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chrome-extensions.sgit.ai — the expensive bugs do not throw

Site version: v0.1.0 (9 September 2026). Full machine-readable index: llms.txt ↗.

Guidance and worked examples for building Chrome extensions, written for the agent that reads them before writing one. Four guides from five weeks building a Manifest V3 browser extension that records a web application's own network traffic, against an undocumented target that changed its entire API stack mid-project.

If you read nothing else

Build a deliberately stupid recorder first. No parsers, no domain model — just keep the bodies.
Verify every derived fact against an artefact the system itself produced.
The expensive bugs do not throw.
Missing is null, and null never becomes 0, '' or {}.
Leave the corrections in.

A narrow instrument, stated before the code

This is an instrument for observing your own session and your own data, on an account you hold, recording only what the service already sent to your browser. It originates no requests, transmits nothing, and captures no message content in any mode. Never originates a request; never blocks, delays or alters a response; never throws into the page; never transmits. See about/participant.html ↗.

One shipped, four specified

One extension has been built — the recorder, v0.16.0. Four more were specified across six months and never shipped: a Key Vault, risk cards on extensions, the Scribe, and a secrets manager, plus two smaller proposals (the manifest as a published profile, and the vault as the extension's storage layer). See the arc ↗ and the unbuilt ↗.

The four guides — read 01 first

Built from the guides

What this site does not cover

The guides are written from one extension: a passive recorder that never originates a request. No page-modifying extensions, injected UI, declarativeNetRequest, OAuth flows, multi-origin content scripts, or Chrome Web Store publishing guide. The recorder's original target is never named.

CC BY 4.0 (site text, rubric, guides); code snippets CC0/MIT.