# LDC-E5403 — Two operations collide at one effective moment

## What it means

Operations on a revision edge apply in a defined order: first by their
effective moment, then by declaration order. When two operations touch the
same fragment in the same language at the same effective moment, that order
cannot decide between them, so the result would depend on an accident of
evaluation. The compiler reports the collision and leaves the edge
unapplied — give the operations different moments or merge them into one.

## Example

```law
language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

source ORDER { kind ministerial_order; }
edition ED_2025 of ORDER { language ru; officiality official; }
edition ED_2026 of ORDER { language ru; officiality official; }
fragment F_OLD in ED_2025 { kind article; locator "article/5";
  text ru official """старая редакция"""; }
fragment F_NEW in ED_2026 { kind article; locator "article/5";
  text ru official """новая редакция"""; }
revision LAW_1 {
  previous ED_2025;
  next ED_2026;
  relation amends;
  op replace { locator "article/5"; language ru; text """новая редакция"""; }
  op replace { locator "article/5"; language ru; text """третья редакция"""; }
}
```

## Fix

```law
language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

source ORDER { kind ministerial_order; }
edition ED_2025 of ORDER { language ru; officiality official; }
edition ED_2026 of ORDER { language ru; officiality official; }
fragment F_OLD in ED_2025 { kind article; locator "article/5";
  text ru official """старая редакция"""; }
fragment F_NEW in ED_2026 { kind article; locator "article/5";
  text ru official """новая редакция"""; }
revision LAW_1 {
  previous ED_2025;
  next ED_2026;
  relation amends;
  op replace { locator "article/5"; language ru; text """новая редакция"""; }
}
```

## Engine message

The engine reports this in its own wording:

```text
example.law:17:3: error LDC-E5403: edge "LAW_1": operations #0 and #1 touch article/5 (ru) at the same effective (unset) — application order is undefined (§32.1)
```

## Related

- [Time](/constructs/time/) — how editions and effective moments order amendments.
- [Sources](/constructs/sources/) — how editions carry fragment texts.