[BUG] MCP slash commands unrecognized when followed by a prompt
Status Closed — not planned
Maintainer reply None cached
Activity 9 comments · opened Aug 27, 2025 · closed Jan 11, 2026
Environment
- Platform (select one):
- [X] Anthropic API
- [ ] AWS Bedrock
- [ ] Google Vertex AI
- [ ] Other: <!-- specify -->
- Claude CLI version: 1.0.93
- Operating System: macOS 15.6.1
- Terminal: zsh
Bug Description
When I invoke any MCP slash command followed by a prompt, the command isn't recognized.
This works: /zen:chat but this doesn't: /zen:chat foo
The error message I get is Unknown slash command: /zen:chat.
This happens with all of my MCP connections, I have verified the problem does not exist on zen specifically.
Steps to Reproduce
- Add MCP server of choice to claude
- Invoke a slash command with a prompt after
Expected Behavior
The command should run, and the string following that slash command should be interpreted as input to that command.
Actual Behavior
I get the error Unknown slash command: /zen:chat
9 Comments
All of my commands are giving me unknown slash command today, whether they have text after or not.
I am having the same experience as @brandon-reinhart . Also, something has changed in the Claude web client and Claude Desktop, so I can't use MCP server prompts anymore. Just yesterday (2025-08-26), it worked just fine.
There has been a regression, you now cannot use prompts from MCPs any more with Claude Code.
Repro:
claude mcp add --transport http --scope project svelte-llm https://svelte-llm.stanislav.garden/mcp/mcp/svelte-llmand try to add any of the prompts. You getUnknown slash command: svelte-llm:Svelteerror, almost like it's not possible to use prompts with spaces.Me too. I added the same mcp server in VSCode and it works fine. Claude Code lists the slash commands from the mcp server prompts, but when I try to run them, I get “Unknown slash command”.
All of my commands had mandatory and optional arguments based on the typescript mcp sdk docs
_Anthropic when it’s time to plagiarize from thousands of authors:_ 🧑💻🔥👩💻
_Anthropic when it’s time to fix basic MCP support (a protocol they invented) in their flagship product:_ 🥱😴💤
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Congrats on uhhh donating MCP to the linux foundation but this is still occurring! :(
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