Class: LLM::LoopGuard

Inherits:
Object
  • Object
show all
Defined in:
lib/llm/loop_guard.rb

Overview

LLM::LoopGuard is the built-in implementation of llm.rb’s ‘guard` capability.

A guard is a context-level supervisor for agentic execution. It can inspect the current runtime state and return a warning string when pending tool work should be blocked before the loop keeps going.

LLM::LoopGuard detects when a context is repeating the same tool-call pattern instead of making progress. It is directly inspired by General Intelligence Systems’ Brute runtime and its doom-loop detection approach.

The public interface is intentionally small:

  • ‘call(ctx)` returns `nil` when no intervention is needed

  • ‘call(ctx)` returns a warning string when pending tool execution should be blocked

LLM::Context can use that warning to return in-band LLM::GuardError tool errors, and LLM::Agent enables this guard by default through its wrapped context.

Brute is MIT licensed. The relevant license grant is:

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so.

Constant Summary collapse

DEFAULT_THRESHOLD =

The default number of repeated tool-call patterns required before the guard intervenes.

Returns:

  • (Integer) 
3

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(config = {}) ⇒ LoopGuard

Returns a new instance of LoopGuard.

Parameters:

  • config (Hash) (defaults to: {})

Options Hash (config):

  • :threshold (Integer) —

    How many repeated tool-call patterns must appear at the tail of the sequence before the guard returns a warning.



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# File 'lib/llm/loop_guard.rb', line 50

def initialize(config = {})
  @threshold = config.fetch(:threshold, DEFAULT_THRESHOLD)
end

Instance Attribute Details

#threshold ⇒ Integer (readonly)

Returns the repetition threshold.

Returns:

  • (Integer) 


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# File 'lib/llm/loop_guard.rb', line 43

def threshold
  @threshold
end

Instance Method Details

#call(ctx) ⇒ String?

Checks the current context for repeated tool-call patterns.

This method inspects assistant tool calls only. It reduces each call to a ‘[tool_name, arguments]` signature and checks whether the tail of the sequence is repeating.

Parameters:

Returns:

  • (String, nil) —

    Returns a warning string when pending tool execution should be blocked, or ‘nil` when execution should continue.



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# File 'lib/llm/loop_guard.rb', line 65

def call(ctx)
  repetitions = detect(ctx.messages.to_a)
  repetitions ? warning(repetitions) : nil
end