Kq – jq but 1.5x faster on paths, from a language with no GC/lifetimes

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GitHub - kanso-lang/kq: jq-style JSON queries, byte-identical to jq -S and faster on paths — written in kanso · GitHub

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kq

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kq

A jq-style JSON query tool, written in kanso. Output<br>is byte-identical to jq -S on every query below — verified with diff, not<br>claimed.

Speed

Interleaved runs, best-of-25, whole-process wall time (startup + read + parse +<br>query + print), Apple M-series. Reproduce: sh bench/kq_race.sh.

workload<br>kq<br>jq 1.7.1

path query, 188 KB (.[0].k0_30)<br>3.2 ms<br>4.8 ms<br>kq 1.49x faster, 25/25 runs

path query, 1.9 MB (.[0].k0_30)<br>15.5 ms<br>25.0 ms<br>kq 1.61x faster, 15/15 runs

full pretty-print, 188 KB (.)<br>12.0 ms<br>12.8 ms<br>kq 1.07x faster, 24/25 runs

full pretty-print, 1.9 MB<br>109 ms<br>106 ms<br>jq 1.03x faster

The path-query gap grows with document size: kq decodes, walks to the subtree,<br>and prints only that — the win compounds as the part you didn't ask for gets<br>bigger. Full-document dumps are printer-bound, where the two are at parity;<br>kq's pretty-printer is the next optimization target on the ledger.

One deliberate difference: on a path that doesn't exist, jq prints<br>null; kq reports an error naming the missing key. kanso treats a missing<br>index as a failure to surface, not a nothing to pass along — if you want<br>jq's silence, query a path that exists. The race harness verifies<br>byte-identity per query before timing anything, which is exactly how this<br>difference was caught.

Use

[file.json] # or pipe json on stdin<br>kq .users[3].name data.json">kq [file.json] # or pipe json on stdin<br>kq .users[3].name data.json

Why it's fast

kq is ~400 lines of kanso sharing its decoder with the standard library — the<br>same decoder that outruns hand-tuned serde_json on the language's json<br>gauntlet. No hand-written parser tricks live in this directory; the speed is<br>the compiler's. The story: kanso-lang.dev/compiler.html.

Specs

sh spec.sh (with KANSO pointing at a kanso build) runs the unit tests,<br>then eleven fixture cases over non-trivial JSON — unicode/CJK/emoji and<br>escapes, precision-edge numbers, deep nesting and empty containers, and the<br>188 KB nested document — each checked against a committed golden AND against<br>live jq -S byte-for-byte. CI gates on all of it.

Intel macs: no GitHub runners exist for that target anymore; build from<br>source (kanso build .) or use Rosetta until a cross-build lands.

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jq-style JSON queries, byte-identical to jq -S and faster on paths — written in kanso

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kq v0.1.0

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Jul 19, 2026

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