Model comparison
Claude Opus 5 vs GPT-5.3-Codex
Anthropic against OpenAI, compared on context, price, and verified benchmark results.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: High — see receipts below
Anthropic
Claude Opus 5
Frontier
OpenAI
GPT-5.3-Codex
Frontier
| Specification | Claude Opus 5 | GPT-5.3-Codex |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Tier | Frontier | Frontier |
| Context window | Winner: 1M | 400K |
| Max output | 128K | 128K |
| Input / 1M tokens | $5 | Winner: $1.75 |
| Output / 1M tokens | $25 | Winner: $14 |
| Weights | Closed | Closed |
| Parameters | Not disclosedUnverified | Not disclosedUnverified |
| Reasoning levels | adaptive | none, low, medium, high, xhigh, max |
| Modalities | text, image | text, image |
| API model id | claude-opus-5 | gpt-5.3-codex |
| Released | July 24, 2026 | February 5, 2026 |
| Artificial Analysis Intelligence Index [max] (2026-08-14) | 63 | Not verifiedUnverified |
| Artificial Analysis Intelligence Index [high] (2026-08-14) | Not verifiedUnverified | 52 |
| Humanity's Last Exam (2026-09-01) | 63.6 | Not verifiedUnverified |
| Terminal-Bench 2.1 (2026-09-03) | 86.7 | Not verifiedUnverified |
Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.
Benchmark receipts
- 2026-09-03: Meta Muse Spark 1.3 launch table (independent cross-vendor run; conflicts with Google's 89.1 — both preserved)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
- 2026-09-02: Google Gemini 3.8 Flash launch eval table (independent cross-vendor run)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
- 2026-09-01: Anthropic Fable 5.1 comparison table (vendor, with tools; 56.6 no tools)Frontier-knowledge ceiling: extremely hard multi-domain questions written to be near-impossible without deep expertise. Comparability: comparable with caveat — Subset/tool configurations (text-only vs with-tools) differ between vendors and materially change scores; must match configuration to compare.
- 2026-08-14: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
Pricing tiers: Claude Opus 5: Standard $5/$25 per MTok; cache reads 10% of base input. Knowledge cutoff May 2026. · GPT-5.3-Codex: Standard $1.75/$14 per MTok; cached input $0.175/MTok; Fast mode $3.50/$28. Purpose-built for the Codex agent.
Claude Opus 5
Claude Opus 5 is Anthropic's top model for complex agentic coding and enterprise work — superseded at the top of the Artificial Analysis Index by Fable 5.1 (2026-09-01) but stronger on price.
Best for
- Complex agentic coding
- Enterprise work
- Long-context analysis
Watch out
Output costs 5x input; long generations dominate the bill.
GPT-5.3-Codex
GPT-5.3-Codex is OpenAI's coding-specialised model powering the Codex agent at $1.75/$14.
Best for
- Autonomous coding
- Repo-scale refactors
- Test generation
Watch out
Tuned for coding, not general chat; use GPT-5.6 for broad reasoning.
When the cheaper one wins
GPT-5.3-Codex is cheaper on output at $14 per million tokens against $25 for Claude Opus 5 — about 1.8×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.
Run the model pickerEvidence confidence: High
How strong and complete the evidence behind this comparison is — not a prediction of which model is better.
- Pricing verified on both sides — Input and output rates are verified for both models.
- 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
- 1 shared named benchmark with differing scores — Measured on: Artificial Analysis Intelligence Index.
- Verified within the last 90 days — Newest catalog check was 8 days ago.
- Both models carry source citations — Each side has at least two catalog sources on record.
Source receipts
Each catalog figure was checked against the provider or an independent second source on the date shown.
- Claude Opus 5: Anthropic — Claude Opus 5 (accessed 2026-08-29)
- Claude Opus 5: Anthropic news — Claude Opus 5 (accessed 2026-08-29)
- GPT-5.3-Codex: OpenAI — Introducing GPT-5.3-Codex (accessed 2026-08-29)
- GPT-5.3-Codex: OpenAI API pricing (gpt-5.3-codex $1.75/$14) (accessed 2026-08-29)
Related comparisons
- Claude Opus 5 vs DeepSeek V4 Flash
- Claude Opus 5 vs Gemini 3.6 Flash
- Claude Opus 5 vs Gemini 3.7 Flash
- Claude Opus 5 vs Gemini 3.8 Flash
- Claude Opus 5 vs GPT-5.6 Luna
- Claude Fable 5.1 vs Claude Opus 5
Diving deeper on one model? Claude Opus 5 · GPT-5.3-Codex
Common questions
Claude Opus 5 vs GPT-5.3-Codex
Answered from the verified figures on this page rather than general guidance.
Is Claude Opus 5 or GPT-5.3-Codex cheaper for input?
GPT-5.3-Codex is cheaper at $1.75 per million input tokens, against $5 for Claude Opus 5 — roughly 2.9× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Claude Opus 5 has tiered pricing: Standard $5/$25 per MTok; cache reads 10% of base input. Knowledge cutoff May 2026. GPT-5.3-Codex has tiered pricing: Standard $1.75/$14 per MTok; cached input $0.175/MTok; Fast mode $3.50/$28. Purpose-built for the Codex agent.
Is Claude Opus 5 or GPT-5.3-Codex cheaper for output?
GPT-5.3-Codex is cheaper at $14 per million output tokens, against $25 for Claude Opus 5 — roughly 1.8× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Claude Opus 5 has tiered pricing: Standard $5/$25 per MTok; cache reads 10% of base input. Knowledge cutoff May 2026. GPT-5.3-Codex has tiered pricing: Standard $1.75/$14 per MTok; cached input $0.175/MTok; Fast mode $3.50/$28. Purpose-built for the Codex agent.
Which has the larger context window, Claude Opus 5 or GPT-5.3-Codex?
Claude Opus 5 accepts 1M tokens against 400K for GPT-5.3-Codex. This only matters if you routinely send very long documents or large codebases.
Do Claude Opus 5 and GPT-5.3-Codex support the same reasoning levels?
Claude Opus 5 exposes adaptive, while GPT-5.3-Codex exposes none, low, medium, high, xhigh, max.
Should I use Claude Opus 5 or GPT-5.3-Codex?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Claude Opus 5 suits complex agentic coding; GPT-5.3-Codex suits autonomous coding.
Next step
Choosing between them
The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.
- Input price: GPT-5.3-Codex costs $1.75 per 1M tokens versus $5 for Claude Opus 5 — a 2.9x difference at the headline tier.
- Context: Claude Opus 5 takes 1M against 400K for GPT-5.3-Codex — only decisive if your prompts approach the smaller window.
- Measured capability: Claude Opus 5 leads Artificial Analysis Intelligence Index 63 to 52 (measured 2026-08-14).
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.