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 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.

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 41

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 34

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 56

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