TFLite SignatureDef subgraph-index crash PoC

What this proves

• A released TFLite/LiteRT Python runtime accepts a malformed model.
• Creating a SignatureRunner for the malformed signature succeeds.
• Calling get_input_details() or get_output_details() on that runner crashes the process natively.

Files

• reverse_signature_model.bin: public TensorFlow test fixture used as the clean baseline
• invalid_signature_subgraph.bin: mutated model with signatureDefs[0].subgraphIndex = 99
• repro_invalid_signature_subgraph.py: reproduces the crash and shows the clean baseline

Reproduction

• the baseline model succeeds
• the malformed model terminates the Python process when get_input_details() is called on the signature runner