Model comparison
Grok 4.1 Fast vs LFM2.5-8B-A1B
Head-to-head evidence from 12 shared benchmark results across 5 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
BenchAlign evidence: Grok 4.1 Fast supported; LFM2.5-8B-A1B estimated. Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Grok 4.1 Fast and LFM2.5-8B-A1B share 12 comparable benchmark results. 0 of 8 categories are comparable. 2 results are unique to Grok 4.1 Fast; 6 to LFM2.5-8B-A1B.
Updated July 16, 2026- Shared results
- 12
- Grok 4.1 Fast only
- 2
- LFM2.5-8B-A1B only
- 6
- Comparable categories
- 0 / 8
Benchmark data for Grok 4.1 Fast and LFM2.5-8B-A1B is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 12 shared benchmark results across 5 evidence categories; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
Grok 4.1 Fast is priced at $0.20 input / $0.50 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for LFM2.5-8B-A1B. Grok 4.1 Fast has the larger context window at 1M, compared with 128K for LFM2.5-8B-A1B.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | Grok 4.1 Fast | Δ | LFM2.5-8B-A1B |
|---|---|---|---|
| Math | Grok 4.1 FastNot measured | MarginNo overlap | LFM2.5-8B-A1B50.0 |
| Inst. Following | Grok 4.1 FastNot measured | MarginNo overlap | LFM2.5-8B-A1B68.8 |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Grok 4.1 Fast | LFM2.5-8B-A1B | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Grok 4.1 Fast$0.2 input / $0.5 output | LFM2.5-8B-A1B$0 input / $0 output | LFM2.5-8B-A1B has the lower combined listed price. |
| Generation speedtokens per second | Grok 4.1 Fast138 tok/s | LFM2.5-8B-A1BNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Grok 4.1 Fast0.54 s | LFM2.5-8B-A1BNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Grok 4.1 Fast1M | LFM2.5-8B-A1B128K | Grok 4.1 Fast lists the larger context window. |
Benchmark Deep Dive
Agentic3 benchmarks
Coding2 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | Grok 4.1 Fast | LFM2.5-8B-A1B | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 16.9% | 8.3% | Grok 4.1 Fast leads |
| AA-GPQA DiamondSource | 63.7% | 51.3% | Grok 4.1 Fast leads |
| AA-HLESource | 5.0% | 6.9% | LFM2.5-8B-A1B leads |
| AA-Omniscience IndexSource | -50.9% | -33.3% | LFM2.5-8B-A1B leads |
| AA-Omniscience AccuracySource | 17.0% | 9.4% | Grok 4.1 Fast leads |
| AA-Omniscience Hallucination RateSource | 81.8% | 47.0% | LFM2.5-8B-A1B leads |
Math3 benchmarks
Multimodal1 benchmarks
| Benchmark | Grok 4.1 Fast | LFM2.5-8B-A1B | Result |
|---|---|---|---|
| AA-MMMU-ProSource | 48.4% | — | Not comparable |
Frequently Asked Questions (3)
Can I compare Grok 4.1 Fast and LFM2.5-8B-A1B on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
What data is available for Grok 4.1 Fast and LFM2.5-8B-A1B today?
Grok 4.1 Fast: $0.20 input / $0.50 output per 1M tokens LFM2.5-8B-A1B: $0.00 input / $0.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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