Random session sampling destroys cross-session hash block sharing
(52% -> 16%) because sessions sharing system prompts get scattered.
New approach: take a contiguous time window from the trace (preserving
temporal locality of shared-prefix sessions), then thin within the
window to hit target QPS. This preserves both intra-session reuse
(62% of reusable tokens) and cross-session sharing (38%).
Results (block sharing rate):
Old random r=0.002: 16.0% -> Window+thin: 29.7%
Old random r=0.016: 19.5% -> Window+thin: 42.7%
Full trace baseline: 52%
Also corrected the "91% intra-session" claim: actual split is
62% intra / 38% cross (token-level), making cross-session sharing
preservation critical for valid APC benchmarks.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Gahow Wang
1e1e2e774d