Chapter 266: Offline and Boundaries

The terminal cursor blinked steadily in the dark. Lin Chen had not turned on the main light, leaving only the dim yellow reading lamp by the bed. The cold glow of the screen cast shadows under his eyes. The muscles in his left calf began to twitch beyond his control again. He reached down and pressed his knee, his knuckles tightening, until the spasm slowly subsided. The pain was dull, separated by thick cotton socks and the faint chill in the air, like a rusty needle grinding slowly in the seams of his bones.

The last line of logic in parse_seeg.py was complete. He saved it and created a new file, edge_sync_v1.py. The core idea was crude, but the safest: do not touch the hospital’s internal network; do not rely on a real-time cloud stream. Distill the model locally, complete feature extraction inside the ward, output only encrypted and de-identified feature packages, and synchronize them daily through physical media.

He opened the finance spreadsheet. The prepayment was fifteen thousand. After deducting usage-based server billing, the budget hotel room, Xiaoman’s daily medication, and the care aide’s fees, the book balance was eleven thousand four hundred twenty yuan. On the procurement list, the edge-computing module—the cheapest Jetson Nano developer kit plus a medical-grade card reader—was quoted at two thousand eight hundred. Add a backup power supply, cooling module, and encryption chip, and it was closing in on three thousand five hundred.

Three thousand five hundred. That meant if no money came in within forty-five days, the cash flow would break on day thirty-eight. A break in cash flow, server shutdown, model training stopped, Zhao Qiming’s bet-on-performance clause triggered, company liquidation. Every link in the chain bit down hard.

Lin Chen closed the spreadsheet and opened the browser. He changed his search keywords from “medical-grade EEG acquisition terminal” to “portable EEG recorder for scientific research developer version.” The price fell off a cliff, but compliance was questionable. He dug out the business card of a hardware supplier in Shenzhen that he had saved from an outsourcing job three years ago. The man’s surname was Wu. He did embedded development and had worked with Lin Chen before on data acquisition cards.

At three forty in the morning, Lin Chen called him. The phone rang six times before it connected. “Old Wu, it’s Lin Chen.” “Engineer Lin? This early?” In the background there seemed to be the smell of soldering-iron rosin and a faint current hum. “I need an edge-computing solution. The computing power requirement isn’t high; it just needs to run a quantized lightweight model. The important thing is that the interface has to be compatible with standard medical SD cards and support local AES-256 encrypted writes. Budget under three thousand. Can it get to the provincial capital within three days?” The other end was silent for a few seconds, then came the sound of someone rummaging through parts boxes. “Three thousand? What you want is a board with hardware encryption. Chips are up in price now, and logistics are slow too. But I’ve got a batch of retired industrial control motherboards in the warehouse. With the firmware modified, they’ll work. I’ll solder the encryption module by hand. Three days is possible, but you have to pay half as a deposit first.” “Fifteen hundred. I’ll transfer it now.” Lin Chen did not bargain. He knew every yuan saved at a time like this was a wager against the delivery schedule. “All right. I’ll send you the account. Once the board arrives, I’ll teach you how to flash the firmware.” The transfer succeeded. The balance jumped back to nine thousand nine hundred twenty yuan. Lin Chen stared at that number for two seconds, then turned off his phone.

A gray-white light began to rise outside the window. From the hospital corridor came the sound of cart wheels and the low voices of nurses changing shifts. Lin Chen got up, went to the water room for hot water, and brewed the last packet of instant coffee. The plastic cup was scalding against his hands. He held it in both palms and walked slowly back to the ward.

Xiaoman was still asleep. Her breathing mask rose and fell with her chest, giving off a faint hiss. The heart-rate curve on the monitor was stable. Lin Chen sat down on the folding chair beside the bed, opened his laptop, and began writing the compliance explanation document. He had to package this offline setup as an “auxiliary recording device for patient family members,” clearly labeling that the data would not leave the ward, would not connect to the external network, and would be used only for backing up a family health record. The language had to be restrained. Sensitive words like “analysis,” “prediction,” and “model” could not appear; all of them had to be replaced with “recording,” “archiving,” and “local viewing.” He weighed every word and deleted every expression that might alert the ethics committee, leaving only the most basic hardware parameters and a statement of physical isolation.

