Bug: External MCP servers (e.g. Notion) listed in allowedTools but never connected at runtime

Summary

In GitHub Actions (anthropics/claude-code-action@v1), Notion MCP tools are present in SDK options.allowedTools, but the Notion MCP server is never connected at runtime.
As a result, Claude returns NOTION_MCP_UNAVAILABLE and ToolSearch cannot find mcp__notion__* tools.

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Environment

Key | Value
-- | --
Action | anthropics/claude-code-action@v1
Claude Code version (from logs) | 2.1.92
Runner | ubuntu-24.04
Workflow run date | 2026-04-07
Auth mode | claude_code_oauth_token
show_full_output | true

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Minimal Repro Setup

Workflow passes:

• --mcp-config /tmp/mcp-notion.json
• --allowed-tools "mcp__notion__notion-fetch,..."
• NOTION_TOKEN present (non-empty, verified)
• MCP config file exists at /tmp/mcp-notion.json before action starts

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Timing Evidence (rules out file creation race condition)

14:29:05.856 → /tmp/mcp-notion.json written

14:29:05.891 → NOTION_TOKEN is set

14:29:05.905 → MCP config present (verified via cat)

14:29:05.946 → anthropics/claude-code-action@v1 starts

14:29:25.389 → SDK options.allowedTools contains mcp__notion__* ✅

14:29:27.905 → mcp_servers shows only `github_comment: connected`  ❌

Conclusion: --mcp-config is read for allowedTools construction but apparently not used for actual MCP server registration at runtime.

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Expected Behavior

mcp_servers should include:

notion: connected

and mcp__notion__notion-fetch should be callable.

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Actual Behavior

Runtime init shows only:

github_comment: connected

No notion MCP server appears in mcp_servers.

ToolSearch output:

• query select:mcp__notion__notion-fetch → No matching deferred tools found
• query notion → No matching deferred tools found

Final assistant result: NOTION_MCP_UNAVAILABLE

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Evidence from Logs

1. CLAUDE_ARGS includes:
   --mcp-config /tmp/mcp-notion.json --allowed-tools "mcp__notion__notion-fetch,..."
2. SDK options.allowedTools includes all mcp__notion__* entries ✅
3. mcp_servers contains only github_comment (connected), no notion ❌
4. ToolSearch cannot find notion tools
5. Assistant posts NOTION_MCP_UNAVAILABLE

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Control Test (rules out token/permission issues)

Direct Notion API smoke test in a separate workflow (without Claude action) succeeds:

NOTION_TOKEN present

HTTP/2 200

NOTION_FETCH_OK

Page ID: 325765e5-dc96-81fc-b772-e7a3cf48dfa5

Token and page permissions are confirmed valid. The issue is isolated to the action runtime.

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Hypothesis

The claude-code-action appears to have two separate code paths:

1. Tool allowlist: reads --mcp-config and populates allowedTools ✅
2. MCP server registration: does not use --mcp-config to connect the server ❌

github_comment connects because it is hardcoded inside the action.
External servers passed via --mcp-config / claude_args seem to be ignored at the connect step.

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Specific Question for Maintainers

Does --mcp-config passed via claude_args get forwarded to the SDK's MCP server registration step, or only to allowedTools parsing?
Is connecting external MCP servers via --mcp-config currently supported in claude-code-action, or must servers be hardcoded in the action itself?

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Full run links and sanitized logs available on request.

Start at anthropics/claude-code-action@v1 and trace how --mcp-config is handled between allowedTools construction and runtime MCP registration. Reproduce the workflow with /tmp/mcp-notion.json and inspect mcp_servers; done when notion is connected and mcp__notion__notion-fetch is callable.

Written by the indexing model from the issue text.