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Providers

Amazon Anthropic Cohere DeepSeek Google MiniMax Mistral Moonshot AI OpenAI Qwen xAI Xiaomi MiMo Z.ai

Providers

Amazon 8 Anthropic 31 Cohere 35 DeepSeek 5 Google 34 MiniMax 17 Mistral 53 Moonshot AI 18 OpenAI 106 Qwen 26 xAI 26 Xiaomi MiMo 4 Z.ai 22
xAI grok-4-1-fast-reasoning

Grok 4.1 Fast Reasoning (xAI)

Retired

Yes — Grok 4.1 Fast Reasoning is retired. xAI shut it down on May 15, 2026; API requests to it now fail. The recommended replacement is Grok 4.3.

A 2M-context reasoning model that was, for a few months, the cheapest way to put a long document in front of a frontier model. It retired on 15 May 2026, and the slug still resolves - requests are silently served by grok-4.3 at grok-4.3 prices, which is the trap in this whole retirement wave.

The facts

Provider xAI
Model id grok-4-1-fast-reasoning
Released —
Deprecated date not published
Shutdown May 15, 2026 · 80 days ago
Status Retired
Last verified August 3, 2026

What to use instead

xAI Grok 4.3 grok-4.3 Provider-recommended Active

xAI maps this id to grok-4.3 with reasoning effort "low". The slug keeps working, so nothing breaks - but you are billed $1.25/$2.50 per million instead of the old rate, and the context window drops from 2M to 1M.

What parameters grok-4.3 accepts on modelparams.dev

Change the id

In most cases the migration is one string. Check the parameter differences before you ship — newer models drop older sampling knobs more often than they add them. 

- "model": "grok-4-1-fast-reasoning"
+ "model": "grok-4.3"

Frequently asked questions

When did xAI Grok 4.1 Fast Reasoning shut down?
xAI Grok 4.1 Fast Reasoning shut down on May 15, 2026. API requests to it fail from that date onward.
What replaces xAI Grok 4.1 Fast Reasoning?
xAI recommends Grok 4.3 (`grok-4.3`) as the replacement for xAI Grok 4.1 Fast Reasoning. xAI maps this id to grok-4.3 with reasoning effort "low". The slug keeps working, so nothing breaks - but you are billed $1.25/$2.50 per million instead of the old rate, and the context window drops from 2M to 1M.
Is xAI Grok 4.1 Fast Reasoning still available?
No. xAI Grok 4.1 Fast Reasoning is retired and no longer served — it was shut down on May 15, 2026. Calls to it return an error.
How do I migrate from xAI Grok 4.1 Fast Reasoning to grok-4.3?
Swap the model id in your API call: replace "grok-4-1-fast-reasoning" with "grok-4.3". xAI maps this id to grok-4.3 with reasoning effort "low". The slug keeps working, so nothing breaks - but you are billed $1.25/$2.50 per million instead of the old rate, and the context window drops from 2M to 1M.

Sources

Found something wrong? The data is one YAML file — edit it on GitHub.

This page, for machines

JSON Markdown Badge JSON

Drop the badge in a README so it turns red the day this model is retired:

[![grok-4-1-fast-reasoning](https://img.shields.io/endpoint?url=https://modeldeprecations.dev/badge/xai/grok-4-1-fast-reasoning.json)](https://modeldeprecations.dev/xai/grok-4-1-fast-reasoning)

Other xAI models

All xAI deprecations →

How to use this site

The full guide, in Markdown. Copy it and hand it to a coding agent verbatim.

# How to use modeldeprecations.dev

[modeldeprecations.dev](https://modeldeprecations.dev) answers one question per model: is it deprecated,
when does it shut down, and what replaces it. Every date on the site is cited to the
provider's own documentation, with the date we last checked it.

Three lifecycle states are used, matching the providers' own vocabulary:

- **active** — still supported, no deprecation announced.
- **deprecated** — the provider has announced it is going away. It still answers requests.
- **retired** — API access is gone. Requests fail.

A model can be active *and* carry a shutdown date: Anthropic publishes a
"not sooner than" date and Google publishes an earliest shutdown date for models
that are current and fully supported. Those are reported as scheduled shutdowns,
not deprecations, because that is what the provider actually committed to.

## Check one model

```bash
curl https://modeldeprecations.dev/api/v1/models/openai/gpt-4-32k.json
```

Or fetch the page as Markdown, which includes the answer, the dates and the sources:

```bash
curl https://modeldeprecations.dev/openai/gpt-4-32k.md
```

## Full catalog

```bash
curl https://modeldeprecations.dev/api/v1/models.json
```

Ids are `provider/model`. Dated snapshots (`gpt-4-32k-0613`) are listed as aliases of
their canonical entry rather than as separate records.

Each entry carries `computed_status`, the lifecycle state recomputed against the build
date — so a model whose shutdown has passed reads `retired` without anyone editing data.

## Badges

A shields.io endpoint per model, for READMEs that should go red when a model dies:

```
https://img.shields.io/endpoint?url=https://modeldeprecations.dev/badge/openai/gpt-4-32k.json
```

## Calendar and changelog

- Subscribe to every shutdown date: https://modeldeprecations.dev/calendar.ics
- Changelog RSS: https://modeldeprecations.dev/changelog.xml

## JSON Schema

```bash
curl https://modeldeprecations.dev/api/v1/schema.json
```

## Contribute

Data lives in YAML under `models/{provider}/{model}.yaml` in the
[GitHub repo](https://github.com/mnfst/modeldeprecations.dev). Every lifecycle date needs a source URL; CI rejects a
date without one. Open a PR.

## For agents

- Machine-readable overview: https://modeldeprecations.dev/llms.txt
- This guide plus every model inline: https://modeldeprecations.dev/llms-full.txt
- Any page also exists as Markdown: append `.md` to a model URL.
- In a browser, this site registers a **WebMCP** tool on `navigator.modelContext`:
  `check_model_deprecation`, `list_shutdowns`, `find_replacement`, and `get_usage_guide`.
- Parameters each model accepts are catalogued on the sibling site, https://modelparams.dev.