Zombie Code: Why Deleted Features Keep Coming Back
You removed a button last week. Today it’s back, and it even works—bad news, because you retired that flow for a reason. In AI‑first development, old code can resurface when the AI leans on earlier context, copies from a similar screen, or tries to “help” by restoring something it believes you still want. This is zombie code: features that should be gone but keep returning.
How zombie code shows up
The signs vary. An old route becomes reachable again from a new menu. A form you replaced appears in a different section with the same old rules. A retired email still sends when a rare action fires. From a user’s point of view, this feels like the product cannot make up its mind, which hurts trust and encourages churn.
Why AI brings old features back
Vibe‑coding depends on natural‑language prompts and fast generation. If your project contains a mix of new and old patterns, the AI may rely on examples it has already seen in your files. When you ask for “a page like the previous one with fewer fields,” it might revive the original while trying to keep your request. Without clear instructions about what must stay deleted, the safest guess is to reuse what exists.
Make retirements explicit
Prevent zombie code by treating deletions as decisions the AI can understand. Name the feature, say it is retired, and point to the replacement if one exists. Do this in the code, in a short note for yourself, and in your next prompt.
- Add a brief comment or note near the replacement that says “Replaces old X; do not reintroduce”
- Remove dead links from navigation and any unused routes that expose old flows
- Keep a small “retired features” list in your one‑page plan with dates and reasons
This creates a trail that both you and the AI can follow.
Write prompts that close doors, not just open them
When you ask for a change, state what must remain gone. You can be friendly and firm at the same time.
Examples that work:
- “Replace the legacy Invite flow with the new Share Link screen. Remove the Invite route and do not re‑add it elsewhere.”
- “Use the new Payment page and delete the old card form. Do not restore the old form in the checkout modal.”
- “Keep the Dashboard as the home page. Do not bring back the old Overview route.”
Clean up the roots so nothing grows back
Zombie code often lives in small places—an unused helper, a hidden link, a leftover email template. Set aside a short window each week to search for old names and flows, then remove or redirect them. If you find a test or a snippet that refers to retired behavior, update it to point at the new feature. Few things build confidence like being able to say, “that path no longer exists.”
Keep the promise you make to users
When you retire a feature, you make a promise about how the product will behave. Keeping that promise keeps people’s trust. By stating retirements clearly, guiding AI app generation with specific prompts, and pruning leftovers, you prevent old ideas from haunting your app and you keep focus on what users actually need.
If you keep seeing retired flows resurface and want outside help to close those doors for good, Spin by fryga offers hands‑on rescue work for vibe‑coded and no‑code apps so the past stays in the past.