Enhance Claude Code Plugin Evaluation: System Prompt Fix

Jan 17, 2026 by Editorial Team 57 views

Enhance Claude Code Plugin Evaluation: System Prompt Configuration

Hey guys! Let's dive into an important update that improves how we evaluate Claude Code plugins. The goal here is to make sure our evaluations are as accurate and consistent as possible, and it all revolves around properly configuring the system prompt during the critical Stage 3 execution. We're talking about a feature addition designed to explicitly configure the Agent SDK's system prompt, specifically with the "claude_code" preset. This adjustment ensures that Claude operates with the expected behaviors, enabling more reliable and effective plugin evaluations. By default, Claude Code may not have the built-in behaviors and instructions that Claude Code users expect. This lack of configuration can affect how Claude Code interacts with the plugins and tools it's supposed to use. In this article, we'll explain why this update is needed, the proposed solutions, and what alternatives we considered. Let's make sure we understand the benefits of this update for the entire evaluation process. This means our evaluations will be more accurate, and that we can trust the results and feedback we receive. So, this enhancement ensures Claude Code will function just as it is intended to.

The Core Issue: System Prompt and Agent SDK

So, what's the deal, guys? The heart of this issue lies in how the Agent SDK, particularly in Stage 3 execution, currently handles the systemPrompt. The Agent SDK, starting from version v0.1.0, decided to move away from including a default system prompt. This change offers greater flexibility, but it also means we need to explicitly configure this setting. The absence of a configured system prompt means that Claude might behave differently, potentially affecting how it recognizes skills, triggers agents, understands commands, and utilizes tools. The existing code, specifically in agent-executor.ts and session-batching.ts, doesn't explicitly set the systemPrompt option. This is where the problem starts, because Claude Code relies on the system prompt for its core functionalities, such as determining how to invoke skills, the agent's capabilities, command patterns, and expected tool behaviors. Without this prompt, Claude operates without these crucial instructions, leading to inconsistencies. To address this, we propose integrating the systemPrompt configuration into Stage 3 execution. This update ensures that Claude has access to the necessary instructions and behaviors during plugin evaluation, thus improving the reliability and consistency of our evaluations. This proposed solution is all about making sure Claude Code performs the way it is supposed to. This enhancement makes sure the tools can be used in the appropriate manner.

Code Deep Dive: What's Missing?

Let's take a closer look at the current implementation to understand the problem better. The buildQueryInput function, a critical part of the process, currently doesn't set the systemPrompt. This means that when the system is executing the prompt and considering the plugins and settings, the important system prompt is missing. This is like starting a race without giving the runner the route to follow; the runner will not know where to go. The SDK documentation shows how to use the Claude Code system prompt. The proposed solution involves modifying the buildQueryInput functions to include the systemPrompt option, using the "claude_code" preset. This will ensure that Claude is initialized with the expected instructions. It's like giving the runner the map and saying "Here's where to go, and here's how to get there". By adding the configuration, we're making sure that Claude Code works as intended during our plugin evaluations. This modification ensures that Claude has the context it needs to correctly process prompts, understand tools, and behave as expected. It ensures the evaluation process is much more accurate and consistent. This guarantees that all instructions are present, allowing the tool to perform as it should. This ensures a consistent environment for plugin execution.

The Proposed Solution: Configuring the System Prompt

So, what's the plan to fix this, friends? The proposed solution involves two main steps, both of which are designed to integrate the systemPrompt configuration into Stage 3 execution, making sure Claude Code behaves consistently during plugin evaluation. Let's break down the approach to make sure we're all on the same page. The main solution is to update the buildQueryInput functions to include the systemPrompt option. By including the systemPrompt option, we are making sure that Claude has the information needed to perform correctly. The code will set the systemPrompt to the "claude_code" preset. This will ensure that Claude has all the right instructions.

