The correct option is The file length exceeds the amount of code that Copilot can consider at once. When you edit near the bottom of a very long file the model can only attend to a limited window of surrounding code, so earlier patterns fall outside that window and suggestions feel less connected to the rest of the file.

Copilot bases its completions on the code and comments around your cursor and on other nearby or open files. All large language models work within a fixed context window, which means only a portion of the file can be included in the prompt at any time. In a 2,800 line TypeScript file the sections near the top are likely outside the active context while you edit near the bottom, so the assistant cannot reliably use those earlier patterns when proposing completions.

Copilot supports only UI frameworks and ignores backend code is incorrect because Copilot works across many languages and domains, including backend TypeScript and server side frameworks, and it does not limit support to UI code.

You must retrain or fine tune Copilot on your repository to improve suggestions is incorrect because users do not retrain or fine tune Copilot on their own data. Copilot improves suggestions by using the immediate coding context in your editor rather than by per repository model training.

Copilot is incompatible with TypeScript projects is incorrect because Copilot fully supports TypeScript and is widely used in TypeScript codebases. The issue in this scenario stems from context limits, not language compatibility.

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