Chen Xi had named the problem months ago.

  The Broken Constant.

  In physics, a constant is a value that does not change. The speed of light. Planck's constant. Gravitational constant. The anchors of reality. The numbers you trust.

  The Vortex Core was built on a constant: that Qi behaved as a conserved, predictable fluid, obeying the same transport equations regardless of density or context.

  In the Silt, this held perfectly.

  In the Torrent, it was broken.

  He discovered it during the third week, designing the selective intake filter. The filter required distinguishing ambient Qi from cultivator-circulated Qi based on energy signatures.

  In theory: simple. Ambient Qi was chaotic, random. Cultivator Qi was structured, coherent.

  In practice, at Torrent density, the distinction collapsed.

  The ambient Qi here was not chaotic. It was semi-structured — influenced by millennia of cultivators circulating energy through this region.

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  The Qi river itself was cultivator-made, carrying the combined signature of every technique ever practised within its watershed.

  The constant he'd built on, that ambient Qi was distinguishable from cultivator Qi — was not constant.

  It was context-dependent. It changed with density, location, and history.

  This broke everything.

  Not the vortex. That still spun, still achieved fifty-four percent. But the selective filter couldn't be built on a foundation that didn't exist.

  Without the filter, the drain continued.

  Without fixing the drain, Chen Xi was a danger to everyone he cared about.

  He spent three days staring at equations that refused to resolve.

  On the fourth day, he threw his notebook across the room.

  It hit the wall with a sound more satisfying than it should have been.

  And something broke in him. A dam of competence and control that had held since the Silted Bones.

  The dam that allowed him to approach every challenge as a problem to be solved, every loss as a data point to be filed.

  He sat on the floor of his room. Thirty-one metres from everyone he cared about.

  He felt — actually felt, without filing or categorising — every thing he'd been storing since he died.

  Elena. Stanford. The coffee machine. The equation glimpsed for 0.003 seconds. The body that wasn't his. The world that wasn't his. The friends who couldn't safely stand near him.

  He counted primes.

  2, 3, 5, 7, 11, 13...

  43 — his age at death.

  67 — the efficiency that made him exceptional in a lower world and merely competent here.

  73 — the years Wu Zheng spent in a graveyard waiting for someone who was now failing him from thirty-one metres away.

  He stopped counting.

  The silence was worse.

  But broken things, he was beginning to understand, sometimes contained the pieces of something better.