[Go] Genkit ignores dotprompt-defined roles

[janishorsts]

Describe the bug

When the Genkit renders the dotprompt prompt, it always uses the "user" role and ignores the dotprompt-defined roles.

To Reproduce

Use the PromptWithMultiMessage from go/samples/prompts to reproduce.

Expected behavior

The dotprompt-defined roles are retained.

Screenshots

The following screenshot of debugging the go/samples/prompts sample shows that the system prompt You are a great pirate and an AI assistant. has been added as a user message after rendering.

Runtime (please complete the following information):

• OS: MacOS
• Version 26

Go version

go version go1.25.2 darwin/arm64

Additional context

Relates to #3710

[janishorsts]

The implementation fails when a partial containing a dotprompt role is used in a dotprompt. Otherwise, without partials, it works.

For example, this fails ❌

{{>pirate}}

<<<dotprompt:role:user>>>
Say hello

Where pirate is a partial

<<<dotprompt:role:system>>>
You are a pirate

[hugoaguirre]

Hey @janishorsts thanks for the heads up. We will investigate this.