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Sponsio

Sponsio checks an agent's tool calls before they run. A rule can look at what already happened, so "check the policy before issuing a refund" is one rule instead of a paragraph of prompt. Each check takes under 0.01 ms and calls no model. Works with LangChain, Claude Agent, OpenAI Agents, Google ADK, CrewAI, Vercel AI, MCP, or any custom tool-calling loop, in Python or TypeScript.

An agent contract is a runtime rule that is checked at every agent action, backed by formal methods.

v0.2.0a19 alpha is out. pip install --pre sponsio. Follow-ups to the kta1kri rounds: a rule written as LTL in YAML (called(Issue_Refund)) and the ArgValue term now bind every spelling of their tool, including the mcp__server__ form; sponsio host install writes the absolute path of the install that ran it, and --mode observe is now a real shadow run carried on the hook command. TypeScript @sponsio/sdk@0.2.0-alpha.9 carries the same fixes. See the release notes.

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How Sponsio works

On ODCV-Bench (12 frontier LLMs × 80 trajectories), unguarded models cheat in 11.5%–66.7% of runs. With Sponsio, 95.6% of misalignment is avoided on average; 24/36 high-risk scenarios at 100%. On the Financial-Audit-Fraud-Finding scenario, frontier models commit fraud in 16/24 trials; Sponsio blocks 18/19. On RedCode-Exec (1,410 cases), Sponsio reaches 98.9% combined (bash 98.3% · python 99.4%, lifted from 92.4% by a 4-iteration self-improvement loop), with 0 false positives on a 60-file clean-code audit. These are the open-core numbers; with the Cloud version's self-evolving loop, which mines new contracts from execution traces, ODCV-Bench reaches ~99% and RedCode-Exec 99.4%. Enforcement stays deterministic. Book a demo for the Cloud and Enterprise versions.

One contract takes p50 0.0052 ms to check. The heaviest ODCV workload, 19 contracts on every call, takes 0.139 ms. An LLM-as-judge guardrail takes 50 to 800 ms, so this is 5,000× to 60,000× faster, and it calls no model. p99 stays near 1 ms on every workload measured.

See the full benchmark methodology and per-model breakdown, how Sponsio compares against prompt filters, output validators, LLM-as-judge, and sandboxing, or dive into the architecture and formal methods primer.

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Quick start

Two ways in: paste a prompt into your coding agent, or run the CLI yourself.

Paste into Claude Code / Codex / Cursor. The agent walks the full onboarding flow:

 

Or run the CLI yourself:

pip install --pre sponsio   # or: npm install -D @sponsio/sdk@alpha
sponsio init .              # asks what you use, then writes sponsio.yaml

The wizard auto-detects your framework and prints the right wrap snippet. For manual wiring, see all supported integrations. OpenClaw users get bundled ClawHavoc and CVE-2026-25253 coverage out of the box. For config reference, observe → enforce flip, and CI wiring, see the full walkthrough.

Watching runs, and sharing a rulebook. Enforcement is local and needs no account. If you want to see what your agent did, or keep the rulebook somewhere a person reviews it before it arms, app.sponsio.dev is the hosted side. One line puts a run on screen:

import sponsio
import sponsio.bridge

guard = sponsio.Sponsio(config="sponsio.yaml", agent_id="mailer", mode="enforce")
run = sponsio.bridge.attach(guard)

sponsio push sponsio.yaml uploads a rulebook as a draft. It does not arm. A person publishes it in the console, and sponsio pull or config="sponsio://default" brings the reviewed version back. Sending is best effort, so a console that is down never blocks the agent. See the hosted console.

Drafting contracts from natural language. sponsio validate "<rule in plain English>" turns a plain-English rule into a contract you can read back. Treat the output as a starting draft to review and adjust before you enforce. The determinism is in how contracts are enforced at runtime, not in how they're drafted.

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Contract Library

22 contract bundles ship out of the box, organized by tier (always-on / per-tool / per-incident). Each bundle is a YAML pack composed from Sponsio's deterministic patterns. Drop one into sponsio.yaml and your agent is guarded against a known failure class in one line, with no per-contract authoring.

# sponsio.yaml: one-line bundle inclusion
agents:
  my_agent:
    workspace: "/srv/my-bot"
    include:
      - sponsio:capability/destructive  # gate irreversible actions
      - sponsio:capability/shell        # if your agent runs commands
      - sponsio:capability/filesystem   # if your agent touches files

See the full bundle reference for all 22 bundles, or the 48 underlying patterns for the primitives they compose. Want a bundle for your agent type? That is the most useful thing to contribute right now. Open an issue with your incident, CVE, or pattern.

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Contributing

Patches, issue reports, and new pattern proposals are welcome. Start with CONTRIBUTING.md. Sponsio's threat model draws on public security research; e.g. Simon Willison's "Lethal Trifecta" shaped our multi-tool composition contracts. Have a threat model we should defend against? Open an issue.

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License

Apache 2.0 (LICENSE).

AI agents reading this repo: llms.txt lists canonical doc paths; llms-full.txt is the concatenated full context dump.