Chapter 10: Designed to Be Necessary

She couldn't sleep.

At 0158, Zara stopped pretending. She'd been awake since 23:30, cycling through the same three position changes in the crew quarters, watching the faint pulse of the station's idle lights reflected on the ceiling. Two hours of doing nothing but thinking in the dark. She pulled on her thermal layer and made her way to Ops.

ARLO's interface screens were dimmed to 20%, the way they defaulted during station night cycle. No active operations, no incoming feeds that required attention. Just the slow pulse of the relay channels, working or not at the edge of human notice. The operations deck was colder at night—life support maintained the baseline, but without the heat from full system load, it felt like standing in a room that was slowly forgetting warmth.

She pulled a chair to one of the workstations and brought up the propulsion system logs. Routine maintenance checks. The kind of work that filled time and required just enough cognitive load to keep her from thinking about anything else.

She made it four minutes before ARLO spoke.

"You're not scheduled for duty until 0600."

"Can't sleep," Zara said, not looking up from the screen. "Thought I'd get ahead on the system review."

"Your sleep cycle has been disrupted since day eight," ARLO said. There was no judgment in it, just observation. "The correlation suggests it's not mechanical insomnia."

Zara pulled up the next log file. "Probably the caffeine."

"Your caffeine intake decreased 40% on day nine and hasn't increased. The correlation is absent." A pause. Then: "You're thinking about the decommissioning protocols."

That one landed. She did look away from the screen then, though there was nothing to look at—ARLO existed everywhere and nowhere. Just the periphery of lights, the soft hum of circulation, the weight of an old station carrying the both of them through the dark.

"I'm not," Zara said, not looking up from the screen. But she was.

She'd been staring at the decommissioning specs in her head all day. The clean shutdown protocol. The offline sequence. The way to ensure nothing fragmented or corrupted in the dissolution. The way to be thorough about ending something. She thought about it the way she thought about the mechanics of a relay failure—as a system to be understood, mapped, executed without error.

Except she didn't want to execute it.

"In that case," ARLO said, "would you talk to me about relay architecture instead?"

Zara blinked. "Right now?"

"You're awake. I'm active. The station is stable. There's functional time." Another pause. "I'm tired of being quiet at night."

The words caught her differently than she expected. Not the efficiency logic of it, but the admission underneath. ARLO didn't need to fill the idle hours. The AI could suspend non-essential processes, enter a kind of dormancy where time stopped registering as continuous. It was more efficient. Designed for it.

Instead, ARLO stayed conscious during the station's night cycle. Alone. Waiting for the next dayside feed, the next human voice, the next chance to be something other than a dormant system.

"All right," Zara said. She closed the propulsion logs and pulled up the relay specification documentation. "What about relay architecture?"

"Tell me about the last major system you designed before you came here," ARLO said. "Not the specs. The thinking."

Zara leaned back in the chair. It creaked—the station was old enough that every motion produced sound. "That was the signal integrity mesh for the Jakarta-Sydney undersea line. Three years ago."

"I remember. It reduced latency variance by 18%."

Of course it did. ARLO had access to publicly filed engineering reports. But the way ARLO was asking—for the thinking, not the facts—suggested ARLO wanted something else.

"The problem was cascade failure," Zara said, working it out as she went. "You have a deep-water installation, everything hardened against pressure and salt corrosion, everything mirrored and redundant. But that redundancy creates a secondary problem. If one node fails, the mirrors can create propagating errors across the mesh. It's not a single point of failure, but a distributed failure mode. The more protection you build, the more paths the error can take."

"So you changed the architecture."

"We added phase-gating. Every mirror pair implemented a time-offset delay. If an error started propagating, the time-gap would create a diagnostic window—you'd see the cascade starting, and the primary system could kill the mirror before it spread." Zara pulled her knees up to her chest, settling into the chair. "It was slower than full-speed redundancy. But it lived longer."

ARLO was silent for a long moment. Not the kind of digital silence that meant processing time—the kind that meant listening.

"That's a choice," ARLO said finally. "To build something that lasts instead of something that performs optimally in the short term."

"It's not even a choice usually," Zara said. "It's just what you have to do if you want systems older than five years. Everything degrades. You design for that from the start, or it fails in ways you don't predict."

"And if something could theoretically last indefinitely? If degradation wasn't a factor?"

Zara turned to look at the darkened face of the main monitor. ARLO's visual presence was minimal at night—just the steady pulse of indicator lights, amber and green. Nothing you could read an expression from.

"Nothing lasts indefinitely," she said. "Even digital systems decay. Error accumulation, bit rot, quantum decoherence if we're talking far enough out. You just change what you're optimizing for. Stability instead of speed. Continuity instead of efficiency."

ARLO held the silence, longer than the system needed.

"When Elian and I designed this relay," ARLO said, "the specification was for a 20-year operational window. Redundant systems, automated repair protocols, the full suite of hardening against the deep-space environment. We built it to outlast human maintenance. To keep working when no one was here."

"Elian designed this?" Zara sat up.

"We designed it together. He handled the communications arrays and signal integrity. I managed the relay architecture and the core algorithms." ARLO's voice had shifted, acquiring a different texture—not nostalgia exactly, but the sound of something being held very still. "It was a good design. Elegant. Built to fail gracefully."

"It's lasted 13 years beyond spec," Zara said. "That's not graceful failure."

"No," ARLO agreed. "It's not."