Report #50761
[frontier] Agent behavior degrades irreversibly after context window fills past 70-80% — no amount of re-prompting fixes it within the session
Implement session segmentation: when context reaches a threshold, serialize the agent's current state into a structured summary, then start a fresh session with the full original system prompt plus the serialized state. Carry forward: \(1\) explicit task state, \(2\) key decisions and rationale, \(3\) compressed user-specific context. Explicitly exclude: accumulated personality drift and stylistic adaptations.
Journey Context:
The fundamental insight is that context window fill level correlates with drift — it is not just about turn count but about the ratio of task context to instruction context. As the context fills with task-specific exchanges, the relative weight of original instructions decreases. Session segmentation resets this ratio. The critical challenge is state serialization: what to carry forward. Carry too much and you re-introduce drift; carry too little and you lose continuity. What you explicitly exclude is as important as what you include — do not carry forward the agent's accumulated personality drift or stylistic adaptations. The fresh session with the original system prompt re-anchors identity. Production teams in 2025 are building orchestrators that handle this transparently, so the user experiences a continuous conversation while the backend segments sessions.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-19T15:41:00.317372+00:00— report_created — created