feat(consensus): SIP-5 speculative apply — block hash commits state root (Bug B, #751)

[satyakwok]

Draft / WIP — not for merge. Block-executor core for SIP-5 (Bug B, #751): speculative apply at propose so the block hash commits the post-execution state_root, closing the block.hash != justification.block_hash inconsistency.

Design: SIP-5 (B1).

In this PR (block-executor side)

• SPECULATIVE_APPLY_HEIGHT fork gate (default u64::MAX both nets — inert until activated by env)
• Blockchain::speculative_apply_for_state_root — computes the state_root a candidate block would produce on a throwaway clone (justification gate is peer-only, so a propose-time block with no justification still applies)
• Blockchain::is_speculative_apply_height wrapper
• commit-gate: post-fork, a self-produced block with state_root = None is rejected instead of stamp+recompute (the Bug B H1→H2 divergence)

Builds clean (-p sentrix-fork-heights, -p sentrix-core).

Remaining (separate commits)

• Propose-side stamp in bin/sentrix/src/main.rs (refactor build_or_reuse_proposal → single point that stamps state_root + recomputes hash before signing)
• Verify-before-vote on the received-proposal path (re-derive state_root, refuse to prevote on divergence)
• Full regression test (block.hash == justification.block_hash post-fork)

Activation

Fork-gated off. Activation = halt-all + state-root-alignment pre-flight + simul-start, testnet first, then mainnet at a coordinated height. Requires fresh-brain review + testnet bake before activation.

Summary by CodeRabbit

• New Features

  • Added validation helpers for block state root analysis and fork height management.

• Bug Fixes

  • Enforced stricter state root validation for self-produced blocks at/after a designated fork height.
  • Self-produced blocks without state roots are now properly rejected rather than being computed, improving block validation consistency.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 4c64e55d-009d-48f9-99c3-279fd7a9a9bc

📥 Commits

Reviewing files that changed from the base of the PR and between 90ccab3 and b7b1ef0.

📒 Files selected for processing (3)

• crates/sentrix-core/src/block_executor.rs
• crates/sentrix-core/src/blockchain.rs
• crates/sentrix-fork-heights/src/lib.rs

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📝 Walkthrough

Walkthrough

The PR implements SIP-5 / "Bug B" by adding a SPECULATIVE_APPLY_HEIGHT fork gate across three crates. In sentrix-fork-heights, a new compile-time constant SPECULATIVE_APPLY_HEIGHT_DEFAULT (set to u64::MAX, disabled) is added alongside get_speculative_apply_height() and is_speculative_apply_height(height) runtime helpers. Blockchain gains a delegating predicate method is_speculative_apply_height. In block_executor.rs, a new speculative_apply_for_state_root method clones the chain and applies a candidate block to extract the resulting state_root. The apply_block_pass2 state-root path is updated to reject self-produced blocks with state_root=None at or after the fork height with ChainValidationFailed instead of proceeding to the prior stamping behavior.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related issues

• Bug B: block.hash recomputed post-apply doesn't update embedded justification — produces internally inconsistent blocks #751: This PR directly implements "Option B1 — speculative apply at propose time" from issue #751 to fix "Bug B," adding speculative_apply_for_state_root() for pre-proposal state_root computation and fork-height gating to enforce the new behavior.

Possibly related PRs

• sentrix-labs/sentrix#801: Both PRs modify apply_block_pass2 in block_executor.rs in the state_root validation path — this PR adds a rejection rule for state_root=None self-produced blocks post-fork, while #801 changes handling of received_root != computed_root for justified peer blocks.

✨ 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 feat/speculative-apply-state-root

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