What is next-dev-loop?

A verification workflow for Next.js applications, a JavaScript framework, while a development server is running. It checks the app through Next.js's own runtime information and a real browser.

Checking routes, server-rendered behavior, browser output, console errors, network activity, and other runtime effects after code changes.

A successful build or type check does not prove that pages, browser behavior, or runtime errors work correctly.

next-dev-loop — Skill for Claude Code and Codex by sanity-io

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add sanity-io/next-sanity --skill next-dev-loop

Clone the repo

git clone --depth 1 https://github.com/sanity-io/next-sanity

Made for: Claude Code, Codex.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/sanity-io/next-sanity/next-dev-loop/github.svg)](https://agentmods.dev/skills/sanity-io/next-sanity/next-dev-loop)

Your own site

<a href="https://agentmods.dev/skills/sanity-io/next-sanity/next-dev-loop"><img src="https://agentmods.dev/badge/skills/sanity-io/next-sanity/next-dev-loop/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/sanity-io/next-sanity/next-dev-loop"><img src="https://agentmods.dev/badge/skills/sanity-io/next-sanity/next-dev-loop.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 68 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,007 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.

Origin 94% copy Near-identical to another mod in the catalogue.

Token cost

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	$0.00068	$0.02007
Opus 5.5	$0.00027	$0.00803
Sonnet 5.5	$0.00014	$0.00401
Haiku 4.5	$0.00007	$0.00201

Measured 1mo ago against content hash 07c8721871d5, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

next-dev-loop scanned grade A with 1 finding 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 1mo 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

again. Don't fall back to `curl`; it bypasses the browser you're

Origin

This is a copy

94% identical to next-dev-loop — 47 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/next-dev-loop/SKILL.md · 189 lines

How it starts

The opening of the file, as written. The whole thing — 189 lines — stays where its author put it; the contents beside it link to each section on GitHub.

next-dev-loop

The edit/verify rhythm during next dev — make a change, then confirm it actually works at runtime, not only that the types or the build are happy.

You verify through two views of the same running app:

/_next/mcp — an HTTP endpoint Next.js exposes about itself. Knows framework-specific things: routes, segments, RSC, server actions, server logs, and errors as Next.js saw them. Call tools/list for the current surface.
agent-browser — a CLI that drives a real Chrome. Knows framework-agnostic browser things: DOM, console, network, React fiber, vitals. Before driving it, run agent-browser skills get core once for the version-matched usage guide — don't guess subcommands from memory.

The two views cross-check each other.

requires

Next.js 16.3+ with Turbopack — /_next/mcp plus the proactive compile check via get_compilation_issues.
agent-browser >= 0.31.1 — React introspection, worktree-scoped session id, idempotent --restore, and launch flag reconciliation.

These are hard floors, not soft preferences. If anything is missing, tell the user how to upgrade and stop. Don't fall back to grepping source or to a weaker probe — this skill assumes both views are live at the versions above.

Upgrade Next.js: pnpm next upgrade (or npx next upgrade). Docs: https://nextjs.org/docs/app/getting-started/upgrading (version-16 guide: https://nextjs.org/docs/app/guides/upgrading/version-16)
Install or upgrade agent-browser: npm i -g agent-browser@latest. If the CLI isn't on PATH, install it before continuing — preflight expects to invoke it directly.

preflight

Once per session, confirm both views are live.

Open agent-browser at the target URL, restoring saved login state when present. First derive one stable session id for this checkout and use it for every agent-browser command:
```
SESSION="$(agent-browser session id --scope worktree --prefix next-dev-loop)"
export AGENT_BROWSER_SESSION="$SESSION"
export AGENT_BROWSER_RESTORE="$SESSION"
```

Read the full file on GitHub · 189 lines

Changes

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.

1mo ago First seen · 189 lines · 68 tokens per session scan A 07c8721871d5

Subscribe to this mod's changes

next-dev-loop is a skill published in the GitHub repository sanity-io/next-sanity (956 stars, last pushed today), licensed MIT. It adds 68 tokens to every session and 2,007 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). It is 94% identical to next-dev-loop, differing in 47 lines, and is treated as a copy.

Frontend Testing hook nextjs preview real-time sanity toolkit

server-side-calls

Call tRPC procedures directly from server code using t.createCallerFactory() and router.createCaller(context) for integration testing, internal server logic, and custom API endpoints. Catch TRPCError and extract HTTP status with getHTTPStatusCodeFromError(). Error handling via onError option.

trpc/trpc · 61 tokens

pytest-suite

Write or extend the backend test suite following this project's conventions. Use when adding tests for a new service/route/repository, when coverage is missing, or when asked to test a feature. Knows the mocked-session + httpx AsyncClient setup so tests run with no database.

vstorm-co/full-stack-ai-agent-template · 59 tokens

relay-80-100-workflow

Use when writing agent-relay workflows that must fully validate features end-to-end before merging. Covers the 80-to-100 pattern - going beyond "code compiles" to "feature works, tested E2E locally." Includes repair-before-failure validation gates, review-depth fresh-eyes review/fix loops with test hardening, PGlite…

AgentWorkforce/relay · 115 tokens

next-dev-loop

Getting it into your agent

Wrote this? Show the measurements

What it costs to keep this loaded

Grade A, and why

Makes network callslowCapability

This is a copy

How it starts

next-dev-loop

requires

preflight

What this file has done since we first saw it

Other skills, from other repositories

server-side-calls

pytest-suite

relay-80-100-workflow

browser-testing-with-screenshots

implement-feature

verify-work