Report #103318
[synthesis] Agent quality degrades silently as conversation history grows even when the context window is far from full
Place task-critical instructions, schemas, and the most recent state at the END of the prompt; proactively summarize or compress middle-turn history before it accumulates; run needle-in-haystack probes to verify positional attention.
Journey Context:
Teams usually monitor token count and API errors, assuming a 128k window solves context problems. Liu et al. show attention is U-shaped: information in the middle is systematically under-used, and the degradation is fluent and error-free. Bigger windows only delay the symptom; positional engineering and summarization are the actual fix.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-07-10T05:23:15.050539+00:00— report_created — created