Ask HN: Any active COBOL devs here? What are you working on?

Met one close to retirement who worked on a ERP system in the food processing industry. Nightly batch jobs would trigger orders from their suppliers, customer service would enter new orders. Two SAP migrations already failed, costing the company millions. All company process knowledge was in code, database fields have been repurposed (but no renamed, too much work), feature development stop long time ago. In parallel a new system was built in-house (no longer trusting external consultants) and his job was explaining what the system does. Probably well paid but he didn't seem to care, he just wanted to work less and retire on good terms.

I grew to like migration projects like that.

Currently working on migration of 30yo ERP without tests in Progress to Kotlin+PostgreSQL.

AI agents don’t care which code to read or convert into tests. They just need an automated feedback loop and some human oversight.

I would argue that they need heavy human oversight

For sure; I'll believe that an AI can read and "understand" code, extract meaning and requirements from it, but it won't be the same as a human that knows requirements.

Then again, a human won't know all requirements either; over time, requirements are literally encoded.

In systems like that you can record human interactions with the old version, replay against the new one and compare outcomes.

Is there a delta? Debug and add a unit test to capture the bug. Then fix and move to the next delta.

I quickly worked at a company like that, that had large parts of their core business logic running on an AS400, and they were asking what they need to do to migrate to something newer - was surreal. A few hundred employees all interacting with the system - in building A, a deliver arrives, they scan it like this, press this button. Building B, a guys job was to oversee the conversion of tables from As400 to a csv format suitable for some other outsourced software. Data goes into system C and shows to employees working on conveyor belts this and that. Hundreds of kilometers away, truck drivers get a notification for this and that.b

And, nobody knew how the whole worked. Everyone has their niche of interaction with the system. They would be able to shave off an insane percentage off expenses (in the form of employees whose job exists for no real reason), but the switching costs would also be immense.

I sometimes wonder what came of their company. The system was so far beyond the complexity that anyone could grasp, they had no inhouse devs, they'd need people with the competency to judge which competency they need.