coffer-cli 0.1.0

Scan codebases for LLM cost-waste anti-patterns. Find retry storms, missing prompt caching, unbounded conversation history, agent loops without iteration caps, and more — before you ship.

coffer-cli

Scan your code for LLM cost-waste anti-patterns before you ship.

coffer-cli is a static scanner for production AI code. It catches the mistakes that show up at month-end on your OpenAI / Anthropic bill — retry storms, missing prompt caching, unbounded conversation history, agent loops without iteration caps, SDK inits without timeouts, and more.

It is intentionally not a magic dollar estimator. Static analysis cannot know call volume; we leave that to live tracking. Instead, we surface structural risks that a careful reviewer would catch — but faster, in CI, on every commit.

pipx install coffer-cli

coffer scan ./my-app
coffer scan ./my-app --json     # for CI / Claude Code skill consumption
coffer prices                    # current model pricing table
coffer compare gpt-4o gpt-4o-mini

What it catches (v0.1.0)

Detectors are organized by the four levers that drive LLM cost:

Lever	Detector	Severity
A: input tokens	dynamic_before_static_cache_break — f-string interpolation in SYSTEM_PROMPT defeats OpenAI auto-cache and Anthropic cache_control	🚨 high
	unbounded_conversation_history — messages.append(...) without truncation or summarization	🟡 med
	uncached_large_prompt — ≥2,000-char hardcoded prompt without nearby cache_control	🟡 med
B: output tokens	missing_max_tokens — LLM call without a max_tokens cap	🟡 med
	reasoning_effort_high_default — reasoning_effort="high" literal (up to ~20× extra reasoning tokens on trivial tasks)	🟡 med
D: number of calls	llm_in_for_loop — N× cost; gather is a latency fix, not a cost fix	🟡 med
	agent_loop_no_max_iter — while True: containing an LLM call without an iteration cap (the $47K-incident pattern)	🚨 high
	temperature_nonzero_with_cache_hint — cache layer nearby but temperature > 0 silently breaks it	🟡 med
E: architecture	retry_loop_no_backoff — retry storm amplifies the bill 10×	🚨 high
	sdk_init_no_timeout — default 600s lets a hung provider block your thread	🚨 high

Each finding includes a concrete fix and explains the cost angle explicitly (we do not conflate latency fixes with cost fixes).

Use with Claude Code (the skill)

The coffer-cost-review Claude Code skill in skills/ combines this scanner with Claude's semantic judgment. In Claude Code, ask "review my LLM costs" and the skill will:

1. Run coffer scan <path> --json for deterministic findings
2. Read each flagged file in context to filter false positives
3. Add semantic-only checks the scanner cannot do (frontier model used for trivial tasks, free-form output where structured works, public endpoints without rate limit, ...)
4. Produce a severity-ranked review with concrete code-diff fixes

Install:

git clone https://github.com/neal-c611/coffer-cli
mkdir -p ~/.claude/skills
cp -r coffer-cli/skills/coffer-cost-review ~/.claude/skills/

What it deliberately does NOT do

• No invented dollar estimates. Call volume is unknowable from static code. We report severity, not numbers.
• No proxy mode. Your LLM calls go directly to your providers.
• No auto-rewrites. Suggestions only; you stay in control.

For live production cost tracking with per-feature and per-user attribution (the part static analysis genuinely can't do), see Coffer.

Exit codes

• 0 — clean, or only medium/low findings
• 1 — at least one high finding (use for CI gating)

Development

git clone https://github.com/neal-c611/coffer-cli
cd coffer-cli
uv sync --extra dev
uv run pytest

Patterns are detected by src/coffer_cli/patterns.py (regex-based, single-file scope) and rendered by src/coffer_cli/cli.py (typer + rich).

Contributions welcome. New detectors should:

• Default to medium severity; reserve high for patterns that are demonstrably cost-amplifying in production
• Include a test in tests/test_patterns.py showing both a positive case AND a negative case (the negative case is what keeps false-positive rate low)
• Propose a cost fix, not a latency fix. Wrapping things in asyncio.gather does not reduce the bill.

License

Apache 2.0.