Grok 4.3 vs Phi 3.5 Mini Instruct
Grok 4.3 (2026) and Phi 3.5 Mini Instruct (2024) are frontier reasoning models from xAI and Microsoft Research. Grok 4.3 ships a 1m-token context window, while Phi 3.5 Mini Instruct ships a 128k-token context window. On pricing, Grok 4.3 ranges from $1.25 to $2.50/1M 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.
Grok 4.3 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 | Grok 4.3 | Phi 3.5 Mini Instruct |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | provider-routed production |
| Decision fit | RAG, Agents, and Long context | Long context |
| Context window | 1m | 128k |
| Cheapest output | $2.50/1M tokens | $0.90/1M tokens |
| Provider routes | 4 tracked | 2 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Grok 4.3 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Grok 4.3 has broader tracked provider coverage for fallback and procurement flexibility.
- Grok 4.3 uniquely exposes Vision, Multimodal, and Reasoning in local model data.
- Local decision data tags Grok 4.3 for RAG, Agents, and Long context.
- 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.
Grok 4.3
$1,625
Cheapest tracked route/tier: xAI Console
Phi 3.5 Mini Instruct
$945
Cheapest tracked route/tier: Fireworks AI
Estimated monthly gap: $680. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Grok 4.3 and Phi 3.5 Mini Instruct; plan for SDK, billing, or endpoint changes.
- Phi 3.5 Mini Instruct is $1.60/1M 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 Grok 4.3; plan for SDK, billing, or endpoint changes.
- Grok 4.3 is $1.60/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Grok 4.3 adds Vision, Multimodal, and Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-06 | 2024-08-20 |
| Context window | 1m | 128k |
| Parameters | ~0.5T | 3.8B |
| Architecture | - | decoder only |
| License | Proprietary | MIT(OSI) |
| Openness | Proprietary | Open source |
| Commercial use | Commercial use with conditions | Commercial use allowed |
| Knowledge cutoff | 2024-11 | 2023-10 |
Pricing and availability
| Pricing attribute | Grok 4.3 | Phi 3.5 Mini Instruct |
|---|---|---|
| Input price |
| $0.90/1M tokens |
| Output price |
| $0.90/1M tokens |
| Providers |
Capabilities
| Capability | Grok 4.3 | Phi 3.5 Mini Instruct |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | No |
| Reasoning | Yes | No |
| Function calling | Yes | No |
| Tool use | Yes | 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 vision: Grok 4.3, multimodal input: Grok 4.3, reasoning mode: Grok 4.3, function calling: Grok 4.3, tool use: Grok 4.3, and structured outputs: Grok 4.3. 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, Grok 4.3 lists tiered pricing: 0-200,001t is $1.25/1M input and $2.50/1M output; 200,001t+ is $2.50/1M input and $5/1M output, while Phi 3.5 Mini Instruct lists $0.90/1M input and $0.90/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Phi 3.5 Mini Instruct lower by about $0.72 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 4 providers versus 2, so concentration risk also matters.
Choose Grok 4.3 when reasoning depth, larger context windows, and broader provider choice are central to the workload. Choose Phi 3.5 Mini 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, Grok 4.3 or Phi 3.5 Mini Instruct?
Grok 4.3 supports 1m tokens, while Phi 3.5 Mini 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, Grok 4.3 or Phi 3.5 Mini Instruct?
Grok 4.3 lists tiered pricing: 0-200,001t is $1.25/1M input and $2.50/1M output; 200,001t+ is $2.50/1M input and $5/1M output. Phi 3.5 Mini Instruct lists $0.90/1M input and $0.90/1M 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 Grok 4.3 or Phi 3.5 Mini Instruct open source?
Grok 4.3 is listed under Proprietary. Phi 3.5 Mini 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, Grok 4.3 or Phi 3.5 Mini Instruct?
Grok 4.3 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, Grok 4.3 or Phi 3.5 Mini Instruct?
Grok 4.3 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 Grok 4.3 and Phi 3.5 Mini Instruct?
Grok 4.3 is available on xAI Console, OpenRouter, Microsoft Foundry, and Vercel AI Gateway. Phi 3.5 Mini Instruct is available on Fireworks AI and NVIDIA NIM. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-25. Data sourced from public model cards and provider documentation.