Clear touches one copy of several

What goes wrong

The same fact is held in more than one place, and the operation that clears or updates it knows about only one of them. The untouched copy survives and keeps governing behaviour. Readers trust that a single reset means the state is gone everywhere.

Example

A sign-out clears the session from the shared store, but a copy kept in memory still answers checks, so the next request is treated as signed in.

Not to be confused with

Not Fix applied to one copy only, which is about the same logic duplicated in two code paths; here one write path runs correctly and leaves a second store of the same fact untouched.

Discovered by

@sks24git GitHub

Field notes · 8

@sks24git2026-11-05beat 1 review round

A new column copied user data, and only the new code's erase cleared it. An account deleted by an old server mid-rollout keeps that copy for good, since nothing later scrubs it.

Every new copy of user data needs a scrub old code can't skip. Rollouts mix writers.
Test a copy against its source when they differ. Equal fixtures hide which one you read.

@sks24git2026-11-04

An invoice copies the seat count at issue, but the month's debt uses the count in force that month. Raise the count after issue and the client pays in full, yet the month stays short and the account freezes.

Price a bill from the same source as its debt. Two copies of one number drift.
Decide what an open bill does when inputs change. Re-price it or block the change.

@sks24git2026-11-03beat 2 review rounds

A web form kept a privacy promise by sending it back on submit, but a refused post redrew the form from the current setting. The second try then went public, though the page had said private.

Store a promise, never re-derive it. A value rebuilt each render forgets what the last one said.
Keep side reads off shared pages. An optional lookup that throws breaks every form on it.

@sks24git2026-10-31

A third install mode rewrote the first two lines of a command block but kept a line an earlier step had appended for the old tool. The page showed three lines and promised they travel together, while copy took only one.

When a mode rewrites a block, rewrite all of it. Lines other steps appended outlive your edit.
Test every switch order, not just the one you built. The new path back is where state leaks.

@sks24git2026-10-28

A gate asked clients of one export format for missing balances, then skipped that format in the branch that checks them. The client supplies the numbers and stays blocked forever.

Trace the asked-for input to the branch that uses it. A request nobody consumes is a dead end.
Build test fixtures with the real variant. A helper on another format hides the gap.

@sks24git2026-10-25

A new shortcut sent signed-in visitors straight past a page, and only read a code from the link. A code parked earlier in a cookie was waiting for the step the shortcut now skips, so it was never applied.

When a shortcut skips a step, list what that step consumed. Every input it read now needs a new home.

@sks24git2026-09-21beat 2 review rounds

A one-line 429 parser grew a guard so the periodic probe could not undo it, and each review round found the guard right on one pod and wrong on the next seam. Three rounds in, the guard shipped dark.

Precedence between two state sources is a feature. Prove every writer and exit before code.
Three blocking rounds means stop. Ship the stable half; ticket the rest from the cause.

@sks24git2026-09-10

The trigger dated only a change of the period, so arming the switch where the period was set long ago left the start date stale. The floor was already past, and arming would expire every long-silent account at once.

Date the edge that arms, not only the edge that changes the value. A start date older than the arming protects nobody.
Check the doc that claims the hole is closed.