Threat Model Forge (tmforge)

The open, cross-platform successor to the Microsoft Threat Modeling Tool: threat modeling as code, in your browser, your terminal, and your CI pipeline.

The Microsoft Threat Modeling Tool (MTMT) is Windows-only, GUI-only, and can't run in a pipeline. Threat Model Forge keeps its file format, reading and writing .tm7 files byte-for-byte unchanged for native no-op saves, while preserving unrelated native content when editing. Author models in browser or VS Code Studio or a headless CLI, diff and merge them like source code, analyze them against built-in security and hygiene rules, and gate a build on the result. No Windows, no GUI required.

Try it now, no install: the full editor and validation engine run client-side (WebAssembly) at hacks4snacks.github.io/tmforge. Model processing stays in your browser; saving, exporting, or sharing a model is an explicit action.

Why tmforge

• Keep native models native. Open and edit .tm7 without converting it to another format. No-op native saves retain the source bytes; edited saves preserve unrelated native content but may change XML formatting. Fidelity and limits are documented per format.
• Threat modeling as code. Models live in git like everything else: semantic diff, a three-way merge driver, declarative apply/export manifests, and --json output with a stable, versioned envelope on supported model commands for scripts, pipelines, and AI agents.
• CI-grade validation. Rule packs for core hygiene, STRIDE completeness, input validation, data protection, transport security, and identity & access, with SARIF + HTML reports and a distinct exit code for "found issues" you can gate a build on.
• One engine across tools. Browser Studio, VS Code, a scriptable CLI with MCP tools, and a versioned HTTP API share the same .NET engine.
• Multi-format. Import/export draw.io and Visio (.vsdx) alongside .tm7 and a canonical JSON wire format; import bounded subsets of Threat Dragon, Mermaid, and Graphviz DOT.
• Zero-runtime install. Self-contained, single-file binaries for six platforms, or one container for the API + Studio.

Try it

In the browser (no install): open hacks4snacks.github.io/tmforge and start drawing.

Self-hosted: run the published engine API + Studio image (or build it yourself):

docker run --rm -p 127.0.0.1:8080:8080 ghcr.io/hacks4snacks/tmforge  # http://localhost:8080/

The API has no built-in authentication. Read the security posture before exposing it to other users.

In VS Code: install Threat Model Forge (hacks4snacks.tmforge), or install the release VSIX, then open a .tm7 or .tmforge.json file. See the extension guide.

In the terminal: with tmforge on your PATH (see Install):

tmforge new payments.tm7 --name "Payments"
tmforge add process payments.tm7 --name "Checkout API"
tmforge add store payments.tm7 --name "Orders DB"
tmforge add boundary payments.tm7 --name "Azure VNet"
tmforge analyze payments.tm7 --max-severity warning  # exits 2 on warning/error findings
tmforge report payments.tm7 --out payments.html

New here? Start with the Quick start. Coming from MTMT? Your .tm7 files open as-is; see Formats & interoperability.

What it does

• Author & edit data-flow diagrams in the browser (the React Studio SPA): add processes, external entities, data stores, and trust boundaries; draw data flows; resize and bend connectors; organize a model across multiple pages.
• Author headlessly from the CLI (new, add, connect, set, ...) or the API, so agents and pipelines build models with no GUI.
• Preserve native .tm7 data, including templates and unaffected threat decisions during native editing.
• Version like code: semantic diff, three-way merge, and git-setup to wire both into your repo, plus declarative apply/export manifests for reproducible models.
• Convert between .tm7, tmforge-json, draw.io, and Visio.
• Import Mermaid flowcharts and Graphviz DOT as starter models with explicit mapping assumptions.
• Import and export OWASP Threat Dragon v2 JSON with stable imported identities and authored threats. The bounded subset supports rectangular boundaries and directed flows; unsupported content is refused with a specific reason.
• Report to self-contained HTML (with inline SVG diagrams), or render the diagram right in your terminal.
• Analyze in CI with the tmforge CLI (tmforge analyze), gating builds on SARIF-reported findings.
• Model with Copilot using the Strider plugin: evidence-backed STRIDE analysis, deterministic reports, and optional .tm7 authoring. Install through the tmforge marketplace; Markdown-only analysis does not require the CLI.

Documentation

Full user documentation lives in docs/:

• Overview & features · Quick start · Installation
• CLI reference · Studio guide · Engine API reference
• Formats & interoperability · Analysis rules & CI · Deployment

Install

Prebuilt, self-contained tmforge binaries (no .NET runtime required on the host) are attached to each GitHub Release for six platforms:

OS	x64	arm64
Linux	tmforge-<ver>-linux-x64.tar.gz	tmforge-<ver>-linux-arm64.tar.gz
macOS	tmforge-<ver>-osx-x64.tar.gz	tmforge-<ver>-osx-arm64.tar.gz
Windows	tmforge-<ver>-win-x64.zip	tmforge-<ver>-win-arm64.zip

# Linux example; select the version and RID for your platform.
base=https://github.com/hacks4snacks/tmforge/releases/download/v0.12.0
curl -fsSLO "$base/tmforge-0.12.0-linux-x64.tar.gz" &&
curl -fsSLO "$base/checksums.txt" &&
grep -F '  tmforge-0.12.0-linux-x64.tar.gz' checksums.txt | sha256sum -c - &&
tar -xzf tmforge-0.12.0-linux-x64.tar.gz &&
./tmforge-0.12.0-linux-x64/tmforge --version

Each release also ships checksums.txt (SHA-256) and release-metadata.json. Verify the downloaded archive before extracting or executing it.

Platform notes. Linux binaries target a glibc baseline (not musl/Alpine). macOS binaries are not code-signed or notarized. Follow the platform notes if macOS blocks a verified download; changing Gatekeeper policy is not a prerequisite.

Prefer a runtime-present install? Use the container image or the RID-agnostic global tool (dotnet pack -p:PackTools=true).

Build & test

Requires the .NET SDK pinned in global.json and Node.js 22.12+ with npm for Studio. Use -p:BuildStudio=false for a .NET-only build/test loop; that does not build the browser UI.

dotnet build dirs.proj
dotnet test  dirs.proj --no-build

The build system is MSBuild + Microsoft.Build.Traversal; central package versions live in Directory.Packages.props; shared build settings in Directory.Build.props. Output goes to out/<Config>-<Platform>/.

Containers

Pull the published multi-arch images from GitHub Container Registry:

# Engine API + Studio SPA (React): the /v1 API serves the SPA at /
docker run --rm -p 127.0.0.1:8080:8080 ghcr.io/hacks4snacks/tmforge  # http://localhost:8080/

# CLI tool
docker run --rm -v "$PWD:/work" ghcr.io/hacks4snacks/tmforge-cli analyze model.tm7

Published tags include latest, the release version (e.g. 0.12.0), 0.12, and edge (latest main). Prefer to build locally?

docker build -f build/Dockerfile.api -t tmforge .        # API + Studio
docker build -f build/Dockerfile -t tmforge-cli .        # CLI

Both Dockerfiles build from the repo root and target the real src/ layout.

Repository layout

docs/              Project documentation
build/             Dockerfile (CLI) + Dockerfile.api (engine API + Studio SPA)
src/               shared libraries, CLI/MCP, engine API, browser Studio, and VS Code extension
test/              one *.Tests project per shipping library

ThreatModelForge.slnx lists every project for IDE users; the build is driven by dirs.proj (Microsoft.Build.Traversal), which fans out to src/dirs.proj and test/dirs.proj.

Security

Report vulnerabilities privately using the security policy. For shared hosting, read the API security posture.

License

MIT.