System/Tools consume 73% of context window (146k/200k), triggering auto-compaction on first message

With multiple MCP servers and plugins configured, the System/Tools section consumes 146k tokens — 73% of the 200k context window. This leaves negative free space before the user sends their first message, causing immediate auto-compaction in brand new sessions.

Reproduction

1. Configure ~10 MCP servers (mix of builtin and custom)
2. Install plugins that register additional tools and skills
3. Have custom instruction files in ~/.copilot/copilot-instructions.md and .github/instructions/
4. Start a new session
5. Run /context

System/Tools: 146.4k (73%)
Messages: 1.2k (1%)
Free Space: -18383 (-9%)
Buffer: 70.8k (35%)

Auto-compaction fires after the first interaction (~100 credits used), despite no meaningful conversation history to compact.

Environment

- Copilot CLI v1.0.55-1
- Windows 11, PowerShell
- Model: Internal model
- ~10 MCP servers configured across user and org plugins

Impact

- Effectively unusable for multi-turn conversations without constant compaction
- Credits wasted on compaction rather than productive work
- Users with enterprise MCP setups hit this silently with no warning