PromptX Language Support

VS Code language support for .promptx files — the prompt format used by AIEngine.

This extension remains a separate internal VS Code project. The runtime PromptX parsing/validation library lives in Libs/Zionet.Prompting, which is the private backend package.

Once installed, any file ending in .promptx is recognized as a PromptX document with syntax highlighting and inline diagnostics.

Features

• Dedicated promptx language for .promptx files.
• YAML frontmatter highlighting.
• Chat role highlighting for system:, user:, assistant:, and developer: blocks.
• Variable highlighting for placeholders such as {{question}}.
• Diagnostics for invalid frontmatter fields, invalid type values, and malformed chat role markers.

PromptX Syntax

A PromptX file has two parts:

1. A required YAML frontmatter block, delimited by --- lines.
2. A body whose shape depends on the frontmatter type.

Frontmatter

---
description: Short human-readable description of what this prompt does.
type: chat
---

Allowed fields:

The frontmatter must:

• Start on the very first line of the file with ---.
• End with a closing --- on its own line.
• Be valid YAML.

The prompt name comes from the containing folder name, and the prompt version comes from the file name (for example v1.promptx). These are not declared in frontmatter.

Body — type: prompt

The body is plain text. It may reference variables using {{name}}:

---
description: Summarize a piece of text in a target word count.
type: prompt
---

Summarize the following text in {{maxWords}} words or fewer:

{{text}}

Body — type: chat

The body is a sequence of role blocks. Each block starts with one of the following labels at column 0, on its own line, immediately followed by ::

• system:
• user:
• assistant:
• developer:

Everything until the next role label belongs to that block. Roles may repeat. Anything before the first role label must be blank.

---
description: Simple Q and A prompt with multiple role blocks.
type: chat
---

system:
You are a helpful assistant. Answer briefly and accurately.

developer:
Keep the answer concise and grounded in the prompt.

user:
{{question}}

assistant:
I can help with that.

user:
Keep the answer short.

Variables

Variables use double curly braces and a simple identifier: {{question}}, {{maxWords}}, {{text}}.

Diagnostics

The extension reports errors directly in the editor for:

• Missing or unterminated --- frontmatter delimiters.
• Frontmatter that is not a YAML mapping or contains YAML syntax errors.
• Unknown frontmatter fields (only description and type are allowed).
• Use of removed fields like name or version, with a message explaining where the value now comes from.
• Missing or invalid type value.
• Chat prompts with no role block, with role labels indented past column 0, or with unknown role labels.
• Non-blank content before the first role label in a chat prompt.

Shared Source Of Truth

The canonical PromptX schema now lives in Libs/Zionet.Prompting/Assets/Schemas/promptx.schema.json.

Keep editor validation rules in this extension aligned with that shared schema and the backend prompting library.

Not Included

The extension does not currently provide:

• Completion items or snippets.
• Comments inside the prompt body.

Build And Install

The extension is shipped as a local .vsix rather than published to the Marketplace.

Prerequisites:

• Node.js and npm.
• The VS Code code CLI on your PATH (in VS Code: Shell Command: Install 'code' command in PATH).

From the Tools/promptx-vscode folder:

npm install
npm run package
code --install-extension promptx-vscode-0.3.0.vsix --force

Then reload VS Code (Developer: Reload Window) and open any .promptx file to verify highlighting and diagnostics.

To iterate on the extension without reinstalling, open Tools/promptx-vscode as the workspace folder and press F5 to launch an Extension Development Host.