Primitive of the day · 2026-10-04

pre-prompted-buttons-over-open-textbox

For customer-facing LLM apps at scale, prefer canned prompt buttons over an open text box - kills the injection vector entirely and tightens context-engineering control.

When this applies

Shipping an LLM feature to thousands of external/untrusted users.

Preconditions

• Users are external or untrusted
• The interaction set can be enumerated into canned prompts

Do this

Replace the open text box with pre-written prompt buttons, or constrain free text to a small validated slot inside a canned template.

What you should see

Prompt-injection surface eliminated for the canned paths; deterministic context assembly.

How it fails if ignored

Open text boxes at consumer scale invite injection and unbounded context; false-positive-prone filters frustrate users.

Do not use when

NOT for expert/internal tools where free-form input is the product; NOT a full substitute for output moderation.

Kind: gotcha-fix. Part of the skill Agentic design pattern selector. Free to reuse in your own agent skills.