GPT-5.1-Codex
by OpenAI · openai/gpt-5.1-codex · #335 cheapest of 422 paid models
Prices updated Sep 19, 2026, 6:21 PM UTC · refreshed hourly
GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows. It is designed for both interactive development sessions and long, independent execution of complex engineering tasks....
Compare vs:Claude Sonnet 5Claude Opus 4.6Claude Haiku 4.5Gemini 3.6 Flash
Pricing
Input
$1.25
per 1M tokens
Output
$10.00
per 1M tokens
Blended (3:1)
$3.44
3 input : 1 output
Cache read
$0.13
per 1M cached tokens
Cache write
—
per 1M tokens
Cache & batch economics
Effective prices for GPT-5.1-Codex with prompt caching.
| Cache hit rate | Effective blended $/1M | Example request* | vs no cache |
|---|---|---|---|
| 0% | $3.44 | $0.1375 | — |
| 50% | $3.02 | $0.0815 | −41% |
| 90% | $2.68 | $0.0367 | −73% |
*Example: 100K sticky context + 2K new input + 1K output. Batch discount is an approximate 50% off list rates for this provider’s batch API. Confirm on the vendor’s pricing page.
What a request costs
| Workload | Input tokens | Output tokens | Cost / request | Cost / 1K requests |
|---|---|---|---|---|
| Short chat message | 500 | 300 | $0.003625 | $3.62 |
| Document summary | 8,000 | 1,000 | $0.02 | $20.00 |
| Codebase question (RAG) | 30,000 | 2,000 | $0.0575 | $57.50 |
| Long-context analysis | 150,000 | 5,000 | $0.2375 | $237.50 |
Performance
Intelligence Index
23.7
AA composite quality
Coding Index
—
Math Index
95.7
Agentic Index
—
Output speed
0 tok/s
median
Time to first token
0s
median
Time to first answer
0s
after reasoning tokens
Artificial Analysis benchmarks
| Benchmark | Score |
|---|---|
| MMLU-Pro | 86.0% |
| GPQA Diamond | 86.0% |
| Humanity's Last Exam | 25.7% |
| LiveCodeBench | 84.9% |
| AIME 2025 | 95.7% |
| IFBench | 70.0% |
| AA-LCR (Long Context Reasoning) | 69.3% |
| Terminal-Bench Hard | 34.8% |
| τ²-Bench (Telecom) | 83.0% |
Design Arena Elo
| Category | Elo |
|---|---|
| Website | 1,174 |
| Web apps | 1,033 |
| Full-stack | 1,086 |
| Mobile apps | 1,191 |
| UI components | 1,252 |
| Data viz | 1,228 |
| Game dev | 1,161 |
| Code categories | 1,167 |
Specs
Context window
400K
tokens
Max output
128K
tokens
Input modalities
text, image
Tokenizer
GPT