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+#!/usr/bin/env ruby
+# GPT-5 Action-Oriented Agent - pure stdlib
+
+require "net/http"
+require "json"
+require "uri"
+
+API_KEY = ENV["OPENAI_API_KEY"] or abort("Set OPENAI_API_KEY")
+MODEL   = "gpt-5-mini"
+
+# Tools GPT-5 can use
+TOOLS = [
+  {
+    type: "function",
+    function: {
+      name: "read_file",
+      description: "Read contents of a file",
+      parameters: {
+        type: "object",
+        properties: { path: { type: "string" } },
+        required: ["path"]
+      }
+    }
+  },
+  {
+    type: "function",
+    function: {
+      name: "write_file",
+      description: "Write contents to a file",
+      parameters: {
+        type: "object",
+        properties: { path: { type: "string" }, content: { type: "string" } },
+        required: ["path","content"]
+      }
+    }
+  },
+  {
+    type: "function",
+    function: {
+      name: "run_command",
+      description: "Run a shell command and return output",
+      parameters: {
+        type: "object",
+        properties: { command: { type: "string" } },
+        required: ["command"]
+      }
+    }
+  }
+]
+
+# Execute tools
+def run_tool(name, args)
+  case name
+  when "read_file"
+    begin
+      { content: File.read(args["path"]) }
+    rescue => e
+      { error: e.message }
+    end
+  when "write_file"
+    begin
+      File.write(args["path"], args["content"])
+      { status: "ok" }
+    rescue => e
+      { error: e.message }
+    end
+  when "run_command"
+    begin
+      { output: `#{args["command"]}`.strip }
+    rescue => e
+      { error: e.message }
+    end
+  else
+    { error: "unknown tool #{name}" }
+  end
+end
+
+# Call OpenAI
+def openai_chat(messages, tools)
+  uri = URI("https://api.openai.com/v1/chat/completions")
+  req = Net::HTTP::Post.new(uri)
+  req["Authorization"] = "Bearer #{API_KEY}"
+  req["Content-Type"] = "application/json"
+
+  req.body = {
+    model: MODEL,
+    messages: messages,
+    tools: tools,
+    tool_choice: "auto"
+  }.to_json
+
+  res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |h| h.request(req) }
+  raise "HTTP #{res.code}: #{res.body}" unless res.is_a?(Net::HTTPSuccess)
+  JSON.parse(res.body)
+end
+
+# Conversation with bias-for-action
+messages = [
+  { role: "system", content: <<~MSG
+      You are a reasoning coding and system agent. Prioritize taking practical actions whenever possible.
+      Use read_file, write_file, and run_command proactively to achieve user goals.
+      Explain your reasoning briefly in content. Avoid unnecessary delays; act whenever sufficient info is available.
+  MSG
+  }
+]
+
+puts ">> Type instructions (or 'exit')"
+
+loop do
+  print "\nUser> "
+  input = STDIN.gets&.strip
+  break if input.nil? || input.downcase == "exit"
+  messages << { role: "user", content: input }
+
+  loop do
+    resp = openai_chat(messages, TOOLS)
+    msg = resp.dig("choices", 0, "message")
+    messages << msg
+
+    # Print reasoning content immediately
+    if msg["content"] && !msg["content"].empty?
+      puts "\nAssistant> #{msg['content']}"
+    end
+
+    # Execute any tool calls
+    if msg["tool_calls"]
+      msg["tool_calls"].each do |call|
+        name = call.dig("function","name")
+        args = JSON.parse(call.dig("function","arguments"))
+        result = run_tool(name, args)
+        messages << { role: "tool", tool_call_id: call["id"], content: JSON.dump(result) }
+      end
+      next # continue reasoning on tool results
+    end
+
+    break # no tool calls left, turn is done
+  end
+end