Summary: Bonsai was RISC Zero’s centralized remote proving service. The note matters because it cleanly exposes the middle phase between local proving and a decentralized prover market: API keys, quotas, centralized scheduling, and plain first-party service dependence.
What it does:
Let developers generate proofs for RISC Zero zkVM applications without operating their own proving hardware
Accepted a guest program plus inputs and returned a proof through a hosted API flow
Integrated directly into host code via BONSAI_API_KEY and BONSAI_API_URL, with default_prover() automatically routing proving jobs to the service when configured
Exposed both a Rust SDK and a REST API for proof submission and retrieval
Enforced service-side quotas such as concurrent proofs, cycle budget, cycle usage, executor cycle limit, and per-job parallelism limits
Delivered a simpler offchain proving path than Boundless, which later replaced it with wallet-funded onchain requests plus external storage and asynchronous fulfillment
Key claims:
The RISC Zero 1.1 remote-proving docs describe Bonsai as a “highly parallelized, highly performant” service that split proving work across a dynamically sized GPU cluster
The 1.1 proving-options docs recommended remote proving for most applications, reserving local proving especially for private-input use cases and dev mode for rapid prototyping
The API docs show that practical access and performance were governed by centralized service policy: API keys, configurable quota ceilings, and cycle accounting
The Boundless migration page states that Bonsai was RISC Zero’s centralized proving service, that it became unavailable in December 2025, and that Boundless is intended as its replacement
The same migration material makes the architectural split unusually clear: Bonsai used two environment variables and direct offchain proof delivery, while Boundless requires wallet plus storage-provider setup and moves request/fulfillment into a decentralized protocol
Boundless docs also say onchain verification can remain compatible through the same verifier-contract path, which helps isolate what changed: request routing, delivery, liveness guarantees, and market structure rather than the core proof format alone
Whitepaper: No canonical Bonsai whitepaper or litepaper was surfaced in this pass. The strongest primary materials were RISC Zero’s historical remote-proving docs, proving-options docs, and the official Boundless migration page; see ../whitepapers/bonsai-primary-sources-2026-05-13.md.