crosshair-tool
Analyze Python code for correctness using symbolic execution.
Decision gist · record as of 2026-08-14
Yes, if you work with type-annotated Python and want automated counterexample detection beyond traditional testing. The active maintenance, broad Python version support, and zero known vulnerabilities make it safe to adopt. Install friction is moderate due to z3-solver's compilation requirements, but prebuilt wheels are available. Best suited for projects where correctness is critical and you're willing to write contracts alongside type hints.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- z3-solver is a compiled dependency that may require build tools on some systems; symbolic execution can be computationally expensive for complex functions.
- Medium install friction due to 7 runtime dependencies including z3-solver, a heavyweight SMT solver.
- Actively maintained with a release 24 days ago and 1314 repository stars.
License · maintenance · safety
MIT (permissive) — MIT license permits commercial and private use with minimal restrictions, making it suitable for most development contexts.
last release 2026-07-21 (24 days) · last repo commit 2026-08-12 · 1,314 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 417,304 downloads/mo, #6,818 on PyPI
Alternatives
Verify before relying
pip install crosshair-tool
from crosshair.core import analyze
def example(x: int) -> int:
"""post: _ >= 0"""
return x * 2
analyze(example)- Whether IDE integrations for VS Code and PyCharm are actively maintained and compatible with current versions
- Performance characteristics and timeout behavior when analyzing large or complex codebases
- How well symbolic reasoning handles third-party library calls beyond the standard library
What it is and what it does
CrossHair is a symbolic execution and theorem-proving tool for Python that bridges testing and type systems. You annotate functions with type hints and optional contracts (preconditions, postconditions, invariants), and CrossHair explores execution paths using an SMT solver to find inputs that violate those contracts—essentially automated counterexample generation. It works by repeatedly calling your functions with symbolic inputs, tracking constraints, and asking the solver whether any path can violate your specifications.
Beyond contract checking, CrossHair can generate unit tests by exploring code paths and detecting behavioral differences between function implementations. It integrates with Hypothesis as an optional backend and offers IDE plugins for VS Code and PyCharm. The tool targets developers who want stronger correctness guarantees than traditional testing alone, particularly for functions with clear specifications. Runtime dependencies include z3-solver (the SMT engine), typing-inspect, pygls (for language server protocol), and typeshed-client.
Use it for
- Find edge cases and counterexamples in functions with type annotations and contracts before they reach production
- Generate test cases automatically by exploring symbolic execution paths through your code
- Verify that refactored or optimized functions behave identically to their original implementations
- Use as a Hypothesis backend for property-based testing with symbolic reasoning
- Catch off-by-one errors, null-pointer-like issues, and invariant violations in class methods
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if you work with type-annotated Python and want automated counterexample detection beyond traditional testing.
The active maintenance, broad Python version support, and zero known vulnerabilities make it safe to adopt. Install friction is moderate due to z3-solver's compilation requirements, but prebuilt wheels are available. Best suited for projects where correctness is critical and you're willing to write contracts alongside type hints.
Install
crosshair-tool on PyPI
Before you install
Medium install friction due to 7 runtime dependencies including z3-solver, a heavyweight SMT solver. Actively maintained with a release 24 days ago and 1314 repository stars. Supports Python 3.8 through 3.15 with prebuilt wheels across macOS, Linux, and Windows.
z3-solver is a compiled dependency that may require build tools on some systems; symbolic execution can be computationally expensive for complex functions.
License in practice
MIT license permits commercial and private use with minimal restrictions, making it suitable for most development contexts.
Quickstart
pip install crosshair-tool
from crosshair.core import analyze
def example(x: int) -> int:
"""post: _ >= 0"""
return x * 2
analyze(example)Verify before relying
- Whether IDE integrations for VS Code and PyCharm are actively maintained and compatible with current versions
- Performance characteristics and timeout behavior when analyzing large or complex codebases
- How well symbolic reasoning handles third-party library calls beyond the standard library
Package facts
| License | MIT permissive |
| Python support | Supports the current Python release >=3.8 |
| Install friction | Medium. Platform-specific wheel |
| Runtime dependencies | 7 packagespackagingtyping-inspecttyping_extensionsz3-solverimportlib_metadatapyglstypeshed-client |
| Maintenance | Actively maintained 24 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 417,304 / month, #6,818 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 3 - AlphaIntended Audience :: DevelopersOperating System :: MacOSOperating System :: Microsoft :: WindowsOperating System :: POSIX :: LinuxProgramming Language :: Python :: 3Programming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Programming Language :: Python :: 3.15Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Programming Language :: Python :: Implementation :: CPythonTopic :: Software Development :: Quality AssuranceTopic :: Software Development :: Testing |
Evidence: crosshair_tool-0.0.109-cp310-cp310-macosx_10_9_universal2.whl; crosshair_tool-0.0.109-cp310-cp310-macosx_10_9_x86_64.whl; crosshair_tool-0.0.109-cp310-cp310-macosx_11_0_arm64.whl; crosshair_tool-0.0.109-cp310-cp310-manylinux1_x86_64.manylinux_2_28_x86_64.manylinux_2_5_x86_64.whl; crosshair_tool-0.0.109-cp310-cp310-musllinux_1_2_x86_64.whl; crosshair_tool-0.0.109-cp310-cp310-win32.whl; crosshair_tool-0.0.109-cp310-cp310-win_amd64.whl; crosshair_tool-0.0.109-cp311-cp311-macosx_10_9_universal2.whl; crosshair_tool-0.0.109-cp311-cp311-macosx_10_9_x86_64.whl; crosshair_tool-0.0.109-cp311-cp311-macosx_11_0_arm64.whl; crosshair_tool-0.0.109-cp311-cp311-manylinux1_x86_64.manylinux_2_28_x86_64.manylinux_2_5_x86_64.whl; crosshair_tool-0.0.109-cp311-cp311-musllinux_1_2_x86_64.whl; crosshair_tool-0.0.109-cp311-cp311-win32.whl; crosshair_tool-0.0.109-cp311-cp311-win_amd64.whl; crosshair_tool-0.0.109-cp312-cp312-macosx_10_13_universal2.whl; crosshair_tool-0.0.109-cp312-cp312-macosx_10_13_x86_64.whl; crosshair_tool-0.0.109-cp312-cp312-macosx_11_0_arm64.whl; crosshair_tool-0.0.109-cp312-cp312-manylinux1_x86_64.manylinux_2_28_x86_64.manylinux_2_5_x86_64.whl; crosshair_tool-0.0.109-cp312-cp312-musllinux_1_2_x86_64.whl; crosshair_tool-0.0.109-cp312-cp312-win32.whl
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