Dominik Kundel

Codex, Behind the Harness — Dominik Kundel, OpenAI

Aug 10, 2026 · 20:55

Dominik Kundel, an OpenAI engineer, explains the internals of the Codex agent harness, which is open source under Apache 2 and written in Rust. He details how context construction caps available skills at 2% of the context window and uses deferred tools with tool search to manage size and cost. For actions, Codex relies on an apply patch tool for file edits, a shell tool with ripgrep, and sandboxes: seatbelt on macOS, bubblewrap on Linux, and a custom open-source Windows sandbox. To reduce approval fatigue, an auto-review subagent with read-only permissions judges actions against user authorization and risk taxonomies. Speed improvements come from websocket mode in the responses API, which sends only changed items instead of full state, crucial when GPT 5.3 Codex Spark hit 1,000 tokens per second on Cerebras. Long-horizon goals work via a continuation prompt until the model calls an update goal tool, favoring concrete verifiable objectives, and auto compaction maintains performance…

Building voice agents with OpenAI — Dominik Kundel, OpenAI

Jun 29, 2025 · 1:25:35

Dominik Kundel from OpenAI presents the new OpenAI Agents SDK for TypeScript and demonstrates how to build voice agents, arguing that speech-to-speech architectures (using GPT-4 real-time) offer lower latency and more natural interactions than chained approaches that transcribe audio to text. He covers two architectures: chained (speech-to-text, text agent, text-to-speech) versus speech-to-speech (native audio understanding), and recommends starting with a small, clear goal, building evals and guardrails early, and using generative prompts to control tone and personality via openai.fm. In a live coding session, he builds a real-time agent with tools (e.g., getWeather) and handoffs, demonstrates delegation to a smarter model (O4 mini) for complex tasks like refunds, and shows built-in interruption handling, human-in-the-loop approval, tracing for debugging, and output guardrails. The SDK supports WebRTC and WebSocket, handles turn detection automatically, and provides session management with a 30-minute timeout that can be extended by injecting previous context.

Cooking with fire without burning down the kitchen: Dominik Kundel

Dec 31, 2024 · 20:35

Dominik Kundel, who leads product and design for Twilio's Emerging Tech & Innovation team, explains how the company balances disruptive AI innovation with its existing communications and customer data platform businesses. He distinguishes sustaining innovation (e.g., Apple's AI features) from disruptive innovation (e.g., agents not yet enterprise-ready due to quality and cost), arguing that ignoring disruptive AI is increasingly dangerous because quality improves daily. Kundel shares three key lessons from Twilio's AI journey: first, ship early and often—even rough prototypes—to gather real feedback, which led to the Twilio Alpha sub-brand for setting expectations; second, build a curious, problem-owning team rather than requiring existing AI expertise; third, share learnings internally and externally to avoid operating in a silo and to help customers be thought leaders. He recounts how an initial AI personalization engine was too disruptive for mainstream R&D, so the team iterated on an AI Assistance agent builder, using internal hackathons and dogfooding with low-risk use cases like IT helpdesk to improve quality before broader release.