diff --git a/codex/SKILL.md b/codex/SKILL.md
index 3cbb7850..df8f69ce 100644
--- a/codex/SKILL.md
+++ b/codex/SKILL.md
@@ -424,8 +424,8 @@ If token count is not available, display: `Tokens: unknown`
 ## Error Handling
 
 - **Binary not found:** Detected in Step 0. Stop with install instructions.
-- **API key missing:** Codex prints an auth error to stderr. Surface the error:
-  "Codex authentication failed. Set OPENAI_API_KEY in your environment."
+- **Auth error:** Codex prints an auth error to stderr. Surface the error:
+  "Codex authentication failed. Run `codex login` in your terminal to authenticate via ChatGPT."
 - **Timeout:** If the Bash call times out (5 min), tell the user:
   "Codex timed out after 5 minutes. The diff may be too large or the API may be slow. Try again or use a smaller scope."
 - **Empty response:** If `$TMPRESP` is empty or doesn't exist, tell the user:
diff --git a/codex/SKILL.md.tmpl b/codex/SKILL.md.tmpl
index ffa0f684..ea02612c 100644
--- a/codex/SKILL.md.tmpl
+++ b/codex/SKILL.md.tmpl
@@ -278,8 +278,8 @@ If token count is not available, display: `Tokens: unknown`
 ## Error Handling
 
 - **Binary not found:** Detected in Step 0. Stop with install instructions.
-- **API key missing:** Codex prints an auth error to stderr. Surface the error:
-  "Codex authentication failed. Set OPENAI_API_KEY in your environment."
+- **Auth error:** Codex prints an auth error to stderr. Surface the error:
+  "Codex authentication failed. Run `codex login` in your terminal to authenticate via ChatGPT."
 - **Timeout:** If the Bash call times out (5 min), tell the user:
   "Codex timed out after 5 minutes. The diff may be too large or the API may be slow. Try again or use a smaller scope."
 - **Empty response:** If `$TMPRESP` is empty or doesn't exist, tell the user:
diff --git a/test/skill-validation.test.ts b/test/skill-validation.test.ts
index 422e4932..118158d6 100644
--- a/test/skill-validation.test.ts
+++ b/test/skill-validation.test.ts
@@ -1176,10 +1176,10 @@ describe('Codex skill', () => {
     expect(content).not.toContain('/opt/homebrew/bin/codex');
   });
 
-  test('codex/SKILL.md contains error handling for missing binary and API key', () => {
+  test('codex/SKILL.md contains error handling for missing binary and auth', () => {
     const content = fs.readFileSync(path.join(ROOT, 'codex', 'SKILL.md'), 'utf-8');
     expect(content).toContain('NOT_FOUND');
-    expect(content).toContain('OPENAI_API_KEY');
+    expect(content).toContain('codex login');
   });
 
   test('codex/SKILL.md uses mktemp for temp files', () => {