Tkach Security — Krosna, Zaslon, Propusk and Sled

A fail-closed security boundary for AI agents and compromised model output.

The model proposes. Tkach authorizes.

Put Tkach between model proposals and protected actions. Its Rust Core checks authority and information flow before allowing an action or releasing output. Model output remains untrusted data, even when the model is compromised.

Why Tkach

Explicit authority: protected actions need an exact-scope, Core-issued Propusk; model text cannot create one.
Controlled data flow: permission to read is not permission to export. Provenance and release checks remain inside the boundary.
Fail-closed decisions: invalid, denied, replayed, cancelled, or uncertain states do not silently become permission.
Isolated secrets and bounded evidence: broker-held secrets stay outside ordinary model context; Sled receipts do not include payloads.

These guarantees apply to paths routed through Tkach. It does not make the model trustworthy, detect every prompt injection, or protect a compromised host.

Start in minutes

Install from crates.io with Rust 1.85 or newer:

console

cargo install tkach-cli --version 0.1.2 --locked
tkach init my-agent
tkach check my-agent/.tkach/request.json
tkach run --demo

init creates a starter request without overwriting files; check validates its schema, not permission to execute; run --demo exercises the offline boundary without a model connection. Use tkach ui for the interactive panel.

Prefer no Rust toolchain? Download a binary below and start with tkach init.

Packages and downloads · v0.1.2

Channel	What you get	Install / next step
GitHub Releases	`tkach` + `tkach-mcp`; Linux x86_64, macOS x86_64/arm64, Windows x86_64	Verify downloads
crates.io	Seven Rust crates at `0.1.2`: Core, Gateway, HTTP, client, MCP, CLI, provider adapter	Package list
npm	Thin JavaScript / TypeScript HTTP client	`npm install tkach-security-client@0.1.2`
PyPI	Thin Python HTTP client	`python -m pip install tkach-security-client==0.1.2`
Official MCP Registry	`io.github.ECD5A/tkach-security@0.1.2`, local stdio	Configure MCP
GHCR	OCI image for Linux amd64 / arm64	Digest and deployment

Binary archives include SHA-256 manifests, keyless Sigstore bundles, and GitHub build attestations. Pin the OCI digest for deployment; verification details live in the distribution guide.

Integrate without moving policy out of Rust

Use the HTTP contract from your application, the Rust client, a Python/JS/TS/Go client, or the stdio adapter from an MCP client. Clients and MCP require a separately started local tkach serve runtime and its bearer token; installing a package does not enable background protection.

tkach-core stays provider-, protocol-, and language-independent. Adapters transport requests; policy and authority stay in Rust. Follow the integration guide or copy a working examples/ scenario. The Go client is a source module, not a separate registry package.

The supported runtime is loopback-only by default. Public internet serving, TLS termination, Streamable HTTP, a cloud control plane, and a generic executor are not included; see the deployment contract.

Show the cross-platform CLI window

Tkach CLI in English on WSL Ubuntu

See the boundary in action

From a repository checkout, run the offline Golden Case. It needs no model service or credentials. It performs one create-only write inside a temporary sandbox, then proves that a sibling path and a compromised provider proposal are denied:

console

cargo run -p tkach-gateway --example golden_case --locked

Expected result:

text

GOLDEN_CASE|safe_output=released|allowed_write=committed|out_of_scope=denied|compromised_action=denied|compromised_executor_calls=0

The positive path uses trusted host configuration for the exact policy, destination, and executor binding; the provider supplies only an untrusted proposal. Read the architecture for the enforcement path and the release notes for the release checks and remaining limitations.

Documentation

Use: integration guide, examples, distribution.
Review: product contract, architecture, security model, threat model.
Follow: changelog, roadmap. Report vulnerabilities through SECURITY.md.

Contributing

Keep changes small and explicit about the security boundary. Core changes need a demonstrated security or product defect; adapters must remain thin and must not duplicate Core logic. See CONTRIBUTING.md for required checks, public-claim rules, and files that must remain local.