Agent Skills, and a version conflict nobody resolved

Skills are packaged capability: instructions and resources you hand the model so it can do a specific job well, without you stuffing all of it into a system prompt on every request. Think of it as extracting a fat inline prompt into a module the model imports when it needs it, rather than pasting the whole thing into every call. On the exam this sits under Agentic Customization, and there are two facts in it that are pure recall.

Two headers, and they are not optional

Agent Skills needs both of these:

• skills-2025-10-02
• code-execution-2025-08-25

Two headers. Skills leans on code execution, so you are opting into both betas at once, and forgetting the second one is a plausible exam question because it looks like an unrelated feature. It is the same shape as a peer dependency: the thing you asked for does not work until you have also installed the thing it quietly relies on, and nothing in the name of the first tells you about the second.

The conflict, stated plainly

Here is where the documentation stops agreeing with itself, and you should carry the disagreement rather than a resolution.

The skills guide's own example uses code_execution_20250825.

The tool reference lists code_execution_20260521, code_execution_20260120 and code_execution_20250825, all as GA.

Nothing states which version Agent Skills actually requires. The beta header says 2025-08-25, and the guide's example says 20250825, which is suggestive. It is not a statement. Beta headers and tool versions are separate axes, and "these two numbers match so one must imply the other" is an inference dressed up as a fact.

What to do with an unresolved conflict

Two different answers depending on where you are.

Writing code: pin what the guide's example uses, code_execution_20250825, and leave a comment saying why, because the next person will look at the three GA versions and assume you picked the oldest by accident.

Sitting the exam: if a question forces a single version, the guide's example is the most defensible thing to reach for, because it is the only place the two features appear together. But notice that you are reasoning under ambiguity rather than recalling a fact. That difference matters, because it changes how long you should spend before moving on.

The habit worth building is spotting the seam at all. Three GA versions of the same tool means the version is a live parameter someone chose, not a constant, and a course that told you "it's _20250825, done" would be teaching you a confidence the docs have not earned.

{
  "headers": {
    "anthropic-beta": "skills-2025-10-02,code_execution_20250825"
  },
  "tools": [
    { "type": "code_execution_20250825" }
  ]
}