ACP-181: P-Chain Epoched Views

[avalanche-foundation-admin]

Proposes a standard P-Chain epoching scheme such that any VM that implements it uses a P-Chain block height known prior to the generation of its next block. This would enable VMs to optimize validator set retrievals, which currently must be done during block execution. This standard does not introduce epochs to the P-Chain's VM directly. Instead, it provides a standard that may be implemented by layers that inject P-Chain state into VMs, such as the ProposerVM.

https://github.com/avalanche-foundation/ACPs/tree/main/ACPs/181-p-chain-epoched-views

[meaghanfitzgerald]

🔊 ACP-181 Community Call: P-Chain Epoched Views

Meeting Date/Time: July 1, 2025, 14:30 UTC (10:30 AM EST)
Meeting Duration: 1 hour
Presenters: Cam Schultz

Purpose of the Meeting

In this meeting, we will discuss ACP-181, which proposes a standardized P-Chain epoching scheme to optimize validator set retrievals. Currently, VMs must fetch validator sets during block execution, which can be inefficient. By introducing epochs—fixed periods where the P-Chain height remains constant—VMs can pre-fetch validator sets and reduce on-chain overhead.

This ACP does not introduce epochs directly to the P-Chain but provides a standard for layers (like ProposerVM) that inject P-Chain state into VMs.

Who is invited?

• Protocol developers
• ACP authors
• Researchers
• Avalanche community members

If you’ve previously signed up for an ACP call, no need to register again.

Links

📝 Sign Up Form: Google Form
🎥 Recording

Preparation Material

Mandatory Reading

📄 ACP-181: P-Chain Epoched Views

Suggested Reading

🔗 ProposerVM Implementation (PR #3746)

Agenda

1. Overview of ACP-181’s motivation and design
2. Discussion on epoch duration & security considerations
3. Open Q&A with the community

FAQs

Q: What problem does ACP-181 solve?
A: Currently, VMs must fetch the latest P-Chain validator set during block execution, which can slow down block production. ACP-181 introduces epochs, where the P-Chain height remains fixed for a period, allowing VMs to pre-fetch validator sets.

Q: Does this change the P-Chain itself?
A: No—this standard is for VMs that depend on P-Chain state (e.g., via ProposerVM). The P-Chain continues operating as-is.

Q: How does this impact validator set changes?
A: Validator updates are batched at epoch boundaries, which could lead to concentrated changes. The ACP discusses potential mitigations (e.g., queuing updates).

Q: What’s the proposed epoch duration?
A: This is still an open question—join the discussion to share your thoughts!

Q: Is this backwards-compatible?
A: No—this requires a network upgrade since it changes how VMs interact with P-Chain state.