Anuken/Mindustry · error · ArcRuntimeException

Rules too long

Error message

Rules too long

What it means

readRules() reads JSON-serialized Rules from a Reads stream. It reads a 4-byte length and throws ArcRuntimeException if it exceeds 100_000 bytes. The cap protects the client (rules arrive on connect) from a hostile or buggy server's oversized payload.

Source

Thrown at core/src/mindustry/io/TypeIO.java:928

    public static void writeMarkerControl(Writes write, LMarkerControl reason){
        write.b((byte)reason.ordinal());
    }

    public static LMarkerControl readMarkerControl(Reads read){
        return LMarkerControl.all[read.ub()];
    }

    public static void writeRules(Writes write, Rules rules){
        String string = JsonIO.write(rules);
        byte[] bytes = string.getBytes(charset);
        write.i(bytes.length);
        write.b(bytes);
    }

    public static Rules readRules(Reads read){
        int length = read.i();
        //this is only called clientside, but the byte limit is reasonable either way...
        if(length > 100_000) throw new ArcRuntimeException("Rules too long");
        String string = new String(read.b(new byte[length]), charset);
        return JsonIO.read(Rules.class, string);
    }

    public static void writeObjectives(Writes write, MapObjectives executor){
        String string = JsonIO.write(executor);
        byte[] bytes = string.getBytes(charset);
        write.i(bytes.length);
        write.b(bytes);
    }

    public static MapObjectives readObjectives(Reads read){
        int length = read.i();
        if(length >= 60_000) throw new RuntimeException("Objectives bytes too long: " + length);
        String string = new String(read.b(new byte[length]), charset);
        return JsonIO.read(MapObjectives.class, string);
    }

View on GitHub (pinned to f695ad7e60)

Solutions

1. Reduce rules complexity/mods so serialized Rules stays under 100KB.
2. If you are the client hitting this on a server you do not control, the server is hostile or buggy — leave the server.

// Before writing rules, check serialized size against the read cap.
String json = JsonIO.write(rules);
if(json.getBytes(java.nio.charset.StandardCharsets.UTF_8).length > 100_000){
    throw new IllegalStateException("Rules JSON too large");
}

try { Rules r = TypeIO.readRules(read); }
catch(ArcRuntimeException e){ Log.err("Rules payload too large", e); /* disconnect from server */ }

When it happens

Trigger: A rules packet whose int length field exceeds 100_000.

Common situations: A heavily customized gamemode or mod that inflates Rules JSON; a malicious server; corruption.

Related errors

• Invalid array size: {}
• Invalid array size:
• Queue too long:
• Too many plans:
• Objectives bytes too long:

AI-assisted analysis of Anuken/Mindustry@f695ad7e60 (2026-08-14). Data as JSON: /api/errors/6c3d2902978b23a3. Report an issue: GitHub.