Tacy

Tacy runs AI agents in confidential VMs. Your requests are encrypted to a key that exists only inside a VM whose code you can check, so nobody else can read them, us included.

What this is

The code inside Tacy's trust boundary: everything the agent VM runs, how its definition is built reproducibly, and the verifier that checks a running VM before anything is sent to it. Everything outside the boundary (the web app, the relay, the control plane) only sees ciphertext and metadata, and isn't here (What's not here).

What it proves

Attestation proves which code a VM runs. It proves nothing about what that code does. So the code has to be public, rebuildable, and every release signed in a public log. Together:

• The key is the VM's. An Intel TDX quote binds the VM's per-boot encryption key to its measured boot chain and to the hash of its compose.yaml (How it works).
• The VM runs a release from this repository. That compose hash must be signed by this repository's release workflow on a version tag, logged in Sigstore's public Rekor log (Releases and signing).
• The release is this source. Anyone can rebuild a release and get the same compose, binary hashes and image digests (Reproduce).
• Underneath is a known OS on a known VM shape. The firmware, kernel, initramfs and root filesystem are pinned measurements (Boot measurements).

What it doesn't prove, and what you still have to trust, is listed under What's not here.

How to verify a release

1. The signature. Check that a release's compose.yaml was signed by this repository's release workflow on its tag (needs the GitHub CLI):

   gh release download v0.19.1 --repo tacyhq/tacy --pattern compose.yaml
   gh attestation verify compose.yaml --repo tacyhq/tacy \
     --signer-workflow tacyhq/tacy/.github/workflows/release.yml --source-ref refs/tags/v0.19.1
   

2. The build. Rebuild the tag and compare it with its release.json and with the images ghcr.io serves (needs docker, git, curl and jq):

   scripts/reproduce.sh v0.19.1
   

3. A running VM. The browser checks the VM's attestation before every request: 16 checks, in the same Go code as verifier/ and release/ (How the browser verifies a VM).

Release history is in CHANGELOG.md. To report a vulnerability, see SECURITY.md.

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