Server mod author guide

Feature flags

TaystJK gates some client-side features on recognising the server as JA+ or jaPRO. taystJKinfo is how any other game module opts in to them individually, without pretending to be either.

The problem it solves

Several client features need the server to behave compatibly because they change movement prediction, or draw something the server also decides. Rather than run them everywhere and desync, the client checks which mod the server is running and enables them only where it knows they work. The ordering that check uses, and what it costs you, is described on mod compatibility.

If your module supports one of these features but is not JA+ or jaPRO, that check would turn it off. taystJKinfo is the override.

Setting it

Put the bitmask in your serverinfo under the key taystJKinfo. The client reads it once per gamestate, alongside the rest of the server’s configstring (cg_servercmds.c):

Info_SetValueForKey( info, "taystJKinfo", va( "%i", flags ) );

Set only the bits you have actually implemented. A client that trusts a flag you do not honour will mispredict, which is worse for the player than the feature being absent.

The bits

Defined in bg_public.h:

Bit	Value	Constant	Means
0	1	`TAYSTJK_INFO_RGBSABERS`	Sabers may use colours beyond the stock set.
1	2	`TAYSTJK_INFO_BLACKSABERS`	The black saber colour is permitted.
2	4	`TAYSTJK_INFO_FLIPKICK`	Flip kicks are supported.
3	8	`TAYSTJK_INFO_GRAPPLE`	The grapple hook behaves as JA+’s.
4	16	`TAYSTJK_INFO_FIXROLL_1`	Rolling while using force grip.
5	32	`TAYSTJK_INFO_FIXROLL_2`	The above, plus chaining rolls.
6	64	`TAYSTJK_INFO_FIXROLL_3`	JK2-style rolling.

The three roll bits are alternatives rather than a progression to be combined. The client tests them from 3 downwards and takes the first that matches (bg_pmove.c).

How the client uses a flag

Each feature listed in the bit table accepts its flag in the client check. The grapple check is representative (bg_pmove.c): JA+, or jaPRO with its own grapple option set, or your flag.

Flags can also change behaviour on recognised JA+ and jaPRO servers. For example, the grapple flag enables the client path even when jaPRO’s own grapple option is off. In the roll selection above, FIXROLL_3 is tested before the server’s roll-2 or roll-1 option, so advertising it takes precedence over either lower mode (bg_pmove.c). Keep the advertised flags consistent with the server’s actual movement rules and options.

Verifying it

Connect and run serverinfo. The key appears with the value you set, and the feature should behave as it does on a jaPRO server. If the key is absent from that output, the client never received it and nothing downstream of it will work. Fix that before looking at the feature itself.

Last changed 24 September 2026 History Edit this page on GitHub