fix: support trusted warp sync checkpoints on release v500

[UnArbosFive]

Summary

Ports the trusted Finney GRANDPA warp-sync checkpoint fix from #3113 onto the release-v500 branch used by #3117.

• register an explicit grandpaWarpSyncCheckpoint chain-spec extension containing a historical GRANDPA transition header and the authority set that signed it
• feed that trusted transition into the existing GRANDPA warp-proof verifier, preserving Finney's one-time initial set-ID correction while allowing normal proof verification to continue to the peer's current finalized head
• expose a compact grandpa_genWarpSyncCheckpoint response behind the opt-in --enable-warp-sync-checkpoint-rpc flag
• preserve grandpaWarpSyncCheckpoint whenever the raw and plain chain specs are rebuilt
• require any exceptional future checkpoint change to be an explicit reviewed chain-spec diff; normal scheduled authority rotations require no refresh

Addresses #3112.

Cause and user impact

Finney's historical GRANDPA set-ID discontinuity causes otherwise valid warp proofs to be rejected during bootstrap. A full sync bypasses warp verification but is not a practical replacement for lite-node operation. This change supplies a trusted historical signing boundary in the Finney chain spec, after which ordinary GRANDPA transitions continue to be verified from the proof chain.

Trust and compatibility

• Finney remains Aura for block production and GRANDPA for finality. This is GRANDPA-only and does not modify BABE.
• The checkpoint authenticates one historical transition; it is not a current-set-ID cache. Future scheduled rotations and set-ID increments are verified automatically and do not require checkpoint updates.
• State sync remains targeted at the proof's current finalized header, so clients do not need archive state at the historical checkpoint.
• A malformed populated checkpoint fails startup in warp mode.
• Full sync, sealing, existing databases, and chain specs without a checkpoint retain their existing behavior.
• Serving peers do not need this branch, but Finney proof providers need the set-ID generation fix first released in v446 and retained transition data.
• The generator RPC is disabled by default and does not automatically update a chain spec.

Validation

• replayed the exact fix: support trusted warp sync checkpoints #3113 commit series onto the current Release 450: canonical on-chain beta pricing, display units, and curated beta #3117 head with no conflicts
• confirmed all nine touched files are byte-for-byte identical to the audited final fix: support trusted warp sync checkpoints #3113 state
• cargo fmt --check --all
• bash -n scripts/build_all_chainspecs.sh
• git diff --check origin/release-v500...HEAD
• SKIP_WASM_BUILD=1 cargo check -p node-subtensor --lib
• the focused checkpoint and service tests passed on the original change; CI reruns the complete checks against this release-v500 base
• the prior fresh-database Finney regression completed --sync=warp, imported current state, reported GRANDPA set ID 6, reached isSyncing: false, and continued finalizing blocks
• the archive proof provider restarted on its existing database and served current-head proofs without a database re-sync

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Project	Deployment	Actions	Updated (UTC)
subtensor	Building	Preview	Aug 27, 2026 5:39pm

[github-actions]

🛡️ AI Review — Skeptic (security review)

VERDICT: SAFE

VERY HIGH account-age/repository scrutiny, mitigated by admin permission and substantial merged history; no Gittensor association found; integration branch fix/finney-light-sync-checkpoint-v500 → release-v500.

Static review found the nine changed files byte-identical to the previously reviewed and merged #3113 implementation. The checkpoint remains explicitly chain-spec anchored, validates its transition shape and authority set, and the generator RPC is opt-in.

Findings

No findings.

Conclusion

No malicious behavior or security vulnerability was found in the PR-specific changes.

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🔍 AI Review — Auditor (domain review)

VERDICT: 👍

Gittensor association UNKNOWN; very new account, but admin permission and substantial repository contribution history warrant established-contributor calibration.

The implementation matches the substantive PR description and is identical to the previously reviewed #3113 change. The checkpoint is chain-spec anchored and validated, while its generator RPC remains explicitly opt-in.

Quick checks passed: bash -n scripts/build_all_chainspecs.sh, JSON parsing of both changed Finney specs, and git diff --check. cargo fmt --check --all was skipped because the locked Rust environment could not create its rustup temporary file. The working tree remains clean.

Findings

No findings.

Conclusion

The release-branch port preserves the reviewed checkpoint behavior and includes focused validation and regression coverage. No blocking domain issues were found.

[github-actions]

🔄 AI review updated — Skeptic: SAFE Auditor: 👍