# Backstop

> Hard limits for AI agents. Budgets, circuit breaking and concurrency control, in-process, with no proxy and no network hop.

## Get started

- [Documentation](https://backstop-b5g.pages.dev/docs): Backstop puts budgets, a circuit breaker and concurrency limits on AI agents, in the process that calls them.
- [Quickstart](https://backstop-b5g.pages.dev/docs/quickstart): Get to a working budget guardrail in under 60 seconds.
- [Installing Backstop](https://backstop-b5g.pages.dev/docs/install): Every install path: pip, pipx, uv, air-gapped, and from source.
- [The built-in dashboard](https://backstop-b5g.pages.dev/docs/dashboard): A dependency-free operations dashboard: budgets, concurrency, breaker state, sessions and enforcement events, with no Prometheus.

## How it works

- [Backstop Architecture](https://backstop-b5g.pages.dev/docs/architecture): An in-process control layer for the official provider SDKs: budgets, admission control, retries, circuit breaking, caching and metrics, around the transport.
- [Dollar budgets](https://backstop-b5g.pages.dev/docs/usd-budgets): A ceiling in money, priced from the model you actually call, with the arithmetic done in decimals.
- [The Spend Ledger](https://backstop-b5g.pages.dev/docs/ledger): What your traffic actually cost, grouped by whoever is responsible for it, with a charge-back export.
- [Runaway-spend detection](https://backstop-b5g.pages.dev/docs/detection): Four detectors that notice a spend pattern before it becomes an invoice: velocity, drift, retry amplification and context growth.
- [Concurrency & Scale Limits](https://backstop-b5g.pages.dev/docs/concurrency): What running in your own process means for the GIL, and where the concurrency ceiling actually is.

## Reference

- [Compatibility Matrix](https://backstop-b5g.pages.dev/docs/compatibility): Which SDK versions are tested, which are not, and what the matrix does not claim.
- [SDK Compatibility Matrix](https://backstop-b5g.pages.dev/docs/sdk-matrix): Which SDK version combinations CI actually proves, one row at a time.
- [Framework adapters](https://backstop-b5g.pages.dev/docs/frameworks): Backstop sits under the framework, at the transport, so any framework works without knowing Backstop exists.

## Operations

- [Budget alerts](https://backstop-b5g.pages.dev/docs/alerts): A webhook when a budget crosses a threshold, so the person who owns the budget hears about it while there is still budget left.
- [Benchmarks](https://backstop-b5g.pages.dev/docs/benchmarks): How the overhead numbers are measured, what they include, and what they do not.
- [Backstop control-path overhead — 2026-10-20](https://backstop-b5g.pages.dev/docs/benchmark-results-2026-10-20): The only committed overhead figures for this project, with the host, the seed, the transport and both payload sizes.
- [Threat Model](https://backstop-b5g.pages.dev/docs/threat-model): What Backstop trusts, what it does not, and where its limits are.

## Other

- [Backstop Benchmark Results](https://backstop-b5g.pages.dev/docs/benchmark-results-2026-07-20): A superseded overhead snapshot, kept for history: the date, the seed, the transport and the request count, and not the host.

## Agent resources

- [llms-full.txt](https://backstop-b5g.pages.dev/llms-full.txt): The full Markdown of every page in one file.
- [Page Markdown](https://backstop-b5g.pages.dev/index.md): Append `.md` to any page URL to fetch that page as raw Markdown.
- [JSON API](https://backstop-b5g.pages.dev/api/docs/pages.json): Page index of the JSON docs API; each entry links the page's JSON and Markdown forms. Described by the OpenAPI document at https://backstop-b5g.pages.dev/openapi.json.
- [API catalog](https://backstop-b5g.pages.dev/.well-known/api-catalog): RFC 9727 linkset of the APIs documented here.
- [AI catalog](https://backstop-b5g.pages.dev/.well-known/ai-catalog.json): ARD manifest of the agent-facing resources on this site (MCP server, skills, APIs).
- [agent-readability.json](https://backstop-b5g.pages.dev/agent-readability.json): Manifest of every agent-facing artifact on this site.
- [Sitemap](https://backstop-b5g.pages.dev/sitemap.xml): Every indexable page URL with its last-modified date.