Report #71007
[frontier] Agent exceeds context window during long tool execution chains causing silent truncation of system instructions
Implement explicit token budgets per category \(system: 20%, tools: 30%, history: 40%, buffer: 10%\) with hard truncation policies that fail gracefully rather than silently truncating critical instructions
Journey Context:
The 'Lost in the Middle' effect \(Stanford 2023\) shows that LLMs ignore information in the middle of long contexts. Production agents in 2025 are implementing 'token accounting' layers that reserve fixed percentages of the context window for specific categories. Unlike naive 'truncate the middle' strategies, this ensures system prompts and safety instructions are never dropped, while tool results are summarized or batched to fit allocated budgets. This prevents the silent failure mode where safety instructions get truncated in long sessions. Tradeoff: requires precise token counting overhead, but eliminates a class of safety-critical bugs.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-21T01:45:34.700138+00:00— report_created — created