persist per-topic NonceV2 epoch sequence (ENGN-8910)

[zale144]

Summary

• Add a per-topic topicLastEpochNonce store and AllocateNextEpochNonce so each StartEpoch gets a unique NonceV2 (Bech32 deferred).
• Round-trip the last-nonce map through genesis (topic_last_epoch_nonces).
• Cover monotonic allocation and export/import with unit tests.

Test plan

• go test ./x/emissions/keeper/ -run 'TestKeeperTestSuite/TestAllocateNextEpochNonceMonotonicPerTopic|TestKeeperTestSuite/TestTopicLastEpochNonceGenesisRoundTrip'
• CI green on this PR

Linear: ENGN-8910

Made with Cursor

---

Summary by cubic

Persists per-topic types.NonceV2 epoch sequences and makes StartEpoch allocate the next per-topic nonce; sequences survive restarts and export/import. Keeps types.NonceV2, defers Bech32. Linear: ENGN-8910.

• Adds topicLastEpochNonce map (TopicLastEpochNonceKey=112) with GetTopicLastEpochNonce and AllocateNextEpochNonce; first allocation is ZeroNonce().NextNonce() (V1, payload 1).
• Wires StartEpoch to AllocateNextEpochNonce so every epoch is unique per topic.
• Genesis: new topic_last_epoch_nonces (types.TopicIdAndEpochNonce) with Init/Export; NewGenesisState initializes it empty.
• Tests: per-topic monotonic allocation and genesis round-trip in x/emissions/keeper/epoch_nonce_test.go.
• Lint/format: reformat v10 protos; update x/emissions/proto/buf.yaml rules for EpochState; fix golangci issues (explicit FSM Advance asserts, NonceV2.Version bitmask with //nolint:gosec, add context in tests, minor static checks).

^{Written for commit 35530f6. Summary will update on new commits.}

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf Linter / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	⏩ skipped	Aug 20, 2026, 6:26 PM

[cubic-dev-ai]

cubic analysis

1 issue found across 10 files

Not reviewed (too large): x/emissions/api/emissions/v10/genesis.pulsar.go (~2,188 lines) - if these are generated or fixture files, add them to ignored paths to exclude them from future reviews.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="x/emissions/keeper/epoch.go">

<violation number="1" location="x/emissions/keeper/epoch.go:103">
P2: Starting an epoch panics once the persisted sequence reaches the uint56 limit, instead of returning a recoverable allocation error. Guard the maximum payload before calling `NextNonce` so an exhausted sequence cannot halt this execution path.</violation>
</file>

Linked issue analysis

Linked issue: ENGN-8910: Epoch nonce format + per-topic sequence persistence

Status	Acceptance criteria	Notes
✅	Add per-topic sequence store for last allocated epoch NonceV2 and persist it through genesis/export-import	The keeper now includes topicLastEpochNonce map, genesis init/export iterate and set logic, and the genesis proto/types were extended to carry TopicLastEpochNonces.
✅	Wire per-topic sequence into StartEpoch so every new epoch gets a unique NonceV2 per topic	StartEpoch now calls AllocateNextEpochNonce and no longer uses a zero nonce placeholder; AllocateNextEpochNonce computes NextNonce() and persists it as the topic's last nonce.
✅	Unit tests cover monotonic per-topic allocation and genesis round-trip (sequence survives restart/export-import)	Added tests exercise monotonic allocation across topics and verify that exported genesis carries last-nonce rows which are initialized by InitGenesis and produce the same next allocations after import.

Architecture diagram

sequenceDiagram
    participant Trigger as Epoch Trigger (BeginBlocker/Msg)
    participant Keeper as Keeper
    participant Store as topicLastEpochNonce Store
    participant GenesisExporter as Genesis Export
    participant GenesisImporter as Genesis Import

    Note over Trigger,Store: NEW: Per-topic epoch nonce allocation

    Trigger->>Keeper: StartEpoch(topicID)
    Keeper->>Keeper: AllocateNextEpochNonce(topicID)

    Keeper->>Store: Get(topicID)
    alt First allocation for topic
        Store-->>Keeper: not found (ErrNotFound)
        Keeper->>Keeper: lastNonce = ZeroNonce()
    else Subsequent allocation
        Store-->>Keeper: lastNonce
    end

    Keeper->>Keeper: nextNonce = lastNonce.NextNonce()
    Keeper->>Store: Set(topicID, nextNonce)
    Store-->>Keeper: ok
    Keeper->>Keeper: Create epoch with nextNonce
    Keeper-->>Trigger: epoch started

    Note over Trigger,Store: Monotonic per topic: NonceV2 version V1, payload increments

    Note over GenesisExporter,GenesisImporter: NEW: Genesis round-trip for nonces

    GenesisExporter->>Keeper: ExportGenesis(ctx)
    Keeper->>Store: Iterate()
    Store-->>Keeper: topicID → NonceV2 pairs
    Keeper->>Keeper: Build TopicLastEpochNonces slice
    Keeper-->>GenesisExporter: genesis data with nonces

    GenesisImporter->>Keeper: InitGenesis(ctx, data)
    Keeper->>Keeper: Iterate TopicLastEpochNonces
    loop each entry
        Keeper->>Store: Set(topicID, nonce)
        Store-->>Keeper: ok
    end
    Keeper-->>GenesisImporter: genesis initialized

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Fix all with cubic | Re-trigger cubic</sub>

[cubic-dev-ai]

P2: Starting an epoch panics once the persisted sequence reaches the uint56 limit, instead of returning a recoverable allocation error. Guard the maximum payload before calling NextNonce so an exhausted sequence cannot halt this execution path.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At x/emissions/keeper/epoch.go, line 103:

<comment>Starting an epoch panics once the persisted sequence reaches the uint56 limit, instead of returning a recoverable allocation error. Guard the maximum payload before calling `NextNonce` so an exhausted sequence cannot halt this execution path.</comment>

<file context>
@@ -75,6 +76,37 @@ func (k *Keeper) setupEpochFSMEngine() {
+		lastNonce = types.ZeroNonce()
+	}
+
+	nextNonce := lastNonce.NextNonce()
+	if err := k.topicLastEpochNonce.Set(ctx, topicID, nextNonce); err != nil {
+		return types.NonceV2(0), err
</file context>

Suggested change

	nextNonce := lastNonce.NextNonce()
	if lastNonce.Payload() == (uint64(1)<<56)-1 {
	return types.NonceV2(0), errors.New("epoch nonce sequence exhausted")
	}
	nextNonce := lastNonce.NextNonce()