Choose Inception: Mercury 2.5 if…
- cost matters at scale — it is 90% cheaper on a typical 3:1 input/output mix ($6.00 vs $58.75 a month for 50,000 support chats)
- you want the newer model — released 2026-09-08, 10 months after the other
Inception: Mercury 2.5 vs OpenAI: GPT-5.1-Codex-Mini
Neither wins outright: Inception: Mercury 2.5 is the pick when cost matters at scale, OpenAI: GPT-5.1-Codex-Mini when you need to fit long inputs in one request.
Key numbers
| Spec | Inception: Mercury 2.5 | OpenAI: GPT-5.1-Codex-Mini |
|---|---|---|
| Provider | Inception | OpenAI |
| Input price (per 1M tokens) | $0.04 | $0.25 |
| Output price (per 1M tokens) | $0.15 | $2.00 |
| Blended price (3:1 input/output) | $0.07 | $0.69 |
| Cheaper than … of all models we track | 85% | 47% |
| Context window | 260K tokens (~390 pages) | 400K tokens (~600 pages) |
| Larger context than … of all models | 46% | 63% |
| Max output per response | 66K tokens (~49,200 words) | 128K tokens (~96,000 words) |
| Input types | text | image, text |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2026-09-08 | 2025-11-13 |
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What it costs for real workloads
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) | Inception: Mercury 2.5 | OpenAI: GPT-5.1-Codex-Mini | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $6.00 | $58.75 | Inception: Mercury 2.5 saves $52.75 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $6.30 | $50.00 | Inception: Mercury 2.5 saves $43.70 |
| 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) | $6.60 | $54.00 | Inception: Mercury 2.5 saves $47.40 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $4.10 | $32.00 | Inception: Mercury 2.5 saves $27.90 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $2.15 | $14.50 | Inception: Mercury 2.5 saves $12.35 |
Capabilities side by side
| Capability | Inception: Mercury 2.5 | OpenAI: GPT-5.1-Codex-Mini | 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 | ✓ Yes | spend extra tokens thinking before answering hard problems |
| Image input | — | ✓ 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.
Price history
- Inception: Mercury 2.5: price unchanged since we started tracking it on 2026-09-09.
- OpenAI: GPT-5.1-Codex-Mini: price unchanged since we started tracking it on 2026-03-10.
Which should you choose?
Choose OpenAI: GPT-5.1-Codex-Mini if…
- you need to fit long inputs in one request — 400K tokens is roughly 600 pages, against 390
- you need image input — to read screenshots, charts and scanned pages; Inception: Mercury 2.5 does not advertise it
- you need built-in web search — to answer from live web results; Inception: Mercury 2.5 does not advertise it
- you need seed (reproducible sampling) — to repeat a generation for tests and evals; Inception: Mercury 2.5 does not advertise it
- you generate long outputs in one go — up to 128K tokens (about 96,000 words) per response
Frequently asked questions
Is Inception: Mercury 2.5 better than OpenAI: GPT-5.1-Codex-Mini?
Neither wins outright: Inception: Mercury 2.5 is the pick when cost matters at scale, OpenAI: GPT-5.1-Codex-Mini when you need to fit long inputs in one request. In short: Inception: Mercury 2.5 when cost matters at scale, you want the newer model; OpenAI: GPT-5.1-Codex-Mini when you need to fit long inputs in one request, you need image input, you need built-in web search, you need seed (reproducible sampling), you generate long outputs in one go.
Which is cheaper, Inception: Mercury 2.5 or OpenAI: GPT-5.1-Codex-Mini?
Inception: Mercury 2.5 is cheaper: $0.07 vs $0.69 per 1M tokens at a typical 3:1 input/output mix, 90% less. For 50,000 support conversations a month that is $6.00 against $58.75.
How much do Inception: Mercury 2.5 and OpenAI: GPT-5.1-Codex-Mini cost per million tokens?
Inception: Mercury 2.5 costs $0.04 per 1M input tokens and $0.15 per 1M output tokens; OpenAI: GPT-5.1-Codex-Mini costs $0.25 input and $2.00 output. Output tokens are billed separately, so long answers shift the gap.
Which has the bigger context window, Inception: Mercury 2.5 or OpenAI: GPT-5.1-Codex-Mini?
OpenAI: GPT-5.1-Codex-Mini: 400K tokens, about 600 pages, against 260K (about 390 pages) for Inception: Mercury 2.5.
Do Inception: Mercury 2.5 and OpenAI: GPT-5.1-Codex-Mini support function calling and JSON output?
Tool calling — Inception: Mercury 2.5: yes, OpenAI: GPT-5.1-Codex-Mini: yes. JSON-schema structured output — Inception: Mercury 2.5: yes, OpenAI: GPT-5.1-Codex-Mini: yes.
Can Inception: Mercury 2.5 or OpenAI: GPT-5.1-Codex-Mini read images?
Only OpenAI: GPT-5.1-Codex-Mini accepts image input; Inception: Mercury 2.5 is text-only for input.
Is Inception: Mercury 2.5 or OpenAI: GPT-5.1-Codex-Mini free to use?
No free variant is listed for either; both are pay-per-token.
What is the maximum output length of Inception: Mercury 2.5 and OpenAI: GPT-5.1-Codex-Mini?
Inception: Mercury 2.5 can write up to 66K tokens (about 49,200 words) per response; OpenAI: GPT-5.1-Codex-Mini up to 128K (about 96,000 words).
When were Inception: Mercury 2.5 and OpenAI: GPT-5.1-Codex-Mini released?
Inception: Mercury 2.5 was listed on 2026-09-08; OpenAI: GPT-5.1-Codex-Mini on 2025-11-13.
About the two models
Inception: Mercury 2.5
Mercury 2.5 is the fastest reasoning LLM, and the latest diffusion LLM (dLLM) from Inception. Instead of generating tokens sequentially, Mercury 2.5 produces and refines multiple tokens in parallel, achieving...
Full Inception: Mercury 2.5 specs →OpenAI: GPT-5.1-Codex-Mini
GPT-5.1-Codex-Mini is a smaller and faster version of GPT-5.1-Codex
Full OpenAI: GPT-5.1-Codex-Mini specs →