Open-source deterministic hypervisor platform for automated software testing, inspired by Antithesis.

Status: under active development. Certain execution paths may not work as intended. The TCG backend is fully deterministic but slow (~100 states/min). The Firecracker backend is fast (~1200 states/min) and fully deterministic when host KVM patches are applied (make install-host-kernel); without them (no_host_patches: true, the default for examples), it reaches approximately 99% KCOV edge determinism.

OpenThesis runs your system inside a deterministic virtual machine where time, randomness, and network events are fully controlled. At each burst boundary, the orchestrator snapshots the VM state and forks execution with a different fault schedule - building a tree of explored states across thousands of distinct scenarios per minute. Coverage is tracked with kernel KCOV¹; new edges drive the search forward via an MCTS-based snapshot selector² using AFL-style edge bucketing³, while a UCB1 bandit inspired by MOPT⁴ selects which fault kinds to apply. Test drivers can steer the search using IJON-style maximize and explore hints⁵. Subtrees with plateaued coverage discovery are detected using the Chao1 species-richness estimator⁶ and deprioritized. When a property violation is found, the exact seed and fault schedule are saved so the bug can be replayed, shrunk to a minimal reproducer, and causally attributed to the specific fault that triggered it.

# Requires Go 1.25+, Linux, KVM (/dev/kvm)
make install   # download guest kernel, rootfs, and patched Firecracker

# Run a campaign
openthesis campaign --config examples/etcd/openthesis.json --duration 10m --parallel 8

# Browse violations
openthesis find

# Replay a specific violation
openthesis replay --artifact ~/.openthesis/etcd/violations/violation-000-*/

# Shrink to a minimal fault schedule
openthesis shrink --artifact ~/.openthesis/etcd/violations/violation-000-*/ --config examples/etcd/openthesis.json

• Linux with KVM (/dev/kvm)
• Go 1.25+

make install                        # download guest kernel, rootfs, patched Firecracker
make install BACKEND=firecracker    # same, prefer Firecracker explicitly
make install BUILD_KERNEL=1         # build guest kernel from source instead of downloading
make install-check                  # verify prerequisites (Docker, QEMU, /dev/kvm)
make install-host-kernel            # patch host KVM modules for full determinism (sudo, ~10 min)

First-time provisioning and full build on a bare-metal server:

make setup HOST=ubuntu@YOUR_SERVER          # provision + build all + deploy (~60 min)
make status HOST=ubuntu@YOUR_SERVER         # show which steps are complete

Individual steps:

make provision          HOST=ubuntu@YOUR_SERVER   # base packages, firewall
make build-firecracker  HOST=ubuntu@YOUR_SERVER   # patched Firecracker (~30-60 min)
make build-kernel       HOST=ubuntu@YOUR_SERVER   # deterministic guest kernel (~20 min)
make build-rootfs       HOST=ubuntu@YOUR_SERVER   # Debian bookworm rootfs (~10 min)
make build-host-kernel  HOST=ubuntu@YOUR_SERVER   # patched KVM modules for full determinism (~10 min)
make deploy             HOST=ubuntu@YOUR_SERVER   # deploy openthesis binaries
make deploy-example     HOST=ubuntu@YOUR_SERVER EXAMPLE=etcd

Tests use the OpenThesis SDK to declare properties about your system:

import ot "github.com/openthesis/openthesis/sdk/go/assert"

// Must be true on every execution
ot.Always(balance >= 0, "balance is never negative", map[string]any{"balance": balance})

// Must be true at least once during exploration
ot.Sometimes(isLeader, "a leader is eventually elected", nil)

// Must be reachable
ot.Reachable("failover path exercised", nil)

Guidance signals steer the exploration engine toward interesting states:

import "github.com/openthesis/openthesis/sdk/go/guidance"

guidance.Maximize("writes_committed", int64(commitCount))
guidance.Explore("raft_term", int64(term))

Available SDKs: Go, Python, Java, C, Rust.

Scripts in the test bundle are dispatched by the guest agent based on filename prefix:

Openthesis is distributed under AGPL-3.0-only.