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 low-level stateful execution boundary in llm.rb. Most users should start with Agent, which wraps Context and manages tool loops automatically. Use Context directly when you need manual control over tool execution.

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.deepseek(key: ENV["KEY"])
ctx = LLM::Context.new(llm, stream: $stdout)
ctx.talk "If a train goes 60 mph for 1.5 hours, how far does it travel?"
ctx.messages.each { |m| puts "[#{m.role}] #{m.content}" }

See Also:

Defined Under Namespace

Modules: Deserializer, Serializer

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Deserializer

#deserialize

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 :responses for OpenAI, otherwise it defaults to :completions.

  • :model (String) —

    Defaults to the provider's default model

  • :compactor (Class<LLM::Compactor>, nil) —

    A compactor class to use for context compaction. Defaults to LLM::Compactor::Null.

  • :compactor_options (Hash) —

    Options passed to the compactor's call method. Defaults to {}.

  • :transformer (Class<LLM::Transformer>, nil) —

    A transformer class to use for message transformation. Defaults to Transformer::Null.

  • :transformer_options (Hash) —

    Options passed to the transformer's call method. Defaults to {}.

  • :guard (Class<LLM::Guard>, nil) —

    A guard class to supervise agentic tool execution. Defaults to Guard::Null.

  • :guard_options (Hash) —

    Options passed to the guard's call method. Defaults to {}.

  • :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 95

def initialize(llm, params = {})
  params = {}.merge!(params)
  @llm = llm
  @mode = params.delete(:mode) || (llm.name == :openai ? :responses : :completions)
  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?
  @params[:store] ||= false if @mode == :responses
  @messages = LLM::Buffer.new(llm)
  extra = @params.slice(:model, :tools).merge!(ctx: self, tracer:)
  @params[:stream] = LLM::Stream.try(@params[:stream], extra:)
  @compactor = {
    klass: params.delete(:compactor) || LLM::Compactor::Null,
    options: params.delete(:compactor_options) || {}
  }
  @transformer = {
    klass: params.delete(:transformer) || LLM::Transformer::Null,
    options: params.delete(:transformer_options) || {}
  }
  @guard = {
    klass: params.delete(:guard) || LLM::Guard::Null,
    options: params.delete(:guard_options) || {}
  }
  @retry_budget = params.delete(:retry_budget) || 0
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 147

def compacted
  @compacted
end

#llm ⇒ LLM::Provider (readonly)

Returns a provider

Returns:



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# File 'lib/llm/context.rb', line 60

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 55

def messages
  @messages
end

#mode ⇒ Symbol (readonly)

Returns the context mode

Returns:

  • (Symbol) 


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

def mode
  @mode
end

Class Method Details

.params ⇒ Array<Symbol>

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 the set of runtime parameters that configure this context and must never be forwarded to a provider request body.

Returns:

  • (Array<Symbol>) 


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# File 'lib/llm/context.rb', line 48

def self.params
  %w[guard retry_budget concurrency transformer compactor]
end

Instance Method Details

#ask(prompt, options = {}) {|String| ... } ⇒ LLM::Response

Ask a question and return the content string directly. Accepts with: for file attachments and a block for streaming. This interface is compatible with RubyLLM's ask method.

Parameters:

  • prompt (String)
  • options (Hash) (defaults to: {})

Options Hash (options):

  • :with (String, Array<String>, nil) —

    File path(s) to attach

  • :stream (#<<, LLM::Stream, nil) —

    A stream target

Yields:

  • (String) —

    content chunks when streaming

Returns:



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# File 'lib/llm/context.rb', line 222

def ask(prompt, options = {}, &block)
  options = {with: nil, stream: nil}.merge!(options || {})
  with, stream = options.values_at(:with, :stream)
  prompt = with ? [prompt, [*with].map { local_file(_1) }] : prompt
  target = if block
    blk = block.dup
    blk.singleton_class.alias_method(:<<, :call)
    blk
  else
    stream
  end
  target ? talk(prompt, stream: target) : talk(prompt)
end

#compactor ⇒ LLM::Compactor

Returns a context compactor

Returns:



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# File 'lib/llm/context.rb', line 138

def compactor
  @compactor[:klass]
end

#context_usage ⇒ Rational?

Returns the fraction of the context window currently used. For example: Rational(100, 10_000), or nil when unknown

Returns:

  • (Rational, nil) —

    Returns the fraction of the context window currently used. For example: Rational(100, 10_000), or nil when unknown



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# File 'lib/llm/context.rb', line 371

def context_usage
  return nil if @messages.size < 2
  used = context_used
  return nil if used.nil?
  total = context_window
  total.nil? || total <= 0 ? nil : Rational(used, total)
rescue LLM::NoSuchModelError, LLM::NoSuchRegistryError
  nil
end

#context_used ⇒ Integer?

Returns the live context size (in tokens) of the most recent assistant message.

Returns:

  • (Integer, nil) —

    Returns the live context size (in tokens) of the most recent assistant message.



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# File 'lib/llm/context.rb', line 360

def context_used
  @messages
    .find(&:assistant?)
    &.token_usage
    &.total_tokens
end

#context_window ⇒ Integer?

