GPT-5.4 vs Phi 3.5 Mini Instruct
GPT-5.4 (2026) and Phi 3.5 Mini Instruct (2024) are frontier reasoning models from OpenAI and Microsoft Research. GPT-5.4 ships a 1.05m-token context window, while Phi 3.5 Mini Instruct ships a 128k-token context window. On pricing, GPT-5.4 ranges from $2.50 to $5/1M input tokens by tier; Phi 3.5 Mini Instruct costs $0.90/1M 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-5.4 fits 8x more tokens; pick it for long-context work and Phi 3.5 Mini Instruct for tighter calls.
Decision scorecard
Local evidence first| Signal | GPT-5.4 | Phi 3.5 Mini Instruct |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | provider-routed production |
| Decision fit | Coding, RAG, and Agents | Long context |
| Context window | 1.05m | 128k |
| Cheapest output | $15/1M tokens | $0.90/1M tokens |
| Provider routes | 4 tracked | 2 tracked |
| Shared benchmarks | 0 shared | 0 shared |
Decision tradeoffs
- GPT-5.4 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.4 has broader tracked provider coverage for fallback and route flexibility.
- GPT-5.4 uniquely exposes Vision, Multimodal, and Reasoning in local model data.
- Local decision data tags GPT-5.4 for Coding, RAG, and Agents.
- Phi 3.5 Mini Instruct has the lower cheapest tracked output price at $0.90/1M tokens.
- Local decision data tags Phi 3.5 Mini 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-5.4
$5,750
Cheapest tracked route/tier: OpenAI API
Phi 3.5 Mini Instruct
$945
Cheapest tracked route/tier: Fireworks AI
Estimated monthly gap: $4,805. 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-5.4 and Phi 3.5 Mini Instruct; plan for SDK, billing, or endpoint changes.
- Phi 3.5 Mini Instruct is $14.10/1M 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 Mini Instruct and GPT-5.4; plan for SDK, billing, or endpoint changes.
- GPT-5.4 is $14.10/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.4 adds Vision, Multimodal, and Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-03-05 | 2024-08-20 |
| Context window | 1.05m | 128k |
| Parameters | — | 3.8B |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | MITOSI-approved |
| Openness | Proprietary | Open source |
| Weights | Not released | Unknown |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: permitted |
| Knowledge cutoff | 2025-08 | 2023-10 |
Pricing and availability
| Pricing attribute | GPT-5.4 | Phi 3.5 Mini Instruct |
|---|---|---|
| Input price |
| $0.90/1M tokens |
| Output price |
| $0.90/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.4 | Phi 3.5 Mini Instruct |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | No |
| Reasoning | Yes | No |
| JSON / 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 scores are currently available for this pair.
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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.