ARCHIVED MODEL EDITIONS / REFERENCE

Claude Sonnet 4 vs Gemini 2.5 Pro

What should an agent or multimodal evaluation measure?

ARCHIVED REFERENCE

This page compares the older editions named in its title. For current GPT-6, Claude 5.5 and Gemini 3.8 comparisons, open the current comparison library. The historical model identities are preserved for migration and reproducibility.

Anthropic

Claude Sonnet 4↗

A hosted Claude model introduced for coding and agent workflows.

Access type
Hosted API
License / terms
Provider service terms

Native Messages requests differ from OpenAI Chat Completions. A compatibility layer must map tool and streaming behavior correctly.

Official source ↗
Google

Gemini 2.5 Pro↗

A hosted Gemini thinking model for complex and multimodal tasks.

Access type
Hosted API
License / terms
Provider service terms

Gemini API formats and thinking controls differ from other providers. Check current pricing and availability directly.

Official source ↗

The decision to test

Use one harness with provider-specific adapters. Record failures, retries and tool execution results. For long documents, evaluate evidence retrieval and final-answer grounding separately.

Three criteria for this comparison

  1. Successful multi-step execution
  2. Modality support on the selected endpoint
  3. Full request time and complete token usage

Run a fair comparison

Use the same representative inputs and a written answer rubric. Pin the model version and record the endpoint, thinking configuration, quantization when known, context length, output allowance and concurrency. Preserve native request differences in an adapter rather than silently dropping fields.

Measure full request time, error rate and reported usage. For tools, validate arguments and score the result after execution. For images, preserve resolution and preprocessing. A valid response format alone does not establish a correct answer.

Compare cost per accepted result

Calculate input cost plus all billed output, including reasoning where the provider counts it. Add retries and discarded answers. Divide the total by the number of results that pass your quality criteria. Keep API usage cost separate from deployment and engineering cost.

Estimate token costs with the API calculator →
YOUR WORKLOAD

Compare cost per accepted task.

Enter results from your own evaluation. A task should count once it meets your written quality criteria. Include failed attempts and retries in total spend. These inputs stay in this browser and are not a Flonno benchmark.

Claude Sonnet 4
Gemini 2.5 Pro
Claude Sonnet 4

Enter all four values. Attempted tasks must be at least one; accepted tasks cannot exceed attempted tasks.

Gemini 2.5 Pro

Enter all four values. Attempted tasks must be at least one; accepted tasks cannot exceed attempted tasks.

Turn evidence into a deployment decision

A source benchmark can inform your shortlist, while your evaluation shows whether a model finishes the work at an acceptable cost. Keep the chosen endpoint, processing terms and output limits in the decision record. Inclusion in the Radar does not mean the model is served by Flonno.

For the API currently offered here, explore Qwen3.8 Flash 27B and the production evaluation guide.

Related reference comparisons

Browse current guides →