Short answer. Yes. Separation of property may be total or partial, and may cover present property, future property, or both. If you only agree to separate part of it, whatever property you did not specifically agree to keep separate still falls into the absolute community.
What the law says
Separation of property may refer to present or future property or both. It may be total or partial. In the latter case, the property not agreed upon as separate shall pertain to the absolute community.
Family Code, Article 144 — Separation May Be Total or Partial, Present or Future. Read the full provision →
Two independent choices you get to make
This article gives you flexibility along two separate dimensions at once. First, timing: separation of property may refer to present or future property or both, so you can choose to separate what you already own, what you might acquire later, or both together. Second, scope: it may be total or partial. These two choices are independent of each other — you are not forced to pick an all-or-nothing arrangement just because you are also deciding whether it covers present, future, or both kinds of property.
What happens to what you leave out
Choosing a partial separation does not simply leave the untouched property in limbo, and it does not mean it stays exclusively yours by default either. The article is specific: "the property not agreed upon as separate shall pertain to the absolute community." In other words, anything you did not expressly designate as separate falls into the community property shared between spouses. A partial separation agreement is only as protective as what it actually lists — silence on an asset does not keep it out of the community.
Precision in the agreement matters more than intent
Because the fallback for unaddressed property is the absolute community, the practical consequence of a partial separation is that your agreement needs to clearly identify exactly which property is being kept separate. An agreement that expresses a general intention to "separate our property" without being specific about which items or categories is exactly the kind of gap this article resolves against you — the unlisted property does not default to staying yours alone.
Why this is worth thinking through carefully before signing
If you are drafting or reviewing a partial separation arrangement, the value of this article is in what it warns against: assuming that anything you did not explicitly mention will be treated the way you privately intended. Whether an asset ends up separate or shared under the absolute community depends on what the agreement actually says it covers, not on what either spouse assumed was understood. A carefully itemized agreement avoids disputes later over which category a particular asset was ever meant to fall into.