info request on HL1 engine

[SamPlay]

Can anyone be so kind as to tell me where I can find info on how the engine updates the various players ( I cannot understand why my bot in god mode cannot get a headshot anytime I want it, in conditions where the weapon accuracy is of no concern).
eg: does the other players moves while your own Startframe code is running? ( do their position vary, which would require for shooting to pick their position
the latest possible before calling pfnrunplayermove)? or is everything frozen ?
Do we need to do some prediction on the other players moves , does the engine compensates in some way?
I am ready to spend some time looking through the code of another publicly available engine ( like Quake 1/ 2/ 3) but I do not know if it is relevant for HL1.

Or any paper/website/..., even not HL1 specific, explaining how an engine deals with multiplayers updates, would also be of interest.
Thanks in advance.

[Whistler]

read botman's readme.txt file included with the HPB bot, as well as the HPB bot source code and the HLSDK source code

[SamPlay]

Thanks Whistler,
I already looked at HPB files years(!) ago, looked again now and did not find what I am looking for. The HLSKD files does not include source dealing with how the engine updates players: example: pm_... tells about one player move update but not about the update process for all players which is part of source code not publicly available). The HPB source tells how Botman actually did things, but not why, which does not allow to code your own solution.

Example: from testing, I am sure that the engine updates a bot move( including changes in view angles) before executing its attack ( IN_ATTACK button flag set). This does not relate to how and when the other players are or are not updated , but it is another example of things that you cannot get anywhere though it is, I think, important to know it.