llm-cost-governor

Composable pre-call and post-call hooks for LLM API calls: pricing, budgets, cost caps, rate limits, event log, observability.

Wrap your existing Anthropic / OpenAI / Voyage SDK calls with a single guarded_call(client, ...), register the hooks you need, and get:

• Priced cost per call from a shared pricing table (Sonnet, Opus, Haiku, GPT-4/5, Voyage embeddings, easy to extend).
• Session or scope budgets with pre-flight enforcement.
• Rolling-window cost caps (hourly / daily / weekly, optionally per-identity) with durable state (local disk or GCS).
• Per-IP request rate limiting as a FastAPI dependency factory.
• Structured event log (one JSON line per call) for offline analysis.
• OpenTelemetry span per call, with LangSmith metadata support and per-request content scrubbing.
• Framework-agnostic core — the FastAPI, GCS, and OTel bits are optional extras. Zero coupling to any host application.

The library was extracted from Pitchcraft and is currently consumed there in production; a second consumer (Rulebook) is scheduled to adopt it.

Adopting this in a new app? See docs/integration.md for the DI pattern, FastAPI init-order gotcha, constructor signatures, and reference implementation.

Install

# Core install
pip install "llm-cost-governor @ git+https://github.com/ecoop/llm-cost-governor@v0.3.0"

# With optional integrations
pip install "llm-cost-governor[fastapi,gcs,otel] @ git+https://github.com/ecoop/llm-cost-governor@v0.3.0"

Requires Python 3.11+. The core has just one dependency (pydantic v2); every integration is behind an optional extra so the install stays lean.

Quick example

from anthropic import Anthropic
from llm_cost_governor.wrapper import guarded_call
from llm_cost_governor.budget import ScopeBudget, ScopeBudgetHook
from llm_cost_governor.counters import CostCounter, WindowedCapHook
from llm_cost_governor.events import EventLogHook
from llm_cost_governor.state import LocalFileBackend

client = Anthropic()

# Wire up the counter at startup — one instance, shared across requests.
counter = CostCounter(
    object_name="cost_counter.json",
    backend=LocalFileBackend(path="./state"),
    enabled=True,
    hourly_cap_usd=0.50, daily_cap_usd=2.00,
    weekly_cap_usd=10.00, per_token_cap_usd=1.00,
)
counter.load()

# Per-request: build a fresh scope budget, compose the hook chain.
budget = ScopeBudget(limit_usd=0.25)
hooks = [
    ScopeBudgetHook(budget),
    WindowedCapHook(counter),
    EventLogHook(enabled=True),
]

# The one line that replaces `client.messages.create(...)`.
response, usage = guarded_call(
    client,
    provider="anthropic",
    hooks=hooks,
    tags={"stage": "drafter"},
    model="claude-sonnet-5",
    messages=[{"role": "user", "content": "Hello"}],
    max_tokens=512,
)

print(f"Cost: ${usage.cost_usd:.4f}   Tokens: {usage.input_tokens} in / {usage.output_tokens} out")

That's it. Every hook's pre runs before the SDK call (aborts on BudgetExceeded / CostCapExceeded / RateLimitExceeded); every post runs after with the priced UsageRecord and updates the shared state.

Core concepts

The Hook chain

guarded_call(client, ..., hooks=[...]) runs each hook's pre(ctx) method before the SDK call and each post(ctx, usage) after. A hook is any object with those two methods and a name attribute — implement your own by satisfying the Hook Protocol. The shipped hooks:

Providers

guarded_call(provider="anthropic", ...) selects the adapter that knows how to invoke the SDK and normalize the response. The Anthropic adapter ships in-box; OpenAI and Voyage adapters slot in as new modules with a couple lines each. See providers/anthropic.py for the shape.

State backends

Counters can persist their rolling-window state through the StateBackend Protocol. Two implementations ship:

• LocalFileBackend(path) — atomic JSON writes to a filesystem path. Default for local dev / CI.
• GcsBackend(bucket) — Google Cloud Storage blob. Lazily imports google-cloud-storage on first use, so the core install stays dep-free.

Add your own by implementing read(name) -> str | None and write(name, text) -> None.

record_usage — for calls you made yourself

Voyage embeddings, batch APIs, vision — anything that doesn't fit the guarded_call shape. record_usage() runs only the post hooks, still gives you priced cost and event log, without wrapping the call:

from llm_cost_governor.wrapper import record_usage

response = voyage_client.embed(texts=[...], model="voyage-3.5")
record_usage(
    provider="voyage", model="voyage-3.5",
    input_tokens=response.total_tokens, output_tokens=0,
    hooks=hooks, tags={"call_type": "embedding"},
)

What's in / what's out

Included:

• Pricing for currently-shipped Claude models — Fable 5, Opus 5, Sonnet 5, Opus 4.6/4.7/4.8, Sonnet 4.6, Haiku 4.5. Easy to extend for new models as they ship.
• Rolling-window counter with configurable caps + durable persistence.
• Per-IP rate limiter (framework-neutral core + FastAPI dependency factory).
• Structured event log (stdout → any log aggregator).
• Provider adapter for Anthropic.
• OTel span hooks + a request-span context manager + LangSmith metadata.
• Content-scrubbing OTel exporter for per-request telemetry control.
• Discord-webhook alert sink (implements the AlertSink Protocol).

Not (yet) included:

• Provider adapters for OpenAI, Voyage, Gemini — the shape is fixed and each is ~30 lines, but they're not in the box until someone needs them.
• Streaming responses. The wrapper is synchronous today; adding async is straightforward but not implemented yet.
• Multi-instance atomic counters — the rolling-window counter is correct at max-instances=1. Distributed correctness (e.g., Redis-backed) is a future extension.
• Retry / circuit-breaker logic. The library never retries — that's the caller's responsibility.

Development

git clone https://github.com/ecoop/llm-cost-governor
cd llm-cost-governor
python -m venv .venv && source .venv/bin/activate
pip install -e ".[dev]"
pytest
ruff check src tests

CI runs on Python 3.11, 3.12, 3.13 via GitHub Actions.

Versioning

Currently v0.3.1. The 0.3.x line renamed the package from llm-guardrails to llm-cost-governor. Semver from v1.0.0 onward; anything before is "shipped but pre-stable API — expect breaking changes."

Contributing

Issues and pull requests welcome. For substantive changes, open an issue first to discuss the shape before writing code. The Hook Protocol and provider-adapter surface are the two most important extension points — happy to talk through how to add a new provider or hook.

License

MIT. See LICENSE.