GPT-5.5 vs Phi 3.5 MoE Instruct
GPT-5.5 (2026) and Phi 3.5 MoE Instruct (2024) are frontier reasoning models from OpenAI and Microsoft Research. GPT-5.5 ships a 1.05m-token context window, while Phi 3.5 MoE Instruct ships a 128k-token context window. On pricing, GPT-5.5 ranges from $5 to $8/1M input tokens by tier; Phi 3.5 MoE Instruct costs $0.50/1M input tokens. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
GPT-5.5 fits 8x more tokens; pick it for long-context work and Phi 3.5 MoE Instruct for tighter calls.
Decision scorecard
Local evidence first| Signal | GPT-5.5 | Phi 3.5 MoE Instruct |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | general production evaluation |
| Decision fit | Coding, RAG, and Agents | Long context |
| Context window | 1.05m | 128k |
| Cheapest output | $30/1M tokens | $0.50/1M tokens |
| Provider routes | 3 tracked | 1 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- GPT-5.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 has broader tracked provider coverage for fallback and procurement flexibility.
- GPT-5.5 uniquely exposes Vision, Multimodal, and Reasoning in local model data.
- Local decision data tags GPT-5.5 for Coding, RAG, and Agents.
- Phi 3.5 MoE Instruct has the lower cheapest tracked output price at $0.50/1M tokens.
- Local decision data tags Phi 3.5 MoE Instruct for Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
GPT-5.5
$11,500
Cheapest tracked route/tier: OpenAI API 0-272K input tokens
Phi 3.5 MoE Instruct
$525
Cheapest tracked route/tier: Fireworks AI
Estimated monthly gap: $10,975. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for GPT-5.5 and Phi 3.5 MoE Instruct; plan for SDK, billing, or endpoint changes.
- Phi 3.5 MoE Instruct is $29.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Vision, Multimodal, and Reasoning before moving production traffic.
- No overlapping tracked provider route is sourced for Phi 3.5 MoE Instruct and GPT-5.5; plan for SDK, billing, or endpoint changes.
- GPT-5.5 is $29.50/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.5 adds Vision, Multimodal, and Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-23 | 2024-08-20 |
| Context window | 1.05m | 128k |
| Parameters | — | 16x3.8B (42B, 6.6B active) |
| Architecture | decoder only | decoder only |
| License | Proprietary | MIT(OSI) |
| Openness | Proprietary | Open source |
| Commercial use | Commercial use with conditions | Commercial use allowed |
| Knowledge cutoff | 2025-12 | 2023-10 |
Pricing and availability
| Pricing attribute | GPT-5.5 | Phi 3.5 MoE Instruct |
|---|---|---|
| Input price |
| $0.50/1M tokens |
| Output price |
| $0.50/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.5 | Phi 3.5 MoE Instruct |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | No |
| 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
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on vision: GPT-5.5, multimodal input: GPT-5.5, reasoning mode: GPT-5.5, function calling: GPT-5.5, tool use: GPT-5.5, structured outputs: GPT-5.5, and code execution: GPT-5.5. 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, GPT-5.5 lists tiered pricing: 0-272K input tokens is $5/1M input and $30/1M output; 272K+ input tokens is $8/1M input and $36/1M output, while Phi 3.5 MoE Instruct lists $0.50/1M input and $0.50/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Phi 3.5 MoE Instruct lower by about $12 per million blended tokens. For tiered rows, this cheapest-track view can understate interactive or fast-lane spend, so compare the tier you will actually use. Availability is 3 providers versus 1, so concentration risk also matters.
Choose GPT-5.5 when coding workflow support, larger context windows, and broader provider choice are central to the workload. Choose Phi 3.5 MoE Instruct when provider fit 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.
FAQ
Which has a larger context window, GPT-5.5 or Phi 3.5 MoE Instruct?
GPT-5.5 supports 1.05m tokens, while Phi 3.5 MoE Instruct supports 128k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, GPT-5.5 or Phi 3.5 MoE Instruct?
GPT-5.5 lists tiered pricing: 0-272K input tokens is $5/1M input and $30/1M output; 272K+ input tokens is $8/1M input and $36/1M output. Phi 3.5 MoE Instruct lists $0.50/1M input and $0.50/1M output tokens on the cheapest tracked provider. Compare the tier you will actually use; cheap async pricing can overstate savings for interactive workflows. Provider discounts or batch pricing can still change the final bill.
Is GPT-5.5 or Phi 3.5 MoE Instruct open source?
GPT-5.5 is listed under Proprietary. Phi 3.5 MoE Instruct is listed under MIT. 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, GPT-5.5 or Phi 3.5 MoE Instruct?
GPT-5.5 has the clearer documented vision signal in this comparison. If vision is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, GPT-5.5 or Phi 3.5 MoE Instruct?
GPT-5.5 has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run GPT-5.5 and Phi 3.5 MoE Instruct?
GPT-5.5 is available on OpenAI API, OpenRouter, and Vercel AI Gateway. Phi 3.5 MoE Instruct is available on Fireworks AI. 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.