Evaluate Claude Opus 4.8 on Advanced Coding Tasks

This prompt chain evaluates Claude Opus 4.8 - Anthropic's most capable model for complex reasoning and agentic coding - on hard coding challenges. It tests bug diagnosis across multiple system boundaries, production-quality code generation with proper error handling, and code review with nuanced, prioritized feedback using the xhigh effort level and adaptive thinking.

Use this workflow when you need to benchmark or validate Claude Opus 4.8's performance on complex coding tasks that require multi-step reasoning, cross-system debugging, or production-grade code output. It's ideal for evaluating whether Opus 4.8 meets your standards for agentic coding workflows or long-horizon development tasks.

Do NOT use this if you need basic code completion or simple syntax fixes - the xhigh effort level and adaptive thinking overhead are unnecessary for straightforward tasks. Avoid this workflow if you haven't set explicit thinking: { type: adaptive } configuration, as the model will run without extended thinking even at high effort levels.

You provide an Anthropic API key and run the evaluation suite against predefined coding test cases covering bug diagnosis, code generation, and review scenarios.

Opus 4.8 is accessible through multiple providers:

• Anthropic Messages API - Direct access via anthropic:messages:claude-opus-4-8
• AWS Bedrock - bedrock:us.anthropic.claude-opus-4-8 or bedrock:converse:us.anthropic.claude-opus-4-8
• Google Vertex AI - vertex:claude-opus-4-8 with config.region: global
• Azure AI Foundry - Point anthropic:messages:claude-opus-4-8 at https://<resource>.services.ai.azure.com/anthropic via apiBaseUrl

Across all four providers, promptfoo automatically omits unsupported sampling parameters (temperature, top_p, top_k) that Opus 4.8 rejects at the model level.

Install and run the evaluation:

npx promptfoo@latest init --example anthropic/opus-4-8-coding
cd opus-4-8-coding

Then execute the test suite:

# Set your API key
export ANTHROPIC_API_KEY=your_api_key_here

# Run the evaluation
npx promptfoo@latest eval

# View results
npx promptfoo@latest view

Opus 4.8 builds on 4.7's feature set with no breaking API changes, adding enhanced capability specifically for long-horizon agentic coding and complex reasoning scenarios. Adaptive thinking is opt-in - set thinking: { type: adaptive } to let the model decide when and how much to reason per request. The effort parameter defaults to high; xhigh is available and recommended for coding and agentic work. Pair high effort with a large max_tokens value.