karanb192 claims the released cache-tax tool prevents idle Claude Code context from expiring through scheduled warming requests, potentially lowering resumed-session costs when avoided cache writes outweigh warming charges.
state: corroboratedheat: lowuncertainty: mediumconvergesscott: mediumprompt-caching inference-economics coding-agentskaranb192
What is this?
karanb192/cache-tax is an open-source Claude Code mod that keeps a session's prompt cache warm during breaks — after 50 idle minutes it sends one no-tools fork of the conversation as a warming request — and shows estimated cost before a 'cold' send; its repo description claims a 1-hour cache write on Fable 5.1 costs 80x a cache read. The expiry mechanism behind it is independently confirmed: a Sep 2026 hands-on write-up (Claude Code 2.1.269) documents the 'prompt cache has likely expired' notice and the 1h-Pro/Max vs 5m-API default TTLs, and an anthropics/claude-code GitHub issue records a ~200-token prompt being re-billed as ~900k input tokens after a 5-minute idle. The 80x pricing figure, however, appears only in the tool's own tagline, and on Hacker News a Claude Code team member (Boris) disputed the 'cache tax' framing — arguing stored-state cost doesn't change with idle length — while a commenter countered that Anthropic's higher 1h-TTL write price ($10 vs $6.25/MTok for Opus) is effectively a storage charge. No supplied source measures whether avoided cache rewrites outweigh warming charges, so the tool's net-savings premise remains unverified.
Why it matters to Scott
Two independent builders have shipped tools that operationalize what Scott's canon already argues — the cache-window-tuned heartbeat cadence in Ask Yourself If You're Finished and warm-kernel continuity in Prompt-Interrupt Architecture — keeping a live session inside the cache window rather than paying cold-reconstruction on resume, with the CLAUDE_CODE_PROMPT_CACHE_TTL override immediately applicable to his own ask harness. But the break-even at the heart of his Prefix-Caching Economics page (do avoided rewrites beat warming charges?) is still unmeasured and now publicly disputed by Claude Code's Boris, making this a dated-receipts test/publishing opportunity rather than mere corroboration.
ip:concept.prefix-caching-economicsip:source.ask-yourself-if-you-re-finished-cron-as-the-poor-man-s-orchestrator-ebookip:framework.prompt-interrupt-architecturedev:project.askradar:claude-code-cache-ttl-analyzerradar:concept.prompt-cachingradar:anthropic-context-compaction-cost-reversal
queries asked of Scott's wikis
- prefix caching write vs read pricing asymmetry
- cache window heartbeat cadence cron orchestrator
- Claude Code idle session resume cost spike
- scheduled keepalive warming requests in agent harness
- prompt cache TTL override environment variable
- warming cost vs avoided cache write break-even
Measured heat
now 0 pts/hpeak 2 pts/hcomments 0/hpeers p0momentum: steady2 platformsage 548h
points/hour across evidence · reading as of 2026-10-12 02:59:37.977291+11:00 · deterministic, not a model opinion
How the heat travelled
pace: p62 vs 1032 stories at the 336h mark (now 548h old) — ahead of linum-jit-ddt-training-efficiency (1.0x), behind artificium-covering-design-search (1.0x)
Evidence (3) — ⭐ canonical anchor
Interpretation history
2026-10-06T01:32:52Z
grounded: converges/medium — Two independent builders have shipped tools that operationalize what Scott's canon already argues — the cache-window-tuned heartbeat cadence in Ask Yourself If
2026-10-06T01:26:20Z
A second independent cache-warming plugin (TeachTall3390) with explicit TTL gating — defaults 1h on Pro/Max, 5m on API, CLAUDE_CODE_PROMPT_CACHE_TTL override — turns idle-warming from one builder's claim into a two-author replicated pattern and corroborates the cache-default reports the grounding flagged as inconsistent. The economics remain unmeasured and reception stays skeptical (0.64 ratio on the original; TOS-hoarding and '/loop is simpler' objections), so this is corroboration of the mechanism, not of net savings.
2026-10-05T23:34:20Z
evidence attached: reddit.post.1wyluod — Second independent Pi-inspired cache-warming plugin with explicit cost-benefit gating shows the idle-warming pattern replicating beyond one tool.
2026-09-18T20:38:44Z
grounded: converges/medium — The claimed cache-warming tool independently operationalizes Scott’s Prefix-Caching Economics and the cache-window-aware heartbeat cadence in Ask Yourself If Yo
2026-09-18T20:33:18Z
case created — An installable tool makes the cache-expiry optimization testable, but the claimed pricing asymmetry alone does not establish net savings.
Decision trace
- 10-06 12:32repriceA second independent cache-warming plugin (TeachTall3390) with explicit TTL gating — defaults 1h on Pro/Max, 5m on API, CLAUDE_CODE_PROMPT_CACHE_TTL override — turns idle-warming from one builder'
- 10-06 12:32groundTwo independent builders have shipped tools that operationalize what Scott's canon already argues — the cache-window-tuned heartbeat cadence in Ask Yourself If You're Finished and warm-kerne
- 10-06 10:34attachSecond independent Pi-inspired cache-warming plugin with explicit cost-benefit gating shows the idle-warming pattern replicating beyond one tool.
- 10-06 10:28propose_attachSecond independent Pi-inspired cache-warming plugin with explicit cost-benefit gating shows the idle-warming pattern replicating beyond one tool.
- 09-20 08:23review_screenThe only new content is a procedural question about handling warmed conversations; it adds no new fact, implementation result, pricing/access change, contradiction, or firsthand evidence.
- 09-19 22:24review_screenThe changes add criticism, a proposed workaround, and a personal anecdote, but no new implementation result, pricing evidence, or credible contradiction affecting the assessment.
- 09-19 18:20sensor_dirtycomment_update
- 09-19 14:23review_screenAdds only a speculative opinion about possible terms-of-service treatment, with no new implementation result, pricing evidence, or credible contradiction.
- 09-19 11:20sensor_dirtycomment_update
- 09-19 06:38groundThe claimed cache-warming tool independently operationalizes Scott’s Prefix-Caching Economics and the cache-window-aware heartbeat cadence in Ask Yourself If You re Finished Cron as the Poor Man s Orc
- 09-19 06:33createAn installable tool makes the cache-expiry optimization testable, but the claimed pricing asymmetry alone does not establish net savings.