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Add prev_blockhash validation to CheckPoint#2115

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evanlinjin wants to merge 14 commits intobitcoindevkit:masterfrom
evanlinjin:cp_entry
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Add prev_blockhash validation to CheckPoint#2115
evanlinjin wants to merge 14 commits intobitcoindevkit:masterfrom
evanlinjin:cp_entry

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@evanlinjin evanlinjin commented Feb 5, 2026 •
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Closes #2021
Related to #2076
Replaces #2024
Replaces #2091

Description

This PR adds prev_blockhash awareness to CheckPoint, enabling proper chain validation when merging checkpoint chains that store block headers or similar data with previous block hash information.

Notes to the reviewers

This PR replaces some prior attempts:

Changelog notice

Added:
- `ToBlockHash::prev_blockhash()` - optional method to expose previous block hash
- `CheckPointEntry` - new type for iterating with `prev_blockhash` awareness, yielding "placeholder" entries for heights inferred from `prev_blockhash`
- `ApplyBlockError` - this is a new error type with two variants; `MissingGenesis` and `PrevBlockhashMismatch`. The second variant is a new error case introduced by `prev_blockhash` awareness.

Changed:
- `CheckPoint::push` - now errors when `prev_blockhash` conflicts with current tip (contiguous heights)
- `CheckPoint::insert` - now evicts/displaces checkpoints on `prev_blockhash` conflict
- `merge_chains` - now validates `prev_blockhash` consistency when merging
- `LocalChain<D>` generic parameter - relaxed constraint to `D: Clone` instead of `D: Copy`.

Checklists

All Submissions:

New Features:

  • I've added tests for the new feature
  • I've added docs for the new feature

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Reviewers

@ValuedMammal ValuedMammal Awaiting requested review from ValuedMammal

@oleonardolima oleonardolima Awaiting requested review from oleonardolima oleonardolima is a code owner

@nymius nymius Awaiting requested review from nymius

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@evanlinjin evanlinjin

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bug Something isn't working

Projects

BDK Chain
Status: Needs Review

Milestone

Chain 0.24.0

Development

Successfully merging this pull request may close these issues.

Ensure CheckPoint chain methods validate and link via previous blockhash

3 participants

@evanlinjin @nymius @ValuedMammal