From 6b95a23606d5b27fd8c1f92d76ed8d23a555eefc Mon Sep 17 00:00:00 2001
From: Evan <evanpelle@gmail.com>
Date: Sat, 27 Jun 2026 11:10:47 -0700
Subject: [PATCH] Fix anonymize-names desync: seed cluster-recalc offset from
 id() not name() (#4426)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

## Description

Fixes a hard desync that hit anonymous-names lobbies (e.g. the OFM
tournament): in an anonymized FFA, roughly half the clients desynced.

### Root cause

`PlayerExecution.init()` seeded the per-player phase offset that
schedules `removeClusters()` from the player's **username**:

```ts
this.lastCalc = ticks + (simpleHash(this.player.name()) % this.ticksPerClusterCalc);
```

`removeClusters()` is not display-only — it both sets
`largestClusterBoundingBox` (read by `AiAttackBehavior` for targeting)
**and removes disconnected/surrounded territory, mutating tile
ownership**.

The anonymize-names option (#4318) sends each client a *different*
username for the same player (`anonName(target + viewer)`). So
`simpleHash(name()) % 20` differs per client → `removeClusters()` runs
on different ticks per client → `numTilesOwned()` diverges → the
every-10-tick state hash (`simpleHash(id) * (troops + numTilesOwned) +
units`) diverges → **desync**.

**Why only half the lobby:** clients granted real-name reveal (host /
admins / casters via `nameReveals` / `nameRevealPublicIds`) all see real
names, compute identical offsets, and stay in sync with each other and
the server record. Every non-granted (anonymized) client sees a unique
random name per player and diverges. Hence the clean split.

This line has been latent and harmless since 2024 (`f01949f0`) because
`name()` used to be identical on every client; #4318 was the first
feature to feed a per-client value into the core. The PR comment in
`GameServer.ts` even states the assumption — *"username … neither of
which the simulation reads"* — which turned out to be false.

### Fix

Seed the offset from `id()` instead of `name()`. Player `id()` is
assigned from a `gameID`-seeded PRNG by spawn order, so it is identical
on every client while still spreading cluster recalculation across
players (the line's original load-balancing intent). One-line sim
change; no schema/wire change.

### Verification / scope

- Audited every `name()`/`username` read in `src/core/`: this was the
**only** state-affecting one (all others are `console.log` / error
strings / display-only update fields). So this closes the whole desync
class.
- Confirmed player order, ids, config, `clanTag`/`friends` and cosmetics
are all client-identical under anonymize-names — `username` was the sole
per-client field reaching the sim.
- Swept the other recent core commits (impassable terrain, rail network,
nations AI, inline sfc32 PRNG, troop/economy changes) for independent
determinism regressions — none found.

### Follow-up

`name()` should be removed from the core `Player` surface entirely so a
per-client username can never re-enter the sim again (the remaining
reads are logging + the display payload the renderer needs). Tracked
separately.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
---
 src/core/execution/PlayerExecution.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/core/execution/PlayerExecution.ts b/src/core/execution/PlayerExecution.ts
index 5742f2d9d..9b123a1e9 100644
--- a/src/core/execution/PlayerExecution.ts
+++ b/src/core/execution/PlayerExecution.ts
@@ -41,7 +41,7 @@ export class PlayerExecution implements Execution {
     this.map = mg.map();
     this.config = mg.config();
     this.lastCalc =
-      ticks + (simpleHash(this.player.name()) % this.ticksPerClusterCalc);
+      ticks + (simpleHash(this.player.id()) % this.ticksPerClusterCalc);
   }
 
   tick(ticks: number) {