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Not every decision should be made by an LLM. Fabro provides several mechanisms for humans to participate in workflows — approving plans, choosing between options, providing free-form input, and steering agents while they run.

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Human gates

A human gate is a node with shape hexagon that pauses the workflow and presents the user with a choice. The options are derived from the outgoing edge labels:
When execution reaches the gate, the user sees the previous stage’s output followed by the node’s label (“Approve Plan”) and the available options. In the CLI, this appears as an interactive menu. In the web UI, blocked runs show an interview dock on the run page where the user can answer the pending question.

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Keyboard accelerators

The prefixes [A], [R], [S] in edge labels serve as keyboard accelerators. Fabro supports three formats: When matching the user’s selection to an edge, Fabro strips the accelerator prefix so typing A matches [A] Approve.

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Freeform input

In addition to fixed choices, a human gate can accept freeform text input. Add an edge with freeform=true:
If the user types something that doesn’t match any fixed option, their input routes to the freeform edge. The text is available to downstream nodes as human.gate.text in the run context. When a gate has only a freeform edge and no fixed choices, the user goes directly to a text input prompt — skipping the multiple-choice menu entirely. This is useful for conversational loops like REPL workflows where the user provides open-ended instructions each iteration.

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Question types

Human gates infer their interview type from their edges: fixed choices become multiple_choice, and a gate with only a freeform edge becomes freeform. To force another interviewer presentation, set question_type on the node:
Supported values are yes_no, confirmation, multiple_choice, multi_select, and freeform.

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Default choice on timeout

If a human gate has a timeout configured, you can specify a default choice using the human.default_choice attribute:
If the timeout elapses without a response, the workflow continues to the default target rather than failing.

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Unanswered gates fail closed

Fabro does not treat missing input as approval. A human gate advances only when one of these happens:
  • A person explicitly answers the question
  • The gate times out and human.default_choice is set
  • The run uses --auto-approve
If stdin is closed, a prompt is canceled, a web session disconnects, or no answer is otherwise captured, the gate is treated as unanswered. Fabro will not fall through to an unconditional approval edge. If you want to handle that case explicitly, add a failure route such as condition="outcome=failed" or a retry_target.

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Auto-approve

For testing or fully automated runs, pass --auto-approve to skip all human gates:
Auto-approve selects Yes for yes/no gates and the first option for multiple-choice gates.

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Where to place human gates

Human gates are most valuable at high-leverage decision points:
  • Before implementation — Approve a plan before the agent writes code
  • After review — Confirm that a code review’s findings are worth fixing
  • At branch points — Choose a strategy when multiple approaches are viable
  • Before external actions — Approve before deploying, merging, or sending notifications
A workflow can have multiple human gates. Place them where the cost of a wrong decision is high relative to the cost of a brief pause.

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Context set by human gates

When a user makes a selection, the human gate sets several context values for downstream use: These can be read in edge conditions or referenced by downstream agents.