Harden Review (2026): Pricing, Features & Honest Verdict

TLDR

Harden is a free local firewall that checks what coding agents try to run before the command executes. It is careful, unusually transparent software held back by a closed beta licence and a model that only advises. Best for: solo developers on Macs. Price: from $0/mo, free plan yes. Rating: 7.0/10.

What is Harden?

We came across Harden on Product Hunt, where it launched on 9 September 2026 as a security tool for agents that write and run code. The product the marketing site sells is called AIF, short for a longer brand name that ends in the word Foundation. That word is branding. The terms and the beta licence both name VizopsAI, Inc., a Delaware corporation, as the operator, and nothing on the site describes a non-profit.

AIF sits between an agent such as Claude Code or Codex and your shell. Every covered tool call goes to a daemon on your own machine, which decides to allow it, block it, pause it for approval, redact a secret out of it, or log it. The promise is that you can let agents work unattended without one of them piping your .env file to a stranger or deleting a production namespace.

What Are Harden’s Key Features?

Hooks into seven agents, with a proxy for the rest

AIF works through each agent’s own hook system rather than a network proxy. Claude Code and Codex get native hooks that fire before execution, Google’s Antigravity CLI and the Anysphere editor get hook wiring, Kiro gets hooks for its main agent, and OpenClaw plus one other agent go through a bridge process. Anything else that speaks MCP over stdio can be routed through an aif mcp-proxy wrapper. Every hook is set to fail closed, so if the daemon dies, tool calls are blocked rather than waved through.

Secret-flow rules that come with a guarantee

The core is deterministic. The rules reference lists about 46 credential detectors (AWS, OpenAI and Anthropic provider keys, payment and code-host tokens, PEM files, JWTs) plus rules for data flowing from a source to a sink. The trust page publishes a short table of cases it guarantees to block, such as cat .env piped to curl, or an environment variable posted from inline Python. It also blocks rm -rf outside the repo and force pushes to main, labelled as a preview feature.

Block-and-steer instead of a bare refusal

When AIF stops a call it hands the agent a safer alternative, so the run carries on. The demo on the site shows an attempt to delete a production Kubernetes namespace being refused and replaced with a restart of the staging deployment. Secrets you enrol with aif enroll can be swapped for placeholder handles in shell output, which keeps the real value out of the model’s context.

A local dashboard and decision log

Every decision lands in a SQLite file at ~/.aif/aif.db with no retention limit. The aif show command opens a viewer on 127.0.0.1:47391, and there is a terminal view too. You can replay old blocks against a newer release, review paused calls, and export a redacted bundle.

What Is It Like to Use Harden?

We did not install AIF, so this describes the workflow from the docs, the install script and the release package we downloaded. Setup is one shell line that fetches install.sh from aif.harden.run. The 1,007-line script pulls a signed release (version 0.7.5 when we checked), verifies its sha256 checksum, checks a minisign signature only if minisign is present, places the build under ~/.aif and adds one line to your shell profile. It does not touch agent configs until you run aif configure, which offers a dry run first.

There is an irony here. One of AIF’s own built-in rules blocks downloaded code that would run immediately, which is exactly what the documented install command does. It is a common pattern, but a security product could also offer a package manager route.

The local AI part is heavier. The full model needs an Apple Silicon Mac with 16 GB of unified memory (24 GB recommended) and a 5.17 GiB download, and the docs measured a 2.33-second warm median decision on an M5. The rule engine is much quicker: Harden reports a 70.2 ms P99 from one week of internal use.

Where Does Harden Fall Short?

It is not open source. The site’s own metadata still describes an open-source CLI that is free forever, but the GitHub repository holds only an introduction page, a licence and a notice file, and the trust page states outright that AIF is closed source. The build ships under a proprietary beta licence that bans reverse engineering, may be withdrawn at any time, and limits liability to $100. The Node and Python SDK packages it mentions are 0.0.1 placeholders.

The marketing and the trust page disagree about the model. The site says Harden’s custom models judge every action and stop the dangerous ones. The trust page says the AI tier is advisory at launch, runs after the rule-based verdict and never changes it. The research write-up adds that the model is near-blind to deliberate sabotage, and the claims cover careless agents only, not a prompt-injected one hiding its tracks.

