Build VS Code extension for subscription template live preview

[Smartdevs17]

Context

Developers building email and notification templates must deploy changes and trigger an email to preview the rendered output, severely slowing iteration.

Current Limitation/Problem

No local preview for templates. Developers use trial-and-error deployment to review template rendering.

Expected Outcome

VS Code extension (subtrackr-template-preview) with live template preview side panel: parse template, render with mock data, show AST tree view, and validate syntax on save.

Acceptance Criteria

• VS Code extension published to marketplace: subtrackr-template-preview
• Side panel: live preview of rendered template with mock data (auto-refresh on save)
• Variable injection: right-click variable -> edit mock value in context menu
• AST tree view: show parsed template structure in VS Code tree view
• Validation: syntax errors highlighted inline with red squiggly underline
• Partial rendering: clicking a partial reference renders it standalone
• Mock data: load from .mock.json file in project root, or use default fixtures
• Supported formats: MJML, Handlebars, and custom AST-based templates
• Edge case: template with syntax errors renders partial preview up to error location

Technical Scope

• packages/vscode-subtrackr/ - VS Code extension directory
• packages/vscode-subtrackr/src/panels/ - preview webview panel
• packages/vscode-subtrackr/src/tree/ - AST tree data provider
• packages/vscode-subtrackr/src/validation/ - linter integration
• packages/vscode-subtrackr/package.json - activation events, commands, contributes
• docs/VSCode_EXTENSION.md - usage documentation

[Glittersup]

@Glittersup has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I’m interested in handling this issue. I’ve built and tested web3 applications across contracts, backend services, and frontend flows.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Glittersup to this issue.

[Dev-Ben-Theo]

@Dev-Ben-Theo has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

hi maintainer, i would love to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Dev-Ben-Theo to this issue.

[susanyusuf]

@susanyusuf has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi @Smartdevs17,

I'd love to work on this issue. I can build the subtrackr-template-preview VS Code extension to give developers a real-time local preview of their templates i will set up the extension scaffolding in packages/vscode-subtrackr/ with activation events for MJML, Handlebars, and custom templates.Build the live preview webview panel with auto-refresh on save, supporting partial rendering and fallback partial previews when syntax errors occur.Implement the AST tree data provider to display the template structure inside the VS Code sidebar.
Integrate the linter/validator to highlight syntax errors inline with diagnostic red squiggles.
Add variable injection via context menus and load data dynamically from .mock.json files or default fixtures.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @susanyusuf to this issue.

[drips-wave]

Congratulations, @susanyusuf! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @susanyusuf: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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