Chapter 303: Boundaries and Masks

The progress bar in the bottom right corner of the screen was stuck at forty-two percent. The industrial fans in the server room emitted a low hum, the hot air carrying the scent of ozone and dust clinging to the skin. Lin Chen's left foot had completely lost sensation, feeling like a piece of wood that didn't belong to his body, yet the muscles below his knee still twitched in fine, uncontrollable spasms. He pressed his palm against the outside of his left leg, pushing down hard until the physical pressure temporarily numbed the pain receptors, then let go.

Inside the terminal window, logs were scrolling.

INFO: Preprocessing module initiated. Dynamic mask loaded. Missing fields: Blood pressure (systolic/diastolic separated), Medical history (handwriting recognition confidence 0.61), Medication records (non-standard units: mg/dl → mmol/L). WARNING: Field "Liver Function ALT" missing units. Default conversion applied per 1998 provincial standards. Confidence downgraded and flagged. INFO: Sandbox isolation environment verification passed. External network request interception rate 100%. Local knowledge base loaded.

Lin Chen stared at the flickering characters. Medical records from ten years ago, yellowed paper, scrawled handwriting; the doctors' typos and abbreviations from back then had all become traps for the algorithm. During the V2.0 era, he relied on manual cleaning; now, he relied on rule-based fallbacks. He hit Enter, triggering the inference command.

The progress bar began to crawl upward. Forty-five percent. Fifty-one. Sixty-eight.

The glass door to the server room was pushed open gently. Zhou Zhen stood in the doorway, not stepping inside, just watching the screen through the glass. In his hand was the handwritten medical record summary, his fingertips rubbing the worn edges. Su Man followed behind him, holding a clipboard, her expression calm.

"Director Lin," Zhou Zhen's voice came through the glass door, slightly muffled. "What is the model running?"

"Filling in the probability distributions for missing dimensions." Lin Chen didn't turn around, his fingers hovering above the keyboard. "The records are missing renal function indicators and allergy history. The model won't make things up. It will use statistical priors from similar cases to fill the gaps, but it will minimize the weight of those imputed values. The final output isn't a diagnostic conclusion. It's a risk ranking and differential diagnosis recommendations."

"What if the priors are wrong?"

"That's why there are confidence intervals." Lin Chen brought up the visualization panel. Three curves appeared on the screen, each representing the probability distribution for a different pathological hypothesis. The peak landed at seventy-one percent, annotated beside it with CONFIDENCE: 0.71 [RANGE: 0.64-0.78]. "Below seventy-five percent, the system forcibly flags it as 'Requires Manual Review'. It doesn't overstep, and it doesn't usurp the doctor's judgment. That's the bottom line."

Zhou Zhen was silent for a few seconds. He pushed the door open, stepped inside, and placed the medical record on the edge of the console. "On the Health Commission's inspection checklist, there's an item called 'Algorithm Explainability'. Can this mask mechanism of yours be traced?"

"Yes." Lin Chen clicked open the audit view in the log module. Inside the local SQLite database, three hundred and twenty records were arranged by timestamp. Every data access, every weight adjustment, every skipped field had generated an independent hash value. The chain was complete and tamper-proof. "Every decision path leaves a trail. If a medical dispute arises in the future, we can fully export the raw snapshots of the inference process for third-party review. No black boxes, no buck-passing."

Zhou Zhen leaned down, examining the hash chains closely. His gaze lingered for a long time on the tags "Confidence Downgraded" and "Manual Review". The temperature in the server room continued to rise. The back of Lin Chen's short-sleeved shirt was soaked with sweat, clinging to his spine. He breathed lightly, trying not to let the rise and fall of his chest disturb the stability of the console.

The progress bar reached ninety-nine percent.

INFO: Inference complete. Output report generated. Unknown field skip rate 4.3%. Peak confidence 0.71. Recommendation: Transfer to manual review. SUCCESS: Sandbox closed-loop test passed. No privilege escalation, no data leakage, no interruptions.

Lin Chen pressed the export key. A PDF file landed on the desktop. He printed it out and handed it to Zhou Zhen.

Zhou Zhen took the report and flipped to the last page. There were no words for "Confirmed Diagnosis". Only: "Suspected chronic liver disease with metabolic abnormalities. Recommend completing abdominal ultrasound and renal function re-examination to rule out drug-induced liver injury." The format was standard, the wording restrained, fully compliant with clinical decision support specifications.

