Eagerly transition to SAE for state sync by rahulmutt-ava · Pull Request #5916 · ava-labs/avalanchego

rahulmutt-ava · 2026-09-02T20:21:00Z

Why this should be merged

Resolves #5875. when state syncing a fresh node, it'll start at the coreth vm and if state sync is enabled & transition has happened in the rest of the network, it must transition because the rest of network only supports the SAE state sync protocol.

How this works

Updates the transitionvm to perform the necessary checks described above.

How this was tested

Unit tests + tested on a live fuji network.

Need to be documented in RELEASES.md?

No

Copilot

🔵 Needs a closer look

It changes startup-time VM transition behavior in a consensus-critical/state-sync path where incorrect behavior could strand nodes or affect network operability.

Pull request overview

This PR updates transitionvm to eagerly transition a fresh node to the post-transition VM (SAE) during Initialize when the wall clock is past the configured transition time and the node intends to state sync, avoiding failures caused by peers only serving post-transition state summaries after the network has transitioned.

Changes:

Add an eager-transition path in VM.Initialize to transition immediately (before any transition block is seen) for genesis-height nodes that will state sync and start after transitionTime.
Extend unit tests to cover eager-transition conditions, durability across restart, and error propagation from StateSyncEnabled.
Document the eager-transition behavior and accepted failure modes in vms/transitionvm/README.md.

File summaries

File	Description
`vms/transitionvm/vm.go`	Adds eager-transition logic in `Initialize` based on wall-clock time, chain height, and `StateSyncEnabled`.
`vms/transitionvm/vm_test.go`	Adds/updates test scaffolding and new tests validating eager transition behavior and persistence.
`vms/transitionvm/README.md`	Documents eager transition for state sync and explicitly lists the one-way commitment and failure modes.

Review details

Files reviewed: 3/3 changed files
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Review effort level: Lite

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alarso16

I'm not sure this is the correct parent. Maybe make it as a child of #5869 instead?

rahulmutt-ava · 2026-09-03T17:56:36Z

I'm not sure this is the correct parent. Maybe make it as a child of #5869 instead?

good point, rebased to #5869

alarso16

In theory, I think it would be helpful to provide a warning for people currently state syncing that the network transitioned and they should restart, but it sounds logistically complicated.

