ModelFuzz vs SigmaShake

ModelFuzz and SigmaShake are both guardrails & safety tracked by AIDiveForge. Below is a side-by-side comparison of pricing, capabilities, platforms, and ownership — sourced from each tool's live website and verified before publishing.

ModelFuzz

The library ships two halves: a red-team scanner that fires deceptive prompt-injection payloads at any OpenAI-compatible endpoint so you can see which attacks actually trigger a tool call, and a decorator that wraps individual tools and checks every argument against your policies before the function executes. The decorator approach means enforcement lives in your code, not in a separate proxy or prompt. The policy engine works on argument content — keyword matching and pattern rules the docs describe — which catches known-bad patterns well but leaves gaps for novel exfiltration routes that do not match existing rules. A hosted dashboard with centralized policies and audit logs is on a waitlist and not yet available, so teams running multiple agents coordinate policy changes manually across codebases.

SigmaShake

SigmaShake intercepts tool calls from agents running in Claude Code, Cursor, VS Code Copilot, and Gemini CLI, evaluating each action against a rule set before it executes. The vendor states decisions resolve in roughly 85 ms using deterministic native evaluation — no model inference, no GPU, no token spend. Rules follow an Allow/Ask/Deny pattern, where Ask routes the action to a human approval queue rather than blunting everything with a hard block. The desktop app installs in about 30 seconds with no admin rights; the CLI drops into any shell or CI hook chain. Self-hosting is supported, which means the guardrail layer stays offline and never sends your code or commands to a third-party model.

Attribute	ModelFuzz	SigmaShake
Pricing	Free	Paid
Price	—	$5/mo
Free trial	No	No
Open source	Yes	No
Has API	No	No
Self-hosted option	Yes	Yes
Platforms	Python	Windows 10+, macOS 14+, Linux (Ubuntu 22.04+ / Fedora 38+ / Pop!_OS)
Pros	Execution-layer interception via a single decorator, which means a compromised LLM decision gets stopped before the tool function runs — not after secrets are already in transit. Bundled red-team scanner targets any OpenAI-compatible endpoint, so you get a concrete vulnerability report — which payloads triggered a tool call, what percentage landed — before you write a single policy rule. MIT-licensed and self-hostable with no runtime cloud dependency, which means enforcement works in air-gapped or on-premise environments where a SaaS security proxy is not an option. Pure Python decorator integration, so adding shield coverage to an existing agent requires editing one line per tool function rather than restructuring the agent architecture or routing traffic through a sidecar.	Deterministic local evaluation at roughly 85 ms per check, so you avoid the latency and per-token cost of routing every agent action through a model-based policy guard. Ask mode holds a risky action in a human approval queue rather than blocking it outright, which means your agent keeps moving on safe tasks while you review the one call that needs a second look. PreToolUse hook integration for Claude Code and MCP server integration for Cursor, Codex, and VS Code Copilot, so the guardrail wires into agents your team is already running without a custom shim. Self-hosted deployment with no model inference, so your code, file paths, and shell commands never leave the machine — critical for teams with data-handling obligations. Per-user install with no admin or UAC rights required, which means individual developers can adopt it without waiting for IT to sign off on an organization-wide rollout.
Cons	Policy enforcement is rule-based against argument content — keyword and pattern matching as the docs describe. When an attacker uses encoded payloads, splits sensitive data across multiple arguments, or exploits a channel your rules do not cover, the block does not fire. Teams handling adversarially sophisticated injection will need to write, test, and maintain an expanding ruleset rather than rely on the defaults. There is no team-level policy management, centralized audit log, or dashboard available outside a waitlist. A team running four agents with overlapping tool sets coordinates policy changes by editing files in four separate codebases. When that coordination cost exceeds the deployment overhead of a dedicated security proxy or a commercial LLM firewall, teams move to those alternatives. The scanner targets OpenAI-compatible endpoints only. Agents built on frameworks that do not expose a compatible API surface — or that use non-standard tool-calling schemas — cannot be red-teamed with the CLI without custom adaptation, which the docs do not describe.	No API is exposed, so teams building custom agent runtimes or embedding safety checks inside their own orchestration code cannot call SigmaShake programmatically — they wrap the CLI binary, which introduces a process boundary and complicates error handling at scale. The SHAKEDOWN benchmark that positions SigmaShake as the top-ranked guardrail was authored by SigmaShake, and competitor scores were modeled from public docs rather than measured runs; teams doing their own evaluation should run independent tests before treating the benchmark as a neutral comparison. Fleet management and team-level policy enforcement are paid-only features, which means a free-tier team cannot centrally audit what rules individual developers are running — a gap that matters the moment more than one engineer is using an AI coding agent on shared infrastructure. Windows support is the primary release target based on page emphasis and download prominence; macOS and Linux builds are listed but community reports on edge cases outside Windows are sparse, so teams running heterogeneous developer environments should validate on non-Windows machines before committing.

Bottom line

ModelFuzz is free while SigmaShake is paid; ModelFuzz is open source. Choose based on which difference matters most for your workflow.

Frequently asked questions

What is the difference between ModelFuzz and SigmaShake?

ModelFuzz is Free and open source, while SigmaShake is Paid. Compare pricing, free trial, API, platforms, and pros/cons in the table above on AIDiveForge.

Is ModelFuzz better than SigmaShake?

It depends on your workflow. Use the side-by-side attributes (pricing, open source, API, self-hosted, platforms) to decide. AIDiveForge does not rank a universal winner — we publish verified facts so you can choose.