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A Hit Rate Is a Retention Policy: Prefix-Cache Reuse in Agentic Coding Traces Compounds the Workload With the Server's Eviction Rule and the Harness's Invalidations, Which Serving Assumptions the Traces Actually Break, and the Rent-or-Buy Rule That Prices the Turn Boundary
(c) 2026 Pranay Mahendrakar. Licensed under CC BY 4.0. Life of Research Coding agents are becoming a major class of language-model traffic, and the first production-scale characterisation of that traffic, 13.5 million GitHub Copilot agent sessions, concludes that its findings "challenge…