o3 vs Qwen3.5-4B
o3 (2025) and Qwen3.5-4B (2026) are frontier reasoning models from OpenAI and Alibaba. o3 ships a 200k-token context window, while Qwen3.5-4B ships a 262k-token context window. On Google-Proof Q&A, o3 leads by 11.5 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads. It focuses on practical selection signals rather than broad model-family marketing.
Qwen3.5-4B is safer overall; choose o3 when coding workflow support matters.
Decision scorecard
Local evidence first| Signal | o3 | Qwen3.5-4B |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | multimodal apps |
| Decision fit | Coding, RAG, and Agents | Coding, Agents, and Long context |
| Context window | 200k | 262k |
| Cheapest output | $8/1M tokens | - |
| Provider routes | 3 tracked | 0 tracked |
| Shared benchmarks | Google-Proof Q&A leader | 2 rows |
Decision tradeoffs
- o3 holds a shared-benchmark lead on Google-Proof Q&A, ahead by 11.5 points.
- o3 has broader tracked provider coverage for fallback and procurement flexibility.
- o3 uniquely exposes Reasoning, Function calling, and Tool use in local model data.
- Local decision data tags o3 for Coding, RAG, and Agents.
- Qwen3.5-4B has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Local decision data tags Qwen3.5-4B for Coding, Agents, and Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
o3
$3,600
Cheapest tracked route/tier: OpenAI API
Qwen3.5-4B
Unavailable
No complete token price in local provider data
Cost delta unavailable until both models have sourced input and output token prices.
Switch friction
- No overlapping tracked provider route is sourced for o3 and Qwen3.5-4B; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Reasoning, Function calling, and Tool use before moving production traffic.
- No overlapping tracked provider route is sourced for Qwen3.5-4B and o3; plan for SDK, billing, or endpoint changes.
- o3 adds Reasoning, Function calling, and Tool use in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-04-16 | 2026-03-02 |
| Context window | 200k | 262k |
| Parameters | — | 4B |
| Architecture | decoder only | - |
| License | Proprietary | Apache 2.0(OSI) |
| Openness | Proprietary | Open source |
| Commercial use | Commercial use with conditions | Commercial use allowed |
| Knowledge cutoff | 2024-06 | - |
Pricing and availability
| Pricing attribute | o3 | Qwen3.5-4B |
|---|---|---|
| Input price | $2/1M tokens | - |
| Output price | $8/1M tokens | - |
| Providers | - |
Capabilities
| Capability | o3 | Qwen3.5-4B |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | No |
| Function calling | Yes | No |
| Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | o3 | Qwen3.5-4B |
|---|---|---|
| Google-Proof Q&A | 87.7 | 76.2 |
| LiveCodeBench | 85.5 | 55.8 |
Deep dive
On shared benchmark coverage, Google-Proof Q&A has o3 at 87.7 and Qwen3.5-4B at 76.2, with o3 ahead by 11.5 points; LiveCodeBench has o3 at 85.5 and Qwen3.5-4B at 55.8, with o3 ahead by 29.7 points. The largest visible gap is 29.7 points on LiveCodeBench, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on reasoning mode: o3, function calling: o3, tool use: o3, structured outputs: o3, and code execution: o3. Both models share vision and multimodal input, 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.
Pricing coverage is uneven: o3 has $2/1M input tokens and Qwen3.5-4B has no token price sourced yet. Provider availability is 3 tracked routes versus 0. Treat unknown pricing as an integration gap, then verify the route you will actually call before estimating production spend.
Choose o3 when coding workflow support and broader provider choice are central to the workload. Choose Qwen3.5-4B when long-context analysis and larger context windows are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, o3 or Qwen3.5-4B?
Qwen3.5-4B supports 262k tokens, while o3 supports 200k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Is o3 or Qwen3.5-4B open source?
o3 is listed under Proprietary. Qwen3.5-4B is listed under Apache 2.0. 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 vision, o3 or Qwen3.5-4B?
Both o3 and Qwen3.5-4B expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, o3 or Qwen3.5-4B?
Both o3 and Qwen3.5-4B expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for reasoning mode, o3 or Qwen3.5-4B?
o3 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.
Where can I run o3 and Qwen3.5-4B?
o3 is available on OpenAI API, OpenRouter, and Vercel AI Gateway. Qwen3.5-4B is available on the tracked providers still being sourced. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-06-08. Data sourced from public model cards and provider documentation.