Greywall
Greywall sandboxes any local CLI coding agent with a live activity feed of every file read, write, and outbound connection.
If you run agents with skip-permissions and quietly hope they behave, Greywall is cheap insurance. The live feed plus mid-session deny switching is the part that matters: you see the .env read before the Stripe charge posts. It's kernel-enforced work, not a prompt wrapper, and v0.3.1 tightened command blocking across agents. Skip it if you need VM-grade isolation from hostile code or you're on Windows.
Verified 4d ago · liveness 72/100 · cite: rightaichoice.com/tools/greywall
- Developers running Claude Code, Codex, Cursor, Aider, or similar local CLI agents with skip-permissions flags
- Teams wanting an opt-in enforcement layer plus an activity log before investing in heavier managed governance
- Solo developers who want to see what an agent reads, writes, and calls out to before it hits a production key
- Platform engineers evaluating lightweight kernel-enforced sandboxing without container image rebuilds
- Teams needing VM-grade or container isolation against genuinely hostile code — kernel enforcement is a different bar than a hypervisor
- Windows users — support is Linux and macOS only
- Non-developers who do not run local CLI coding agents
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Skip Greywall if you need VM-grade containment against genuinely hostile code, run Windows, or want enforcement on by default with zero config — Greywall's default is allow, and ask/deny are opt-in.
Kernel layer availability varies by host: on kernels below 5.13 you lose Landlock filesystem control, so the effective protection set is smaller than the feature list suggests.
The Apache-2.0 core costs nothing and covers the full Linux/macOS feature set, which puts Greywall in a different bracket from managed agent-governance platforms that charge per seat or per policy. If you only need single-machine containment and an activity feed, the open-source core is the cheaper path; managed multi-team governance is stated as still being built.
In short
Greywall — Greywall sandboxes any local CLI coding agent with a live activity feed of every file read, write, and outbound connection. Best for Developers running Claude Code, Codex, Cursor, Aider, or similar local CLI agents with skip-permissions flags, Teams wanting an opt-in enforcement layer plus an activity log before investing in heavier managed governance, Solo developers who want to see what an agent reads, writes, and calls out to before it hits a production key. Free to use.
What's new in Greywall
Checked 5 days agoAcross the latest 1 update: 1 changelog entry.
What people actually say about Greywall — is it worth it?
We ran a structured research pass across product reviews, community discussions, and post-purchase forum threads to surface the patterns vendors won't publish themselves. Below: the recurring strengths, the hidden costs people mention most, and the cohort that consistently regrets adopting this tool.
17 mentions across 2 sources (Hacker News, GitHub) · researched Jul 3, 2026.
Average across the 2 sources that answered — each source counts once, not each post.
- +Kernel-level sandboxing provides stronger isolation than container or VM approaches.
- +Deny-by-default policy prevents agents from accessing sensitive files like .env and SSH keys.
- +Live activity feed shows every read, write, and network request in real time.
- +Supports any CLI agent without modifications, including Claude Code, Codex, and Cursor.
- +Zero config for common development directories reduces setup time.
- −Very early-stage with only ~250 GitHub stars and 22 open issues.
- −A user reported it could be forkbombed by a compromised package, raising reliability doubts.
- −Limited community presence outside Hacker News and GitHub makes support uncertain.
- −No official documentation or tutorials beyond the GitHub repo and website.
- −Cross-platform support may have gaps; macOS implementation relies on Endpoint Security.
