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DeerFlow

Quick Start

This chapter is for people using DeerFlow through the web interface. By the end you will know how to let the Lead Agent use subagents, how to read a task card, and where the result goes.

Prerequisites

  • DeerFlow is configured per Quick Start and you can chat normally. The subagents: section in config.yaml can stay empty; the built-in defaults work.
  • To use the bash subagent you need a container sandbox, or sandbox.allow_host_bash: true under the local sandbox, which is only appropriate in a fully trusted local environment. Otherwise bash is hidden from the catalog.

Turn subagents on

Pick Ultra in the mode selector of the input box. The UI describes it as “Pro mode with subagents to divide work”. Ultra mode sets subagent_enabled to true in the request context, enables plan mode, and defaults the reasoning effort to high. In Flash, Thinking, and Pro modes the Lead Agent does not see the task tool.

If you are talking to a Custom Agent, the Subagent access option in that agent’s settings may narrow or disable delegation further. See Subagent Catalog.

Send a task that splits well

More delegation is not better. The Lead Agent defaults to direct execution and only delegates when parallelism, specialist capability, or context isolation gives a clear net benefit. A good candidate:

Research the pricing changes at companies A, B, and C over the last year, write one paragraph of conclusions for each, then combine them into a comparison table.

The three investigations are independent, can run in parallel, and their browsing history does not need to pollute the main conversation.

Read the task card

Every task call shows up in the conversation as a subtask card:

  • Status icon: a spinner while running, a check mark when completed, a red cross when failed. Cancelled, timed-out, and polling-timed-out runs all show as failed.
  • Model label and token total: the model the subagent actually used and its cumulative tokens. The token count updates after each completed subagent model call and is hidden when token_usage.enabled is false.
  • Step timeline: expand the card to see each step, with assistant reasoning interleaved with tool calls. After a page reload the steps are backfilled from run events, so nothing is lost.
  • Result: the card renders the final report when completed, or a red error line when failed.

How the result reaches the Lead Agent

The subagent’s final report returns as a tool result starting with Task Succeeded. Result:. If acceptance criteria were attached, an Acceptance checklist section follows. The Lead Agent continues from there and synthesizes the final reply.

The report is the subagent’s self-report. The runtime cross-checks the receipts it cites and marks unverified parts in the delegation ledger, and the Lead Agent uses that to decide whether to double-check. See Results and Acceptance.

Stopping

Pressing stop while a subagent is running sends it a cancellation request. The card turns to the failed state because no tool result arrives, and the ledger entry is marked cancelled when the next run starts, so the Lead Agent is no longer told that the task is “already delegated, do not repeat”.

A subagent cannot ask you questions: ask_clarification is not available to it. Put the constraints, paths, and expected deliverable into your request to the Lead Agent, which passes them on.

Next steps

Introduction