Darak had the analysis drafted before Aliyah finished walking from the Keystone chamber to the instrument room.

He had been writing continuously since the moment the second bell rang, and had not stopped when the engagement ended.

"The probe's size was not incidental," he said, when she arrived. "A larger entity in the chamber would have required more of the garrison's attention to address, which is the pattern every previous incursion has followed."

"This probe required almost none of the garrison's attention. It required exactly one person's attention, for exactly as long as it took to dissolve, and that person was the one whose attention the reinforcement sequence depended on."

"It was placed for Vor'gath specifically," Aliyah said. "Not for the chamber. Not for the binding directly."

"The directing intelligence has been operating from observed patterns since the second incursion. It would have observed the chamber's reinforcement rhythm over weeks, the same way it observed the corridor rotation."

"A small disoriented probe, in the chamber, during a reinforcement window, produces exactly the gap we just experienced. It does not need to be large. It needs to be in the right place at the right time, and disoriented enough to require Vor'gath specifically rather than anyone else."

Aliyah sat with that.

The third Keystone's reading sat at its small permanent increase on the display in front of her, the first movement in weeks. The mechanism that had produced it had cost the directing intelligence almost nothing.

One small probe, dissolved in ten seconds, in exchange for ten seconds of unopposed pressure on a structural vulnerability that had been holding for weeks against everything else thrown at it.

"The lesson generalizes," she said slowly. "It does not need a large entity anywhere. It needs small things, placed correctly, timed to whatever rhythm the people doing the critical work have fallen into."

"The corridor protocols broke the rhythm for combat response. We have no equivalent for the chamber."

"Because the chamber has never needed one before today," Vor'gath said.

He had recovered enough to sit upright, though Rakh'ash'tha, who had come in when the bell rang and stayed, was still watching him with the specific attention she gave to people whose depletion she could not directly treat.

"I am the only person whose disruption work matters to the third Keystone's reinforcement. If something in the chamber requires my attention, there is no equivalent person to hold the rhythm while I am occupied."

"Could there be?" Aliyah said. "Not someone who can do what you do. Someone who can do enough."

Rakh'ash'tha looked up. "The second Keystone. The locus division technique, the night of the emergency reinforcement."

"I held a position by sustained physical contact and focused attention, dividing the load without being able to reinforce it directly."

"That was the second Keystone's binding," Vor'gath said. "The third Keystone's vulnerability is different, more precise, the chisel-and-grain point."

"Locus division on the housing would not interrupt the patient entity's pressure the way my disruption does."

"I am not proposing it would replace what you do," Rakh'ash'tha said. "I am proposing a third person in the chamber during reinforcement windows, whose function is not the binding at all."

"Whose function is the chamber itself. If something comes through the wall, that person is between it and you, for long enough that you do not have to choose between the probe and the rhythm."

Vor'gath considered this. "A physical buffer. Not a counter to whatever comes through."

"Enough delay that I can finish the disruption's current cycle before I have to turn toward whatever the probe is."

"Enough delay," Rakh'ash'tha agreed. "I held a Keystone housing through a night using sustained attention I had built over thirty years of medical practice."

"I do not know if that translates to standing between a person and an unknown small entity for the few seconds you would need. But it is something, where right now there is nothing."

Aliyah looked at the small dark scar on the chamber wall, then at Darak's analysis, then at Vor'gath and Rakh'ash'tha both.

"It is an interim measure," she said. "I am not pretending it solves what today demonstrated."

"What today demonstrated is that the directing intelligence has identified a category of weakness: the dependency of critical work on a single person's undivided attention. It will look for that category everywhere it exists, not only in this chamber."

She turned to Darak. "Write that as its own line, separate from the chamber-specific recommendation. Every critical function in this facility that depends on one person's attention is now a category of risk, not an individual exception."

Darak wrote it.

"For the chamber specifically," Aliyah continued, "Rakh'ash'tha is in the chamber during reinforcement windows, beginning with the next one."

"Her function is exactly what she described: a buffer, not a counter. If something comes through, she occupies it, physically, for however many seconds it takes, and Vor'gath finishes his current cycle before responding to it."

"And if what comes through is larger than today's probe," Vor'gath said. "Large enough that a buffer is not enough."

"Then we will have learned that the day it happens, the same way we have learned everything else."

Aliyah's voice did not change, but something in how she said it acknowledged the gap between what they were building and what might eventually be needed.

"I am not solving this today. I am making today's gap smaller than it was this morning. The rest is still open."

She went back to the third Keystone's reading, which sat at its small permanent increase, the first thing in weeks that the binding had given up and not gotten back.

She began the notation that would carry the day's events into the record, alongside everything else the record already held.

The instrument room settled back into its rhythm around her: Urrak at his station, Durahl and Kessin at theirs, Prenn still watching the sixth Keystone with the same unbroken attention he had given it before the bells rang, because nothing about his assignment had changed, and that, today, had been the point of it.