Blockchain fundamentals
Chain reorganisations: why recent inclusion can change
A node can replace its recent chain view when a different valid branch becomes canonical under the consensus rules.
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Competing histories
Networks can temporarily produce competing valid blocks. Nodes use their consensus and fork-choice rules to determine which history to follow. A reorganisation replaces a portion of the previously followed branch, potentially moving or removing transactions that appeared in that branch.
This is why inclusion, confirmation depth and finality should not be treated as synonyms. The relevant assurance depends on the chain and its consensus mechanism. A wallet showing a transaction in a recent block does not independently establish irreversible settlement under every possible failure model.
The accounting consequences
An exchange or indexer must handle the reversal of a credited observation when its supporting block is no longer canonical. Applications that react to the first event without rollback logic can display incorrect balances or perform an offchain action too early.
For an investigation, preserve the block hash alongside the height and transaction identifier. A height alone can refer to a different block after a reorganisation. Snapshots and incident timelines should explain whether a cited event was merely observed, confirmed under a policy or finalised under the protocol.