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Reported issues for next-devtools-mcp

Pod holds 20 of 26 problems reported by people outside the maintainer team. Issues filed by the project's own owners, members and collaborators are excluded entirely — a maintainer's release checklist is not a warning to a prospective user.

Back to next-devtools-mcp.

Most discussed

nextjs_call fails with 'Expected object, received string' when MCP clients serialize args as JSON string

Bug Description

The nextjs_call tool fails with a Zod validation error when MCP clients pass the args parameter as a serialized JSON string instead of a parsed object. This is a known pattern across the MCP ecosystem where certain clients serialize object-typed parameters before sending them to the server.

Error:

Expected object, received string

The nextjs_index (action: discover_servers and list_tools) works correctly. Only nextjs_call (action: call_tool) fails b

Read the thread · 2026-04-14 · closed · external user · 2 comments

Issues with nextjs_docs and nextjs-docs://llms-index

I'm having issues where the model (in this case, GPT 5.2 Codex in OpenCode) complains it can't get the Next.js docs index or llms-index. Here's the output:

Details

Thinking: Attempting to access Next.js docs
I’m trying to read the required nextjs-docs://llms-index resource via the read tool to comply with documentation access requirements, but previous attempts failed; I’ll retry reading it directly to resolve this blocker before proceeding.

→ Read ne

Read the thread · 2026-01-29 · open · external user · 2 comments

Codex goes idle after next-devtools.init

I have this in my AGENTS.md:

**Next.js Initialization**: When starting work on a Next.js project, automatically
call the `init` tool from the next-devtools-mcp server FIRST. This establishes
proper context and ensures all Next.js queries use official documentation.

For every new session, Codex runs next-devtools.init then goes idle with the message "Initialization complete." – because that's what it's told to do – and I have to respond with "Continue" or something like that. Every. S

Read the thread · 2025-12-20 · closed · external user · 3 comments

Bun Runtime

Hi, Can you please add the bun runtime availability that will be helpful, thank you.

Read the thread · 2025-12-04 · closed · external user · 7 comments

[Bug] Auto-discovery fails on Windows - discover_servers returns 406 due to missing Accept header

Environment

Operating System:

  • Windows 11 (MINGW64_NT-10.0-26200)

Versions:

  • next-devtools-mcp: 0.3.3 (latest)
  • Next.js: 16.0.3
  • Node.js: v24.9.0
  • Bun: 1.3.0 (used as package manager)
  • React: 19.2.0

MCP Configuration (.mcp.json): { "servers": { "next-devtools": { "type": "stdio", "command": "bunx", "args": ["next-devtools-mcp@latest"], "env": {} } } }

Next.js Configuration: const nextConfig: NextConfig = {

Read the thread · 2025-11-18 · closed · external user · 5 comments

MCP Discovery Failure on Windows with Cursor (Next.js 16)

MCP Discovery Failure on Windows (Next.js 16)

  • Environment

    • Windows 11
    • Node.js v25.0.0. (tried on v20 too)
    • Node/npm per next dev
    • next@16.0.0
    • next-devtools-mcp@^0.2.1
    • .cursor/mcp.json includes next-devtools and Sentry entries

  • Steps Taken

    • Install project dependencies (npm install)
    • Start dev server: npm run dev
      • App reachable at http://localhost:3000
      • MCP endpoint responds (requires Accept: text/event-stream)
        • Power

Read the thread · 2025-10-23 · closed · external user · 6 comments

CLI: code --add-mcp <json> strips quotes when invoked from PowerShell on Windows

CLI: code --add-mcp <json> loses quotes when invoked from PowerShell (Windows)

Summary

Invoking code --add-mcp '<json>' from PowerShell (pwsh) causes the JSON double-quotes to be stripped or mangled, leading to JSON parse errors. Running the VS Code CLI implementation (cli.js) directly with node succeeds, which suggests the issue is in the PowerShell → cmd handoff or the code wrapper's argument handling.

Environment

  • OS: Windows 11 Pro (Edition: Windows 11 Pro, Versio

Read the thread · 2025-10-23 · closed · external user · 2 comments

Claude code failed connection

I'm adding the MCP using this command

claude mcp add next-devtools npx next-devtools-mcp@latest

latest claude version, cli and vscode extension but still failed connection with the MCP :/

Read the thread · 2025-10-22 · closed · external user · 2 comments

Most recent

browser_eval wrapper uses outdated field names: ref / startRef / endRef / selector — type, click, drag, evaluate, and fill_form all fail

Summary

The browser_eval action wrapper in dist/tools/browser-eval.js sends parameter names that no longer match @playwright/mcp's tool schemas. As a result, type, click, evaluate, drag, and fill_form all return InputValidationError. Only start, navigate, screenshot, console_messages, list_tools, and close work.

The bug is the same class as #94 / #98 (Playwright MCP renamed browser_screenshot to browser_take_screenshot), but for several other tools.

