If prec_mode 1 is record all games then you could just do prec_start in your soldier config

Thanks, but when I tried the prec commands they don't seem to be supported, as supported commands should be auto-completed or given suggestions right? Is there a website where I can check all available commands?

in cfg/ you can make 9 files: scout.cfg, soldier.cfg etc (heavy is heavyweapons.cfg). whenever you select that class the corresponding cfg file is executed, so you can put prec_mode 3 in medic.cfg and prec_mode 1 in soldier.cfg. bear in mind that you need to put a default value for prec_mode in all other cfgs otherwise if you swap to medic/soldier and back it would still be at that value

Sorry for not explaining well, but I do understand and is editting the class cfgs. The problem is since TF2 is now using its own demo recording, it does not seem that PREC settings like prec_mode are even supported in the game. Therefore I am not sure how to set the corresponding preferences directing in script instead of going through the control panel.

prec still works, but obviously stops you from using matchmaking and casual. you'd need to make sure prec is installed in custom before using prec commands

i understand the question now though, valve demo system commands start with ds_

[spoiler]] find ds_
"ds_enable" = "0" min. 0.000000 max. 3.000000
client archive
- Demo support - enable automatic .dem file recording and features. 0 - Manual, 1 - Auto-record competitive matches, 2 - Auto-record all matches, 3 - Auto-record tournament (mp_tournament) matches
"ds_dir" = "demos"
client archive
- Demo support - will put all files into this folder under the gamedir. 24 characters max.
"ds_prefix" = ""
client archive
- Demo support - will prefix files with this string. 24 characters max.
"ds_min_streak" = "4.000000" ( def. "4" ) min. 2.000000
client archive
- Demo support - minimum kill streak count before being recorded.
"ds_kill_delay" = "15.000000" ( def. "15" ) min. 5.000000
client archive
- Demo support - maximum time between kills for tracking kill streaks.
"ds_log" = "1" min. 0.000000 max. 1.000000
client archive
- Demo support - log kill streak and bookmark events to an associated .txt file.
"ds_sound" = "1" min. 0.000000 max. 1.000000
client archive
- Demo support - play start/stop sound for demo recording.
"ds_notify" = "0" min. 0.000000 max. 2.000000
client archive
- Demo support - text output when recording start/stop/bookmark events : 0 - console, 1 - console and chat, 2 - console and HUD.
"ds_screens" = "1" min. 0.000000 max. 1.000000
client archive
- Demo support - take screenshot of the scoreboard for non-competitive matches or the match summary stats for competitive matches. For competitive matches, it will not capture the screenshot if you disconnect from the server before the medal awards have completed.
"ds_autodelete" = "0" min. 0.000000 max. 1.000000
client archive
- Demo support - automatically delete .dem files with no associated bookmark or kill streak events.
"ds_mark"
client
- Demo support - bookmark (with optional single-word description) the current tick count for the demo being recorded.
"ds_record"
client
- Demo support - start recording a demo.
"ds_stop"
client
- Demo support - stop recording a demo.
"ds_status"
client
- Demo support - show the current recording status.
"binds_per_command" = "1"
client
"tf_halloween_kart_impact_bounds_scale" = "1.0f"
game cheat
[/spoiler]

so the command you're looking for is ds_enable

Thanks! Never known the change before this thread.