diff --git a/Autotests/run_mandatory b/Autotests/run_mandatory
index d93f41fb..b67e62a7 100644
--- a/Autotests/run_mandatory
+++ b/Autotests/run_mandatory
@@ -39,6 +39,7 @@ test_openai_runtime_embeddings.py
 test_prompt_grounding.py
 test_websearch_smoke.py
 test_wschat.py
+unit/test_config.py
 unit/test_fileio_verified_writes.py
 unit/test_helper_parsing.py
 unit/test_openclaw_unit.py
diff --git a/Autotests/unit/test_config.py b/Autotests/unit/test_config.py
new file mode 100644
index 00000000..acb5bec5
--- /dev/null
+++ b/Autotests/unit/test_config.py
@@ -0,0 +1,149 @@
+"""In-process unit tests for src/config.py.
+
+The configuration resolver checks command-line arguments, OMEGACLAW_<key>
+environment variables, the YAML configuration file, and finally the supplied
+default. Resolved values are cached until configuration is initialized again.
+
+No container, no network, no token — same pattern as
+unit/test_fileio_verified_writes.py: the module is loaded by file path.
+"""
+import importlib.util
+import os
+
+import pytest
+
+_REPO_ROOT = os.path.normpath(os.path.join(os.path.dirname(__file__), "..", ".."))
+_CONFIG_PATH = os.path.join(_REPO_ROOT, "src", "config.py")
+
+
+def _load_config():
+    spec = importlib.util.spec_from_file_location("config_under_test", _CONFIG_PATH)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+@pytest.fixture
+def config():
+    return _load_config()
+
+
+def test_config_module_exposes_public_api(config):
+    assert hasattr(config, "config_get_by_key")
+    assert hasattr(config, "command_line_to_dict")
+    assert hasattr(config, "init_config")
+
+
+def test_command_line_key_value_pairs(config):
+    result = config.command_line_to_dict(["provider=OpenRouter", "model=free"])
+
+    assert result == {"provider": "OpenRouter", "model": "free"}
+
+
+def test_command_line_bare_argument_becomes_true(config):
+    assert config.command_line_to_dict(["verbose"]) == {"verbose": True}
+
+
+def test_command_line_splits_on_first_equals_only(config):
+    result = config.command_line_to_dict(["url=http://host/?a=b"])
+
+    assert result == {"url": "http://host/?a=b"}
+
+
+def test_command_line_empty_value_is_empty_string(config):
+    assert config.command_line_to_dict(["key="]) == {"key": ""}
+
+
+def test_command_line_empty_list(config):
+    assert config.command_line_to_dict([]) == {}
+
+
+def test_default_used_when_nothing_configured(config):
+    assert config.config_get_by_key("MISSING", "fallback") == "fallback"
+
+
+def test_default_is_none_when_unspecified(config):
+    assert config.config_get_by_key("MISSING") is None
+
+
+def test_reads_from_command_line(config):
+    config._COMMAND_LINE = {"provider": "OpenRouter"}
+
+    assert config.config_get_by_key("provider", "Anthropic") == "OpenRouter"
+
+
+def test_reads_from_environment_with_omegaclaw_prefix(config, monkeypatch):
+    monkeypatch.setenv("OMEGACLAW_provider", "OpenRouter")
+
+    assert config.config_get_by_key("provider", "Anthropic") == "OpenRouter"
+
+
+def test_environment_key_without_prefix_is_ignored(config, monkeypatch):
+    # Only OMEGACLAW_<key> is consulted, never the bare key.
+    monkeypatch.setenv("provider", "OpenRouter")
+    monkeypatch.delenv("OMEGACLAW_provider", raising=False)
+
+    assert config.config_get_by_key("provider", "Anthropic") == "Anthropic"
+
+
+def test_reads_from_config_file(config, monkeypatch):
+    monkeypatch.delenv("OMEGACLAW_provider", raising=False)
+    config._CONFIG_FILE = {"provider": "OpenRouter"}
+
+    assert config.config_get_by_key("provider", "Anthropic") == "OpenRouter"
+
+
+def test_init_config_reads_yaml_file(config, monkeypatch, tmp_path):
+    # Goes through the real open() and yaml.safe_load(), not an injected dict.
+    monkeypatch.delenv("OMEGACLAW_provider", raising=False)
+    config_file = tmp_path / "config.yaml"
+    config_file.write_text("provider: Anthropic\n", encoding="utf-8")
+
+    config.init_config([f"config={config_file}"])
+
+    assert config.config_get_by_key("provider", "Fallback") == "Anthropic"
+
+
+def test_command_line_beats_environment_and_file(config, monkeypatch):
+    config._COMMAND_LINE = {"provider": "OpenRouter"}
+    monkeypatch.setenv("OMEGACLAW_provider", "OpenAI")
+    config._CONFIG_FILE = {"provider": "Anthropic"}
+
+    assert config.config_get_by_key("provider") == "OpenRouter"
+
+
+def test_environment_beats_config_file(config, monkeypatch):
+    monkeypatch.setenv("OMEGACLAW_provider", "OpenRouter")
+    config._CONFIG_FILE = {"provider": "Anthropic"}
+
+    assert config.config_get_by_key("provider", "DefaultProvider") == "OpenRouter"
+
+
+def test_config_file_beats_default(config, monkeypatch):
+    monkeypatch.delenv("OMEGACLAW_provider", raising=False)
+    config._CONFIG_FILE = {"provider": "OpenRouter"}
+
+    assert config.config_get_by_key("provider", "Anthropic") == "OpenRouter"
+
+
+def test_resolved_value_is_cached(config):
+    config._COMMAND_LINE = {"provider": "OpenRouter"}
+    first_result = config.config_get_by_key("provider")
+
+    config._COMMAND_LINE["provider"] = "Anthropic"
+    second_result = config.config_get_by_key("provider")
+
+    assert first_result == "OpenRouter"
+    assert second_result == "OpenRouter"
+
+
+def test_init_config_resets_old_cache(config, monkeypatch, tmp_path):
+    monkeypatch.delenv("OMEGACLAW_model", raising=False)
+    config._CONFIG["provider"] = "OldProvider"
+    config_file = tmp_path / "config.yaml"
+    config_file.write_text("provider: Anthropic\nmodel: free\n", encoding="utf-8")
+
+    config.init_config([f"config={config_file}", "provider=OpenRouter"])
+
+    assert config.config_get_by_key("provider") == "OpenRouter"
+    assert config.config_get_by_key("model") == "free"