The historical RISC Zero 1.1 docs make the old service model unusually explicit: Bonsai was a hosted remote-proving path where developers set BONSAI_API_KEY and BONSAI_API_URL, then let default_prover() route proof jobs to a first-party service.
The same docs show the real control surface was not the zkVM runtime alone, but centralized service policy: API-key admission, quota ceilings, cycle accounting, executor limits, and managed GPU scheduling.
The 1.1 proving-options page is especially useful because it places Bonsai directly beside dev mode and local proving, which makes hosted proving legible as a distinct middle layer rather than a footnote to the runtime.
The current remote-proving docs now point only to Boundless, which helps date the architectural transition away from hosted proving.
The official Boundless migration page states that Bonsai was RISC Zero’s centralized proving service and that it became unavailable in December 2025. It also gives a clean comparison surface: Bonsai used direct API-based offchain delivery, while Boundless requires wallet plus storage-provider setup and moves proving into a decentralized protocol with asynchronous fulfillment.
No standalone Bonsai whitepaper or litepaper surfaced in this pass.
Best corpus use: compare Bonsai directly against local proving, RISC Zero as runtime infrastructure, and Boundless as the later prover-market layer so hosted-service control does not get flattened into generic zkVM or generic proof generation coverage.