Knowledge: split-tunnel persistence — sparse append on write, resident fold on read (measured: 0.72 ms)

[AdaWorldAPI]

What

Documentation only. Records a measured persistence pattern as a globally available knowledge doc, so the next consumer adopts it instead of re-deriving it.

• .claude/knowledge/split-tunnel-sparse-append-resident-fold.md covers the pattern, its seven rules, the measurements, the scope, and how to adopt it.
  • Write: sparse (version, owner, op, row, lane, present, value) records, one Lance version per batch. Never updated in place, never compacted.
  • Recovery: Lance is read once, at replay. Replay installs the records in memory only after every batch has applied.
  • Read: every read is a Quack / mask-risc fold over the in-memory records. The newest write wins by append order, with no sort.
• Board entry 2026-10-10-split-tunnel-sparse-append-resident-fold.md, with the index regenerated (entries_index.py --write; --check passes).
• One line in the CLAUDE.md knowledge list, so the doc is found from the session entry point.

Why it belongs here

This is the first measured instance of two working models already on this board:

• "newest-first over append-only", from 2026-09-23-stable-row-ids-…;
• the persistence half of the alpha split tunnel / merge-on-read SparseDelta, from 2026-10-05-quack-storage-portability.md.

It applies the existing cost rule from 2026-09-24-cost-scales-with-dirty-rows-…: one write costs about 10⁶ folds, and a Lance scan is recovery cost.

The Alpha* types are not touched. AlphaOverlay carries no payload, so this is the persistence half beside it.

Evidence

The reference implementation is HubSPO-rs hubspo-store::log (#23–#25 there), measured in release on 2026-10-10 over 1.2M log records, 1,000 versions and 1,001 fragments:

read	median
history, resident fold	0.72 ms
replay, once at startup	532 ms
history by scanning Lance per read	336 ms
history by address index into in-place updates	46 ms
budget	< 20 ms

Disable runs there were all red: the resident-version check, installing before replay validates, commit not extending the in-memory records, each term of the history program, and the I32 sign bit.

Scope: labelled MEASURED for one consumer and carrier shape, and WORKING-MODEL for NodeRow / facet payloads, multi-mailbox logs, and in-memory sets larger than memory. The changed_coordinates representation stays open.

supersession_index.py regenerates identically, and citation_decay.py --since origin/main reports no new decay.

🤖 Generated with Claude Code

https://claude.ai/code/session_01PPcakjk7ioQsnasmNDtc5z

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Generated by Claude Code

Summary by CodeRabbit

• Documentation
  • Added guidance on sparse append-only persistence and reads folded from resident records, including replay validation, writer-race handling, measured performance, and adoption limits.
  • Added the guidance to the knowledge-base index and board-entry listing.

[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-10T20:40:39.268290Z	b3352b9	PR opened

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📒 Files selected for processing (4)

• .claude/board/entries/2026-10-10-split-tunnel-sparse-append-resident-fold.md
• .claude/board/entries/README.md
• .claude/knowledge/split-tunnel-sparse-append-resident-fold.md
• CLAUDE.md

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[chatgpt-codex-connector]

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