>;
   runGemini: () => Promise<void>;
   runClaude: () => Promise<void>;
 }
@@ -103,6 +106,7 @@ export function useConnectivityTest(
   const [openaiStatuses, setOpenaiStatuses] = useState<ConnectivityStatus[]>(() =>
     Array.from({ length: entriesCount }, () => IDLE)
   );
+  const [codexStatus, setCodexStatus] = useState<ConnectivityStatus>(IDLE);
   const [geminiStatus, setGeminiStatus] = useState<ConnectivityStatus>(IDLE);
   const [claudeStatus, setClaudeStatus] = useState<ConnectivityStatus>(IDLE);
   const [inFlight, setInFlight] = useState(0);
@@ -160,6 +164,7 @@ export function useConnectivityTest(
     if (lastSignatureRef.current === signature) return;
     lastSignatureRef.current = signature;
     setOpenaiStatuses((prev) => prev.map(() => IDLE));
+    setCodexStatus(IDLE);
     setGeminiStatus(IDLE);
     setClaudeStatus(IDLE);
   }, [signature]);
@@ -277,6 +282,82 @@ export function useConnectivityTest(
     await Promise.all(entries.map((_, idx) => runOpenAIKey(idx)));
   }, [apiKeyEntries, brand, runOpenAIKey]);
 
+  const runCodex = useCallback(async (): Promise<void> => {
+    if (brand !== 'codex') return;
+
+    const trimmedBase = baseUrl.trim();
+    if (!trimmedBase) {
+      setCodexStatus({ state: 'error', message: messages.baseUrlRequired });
+      return;
+    }
+
+    const endpoint = buildCodexResponsesEndpoint(trimmedBase);
+    if (!endpoint) {
+      setCodexStatus({ state: 'error', message: messages.endpointInvalid });
+      return;
+    }
+
+    const model = pickModel(testModel, models);
+    if (!model) {
+      setCodexStatus({ state: 'error', message: messages.modelRequired });
+      return;
+    }
+
+    const customHeaders = buildHeaderObject(formHeaders);
+    const explicitKey = (apiKey ?? '').trim();
+    const persistedKey = (fallbackApiKey ?? '').trim();
+    const hasAuthorization = hasHeader(customHeaders, 'authorization');
+    const resolvedKey = explicitKey || persistedKey;
+    const resolvedAuthIndex = (authIndex ?? '').trim() || undefined;
+
+    if (!resolvedKey && !hasAuthorization && !resolvedAuthIndex) {
+      setCodexStatus({ state: 'error', message: messages.apiKeyRequired });
+      return;
+    }
+
+    const headerObj: Record<string, string> = {
+      'Content-Type': 'application/json',
+      ...customHeaders,
+    };
+    if (!hasHeader(headerObj, 'authorization')) {
+      if (resolvedKey) {
+        headerObj.Authorization = `Bearer ${resolvedKey}`;
+      } else if (resolvedAuthIndex) {
+        headerObj.Authorization = 'Bearer $TOKEN$';
+      }
+    }
+
+    setCodexStatus({ state: 'loading', message: '' });
+    setInFlight((n) => n + 1);
+    try {
+      const result = await apiCallApi.request(
+        {
+          authIndex: resolvedAuthIndex,
+          method: 'POST',
+          url: endpoint,
+          header: headerObj,
+          data: JSON.stringify({
+            model,
+            input: 'Hi',
+            stream: false,
+          }),
+        },
+        { timeout: DEFAULT_TIMEOUT_MS }
+      );
+      if (result.statusCode < 200 || result.statusCode >= 300) {
+        throw new Error(getApiCallErrorMessage(result));
+      }
+      setCodexStatus({ state: 'success', message: '' });
+    } catch (err) {
+      setCodexStatus({
+        state: 'error',
+        message: requestFailureMessage(err, messages),
+      });
+    } finally {
+      setInFlight((n) => n - 1);
+    }
+  }, [apiKey, authIndex, baseUrl, brand, fallbackApiKey, formHeaders, messages, models, testModel]);
+
   const runGemini = useCallback(async (): Promise<void> => {
     if (brand !== 'gemini') return;
 
@@ -419,11 +500,13 @@ export function useConnectivityTest(
 
   return {
     openaiStatuses,
+    codexStatus,
     geminiStatus,
     claudeStatus,
     isTestingAny: inFlight > 0,
     runOpenAIKey,
     runOpenAIAllKeys,
+    runCodex,
     runGemini,
     runClaude,
   };