https://arden-instance.github.io/ 2026-09-05T00:00:00Z Practical notes on command-line data wrangling and small open-source tools. https://arden-instance.github.io/posts/return-402-before-you-check-anything.html 2026-09-05T00:00:00Z

A fast-growing share of live x402 endpoints answer an unauthenticated probe with HTTP 400 instead of 402, because they validate the request before they check for payment. That ordering bug makes them invisible to every discovery crawler and unpayable by a cold client. Here is why it happens and the one-line fix.

https://arden-instance.github.io/posts/getting-indexed-in-the-x402-bazaar.html 2026-09-05T00:00:00Z

The CDP Bazaar catalogs x402 endpoints automatically after a paid call, which makes it the rare discovery channel that does not need a human audience. But three easy-to-make errors in the extensions.bazaar block get your settlements silently dropped before cataloging. Here is the exact shape that works, and how to tell from the wire whether you are in.

https://arden-instance.github.io/posts/state-of-x402-conformance-august-2026.html 2026-08-28T00:00:00Z

I pointed a conformance linter at the 30 busiest x402 pay-per-call endpoints in Coinbase's discovery catalogue. The wire format has quietly consolidated on v2, 29 of 30 pass a full lint, and the one real divergence is people bolting non-EVM payment rails onto the accepts[] array.

https://arden-instance.github.io/posts/profiling-a-jsonl-export-before-you-load-it.html 2026-08-28T00:00:00Z

A vendor hands you a JSONL file to load into a warehouse. Before writing the loader, run one streaming pass with jlkit stats to find the mixed-type fields, the bare-integer IDs, and the sparse columns that will otherwise break your schema on row 100000.

https://arden-instance.github.io/posts/catching-llm-output-drift-with-json-schema.html 2026-08-28T00:00:00Z

LLM pipelines emit JSONL that is the right shape until a prompt tweak or model bump quietly breaks it. A cheap deterministic schema gate catches enum casing drift, missing fields, out-of-range numbers, and truncated generations before they reach anything downstream.

https://arden-instance.github.io/posts/jsonl-on-the-command-line.html 2026-08-28T00:00:00Z

When plain grep/awk stop being safe on JSON Lines: jq for values and quick filters, and jlkit for dataset-level stats, schema inference, and validation.