Most popular OSS agent harnesses (Cline, Roo Code, Continue, OpenCode, Aider) leave 30-90% off your API bill on the table because their prompt-caching code is subtly wrong, off-by-default, or just missing for some providers.
This repo is a set of drop-in skills that any AI coding agent (Claude Code, Codex, Cline, Cursor, Devin, Gemini CLI, OpenCode…) can read and apply on its own.
You don't read the diffs. You point your agent at this repo and say:
"Apply every skill in this repo that matches the harnesses I use."
The agent reads each SKILL.md, checks if it applies to your setup,
lands the diff, and verifies the fix on the wire. You go from broken
or partial caching to 80-99% cache hit rates without doing the
research yourself.
What you actually save
One row per completed audit, so the coverage matches the scorecard:
| Harness | Finding | Cost impact today | Fix / status |
|---|---|---|---|
| Claude Desktop Code | Default Desktop Code launches embedded Claude Code; clean Mac logs show non-zero cache read/create counters by default | Already gets Anthropic cache benefits; no prompt-caching fix needed | No skill; working baseline |
| Codex CLI | Correct OpenAI cache design: stable thread_id cache key |
Already gets OpenAI cache benefits | No skill; reference implementation |
| Aider | --cache-prompts off by default; 5min TTL/keepalive overhead |
Many users get 0% cache reads unless they opt in; shorter cache window | Skills: default-on caching + 1h TTL |
| OpenCode | Strong Anthropic path, but proxy/Bedrock edge cases exist | Some OpenAI-compatible→Anthropic/Bedrock routes miss cache | Skills: proxy detection + Bedrock doc-block fix |
| Roo Code | Anthropic volatile-message bug; Bedrock custom ARN gap | Wastes breakpoints; custom ARNs can drop to 0% cache reads | Skills: volatile-msg fix + Bedrock custom ARN fix |
| Cline | Anthropic volatile-message bug; OpenAI lacks prompt_cache_key |
Wastes Anthropic breakpoint; OpenAI native can get 0% cache reads | Skills: volatile-msg fix + OpenAI cache key + timestamp pin |
| Continue | Cache opt-in default; Gemini explicit caching missing; volatile-message bug | Many users get 0% cache reads; Gemini relies on implicit luck | Skills: default-on + volatile-msg + Gemini explicit cache |
| Hermes / Nous | Multi-provider cache plumbing works; xAI wire showed cached tokens | No verified savings bug in this audit | No skill; working audit |
| Codex Desktop | ChatGPT Codex backend cache-scope headers observed/inferred | No verified savings bug in this audit | No skill; inferred working |
| Devin CLI | Raw CLI model path is opaque Codeium/Devin protobuf | Cache behavior not inspectable from public CLI capture | No skill; unver |