Three big problems with subagents: lossy handoffs, hidden eval failures, debugging hell
arpit_bhayani · x · 2026-09-17
The author lays out three core problems with multi-agent architectures:
- Lossy handoffs: agents pass only summaries, not reasoning traces, so receivers lack the context behind conclusions and may take unexpected paths.
- Misleading evals: each subagent can pass its own evals while the system still fails — e.g. a retrieval agent returns correct docs, a synthesis agent summarizes them correctly, yet the answer is wrong because they weren't aligned on user intent.
- Debugging pain: one agent gives you a single trace to step through; N concurrent agents give you N context windows intersecting only at handoffs — precisely where information was already lost.
None of this condemns multi-agent design, but coordination — what passes between agents and how failures surface — deserves as much design attention as the agents themselves.
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