Open WebUI prompt variables: reusable task forms

A reusable prompt is useful when the task stays recognizable but its inputs change. Open WebUI can turn that pattern into a slash command with input fields. This is a way to prepare a model request, separate from choosing the model, provisioning inference or configuring a tool that acts on the resulting text.

Create a task template in Workspace

The Prompts guide places creation in Workspace, Prompts and the Create action. Give the template a meaningful name and command. Keep the instruction focused on the task that remains constant rather than embedding a sample input that users must remember to remove.

For an engineering summary, the stable part can request the changed behavior, affected component and unresolved question. The changing part is the source material supplied by the user. Avoid a template so broad that every run needs an unrelated conversational negotiation before it becomes useful.

Distinguish fields from system substitutions

Custom variables can collect typed user input; system variables substitute values supplied by the application. A date supplied by the system and a release date entered by the user are not the same fact. Name them so a reader can see the distinction in the resulting prompt.

The documented syntax includes {{summary | text:required}} for a required text field. A textarea is more appropriate for a long source passage. Test the form with an omitted required value and with an explicitly empty optional field. A default is a chosen input, not proof that the user confirmed its meaning.

Keep the template separate from a model wrapper

The Workspace overview distinguishes Prompts from Models, Knowledge and Skills. A slash-command prompt prepares instructions for a conversation. It should not be described as installing a new model or fine-tuning weights.

The Models documentation describes reusable wrappers with their own instructions and attachments. Check how the selected wrapper and inserted task template interact. If both specify an output format, keep the relationship intentional instead of relying on whichever instruction appears most persuasive to a particular model.

Test a realistic input form

Create a release-note task with a required summary and optional evidence passage. Run it with a concise input, a long passage and text containing punctuation or template-like braces. Inspect the expanded request as well as the final response.

Check that the input appears in the intended location and that labels make sense without reading the template source. If an optional passage is absent, the instruction should remain grammatical and should not ask the model to invent evidence that the form never supplied.

Manage versions and sharing deliberately

The prompt documentation describes version history and sharing controls. Review a changed template before making its new content the active version. A command rename and a content revision need not have the same version behavior.

Keep a small set of sample inputs for regression review when the template changes. Also review the actual access scope before making a prompt public within an instance. A shared task form is useful when its wording and inputs are understandable to other users; it does not authorize them to read another person’s documents or execute an unavailable tool.

Related reading

vLLM served-model-name: Fix a Missing API Model, llama.cpp server: a local API from a GGUF model.