jwx is a Go library implementing JOSE security standards for signing, encrypting, parsing, and verifying JSON-based messages and tokens such as JWTs, JWSs, JWEs, and JWKs. Go developers use it to add authentication and related cryptographic protocols to products, and the catalogue includes guidance for assistants helping developers work with its version 4 API.
Borrowing it
Nothing to install: this file belongs to lestrrat-go/jwx. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/lestrrat-go/jwx/develop/v4/AGENTS.mdgit clone --depth 1 https://github.com/lestrrat-go/jwxWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/instructions/lestrrat-go/jwx/agents-md)<a href="https://agentmods.dev/instructions/lestrrat-go/jwx/agents-md"><img src="https://agentmods.dev/badge/instructions/lestrrat-go/jwx/agents-md/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/instructions/lestrrat-go/jwx/agents-md"><img src="https://agentmods.dev/badge/instructions/lestrrat-go/jwx/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.03351 | $0.03351 |
| Opus 5.5 | $0.01340 | $0.01340 |
| Sonnet 5.5 | $0.00670 | $0.00670 |
| Haiku 4.5 | $0.00335 | $0.00335 |
Grade A, and why
jwx AGENTS.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 14d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 296 lines — stays where its author put it; the contents beside it link to each section on GitHub.
AGENTS.md
For Module Consumers
If you are writing code that uses jwx (not developing jwx itself):
- Examples: See
github.com/jwx-go/examplesfor runnable usage patterns (locally atexamples/when checked out viago.work) - Documentation: See
docs/directory and package READMEs - API Reference: Use
go docor https://pkg.go.dev/github.com/lestrrat-go/jwx/v4 - Migrating from v3? See
MIGRATION.mdfor a complete guide, andgithub.com/jwx-go/jwxmigratefor machine-readable migration rules and automated checking
The rest of this document focuses on developing the jwx library itself.
Go Version
This project requires Go 1.26.0 or later. Check go.mod for the exact version.
GOEXPERIMENT
v4 depends on encoding/json/v2, which is behind GOEXPERIMENT=jsonv2 on Go 1.26 and part of the standard library from Go 1.27 on. The Makefile probes the toolchain and rewrites GOEXPERIMENT to match it, adding jsonv2 on Go 1.26 and removing it on Go 1.27, so make targets work on both even when your shell already exports the variable. Experiments other than jsonv2 are left alone. scripts/test-companion.sh carries the same probe.
A direct go build, go test, or go run invocation on Go 1.26 must set it:
GOEXPERIMENT=jsonv2 go test ./...
GOEXPERIMENT=jsonv2 go build ./...
Without this, Go 1.26 builds fail with build constraints exclude all Go files errors.
On Go 1.27 do not set it. Naming an experiment the toolchain already ships for real rebuilds the standard library under a non-default configuration for no benefit.
Module Path vs Physical Layout
This repository uses a flat layout with vanity import paths. There is no physical v4/ directory.
| Branch | Module Path | Physical Root |
|---|---|---|
develop/v4 |
github.com/lestrrat-go/jwx/v4 |
/ (repo root) |
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 14d ago Changed · +8 lines · +195 tokens per session 9a7125f9a852
- 28d ago Changed · +7 lines · +98 tokens per session 30964e12c19d
- 1mo ago First seen · 281 lines · 3,058 tokens per session scan A 66abdef07afa
jwx AGENTS.md is an instructions file published in the GitHub repository lestrrat-go/jwx (2,440 stars, last pushed yesterday), licensed MIT. It adds 3,351 tokens to every session, about $0.0134 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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