fix(tests): stop config.set model tests writing cli-config.yaml into the repo root

tests/conftest.py

@@ -402,6 +402,57 @@ def _isolate_hermes_home(_hermetic_environment):
     return None
 
 
+_REPO_ROOT_CLI_CONFIG = Path(__file__).resolve().parent.parent / "cli-config.yaml"
+
+
+@pytest.fixture(autouse=True)
+def _guard_repo_root_cli_config():
+    """Fail any test that creates or mutates ``<repo>/cli-config.yaml``.
+
+    ``cli.save_config_value()`` falls back to writing the PROJECT config —
+    ``cli-config.yaml`` next to ``cli.py``, i.e. the repo root — whenever
+    the user config (``cli._hermes_home / 'config.yaml'``) does not exist.
+    Under ``_hermetic_environment`` the per-test HERMES_HOME tempdir is
+    always empty, so any test that reaches the real ``save_config_value``
+    silently drops a ``cli-config.yaml`` into the developer's checkout.
+    The file is gitignored (invisible in ``git status``) and is then read
+    back as the project-config fallback by every later run, breaking e.g.
+    ``tests/hermes_cli/test_ignore_user_config_flags.py`` and
+    ``tests/test_hermes_state.py``.
+
+    This tripwire pins the blame on the offending test instead of letting
+    the pollution surface as unrelated failures three runs later. It also
+    restores the pre-test state so one offender can't cascade.
+    """
+    before = (
+        _REPO_ROOT_CLI_CONFIG.read_bytes()
+        if _REPO_ROOT_CLI_CONFIG.exists()
+        else None
+    )
+    yield
+    after = (
+        _REPO_ROOT_CLI_CONFIG.read_bytes()
+        if _REPO_ROOT_CLI_CONFIG.exists()
+        else None
+    )
+    if after == before:
+        return
+    # Restore first so the pollution doesn't outlive the failing test.
+    if before is None:
+        _REPO_ROOT_CLI_CONFIG.unlink()
+    else:
+        _REPO_ROOT_CLI_CONFIG.write_bytes(before)
+    pytest.fail(
+        "this test wrote to the repo-root cli-config.yaml "
+        f"({_REPO_ROOT_CLI_CONFIG}). It reached the real "
+        "cli.save_config_value() with an empty HERMES_HOME, so the write "
+        "fell through to the project-config fallback in the developer's "
+        "checkout. Point cli._hermes_home at a tmp_path containing a "
+        "config.yaml (or monkeypatch cli.save_config_value) instead. "
+        f"Written content was:\n{(after or b'').decode('utf-8', 'replace')}"
+    )
+
+
 # ── Module-level state reset — replaced by per-file process isolation ──────
 #
 # Each test FILE runs in a freshly-spawned ``python -m pytest <file>``

tests/test_tui_gateway_server.py

@@ -3338,6 +3338,10 @@ def switch_model(self, **_kwargs):
     )
     monkeypatch.setattr(server, "_restart_slash_worker", lambda sid, session: None)
     monkeypatch.setattr(server, "_emit", lambda *args, **kwargs: None)
+    # Plain /model persists globally by default; without this patch the real
+    # save_config_value() writes a cli-config.yaml into the repo root (the
+    # per-test HERMES_HOME is empty, so it falls through to project config).
+    monkeypatch.setattr("cli.save_config_value", lambda _key, _value: True)
 
     resp = server.handle_request(
         {
@@ -3436,6 +3440,9 @@ def test_config_set_model_explicit_provider_skips_broken_default_init(monkeypatc
     monkeypatch.setattr(server, "_wait_agent", lambda *_args: seen.__setitem__("wait", seen["wait"] + 1))
     monkeypatch.setattr(server, "_emit", lambda *args, **kwargs: None)
     monkeypatch.setattr(server, "_restart_slash_worker", lambda *args, **kwargs: None)
+    # Plain /model persists globally by default; keep the real
+    # save_config_value() from writing a repo-root cli-config.yaml.
+    monkeypatch.setattr("cli.save_config_value", lambda _key, _value: True)
 
     def fake_runtime_provider(*, requested=None, target_model=None, **_kwargs):
         seen["requested"].append((requested, target_model))
@@ -3552,6 +3559,9 @@ def switch_model(self, **_kwargs):
     )
     monkeypatch.setattr(server, "_restart_slash_worker", lambda sid, session: None)
     monkeypatch.setattr(server, "_emit", lambda *args, **kwargs: None)
+    # Plain /model persists globally by default; keep the real
+    # save_config_value() from writing a repo-root cli-config.yaml.
+    monkeypatch.setattr("cli.save_config_value", lambda _key, _value: True)
 
     try:
         server.handle_request(
@@ -3613,6 +3623,9 @@ def switch_model(self, **_kwargs):
     )
     monkeypatch.setattr(server, "_restart_slash_worker", lambda sid, session: None)
     monkeypatch.setattr(server, "_emit", lambda *args, **kwargs: None)
+    # Plain /model persists globally by default; keep the real
+    # save_config_value() from writing a repo-root cli-config.yaml.
+    monkeypatch.setattr("cli.save_config_value", lambda _key, _value: True)
 
     try:
         server.handle_request(
@@ -3695,6 +3708,9 @@ def append_message(self, session_id, role, content=None, **_kwargs):
     monkeypatch.delenv("HERMES_INFERENCE_MODEL", raising=False)
     monkeypatch.setattr(server, "_restart_slash_worker", lambda sid, session: None)
     monkeypatch.setattr(server, "_emit", lambda *args, **kwargs: None)
+    # Plain /model persists globally by default; keep the real
+    # save_config_value() from writing a repo-root cli-config.yaml.
+    monkeypatch.setattr("cli.save_config_value", lambda _key, _value: True)
 
     def fake_switch_model(**kwargs):
         return types.SimpleNamespace(