OpenAI o3 (Reasoning Model) vsGrok 4.1 Fast Reasoning (xAI)
Compare the listed model data for OpenAI o3 (Reasoning Model) by OpenAI and Grok 4.1 Fast Reasoning (xAI) by xAI. Benchmark and pricing records are not a controlled test and may change.
Data last updated: 2026-10-16. Verify current model details with each provider.
What the listed data says
OpenAI o3 (Reasoning Model): 128K tokens; Grok 4.1 Fast Reasoning (xAI): 2M tokens. Grok 4.1 Fast Reasoning (xAI) has the larger listed context window. OpenAI o3 (Reasoning Model) is listed for coding, reasoning, vision, multimodal input, agentic workflows, long-context tasks; Grok 4.1 Fast Reasoning (xAI) is listed for coding, reasoning, vision, multimodal input, agentic workflows, long-context tasks. Shared catalog benchmark entries: AIME 2025: OpenAI o3 (Reasoning Model) 96.7%; Grok 4.1 Fast Reasoning (xAI) 93.2%; GPQA Diamond: OpenAI o3 (Reasoning Model) 87.7%; Grok 4.1 Fast Reasoning (xAI) 84.1%; HumanEval: OpenAI o3 (Reasoning Model) 99.2%; Grok 4.1 Fast Reasoning (xAI) 96.4%. These records are reference data, not a controlled head-to-head test; verify current pricing and specifications with each provider.
Catalog source links
Use these model and provider links to verify current specifications, pricing, and availability.
The listed context windows are 128K tokens and 2M tokens; the larger is 15.63× the smaller.
On shared numeric benchmark entries, AIME 2025: OpenAI o3 (Reasoning Model) − Grok 4.1 Fast Reasoning (xAI) = +3.5 percentage points (96.7% vs 93.2%); GPQA Diamond: OpenAI o3 (Reasoning Model) − Grok 4.1 Fast Reasoning (xAI) = +3.6 percentage points (87.7% vs 84.1%); HumanEval: OpenAI o3 (Reasoning Model) − Grok 4.1 Fast Reasoning (xAI) = +2.8 percentage points (99.2% vs 96.4%).
The first listed parameter quantities are ~200B+ (frontier reasoning, exact size proprietary) and ~314B MoE (2M context, exact active params proprietary); the larger quantity is 1.57× the smaller. Total and active MoE parameters are not directly equivalent.
A release-date gap cannot be calculated from the catalog values (OpenAI o3 (Reasoning Model): 2025; Grok 4.1 Fast Reasoning (xAI): 2025).
Cost example: 1M input and 1M output tokens
A cost example for 1M input plus 1M output tokens cannot be calculated reliably because separate numeric input and output rates are not listed for both models.
Choose OpenAI o3 (Reasoning Model) if…
Choose OpenAI o3 (Reasoning Model) when your task aligns with catalog-listed uses or strengths such as Competition and graduate-level mathematics (AIME, Olympiad problems), Advanced scientific research: physics, chemistry, biology problem solving, Complex software engineering requiring full architectural reasoning, PhD-level research questions in STEM fields.
Choose Grok 4.1 Fast Reasoning (xAI) if…
Choose Grok 4.1 Fast Reasoning (xAI) when your task aligns with catalog-listed uses or strengths such as Ultra-long document analysis requiring 1M+ token context (books, legal archives, codebases), Real-time research requiring current news and social media data from X, Financial analysis of quarterly reports, 10-Ks, and multi-year filings in one session, Rapid complex reasoning tasks where full o3-style thinking is too slow.
~314B MoE (2M context, exact active params proprietary)
Context window
128K tokens
2M tokens
Maximum output
Not listed
Not listed
Catalog pricing
Via LITHOVEX AI free. OpenAI API: premium pricing.
Via LITHOVEX AI free.
