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Mercury 3 vs Step-3.5-Flash

Mercury 3 and Step-3.5-Flash are closely matched at 36.1 and 36.8 on the LLM Stats Score. Mercury 3 is 1.1x cheaper per token.

Inception · StepFun · Updated for 2026

Which is better?

Mercury 3 and Step-3.5-Flash are closely matched on the overall LLM Stats Score at 36.1 and 36.8.

On price, Mercury 3 is roughly 1.1x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Mercury 3 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Mercury 3

  • cost matters — it's about 1.1x cheaper per token
  • you process long inputs — it offers a 1,000,000 token context window
  • you want the most recent training data — it shipped Oct 2026

Choose Step-3.5-Flash

  • you need open weights you can self-host or fine-tune

At a glance

The differences that matter most.

Mercury 3
Inception
Step-3.5-Flash
StepFun
Core performance indexes
LLM Stats Score
36.1
#98
36.8
#90
Reasoning
34.8
#103
36.9
#89
Coding
21.5
#105
20.4
#115
Agents
19.4
#84
15.3
#108
Cost, coverage & limits
Benchmark wins
—
—
Input price
$0.10 / M
$0.10 / M
Output price
$0.35 / M
$0.40 / M
Context window
1,000,000
65,536

Individual benchmarks

12 reported for Mercury 3 · 7 for Step-3.5-Flash

No common benchmarks found

Mercury 3 and Step-3.5-Flashdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

Mercury 3 costs less

For input processing, Mercury 3 ($0.10/1M tokens) costs the same as Step-3.5-Flash ($0.10/1M tokens).

For output processing, Mercury 3 ($0.35/1M tokens) is 1.1x cheaper than Step-3.5-Flash ($0.40/1M tokens).

In conclusion, Step-3.5-Flash is more expensive than Mercury 3.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Fri Oct 23 2026 • llm-stats.com
Inception
Mercury 3
Input tokens$0.10
Output tokens$0.35
Best providerInception
StepFun
Step-3.5-Flash
Input tokens$0.10
Output tokens$0.40
Best providerStepFun
Notice missing or incorrect data?

Context Window

Maximum input and output token capacity

Mercury 3 accepts 1,000,000 input tokens compared to Step-3.5-Flash's 65,536 tokens. Mercury 3 can generate longer responses up to 131,072 tokens, while Step-3.5-Flash is limited to 8,192 tokens.

Inception
Mercury 3
Input1,000,000 tokens
Output131,072 tokens
StepFun
Step-3.5-Flash
Input65,536 tokens
Output8,192 tokens
Fri Oct 23 2026 • llm-stats.com

License

Usage and distribution terms

Mercury 3 is licensed under a proprietary license, while Step-3.5-Flash uses Apache 2.0.

License differences may affect how you can use these models in commercial or open-source projects.

Mercury 3

Proprietary

Closed source

Step-3.5-Flash

Apache 2.0

Open weights

Release Timeline

When each model was launched

Mercury 3 was released on 2026-10-19, while Step-3.5-Flash was released on 2026-02-02.

Mercury 3 is 9 months newer than Step-3.5-Flash.

Mercury 3

Oct 19, 2026

0 days ago

8mo newer
Step-3.5-Flash

Feb 2, 2026

8 months ago

Knowledge Cutoff

When training data ends

Neither model specifies a knowledge cutoff date.

Unable to compare the recency of their training data.

No cutoff dates available

Provider Availability

Mercury 3 is available from Inception. Step-3.5-Flash is available from StepFun.

Mercury 3

inception logo
Inception
Input Price:Input: $0.10/1MOutput Price:Output: $0.35/1M

Step-3.5-Flash

stepfun logo
StepFun
Input Price:Input: $0.10/1MOutput Price:Output: $0.40/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

Run your own prompts against Mercury 3 and Step-3.5-Flash side-by-side, then vote on the output you prefer.

Mercury 3
✓ Preferred
Step-3.5-Flash
Open in Playground

FAQ

Common questions about Mercury 3 vs Step-3.5-Flash.

Which is better, Mercury 3 or Step-3.5-Flash?

Mercury 3 and Step-3.5-Flash are closely matched on the LLM Stats Score at 36.1 and 36.8. Mercury 3 is made by Inception and Step-3.5-Flash is made by StepFun. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Mercury 3 compare to Step-3.5-Flash in benchmarks?

Mercury 3 scores GPQA: 89.2%, AA-LCR: 77.7%, IFBench: 76.8%, MRCR v2: 75.5%, DeepSearchQA: 71.3%. Step-3.5-Flash scores AIME 2025: 97.3%, Tau-bench: 88.2%, LiveCodeBench v6: 86.4%, IMO-AnswerBench: 85.4%, SWE-Bench Verified: 74.4%.

Is Mercury 3 cheaper than Step-3.5-Flash?

Both models cost $0.10 per million input tokens.

What are the context window sizes for Mercury 3 and Step-3.5-Flash?

Mercury 3 supports 1.0M tokens and Step-3.5-Flash supports 66K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Mercury 3 and Step-3.5-Flash?

Key differences include LLM Stats Score (36.1 vs 36.8), context window (1.0M vs 66K), licensing (Proprietary vs Apache 2.0). See the full comparison above for benchmark-by-benchmark results.

Who makes Mercury 3 and Step-3.5-Flash?

Mercury 3 is developed by Inception and Step-3.5-Flash is developed by StepFun.

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