Standard Compute
Model comparison 2026

Claude Sonnet 5.5 vs GPT-6 Luna

Claude Sonnet 5.5
Anthropic · Balanced · Proprietary
$4.40/1M · 1M ctx
GPT-6 Luna
OpenAI · Budget · Proprietary
$0.22/1M · 1.1M ctx

Community vote

Pick a winner in each dimension. You can change your vote any time.

Output Quality
Correctness and depth of what it produces
Agentic Ability
Tool calls, instruction-following, and multi-step tasks
Speed
Tokens per second and time-to-first-token
Value for money
How much capability you get per dollar
Reliability
Consistent results: fewer refusals, loops and format breaks

Specs and pricing side by side

Spec
Sonnet 5.5
GPT-6 Luna
Maker
Anthropic
OpenAI
Blended price / 1M
$4.40
$0.22
Input / output
$2.00 in · $10 out / 1M tokens
$0.10 in · $0.50 out / 1M tokens
Context window
1M
1.1M
Open weights
No
No
Tool use
Yes
Yes
Reasoning
Yes
Yes
Output Quality
9.8
8.7
Agentic Ability
9.8
8.5
Speed
8.4
9.3
Value for money
8.8
9.4
Reliability
9.4
9.1

Pricing and capabilities synced from the OpenRouter catalogue. Scores are editorial (0–10).

Verdict: Sonnet 5.5 or GPT-6 Luna?

Updated 2026-10-13

Choose Claude Sonnet 5.5 if you want the everyday default for coding agents, escalating to Opus 5.5 only for the hardest tasks. Choose GPT-6 Luna if you want cheap, fast subtasks, routing and subagents in OpenAI-based stacks.

In our editorial scoring, Claude Sonnet 5.5 leads in 3 of five dimensions (output quality, agentic ability and reliability), while GPT-6 Luna leads in 2. On price, Claude Sonnet 5.5 runs about $4.40 per 1M tokens (blended) and is proprietary; GPT-6 Luna is about $0.22 and proprietary.

Where Sonnet 5.5 falls short
  • Artificial Analysis flags it as very verbose, which adds output tokens
  • Released September 2026, so its long-run track record is still short
Full Sonnet 5.5 breakdown →
Where GPT-6 Luna falls short
  • Weak on long agentic runs (16.4% on Terminal-Bench 4.0)
  • Clear quality step below GPT-6.1 Sol
Full GPT-6 Luna breakdown →

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