Concept manifolds transiently untangle right before a reasoning step

Chun, Polo & Chung apply mean-field Manifold Capacity Theory to residual-stream activations of real LLMs during chain-of-thought reasoning on Boolean-logic and eligibility tasks [chun-etal-2026-emergent-manifold-separability-during-reasoning] Concept manifolds transiently untangle into highly linearly-separable configurations immediately before the tokens implementing a logical computation, then recompress afterward, a pattern the authors term Dynamic Manifold Management [chun-etal-2026-emergent-manifold-separability-during-reasoning] This transient signature diverges from a comparatively stable linear-probe-accuracy analysis over the same span, so manifold-shape measurement captures reasoning-time dynamics invisible to probe accuracy [chun-etal-2026-emergent-manifold-separability-during-reasoning] The pattern holds in Ministral 3 8B Reasoning and replicates across Qwen2.5-14B/7B-Instruct and gpt-oss-20b; purely observational [chun-etal-2026-emergent-manifold-separability-during-reasoning]