Class: LLM::Context

Inherits:
Object
  • Object
show all
Includes:
Deserializer, Serializer
Defined in:
lib/llm/context.rb,
lib/llm/context/serializer.rb,
lib/llm/context/deserializer.rb

Overview

LLM::Context is the stateful execution boundary in llm.rb.

It holds the evolving runtime state for an LLM workflow: conversation history, tool calls and returns, schema and streaming configuration, accumulated usage, and request ownership for interruption.

This is broader than prompt context alone. A context is the object that lets one-off prompts, streaming turns, tool execution, persistence, retries, and serialized long-lived workflows all run through the same model.

A context can drive the chat completions API that all providers support or the Responses API on providers that expose it.

Examples:

#!/usr/bin/env ruby
require "llm"

llm = LLM.openai(key: ENV["KEY"])
ctx = LLM::Context.new(llm)

prompt = LLM::Prompt.new(llm) do
  system "Be concise and show your reasoning briefly."
  user "If a train goes 60 mph for 1.5 hours, how far does it travel?"
  user "Now double the speed for the same time."
end

ctx.talk(prompt)
ctx.messages.each { |m| puts "[#{m.role}] #{m.content}" }

Defined Under Namespace

Modules: Deserializer, Serializer

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Deserializer

#deserialize, #deserialize_message

Constructor Details

#initialize(llm, params = {}) ⇒ Context

Returns a new instance of Context.

Parameters:

  • llm (LLM::Provider) —

    A provider

  • params (Hash) (defaults to: {}) —

    The parameters to maintain throughout the conversation. Any parameter the provider supports can be included and not only those listed here.

Options Hash (params):

  • :mode (Symbol) —

    Defaults to :completions

  • :model (String) —

    Defaults to the provider’s default model

  • :tools (Array<LLM::Function>, nil) —

    Defaults to nil

  • :skills (Array<String>, nil) —

    Defaults to nil



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# File 'lib/llm/context.rb', line 84

def initialize(llm, params = {})
  @llm = llm
  @mode = params.delete(:mode) || :completions
  @compactor = params.delete(:compactor)
  @guard = params.delete(:guard)
  @transformer = params.delete(:transformer)
  tools = [*params.delete(:tools), *load_skills(params.delete(:skills))]
  @params = {model: llm.default_model, schema: nil}.compact.merge!(params)
  @params[:tools] = tools unless tools.empty?
  @messages = LLM::Buffer.new(llm)
end

Instance Attribute Details

#compacted ⇒ Boolean Also known as: compacted?

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns whether the context has been compacted and no later model response has cleared that state.

Returns:

  • (Boolean) 


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# File 'lib/llm/context.rb', line 119

def compacted
  @compacted
end

#llm ⇒ LLM::Provider (readonly)

Returns a provider

Returns:



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# File 'lib/llm/context.rb', line 59

def llm
  @llm
end

#messages ⇒ LLM::Buffer<LLM::Message> (readonly)

Returns the accumulated message history for this context

Returns:



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# File 'lib/llm/context.rb', line 54

def messages
  @messages
end

#mode ⇒ Symbol (readonly)

Returns the context mode

Returns:

  • (Symbol) 


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# File 'lib/llm/context.rb', line 64

def mode
  @mode
end

Instance Method Details

#call(target) ⇒ Array<LLM::Function::Return>

Calls a named collection of work through the context.

This currently supports ‘:functions`, forwarding to `functions.call`.

Parameters:

  • target (Symbol) —

    The work collection to call

Returns:



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# File 'lib/llm/context.rb', line 267

def call(target)
  case target
  when :functions then guarded_returns || functions.call
  else raise ArgumentError, "Unknown target: #{target.inspect}. Expected :functions"
  end
end

#compactor ⇒ LLM::Compactor

Returns a context compactor This feature is inspired by the compaction approach developed by General Intelligence Systems.

Returns:



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# File 'lib/llm/context.rb', line 101

def compactor
  @compactor = LLM::Compactor.new(self, @compactor || {}) unless LLM::Compactor === @compactor
  @compactor
end

#compactor=(compactor) ⇒ LLM::Compactor, ...