Viability Score
How well maintained and how widely used is Greywall? Built from what the vendor actually publishes (docs, changelog, tutorials, integrations, pricing), whether the site is live, and how much real users discuss it. How we calculate this
Last calculated: October 2026
How we score →Key Features
- Live activity feed logs every file read, write, and outbound connection in real time
- Kernel-enforced filesystem sandboxing with per-path read/write/deny rules
- Network isolation via TUN + SOCKS5 proxy captures TCP/UDP traffic including binaries that ignore proxy env vars
- Seccomp BPF syscall filtering blocks dangerous system calls like ptrace, mount, kexec, and module loading
- eBPF monitoring traces syscall exits with process, path, and reason context
- Landlock filesystem control enforces read/write permissions below userspace on Linux 5.13+
- Bubblewrap namespaces isolate process, network, and mount environments on Linux 3.8+
- Switch between allow, ask, and deny mode mid-session without restarting the agent
- Deny rules for filesystem paths, network hosts, and commands
- Command blocking applies inside pipes, chains, and nested shells
- Learning mode auto-generates least-privilege templates via strace
- Safe defaults deny .env, SSH keys, git hooks, and shell configs
- One-line install via Homebrew, curl, Go install, or build from source
- Works with any local CLI agent with no agent-specific configuration
- Linux and macOS support with graceful degradation on older kernels
About Greywall
Greywall is a sandbox and observability layer for local CLI coding agents on Linux and macOS. It sits under the agent process, so you install it once and then prefix any command: `greywall -- claude --dangerously-skip-permissions`. The agent keeps its same flags and never needs agent-specific setup, because Greywall wraps the process rather than integrating with each tool. It supports Claude Code, Codex, Cursor, Aider, Goose, Amp, Gemini CLI, Cline, OpenCode, and Copilot. The install is one line via Homebrew, curl, or Go install. It is Apache-2.0 licensed and currently at v0.3.1. The core pitch is observability first. GreyProxy records every read, write, and outbound request as it happens, and the default allow mode keeps the agent moving. From the dashboard you can switch into ask or deny mode mid-session without restarting the agent, or set explicit deny rules for filesystem paths, network destinations, and commands. Sensible defaults already deny .env files, SSH keys, git hooks, and shell configs while leaving everything else open. A learning mode uses strace to observe filesystem access and turn it into an initial least-privilege template, and command blocking still applies inside pipes, chains, and nested shells. The enforcement is stacked: Bubblewrap namespaces for process, network, and mount isolation on Linux 3.8+, Landlock for kernel-level filesystem permissions on Linux 5.13+, Seccomp BPF blocking syscalls like ptrace, mount, kexec, module loading, and BPF manipulation, eBPF monitoring for syscall-exit visibility, and a TUN + SOCKS5 proxy that captures TCP/UDP traffic even from binaries that ignore proxy environment variables. Layers degrade gracefully on older kernels. The comparison target is container-based isolation. Greywall is meant to be lighter, with no image rebuilds and native tool access, and it installs in one line without config. Containers and bespoke sandboxes are heavier and interrupt how developers actually work, while Greywall's
Behind the Verdict
The scenario Greywall is built around is embarrassingly common: you tell an agent to add rate limiting, it reads .env to grab the key, calls the live Stripe endpoint to test, and the only signal you get is your bank alert. The fix here isn't a stronger system prompt. It's a boundary under the process plus a feed that shows the attempt before the consequence. That's the honest selling point. Watch mode is default and quiet, deny mode is one switch away without restarting the agent, and the learning mode bootstraps a least-privilege template from strace output so you're not hand-writing rules on day one. In practice, developers reach for this when they want to catch an agent reading .env or hitting a live endpoint, and they don't want to rebuild a container image every time they change a line of code. Where it bites: enforcement is kernel-enforced on Linux and macOS, but it is not a VM. If your threat model is genuinely hostile code, the five-layer stack (Bubblewrap, Landlock, Seccomp BPF, eBPF, TUN + SOCKS5) raises the bar without becoming a boundary a determined adversary cannot cross. Windows isn't supported at all. And the default is allow: if you expect enforcement on by default with zero config, you'll be surprised, because ask and deny are opt-in. Compared to containers, the tradeoff is intent. Containers give you stronger isolation but cost you image rebuilds and native tool access. Safehouse and hand-rolled sandboxes sit somewhere in between, with more setup for less live visibility. Greywall's angle is fast install, no config required, and a dashboard that shows what the agent actually touched. Pick it when you run Claude Code, Codex, Cursor, Aider, Goose, Amp, Gemini CLI, Cline, OpenCode, or Copilot locally and want an opt-in enforcement layer plus an
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Real-world workflow fit
Concrete scenarios for the personas Greywall actually fits — and what changes day-one when you adopt it.
Installs via `brew tap greyhavenhq/tap && brew install greywall`, then runs `greywall -- claude --dangerously-skip-permissions`. Mid-session the activity feed shows `read .env` and an outbound call to api.stripe.com; the developer switches to deny mode and denies both.
Outcome: The agent continues with placeholder values in tests, no production API key is exposed, and no live Stripe charges are posted.
Runs `greywall --learning -- claude` to let strace observe filesystem access, collapsing 47 discovered paths into 12 rules and saving them as a template named `claude`, then re-runs `greywall -- claude` to auto-load that template.
Outcome: A least-privilege starting policy exists without hand-writing rules, and the template can be reviewed and tightened before sharing with the team.
