Ark Nova · Board game rules
Can I regain an x-token if I start my turn with five and use one?
Quick answer
Yes — spending an X-token frees up space under the 5-token cap, so you can gain a new one later that same turn (or afterward) as long as you don't exceed 5 total.
Details
X-tokens are used to increase the strength of an action: for each token you spend, the action's strength increases by 1, and the token is returned to the general supply [p.8 — A Turn / The 5 Action Cards]. The rulebook states you can never have more than 5 X-tokens at any time [p.8 — A Turn / The 5 Action Cards].
Since spending a token returns it to the supply and reduces your total below 5, there is nothing preventing you from later gaining another X-token (for example via the dedicated X-Token action, a Bonus tile, or another card effect) up to the cap of 5 again [p.8 — A Turn / The 5 Action Cards][p.18 — X-Token Action]. The X-Token action itself explicitly states you cannot perform it if you already have 5 tokens, implying you can perform it whenever your total is below that cap [p.18 — X-Token Action].
Watch out: You must set the strength of an action before performing it, and you cannot use X-tokens gained during that same action to further increase its strength — but this restriction is about timing within a single action, not about whether you can regain tokens afterward [p.8 — A Turn / The 5 Action Cards].