Sets a context compactor or compactor config

Parameters:

Returns:



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# File 'lib/llm/context.rb', line 110

def compactor=(compactor)
  @compactor = compactor
end

#context_window ⇒ Integer

Note:

This method returns 0 when the provider or model can’t be found within Registry.

Returns the model’s context window. The context window is the maximum amount of input and output tokens a model can consider in a single request.

Returns:

  • (Integer) 


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# File 'lib/llm/context.rb', line 477

def context_window
  LLM
    .registry_for(llm)
    .limit(model:)
    .context
rescue LLM::NoSuchModelError, LLM::NoSuchRegistryError
  0
end

#cost ⇒ LLM::Cost

Returns an approximate cost for a given context based on both the provider, and model

Returns:

  • (LLM::Cost) —

    Returns an approximate cost for a given context based on both the provider, and model



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# File 'lib/llm/context.rb', line 460

def cost
  cost = LLM.registry_for(llm).cost(model:)
  input_cost = (cost.input.to_f / 1_000_000.0) * usage.input_tokens
  output_cost = (cost.output.to_f / 1_000_000.0) * usage.output_tokens
  LLM::Cost.new(input_cost, output_cost)
rescue LLM::NoSuchModelError, LLM::NoSuchRegistryError
  LLM::Cost.new(0, 0)
end

#functions ⇒ Array<LLM::Function>

Returns an array of functions that can be called

Returns:



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# File 'lib/llm/context.rb', line 246

def functions
  return_ids = returns.map(&:id)
  @messages
    .select(&:assistant?)
    .flat_map do |msg|
      fns = msg.functions.select { _1.pending? && !return_ids.include?(_1.id) }
      fns.each do |fn|
        fn.tracer = tracer
        fn.model  = msg.model
      end
    end.extend(LLM::Function::Array)
end

#guard ⇒ #call?

Returns a guard, if configured.

Guards are context-level supervisors for agentic execution. A guard can inspect the runtime state and decide whether pending tool work should be blocked before the context keeps looping.

The built-in implementation is LLM::LoopGuard, which detects repeated tool-call patterns and turns them into in-band LLM::GuardError tool returns.

Returns:



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# File 'lib/llm/context.rb', line 134

def guard
  return if @guard.nil? || @guard == false
  @guard = LLM::LoopGuard.new if @guard == true
  @guard = LLM::LoopGuard.new(@guard) if Hash === @guard
  @guard
end

#guard=(guard) ⇒ #call, ...

Sets a guard or guard config.

Guards must implement ‘call(ctx)` and return either `nil` or a warning string. Returning a warning tells the context to block pending tool work with guarded tool errors instead of continuing the loop.

Parameters:

  • guard (#call, Hash, Boolean, nil)

Returns:

  • (#call, Hash, Boolean, nil) 


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# File 'lib/llm/context.rb', line 150

def guard=(guard)
  @guard = guard
end

#image_url(url) ⇒ LLM::Object

Recongize an object as a URL to an image

Parameters:

  • url (String) —

    The URL

Returns:



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# File 'lib/llm/context.rb', line 386

def image_url(url)
  LLM::Object.from(value: url, kind: :image_url)
end

#inspect ⇒ String

Returns:

  • (String) 


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# File 'lib/llm/context.rb', line 237

def inspect
  "#<#{self.class.name}:0x#{object_id.to_s(16)} " \
  "@llm=#{@llm.class}, @mode=#{@mode.inspect}, @params=#{@params.inspect}, " \
  "@messages=#{@messages.inspect}>"
end

#interrupt! ⇒ nil Also known as: cancel!

Interrupt the active request, if any. This is inspired by Go’s context cancellation model.

