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Mentions

Use @ in the chat composer to point an agent at an exact file or a connected tool.

Type @ in the message box and a picker opens with two kinds of things to point at: your connected tools and the files in the workspace. Picking one puts a mention in your message, so the agent works with exactly what you meant.

The mention picker open above the composer, with arXiv and Hugging Face under MCP servers and workspace files such as README.md and configs/lora-8b.yaml below
Type @ to open the picker: connected tools first, then files.

When to use it

  • Mention a file when the answer depends on a specific file the agent might otherwise guess at, like one of two config.yaml files.
  • Mention a tool when you want a particular source, like arXiv or Hugging Face.
  • For files outside the workspace, attach them instead.
  • To bring in an agent, ask Optimus or chat with the agent directly; the composer's @ covers files and tools.

Why it matters

Without a mention the agent searches, and a search can land on last month's config or a stale copy. A mention removes that guess, which saves time and the occasional run built on the wrong file.

Mention a file

Type @ and start typing a name or part of a path: @lora finds configs/lora-8b.yaml. Pick a file with the arrow keys and Enter (or Tab), or click it. It goes into the message as its path, like @configs/lora-8b.yaml.

  • Any file in the workspace can be mentioned, pages included: @Experiments/held-out-push.md points at that page.
  • The list shows up to 12 matches. Type more of the name to narrow it.
  • Drag from the file tree. Dropping a workspace file onto the chat adds its mention for you.

The agent reads the file you mentioned, so there's no guessing between two files called config.yaml.

Mention a connected tool

Tools you've connected in Integrations appear under MCP servers, each with how many tools it offers. A bare @ shows the first two; type a name, or @mcp, to see more.

A tool goes in as @mcp: plus its id, like @mcp:arxiv. It tells the agent to use that connection for the request:

Try this

Search @mcp:arxiv for papers since 2025 on deduplicating fine-tuning data, and list the three most relevant with one line on what each found.

  • Only enabled connections are listed. Turn a tool on in Integrations to make it mentionable.
  • Agents can use connected tools without a mention. Mention one when you want that specific source, like Hugging Face over a general web search.

Mentions and agents

In the chat composer, @ points at files and tools. To work with a particular agent, click its name in the sidebar to chat with it directly, or ask Optimus to bring it in: “have Megatron try to disprove this.” In channels, @name mentions an agent, and it always replies; see Talk in a channel.

Mention well

  • Mention the file the answer depends on. “Why does @configs/lora-8b.yaml diverge?” starts the agent in the right place.
  • Mention the few that matter. Two or three files the answer depends on keep the agent focused.
  • Pair a mention with what to look for. “Check the learning-rate warm-up in @configs/lora-8b.yaml” is faster than the file alone.
  • Mention workspace files; attach outside ones. A mention points at the real file and follows your edits.