Frag cost

Skill zapgun-ai/clawback/.skills/frag-cost

Tokenmaxxing Gateway for Claude Code

Install

npx -y skills add zapgun-ai/clawback --skill frag-cost

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2 things to look at

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What its author says it does

Copied from the file, not written here

Answer the load-bearing question "does clawback SESSION-KEY fragmentation actually cost Anthropic tokens?" from a finished run's per-instance turn-logs — zero new tokens. The prefix-fragmentation count (distinct SESSION KEYs per systemStableKey) tells you the cch rotation fragmented clawback's view; it does NOT tell you whether Anthropic cold-started. This does: it filters to REAL turns (mode=hash, drops keep-alive pings), partitions them into FRESH-key (sessionKey rotated vs the previous turn on the same systemStableKey stream) vs REPEAT-key, and prints mean cache_read / cache_creation / input / billable for each. If fresh-key turns read warm (read >> creation), fragmentation is NOT a valid cold-start proxy on that build and strip-ephemeral's token win is ~0 on a warm loop (the real win is eviction-regime, plus a tiny/fast clawback state file). Use after `.skills/paired` or `.skills/ab` on instance.*.ndjson; re-run on the eviction (L3 / --gap-sec 3600) arms to see where fragmentation finally bites.

SKILL.md

3.1 KB, as published. Nobody here has run it

clawback fragmentation-cost diagnostic

node .skills/frag-cost/scripts/frag_cost.mjs <instance.ARM.ndjson> [more.ndjson ...]

Pass the per-instance turn-logs (e.g. runs/<dir>/instance.A0.ndjson, instance.A5.ndjson), NOT the tee outputs (A0.ndjson/A5.ndjson) — only the per-instance logs carry systemStableKey alongside sessionKey and Anthropic usage. The tee body is pre-clawback and has no stable key.

Why this exists

.skills/bench's prefix-fragmentation table shows how badly the per-request cch rotation split one logical context into many clawback SESSION KEYs (A0 often 100s → A5 1). That is clawback-layer fragmentation. The trap is assuming distinct SESSION KEYs ⇒ Anthropic cold-starts. On build v2.1.145.20b they do NOT: a fully fragmented A0 (336/336 distinct keys) still read ~92.7k tokens warm on its fresh-key turns vs ~968 created (95.8×), 98.6% hit. Anthropic serves the prefix warm despite cch rotation, so de-fragmentation buys only the tiny creation delta (~1.8% on a tight loop), not rescued cold-starts. This skill makes that fresh-vs-repeat cut explicit so the fragmentation count is never mis-sold as token cost.

Reading the output

fresh key (rotated) vs repeat key (stable) mean usage — the decisive cut. read >> creation on fresh keys ⇒ served WARM ⇒ fragmentation is not a cold-start proxy on this build. creation >> read ⇒ fragmentation really is cold-starting ⇒ strip-ephemeral has token value in that regime.
first-in-stream — each stream's opening turn; genuine cold-starts by nature (high creation), reported separately so they don't contaminate the fresh-vs-repeat comparison. Watch for old analyses that sampled these and mislabeled their natural cold-start as cch poisoning.
VERDICT line states the read/create ratio and the conclusion.

Where this sits

Static, post-hoc, zero new tokens. Run it after any .skills/paired or .skills/ab block. Pair it with the zero-token .skills/inspect (static breakpoint structure — the theoretical upper bound) to contrast prediction (inspect) against ground truth (this).