Tag
Runtime tools
7 reviewed tools: 7 free or open source.
Order: free and open source first, then hosted products with a real free tier, then paid-led; catalog order inside each group, with quiet or archived repos last. Not a score, and no tool pays for its place.
7 tools
- MiseMIT polyglot runtime manager, the asdf successor that is fast
Free / OSS · OSS/MIT · 35.2k GitHub stars
VerdictThe version manager to install in 2026. MIT, fast, one toml.
CatchNot a container runtime and not direnv-only. Some asdf plugins still assume bash. Team-wide adoption means every laptop runs mise, or CI drifts.
- DenoMIT TypeScript runtime forever; Deploy free tier is real but separate
Free / OSS · Freemium · 109k GitHub stars
VerdictMIT runtime forever. Deploy free tier is real; do not merge the two.
CatchDeploy is not the runtime. The MIT runtime is free forever; Deno Deploy is a separate hosted product with a free tier — do not conflate them. Distinct from Node and Bun as runtimes.
- AgnoApache-2.0 Python agent framework + AgentOS runtime (ex-Phidata)
Free / OSS · Apache-2.0 · 42.8k GitHub stars
VerdictApache-2.0 Python agents + AgentOS. Ship on Agno, not Phidata nostalgia.
CatchVs LangGraph (graphs), CrewAI (roles), Mastra (TypeScript): Agno is Python performance + AgentOS productization, not a coding CLI like Claude Code/OpenCode. Phidata docs/imports are dead—use Agno. Control Plane and hosted conveniences are optional; day-one is OSS SDK+runtime you operate.
- Agent SubstrateHigh-density secure sandbox runtime for idle-heavy agent workloads
Free / OSS · Apache-2.0 · 5.7k GitHub stars
VerdictApache-2.0 agent sandbox runtime. Reach for dense suspend/resume isolation on K8s; bring cluster ops.
CatchVs AgentBox and Flue: Substrate is the dense sandbox/runtime control plane on Kubernetes, not a developer ADE and not a TypeScript harness framework. Ops cost is real — you need cluster competence. README notes it is not an officially supported Google product.
- AX (Agent Executor)Apache-2.0 Go CLI and Kubernetes CRDs for running agent tasks
Free / OSS · Apache-2.0 · 14k GitHub stars
VerdictApache-2.0 agent executor for Kubernetes. Use the ax-agent-executor CLI and CRDs when durable Task/Workspace/Gateway primitives matter; do not confuse it with AX Check.
CatchThis is AX Agent Executor, not the live AX Check (Gauge) evaluation product — the names collide, so use the ax-agent-executor slug. Vs Agent Substrate: AX is the task/CLI/CRD experience on top of an agent runtime; vs OneCLI and Dexto: it is Kubernetes execution infrastructure, not a general desktop agent; vs Cua: it is not a browser/computer-use surface. Kubernetes and Agent Substrate operations are still your problem.
- gVisorApache-2.0 userspace container sandbox — OCI runtime runsc for agent isolation
Free / OSS · Apache-2.0 · 19.7k GitHub stars
VerdictApache-2.0 OCI sandbox runtime when agent or untrusted containers need more than runc — Linux-only, syscall gaps, and you bring the orchestrator.
CatchLinux only (kernel 5.6+ recommended). Not every syscall is implemented — exotic workloads fail or fall back. Heavy file and network I/O pay a measurable overhead versus runc. This is a runtime, not an SDK or an orchestration product: you still wire Docker/K8s/agent harnesses yourself. Vs Firecracker/Cloud Hypervisor (microVMs) and plain seccomp: gVisor is the userspace kernel middle path.
- containerdApache-2.0 CNCF container runtime under Kubernetes
Free / OSS · Apache-2.0 · 21.4k GitHub stars
VerdictThe runtime you are probably already using — interact with it through Kubernetes, nerdctl or Docker.
CatchIt is a low-level daemon, not a developer tool: you drive it through Kubernetes, nerdctl or Docker rather than directly, and its own ctr CLI is meant for debugging. Vs docker (the full developer experience on top): reach for containerd directly only when building platforms or nodes.
FAQ
- What is the top free pick among Runtime tools?
- Mise leads the Stack Gems list for Runtime tools. Verdict: The version manager to install in 2026. MIT, fast, one toml.
- How many Runtime tools does Stack Gems review?
- 7: 7 free or open source. Each review has a verdict and an honest Catch; no tool pays for its spot.
- Which Runtime tools can I self-host for free?
- Mise, Agno, Agent Substrate, AX (Agent Executor), gVisor and containerd.
- Which Runtime tools have the most GitHub stars?
- Deno (109k), Agno (42.8k), Mise (35.2k), per GitHub on 2026-10-21. Stars measure attention, not fit; read the Catch.
- What is the catch with Mise?
- Not a container runtime and not direnv-only.