Show HN: Agent Runner – open-source agent harness to benchmark real coding

Hey HN! We built Agent Runner, a model-agnostic, open-source agent harness that executes the same prompt against two anonymized coding agents in parallel sandboxes. Each agent can make tool calls, edit multiple files, and self-correct through iterative reasoning. You pick the better result - this becomes the ground truth for the leaderboard.

Why we built it Traditional benchmarks often fall short for modern agentic systems: they rely on static tasks and only measure final outputs. But real coding agents modify multiple files across a repo, answer to user re-prompts, use tool calls, and recover from partial failures

What Agent Runner does You ask it to build anything Agent Runner kicks off two generations from different sandboxed LLM providers (OpenAI, Anthropic, Google, xAI, Mistral, Kimi, and more) Anonymized models make tool calls, multi-file edits, and cater to reprompts You pick your favorite - this preference powers the benchmark

Because different providers handle tool calls, prompts, and execution semantics differently, we worked with each provider to ensure configurations reflect intended behavior. These provider-specific setups remain private, but Agent Runner itself is open-source.

How to try it Kick off Agent Runner at https://www.designarena.ai/agentarena Repo at https://github.com/Design-Arena/agent-runner Use it as a CLI tool: https://pypi.org/project/agent-runner/ pip install agent-runner agentrunner run “create a nextjs replica of Discord”

We hope this provides a provider-agnostic, framework-agnostic, realistic benchmark for state-of-the-art coding agents.

Video demo: https://youtu.be/rdtiuCHatjs