fix(bash): skip dotenv entries without values

agent/tools/bash/bash.py

@@ -202,7 +202,7 @@ SAFETY:
             if os.path.exists(env_file):
                 try:
                     from dotenv import dotenv_values
-                    dotenv_vars = dotenv_values(env_file)
+                    dotenv_vars = {key: value for key, value in dotenv_values(env_file).items() if value is not None}
                     env.update(dotenv_vars)
                     logger.debug(f"[Bash] Loaded {len(dotenv_vars)} variables from {env_file}")
                 except ImportError:

docs/adr/ADR-013-bash-bare-dotenv.md

@@ -0,0 +1,17 @@
+# ADR 013: fix(bash): skip dotenv entries without values
+
+## Context
+
+A valid dotenv line containing only a key is parsed as None. Injecting it into the subprocess environment makes every shell command fail with a TypeError.
+
+## Decision
+
+Forward only assigned dotenv values, retaining an inherited environment value when the dotenv entry has no assignment.
+
+## Consequences
+
+Empty assigned values remain valid and override inheritance. Bare declarations no longer prevent command execution.
+
+## Acceptance
+
+The regression in `tests/test_cow32_bash_bare_dotenv.py` fails on `5f54fc5beb55e522091ebfbe3a11aece9bb7d502` and passes with this decision. Related existing tests must pass. Validation uses local fixtures without external services or model calls.

tests/test_cow32_bash_bare_dotenv.py

@@ -0,0 +1,16 @@
+import sys
+from agent.tools.bash.bash import Bash
+
+def test_bare_dotenv_key_does_not_break_native_shell(tmp_path, monkeypatch):
+    home = tmp_path / "home"
+    folder = home / ".cow"
+    folder.mkdir(parents=True)
+    (folder / ".env").write_text("COW_BARE_KEY\nCOW_EMPTY_KEY=\n")
+    monkeypatch.setenv("HOME", str(home))
+    monkeypatch.setenv("USERPROFILE", str(home))
+    monkeypatch.setenv("COW_BARE_KEY", "inherited")
+    monkeypatch.setenv("COW_EMPTY_KEY", "old")
+    command = f"{sys.executable} -c \"import os; print(os.environ['COW_BARE_KEY'] + ':' + os.environ['COW_EMPTY_KEY'])\""
+    result = Bash({"cwd": str(tmp_path)}).execute({"command": command})
+    assert result.status == "success", result.result
+    assert "inherited:" in result.result["output"]