Listed input/output cost per 1M tokens
Separate numeric input/output rates not listed
Separate numeric input/output rates not listed
License
Proprietary
Proprietary
Coding support
Listed
Listed
Reasoning support
Listed
Listed
Vision input
Listed
Listed
Multimodal
Listed
Listed
Open weights
No
No
Benchmark: AIME 2025
96.7%
93.2%
Benchmark: GPQA Diamond
87.7%
84.1%
Benchmark: HumanEval
99.2%
96.4%
Figures are transcribed from LITHOVEX model records. Benchmark versions and evaluation setups may differ; pricing and specifications can change. Check each provider's current documentation before making a decision.
Frequently Asked Questions
What is different between OpenAI o3 (Reasoning Model) and Grok 4.1 Fast Reasoning (xAI)?
OpenAI o3 (Reasoning Model): 128K tokens; Grok 4.1 Fast Reasoning (xAI): 2M tokens. Grok 4.1 Fast Reasoning (xAI) has the larger listed context window. OpenAI o3 (Reasoning Model) is listed for coding, reasoning, vision, multimodal input, agentic workflows, long-context tasks; Grok 4.1 Fast Reasoning (xAI) is listed for coding, reasoning, vision, multimodal input, agentic workflows, long-context tasks. Shared catalog benchmark entries: AIME 2025: OpenAI o3 (Reasoning Model) 96.7%; Grok 4.1 Fast Reasoning (xAI) 93.2%; GPQA Diamond: OpenAI o3 (Reasoning Model) 87.7%; Grok 4.1 Fast Reasoning (xAI) 84.1%; HumanEval: OpenAI o3 (Reasoning Model) 99.2%; Grok 4.1 Fast Reasoning (xAI) 96.4%. These records are reference data, not a controlled head-to-head test; verify current pricing and specifications with each provider.
What benchmark values are listed for OpenAI o3 (Reasoning Model) and Grok 4.1 Fast Reasoning (xAI)?
AIME 2025: OpenAI o3 (Reasoning Model) 96.7%; Grok 4.1 Fast Reasoning (xAI) 93.2%; GPQA Diamond: OpenAI o3 (Reasoning Model) 87.7%; Grok 4.1 Fast Reasoning (xAI) 84.1%; HumanEval: OpenAI o3 (Reasoning Model) 99.2%; Grok 4.1 Fast Reasoning (xAI) 96.4%. The catalog values may use different versions and evaluation setups, so they are reference points rather than a controlled head-to-head result.
Which model has the larger listed context window?
OpenAI o3 (Reasoning Model): 128K tokens; Grok 4.1 Fast Reasoning (xAI): 2M tokens. Grok 4.1 Fast Reasoning (xAI) has the larger listed context window.
What are the listed costs per million tokens for OpenAI o3 (Reasoning Model) and Grok 4.1 Fast Reasoning (xAI)?
OpenAI o3 (Reasoning Model): Separate numeric input/output rates not listed (Via LITHOVEX AI free. OpenAI API: premium pricing.). Grok 4.1 Fast Reasoning (xAI): Separate numeric input/output rates not listed (Via LITHOVEX AI free.). Where separate numeric input and output rates are available, the worked example uses 1M input plus 1M output tokens. Confirm current terms with each provider.
How far apart are the listed release dates for OpenAI o3 (Reasoning Model) and Grok 4.1 Fast Reasoning (xAI)?
The catalog lists OpenAI o3 (Reasoning Model) as 2025 and Grok 4.1 Fast Reasoning (xAI) as 2025; a release-date gap cannot be calculated from both records.
When was the comparison data last updated?
The model catalog records 2026-10-16 as its data update date. Provider specifications and prices may have changed since then.
How should I choose between OpenAI o3 (Reasoning Model) and Grok 4.1 Fast Reasoning (xAI)?
Compare the listed specifications and capabilities, review the benchmark notes, then test both with the same representative prompt for your task. This page does not claim a universal winner.
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