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Bug: Plan->Compact->Re-Plan infinite loop after auto-compaction #3152

@Akhi-microsoft

Description

@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. With no execution-bias instruction surviving compaction, the loop is structural -- not prompt-specific.

Expected: After compaction, agent resumes from the next concrete file edit. Plans already produced are treated as decided.

Actual: Agent re-summarizes its own plan, validates it, repeats. No file edits across hundreds of turns.

Impact:

  • Burned through hours of compute and Copilot quota
  • Zero code written despite hundreds of turns
  • Severe trust hit for autonomous/long-running workflows
  • Likely under-reported -- users blame themselves before blaming the tool

Asks (priority order):

  1. Treat plans in compaction summaries as DECIDED, not as new prompts. Surface next concrete action as the primary continuation signal.
  2. Inject a default post-compact rule: Resume from the next file edit. Do not re-validate the plan. (Reference: github.com/Dicklesworthstone/post_compact_reminder)
  3. Add a built-in --mode execute session flag that biases hard against planning preambles.
  4. Loop detector: N consecutive turns with zero file edits -> halt and prompt user (suggested default N=3).
  5. Better default /compact preservation: drop planning history, keep only files modified, current error state, and next concrete action.
  6. Add telemetry signal for planning loop suspected to quantify real-world frequency.

Current workarounds (work but should not be required):

  • AGENTS.md with explicit no re-plan after compact rule
  • Post-compact reminder hook (manual third-party install)
  • Manual /compact at ~60% with explicit preservation instructions
  • HANDOFF.md as ground-truth state file

Happy to share session logs and jump on a triage call.

-- Akhi Shukla, Senior PM, IC3 / UED (Prague)
Manager: Bryan Castro | Skip: Nils Dussart

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    area:agentsSub-agents, fleet, autopilot, plan mode, background agents, and custom agentsarea:context-memoryContext window, memory, compaction, checkpoints, and instruction loading

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