Standard Compute
Model comparison 2026

Claude Opus 5.5 vs GPT-5.3-Codex

Claude Opus 5.5
Anthropic · Frontier · Proprietary
$8.80/1M · 1M ctx
GPT-5.3-Codex
OpenAI · Balanced · Proprietary
$5.42/1M · 400K 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
Opus 5.5
GPT-5.3-Codex
Maker
Anthropic
OpenAI
Blended price / 1M
$8.80
$5.42
Input / output
$4.00 in · $20 out / 1M tokens
$1.75 in · $14 out / 1M tokens
Context window
1M
400K
Open weights
No
No
Tool use
Yes
Yes
Reasoning
Yes
Yes
Output Quality
10.0
8.8
Agentic Ability
10.0
9.3
Speed
7.6
7.8
Value for money
7.4
7.8
Reliability
9.5
8.7

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

Verdict: Opus 5.5 or GPT-5.3-Codex?

Updated 2026-10-13

Choose Claude Opus 5.5 if you want the hardest coding and agent work, as the default flagship instead of Fable. Choose GPT-5.3-Codex if you want codex CLI users and dedicated coding agents.

In our editorial scoring, Claude Opus 5.5 leads in 3 of five dimensions (output quality, agentic ability and reliability), while GPT-5.3-Codex leads in 2. On price, Claude Opus 5.5 runs about $8.80 per 1M tokens (blended) and is proprietary; GPT-5.3-Codex is about $5.42 and proprietary.

Where Opus 5.5 falls short
  • Twice Sonnet 5.5's price per token for a small measured gain
  • Released September 2026, so its long-run track record is still short
Full Opus 5.5 breakdown →
Where GPT-5.3-Codex falls short
  • Narrower than a general flagship outside coding
  • Mid-tier pricing
Full GPT-5.3-Codex breakdown →

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Current frontier models Claude Opus 5.5 · Claude Sonnet 5.5

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