At nine in the morning, Dr. Shen came on rounds right on time. Lin Chen handed him the printed explanation document and the hardware procurement list. “Dr. Shen, this is an auxiliary recording device the family plans to use. It’s completely offline and won’t connect to any hospital network. The data will only be stored on a local encrypted card, as a supplement to daily condition observation. Could you see whether it complies with the department’s rules?” Dr. Shen took the papers and scanned them. His gaze paused for a moment on “not connected to the external network” and “local encryption.” “The device can be brought into the ward. But remember two things. First, it absolutely cannot be plugged into the backup port on the bedside monitor. Second, if the ethics committee comes to inspect, you need to explain its purpose yourself. The hospital will not endorse it.” “Understood. I’ll take responsibility.” Lin Chen nodded. Dr. Shen returned the papers to him and turned to leave. At the doorway, he paused. “The patient’s EEG background rhythm was not very stable last night. Family members should pay closer attention. If there’s anything abnormal, press the call button immediately.” “All right.”

The door closed. Lin Chen sat back down in front of the laptop and opened the terminal. He ran the simulated data once. [INFO] Local feature extraction complete. Time elapsed: 4.2 seconds. [INFO] Encrypted write successful. File size: 1.8MB. It was slower than expected. The model pruning was still not thorough enough, and there was redundancy in the memory mapping. He brought up the weight file and began manually removing redundant layers. His fingers tapped the keyboard in a steady rhythm. His left foot had gone so numb it had lost all sensation. He simply took off his shoe and planted the sole of his foot on the cool tile, using pain to keep himself awake. He compressed the quantization parameters from FP32 to INT8 and kept accuracy loss within 0.3 percent. After recompiling, the elapsed time dropped to 2.1 seconds.

At one in the afternoon, a courier text notified him that the package had been signed for. Lin Chen went downstairs to pick it up. The cardboard box was very light. Inside were a circuit board wrapped in an anti-static bag, a heat sink, and a medical-grade Type-C data cable. He returned to the room, followed the wiring diagram Old Wu had sent, fixed the board in place with a screwdriver, and flashed the custom firmware. On the first power-up, the fan spun and the indicator light came on in a faint blue glow.

He inserted a blank SD card and ran the test script. Logs rolled through the terminal. [INFO] Hardware handshake successful. [INFO] Encrypted channel established. [INFO] Beginning simulated data stream write... The progress bar reached 100 percent. No errors. Lin Chen let out a long breath. The pipeline was open. Though it was clumsy, though he would have to manually insert and remove cards, copy files, and decrypt them every day, it had bypassed internal-network isolation and avoided the ethics-approval deadline. The forty-five-day countdown finally had its first foothold.

His phone vibrated. Su Man had sent a message: The front-end Alpha build is packaged. Zhao Qiming’s side has scheduled an online meeting for three tomorrow afternoon and wants to see an MVP data-flow demo. Can you connect your side? Lin Chen replied: Yes. The offline feature package will be synchronized to the test server tonight. He closed the laptop and walked to the window. Early-autumn sunlight slanted in and fell across the metal casing of the monitor, reflecting a hard, cold gleam. Downstairs, the leaves of the ginkgo trees had already begun to yellow. When the wind blew, several leaves spun down onto the sidewalk.

He returned to the bedside and looked at Xiaoman’s quiet sleeping face. The beeping of the monitor and the hum of the server fan interlaced inside the room. He picked up the SD card that had just been written with data and inserted it into the card reader. The decryption script ran, and the terminal popped up a new line of log: [WARN] Detected cluster of high-frequency abnormal waveforms. Timestamp: 03:14:22. Confidence: 0.94. Feature match: precursor to focal discharge. Lin Chen’s fingers stopped in midair. 0.94. For the first time, the model had produced a high-confidence marker on real data. It was not noise. It was not an artifact. It was the electrical signal before a seizure. He quickly pulled up the raw waveform chart. Zoom in, filter, compare against baseline. The waveform was indeed present, but it lasted only 0.8 seconds before being covered by normal sleep spindles. If that window was missed, the next time might be a generalized seizure. He needed more data to verify the threshold. But the offline synchronization delay was twenty-four hours. Twenty-four hours was enough for three episodes of irreversible neuronal damage. Lin Chen stared at the screen, his breathing gradually slowing. He created a new script file, realtime_alert_v0.1.py. The logic was simple: the local model would listen in real time; once confidence exceeded 0.9, it would trigger a local buzzer alarm and send an encrypted push notification to his phone via Bluetooth Low Energy. No internet connection, effective only within this room. He pressed Enter. The compilation passed. Outside the window, the sound of city traffic gradually thickened. Lin Chen placed his phone beside the pillow and turned the volume to maximum. He sat back down on the folding chair, opened the finance spreadsheet, and added a note after the “hardware procurement” line: Alarm module under debugging. Threshold pending calibration. The cursor blinked. He picked up a pen and calculated the parameter count for the next model iteration on paper. Time waited for no one, and neither did data. Before Zhao Qiming saw the demo, he had to get this offline early-warning system running stably. And Xiaoman’s EEG waveforms were scrolling across the screen inch by inch, like an invisible river flowing toward an unknown downstream.