fix(env): strip null bytes from .env before python-dotenv loads

Null bytes in API key values (introduced by copy-paste) crash
    os.environ[k] = v with ValueError: embedded null byte, preventing
    hermes from starting at all.

hermes_cli/env_loader.py

@@ -140,6 +140,10 @@ def _sanitize_env_file_if_needed(path: Path) -> None:
     This produces mangled values — e.g. a bot token duplicated 8×
     (see #8908).
 
+    Also strips embedded null bytes which crash ``os.environ[k] = v``
+    with ``ValueError: embedded null byte`` — typically introduced by
+    copy-pasting API keys from terminals or rich-text editors.
+
     We delegate to ``hermes_cli.config._sanitize_env_lines`` which
     already knows all valid Hermes env-var names and can split
     concatenated lines correctly.
@@ -155,7 +159,11 @@ def _sanitize_env_file_if_needed(path: Path) -> None:
     try:
         with open(path, **read_kw) as f:
             original = f.readlines()
-        sanitized = _sanitize_env_lines(original)
+        # Strip null bytes before _sanitize_env_lines so they never
+        # reach python-dotenv (which passes them to os.environ and
+        # crashes with ValueError).
+        stripped = [line.replace("\x00", "") for line in original]
+        sanitized = _sanitize_env_lines(stripped)
         if sanitized != original:
             import tempfile
             fd, tmp = tempfile.mkstemp(

tests/hermes_cli/test_env_loader.py

@@ -70,6 +70,23 @@ def test_user_env_takes_precedence_over_project_env(tmp_path, monkeypatch):
     assert os.getenv("OPENAI_API_KEY") == "project-key"
 
 
+def test_null_bytes_in_user_env_are_stripped(tmp_path, monkeypatch):
+    home = tmp_path / "hermes"
+    home.mkdir()
+    env_file = home / ".env"
+    # Null bytes can be introduced when copy-pasting API keys.
+    env_file.write_text("GLM_API_KEY=abc\x00\x00\nOPENAI_API_KEY=sk-123\n", encoding="utf-8")
+
+    monkeypatch.delenv("GLM_API_KEY", raising=False)
+    monkeypatch.delenv("OPENAI_API_KEY", raising=False)
+
+    loaded = load_hermes_dotenv(hermes_home=home)
+
+    assert loaded == [env_file]
+    assert os.getenv("GLM_API_KEY") == "abc"
+    assert os.getenv("OPENAI_API_KEY") == "sk-123"
+
+
 def test_main_import_applies_user_env_over_shell_values(tmp_path, monkeypatch):
     home = tmp_path / "hermes"
     home.mkdir()