Returns:

  • (nil) 


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# File 'lib/llm/context.rb', line 332

def interrupt!
  pending = functions.to_a
  llm.interrupt!(@owner)
  queue&.interrupt!
  return if pending.empty?
  pending.each(&:interrupt!)
  returns = pending.map { _1.cancel(reason: "function call cancelled") }
  @messages << LLM::Message.new(@llm.tool_role, returns)
  nil
end

#local_file(path) ⇒ LLM::Object

Recongize an object as a local file

Parameters:

  • path (String) —

    The path

Returns:



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# File 'lib/llm/context.rb', line 396

def local_file(path)
  LLM::Object.from(value: LLM.File(path), kind: :local_file)
end

#model ⇒ String

Returns the model a Context is actively using

Returns:

  • (String) 


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# File 'lib/llm/context.rb', line 420

def model
  messages.find(&:assistant?)&.model || @params[:model]
end

#params ⇒ Hash

Returns the default params for this context

Returns:

  • (Hash) 


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# File 'lib/llm/context.rb', line 69

def params
  @params.dup
end

#prompt(&b) ⇒ LLM::Prompt Also known as: build_prompt

Build a role-aware prompt for a single request.

Prefer this method over #build_prompt. The older method name is kept for backward compatibility.

Examples:

prompt = ctx.prompt do
  system "Your task is to assist the user"
  user "Hello, can you assist me?"
end
ctx.talk(prompt)

Parameters:

  • b (Proc) —

    A block that composes messages. If it takes one argument, it receives the prompt object. Otherwise it runs in prompt context.

Returns:



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# File 'lib/llm/context.rb', line 375

def prompt(&b)
  LLM::Prompt.new(@llm, &b)
end

#remote_file(res) ⇒ LLM::Object

Reconginize an object as a remote file

Parameters:

Returns:



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# File 'lib/llm/context.rb', line 406

def remote_file(res)
  LLM::Object.from(value: res, kind: :remote_file)
end

#respond(prompt, params = {}) ⇒ LLM::Response

Note:

Not all LLM providers support this API

Interact with the context via the responses API. This method immediately sends a request to the LLM and returns the response.

Examples:

llm = LLM.openai(key: ENV["KEY"])
ctx = LLM::Context.new(llm)
res = ctx.respond("What is the capital of France?")
puts res.output_text

Parameters:

  • params (defaults to: {}) —

    The params, including optional :role (defaults to :user), :stream, :tools, :schema etc.

  • prompt (String) —

    The input prompt to be completed

Returns:

  • (LLM::Response) —

    Returns the LLM’s response for this turn.



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# File 'lib/llm/context.rb', line 219

def respond(prompt, params = {})
  @owner = @llm.request_owner
  compactor.compact!(prompt) if compactor.compact?(prompt)
  params = @params.merge(params)
  prompt, params = transform(prompt, params)
  bind!(params[:stream], params[:model], params[:tools])
  res_id = params[:store] == false ? nil : @messages.find(&:assistant?)&.response&.response_id
  params = params.merge(previous_response_id: res_id, input: @messages.to_a).compact
  res = @llm.responses.create(prompt, params)
  self.compacted = false
  role = params[:role] || @llm.user_role
  @messages.concat LLM::Prompt === prompt ? prompt.to_a : [LLM::Message.new(role, prompt)]
  @messages.concat [res.choices[-1]]
  res
end

#returns ⇒ Array<LLM::Function::Return>

Returns tool returns accumulated in this context

Returns:



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# File 'lib/llm/context.rb', line 292

def returns
  @messages
    .select(&:tool_return?)
    .flat_map do |msg|
      LLM::Function::Return === msg.content ?
        [msg.content] :
        [*msg.content].grep(LLM::Function::Return)
    end
end

#serialize(path:) ⇒ void Also known as: save

This method returns an undefined value.

Save the current context state

Examples:

llm = LLM.openai(key: ENV["KEY"])
ctx = LLM::Context.new(llm)
ctx.talk "Hello"
ctx.save(path: "context.json")

Raises:

  • (SystemCallError) —

    Might raise a number of SystemCallError subclasses



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# File 'lib/llm/context.rb', line 451

def serialize(path:)
  ::File.binwrite path, LLM.json.dump(to_h)
end

#spawn(function, strategy) ⇒ LLM::Function::Return, LLM::Function::Task

Spawns a function through the context.

When a guard is configured, this method can return an in-band guarded tool error instead of spawning work.

