Cross-Provider Speculative Decoding: Acceptance Rate Collapses Past 32K Context

hoyasgirl25 · reddit · 2026-08-13

A developer experimenting with cross-provider speculative decoding (local draft model + third-party verifier) reports a severe bottleneck: acceptance rates plummet from 0.71 to 0.18 when the prefix exceeds 32K tokens.

Although next-token KL divergence remains stable during independent sampling and common issues like tokenizer skew and precision differences are ruled out, the divergence appears strongly position-dependent. The author suspects the provider's API might be applying a different RoPE scaling implementation or hidden context preprocessing, and is seeking advice on debugging this black-box issue without building a complex position-by-position logit fingerprinting harness.

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