GPT-5.3 Codex vs Claude Sonnet 5
GPT-5.3 Codex and Claude Sonnet 5 compared on current per-token rates, context window, and capabilities — both callable through one OpenAI-compatible endpoint with per-request cost traces.
| Spec | GPT-5.3 Codex | Claude Sonnet 5 |
|---|---|---|
| Input / 1M tokens | $0.48 | $0.90 |
| Output / 1M tokens | $3.85 | $4.50 |
| Cached input / 1M tokens | $0.05 | $0.15 |
| Context window | 200k | 200k |
| Capabilities | chat, streaming, tool_calling, vision | chat, streaming, tool_calling, vision |
| Detail page | View details | View details |
What a workload actually costs
For a workload of 1M input plus 1M output tokens at current rates: GPT-5.3 Codex comes to $4.33, Claude Sonnet 5 comes to $5.40 — GPT-5.3 Codex is about 20% cheaper on this mix. Real workloads skew heavily toward input tokens, so weigh the input rate by your own ratio; prompt-cache hits bill at the cached-input rate where supported.
Run both through one endpoint
Both models are behind the same OpenAI-compatible endpoint, so an A/B test is a one-string change — same key, same code, and every request traced with tokens, cost, and latency in the dashboard:
compare.sh
curl https://api.router.one/v1/chat/completions \
-H "Authorization: Bearer sk-your-router-one-key" \
-H "Content-Type: application/json" \
-d '{"model": "gpt-5.3-codex", "messages": [{"role": "user", "content": "Hello"}]}'
# Same request, other model — change one string:
# "model": "anthropic/claude-sonnet-5"FAQ
- Is GPT-5.3 Codex cheaper than Claude Sonnet 5?
- At current posted rates, GPT-5.3 Codex is the cheaper of the two (input $0.48 vs $0.90, output $3.85 vs $4.50 per 1M tokens). Rates change; the /models page is the live source of truth.
- Can I switch between GPT-5.3 Codex and Claude Sonnet 5 without changing code?
- Yes. Both are served through the same OpenAI-compatible endpoint, so switching is changing the model string in the request — the key, base URL, and request shape stay identical.
- Where do these numbers come from?
- Specs and prices on this page render from the live Router One catalog — the same data as the /models page — and refresh with it. Pricing methodology is documented on /pricing-methodology.