7,400 trajectories analyzed: Claude Code and Codex carry ~25k ISL vs Terminus 2's 8k

zainhas · x · 2026-08-28

The author analyzed 7,400 agent trajectories to measure "harness bloat" — how much context an agent framework injects at each step, tracked via input/output sequence length (ISL, OSL).

Early findings: Terminus 2 is the most barebones at 8k ISL per step, while Claude Code and Codex sit at 25k ISL — roughly 3x heavier. A full writeup is promised soon. Framework overhead alone can meaningfully inflate token costs and latency for coding agents.

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