AIToday
Large Language ModelsHacker NewsPublished: Jul 15, 2026, 22:00 JST

GPT-5.6-terra uses 48.5% more tokens than Mimo-2.5-pro in agent tasks

3 Key Points

  1. What happened

    A developer compared GPT-5.6-terra and xiaomi/mimo-v2.5-pro by running the same repository through both models on >80 tasks each using Dirac as the test harness. GPT-5.6-terra's average final transcript was 91,794 tokens versus Mimo's 61,831 tokens — a 48.5% difference.

  2. Why it matters

    The larger context consumption directly translates to higher costs per task. The developer found Terra made inefficient tool calls — reading hundreds of lines at a time rather than targeted line ranges, executing commands with oversized outputs (e.g., full test runs instead of tail -20), and repeatedly checking changes even for trivial edits — patterns that score well on benchmarks but waste tokens and slow real-world work.

  3. What to watch

    The developer noted Terra showed an "obsession with Git," constantly examining commits and diffs for debugging even after being instructed not to; at the current pricing, the volume cost and task duration make it a less attractive choice than Mimo despite Terra's correctness on most tasks.

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Context & Analysis

The comparison reveals a tension between benchmark performance and practical efficiency in AI agents. GPT-5.6-terra's behavior — maximal context exploration, small incremental edit-and-check loops, and extensive tool use — are traits that often correlate with high benchmark scores, as the developer notes. However, these same patterns translate to inefficiency in real-world tasks where context window size directly impacts cost and latency. The specific inefficiencies (reading full files rather than targeted spans, running unfiltered commands, obsessive Git inspection) suggest that Terra may be trading practical awareness for exploratory thoroughness. The developer's decision to adjust instructions to limit Git usage, which Terra then ignored, hints at a model that is difficult to steer away from its learned behaviors even with explicit guidance. The 48.5% token inflation is not merely a curiosity—it compounds across many tasks, making the economic and time costs substantial enough to outweigh Terra's correctness on individual tasks.

FAQ
How many tasks were tested in this comparison?
The developer ran 95 tasks on GPT-5.6-terra and 81 tasks on xiaomi/mimo-v2.5-pro, using the same repository and task distribution.
What were the main reasons GPT-5.6-terra used more tokens?
The developer identified three main inefficiencies: reading hundreds of lines per file call instead of targeted ranges, executing commands that produced large outputs (e.g., full test runs instead of filtered output), and repeatedly editing and checking trivial changes rather than batching edits before verification.
Did GPT-5.6-terra produce correct results?
Yes, the developer stated "it does get things right most of the time," but the larger context window usage and slower task completion time made it less practical despite correctness.

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