Gemini 2.5 Pro Preview 05-06 vs Step 3.5 Flash
Gemini 2.5 Pro Preview 05-06 (2025) and Step 3.5 Flash (2026) are frontier reasoning models from Google DeepMind and StepFun. Gemini 2.5 Pro Preview 05-06 ships a 1m-token context window, while Step 3.5 Flash ships a 256k-token context window. On pricing, Step 3.5 Flash costs $0.10/1M input tokens versus $1.25/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Step 3.5 Flash is ~1150% cheaper at $0.10/1M; pay for Gemini 2.5 Pro Preview 05-06 only for long-context analysis.
Decision scorecard
Local evidence first| Signal | Gemini 2.5 Pro Preview 05-06 | Step 3.5 Flash |
|---|---|---|
| Best for | long-context analysis | reasoning-heavy apps |
| Decision fit | RAG, Long context, and Vision | Long context |
| Context window | 1m | 256k |
| Cheapest output | $10/1M tokens | $0.30/1M tokens |
| Provider routes | 1 tracked | 1 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Gemini 2.5 Pro Preview 05-06 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Gemini 2.5 Pro Preview 05-06 uniquely exposes Structured outputs in local model data.
- Local decision data tags Gemini 2.5 Pro Preview 05-06 for RAG, Long context, and Vision.
- Step 3.5 Flash has the lower cheapest tracked output price at $0.30/1M tokens.
- Step 3.5 Flash uniquely exposes Reasoning in local model data.
- Local decision data tags Step 3.5 Flash for Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Gemini 2.5 Pro Preview 05-06
$3,500
Cheapest tracked route/tier: OpenRouter
Step 3.5 Flash
$155
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $3,345. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Step 3.5 Flash is $9.70/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Structured outputs before moving production traffic.
- Step 3.5 Flash adds Reasoning in local capability data.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Gemini 2.5 Pro Preview 05-06 is $9.70/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Reasoning before moving production traffic.
- Gemini 2.5 Pro Preview 05-06 adds Structured outputs in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-05-06 | 2026-01-29 |
| Context window | 1m | 256k |
| Parameters | — | 196B (11B active) |
| Architecture | decoder only | mixture of experts |
| License | Unknown | Open Source |
| Knowledge cutoff | 2025-01 | - |
Pricing and availability
| Pricing attribute | Gemini 2.5 Pro Preview 05-06 | Step 3.5 Flash |
|---|---|---|
| Input price | $1.25/1M tokens | $0.10/1M tokens |
| Output price | $10/1M tokens | $0.30/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 2.5 Pro Preview 05-06 | Step 3.5 Flash |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | No | Yes |
| Function calling | No | No |
| Tool use | No | No |
| Structured outputs | Yes | No |
| Code execution | No | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on reasoning mode: Step 3.5 Flash and structured outputs: Gemini 2.5 Pro Preview 05-06. Both models share the core language-model surface, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Gemini 2.5 Pro Preview 05-06 lists $1.25/1M input and $10/1M output tokens on the cheapest tracked provider, while Step 3.5 Flash lists $0.10/1M input and $0.30/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Step 3.5 Flash lower by about $3.71 per million blended tokens. Availability is 1 providers versus 1, so concentration risk also matters.
Choose Gemini 2.5 Pro Preview 05-06 when long-context analysis and larger context windows are central to the workload. Choose Step 3.5 Flash when reasoning depth and lower input-token cost are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions.
FAQ
Which has a larger context window, Gemini 2.5 Pro Preview 05-06 or Step 3.5 Flash?
Gemini 2.5 Pro Preview 05-06 supports 1m tokens, while Step 3.5 Flash supports 256k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Gemini 2.5 Pro Preview 05-06 or Step 3.5 Flash?
Step 3.5 Flash is cheaper on tracked token pricing. Gemini 2.5 Pro Preview 05-06 costs $1.25/1M input and $10/1M output tokens. Step 3.5 Flash costs $0.10/1M input and $0.30/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Gemini 2.5 Pro Preview 05-06 or Step 3.5 Flash open source?
Gemini 2.5 Pro Preview 05-06 is listed under Unknown. Step 3.5 Flash is listed under Open Source. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for reasoning mode, Gemini 2.5 Pro Preview 05-06 or Step 3.5 Flash?
Step 3.5 Flash has the clearer documented reasoning mode signal in this comparison. If reasoning mode is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for structured outputs, Gemini 2.5 Pro Preview 05-06 or Step 3.5 Flash?
Gemini 2.5 Pro Preview 05-06 has the clearer documented structured outputs signal in this comparison. If structured outputs is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Gemini 2.5 Pro Preview 05-06 and Step 3.5 Flash?
Gemini 2.5 Pro Preview 05-06 is available on OpenRouter. Step 3.5 Flash is available on OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Continue comparing
Last reviewed: 2026-05-29. Data sourced from public model cards and provider documentation.