diff --git a/bin/gstack-codex-probe b/bin/gstack-codex-probe
index 96c640b7f..49bc4ad74 100755
--- a/bin/gstack-codex-probe
+++ b/bin/gstack-codex-probe
@@ -21,8 +21,9 @@
 # --- Auth probe -------------------------------------------------------------
 
 _gstack_codex_auth_probe() {
-  # Multi-signal: env vars OR auth file. Avoids false negatives for env-auth
-  # users (CI, platform engineers) that a file-only check would reject.
+  # Multi-signal: env vars OR auth file OR a custom provider's env_key. Avoids
+  # false negatives for env-auth users (CI, platform engineers, self-hosted
+  # OpenAI-compatible providers) that a file-only check would reject.
   local _codex_home="${CODEX_HOME:-$HOME/.codex}"
   # Use `-n` which returns true only for non-empty non-whitespace. Bash's [ -n ]
   # alone allows whitespace; pair with a whitespace strip for robustness.
@@ -33,7 +34,26 @@ _gstack_codex_auth_probe() {
     echo "AUTH_OK"
     return 0
   fi
+  # Custom OpenAI-compatible providers (#2192): a [model_providers.<id>]
+  # table names its credential variable in env_key. Only keys inside those
+  # tables count, comments are ignored, and the name must be a plain shell
+  # identifier before it is dereferenced.
+  local _env_key _resolved _missing=""
+  if [ -f "$_codex_home/config.toml" ]; then
+    while IFS= read -r _env_key; do
+      case "$_env_key" in ''|[0-9]*|*[!A-Za-z0-9_]*) continue ;; esac
+      _resolved=$(printf '%s' "${!_env_key:-}" | tr -d '[:space:]')
+      if [ -n "$_resolved" ]; then
+        echo "AUTH_OK"
+        return 0
+      fi
+      _missing="${_missing:+$_missing, }$_env_key"
+    done < <(awk '/^[[:space:]]*#/ { next }
+      /^[[:space:]]*\[/ { in_provider = ($0 ~ /^[[:space:]]*\[model_providers\.[^]]+\][[:space:]]*(#.*)?$/); next }
+      in_provider && /^[[:space:]]*env_key[[:space:]]*=/ { v = $0; sub(/^[^=]*=[[:space:]]*/, "", v); sub(/[[:space:]]*#.*$/, "", v); gsub(/["\047[:space:]]/, "", v); print v }' "$_codex_home/config.toml" 2>/dev/null)
+  fi
   echo "AUTH_FAILED"
+  [ -n "$_missing" ] && echo "HINT: $_codex_home/config.toml names a custom provider key ($_missing), but it is not set in this shell. Export it, or run codex login." >&2
   return 1
 }
 
diff --git a/test/codex-hardening.test.ts b/test/codex-hardening.test.ts
index f850df162..36b36fee7 100644
--- a/test/codex-hardening.test.ts
+++ b/test/codex-hardening.test.ts
@@ -51,6 +51,44 @@ function tempHome(): string {
 }
 
 describe('gstack-codex-probe: auth probe', () => {
+  // #2192: custom OpenAI-compatible providers name their credential variable
+  // in config.toml [model_providers.<id>] env_key; a set variable is auth.
+  const withConfig = (toml: string, env: Record<string, string | undefined> = {}) => {
+    const home = tempHome();
+    try {
+      fs.mkdirSync(path.join(home, '.codex'), { recursive: true });
+      fs.writeFileSync(path.join(home, '.codex', 'config.toml'), toml);
+      return runProbe({ snippet: '_gstack_codex_auth_probe', env, home });
+    } finally { fs.rmSync(home, { recursive: true, force: true }); }
+  };
+  const MIMO = '[model_providers.mimo]\nenv_key = "MIMO_API_KEY"\n';
+
+  test('#2192: a provider env_key whose variable is set → AUTH_OK', () => {
+    const r = withConfig(MIMO, { MIMO_API_KEY: 'tp-test-key' });
+    expect([r.stdout.trim(), r.status]).toEqual(['AUTH_OK', 0]);
+    const several = withConfig('[model_providers.a]\nenv_key = "MISSING_A"\n\n[model_providers.b]\nenv_key = \'MIMO_API_KEY\'  # inline comment\n', { MIMO_API_KEY: 'k' });
+    expect(several.stdout.trim()).toBe('AUTH_OK');
+  });
+
+  test('#2192: a provider env_key that is unset or blank → AUTH_FAILED naming the key', () => {
+    for (const value of [undefined, '   \t\n']) {
+      const r = withConfig(MIMO, { MIMO_API_KEY: value });
+      expect([r.stdout.trim(), r.status]).toEqual(['AUTH_FAILED', 1]);
+      expect(r.stderr).toContain('custom provider key (MIMO_API_KEY)');
+    }
+  });
+
+  test('#2192: commented env_key lines and env_key outside [model_providers.*] never count', () => {
+    const toml = '[model_providers.mimo]\n# env_key = "DEPRECATED_KEY"\nenv_key = "MIMO_API_KEY"\n[profiles.work]\nenv_key = "PROFILE_KEY"\n';
+    expect(withConfig(toml, { DEPRECATED_KEY: 'old', PROFILE_KEY: 'p' }).stdout.trim()).toBe('AUTH_FAILED');
+  });
+
+  test('#2192: malformed config.toml or a non-identifier env_key → AUTH_FAILED, no crash', () => {
+    expect(withConfig('\x00\x01 garbage \xff[broken\n=no=\n').stdout.trim()).toBe('AUTH_FAILED');
+    const injected = withConfig('[model_providers.x]\nenv_key = "A;touch /tmp/never"\n');
+    expect([injected.stdout.trim(), injected.status]).toEqual(['AUTH_FAILED', 1]);
+  });
+
   test('CODEX_API_KEY set → AUTH_OK', () => {
     const home = tempHome();
     try {