Versi

Read the thread · 2026-05-15 · closed · external user · 0 comments

Docs: warn that NEXT_DEVTOOLS_HOST env var can redirect MCP off localhost

NEXT_DEVTOOLS_HOST silently overrides the localhost default in src/_internal/nextjs-runtime-manager.ts:39:

const MCP_HOST = process.env.NEXT_DEVTOOLS_HOST ?? "localhost"

…and is used to construct the fetch target at lines 68 and 306. But the README (checked in v0.3.10 and at HEAD on the default branch) has zero mentions of NEXT_DEVTOOLS_HOST, so nothing warns a developer that

Read the thread · 2026-04-21 · closed · external user · 0 comments

Gives warning on Windows 11

When working in Windows 11 inside Git Bash this MCP server gives the following warning for Claude Code:

[Warning] [next-devtools] mcpServers.next-devtools: Windows requires 'cmd /c' wrapper to execute npx

The same seems to be the cause of Claude Code not being able to auto-discover other MCP servers.

Read the thread · 2026-04-04 · open · external user · 0 comments

MCP server failed on exit

  • Claude Code v2.1.71
    • No statusLine configured
  • next-devtools-mcp 0.3.10
  • next 16.1.6
  • macOS Sequoia 15.7.4
  • Apple M1 Pro

Everything works correctly. Claude reports (/mcp)

next-devtools · :heavy_check_mark: connected

After prompting to make sure, Claude reports

The ... dev server is running on port 4200, and the next-devtools MCP connected successfully.

However when exiting Claude (e.g. with /exit), it consistently reports

1 MCP server failed

With this being the only M

Read the thread · 2026-03-09 · closed · external user · 0 comments

Dependency security risk - Anthropic's MCP TypeScript SDK has a ReDoS vulnerability

Dependency security risk - Anthropic's MCP TypeScript SDK has a ReDoS vulnerability

@modelcontextprotocol/sdk < v1.25.2 affected patched version v1.25.2 and higher

Impact A ReDoS vulnerability in the UriTemplate class allows attackers to cause denial of service. The partToRegExp() function generates a regex pattern with nested quantifiers (([^/]+(?:,[^/]+))) for exploded template variables (e.g., {/id}, {?tags*}), causing catastrophic backtracking on malicious input.

Who is affected: MCP

Read the thread · 2026-02-18 · closed · external user · 1 comment

Chromium Support

If working on linux arm64, the only chrome browser build is chromium. Any plans on supporting chromium?

Read the thread · 2026-02-10 · closed · external user · 0 comments

Security: next-devtools-mcp pins vulnerable undici (GHSA-g9mf-h72j-4rw9)

Problem

next-devtools-mcp depends on a vulnerable version of undici flagged by npm audit.

Advisory: GHSA-g9mf-h72j-4rw9 Undici has an unbounded decompression chain in HTTP responses on Node.js Fetch API via Content-Encoding (resource exhaustion).

npm audit reports:

  • undici 7.0.0 - 7.18.1: moderate severity
  • next-devtools-mcp depends on vulnerable versions of undici

Current versions (from lockfile)

  • next-devtools-mcp: 0.3.10
  • undici: 7.16.0 (pinned as a direct dependency of n

Read the thread · 2026-02-06 · closed · external user · 0 comments

CVE-2026-0621

There's a security vulnerability introduced by @modelcontextprotocol/sdk

Affected versions: < 1.25.2 Patched version: 1.25.2

Read the thread · 2026-01-09 · closed · external user · 0 comments

Won't calling process.exit(0) in browser-eval-manager cause a bug?

src/_internal/browser-eval-manager.ts

// browser-eval-manager.ts
process.on("SIGINT", async () => {
await stopBrowserEvalMCP()
process.exit(0) <--- this part
})

process.on("SIGTERM", async () => {
await stopBrowserEvalMCP()
process.exit(0) <--- this part
})

Won't telemetry data be lost if I exit immediately?

Read the thread · 2026-01-09 · open · outside contributor · 0 comments

Playwright screenshot tool fills context window

The Playwright screenshot tool seems to fill the model's context window with base64-encoded image data. Could this data be omitted from the tool response, with the model directed to just read the screenshot image file? 

⏺ next-devtools - browser_eval (MCP)(action: "screenshot")
  ⎿  ⚠ Large MCP response (~25.1k tokens), this can fill up context quickly         
  ⎿ {"success":true,"action":"screenshot","result":{"content":[{"type":"text","text"
    :"### Result\nTook the viewport screensh

[Read the thread](https://github.com/vercel/next-devtools-mcp/issues/104) · 2025-12-09 · closed · outside contributor · 0 comments

### CVE-2025-66414

https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-w48q-cv73-mx4w

Transitive dependency @modelcontextprotocol/sdk 1.21.0 is introduced via
> next-devtools-mcp 0.3.6  @modelcontextprotocol/sdk 1.21.0

[Read the thread](https://github.com/vercel/next-devtools-mcp/issues/103) · 2025-12-09 · closed · external user · 0 comments

### nextjs_index can’t find dev server in Codex CLI even though Next 16 MCP endpoint is reachable

I’m trying to use next-devtools-mcp from the Codex CLI and running into a situation where nextjs_index reports no dev servers, even though:

a Next.js 16 dev server is running and healthy, and
the MCP endpoint at /_next/mcp is reachable from the same environment.
This exact project works with Next DevTools in GitHub Copilot; the problem only appears when using the MCP server via Codex.

Environment

Host: Windows 11 + WSL2
MCP client: Codex CLI (running inside WSL/Ubuntu)
Project: Next.js 16 app

[Read the thread](https://github.com/vercel/next-devtools-mcp/issues/99) · 2025-12-01 · closed · external user · 0 comments

The remaining reports are on [the project's issue tracker](https://github.com/vercel/next-devtools-mcp/issues).