Class: LittleGhost::Workflow

Inherits:
Assembly show all
Defined in:
lib/little_ghost/workflow.rb

Overview

Coordinates Assembly participants with ordinary Ruby control flow.

A workflow is an Assembly whose perform method controls ordering, branching, parallel work, and local variables. Each participant may be an Agent or another coordinated Assembly. The workflow can stream one final participant response or return a value computed from intermediate answers.

A support workflow can guarantee that research happens before the responder writes the caller-visible answer:

class ResponseWorkflow < LittleGhost::Workflow
private

def perform
  evidence = invoke(ResearchAgent).output
  invoke CustomerSupportAgent, input: <<~PROMPT
    #{input.text}

    Research:
    #{evidence}
  PROMPT
end
end

run = ResponseWorkflow.ask("Why is transfer 481 pending?")
run.response
# One possible response: Transfer 481 is waiting for the receiving bank.

Call a named Workflow with ask for its final Run, or the streaming entrypoint for live events.

invoke returns a lazy Workflow::Invocation. Reading output consumes an intermediate invocation and returns RunResult#output. Return a final invocation without consuming it when its events should reach the caller. Return a String or JSON-compatible value when Ruby computes the final answer. Intermediate usage is added to either result.

A child receives the Workflow input unless invoke supplies another one. It also inherits history, settings, cancellation, deadline, template paths, and the parent tracing relationship. JSON-like context is copied for each child, preventing one intermediate Agent from mutating a sibling's state. Non-JSON-like workflow context raises ArgumentError.

A Workflow instance streams once. Returning nil, an unsupported value, an already consumed invocation, or consuming one twice raises ProtocolError. A composition error fails the owning top-level Run. Each child Assembly closes after its attempt, and a cleanup failure raises from that attempt.

Defined Under Namespace

Classes: Invocation

Constant Summary collapse

MAX_DIRECT_RESULT_BYTES =

:nodoc:

1_000_000
MAX_DIRECT_RESULT_DEPTH =

:nodoc:

64
MAX_DIRECT_RESULT_NODES =

:nodoc:

100_000

Constants inherited from Assembly

Assembly::MAX_STEP_EVENTS, Assembly::MAX_STEP_EVENT_BYTES, Assembly::MAX_STEP_OUTPUT_BYTES

Instance Attribute Summary collapse

Attributes inherited from Assembly

#agent_stream_path, #sandbox, #workspace

Instance Method Summary collapse

Methods inherited from Assembly

#as_tool, #as_tool_with_factory, ask, #ask, assembly_id, assembly_kind, #bind_agent_stream_path, #bind_assembly_definition, #build_run, #call, definition, description, #entrypoint_name, #interject, #start_execution, stream_ask, #stream_ask, to_builder, validate_step_policy!

Methods included from Support::ClassAttributes

#class_attribute, included

Constructor Details

#initialize(run: nil, runtime: nil) ⇒ Workflow

:nodoc:



141
142
143
144
145
146
147
 
# File 'lib/little_ghost/workflow.rb', line 141

def initialize(run: nil, runtime: nil) # :nodoc:
  super(run:, runtime:, standalone: run.nil?)
  @mutex = Mutex.new
  @closed = false
  @started = false
  @invocations = []
end

Instance Attribute Details

#run ⇒ Object (readonly)

Run that owns this run-scoped Workflow.



137
138
139
 
# File 'lib/little_ghost/workflow.rb', line 137

def run
  @run
end

#runtime ⇒ Object (readonly)

Runtime used to resolve child Assemblies.



139
140
141
 
# File 'lib/little_ghost/workflow.rb', line 139

def runtime
  @runtime
end

Instance Method Details

#close ⇒ Object

Closes all declared invocations in reverse order.

The operation is idempotent, attempts every close, and raises the first cleanup failure.



252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
 
# File 'lib/little_ghost/workflow.rb', line 252

def close
  invocations = @mutex.synchronize do
    return if @closed

    @closed = true
    @invocations.reverse
  end
  errors = []
  invocations.each do |invocation|
    invocation.close
  rescue => error
    errors << error
  end
  raise errors.first if errors.any?
end

#prompt_locals ⇒ Object

Additional prompt locals shared by agents invoked from the workflow. Subclasses may override this hook.



151
 
# File 'lib/little_ghost/workflow.rb', line 151

def prompt_locals = {}

#stream(input = nil, history: nil, context: nil, cancellation_token: Support::CancellationToken.new, deadline: nil, settings: nil, template_locals: nil, template_paths: nil, parent_operation_id: nil, checkpoint: nil) ⇒ Object

Streams the workflow once as StreamEvent objects.

perform may return a final, unconsumed Workflow::Invocation, a String, or a JSON-compatible value. The returned Enumerator is lazy, but calling stream reserves the single-use workflow instance even when enumeration has not started yet.

Raises:

  • (ArgumentError) 


159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
 
# File 'lib/little_ghost/workflow.rb', line 159

def stream(
  input = nil,
  history: nil,
  context: nil,
  cancellation_token: Support::CancellationToken.new,
  deadline: nil,
  settings: nil,
  template_locals: nil,
  template_paths: nil,
  parent_operation_id: nil,
  checkpoint: nil
)
  raise ArgumentError, "input is required" if input.nil?

  if standalone?
    return build_run(entrypoint_payload(input, {
      history:,
      context:,
      settings:,
      template_paths:,
      deadline_at: deadline,
      cancellation_token:
    }.compact)).each
  end

  @mutex.synchronize do
    raise Error, "workflow is already closed" if @closed
    raise Error, "workflow instances can only be streamed once" if @started

    @started = true
    @input = input.is_a?(Message) ? input : Message.new(role: :user, content: input)
    @history = normalize_history(history)
    @context = context || {}
    @cancellation_token = cancellation_token
    @deadline = deadline
    @settings = settings || {}
    @template_locals = template_locals || {}
    @template_paths = template_paths || []
    @parent_operation_id = parent_operation_id
    @checkpoint = checkpoint
    @intermediate_usage = Usage.new
    @workflow_steps = []
    @workflow_events = nil
  end

  Enumerator.new do |events|
    error_emitted = false
    observed_usage = nil
    @workflow_events = events
    ensure_open!
    final_value = perform
    if final_value.is_a?(Invocation)
      if final_value.consumed?
        raise ProtocolError, "#{self.class} returned an already consumed invocation from perform"
      end

      final_value.each(checkpoint: @checkpoint) do |event|
        error_emitted = true if event.type == :invocation_error
        event = aggregate_usage(event)
        observed_usage = case event.type
        when :invocation_stop
          event.data.fetch(:result).usage
        when :invocation_error
          event.data[:usage] || observed_usage
        when :assembly_step_error
          event.data[:usage] || observed_usage
        else
          observed_usage
        end
        events << event
      end
    else
      emit_direct_result(final_value, events)
    end
  rescue => error
    unless error_emitted
      events << StreamEvent.build(
        :invocation_error,
        error:,
        usage: observed_usage || workflow_usage,
        metadata: {}
      )
    end
    raise
  ensure
    @workflow_events = nil
  end
end