Key facts
| API format | OpenAI-compatible /v1/chat/completions; Anthropic clients need a thin adapter |
| Models | 30+ models from free tiers to frontier reasoning in one catalogue |
| Pricing | Flat monthly self-serve plans with unlimited fair-use usage |
| Free tier | plugsky-micro and plugsky-lite on the free plan, no card required |
| Trial | 14-day full-access trial for frontier models |
| Deployment | Plugsky cloud, your VPC, on-prem and air-gapped |
| Streaming and tools | Streaming, JSON mode and function calling are live |
TL;DR
- Claude's Messages format is not OpenAI-shaped, so budget for an adapter or rewrite.
- An OpenAI-compatible alternative keeps the rest of your stack portable.
- 30+ models and flat monthly pricing make inference spend predictable.
- The free plan plus the 14-day full-access trial cover evaluation.
- Keep Claude for Claude-specific work; standardise commodity calls on one API.
How it works, step by step
- Inventory Claude API calls: chat, streaming, tool use, vision and long-context prompts.
- Separate Claude-specific workloads from commodity text generation.
- Stand up Plugsky on the free plan and rewrite the commodity calls to the OpenAI-compatible endpoint.
- Port tool schemas to OpenAI function-calling format and test edge cases.
- Run the same evaluations on both providers for quality, latency and refusal behaviour.
- Cut over non-Claude workloads, keep a rollback path and monitor usage.
Original data
Try it yourself
Open the Anthropic Claude API cost calculator →
Format differences that drive migration cost
Anthropic's Messages API is a good design, but it is not a drop-in copy of OpenAI's chat completions schema. Message roles, system prompts, tool definitions and streaming events all differ, which means client code, validators and prompt templates need attention. For a small app that is an afternoon of work; for a platform with dozens of services it is a project.
The cheapest migration is usually a compatibility layer. Point Anthropic-style calls at an adapter that translates to an OpenAI-compatible endpoint, then remove the adapter service by service as you rewrite call sites. That keeps risk contained and lets you compare quality per workload before you commit.
What an OpenAI-compatible alternative changes
Plugsky exposes an OpenAI-compatible chat completions API, so anything already written against the OpenAI SDK works with a base URL and model-name change. The catalogue spans 30+ models, from free tiers to frontier reasoning, which gives you room to route easy traffic to cheap models and reserve stronger ones for hard prompts.
- One key and one endpoint for chat, embeddings, RAG and agents.
- Flat monthly self-serve pricing instead of counting tokens.
- Free plan with plugsky-micro and plugsky-lite, no card, plus a 14-day full-access trial.
- VPC, on-prem and air-gapped deployment options for regulated teams.
Honest gaps and when to keep Claude
Plugsky does not serve Anthropic's Claude models, so if you depend on Claude-specific tone, safety behaviour or a particular long-context workflow, keep those calls where they are. Plugsky also does not ship audio, image or moderation endpoints yet; those are coming soon. The practical pattern is hybrid: route commodity generation, classification and embeddings through Plugsky, and keep provider-specific calls on Anthropic until your evaluations show a replacement is safe.
Start with the free plan to measure, then move to a paid plan when the numbers justify it. Because the API is OpenAI-compatible, the reverse migration is just as cheap.
Honest comparison
| Concern | Plugsky | Anthropic Claude API | Custom adapter layer |
|---|---|---|---|
| Request format | OpenAI-compatible | Anthropic Messages format | Translate both schemas |
| Client code | OpenAI SDK unchanged | Anthropic SDK | You maintain mappings |
| Pricing shape | Flat monthly self-serve | Usage-based | No change |
| Model choice | 30+ models, one API | Claude family | You route manually |
| Residency | Region choice, VPC, on-prem, air-gapped | Provider regions | You control |
Frequently asked questions
Is Plugsky compatible with Anthropic's Claude API?
Not directly. Plugsky is OpenAI-compatible, so Anthropic-style clients need a small adapter or a rewrite of the call sites you migrate.
Do I have to migrate everything at once?
No. Most teams move commodity chat and embeddings first, keep Claude for Claude-specific workloads, and expand coverage as evaluations pass.
Is there a free plan?
Yes. The free plan includes plugsky-micro and plugsky-lite with no credit card, and a 14-day full-access trial opens the full model catalogue.
How is pricing structured?
Self-serve plans are flat monthly with unlimited fair-use usage, with no per-token billing on self-serve. See the live pricing page for current plans.
Does Plugsky support tool calling and streaming?
Yes. Streaming, JSON mode and function calling are live; check the docs for per-model details.
Can I keep Anthropic and Plugsky side by side?
Yes, and it is the recommended path. Split traffic by workload, compare quality on real prompts, and cut over only what passes your evaluations.
Can Plugsky deploy in my own environment?
Yes. Plugsky supports VPC, on-prem and air-gapped deployments for enterprise customers.