Skip to content

Document system-prompt template variables #104

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
JakeSCahill merged 1 commit into from
Jun 18, 2026
Merged

Document system-prompt template variables #104

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
54 changes: 54 additions & 0 deletions modules/connect/pages/system-prompts.adoc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -214,6 +214,60 @@ Output format:
- Include units (dollars, kilograms) in all numeric values
----

== Template variables

The system prompt is a Go template that Redpanda renders on every invocation. Use `{{.Variable}}` expressions to inject the current date and the calling user into the prompt at request time. A prompt with no template expressions renders unchanged, so existing prompts keep working without edits. The same variables are available in agent and subagent system prompts.

=== Available variables

[cols="1,2,1"]
|===
| Expression | Description | Example output

| `{{.Now.Date}}`
| Current date, in `YYYY-MM-DD` form
| `2026-06-18`

| `{{.Now.Weekday}}`
| Current day of the week
| `Thursday`

| `{{.Now.Month}}`
| Current month name
| `June`

| `{{.Now.Year}}`
| Current year
| `2026`

| `{{.Now.Time}}`
| Raw current timestamp. Apply a Go time layout for full control, for example, `{{.Now.Time.Format "15:04 MST"}}`.
| `15:04 UTC`

| `{{.User.Email}}`
| Email of the user the agent acts for. Empty when no user is tied to the request, such as a service-account call.
| `user@example.com`
|===

All times are UTC.

=== Example prompt

[,text]
----
You are a support agent. Today is {{.Now.Weekday}}, {{.Now.Month}} {{.Now.Year}}.

You are assisting {{.User.Email}}. Scope every answer to that user's account, and do not reference other users' data.
----

=== Keep prompts cache-friendly

Model providers can cache an identical prompt prefix between requests to reduce cost and latency. The date fields, `{{.Now.Date}}`, `{{.Now.Weekday}}`, `{{.Now.Month}}`, and `{{.Now.Year}}`, hold the same value all day, so the prompt stays identical and the cache keeps hitting. Formatting a sub-day value from `{{.Now.Time}}`, such as the minute or second, changes the prompt on every request and defeats the cache. Use `{{.Now.Time}}` only when the agent needs the time of day.

=== Validate template changes

The agent parses the system prompt when it starts. A broken template stops the agent from starting rather than failing on each request, so the mistake surfaces at deploy time. Common mistakes are an unclosed `{{ }}` expression, a reference to a variable that does not exist, and a time call that returns more than one value, such as `{{.Now.Time.Clock}}`. Test the agent after editing the prompt.

[[evaluation-and-testing]]
== Evaluation and testing

Expand Down