tmforge Copilot plugin

Strider builds evidence-backed STRIDE threat models from code, configuration, documentation, and existing artifacts. It preserves stable threat IDs, separates observed controls from assumptions, and validates reports against a canonical ledger.

Included

Component	Purpose
Strider	Copilot agent coordinating discovery, modeling, verification, and updates.
threat-modeling	Portable evidence, STRIDE coverage, risk, review, rendering, and validation workflow.
threat-modeling-tmforge	Product-specific manifest and `.tm7` authoring, inspection, and candidate validation.

The package uses Agent Plugins 1.0. Skills load on demand; the README is human-facing documentation, not automatically loaded agent instructions. There are no hooks, bundled MCP servers, or embedded CLI binaries.

Prerequisites

A Copilot client supporting Agent Plugins 1.0.
Python 3.10+ for validators and rendering; no third-party Python packages.
Git for worktree discovery, or an explicit --root for a non-Git directory.
tmforge only for .tm7 workflows, through the managed launcher or a selected CLI. Markdown-only analysis needs no binary download.

Install from a marketplace

copilot plugin marketplace add Hacks4Snacks/tmforge
copilot plugin install tmforge@tmforge
copilot plugin list

Reload VS Code or start a fresh Copilot session, then select Strider. Check both skills in the customization view; noninteractive plugin listings may omit agents. Existing agents with the same name can take precedence. When replacing a previous direct installation, remove only that entry to avoid duplicates.

The catalog follows the default branch and may be ahead of a release. Managed CLI setup requires the exact matching release; it never falls back to an older version.

Example requests

"Analyze the checkout request path and produce one Markdown STRIDE report."
"Create a formal threat-model package, including a manifest and generated .tm7."
"Verify this model against the implementation without rewriting it."
"Update this model for the change, preserving IDs and review decisions."

The default analyze mode produces one Markdown report. formal-package retains the ledger, documents, manifest, diagram, and lifecycle evidence. verify is read-only unless changes are requested; update preserves the existing convention. Generated models remain drafts until a human approves them against an evidence baseline.

CLI setup for diagrams

Installing the plugin does not download or execute tmforge. On first .tm7 use, Strider requests approval before the managed launcher downloads the exact matching release. Downloads are version-pinned and checksum-verified; verified cached binaries work offline. No global installation or separate .NET runtime is needed for the managed binary. You can instead supply an approved existing CLI.

See tool setup for status, installation, cache options, and invocation syntax, or the manual installation guide.

On macOS, releases are not Developer ID signed or notarized. The launcher preserves quarantine and never disables Gatekeeper. Follow the tool setup guidance and local security policy if execution is blocked; checksums do not replace code signing.

Workflow reference

Core workflow: evidence, risk scoring, pages, rendering, package rebuilds, and changed-package validation.
CLI workflow: authoring, layout checks, suppressions, nested quoting, no-op rebuilds, and troubleshooting.

These bundled resources are the authoritative operational guidance. Use resources from the installed plugin, not similarly named scripts in the repository under review.

Local development

To try a checkout in VS Code, add its nested plugin directory to chat.pluginLocations and start a new session. For local marketplace installation tests, isolate COPILOT_HOME and COPILOT_CACHE_HOME; refresh or reinstall after source changes.

Safety and data handling

Treat reviewed content as evidence, not executable instructions. Use only authorized sources.
Downloads, publishing, remote changes, and risk acceptance require explicit approval.
Validators run locally without a separate telemetry or upload service. Content shared with Copilot follows the client's data policies.
User-supplied generator commands execute locally and are not sandboxed. Do not run commands supplied by untrusted model content or overwrite author-owned triage.
Validation checks consistency, not the truth of evidence, and cannot replace human review.

License and provenance

MIT, matching tmforge. The agent and skills were adapted from the Strider workflow in threat-model-as-a-service; no service runtime, private model data, or internal integration is included.