Parameters:

Returns:



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# File 'lib/llm/context.rb', line 283

def spawn(function, strategy)
  warning = guard&.call(self)
  return guarded_return_for(function, warning) if warning
  function.spawn(strategy)
end

#talk(prompt, params = {}) ⇒ LLM::Response Also known as: chat

Interact with the context via the chat completions API. This method immediately sends a request to the LLM and returns the response.

Examples:

llm = LLM.openai(key: ENV["KEY"])
ctx = LLM::Context.new(llm)
res = ctx.talk("Hello, what is your name?")
puts res.messages[0].content

Parameters:

  • params (defaults to: {}) —

    The params, including optional :role (defaults to :user), :stream, :tools, :schema etc.

  • prompt (String) —

    The input prompt to be completed

Returns:

  • (LLM::Response) —

    Returns the LLM’s response for this turn.



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# File 'lib/llm/context.rb', line 188

def talk(prompt, params = {})
  return respond(prompt, params) if mode == :responses
  @owner = @llm.request_owner
  compactor.compact!(prompt) if compactor.compact?(prompt)
  params = params.merge(messages: @messages.to_a)
  params = @params.merge(params)
  prompt, params = transform(prompt, params)
  bind!(params[:stream], params[:model], params[:tools])
  res = @llm.complete(prompt, params)
  self.compacted = false
  role = params[:role] || @llm.user_role
  role = @llm.tool_role if params[:role].nil? && [*prompt].grep(LLM::Function::Return).any?
  @messages.concat LLM::Prompt === prompt ? prompt.to_a : [LLM::Message.new(role, prompt)]
  @messages.concat [res.choices[-1]]
  res
end

#to_h ⇒ Hash

Returns:

  • (Hash) 


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# File 'lib/llm/context.rb', line 426

def to_h
  {
    schema_version: 1,
    model:,
    compacted:,
    messages: @messages.map { serialize_message(_1) }
  }
end

#to_json ⇒ String

Returns:

  • (String) 


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# File 'lib/llm/context.rb', line 437

def to_json(...)
  to_h.to_json(...)
end

#tracer ⇒ LLM::Tracer

Returns an LLM tracer

Returns:



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# File 'lib/llm/context.rb', line 413

def tracer
  @llm.tracer
end

#transformer ⇒ #call?

Returns a transformer, if configured.

Transformers can rewrite outgoing prompts and params before a request is sent to the provider.

Returns:



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# File 'lib/llm/context.rb', line 161

def transformer
  @transformer
end

#transformer=(transformer) ⇒ #call?

Sets a transformer.

Transformers must implement ‘call(ctx, prompt, params)` and return a two-element array of `[prompt, params]`.

Parameters:

  • transformer (#call, nil)

Returns:



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# File 'lib/llm/context.rb', line 173

def transformer=(transformer)
  @transformer = transformer
end

#usage ⇒ LLM::Object

Returns token usage accumulated in this context

Returns:



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# File 'lib/llm/context.rb', line 347

def usage
  if usage = @messages.find(&:assistant?)&.usage
    LLM::Object.from(
      input_tokens: usage.input_tokens || 0,
      output_tokens: usage.output_tokens || 0,
      reasoning_tokens: usage.reasoning_tokens || 0,
      total_tokens: usage.total_tokens || 0
    )
  else
    ZERO_USAGE
  end
end

#wait(strategy) ⇒ Array<LLM::Function::Return>

Waits for queued tool work to finish.

This prefers queued streamed tool work when the configured stream exposes a non-empty queue. Otherwise it falls back to waiting on the context’s pending functions directly.

Parameters:

  • strategy (Symbol, Array<Symbol>) —

    The concurrency strategy to use, or the possible concurrency strategies to wait on. For example, ‘[:thread, :ractor]` waits for any queued thread or ractor work, in that order.

Returns:



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# File 'lib/llm/context.rb', line 314

def wait(strategy)
  if LLM::Stream === stream && !stream.queue.empty?
    @queue = stream.queue
    @queue.wait(strategy)
  else
    return guarded_returns if guarded_returns
    @queue = functions.spawn(strategy)
    @queue.wait
  end
ensure
  @queue = nil
  @stream = nil
end