Harness: [Improvement]: Default instructions should request concise rationale/progress instead of thought process

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@eavanvalkenburg is already working on this.

Since Sep 20, 2026.

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Description

.NET agents python

Summary

The default Harness instructions in both .NET and Python currently ask the model to:

Explain your reasoning and thought process

and also ask it to keep the user informed about its "thought process" between tool calls.

For a provider-neutral agent framework, the default should request concise progress, rationale and results, not hidden/internal reasoning or chain-of-thought.

Why this matters

Framework defaults are inherited by applications unless they explicitly override HarnessInstructions.

The current wording can:

  • encourage models to expose private/internal reasoning;
  • behave inconsistently across providers that treat reasoning differently;
  • cause applications to override the whole Harness instruction block just to avoid this behavior;
  • conflate useful user-facing progress with hidden chain-of-thought.

We encountered this while integrating HarnessAgent into a production assistant and replaced the default Harness instructions even though the rest of the defaults were useful.

Suggested direction

For example:

Keep the user informed with concise progress updates when useful.
Explain decisions, actions, results, and important trade-offs at a high level.
Do not expose private chain-of-thought or hidden reasoning.

The exact wording can follow project conventions.

Scope

This appears in both:

  • .NET HarnessAgent.DefaultInstructions
  • Python DEFAULT_HARNESS_INSTRUCTIONS

No new abstraction is required.

Code Sample
Language/SDK

Both

Dominant language
Python
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