Plan->Compact->Re-Plan infinite loop in agency copilot (217 cycles, zero code written)

[Akhi-microsoft]

Repro

Started a coding task with agency copilot. After auto-compaction fired, the agent re-read the compaction summary and started re-planning instead of executing. This repeated through 217 plan→compact→re-plan cycles before I killed the session.

Root cause (hypothesis)

Compaction summarizes "we planned X, Y, Z" into the new context. The agent reads the summary and treats the plan as a fresh prompt to plan against, instead of as decided work to execute. The plan becomes self-perpetuating.

Impact

• Burned through hours of compute and my Copilot quota
• Zero code written despite hundreds of turns
• Severe trust hit for autonomous workflows

Asks

1. Treat plans in compaction summaries as DONE-DECIDED, not as new prompts
2. Add a built-in "execution mode" flag that biases hard against re-planning
3. Bundle a post-compact reminder hook by default (like post_compact_reminder)
4. Surface a loop detector: N consecutive turns with zero file edits → halt
5. Better default /compact preservation that drops planning history

Happy to share session logs and jump on a call to walk through the repro.

— Akhi Shukla, Senior PM, IC3 / UED (Prague)