fix: stop pinning o4-mini in codex config

tests/codex-config.test.js

@@ -0,0 +1,70 @@
+/**
+ * Tests for `.codex/config.toml` reference defaults.
+ *
+ * Run with: node tests/codex-config.test.js
+ */
+
+const assert = require('assert');
+const fs = require('fs');
+const path = require('path');
+
+function test(name, fn) {
+  try {
+    fn();
+    console.log(`  ✓ ${name}`);
+    return true;
+  } catch (err) {
+    console.log(`  ✗ ${name}`);
+    console.log(`    Error: ${err.message}`);
+    return false;
+  }
+}
+
+const repoRoot = path.join(__dirname, '..');
+const configPath = path.join(repoRoot, '.codex', 'config.toml');
+const config = fs.readFileSync(configPath, 'utf8');
+const codexAgentsDir = path.join(repoRoot, '.codex', 'agents');
+
+let passed = 0;
+let failed = 0;
+
+if (
+  test('reference config does not pin a top-level model', () => {
+    assert.ok(!/^model\s*=/m.test(config), 'Expected `.codex/config.toml` to inherit the CLI default model');
+  })
+)
+  passed++;
+else failed++;
+
+if (
+  test('reference config does not pin a top-level model provider', () => {
+    assert.ok(
+      !/^model_provider\s*=/m.test(config),
+      'Expected `.codex/config.toml` to inherit the CLI default provider',
+    );
+  })
+)
+  passed++;
+else failed++;
+
+if (
+  test('sample Codex role configs do not use o4-mini', () => {
+    const roleFiles = fs.readdirSync(codexAgentsDir).filter(file => file.endsWith('.toml'));
+    assert.ok(roleFiles.length > 0, 'Expected sample role config files under `.codex/agents`');
+
+    for (const roleFile of roleFiles) {
+      const rolePath = path.join(codexAgentsDir, roleFile);
+      const roleConfig = fs.readFileSync(rolePath, 'utf8');
+      assert.ok(
+        !/^model\s*=\s*"o4-mini"$/m.test(roleConfig),
+        `Expected sample role config to avoid o4-mini: ${roleFile}`,
+      );
+    }
+  })
+)
+  passed++;
+else failed++;
+
+console.log(`\nPassed: ${passed}`);
+console.log(`Failed: ${failed}`);
+process.exit(failed > 0 ? 1 : 0);