occ-vercel

Cryptographic proof signing for Vercel AI SDK tool calls. Every tool execution gets an Ed25519-signed pre/post proof pair written to proof.jsonl.

Install

npm install occ-vercel ai

Usage

Option A: Wrap tools directly

import { tool } from "ai";
import { z } from "zod";
import { occWrapTools } from "occ-vercel";

const tools = occWrapTools({
  search: tool({
    description: "Search the web",
    parameters: z.object({ query: z.string() }),
    execute: async ({ query }) => doSearch(query),
  }),
  calculate: tool({
    description: "Calculate math",
    parameters: z.object({ expression: z.string() }),
    execute: async ({ expression }) => eval(expression),
  }),
});

const result = await generateText({
  model: openai("gpt-4o"),
  tools,
  prompt: "Search for OCC",
});

Option B: Middleware pattern

import { generateText } from "ai";
import { occMiddleware } from "occ-vercel";

const result = await generateText({
  model: openai("gpt-4o"),
  tools: { search: searchTool },
  experimental_middleware: occMiddleware(),
  prompt: "Search for OCC",
});

Option C: Wrap a single tool

import { occWrapTool } from "occ-vercel";

const safeSearch = occWrapTool(searchTool, "search", {
  proofFile: "proof.jsonl",
  agentId: "my-agent",
});

Configuration

interface OCCVercelOptions {
  proofFile?: string;    // Default: "proof.jsonl"
  statePath?: string;    // Default: ".occ/signer-state.json"
  measurement?: string;  // Default: "occ-vercel:stub"
  agentId?: string;      // Default: "vercel-ai-agent"
}

How it works

1. Each tool's execute function is wrapped with pre/post proof signing
2. Pre-execution proof: Ed25519 signature over SHA-256(tool name + arguments)
3. Tool executes normally
4. Post-execution proof: Ed25519 signature over SHA-256(tool name + args + result)
5. Proofs are chained via prevB64 for tamper-evident ordering
6. Ed25519 keypair generated on first use, persisted to .occ/signer-state.json

Verify

npx occ-mcp-proxy verify proof.jsonl