Fux
Deterministic knowledge retrieval for AI-assisted codebases — rank from a small git-carried index, fetch content from the systems that own it, verify at answer time.
Status (2026-08-12): M2 shipped — the accelerator is in.
src/fux/exists. From a configured directory:fux ingest # builds the committed .fux/index/*.jsonl (+ the accelerator) fux ask "your question" # ranks with BM25F, cites the source file fux find "your question" # ranked locations, one per line fux answer "a question" # the single best answer the index can giveWarm
askis measured at a worst-case p95 of 27.2 ms on 8 870 RFC documents — against a pre-registered 150 ms bar, where the reference scan takes 4.2 s (prediction R3 PASS, the run).The speed comes from a derived index under
.fux/runtime/— never committed, rebuilt from the committed shards byfux build. It is bound by a differential law: its results are byte-identical to the reference scan's, asserted over thousands of comparisons rather than spot-checked.fux ask --scanforces the reference path.A dense lane exists behind
ask --hybridand is off by default — on the graded corpus it closes three known gaps and breaks nine working queries, so the default is a measurement rather than a preference.URLs can join the corpus through a consumer-owned middleware file (
.fux/middleware/cdp.py, Chrome DevTools Protocol on pure stdlib) — list them one per line in.fux/sources/urls, thenfux ingest --refresh-urls. ADR-0010 + ADR-0011 (both proposed). No graph query lane yet (M3). The v0.26 engine and its docs are archived underarchive/v0.26/, reference-only. The new architecture is specified indocs/paper/the-fux-index-paper.md(§4–§6 knowingly stale until M6) and built againstdocs/PLAN.md.The pruning gate closed (2026-08-09): FAIL. Keeping only each document's top-k terms was measured, twice, against a corpus that could actually test it — no selector came within 35.9 points of preserving candidate recall at a 6 % budget. The committed index carries full postings, permanently — ADR-0003.
The idea
- Sources own content. Repo docs stay in git; Confluence pages stay in
Confluence. Fux never keeps a durable copy (except explicit per-source
snapshotpolicy). - Git carries the index — doc-major, sharded, human-readable JSONL;
full per-document postings, dense binary codes, an extracted link graph,
and a source ledger, one line per document, sorted and content-sharded so
git itself diffs and merges it —
docs/compare/index-format.compare.md. - Answers verify themselves. Rank in the index, fetch the cited
documents live (through a version-keyed cache), re-score passages on the
fetched bytes, cite the fresh sha. (The refer plane is M4; M1's
askcites straight from the committed index.) - Laws: $0 default · stdlib-only · byte-deterministic · offline by default · one ADR per feature, every rule referenced.
The .fux/ directory
Everything fux puts in your repo lives here, and every child is declared as committed or derived (ADR-0011):
| entry | kind | what it is |
|---|---|---|
index/ |
committed | the sharded JSONL index |
sources/ |
committed | line-oriented source lists (urls) |
middleware/ |
committed | your code (cdp.py) — fux never rewrites it |
runtime/ |
derived | M2's accelerator segments (gitignored, CACHEDIR.TAG) |
cache/ |
derived | M4's fetch cache (gitignored, CACHEDIR.TAG) |
Fux writes .fux/README.md and a narrow .fux/.gitignore (derived names
only, never *) if they are missing, and never touches them again. fux doctor fails if the index has been git-ignored and warns about anything
undeclared.
Reading order
docs/paper/the-fux-index-paper.md— architecture + falsifiable predictionsdocs/compare/index-format.compare.md— the committed format, measureddocs/PLAN.md— milestones M0–M8docs/adr/0004-index-format.md— the frozen M1 schema../fux-playground/PLAYGROUND.md— a graded 10-doc corpus to try it on, in a separate sibling repository (clone it next to this one)docs/WORKLOG.md— the running build log
License: MIT.
1 maintainer
Release files for fux-engine 0.32.0
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