Bitcoin keeps no active-chain record of discarded stale blocks, and
live monitoring is recent. Merge-mined child chains preserve
independent evidence of those blocks reaching back to before anyone
was watching.
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1. Forks happen, stales vanish
When two miners find a valid block at the same height,
consensus keeps one on the canonical chain and discards the
losing stale block.
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2. Merge mining stamps a copy
Merge-mined chains reuse Bitcoin's proof of work. Each child
block carries a
merge-mining proof
embedding the exact Bitcoin header the miner was hashing.
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3. Child chains never forget
When Bitcoin drops a losing block, any child block that
committed to it keeps that embedded header permanently in its
own chain history.
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4. Recover and classify
Scraping child chains and checking their embedded headers
against Bitcoin Core classifies each parent as canonical,
stale, strict orphan (matching BIP34 height and nBits), or
weak orphan (matching timestamp nBits).