The numbers come from the vendor. Its benchmark wins over GPT-5.5 are narrow (83.7% against 81.4% on AgentHazard, 15.8% against 14.3% on a reworked SLEIGHT setup) and were run by Harden, not a third party. The dogfood figure of 0.25% wrong blocks sounds tiny, yet it means 62 of the 167 blocks in that week were wrong, measured on the team’s own machine.

Coverage has holes the docs admit. Kiro subagents’ shell commands and file edits are not seen at all, HTTP-based MCP servers are not proxied, and Windows is unsupported. The supported-agent list also varies: seven agents on the marketing site, five on the pricing card, and the repository introduction that lists Gemini CLI instead of Antigravity CLI.

The legal pages lag the product. The terms, dated 5 April 2026, describe identity management, observability and cost analytics, not an agent firewall. The privacy policy, dated 13 April 2026, covers only the website and one advertising tag, while the trust page is where telemetry is described.

How Much Does Harden Cost?

Harden starts at $0. The free plan is for individual developers, needs no account or card, and covers the core secret-flow blocking, block-and-steer, the local history and telemetry opt-out. The trust page commits to never charging individuals for local protection, and says features labelled preview can stay free, move to a paid plan, or be cut.

The only paid option is Enterprise at a custom price, adding compliance reporting, an air-gapped mode with no telemetry, MDM-managed installation, support SLAs and custom terms. No figure is published. The site’s /pricing URL returns a 404 page; plans sit in a section of the main page.

On data, the free build sends an anonymous payload of counts (version, OS, agents in use, decision counts, a random install ID) once every 24 hours and checks for updates every 4 hours. Both stop with an environment variable, and aif telemetry show prints the payload first. The release build we inspected contains only the disclosed Harden and GitHub endpoints and no third-party analytics library.

Two paths do carry more: filing an appeal uploads the call’s commands, prompts and paths with credentials tokenized, and enterprise devices sync activity including prompts. Locally, AIF stores your prompt text by default unless you switch that off.

Compared with paid rivals, free is hard to beat. E2B’s Pro sandbox plan is $150 a month plus usage, and Daytona charges by the second for compute.

Who is Harden Best For?

Use Harden if you run Claude Code or Codex with broad permissions on a Mac or Linux machine and your worry is a careless agent leaking credentials or deleting the wrong directory. It costs nothing, keeps decisions on your machine, and its trust page is more candid about gaps than most security vendors manage.

Skip Harden if you need an open-source tool you can audit, protection against a deliberately hostile agent, Windows support, or a published team price. Skip it too if your workflow leans on Kiro subagents, which it cannot see.

Best Harden Alternatives

GitGuardian

GitGuardian’s ggshield scans .env files, shell history and agent transcripts for leaked credentials, and its agent hooks aim to stop new ones. The Starter plan is $0 for up to 25 developers. Developer endpoint protection is a paid add-on on the Business and Enterprise plans, which are quote only.

E2B

E2B takes the opposite route: run agent code in disposable cloud sandboxes so mistakes stay contained. Hobby is free with a one-time $100 usage credit, Pro is $150 a month plus per-second usage, and Enterprise is custom. A sandbox will not stop an agent from dropping a cloud database it has credentials for, which is the gap Harden targets.

Daytona

Daytona also sells isolated sandboxes for AI-generated code, priced pay-as-you-go at $0.0504 per vCPU hour and $0.0162 per GiB of memory per hour, with $200 of free compute included. It suits teams moving agents off developer laptops entirely.

Final Verdict: Is Harden Worth It?

For a solo developer, yes. AIF is free, fails closed, keeps decisions local, and its trust page documents every network call, every known gap and the exact telemetry payload. Few security products publish that much, and the rule engine targets the most common agent accident: a credential sent somewhere it should not go.

Go in with clear eyes. This is version 0.x proprietary beta software from a company whose own site still calls it open source, whose headline model only advises, and whose accuracy figures are self-reported. Install it as an extra guard on a trusted machine, not as your only defence, and wait for independent testing and a published team price before deploying it across a company.