Step-by-Step Implementation

Updating buildQueryInput: The first part of the fix involves updating the buildQueryInput functions. We'll add the systemPrompt option, using the "claude_code" preset. This step ensures that Claude starts with the correct instructions. This is like setting up a stage for the main performance. This simple code update will ensure that the system prompt is configured. Here's a quick look at the code snippet. This change will make sure Claude Code is correctly configured before the prompt is executed. The goal here is consistency. By explicitly setting the system prompt, we ensure that every evaluation starts from the same point, with Claude knowing how to use its tools. These modifications ensure that the necessary instructions are present during execution.
Configuration Options: In order to make this feature even more versatile, we're also considering making the system prompt configurable. We plan to add options within the ExecutionConfigSchema. This allows users to select how the system prompt is handled. The options are claude_code, none, and custom. This way, the users have greater control. The claude_code setting is recommended for plugin evaluation because it lets you run with Claude Code behaviors. The none setting allows us to run without any system prompt. It's useful for baseline comparisons, which means seeing how the system behaves without specific guidance. The custom setting lets users provide their system prompt. This is useful for specialized testing. These options make our tool more versatile and adapt to different testing scenarios. This flexibility makes the plugin evaluations and comparisons more precise.

Alternatives and Why We Chose the Current Path

Alright, let's talk about the other ideas we kicked around before settling on the solution. We thought about different approaches, and each one came with its own set of trade-offs. We evaluated a few different choices to make sure we're on the right track.

Leave as-is: One option was to simply leave things as they were. However, this could lead to inconsistent behavior during evaluations. The default prompt is not set, so you can have some unusual results. While Claude would still function, its performance and interaction with plugins might differ. In the end, we decided against this option, because it could lead to unpredictable results during our evaluations.
Document the behavior: Another thought was to document the change and warn users. This would inform users that the behavior may differ. This is not ideal because the goal here is to make Claude Code plugin evaluations as accurate and reliable as possible. We decided that documentation alone wouldn't solve the core problem of ensuring consistency in our evaluations.
Make it configurable only: Another suggestion was to let users choose. Don't set a default, but allow users to choose from different system prompts. However, without a default, users might be uncertain of the best configuration for a standard evaluation. By setting the claude_code preset as the default, we ensure that new users get the behavior that is expected.

The Final Decision

Ultimately, we decided to set the Claude Code preset as the default. This is because we're evaluating Claude Code plugins. This guarantees that Claude will function properly during the process. This approach gives us the best balance of usability, consistency, and alignment with the intended functionality. This strategy ensures the most accurate, reliable, and user-friendly plugin evaluations possible. This guarantees that the evaluation process is as reliable as possible. This approach is intended to provide the best possible experience.

The Impact: What This Means for You

So, what does this all mean for you and how you use our tool, friends? This update will lead to more reliable plugin evaluations and provides a more consistent testing environment. This allows users to accurately assess the plugins. This leads to more reliable and predictable evaluations.

Enhanced Consistency

First, consistency is what we aim for. By ensuring that Claude Code is consistently initialized with the "claude_code" system prompt, we remove a major source of variability. The evaluations will be more consistent. This consistency allows us to compare and measure the performance of plugins. This will make debugging easier, and help developers. This ensures that every test will run with the same starting conditions.

Improved Accuracy

By ensuring that Claude understands commands, tools, and skills, the accuracy of our evaluations will significantly improve. This means that when you test a plugin, you can have greater confidence in the results, knowing that Claude is behaving as expected. This will ensure that our results are accurate. This allows developers to trust the feedback. This is essential for the evaluation process.

Better Plugin Performance

With improved accuracy, developers can create high-quality plugins that will perform much better. This means that users will get better functionality. It ensures a better user experience. This helps the entire community.

Wrapping Up: Making Evaluations Better

All right, let's bring this home, guys. Adding the Claude Code system prompt configuration to Stage 3 execution is a critical improvement. It addresses the missing system prompt in the Agent SDK. It will improve consistency, accuracy, and overall plugin performance. This update sets the "claude_code" preset as the default. This ensures that Claude has all the necessary instructions. It ensures it will perform as intended during plugin evaluations. This fix will make evaluations more predictable. This is a crucial step towards making our platform more reliable. We're committed to making our evaluation processes better. By making these changes, we can guarantee that our users have the best experience. By ensuring the proper setup, we're guaranteeing that evaluations are as good as they can be. This will let us develop new plugins.