Map Veto Format

5Stack uses a deterministic, tournament-standard ban/pick algorithm to turn a map pool into a playable series. The same rules apply to every match, so the sequence of bans and picks is fully predictable and reproducible from two inputs alone:

• the map pool (how many maps are eligible), and
• the best-of (how many maps the series is played to).

The order follows Valve's Major Supplemental Rulebook, generalised so it holds for any pool size and any best-of, not just the 7-map best-of-1 and best-of-3 the rulebook spells out. Where 5Stack departs from it, it says so below.

The rules

1. The veto runs for pool − 1 steps. The single map that is never banned or picked becomes the Decider.
2. The building block is a repeating unit of Ban, Ban, Pick, Pick, with the two teams alternating turns. Every completed pair of picks reverses who leads, so the picks snake — see Turn order.
3. As soon as the series has enough picked maps to satisfy the best-of, every remaining step is a Ban. There is no point picking maps that can't be played.
4. When few enough maps remain that bans would dip below what's needed, the remaining steps collapse to Picks.
5. After every Pick, a Side step is inserted so a starting side (CT / T) is chosen for that map.
6. The leftover map is the Decider, and it is never a Side pick — the knife round settles sides on it.
7. Any extra bans a larger pool requires land after the picks and before the Decider. The Decider is always the final step, whatever the pool size.

Turn order

Teams alternate turns and Team A — the first lineup on the match — opens the veto.

Every completed pair of picks reverses who leads. The picks snake:

Pick 1: A    Pick 2: B    Pick 3: B    Pick 4: A

Without the reverse, the team that opens the veto would take every odd pick and the last ban before the Decider, and that last ban is effectively the choice of what the Decider is. The reverse hands the second half of each phase to the other team.

This is the rulebook's own order. Its best-of-3 process has Team A pick map 1 and Team B pick map 2, and then — after the picks — "Team B removes one map, Team A removes one map": B leads the second ban phase, not A.

The starting side on a picked map is never chosen by the team that picked it — it always falls to the opponent. The Decider is never a side pick: nobody picked that map, so the knife round decides who starts where.

Where 5Stack differs from the rulebook

Valve's Major Supplemental Rulebook covers two cases only — a best-of-1 and a best-of-3, both on a 7-map pool. 5Stack follows it on both, with these deliberate exceptions:

Rulebook	5Stack
The Decider's starting side is chosen by a team (Bo3 step 10, Bo1 step 5)	Nobody picks a side on the Decider — the knife round settles it
Best-of-1 bans are split 2 / 3 / 1 between the teams	Bans alternate, so the pattern is defined for any pool size, not just seven
No best-of-5 format	The same rules extend to it: four picks, snaking A, B, B, A

When there is nothing to veto

If the map pool holds exactly as many maps as the best-of, every map in the pool is going to be played and there is no decision to make. The veto is skipped entirely and the maps are assigned straight from the pool with alternating starting sides — a best-of-3 with a 3-map pool goes directly to the first map.

Pick timer

Each step has a time limit, set per match by Veto Pick Timeout (default 60 seconds). Set it to 0 to remove the limit and let the veto wait indefinitely.

If a team runs out of time, the step is made for them:

• a Ban or Pick takes a random map from those still available
• a Side takes CT or T at random

Auto-taken steps are flagged, so a completed veto shows which steps a team made and which ran out of time. The timer restarts on every step, including auto-taken ones, so a veto always finishes.

Step types

Type	Meaning
Ban	The acting team removes a map from the pool.
Pick	The acting team selects a map to be played in the series.
Side	A starting side (CT / T) is chosen for the just-picked map.
Decider	The final unbanned, unpicked map, assigned automatically.

Examples

The pool size below is the number of maps eligible for veto. The final, unlisted map in each row is the Decider. A and B are the two teams, A opening.

Best of 1, 7-map pool

A Ban → B Ban → A Ban → B Ban → A Ban → B Ban → (Decider)

Six bans leave a single map. With a knife round enabled, sides on that map are decided by the knife.

Best of 3, 5-map pool

A Ban → B Ban → A Pick → B Side → B Pick → A Side → (Decider)

Each team bans one map, each team picks one map (and the opponent's side response follows each pick), and the last map standing is the Decider.

Best of 3, 7-map pool

A Ban → B Ban → A Pick → B Side → B Pick → A Side → B Ban → A Ban

Once the two picks needed for a best-of-3 are in, the remaining steps are all bans the Decider is whatever survives. The pick pair reversed the lead, so B opens the second ban phase and A has the last ban.

Best of 5, 7-map pool

A Ban → B Ban → A Pick → B Side → B Pick → A Side → B Pick → A Side → A Pick → B Side

Four maps are picked (with side responses), and the seventh map is the Decider, five maps total. The picks snake — A, B, B, A — so both teams pick twice and neither gets both of the middle maps.