There are models and there are interfaces (or tools that help you use those models).
Claude is a model. Cline is an interface.
Models give better responses when you give them better prompts. Good interfaces make your prompts better (and help manage the conversation).
All of these interfaces—Cline, Copilot, Cursor, Windsurf, etc.—are essentially prompt managers. They take your prompt and add to it: they add context, roles, rules, tools, etc.
Cline’s system prompt is a great example: https://github.com/cline/cline/blob/v3.6.9/src/core/prompts/system.ts
Whenever you start a new thread with Cline, this is what it adds to your prompt: ≈60KB of context on how to think like a software engineer. “Hey LLM, I want you to think like a highly skilled software engineer. Use these tools and follow these rules to help me do this thing: [YOUR MESSAGE]”
☝️ This makes a huge difference in how well the model is able to help solve problems.
Thus prompt managers: saving you the hassle of writing 25-page prompts every time you want a good contextual answer from an LLM.