Spec Kit Canvas Markdown Preview

Review existing Spec Kit artifacts inside the GitHub Copilot App's Spec-Driven Development canvas, with rendered Markdown, a hierarchical table of contents, related-file navigation, and return to the original workflow context.

Experimental preview, not an official GitHub release. Maintained by SwagDrivenDeveloper, based on the MIT-licensed GitHub Spec Kit Copilot integration. This repository distributes the existing SDD plugin, not a new standalone viewer canvas. Native marketplace acceptance remains a tester task.

The screenshot uses synthetic content in the actual SDD browser shell with a mocked SDK. It is not a native App installation claim or a private project image.

Component	Version / identity
Marketplace	speckit-markdown-preview / 0.1.0
Plugin	spec-kit-copilot-sdd / 0.2.0-preview.1
Existing canvas	sdd-canvas / Spec-Driven Development
Baseline upstream SDD plugin	0.1.0

Before Installing

• Use the GitHub Copilot App with plugin/canvas support, permitted by your account and organization policies. The plain terminal CLI does not render canvases.
• Have a real SDD-enabled repository with existing .specify/ configuration and specs/<feature>/spec.md files. This preview does not create or regenerate specs.
• Keep the normal core Spec Kit skills available. Node.js 24 was the tested local runtime; no npm install or reader build is required for this packaged SDD plugin.
• Record the existing SDD plugin source/version and repository state first.
• Run exactly one sdd-canvas provider. This is a full replacement SDD build, not an add-on that injects a reader into another installed provider. Safely remove or isolate a competing installed SDD plugin and any old project-local SDD development extension before installing. Leave unrelated plugins alone. Stop if your host cannot provide a supported isolated replacement scope.

The original SDD workflow controls remain present. For the initial acceptance test, use only View/navigation/return. Do not select Setup, Run, Rerun, Implement, or Submit clarification unless you separately intend to authorize that workflow.

Install in Copilot App

1. Open Customize, then Plugins.

2. Open marketplace settings next to the marketplace selector and add:

   SwagDrivenDeveloper/SpeckitCanvasMarkdownViewer
   

3. Select marketplace speckit-markdown-preview.

4. Install spec-kit-copilot-sdd, version 0.2.0-preview.1.

5. Start or refresh an appropriate test session for your existing SDD repository. Verify its effective worktree and that only the intended SDD provider is active.

6. Ask "Open Spec-Driven Development", then use the normal View action for an existing specification. Widen the panel for the permanent TOC rail; compact reader containers use a section-navigation drawer.

UI availability depends on the installed App version and policy. See GitHub's plugin installation documentation. If the old code is cached, save work and restart the App normally, then recheck the provider source. Do not add a second provider as a workaround.

CLI Installation Alternative

Use the Copilot CLI associated with the App's intended configuration:

copilot plugin marketplace add SwagDrivenDeveloper/SpeckitCanvasMarkdownViewer
copilot plugin install spec-kit-copilot-sdd@speckit-markdown-preview
copilot plugin list

Installation registers the canvas. Open it in the App, not in the terminal. No ZIP installer or project-local file copying is part of this marketplace route.

What to Test

1. Open an existing specification and verify its source path and working-tree revision.
2. Jump to a known heading using the TOC, by pointer and keyboard.
3. Visit an existing related Research/Plan/Tasks document and use artifact history.
4. Resize the panel and check the compact section drawer.
5. Return to the same dashboard feature/stage and invoking control.
6. Repeat with another existing feature. Compare repository status and source hashes.
7. Remove the preview and restore the original SDD provider/source/version.

See the test and restoration guide for safeguards and feedback.

Behavior and Limits

• Markdown/GFM, tables, lists, task states, code blocks, and scoped footnotes/headings.
• Related artifacts are workflow-scoped; this is not a general repository browser.
• Review uses the existing canvas server and event stream. Reading/navigation does not submit a model prompt, run a workflow, install dependencies, or write specs.
• Working-tree SHA-256 revisions identify exact source bytes. Changed or deleted files produce explicit refresh/unavailable states rather than silent truncation.
• Ordinary UTF-8 .md and .markdown files are limited to 5,242,880 bytes (5 MiB).
• Images are non-loading placeholders, raw HTML is disabled, and task controls are inert. Unsafe paths, link schemes, redirects, and cross-context reads are denied.
• SDD retains its immediate single-question clarification behavior, with source revalidation before an explicitly authorized submission. No Wizard batching is added.

Validation and Preview Status

The unchanged runtime has recorded local Windows tests for artifact membership, bounded reads, path/auth checks, Markdown rendering, accessibility, freshness, clarifications, independent packaging, and source preservation. The extracted preview kit passed its actual-shell browser test with a mocked SDK. The bundled reader and parser include third-party notices and hash manifests.

This does not claim a completed native marketplace installation study, live stage-output test, ten-participant usability study, production rollout, or formal update/rollback release gate. An earlier TOC build was demonstrated natively in App 1.1.20 on Windows; that is not a guaranteed minimum version for this candidate. Non-Windows native host behavior is unverified. Account/enterprise policy applies.

Package source and exact file hashes are recorded in PREVIEW-PROVENANCE.json. The runtime remains inside the existing SDD plugin; only distribution metadata and documentation differ from the verified local preview payload.

Maintenance and License

Report reproducible, redacted issues in this repository. Never post private spec text, capability URLs, access tokens, absolute private paths, or raw authenticated logs. Nothing in this preview automatically uploads feedback or telemetry; the Copilot App's own service behavior is separate.

The upstream GitHub MIT license is retained in LICENSE and the plugin's UPSTREAM_LICENSE. Bundled dependency notices are shipped alongside the reader and server parser. Preview maintenance is independent of the official project; upstream contribution and an official plugin update are separate decisions.