Post-Quantum (PQ) Interop #28, February 25, 2026

Protocol Calls & happenings
1

Agenda

Resources

  • Facilitator email: will@ethereum.org
  • Facilitator Telegram: @corcoranwill
  • Telegram: PQ Interop — threads: #general, #devnet-1, #devnet-2, #devnet-3, #tooling, #leanVM, #onboarding

High-Level Documents

  • Devnet-0 : lean consensus client interop
  • Devnet-1 : PQ signature signing & verification
  • Devnet-2 : single-layer PQ signature aggregation
  • Devnet-3 : aggregator role separation + subnet aggregation

A. Devnet-3: Implementation Status

Client Readiness

Client Implementation Spec Tests Interop Docker Notes
Zeam :white_check_mark: :white_check_mark: :hourglass_not_done: :white_check_mark: Ready to interop, waiting for other clients. Working on checkpoint sync issues. leanQuickStart ready for Devnet-3.
Ream :white_check_mark: :large_orange_diamond: :hourglass_not_done: :large_orange_diamond: Spec fully implemented. Self-finalization tests not passing yet (debugging). Docker image ready for testing imminently.
Qlean :large_orange_diamond: :hourglass_not_done: :hourglass_not_done: :hourglass_not_done: Kamil traveling (AFK this call).
Lantern :white_check_mark: :white_check_mark: :hourglass_not_done: :white_check_mark: All specs implemented, tests passing. Local 4-node test showed justification/finalization. Ready to release Devnet-3 image for interop.
Ethlambda :large_orange_diamond: :large_orange_diamond: :hourglass_not_done: :hourglass_not_done: Internal 4-node Devnet running. Testing Devnet-3 implementation. Added checkpoint sync + chain guidance support. Next: code review/polish for Devnet-3 branch.
Lighthouse :hourglass_not_done: :hourglass_not_done: :hourglass_not_done: :hourglass_not_done: Back after ~1 month. Starting to target Devnet-3. Will take more time.
Grandine :large_orange_diamond: :hourglass_not_done: :hourglass_not_done: :hourglass_not_done: Multiple Devnet-2 fixes landed, more stable now. Still significant work remaining for Devnet-3.
Nimbus :red_question_mark: :red_question_mark: :red_question_mark: :red_question_mark: No representative on call.

Legend: :white_check_mark: Complete | :large_orange_diamond: In progress | :hourglass_not_done: Not started | :red_question_mark: Unknown

Devnet-3 Interop Status

  • Zeam + Lantern: Both ready to begin interop testing
  • Ream: Docker image expected within days; debugging self-finalization
  • Ethlambda: Internal testing in progress, polish phase next

B. Devnet-4: Specification Status

:tada: Recursive Aggregation API Complete (Emil)

  • Finished: Recursive aggregation implementation ready
  • API approach: Simplified — no Merkle tree of pubkeys needed
    • When verifying aggregated signature, simply feed the list of public keys directly
    • Most efficient approach after testing alternatives
  • Link: Test with API shared in Telegram (leanVM channel)
  • Next: Working on optimizations

Spec Discussion: SSZ Signature Container

Issue raised (Unnawut): leanSpec serializes signatures as variable-size lists (path/hashes), but all clients implement fixed-size bytes.

Discussion:

  • Lantern implemented variable-size per spec but added fixed-size fallback
  • Fixed-size is cheaper and matches all client implementations
  • Root cause: Variable-size was likely an early spec choice that doesn’t reflect the constant dimensions

Resolution: Thomas to update spec to use fixed-size (vector instead of list). Unnawut reverting Ream back to fixed-size.

Research Updates

  • leanSpec minimal client (Thomas): Interop tests passing locally (self-interop). Sync still flaky, but networking and fork choice stable.
  • Specification book (Thomas): Added 3SF-mini section, to be published soon.
  • Pubkey PQ registry (Thomas): Starting to draft a post on post-quantum public key registry.
  • Beacon spec modernization: Discussions ongoing about merging with leanSpec.

C. Long-Running Devnet-2 & Checkpoint Sync

Devnet-2 Stability

  • :tada: 24+ hours finalized: Long-running Devnet-2 reached almost 24 hours of continuous finalization
  • Ream: Reached 13,000 slots; fixed log size issues
  • Grandine: Multiple stability fixes landed

Checkpoint Sync Testing (Katya)

  • Found working combination for 4 clients
  • Testing order: Zeam → Ethlambda → Lantern
  • Lantern implementing checkpoint sync flag for Devnet-2 image (serving finalized/justified states)

Devnet-2 Bug Fixes

Client Fix
Lantern QUIC certificate rotation when expired
Ethlambda Reduced memory during long syncs (upload pending blocks to disk); improved checkpoint sync; added chain guidance support; wrote checkpoint sync + consensus documentation

D. New Client Onboarding

Client Target Devnet Implementation Spec Tests Interop Docker Notes
Gean Devnet-1 → 2 :white_check_mark: :white_check_mark: :hourglass_not_done: :large_orange_diamond: Integrated leanSig (block/attestation signing, signature verification). Integrated leanMetrics for Devnet-1. PR for leanQuickStart expected tomorrow for multi-client interop. Then targeting Devnet-2.

