Class: Brute::Middleware::ToolPipeline

Inherits:
Object
  • Object
show all
Defined in:
lib/brute/middleware/070_tool_pipeline.rb

Instance Method Summary collapse

Constructor Details

#initialize(app, tools: []) ⇒ ToolPipeline

Returns a new instance of ToolPipeline.



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# File 'lib/brute/middleware/070_tool_pipeline.rb', line 12

def initialize(app, tools: [])
  @app   = app
  @tools = tools
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/brute/middleware/070_tool_pipeline.rb', line 17

def call(env)
  env[:tools] = @tools
  @app.call(env)

  response = env[:messages].last

  if response.respond_to?(:tool_calls) && response.tool_calls.present?
    tools_to_run = response.tool_calls

    # tool_to_run may be an Array (Brute::ToolCall) or an id-keyed Hash (some libraries' native shape)
    if tools_to_run.respond_to?(:values)
      tools_to_run = tools_to_run.values
    end

    # No idea why we use Array() here... probably in case it's a hash or something...
    # because reject would work on the hash...
    tools_to_run = Array(tools_to_run).reject { |tc| tc.name == "question" }

    available_tools = Brute::Tools::Adapter.wrap_all(env[:tools])
    env[:events] << on_tool_call_start_event(tools_to_run)

    results = []

    # Async::Barrier blocks until all tasks are complete.
    # Tasks run in parrallel.
    #
    Sync do
      barrier = Async::Barrier.new

      tools_to_run.each do |tool_call|
        barrier.async do 
          name = tool_call.name.to_sym
          args = tool_call.arguments

          # Lifecycle hooks (Brute::Hooks): before_tool may rewrite
          # :arguments or short-circuit with a :result; approve_tool
          # denies on a false (or String) return; after_tool may
          # rewrite :result.
          call_env = {
            name:      name.to_s,
            arguments: args,
            result:    nil,
            events:    env[:events],
            metadata:  {},
            turn_env:  env,
          }
          if (hooks = env[:hooks])
            responses = hooks.emit(:before_tool, call_env).compact
            call_env[:result] = responses.last if call_env[:result].nil? && !responses.empty?

            if call_env[:result].nil?
              denial = hooks.emit(:approve_tool, call_env).find { |r| r == false || r.is_a?(String) }
              unless denial.nil?
                call_env[:result] = denial.is_a?(String) ? denial : %(Tool call to "#{name}" was denied.)
              end
            end
          end

          result = if call_env[:result].nil?
                     available_tools[name].call(call_env[:arguments])
                   else
                     call_env[:result]
                   end

          if (hooks = env[:hooks])
            call_env[:result] = result
            hooks.emit(:after_tool, call_env)
            result = call_env[:result]
          end

          # Coerce to String so Hash results (e.g. Shell's
          # {stdout:, stderr:, exit_code:}) serialize predictably.
          if result.is_a?(String)
            content = result
          else
            content = result.to_s
          end

          # Universal truncation safety net — skip if already truncated
          unless Brute::Truncation.already_truncated?(content)
            content = Brute::Truncation.truncate(content)
          end

          results << [tool_call, content]
        rescue => e
          # Capture the error as a tool result so the LLM can see it
          # and reason about the failure, rather than crashing the
          # entire middleware chain.
          env[:events] << { type: :error, data: { error: e, message: e.message } }
          results << [tool_call, "Error: #{e.class}: #{e.message}"]
        end
      end

      barrier.wait
    ensure
      barrier&.cancel
    end

    # Append events and messages in the original tool_call order so the
    # LLM sees a deterministic sequence regardless of completion order.
    results.sort_by! { |tool_call, _| tools_to_run.index(tool_call) }

    results.each do |tool_call, content|
      env[:events] << { type: :tool_result, data: { name: tool_call.name, content: content } }
      env[:messages] << Brute::Message.new(role: :tool, content: content, tool_call_id: tool_call.id)
    end
  end

  env
end