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3.1The Context Window is a Shared Resource
Every token in the context window competes for the same limited space. A coding agent typically needs context for:
| Consumer | Typical Tokens | Priority |
|---|---|---|
| System prompt | 2,000-5,000 | Fixed |
| Conversation history | 10,000-50,000 | Grows |
| File contents (code being edited) | 5,000-30,000 | Essential |
| Tool definitions (MCP, built-in) | 2,000-15,000 | Fixed per tool |
| Agent reasoning | 5,000-20,000 | Essential |
| Total budget | ~200,000 |
When you add browser automation, you're competing with code editing, test analysis, and reasoning for that same budget.