CURRENT MODEL COMPARISON / 2026

GPT-6.1 Sol vs Claude Opus 5.5

Should a long-running coding workflow use the latest Sol or Opus edition?

Reviewed Live model evidence ↗
OpenAI

GPT-6.1 Sol↗

A September 2026 release for complex coding and professional work, available through Responses and Chat Completions.

Access type
Hosted API
Original release date
Model ID
gpt-6.1-sol
API formats
Responses and Chat Completions
Latest lifecycle note
Ultrafast mode added to Responses on October 8, 2026
License / terms
Provider service terms

OpenAI directs tool-calling workflows to the Responses API. Record the service tier and reasoning setting; Ultrafast mode was added on October 8, 2026.

Official source ↗Latest artifacts and release journal →
Anthropic

Claude Opus 5.5↗

A September 2026 Claude release for long-running agentic coding and knowledge work.

Access type
Hosted API
Original release date
Model ID
claude-opus-5-5
Announced context
1 million tokens by default
Announced maximum output
128,000 tokens
Thinking
Always-on adaptive thinking
License / terms
Provider service terms

Always-on adaptive thinking affects output usage and latency. Announced model limits and standard prices do not describe every cloud platform or inference configuration.

Official source ↗Latest artifacts and release journal →

The decision to test

Use tasks that require multiple edits, tests and recovery. GPT-6.1 Sol launched September 29, 2026, and Opus 5.5 launched September 22. Measure task completion and total work, including unsuccessful attempts.

Set a verifiable stopping condition

Specify the expected change, tests and files before execution. Stop at a fixed task or budget boundary. Report incomplete work as incomplete even when the agent produces a polished explanation.

Account for always-on thinking

Opus 5.5 has always-on adaptive thinking. Record the full usage response and time to a final usable artifact. Do not compare only visible answer tokens against a configuration that reports reasoning separately.

Three criteria for this comparison

  1. Finished changes that pass the complete test suite
  2. Recovery from tool errors and partial progress
  3. Total accepted-task cost including reasoning

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 / sourceGPT-6.1 SolClaude Opus 5.5
Artificial Analysis Intelligence Indexv4.3 · Artificial Analysis51.8 index_pointsMeasured Sep 30, 2026Original result ↗57.6 index_pointsMeasured Sep 22, 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.

GPT-6.1 Sol
Claude Opus 5.5
GPT-6.1 Sol

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

Claude Opus 5.5

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 →

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