"Technically, it passes." Zhou Zhen closed the report, pulled a checklist from his folder, and ticked the boxes for "Offline Inference Compliance" and "Audit Traceability". "But Director Lin, I need to remind you of one thing. Getting the algorithm to run just gets you an entry ticket. The ethics committee at Provincial Second Hospital meets next week. For your system to enter the clinical pilot, you must supplement it with a retrospective report on thirty consecutive days of real-world anonymized data. Without it, the approval won't come through. The Health Commission doesn't fund lab products that only know how to run in a sandbox."

Lin Chen nodded. "Understood. The data cleaning and anonymization pipeline is ready. We'll start running the historical database tonight."

"Not the historical database." Zhou Zhen looked at him, his tone flat. "Run the outpatient logs from Provincial Second Hospital for the past three years. Anonymization standards must follow National Level III. You have seven days. The report must be on my desk by 5 PM Friday. If it's late, the pilot quota will be deferred."

Zhou Zhen turned and left. The glass door closed, leaving only the hum of the fans in the server room once again.

Su Man let out a long breath, leaning against the edge of the console. "Thirty days of real-world data, a report in seven days. He's deliberately bottlenecking our delivery schedule."

"He's not bottlenecking the schedule." Lin Chen closed the terminal window and saved the logs. "He's testing our engineering capacity. The sandbox running proves the algorithm is sound. But whether we can clean, anonymize, align, and generate a report from three years of outpatient logs in seven days determines whether we get the approval. Capital looks at performance targets, the Health Commission looks at real-world implementation. We have to deliver to both sides."

He stood up. The moment his left foot touched the ground, the numbness receded like a tide, replaced by a sharp, piercing pain. He staggered, gripping the edge of the desk, making no sound. Su Man reached out to steady him, but he waved her off and steadied himself.

"You go coordinate with the IT department at Provincial Second Hospital to apply for historical data export permissions. Once approved, immediately launch the cleaning pipeline." Lin Chen walked to the water dispenser, filled a cup with cold water, and drank it slowly. "I'll write the anonymization script. The field mapping rules for National Level III must be finalized tonight."

"Your leg won't hold up through an all-nighter." Su Man frowned.

"It will hold." Lin Chen set the cup down and walked back to his workstation. The screen's cold light flared on again, illuminating the dark circles under his eyes. "The performance agreement spans twenty-four months. The Health Commission's window is only seven days. Time waits for no one. I'll write the code, you'll run the process. In seven days, we trade the report for the approval."

Su Man looked at him for two seconds, then stopped arguing. She picked up her clipboard, turned, and walked out of the server room.

Lin Chen sat down and opened a new code editor. The sound of keyboard strikes resumed, dense, steady, without pause. He pulled up the National Level III anonymization specification document and broke down the fields item by item. Names, ID numbers, addresses, contact information, visit timestamps, diagnosis codes. Each field required a different masking strategy: hash replacement, generalization, interval blurring, complete removal. He created a new class, naming it DataAnonymizerV1.

The hospital's legacy HIS system used GB2312 encoding, with chaotic timestamp formats—some included milliseconds, others only year, month, and day. The doctors' diagnostic abbreviations were a wild assortment; "chronic bronchitis," "coronary heart disease," "glucose tolerance" all had to be mapped to ICD-10 standard codes. Lin Chen didn't rush to write the main logic. He first built an exception-capture layer. Any line that failed to parse wouldn't interrupt the pipeline; it would be written directly to an isolated queue, tagged with PARSE_ERROR, and accompanied by a raw byte snapshot. He knew all too well the destructive power of dirty data. Three years ago, taking on freelance work at a county-town internet cafe, a single full-width comma from a client could crash an entire script. Now, he no longer gambled on luck; he only left himself a way out.

The time in the bottom right corner of the screen jumped to 11:40.

His phone vibrated on the desk. Lin Chen glanced at it. It was a WeChat message from Old Zhao, just one line: "The competitor's proposal from Provincial People's Hospital has been submitted for preliminary ethics review. Don't delay your approval."

Lin Chen didn't reply. His fingers kept typing, writing the initialization parameters for DataAnonymizerV1 into the configuration file. He knew the sandbox was only the first hurdle. The real battlefield lay in the data, in the process, in that approval document seven days from now.

He opened his error log notebook and wrote on a fresh page: Real-world data retrospective. Seven days. Anonymization pipeline. Competitor pressure.

The cursor blinked at the command line. He hit Enter.

The pipeline began to start. Logs scrolled. The daylight outside fully broke through, shining into the server room and falling onto the keyboard. Lin Chen stared at the screen, his breathing steady. His left foot still throbbed with pain, but he didn't move.

The code was running. Time was running too. The next step was to let the data speak.