[gaborbernat]

An untrusted checkout can make a launcher select an unsupported Python. The process cache and disk cache keyed that verdict by the launcher's unchanged path, so a later unrelated checkout could inherit the failure. This PR caches a query only when the probed path is the interpreter that answered. This addresses draft advisory ANT-2026-HK25S1M7.

Launcher results crossed directories

pyenv selects a version from the current directory's .python-version. Before this change, _get_from_cache retained every result under the launcher path, while _get_via_file_cache wrote successful and unsupported results to disk under the same path. The new identity check compares the queried path with the interpreter that answered before either cache accepts the result.

flowchart LR
    Q[Query candidate] --> Old[Before: cache by candidate path]
    Q --> Same{Now: candidate is the interpreter?}
    Same -- yes --> Keep[Cache the result]
    Same -- no --> Retry[Return without caching]
    classDef old fill:#ffd6d6,stroke:#c1121f,color:#5c0000;
    classDef fixed fill:#d8f3dc,stroke:#2d6a4f,color:#1b4332;
    class Old old;
    class Same,Keep,Retry fixed;

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Unsupported-version verdict identity

The old version gate reported only the version. The updated gate also reports its sys.executable, and _query_failure passes that identity to the cache decision. The user-facing error still names the queried candidate and its version.

Behavior changes

Direct interpreter paths and symlinks to them remain cacheable. Discovery queries launchers and generic failures again on later calls, including calls from a different current directory. The collector script change also invalidates older disk entries through the existing script hash.

Closes #194.

Reported by Anthropic's OSS Scanner: ANT-2026-HK25S1M7.