PR #3493 promoted every shell `_guard_command` rejection to a turn-fatal
RuntimeError. The two heuristic outputs in that list -- `path outside
working dir` and `path traversal detected` -- routinely false-positive on
benign constructs (e.g. `2>/dev/null`, quoted `..` arguments to sed/find,
absolute paths inside inline scripts), so legitimate workspace commands
silently kill the user's turn (#3599) and the agent never gets a chance
to retry with a different approach (#3605).
Two changes, both narrowly scoped:
- `ExecTool._guard_command` now skips a small allow-list of kernel device
files (`/dev/null`, the standard streams, `/dev/random`, `/dev/fd/N`,
...) before the workspace path check, matched against the pre-resolve
string so symlinks like `/dev/stderr -> /proc/self/fd/2` still hit the
allow-list. Real outside writes such as `> /etc/issue` remain blocked.
- `AgentRunner._WORKSPACE_BLOCK_MARKERS` keeps only the four hard
path-resolution errors from filesystem.py / shell.py and the SSRF
marker. The two heuristic substrings move out of the fatal list, so
the LLM sees them as ordinary tool errors and can self-correct in the
next iteration. SSRF stays fatal because retrying an internal URL
with a different phrasing would defeat the safety boundary.
Tests:
- `tests/tools/test_exec_security.py`: parametrized regression for the
exact #3599 command sample plus other stdio redirects and device
reads; explicit negative case asserts `> /etc/issue` is still blocked.
- `tests/agent/test_runner.py`: `_is_workspace_violation` no longer
fatals on the two heuristic markers, plus an end-to-end case proving
the runner hands the guard error back to the LLM and finalizes the
next turn cleanly.
* fix: allow_patterns take priority over deny_patterns in ExecTool
Previously deny_patterns were checked first with no bypass, meaning
allow_patterns could never exempt commands from the built-in deny list.
This made it impossible to whitelist destructive commands for specific
directories (e.g. build/cleanup tasks).
Changes:
- shell.py: check allow_patterns first; if matched, skip deny check
- shell.py: deny_patterns now appends to built-in list (not replaces)
- schema.py: add allow_patterns/deny_patterns to ExecToolConfig
- loop.py/subagent.py: pass allow_patterns/deny_patterns to ExecTool
- Add test_exec_allow_patterns.py covering priority semantics
* fix: separate deny pattern errors from workspace violation detection
The deny pattern error message "Command blocked by safety guard" was
included in _WORKSPACE_BLOCK_MARKERS, causing deny_pattern blocks to be
misclassified as fatal workspace violations. This meant LLMs had no
chance to retry with a different command — the turn was aborted
immediately.
Changes:
- shell.py: deny/allowlist error messages now use distinct phrasing
("blocked by deny pattern filter" / "blocked by allowlist filter")
- runner.py: remove "blocked by safety guard" from
_WORKSPACE_BLOCK_MARKERS so deny_pattern errors are treated as normal
tool errors (LLM can retry) instead of fatal violations
- workspace path errors still use "blocked by safety guard" and remain
fatal as intended
* fix: update test assertions to match new deny pattern error message
* fix: indentation error in test file
* fix: restore SSRF fatal classification and tidy exec pattern plumbing
Address review feedback on the deny/allow_patterns rework:
- runner.py: re-add "internal/private url detected" to
_WORKSPACE_BLOCK_MARKERS. The earlier marker removal also stripped
fatal classification from SSRF / internal-URL rejections (whose
message still says "blocked by safety guard"), turning a hard
security boundary into something the LLM could retry.
- loop.py / subagent.py: drop `or None` between ExecToolConfig and
ExecTool. The schema default is an empty list and ExecTool already
normalizes None back to [], so the indirection was a no-op.
- shell.py: extract `explicitly_allowed` flag in _guard_command so
allow_patterns are scanned once instead of twice and the control
flow no longer relies on a no-op `pass + else` branch.
- tests/agent/test_runner.py: add a regression test asserting that
the SSRF block message is treated as fatal, while deny/allowlist
filter messages are deliberately non-fatal.
* fix: remove unused exec allow-pattern test import
Keep the new ExecTool allow-pattern coverage clean under ruff.
Co-authored-by: Cursor <cursoragent@cursor.com>
---------
Co-authored-by: Xubin Ren <xubinrencs@gmail.com>
Co-authored-by: Cursor <cursoragent@cursor.com>
Keep the new exec guard focused on writes to history.jsonl and .dream_cursor while still allowing read-only copy operations out of those files.
Made-with: Cursor
