`#/:chain/:height` opens a block and then rewrites the address to
`#/:chain/:hash`. The redirect is the point, not tidiness: `block` is keyed on
(chain, height) and a reorg overwrites, so a height names a *position* and a
link to one comes to mean a different block the moment the chain forks there. A
hash names one block for good — including after it has lost, which is the only
way an orphan is linkable at all.
`GET /v1/chains/{chain}/blocks/{ref}` takes either spelling; a decimal number
and 32 bytes of hex cannot be confused, so a caller holding a number is not made
to guess which one this API wanted. The same reasoning puts block refs in the
second path segment beside the window: no window name is all digits or 0x plus
64 hex characters.
The answer is assembled from two sources because neither is sufficient, and
they fail at different times:
- The node holds the block and forgets it. Non-canonical bodies go once finality
passes them (blocks-pruning defaults to archive-canonical, and Planck finalises
~100 blocks back), and difficulty is a state read behind a 256-block default.
- The observer holds what the node never had — when the block was seen, whether
that sighting was at the tip — and what it has since forgotten: the difficulty
read while the state behind it still existed.
So resolution degrades in a stated order rather than failing. Node first; a
header it cannot serve falls back to `block_displacement`, which is what makes
an orphan describable at all; a node that is away falls back to the recorded
row. `from_node` tells the reader which they are looking at, and every value
neither source has is spelled out in words — "the body is pruned", "this
observer never saw this block" — because a blank on a block page reads as zero.
Verified against the live chain: a tip block carries difficulty, one extrinsic,
a 1.9 s gap and 473 ms of propagation; height 1000000 keeps its body and loses
difficulty to state pruning; genesis has no author digest and does not panic; a
seeded displacement serves as an orphan with the winner linked, and the winner
lists it in `also_seen`.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jp6a8EDar9ueEhAxzep4V5
rob thijssen
53dac3717b
