Harden masternode handling to avoid empty validator sets

[Copilot]

The “Master improvements” scope needed safeguards to prevent empty masternode sets and clearer validation when epoch data is missing.

Changes

• Snapshot handling: fail fast when penalties remove all candidates to avoid empty validator sets.
• Leader selection: guard HotStuff leader lookup against null/empty masternode arrays.
• Seal validation: return clear errors when epoch info or masternodes are absent; align messaging.
• Tests: added coverage for fully penalized snapshots and missing/empty masternode validation paths.

Key check:

EnsureMasternodesAvailable(candidates, blockNumber); // SnapshotManager
if (currentMasternodes is null || currentMasternodes.Length == 0) throw ...; // HotStuff leader selection

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Description

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

Notes on testing

Targeted XDC tests added/executed for penalized snapshots and missing/empty masternode cases.

Documentation

Requires documentation update

• Yes
• No

Requires explanation in Release Notes

• Yes
• No

Remarks

None.

Original prompt

Master improvements

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Summary by cubic

Hardens masternode handling to prevent crashes and report clear errors when none are available. Adds explicit checks: SnapshotManager now throws when penalties remove all candidates, XdcHotStuff throws on empty/null sets, and XdcSealValidator fails with a message if epoch info is missing or empty; adds focused tests.

^{Written for commit 55f6e34. Summary will update on new commits.}

[vercel]

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Project	Deployment	Actions	Updated (UTC)
express-4bpo	Error		Mar 29, 2026 7:41am

[Deejae69]

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[cubic-dev-ai]

No issues found across 5 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Requires human review: Modifies core consensus logic and error handling in XDC masternode selection, which is a critical path requiring human review for protocol safety.}

[cubic-dev-ai]

0 issues found across 2 files (changes from recent commits).

_{Requires human review: This PR modifies core consensus logic for XDC (SnapshotManager, HotStuff, and SealValidator), including new error handling and exceptions in critical execution paths.}

[Deejae69]

Improve coding