Process-Safe Rustup Toolchain Operations

[nxsaken]

Metadata
Contact	@rami3l
Team(s)	rustup
Goal document	2026/process-safe-rustup
Funding contact	Funding team

Summary

This project goal aims to make rustup "process safe" in toolchain operations,
i.e. make it safe for multiple rustup instances to operate simultaneously on
the same toolchain, by introducing a new transaction mechanism to
rustup-installed toolchains and their modifying actions.

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This issue is intended for status updates only.

For general questions or comments, please contact a goal owner or post in the Zulip topic.

[nxsaken]

This issue is intended for status updates only.

For general questions or comments, please contact the owner(s) directly.

[rami3l]

Status update - Jul 2026

Key developments

• Picked up the abandoned project goal from 2024 and made it official.
• Drafted the v1 of my solution proposal. The current plan is to implement the transaction semantics part of that proposal and use A/B partitioning as a dummy addressing strategy.

Help wanted

Please feel free to check out the relevant discussion at https://rust-lang.zulipchat.com/#narrow/channel/490103-t-rustup/topic/Locked.20rustup.3A.20the.202025.20take/with/611540303!

[rami3l]

Status update - Aug 2026

Key developments

• Drafted the v2 of my solution proposal.
• Modeled the new transactional semantics using a TLA+ spec. The latter is also compatible with the plan regarding the transitional period (using A/B partitioning).
• Updated my first prototype of the proposal using rustup subprocesses. The runtime checks seem to be passing alright.
• Currently working on a more comprehensive prototype in the rustup codebase itself (not aiming for a merge yet).

Help wanted

Please feel free to check out the relevant discussion at rust-lang.zulipchat.com#narrow/channel/490103-t-rustup/topic/Locked.20rustup.3A.20the.202025.20take/with/611540303!

[rami3l]

Status update - Sep 2026

Key developments

• Refined the v2 of my solution proposal per @cachebag's suggestions.
• Made significant progress on the aforementioned in-repo prototype in a personal fork:
  • Implemented basic A/B partitioning and object GC.
  • Full test suite parity achieved on Linux and macOS on the fork modulo minor snapshot mismatches (basic functionalities OK).
  • Cherry-picked initial preparation PRs and merged to mainline.

Help wanted

Please feel free to check out the relevant discussion on Zulip!