GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

A recent analysis of Codex token_count metadata reveals that GPT-5.5 responses disproportionately cluster at exactly 516 reasoning output tokens, with additional spikes at 1034 and 1552. This model-specific anomaly coincides with lower overall reasoning-token intensity and may explain degraded performance on complex Codex tasks. This clustering is significantly higher for GPT-5.5 compared to other models and increased sharply from February to June 2026. The Codex team is asked to investigate if this indicates a reasoning-budget or truncation behavior.