Neither wins outright: OpenAI: GPT-5.1-Codex-Max is the pick when you need to fit long inputs in one request, Pareto 26.9 when you want the newer model.
| Spec | OpenAI: GPT-5.1-Codex-Max | Pareto 26.9 |
|---|---|---|
| Provider | OpenAI | Unbiased |
| Input price (per 1M tokens) | $1.25 | $2.50 |
| Output price (per 1M tokens) | $10.00 | $7.50 |
| Blended price (3:1 input/output) | $3.44 | $3.75 |
| Cheaper than … of all models we track | 19% | 17% |
| Context window | 400K tokens (~600 pages) | 262K tokens (~393 pages) |
| Larger context than … of all models | 63% | 48% |
| Max output per response | 128K tokens (~96,000 words) | 131K tokens (~98,300 words) |
| Input types | text, image | text, image |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2025-12-04 | 2026-10-13 |
Monthly cost at list price for five common workloads. Token counts per unit are stated so you can scale them to your own traffic. A workload that does not fit a model's context window is marked rather than priced.
| Workload (per month) | OpenAI: GPT-5.1-Codex-Max | Pareto 26.9 | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $294 | $338 | OpenAI: GPT-5.1-Codex-Max saves $43.75 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $250 | $375 | OpenAI: GPT-5.1-Codex-Max saves $125 |
| Coding / tool-using agent 2,000 tasks — each a multi-step task with tool calls and file context (60,000 in / 6,000 out tokens) | $270 | $390 | OpenAI: GPT-5.1-Codex-Max saves $120 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $160 | $245 | OpenAI: GPT-5.1-Codex-Max saves $85.00 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $72.50 | $133 | OpenAI: GPT-5.1-Codex-Max saves $60.00 |
| Capability | OpenAI: GPT-5.1-Codex-Max | Pareto 26.9 | What it lets you do |
|---|---|---|---|
| Tool / function calling | ✓ Yes | ✓ Yes | call your APIs and run agent loops |
| Structured output (JSON schema) | ✓ Yes | ✓ Yes | return JSON that validates against your schema |
| Reasoning / thinking mode | ✓ Yes | — | spend extra tokens thinking before answering hard problems |
| Image input | ✓ Yes | ✓ Yes | read screenshots, charts and scanned pages |
| Audio input | — | — | take speech or audio directly |
| File / PDF input | — | — | accept documents without your own parsing step |
| Image output | — | — | generate images, not just text |
| Built-in web search | ✓ Yes | — | answer from live web results |
| Seed (reproducible sampling) | ✓ Yes | — | repeat a generation for tests and evals |
| Log-probabilities | — | — | read token confidence for classification and scoring |
From each model's published parameters and input/output types. “—” means not advertised, not proven absent.
Neither wins outright: OpenAI: GPT-5.1-Codex-Max is the pick when you need to fit long inputs in one request, Pareto 26.9 when you want the newer model. In short: OpenAI: GPT-5.1-Codex-Max when you need to fit long inputs in one request, you need reasoning / thinking mode, you need built-in web search, you need seed (reproducible sampling); Pareto 26.9 when you want the newer model.
OpenAI: GPT-5.1-Codex-Max is cheaper: $3.44 vs $3.75 per 1M tokens at a typical 3:1 input/output mix, 8% less. For 50,000 support conversations a month that is $294 against $338.
OpenAI: GPT-5.1-Codex-Max costs $1.25 per 1M input tokens and $10.00 per 1M output tokens; Pareto 26.9 costs $2.50 input and $7.50 output. Output tokens are billed separately, so long answers shift the gap.
OpenAI: GPT-5.1-Codex-Max: 400K tokens, about 600 pages, against 262K (about 393 pages) for Pareto 26.9.
Tool calling — OpenAI: GPT-5.1-Codex-Max: yes, Pareto 26.9: yes. JSON-schema structured output — OpenAI: GPT-5.1-Codex-Max: yes, Pareto 26.9: yes.
Yes, both accept image input.
No free variant is listed for either; both are pay-per-token.
OpenAI: GPT-5.1-Codex-Max can write up to 128K tokens (about 96,000 words) per response; Pareto 26.9 up to 131K (about 98,300 words).
OpenAI: GPT-5.1-Codex-Max was listed on 2025-12-04; Pareto 26.9 on 2026-10-13.
GPT-5.1-Codex-Max is OpenAI’s latest agentic coding model, designed for long-running, high-context software development tasks. It is based on an updated version of the 5.1 reasoning stack and trained on agentic...
Full OpenAI: GPT-5.1-Codex-Max specs →Pareto is a multimodal composite model built for research, coding, and agentic workflows, while delivering frontier-level performance across a broad range of general-purpose tasks.
Full Pareto 26.9 specs →