Drops ~/my-project/src/, package.json, and node_modules/ (read-only) into the allow list, and adds ~/.ssh/, ~/.env, ~/other-repos/, and ~/Documents/ to the deny list, then runs any agent under `greywall --`.
Outcome: Writes are confined to the project tree, while SSH keys, env files, and unrelated repos stay protected even though the agent keeps running normally.
Use Cases
- Sandbox Claude Code to prevent it from reading ~/.ssh/ or .env files in production projects.
- Watch every file read/write and network call made by Codex while building a web app, then switch to deny mode for sensitive paths.
- Enforce that your AI agent can only write to src/ and package.json, but never to /etc/ or ~/Documents/.
- Block all outbound connections except to your own staging API, ensuring no data leaks to external services.
- Run Cursor with deny rules for .env and API key files while allowing full access to project source code.
- Generate a least-privilege rule template for a new project with `greywall --learning -- claude` instead of hand-writing the policy.
Limitations
- Greywall is a kernel-enforced sandbox for AI coding agents running on Linux and macOS, observing every read, write, and outbound connection and letting you deny specific filesystem paths, network hosts, and commands in config.
- Defaults let the agent run while logging activity; ask or deny mode can be toggled mid-session without restarting.
- On older Linux kernels protections degrade gracefully (Bubblewrap needs Linux 3.8+, Landlock needs Linux 5.13+), so the number of active layers depends on your host.
- A managed governance layer for running it across multiple teams is stated as being built, not yet available.
as of 2026-10-04
Verification history
We have re-verified Greywall 9 times since . Each pass re-reads the vendor's own pages and re-checks every listed field against that evidence; passes where nothing had changed are marked as such.
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
Showing the 6 most recent of 9 verification passes.
Free to cite with attribution — this page re-verifies continuously.
12-month cost
Project the real annual outlay, including the implied monthly cost when only an annual tier is published.
Vendor list price only. Add-on usage, seat overages, and contract minimums are surfaced under Hidden costs & gotchas.
Plans compared
For each published Greywall tier: who it actually fits, and what it adds vs. the previous tier. Cross-reference the cost calculator above for projected annual outlay.
Open Source Core
$0
Ideal for
Solo developers and small teams running local CLI coding agents who want an activity feed and kernel-enforced allow/deny control without a per-seat contract.
What this tier adds
Starting tier: Apache-2.0 core (v0.3.1) with the live activity feed, allow/ask/deny modes, path/network/command deny rules, and all five Linux enforcement layers.
Enterprise / Managed Governance (building)
Talk to us
Where the pricing makes sense
The company stage and team size where Greywall's pricing actually pencils out — and where peers do it cheaper.
The Apache-2.0 core costs nothing and covers the full Linux/macOS feature set, which puts Greywall in a different bracket from managed agent-governance platforms that charge per seat or per policy. If you only need single-machine containment and an activity feed, the open-source core is the cheaper path; managed multi-team governance is stated as still being built.
Setup time & first value
How long it actually takes to get something useful out of Greywall — broken out by persona, not the marketing-page minute.
Install is one line — `curl -fsSL https://raw.githubusercontent.com/GreyhavenHQ/greywall/main/install.sh | sh`, `brew install greywall`, `go install`, or build from source — so most developers are running an agent under it in a few minutes. First real policy work is the longer step: either accept the sensible defaults, or run one `--learning` pass and review the generated template, which
Switching to or from Greywall
How to bring data in from common predecessors and how to get it back out — written for the switcher, not the buyer.
- →From running agents with no sandbox: prefix the exact same command with `greywall --`, e.g. `greywall -- codex --yolo`; no agent-specific configuration is needed.
- →From Docker-based agent isolation: keep the same locally installed agent and drop the image rebuild loop; use the TUN + SOCKS5 proxy and deny lists in place of container network rules.
- →From hand-written proxy env vars: Greywall's TUN capture covers binaries that ignore HTTP_PROXY/HTTPS_PROXY, so those workarounds can be retired.
- →From writing allow/deny rules by hand: run `greywall --learning -- <agent>` once to generate a least-privilege template from observed access.
- ↗To VM-grade or container isolation: required if your threat model includes genuinely hostile code, since Greywall is kernel-enforced rather than a full containment boundary.
- ↗To Windows-hosted agent tooling: Greywall does not run on Windows, so Windows developers need a different approach.
Resources & Guides
Tutorials & Learning
YouTube returned 6 videos for “Greywall”, and we withheld 6: 6 could not be judged, because “Greywall” is a single word that other videos use for other things. We are showing none, because we could not prove any of them are about Greywall.
Official links
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