Meeting Time: Wednesday, February 25, 2026 at 14:00 UTC (60 minutes)

GitHub Issue

2

Meeting Summary:

The team provided updates on various development efforts including devnet interop testing, performance improvements, and checkpoint sync issues across different clients and environments. Progress was reported on multiple devnets, with successful client interoperability testing and resolution of technical issues, while the team also discussed implementation details for signature containers and encoding methods. The conversation ended with updates on performance improvements, testing results, and plans for upcoming work including devnet speccing and port mode scheduling.

Click to expand detailed summary

Gajinder provided updates on the team’s work, including devnet 3 interop with other clients, performance improvements for the Zoom node through caching, and work on checkpoint sync scenarios. The team is reviewing PRs and addressing issues related to these improvements. Gajinder mentioned that Anshil has been working on the API provided by Emil, and they plan to start devnet spec work by the end of the week.

The team discussed progress on devnet 3, where 5 clients were able to interoperate successfully based on Partha’s testing. Shariq reported that checkpoint sync issues with HTTPS have been resolved by swapping a rust library, and the team is ready to start long-term devnets on devnet 3 and begin work on devnet 4 this week. Mihir mentioned debugging issues with slot 3000 and final tablet breaks in devnet 2, and plans to bring those fixes to the devnet 3 branch and release a new image.

The team discussed progress on devnet 3, with Pablo reporting fixes to Gossip message interoperability and the addition of an attestation-commit CLI parameter. Shaaibu shared that their work on devnet 1 was completed but noted that Lane Quickstart doesn’t currently support devnet 1, so they conducted local multi-client interoperability testing instead. The team is now focusing on aligning with other teams to participate in devnet 3 multi-client interoperability testing.

The team discussed progress on DevNet 4, with Gajinder confirming that Anshal is working on a high-level document and will update the coordinating PM markdown. Thomas reported working on the spec and minimal client for interop testing, sharing encouraging results from local tests but requesting the client team to verify integration with their systems. The team also discussed the need for agreement on SSD container implementation for signatures before interop testing can proceed, and Thomas mentioned ongoing work on crypto improvements and potential hash function alternatives following a recent paper on PoSAIDON 2.

The team discussed the implementation of an SSD container for signatures. Gajinder raised questions about the necessity of including the signature structure, but Thomas and Mihir confirmed that hashing the signatures is not currently required and likely not needed in the future. The group agreed that the current approach should work without implementing the SSD container. Parthasarathy inquired about Docker registry preferences for LeanSpec node, to which Thomas responded positively about using a personal registry and suggested publishing Docker images upon merge to the main branch.

T reported a 30% performance improvement for XMSS and recursion after modifying the ISA and compiler. The team discussed encoding methods, with T suggesting the default encoding in the multisig container should work well, though not necessarily be optimal. Benedikt confirmed there’s an issue in the lean sig repository to implement the encoding from a paper, and offered to review a PR if someone takes on the implementation work. Anshal mentioned they need to complete devnet 4 speccing by week’s end and confirmed they don’t need the encoding implementation immediately for that work.

Katya reported testing Checkpoint Sync for 5 clients with successful results, sharing minor issues in the chat. She updated devnet 2 dashboards and is working on devnet 3 metrics, hoping to merge the PR today. Will mentioned he plans to share the port mode schedule later in the week.

Next Steps:

  • Anshal: Start devnet 4 spec work by the end of this week
  • Anshal: Create a high-level doc for DevNet 4
  • Anshal: Update the overall PM markdown doc that cross-coordinates the high-level docs when creating DevNet 4 doc
  • Mihir: Bring finality fixes from devnet 2 testing into DevNet 3 branch and release a new image for DevNet 3
  • Pablo: Share the HTML page with live view of chain status in the Telegram chat
  • Client teams: Check interop with LeanSpec client and report any bugs found
  • Anshal: Post about encoding discussion on the group for others to review and comment
  • Benedikt: Review PR if anyone implements the encoding from the paper in lean sig repository
  • Benedikt: Sync offline with T. about encoding implementation
  • T.: Try to implement the encoding in Linsig as soon as time permits
  • Katya: Share with Lambda team what should be fixed for checkpoint sync after the call
  • Katya: Update Link Start with merged devnet 2 dashboards this week
  • Katya: Merge devnet 3 dashboards PR, hopefully today, and share in the tooling chat
  • Parthasarathy: Include PR to LeanSpec to publish Docker images to preferred registry every time there’s a merge to main branch
  • Will: Share the schedule for port mode later this week in the PQ channel

Recording Access:

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YouTube recording available: https://youtu.be/Csg2NSpPm6o