Fireworks AI Tests Anthropic's J-Lens on Kimi K3 and Qwen3.5-9B

Fireworks AI applied Anthropic's Jacobian Lens (J-Lens), a trained probe that reads a model's hidden states, to Kimi K3 and Qwen3.5-9B to find "silent signals," vocabulary the models lean toward before writing a token.

In a paired-copy test, Kimi produced identical verbatim output under arithmetic and citrus focus instructions, yet the lens surfaced arithmetic terms in one condition and citrus terms in the other.

Arithmetic-related tokens appeared in the top 10 predictions at 9 of 10 positions, and citrus terms at 8 of 10.