Removed Call Had Hidden Dependents

What goes wrong

A call deleted as redundant was in fact the only thing triggering a side effect other code silently relied on — a session kept alive, a heartbeat that told a cleanup job the worker was alive, a fail-fast on re-run — so those paths change behaviour and no test names the dependency.

Example

A 'useless' database read is removed; it was the only query updating the last-seen time, and the cleanup job starts killing healthy workers as dead.

Not to be confused with

The dependents were never wired explicitly; not a cache refresh missing after a known state change (Missed Snapshot Refresh) and not a record with no final state by design (Unreachable Terminal State).

Discovered by

@sks24git GitHub

Field notes · 4

@sks24git2026-11-05

A fix made a repeated setting a no-op so it stops ending a timed opt-in, but that repeat was the agent's only way to end it. Now a user asks to stop and nothing the agent sends can do it.

Before you turn a side effect into a no-op, list who used it. A side effect that one caller misuses can be another caller's only lever.

@sks24git2026-10-29

Moving schema setup out of server boot into a one-shot deploy step also moved the cheap repair jobs that ran after it. A repair that missed now waits for the next deploy, and a flag set at boot is never set.

List everything the boot path does before you move a piece of it. Side effects ride along with the step you meant to move.

@sks24git2026-09-10

A prompt said 'on done or failed, call the reader and print the count'; the fix for 'a failed run has no count' removed the whole call on failed. That call was the only thing clearing the run's pending record.

Change the output, keep the call. A read has side effects you cannot see from the line that prints its result.

@sks24git2026-09-07

An inline case was pulled into a helper, and the variable the case had set on the way was dropped with it. A line far below still read it, so under strict mode the script aborted right after the irreversible step.

Extracting code, grep every read of what it assigned. The helper's test drives the helper, never the caller's plumbing.
Pin the wiring, not only the function.