[BUG] plugin:github:github MCP fails with HTTP 400 — malformed JSON-RPC payload missing version tag

up pls

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did you solved it?

Up

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also happens on linux

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@claude fix this, open a PR referencing this issue, review it, merge it, and tag a new release. Top priority, no mistakes

I was able to fix my GitHub MCP by adding GITHUB_PERSONAL_ACCESS_TOKEN on my Claude global config

edit ~/.claude/settings.json

{
   "env": {
      "GITHUB_PERSONAL_ACCESS_TOKEN": "token"
   }
}

It can also be fixed by adding EXPORT GITHUB_PERSONAL_ACCESS_TOKEN=token in your shell profile, like ~/.zshrc

I was able to fix my GitHub MCP by adding GITHUB_PERSONAL_ACCESS_TOKEN on my Claude global config edit ~/.claude/settings.json { "env": { "GITHUB_PERSONAL_ACCESS_TOKEN": "token" } } It can also be fixed by adding EXPORT GITHUB_PERSONAL_ACCESS_TOKEN=token in your shell profile, like ~/.zshrc

I can confirm it works.

For some reason this doesn't

I was able to fix my GitHub MCP by adding GITHUB_PERSONAL_ACCESS_TOKEN on my Claude global config edit ~/.claude/settings.json { "env": { "GITHUB_PERSONAL_ACCESS_TOKEN": "token" } } It can also be fixed by adding EXPORT GITHUB_PERSONAL_ACCESS_TOKEN=token in your shell profile, like ~/.zshrc

i was try this, but still not work

I was able to fix my GitHub MCP by adding GITHUB_PERSONAL_ACCESS_TOKEN on my Claude global config edit ~/.claude/settings.json { "env": { "GITHUB_PERSONAL_ACCESS_TOKEN": "token" } } It can also be fixed by adding EXPORT GITHUB_PERSONAL_ACCESS_TOKEN=token in your shell profile, like ~/.zshrc

this works for me, thanks

Make sure to follow these instructions:

🔗 https://github.com/github/github-mcp-server/blob/main/docs/installation-guides/install-claude.md

From your terminal

⚠️ NOT in Claude Code CLI

export GITHUB_PAT=<YOUR_PAT_HERE>
claude mcp add-json github '{"type":"http","url":"https://api.githubcopilot.com/mcp","headers":{"Authorization":"Bearer $GITHUB_PAT"}}'

Troubleshooting

You may need to remove your local Github MCP configuration if was improperly configured before:

claude mcp list  #shows all servers availabe 
claude remove github

This issue has also occurred for me whilst, being on windows. So the macos label is false.

Adding a reproduction for what looks like a second, distinct cause of this same 400. The original report diagnoses a malformed JSON-RPC payload missing the "jsonrpc": "2.0" tag. On my machine the payload is fine and the auth header is the problem, so anyone landing here should check which error their debug log actually names before trying a fix.

Claude Code 2.1.235, macOS 26.5.2, plugin:github:github from the official marketplace.

The error

From ~/.claude/debug/<session>.txt:

[ERROR] MCP server "plugin:github:github" Connection failed (400):
Streamable HTTP error: Error POSTing to endpoint:
bad request: Authorization header is badly formatted

Note this is not malformed payload: invalid message version tag, which is what the OP saw.

Cause

The plugin's .mcp.json sets:

"headers": { "Authorization": "Bearer ${GITHUB_PERSONAL_ACCESS_TOKEN}" }

Claude Code expands that from its own process environment. Exporting the variable in .zshenv or .zshrc does not reach it, so the header goes out empty (or as the literal ${...}) and GitHub rejects it.

Isolating which side is broken

Four requests to the same endpoint, same account:

| Request | Result |
|---|---|
| Valid token + valid initialize | 200 |
| Valid token + empty body | 400 POST requires a non-empty body |
| Empty token + valid initialize | 400 bad request: Authorization header is badly formatted |
| Literal ${GITHUB_PERSONAL_ACCESS_TOKEN} + valid initialize | 400 bad request: Authorization header is badly formatted |

Rows 3 and 4 reproduce the logged error exactly. Row 2 is the OP's failure mode. Row 1 confirms the endpoint, token and account are fine.

Reproduction

You cannot reproduce this from a shell that already exports the token, because the child claude process inherits it. That cost me a wrong conclusion, so unset it explicitly:

# with no env key in settings.json
env -u GITHUB_PERSONAL_ACCESS_TOKEN claude --debug -p "say ok"
# -> plugin:github:github ... Authorization header is badly formatted

Add the token to env in ~/.claude/settings.json:

{ "env": { "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_xxx" } }

# same command, variable still unset in the environment
env -u GITHUB_PERSONAL_ACCESS_TOKEN claude --debug -p "say ok"
# -> plugin:github:github: Successfully connected (transport: http) in 440ms

This is the workaround @ph7jack posted, and the A/B above may explain why the shell-export half of it works for some people and not others: only the settings.json entry is guaranteed to land in the process that expands the header. Whether the export works depends on how that particular Claude Code process was launched.

Two things that cost time

claude mcp list reported ✔ Connected for this server the whole time it was failing, and a direct initialize and tools/list against the endpoint both returned 200. The only accurate signal was ~/.claude/debug/*.txt.

It may also be worth failing loudly when a referenced variable is unset at expansion time, rather than sending Bearer and surfacing a generic remote 400 that points at the wrong layer.