diff --git a/docs/guide/configuration.md b/docs/guide/configuration.md
index 8ce1760..2a72a64 100644
--- a/docs/guide/configuration.md
+++ b/docs/guide/configuration.md
@@ -205,7 +205,9 @@ directly through this backend.
 Cursor Agent first, then select it with `model.target_backend=cursor_exec`.
 Read-only rollouts use Ask mode; artifact-producing rollouts add Cursor's
 headless `--force` flag inside the benchmark workspace. SkillOpt enables the
-Cursor sandbox by default and does not approve MCP servers automatically.
+Cursor sandbox by default and rejects file-edit rollouts if it is disabled;
+read-only Ask-mode rollouts may explicitly disable it. SkillOpt does not approve
+MCP servers automatically.
 
 ### Three OpenAI-compatible paths
 
diff --git a/docs/reference/cli.md b/docs/reference/cli.md
index 97481ea..57269f4 100644
--- a/docs/reference/cli.md
+++ b/docs/reference/cli.md
@@ -2,10 +2,9 @@
 
 > **Version note.** This reference tracks `main`. PyPI 0.2.0 does not yet
 > include the generic research `openai_compatible` backend, Sleep handoff,
-> Sleep support for non-Azure OpenAI-compatible endpoints, or the Sleep
+> Sleep support for non-Azure OpenAI-compatible endpoints, the Sleep
 > `--preferences` flag, or the research `cursor_exec` target harness; use a
-> source install from `main` for those
-> features until the next release.
+> source install from `main` for those features until the next release.
 
 ## Training
 
@@ -108,8 +107,10 @@ python scripts/eval_only.py \
 `cursor_exec` runs the target only; the optimizer remains separately
 configured. Read-only rollouts use Cursor Ask mode. Rollouts that request file
 edits use `--force` inside the benchmark workspace, with Cursor sandboxing
-enabled by default. Override the executable or sandbox through
-`model.cursor_exec_path` and `model.cursor_exec_sandbox`.
+enabled. The harness refuses file-edit rollouts when the Cursor sandbox is
+disabled. Read-only Ask-mode rollouts may explicitly disable it. Override the
+executable or sandbox through `model.cursor_exec_path` and
+`model.cursor_exec_sandbox`.
 
 ## SkillOpt-Sleep
 
diff --git a/docs/reference/config.md b/docs/reference/config.md
index 9111b69..b8243c7 100644
--- a/docs/reference/config.md
+++ b/docs/reference/config.md
@@ -66,7 +66,7 @@ defaults to `claude` and can be overridden with `CLAUDE_CLI_BIN`.
 | `model.codex_exec_*` | Codex path, sandbox, profile, SDK mode, reasoning, network/search, and approval policy |
 | `model.claude_code_exec_*` | Claude path, profile, SDK mode, effort, and thinking-token cap |
 | `model.cursor_exec_path` | Cursor Agent executable path; default `cursor-agent` |
-| `model.cursor_exec_sandbox` | Cursor sandbox mode: `enabled` (default) or `disabled` |
+| `model.cursor_exec_sandbox` | Cursor sandbox mode: `enabled` (default) or `disabled`; file-edit rollouts require `enabled` |
 
 ## Training (`train`)
 
diff --git a/skillopt/model/codex_harness.py b/skillopt/model/codex_harness.py
index bbc0512..6bbb093 100644
--- a/skillopt/model/codex_harness.py
+++ b/skillopt/model/codex_harness.py
@@ -18,7 +18,6 @@ from skillopt.model.backend_config import (
     get_target_backend,
 )
 
-
 ANSWER_SCHEMA: dict[str, Any] = {
     "type": "object",
     "properties": {
@@ -1212,6 +1211,11 @@ def run_cursor_exec(
     actual_sandbox = str(sandbox or config["sandbox"])
     if actual_sandbox not in {"enabled", "disabled"}:
         raise ValueError("Cursor Agent sandbox must be 'enabled' or 'disabled'")
+    if allow_file_edits and actual_sandbox == "disabled":
+        raise ValueError(
+            "Cursor Agent file-edit rollouts require sandbox='enabled'; "
+            "refusing to combine --force with a disabled sandbox"
+        )
 
     for attempt in range(retries + 1):
         attempt_prompt = _exec_prompt(
diff --git a/tests/test_cursor_exec_backend.py b/tests/test_cursor_exec_backend.py
index a1c1a96..3fea88f 100644
--- a/tests/test_cursor_exec_backend.py
+++ b/tests/test_cursor_exec_backend.py
@@ -201,6 +201,33 @@ def test_cursor_exec_force_is_limited_to_file_edit_rollouts(
     assert "You may modify files" in prompt
 
 
+def test_cursor_exec_rejects_file_edits_with_disabled_sandbox(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    work_dir = _workspace(tmp_path)
+    calls = 0
+
+    def fake_run(_cmd: list[str], **_kwargs: Any) -> SimpleNamespace:
+        nonlocal calls
+        calls += 1
+        return SimpleNamespace(returncode=0, stdout=_result(), stderr="")
+
+    backend_config.configure_cursor_exec(sandbox="disabled")
+    monkeypatch.setattr(harness.subprocess, "run", fake_run)
+
+    with pytest.raises(ValueError, match="refusing to combine --force"):
+        harness.run_cursor_exec(
+            work_dir=str(work_dir),
+            prompt="Write solution.py.",
+            model="composer-2.5",
+            timeout=10,
+            allow_file_edits=True,
+        )
+
+    assert calls == 0
+
+
 def test_cursor_exec_retries_zero_exit_malformed_output(
     monkeypatch: pytest.MonkeyPatch,
     tmp_path: Path,