alarso16 · 2026-09-03T21:48:45Z

    class E errCls;
 ```

+### Eager transition for state sync


I think there's a lot of this block is redundant with itself and/or the code, so I would maybe say:

The requirements of the pre-VM and post-VM

What errors could occur/expected weird behavior

How to recover if there's a weird error

simplified this quite a bit - let me know how it looks now

…tion time Lets a fresh node joining after the coreth-to-saevm transition state sync via saevm: - transitionvm: Initialize transitions eagerly when the wall clock is past the transition time, the local chain is still at the genesis, and the pre-transition chain reports StateSyncEnabled. A node that already accepted pre-transition blocks never transitions eagerly — the post-transition chain refuses to state sync over accepted blocks — and instead bootstrap-executes to the transition block. The transition marker is a one-way commitment; hazards, including configurations the post-transition chain can never sync (Firewood), documented in the README. - saevm/statesync: document the invariant the eager transition relies on: with state sync enabled, a node whose last accepted block is the genesis never skips a state sync to a non-genesis summary. (adapted from commit 5964266, reduced to the fresh-node case and the transitionvm package, and folding in fixes from adversarial review)

Co-authored-by: Austin Larson <78000745+alarso16@users.noreply.github.com> Signed-off-by: Rahul Muttineni <rahul.muttineni@avalabs.org>

StephenButtolph

There are a number of subtle footguns here, but they are all only limited to a single node starting from scratch, so I think that this is OK to unblock state-sync.

rahulmutt-ava requested review from a team and StephenButtolph as code owners September 2, 2026 20:21

rahulmutt-ava added evm Related to EVM functionality sae labels Sep 2, 2026

rahulmutt-ava changed the base branch from alarso16/cchain-statesync to master September 2, 2026 20:21

rahulmutt-ava changed the title ~~Eagerly transition to the SAE C-Chain for state sync~~ Eagerly transition to SAE for state sync Sep 2, 2026

rahulmutt-ava force-pushed the rahulmutt/eager-transition branch from 3093968 to 42fc8f1 Compare September 2, 2026 20:26

Copilot AI lite review requested due to automatic review settings September 2, 2026 20:26

Copilot started reviewing on behalf of rahulmutt-ava September 2, 2026 20:27 View session

rahulmutt-ava added this to the Helicon - Mainnet Release milestone Sep 2, 2026

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rahulmutt-ava force-pushed the rahulmutt/eager-transition branch from 42fc8f1 to 908c9fd Compare September 3, 2026 13:21

rahulmutt-ava requested a review from ARR4N as a code owner September 3, 2026 13:21

rahulmutt-ava force-pushed the rahulmutt/eager-transition branch from 908c9fd to ed3f5f9 Compare September 3, 2026 13:54

rahulmutt-ava changed the base branch from master to alarso16/cchain-statesync September 3, 2026 13:54

rahulmutt-ava force-pushed the rahulmutt/eager-transition branch 2 times, most recently from 685cd63 to 95095ba Compare September 3, 2026 14:49

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rahulmutt-ava changed the base branch from alarso16/cchain-statesync to alarso16/synchronous-summaries September 3, 2026 17:43

rahulmutt-ava force-pushed the rahulmutt/eager-transition branch from bf5a58d to afc6fcf Compare September 3, 2026 17:52

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alarso16 force-pushed the alarso16/synchronous-summaries branch from 10d6151 to c2e1237 Compare September 3, 2026 20:01

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Base automatically changed from alarso16/synchronous-summaries to master September 3, 2026 23:49

rahulmutt-ava force-pushed the rahulmutt/eager-transition branch from 09939af to cbb1e84 Compare September 4, 2026 10:19

powerslider reviewed Sep 4, 2026

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Comment thread vms/saevm/statesync/syncer.go Outdated

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rahulmutt-ava force-pushed the rahulmutt/eager-transition branch 3 times, most recently from 7eaa5d2 to 63cef6a Compare September 4, 2026 15:41

StephenButtolph reviewed Sep 4, 2026

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Comment thread vms/transitionvm/vm.go

rahulmutt-ava force-pushed the rahulmutt/eager-transition branch from 63cef6a to c15da4b Compare September 4, 2026 16:00

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alarso16 reviewed Sep 4, 2026

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Comment thread node/node.go

Comment thread vms/transitionvm/vm.go Outdated

Update vms/transitionvm/vm.go

8f75e4a

Co-authored-by: Austin Larson <78000745+alarso16@users.noreply.github.com> Signed-off-by: Rahul Muttineni <rahul.muttineni@avalabs.org>

StephenButtolph approved these changes Sep 4, 2026

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StephenButtolph enabled auto-merge September 4, 2026 18:59

StephenButtolph disabled auto-merge September 4, 2026 19:52

gate eager transition to prod networks

74981c0

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rahulmutt-ava added 3 commits September 4, 2026 22:33

fix bazel

218bfc7

fix working about when the commit interval is needed

6ac63f6

Merge branch 'master' into rahulmutt/eager-transition

4a0fc87

StephenButtolph enabled auto-merge September 4, 2026 21:05

StephenButtolph added this pull request to the merge queue Sep 4, 2026

Merged via the queue into master with commit 53fa2d1 Sep 4, 2026
47 checks passed

StephenButtolph deleted the rahulmutt/eager-transition branch September 4, 2026 21:21

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Eagerly transition to SAE for state sync - #5916

Eagerly transition to SAE for state sync#5916
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rahulmutt-ava commented Sep 2, 2026

Why this should be merged

How this works

How this was tested

Need to be documented in RELEASES.md?

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rahulmutt-ava commented Sep 3, 2026

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