diff --git a/skillopt_sleep/backend.py b/skillopt_sleep/backend.py
index f2cc3c84..d0015a29 100644
--- a/skillopt_sleep/backend.py
+++ b/skillopt_sleep/backend.py
@@ -1082,7 +1082,7 @@ def _call(self, prompt: str, *, max_tokens: int = 1024) -> str:
             "--stream", "off",
             "--no-color",
             "--log-level", "none",
-            "--allow-all-tools",
+            "--allowed-tools", os.environ.get("COPILOT_ALLOWED_TOOLS", "Bash"),
             "-C", clean_cwd,
         ]
         if not self.full_env:
@@ -1197,7 +1197,7 @@ def attempt_with_tools(self, task, skill, memory, tools):
                 "--stream", "off",
                 "--no-color",
                 "--log-level", "none",
-                "--allow-all-tools",
+                "--allowed-tools", os.environ.get("COPILOT_ALLOWED_TOOLS", "Bash"),
                 "-C", work,
             ]
             if not self.full_env:
diff --git a/tests/test_copilot_tool_scope.py b/tests/test_copilot_tool_scope.py
new file mode 100644
index 00000000..b965eab9
--- /dev/null
+++ b/tests/test_copilot_tool_scope.py
@@ -0,0 +1,53 @@
+"""Tests for Copilot CLI tool-scope reduction.
+
+The sleep engine's Copilot backend previously launched the CLI with
+``--allow-all-tools``, granting the model unrestricted tool access. It now
+passes ``--allowed-tools`` scoped to ``COPILOT_ALLOWED_TOOLS`` (default
+``Bash``). These tests capture the constructed argv without spawning the CLI.
+"""
+from __future__ import annotations
+
+from skillopt_sleep import backend as backend_mod
+from skillopt_sleep.backend import CopilotCliBackend
+
+
+def _make_backend() -> CopilotCliBackend:
+    b = CopilotCliBackend.__new__(CopilotCliBackend)
+    b.copilot_path = "copilot"
+    b.full_env = False
+    b.model = ""
+    b.copilot_home = ""
+    b.timeout = 10
+    return b
+
+
+def _capture_argv(monkeypatch) -> list[str]:
+    captured: dict[str, list[str]] = {}
+
+    def fake_run(cmd, *args, **kwargs):  # noqa: ANN001
+        captured["cmd"] = cmd
+        raise RuntimeError("stop before spawn")
+
+    monkeypatch.setattr(backend_mod.subprocess, "run", fake_run)
+    _make_backend()._call("hello")
+    return captured["cmd"]
+
+
+def test_allow_all_tools_removed(monkeypatch) -> None:
+    cmd = _capture_argv(monkeypatch)
+    assert "--allow-all-tools" not in cmd
+    assert "--allowed-tools" in cmd
+
+
+def test_default_scope_is_bash(monkeypatch) -> None:
+    monkeypatch.delenv("COPILOT_ALLOWED_TOOLS", raising=False)
+    cmd = _capture_argv(monkeypatch)
+    idx = cmd.index("--allowed-tools")
+    assert cmd[idx + 1] == "Bash"
+
+
+def test_env_var_overrides_scope(monkeypatch) -> None:
+    monkeypatch.setenv("COPILOT_ALLOWED_TOOLS", "Read")
+    cmd = _capture_argv(monkeypatch)
+    idx = cmd.index("--allowed-tools")
+    assert cmd[idx + 1] == "Read"