An engine for long-running agents that rebuilds its prompt under a cap and runs on your budget
One thread for every AI assistant you use
Stage
MVP
MVP
Founded
Not given
Not given
Based in
Not given
IE
Pricing model
Freemium
Free trial
Pricing
Prototype: free during beta, then from December 16, 2026 it costs $1 per 1,000 agent calls after 1,000 monthly included calls. Production: $20 a month with 20,000 agent calls included, then $1 per 1,000 calls after that. Top-ups: $1 per 1,000 calls, from $10 to $500 at a time, never expiring.
Not given
Key features
Prompt rebuilt from journal under token cap at each step to keep it bounded as history grows
Spending limits checked before each model call at token prices you declare
Resume after crash without repeating finished actions
Tool calls returned as actions for your code to carry out
Proof of what ran: check prompts, re-run engine, download hash-chained journal
Integrations with Vercel AI SDK, OpenAI Agents SDK, LangGraph, Mastra, Pydantic AI
MCP server for Claude Code, Claude Projects and Codex
Works with any model via bring-your-own-key
TypeScript and Python clients for HTTP API access
TypeScript SDK
MCP server integration
What makes it different
Bounded prompt under a fixed cap while history grows, so costs per call stop climbing on long sessions
Every run recorded with cryptographic proof: rebuilable prompts, hash-chained journal, re-runnable engine
Resumes from crash without repeating finished actions using stable idempotency keys
Budget enforcement before each model call, not reactive overage billing
No model key storage or logging; your provider bills you directly
Single conversation thread across multiple AI assistants
Works in native AI assistant apps without switching
Argentic
Zipline