fix: key prompt-cache affinity on git root, not cwd - #659
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xAI partitions cache by prompt_cache_key. Hashing the leaf cwd made every graff-evals sandbox a cold ~8k write (rematch first-call cache 0–512 vs grok 11k–43k already warm). Seed is the git root so worktrees and sibling sandboxes share; scratch -p uses graff-scratch. Prefix bytes still have to match. ADR 0011.
justrach
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August 28, 2026 06:33
This was referenced Aug 28, 2026
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Already on main (git-root cache affinity). Closing as superseded. |
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Prompt-cache max was already on (ADR 0011: stable catalog,
/btwparent key, child role lanes). The rematch still paid a cold ~8k on every first call becauseprompt_cache_keyhashed the leaf cwd.xAI partitions cache by that key. Sibling graff-evals sandboxes have the same system+tools prefix and different paths, so every task was a first-request write (cache 0–512). Grok-build’s first calls arrived already warm (11k–43k).
Change
Root affinity (
x-grok-conv-id/prompt_cache_key) is now:graff-scratchwhen there is no repo (scratch-pshares)Prefix bytes still have to match. A repo
CLAUDE.mddoes not hit another repo. Children still use role lanes, not the root id./cachenames the lever. ADR 0011 updated so this does not get “fixed” back to cwd.