[Bug] Conversation compaction fails with "Conversation too long" error at 50% context usage

Bug Description

/compact Get ready to implement this plan. ⎿ Error: Error during compaction: Error: Conversation too long. Press esc twice to go up a few messages and try again. /context

⎿
Context Usage
⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛀ ⛁ ⛀ claude-sonnet-4-5-20250929 · 100k/200k tokens (50%)
⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁
⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ System prompt: 2.5k tokens (1.2%)
⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ System tools: 13.3k tokens (6.6%)
⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ ⛁ MCP tools: 3.0k tokens (1.5%)
⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛁ Memory files: 10.2k tokens (5.1%)
⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛁ Messages: 70.8k tokens (35.4%)
⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ Free space: 100k (50.1%)
⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶
⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶ ⛶

Environment Info

• Platform: darwin
• Terminal: vscode
• Version: 2.0.27
• Feedback ID: 9011388f-be91-4209-a3e9-1e7c8a070080