consensus: anchor checkpoint fast-add

[wolf31o2]

Summary

• enable checkpoint fast-add only after the configured checkpoint header is known in the valid best-header chain
• keep full block validation active when a peer stops its header chain before the checkpoint
• make addblock imports use full consensus validation instead of unconditionally requesting fast-add
• add regression coverage with a valid-PoW block whose coinbase height is consensus-invalid

Validation

• make unit unit-race unit-cover build integration hsd-interop lint vuln workers=2
• go mod verify in the root module, hnsutil, hnsutil/psbt, and chaincfg/chainhash
• release Docker builds and --version smoke tests for linux/amd64 and linux/arm64

The validation used Go 1.26.5, pinned hsd v8.0.0, and a freshly compiled govulncheck v1.6.0.

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Summary by cubic

Anchors fast-add to a known checkpoint header and enforces full consensus validation for addblock imports to prevent bypassing rules with partial header chains.

• Bug Fixes
  • netsync: Enable fast-add only after the checkpoint header is in the best-header view; keep full validation if a peer stops headers before the checkpoint.
  • addblock: Use blockchain.BFNone for imports instead of BFFastAdd.
  • Tests: Added regression for valid-PoW block with invalid coinbase height; updated header path tests to verify fast-add gating.

^{Written for commit aab8c57. Summary will update on new commits.}

Summary by CodeRabbit

• Bug Fixes

  • Block imports now perform complete validation, rejecting blocks with invalid coinbase information.
  • Improved checkpoint handling during blockchain synchronization to prevent fast processing when checkpoint headers are unavailable or invalid.
  • Enhanced reliability when distinguishing valid main-chain blocks from orphaned blocks during import and synchronization.

• Tests

  • Added coverage for invalid block imports and checkpoint-based synchronization scenarios.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: c69d4dc7-13f2-494a-ac89-07f6b2004bd7

📥 Commits

Reviewing files that changed from the base of the PR and between 7aa7481 and aab8c57.

📒 Files selected for processing (4)

• cmd/addblock/import.go
• cmd/addblock/import_test.go
• netsync/manager.go
• netsync/manager_test.go

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📝 Walkthrough

Walkthrough

The block importer now processes imported blocks with normal validation flags instead of fast-add. A regression test constructs a proof-of-work-valid block with an invalid coinbase height and verifies rejection with ErrBadCoinbaseHeight. Header synchronization now validates the next checkpoint header before enabling fast-add. Updated IBD tests cover behavior before and after the checkpoint and verify main-chain anchoring.

Possibly related PRs

• blinklabs-io/handshake-node#66: Adds the mainnet checkpoint data used by checkpoint-related header synchronization logic.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title matches the main change: tightening checkpoint fast-add behavior and anchoring it to the known checkpoint chain.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/checkpoint-anchored-fastadd

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[wolf31o2]

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