---
title: "Tuning the harness, not the model: a Nemotron 3 Ultra playbook"
url: https://daily.dev/posts/tuning-the-harness-not-the-model-a-nemotron-3-ultra-playbook-1owdvfgkp
source_url: https://www.langchain.com/blog/tuning-the-harness-not-the-model-a-nemotron-3-ultra-playbook
type: article
source: "LangChain"
published: 2026-07-08T19:22:59.200Z
updated: 2026-07-08T19:24:47.702Z
tags: ["ai-agents", "prompt-engineering", "langchain", "langsmith"]
reading_time: 12
upvotes: 0
comments: 0
language: en
---

> ## Documentation Index
> Fetch the complete documentation index at: https://daily.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Tuning the harness, not the model: a Nemotron 3 Ultra playbook

**[LangChain](https://daily.dev/sources/langchain)** · 12 min read · 0 upvotes · 0 comments

## Summary

A practical playbook for tuning the scaffolding around Nemotron 3 Ultra (an open NVIDIA model) rather than the model weights themselves. By iterating on system prompts, tool descriptions, and middleware using a trace-driven eval loop, the authors brought Nemotron's best-run score on the Deep Agents suite to 0.86 — nearly matching Claude Opus 4.8's best of 0.87 — at roughly 10x lower cost (~$4.48 vs ~$43.48 per full suite run). Key findings: targeted single-purpose prompt blocks outperform broad rewrites; context injection at the point of need beats standing system-prompt rules; middleware enforces reliability that prompting can't guarantee; and harness tuning has a hard ceiling where model post-training must take over.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://www.langchain.com/blog/tuning-the-harness-not-the-model-a-nemotron-3-ultra-playbook>

## Similar posts on daily.dev

- [Create a LangChain Deep Agents Harness Profile for NVIDIA Nemotron 3 Ultra to Improve Performance](https://daily.dev/posts/create-a-langchain-deep-agents-harness-profile-for-nvidia-nemotron-3-ultra-to-improve-performance-zjnvgnfwx) · NVIDIA Developer · 3 upvotes · 0 comments

---

Tags: [#ai-agents](https://daily.dev/tags/ai-agents), [#prompt-engineering](https://daily.dev/tags/prompt-engineering), [#langchain](https://daily.dev/tags/langchain), [#langsmith](https://daily.dev/tags/langsmith)

[View this post on daily.dev](https://daily.dev/posts/tuning-the-harness-not-the-model-a-nemotron-3-ultra-playbook-1owdvfgkp)