Note:

This method returns nil when the context window size is not known to the runtime

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, nil) 


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# File 'lib/llm/context.rb', line 389

def context_window
  registry
    .limit(model:)
    .context
rescue LLM::NoSuchModelError, LLM::NoSuchRegistryError
  nil
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 512

def cost
  LLM::Cost.from(self)
end

#guard ⇒ Class<LLM::Guard>

Returns the configured guard class.

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 guard is stamped onto the functions the context binds, so it runs whenever a task is spawned — including tool calls queued from a stream via Stream#on_tool_call. A blocked call yields its in-band guard_error return without executing.

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

Returns:



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# File 'lib/llm/context.rb', line 167

def guard
  @guard[:klass]
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 423

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 238

def inspect
  "#<#{LLM::Utils.object_id(self)} " \
  "@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 334

def interrupt!
  llm.interrupt!(@owner)
  queue&.interrupt!
  pending_functions.each(&:interrupt!)
  @queue = nil
  @owner = nil
  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 433

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 472

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 131

def params
  @params.dup
end

#pending_functions ⇒ Array<LLM::Function>

Returns an array of functions that can be called

Returns:



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# File 'lib/llm/context.rb', line 247

def pending_functions
  return_ids = returns.map(&:id)
  guard = @guard[:klass].new(self)
  @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
        fn.guard  = guard
      end
    end.extend(LLM::Function::Array)
end

#pending_functions? ⇒ Boolean

Returns whether there is pending tool work in this context. This prefers queued streamed tool work when present, and otherwise falls back to unresolved functions derived from the message history.

Returns:

  • (Boolean) 


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

def pending_functions?
  pending = queue
  (pending && !pending.empty?) || pending_functions.any?
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 412

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

#registry ⇒ LLM::Registry

Returns:

See Also:



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# File 'lib/llm/context.rb', line 519

def registry
  llm.registry
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 443

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

#retry_budget ⇒ Integer

Returns the retry budget for rate-limited requests.

Returns:

  • (Integer) 


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# File 'lib/llm/context.rb', line 124

def retry_budget
  @retry_budget
end

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

Returns tool returns accumulated in this context

Returns:



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# File 'lib/llm/context.rb', line 285

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 503

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

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

Spawns a function through the context.

Parameters:

Returns:



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# File 'lib/llm/context.rb', line 278

def spawn(function, strategy)
  function.task(strategy)
end

#stream ⇒ LLM::Stream, ...

Returns a stream object, or nil

Returns:

  • (LLM::Stream, #<<, nil) —

    Returns a stream object, or nil



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# File 'lib/llm/context.rb', line 465

def stream
  @stream || @params[:stream]
end

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

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:



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# File 'lib/llm/context.rb', line 193

def talk(prompt, params = {})
  @owner = @llm.request_owner
  @compactor[:klass].new(self).call(**@compactor[:options])
  repair!(@messages, prompt)
  prompt, params, res = try { mode == :responses ? respond(prompt, params) : complete(prompt, params) }
  self.compacted = false
  if prompt.all?(&:tool_return?)
    @messages.concat prompt.map { LLM::Message.new(@llm.tool_role, _1.content, _1.extra) }
  else
    @messages.concat(prompt)
  end
  @messages.concat([res.choices[-1]].compact)
  res
ensure
  @owner = nil
end

#to_h ⇒ Hash

Returns:

  • (Hash) 


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# File 'lib/llm/context.rb', line 478

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 489

def to_json(...)
  LLM.json.dump(to_h, ...)
end

#token_usage ⇒ LLM::Usage Also known as: usage

Returns token usage accumulated in this context

Returns:



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

def token_usage
  @messages
    .select(&:assistant?)
    .map(&:token_usage)
    .compact
    .reduce(LLM::Usage.zero, :+)
end

#tracer ⇒ LLM::Tracer

Returns an LLM tracer

Returns:



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# File 'lib/llm/context.rb', line 450

def tracer
  @llm.tracer
end

#tracer=(other) ⇒ void

This method returns an undefined value.

Parameters:



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# File 'lib/llm/context.rb', line 458

def tracer=(other)
  @llm.tracer = other || LLM::Tracer::Null.new(@llm)
end

#transformer ⇒ Class<LLM::Transformer>

Returns the configured transformer class.

Transformers rewrite the most recent message before it is sent to the provider.

Returns:



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# File 'lib/llm/context.rb', line 178

def transformer
  @transformer[:klass]
end

#wait(strategy, except: []) ⇒ 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>) —

    If the stream queue already has tool work, wait will drain it without using this argument. Otherwise, this controls how pending functions are resolved directly. Use :sequential for sequential execution without spawning.

  • except (Array<LLM::Function>) (defaults to: []) —

    A list of functions to exclude from the wait

Returns:



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# File 'lib/llm/context.rb', line 310

def wait(strategy, except: [])
  if stream.queue.empty?
    ##
    # Every pending function is spawned as a task that checks its own
    # guard (stamped on the function) before running. Blocked tasks
    # yield their guard's return, so all pending calls still close.
    tools = except.empty? ? pending_functions : pending_functions - except
    @queue = tools.task(strategy)
    returns = @queue.wait
    emit_tool_returns(tools, returns)
    returns
  else
    @queue = stream.queue
    @queue.wait
  end
ensure
  @queue = nil
  @stream = nil
end