# The frontier and "as of block H"

How far each stage of BTI and its appendix has got, why the cursors are ordered books ≤ claims ≤ census, and why every block.space figure carries its height.

URL: https://blockspace.wiki/concepts/the-frontier/

Every figure [BTI](https://blockspace.wiki/glossary/bti/) publishes is true up to some block. [The frontier](https://blockspace.wiki/glossary/the-frontier/) is the name for that block. Ruleset v1 gives its core meaning: the frontier is the height every registered protocol has been searched to. On block.space the rule for readers is plain: a board says [as of block H](https://blockspace.wiki/glossary/as-of-block-h/), and a number without its height is not shown.

## Three cursors

BTI's design runs three stages, and each keeps its own [cursor](https://blockspace.wiki/glossary/cursor/), a saved height recording how far that stage has completed:

| cursor | stage | what it means |
|---|---|---|
| census | T1, observation | every block up to here has been counted, byte by byte |
| claims | T2, catalogue | every registered protocol has been searched up to here |
| books | T3, accounting | the books are written up to here |

The standing invariant is **books ≤ claims ≤ census**. Each stage reads only the tier beneath it, so no stage can pass the one below. When the engine follows the chain in steady state, the three advance together and are equal at every commit. When they differ, the books are only as current as the books cursor.

On the latest reading (as of block 972,315, 2026-10-20 12:10:25 UTC):

- census: block 972,318
- claims: block 972,315
- books: block 972,299
- chain tip, from bitcoind: block 972,320

Inside T2 each unit keeps its own cursor too, `claims:<name>`, and the claims cursor can move only past windows every unit has covered and that have been reconciled.

## What moves a cursor, and what stops it

- **Only completed windows count.** An increment commits in one database transaction. An interrupted window is abandoned whole, and rerunning resumes from the cursor, so the frontier only ever states completed windows.
- **The clamp.** No increment may pass the indexed height of any source it depends on: `hi = min(hi, sources, caps)`, checked on every increment. A lagging indexer holds the claims cursor back, and the lag shows in the stage's status.
- **Fail closed.** An unreachable source is a refusal, never a zero. The frontier's meaning, "every registered protocol searched to at least here", cannot be asserted about a protocol whose source could not be asked.
- **Perpetual search.** The ruleset's standing law B35 says a dormant protocol is still searched at every height, forever. A protocol with no recent activity still has to be searched for the frontier to pass.
- **Reorgs.** Facts and state above the fork height are deleted and the increments are rerun. That is cheap because increments are small, and correct because facts below the fork are append-only.

## "As of block H"

The block.space rankings documentation sets the rule: every figure is bounded by a height. A board says "as of block H", where H is the one block the holders appendix is synchronised to. Where a ranking was folded at a different height, or the books are written to another, the detail line names those heights too.

The appendix has its own cursor. It is one row, H, "the block to which every source is reconciled", the lowest of the per-source heights, the books included. The pages print "as of block H" from that row only. The holders data stood at block 972,261 (as of block 972,261, 2026-10-20 12:17:53 UTC).

## Several heights at once

Because each stage and each source has its own cursor, one page can honestly carry several heights. The census is usually nearest the tip, the books follow behind, and the appendix waits for the books. That is why the wiki's live figures each carry their own "as of": a census figure and a books figure read at the same moment can be bounded by different blocks.

The rankings rules add a related one: "Not measured" is never 0. A book the instrument has not measured for a protocol, or a holder the appendix cannot see, is written in words. A zero means a measured zero. See [not measured](https://blockspace.wiki/glossary/not-measured/).

Sources:

- Blockspace Holdings records
- block.space docs: rankings · https://block.space/docs/rankings
- block.space meter and summary APIs · https://block.space/api/summary
- block.space leaderboard API · https://block.space/api/leaderboard

Live figures: frontier as of block 972,315, 2026-10-20 12:10:25 UTC; holders as of block 972,261, 2026-10-20 12:17:53 UTC

Updated: 2026-10-20