CURRENT MODEL COMPARISON / 2026

Claude Sonnet 5.5 vs Gemini 3.8 Flash

Which current hosted model fits your document-and-tool workflow?

Reviewed Live model evidence ↗
Anthropic

Claude Sonnet 5.5↗

The September 2026 Sonnet release, announced across the Claude API and supported cloud platforms.

Access type
Hosted API
Original release date
Model ID
claude-sonnet-5-5
Announced access
Claude API and supported AWS, Google Cloud and Microsoft platforms
Latest lifecycle note
Cache-read price update announced October 7, 2026
License / terms
Provider service terms

Use the exact Claude endpoint and current model documentation for limits and prices. Cache-read pricing changed on October 7, 2026; a launch-era estimate can be stale.

Official source ↗Latest artifacts and release journal →
Google

Gemini 3.8 Flash↗

A September 2026 generally available Gemini release for software engineering, agents and enterprise workflows.

Access type
Hosted API
Original release date
Model ID
gemini-3.8-flash
Source focus
Software engineering, autonomous agents and enterprise workflows
License / terms
Provider service terms

The provider announcement describes intended uses, not an independent result in your application. Check accepted inputs, thinking controls and current pricing on the selected Gemini endpoint.

Official source ↗Latest artifacts and release journal →

The decision to test

Use a document set with known answers and a separate agent task set. Sonnet 5.5 and Gemini 3.8 Flash are September 2026 editions; their current native APIs and measured application behavior matter more than family-level labels.

Separate retrieval failures from reasoning failures

Require the answer to identify the supporting document or passage. Score missing evidence, invented details and wrong conclusions separately. That makes it easier to distinguish an input/context issue from a model-quality issue.

Use an endpoint-specific input check

Confirm that your chosen Gemini and Claude endpoints accept the files and tool schemas you need. Upload handling, streaming and thinking controls belong in the adapter checklist before a quality evaluation.

Three criteria for this comparison

  1. Evidence-grounded answers from identical source documents
  2. Correct tool execution after validation
  3. Retries, full latency 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 →

Independent benchmark evidence

Open the full live comparison →
Latest recorded measurements aligned by exact artifact, benchmark version, source and methodology. These are source results, not tests of Flonno's deployment.
Benchmark / sourceClaude Sonnet 5.5Gemini 3.8 Flash
Artificial Analysis Intelligence Indexv4.3 · Artificial Analysis56 index_pointsMeasured Sep 29, 2026Original result ↗40.9 index_pointsMeasured Sep 20, 2026Original result ↗

Artificial Analysis observations are refreshed by the integrated Radar. Differences in artifact, benchmark version or method prevent a score comparison. Read the evidence methodology →

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 5.5
Gemini 3.8 Flash
Claude Sonnet 5.5

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

Gemini 3.8 Flash

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.

Release coverage and updates

Model journal →

Related current comparisons

Browse current guides →