Agent skill
tracking-cache-costs
Measures OpenCode prompt caching efficiency using ccusage-opencode. Use when investigating API costs, evaluating cache hit rates, or checking if upstream caching fixes have landed.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/other/tracking-cache-costs
SKILL.md
Tracking OpenCode Cache Costs
Quick Check
ccusage-opencode daily
Full Analysis
Run the analysis script for per-day cache efficiency breakdown and savings estimate:
node .opencode/skills/tracking-cache-costs/analyze.mjs
Output includes: daily cache read/write/uncached ratios, cost breakdown at model-specific rates, and projected monthly savings if cache writes were reduced.
Adjust the REDUCTION env var to model different improvement scenarios (default: 0.44 = 44%, per PR #5422's benchmark):
REDUCTION=0.30 node .opencode/skills/tracking-cache-costs/analyze.mjs
Interpreting Results
| Write % | Assessment | Action |
|---|---|---|
| <10% | Healthy | No action needed |
| 10-20% | Moderate | Check for short sessions or frequent subagent spawning |
| 20-40% | Poor | Cache busting likely -- tool reordering or file tree churn |
| >40% | Severe | Investigate immediately, major cost impact |
Root causes of high writes: tool definition order instability (prefix-based cache busted by reordering), file tree changes in system prompt, only 4 cache breakpoints in current opencode, short sessions / subagent spawning.
Check Upstream Progress
gh pr view 5422 --repo anomalyco/opencode --json state,comments --jq '{state, lastComment: .comments[-1].body[:200]}'
gh pr list --repo anomalyco/opencode --search "cache" --state merged --limit 5 --json number,title,mergedAt
Key items:
- PR #5422 -- provider-specific cache config (not merged)
- Issue #5416 -- caching improvement request
- Issue #5224 -- system prompt cache invalidation
- Any PR touching
packages/opencode/src/provider/transform.tssignals caching work
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