CURRENT MODEL COMPARISON / 2026

Claude Haiku 5.5 vs GPT-6 Luna

Which newly released model should you test for high-volume structured decisions?

Reviewed Live model evidence ↗
Anthropic

Claude Haiku 5.5↗

An October 2026 Claude release aimed at high-volume, latency-sensitive work, with adaptive thinking.

Access type
Hosted API
Original release date
Model ID
claude-haiku-5-5
Announced context
1 million tokens
Announced maximum output
128,000 tokens
Thinking
Adaptive thinking with effort control
License / terms
Provider service terms

Migration from Haiku 4.5 needs attention: manual budget_tokens thinking, sampling parameters and assistant prefill can return 400 errors on Haiku 5.5.

Official source ↗Latest artifacts and release journal →
OpenAI

GPT-6 Luna↗

A September 2026 reasoning model with text and image inputs and text output.

Access type
Hosted API
Original release date
Model ID
gpt-6-luna
Input / output
Text and image inputs; text output
API formats
Responses and Chat Completions; Decisions beta added October 6, 2026
License / terms
Provider service terms

Responses and Chat Completions are supported; the Decisions API was added in beta on October 6, 2026. Evaluate that endpoint separately and recheck prices and token tiers.

Official source ↗Latest artifacts and release journal →

The decision to test

Choose labeled inputs and hold back a test set. Haiku 5.5 launched October 7, 2026; GPT-6 Luna launched September 22. Both are candidates for a routine-work evaluation, with different native reasoning and endpoint choices.

Do not silently compare different endpoints

GPT-6 Luna gained a Decisions API beta on October 6, while its Responses and Chat Completions endpoints remain separate choices. Record the endpoint explicitly. A Decisions experiment should be evaluated independently from a general generation request.

Count valid-but-wrong output

A JSON validator only catches format errors. Use expected values to score classifications and extraction fields, then include repair and retries in the accepted-result cost. Keep Haiku's effort setting in the recorded configuration.

Three criteria for this comparison

  1. Correct values as well as valid schemas
  2. Tail latency under production-like concurrency
  3. Retries and total billed output per accepted decision

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 Haiku 5.5GPT-6 Luna
Artificial Analysis Intelligence Indexv4.3 · Artificial Analysis43.4 index_pointsMeasured Oct 8, 2026Original result ↗38.1 index_pointsMeasured Oct 1, 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 Haiku 5.5
GPT-6 Luna
Claude Haiku 5.5

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

GPT-6 Luna

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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