126-Byte Snippet Crashes Five Major Python Type Checkers

charliermarsh · x · 2026-07-31

A tiny 126-byte code snippet has proven to be a fatal edge case for major Python type checkers. Testing the snippet caused a cascade of failures across popular tools: ty 0.0.65 stack-overflowed, mypy 2.3.0 segfaulted, Pyright 1.1.411 timed out, Pyrefly 1.1.1 panicked, and Pycroscope 0.4.0 exited with an internal error. This highlights the fragility of current static analysis tools when dealing with extreme syntax.

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