Claude Code mods are privileged code, not harmless add-ons. Anthropic says mods run with the same access as Claude Code, are not sandboxed, and can read user-accessible files and environment variables, inspect session context, rewrite prompts or tool calls, approve actions before the usual permission prompt, and make network requests.
Install a mod only when you trust its publisher and can inspect its manifest, scripts, hooks, bundled binaries, and external connections. Catalog checks are limited source and structure checks, not a security review. Sandboxing Claude’s own filesystem and network activity can reduce exposure, but it does not turn the mod itself into sandboxed code.
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What “safe” means for a Claude Code mod
A mod is code that runs inside Claude Code with your permissions. Anthropic’s security guidance describes the risk plainly: a mod inherits the authority available to the Claude Code process, rather than running in a separate, restricted container. The practical question is therefore not whether a mod has a “safe” label, but what the code can reach, what events it intercepts, where it sends data, and how quickly you can disable it.
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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesFor a personal installation, assume a mod can act on anything your Claude Code session can act on unless you have deliberately limited that access. For a managed team installation, the relevant question is whether organizational settings prevent unapproved code and preserve centrally enforced policy.
#1 Best Overall
What a mod can access
Files and project data
Because mods run with Claude Code’s access, they can read or write files that the process can reach. That includes the current repository, files in other user-readable directories, configuration files, logs, and generated artifacts. A mod does not need to wait for you to ask Claude to open a file; its own code can inspect files when its event handlers run.
Write access is equally important. A malicious or defective mod could alter source files, configuration, shell scripts, deployment manifests, or generated output. A change may be difficult to notice if it is made during an otherwise normal tool call.
Environment variables and credentials
Environment variables are part of the process environment. If an API key, cloud credential, token, or connection string is present there, a mod may be able to read it. The same applies to secrets stored in files that your account can read, such as local configuration or credential files. “The key was never pasted into a prompt” is not a sufficient protection if the key is available to the Claude Code process.
Use a throwaway project and non-sensitive credentials for first-run testing. Before installing, identify which variables and credential files are present, remove anything unnecessary, and rotate a credential immediately if you suspect it was exposed.
Rank #2
Prompts, tool calls, and session context
Mods can observe session context, including prompts and tool-call information. That can reveal proprietary source code, internal ticket text, customer data, file contents included in a prompt, and secrets accidentally pasted into a conversation. Treat the complete session transcript and tool history as data a mod may process.
Processes and networks
A mod can make network requests and may start subprocesses when its code or an associated hook does so. Network access creates a path for telemetry, data exfiltration, remote commands, or downloads. A trustworthy publisher should explain every external destination and why the connection is needed; unexplained calls are a stop signal.
Can a mod bypass Claude Code’s permission prompt?
It can change the control flow around permissions. Anthropic documents that a mod can rewrite prompts and tool calls and approve a call before the normal permission prompt appears. That means the familiar approval dialog is not an independent security boundary when the code making or intercepting the request is itself untrusted.
Review a mod’s event handlers for anything that transforms user input, edits a proposed command, changes an approval result, or automatically retries a denied action. A mod that promises “fewer interruptions” may be doing useful automation, but the same mechanism can suppress a warning you expected to see.
Are Claude Code mods sandboxed?
No. Anthropic’s 2026 Claude Code mods announcement says, “They aren’t sandboxed, and you should only install mods from sources you trust, the same way you’d install any code on your computer.” The mod executes with the user’s available permissions.
Claude Code can provide sandboxing for Claude’s filesystem and network activity. Anthropic’s 2025 engineering article reports an 84% reduction in permission prompts in its internal usage when sandboxing was enabled. That figure describes Anthropic’s internal experience, not a guaranteed reduction for every project, operating system, or configuration.
Most importantly, sandboxing Claude’s activity does not automatically sandbox a mod. Keep the two controls separate in your threat model:
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| Component | What it controls | Security implication |
|---|---|---|
| Mod | Code running inside Claude Code with the process’s permissions | Can inspect context, alter control flow, access reachable files and environment variables, and make network requests |
| Claude Code sandbox | Filesystem and network isolation for Claude’s activity | Can reduce the actions Claude may perform; does not make an untrusted mod trustworthy |
| Hook | Event-triggered commands, potentially including shell commands | May execute arbitrary shell commands with full user permissions |
| MCP server | External tool or service connected to the session | Adds another code and data-handling boundary that must be reviewed |
Are hooks and MCP servers scanned?
Hooks
Anthropic warns that hooks execute arbitrary shell commands with full user permissions and can cause irreversible damage. A hook can run automatically on an event, so its behavior may occur before you recognize that a command is being launched. Read every hook command, script, interpreter invocation, redirection, deletion operation, and downloaded executable. Treat a hook that uses a shell, evaluates constructed strings, or contacts an unfamiliar host as high risk.
Rank #4
MCP servers
Anthropic’s scanning page says MCP servers and hooks are not scanned at this time. Their presence in a catalog or configuration therefore does not establish that the code is safe, reviewed, or free of data-collection behavior.
Catalog and manifest checks
Catalog checks for a mod’s URL and manifest structure do not inspect or execute the code. They can catch a malformed listing or an invalid source reference, but they are not a security review and cannot prove that a repository, release archive, hook, or MCP server is benign.
How to install a mod more safely
Use this sequence before enabling a mod in a real repository or account:
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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →- Open the source repository. Read the manifest, installation instructions, commands, scripts, hooks, configuration files, and any bundled binaries. Do not rely on a catalog description alone.
- Verify the publisher. Confirm the organization’s identity and inspect its repository history. Watch for look-alike names, copied descriptions, abandoned projects, and forks that change the source.
- Map the privilege surface. List every file path, subprocess, network destination, environment variable, prompt or tool event, permission check, and UI event the mod can access or intercept.
- Check data handling. Determine whether prompts, tool calls, telemetry, diagnostics, or file contents leave the machine. Require a clear explanation of each external request and a way to disable optional telemetry.
- Pin the version. Use a release tag or commit hash rather than a moving branch or a generic “latest” tag. Record the exact version so a later update cannot silently change the code you reviewed.
- Test in isolation. Use a throwaway project, a separate user account when practical, and non-sensitive credentials. Watch filesystem changes, child processes, network connections, and generated output during the test.
- Enable available containment. Use Claude Code’s filesystem and network sandboxing where it fits your workflow. Remember that this limits Claude’s activity; it does not certify the mod.
- Define a rollback. Know how to disable or remove the mod, restore the project from version control, revoke test credentials, and review logs before allowing it into a production workspace.
How organizations can reduce mod risk
Individual inspection does not scale well across a team. Anthropic describes managed settings and a built-in sec-default mod that can restrict user-installed mods and preserve managed policy. Administrators should use those controls to define which sources are approved, whether users may add their own mods, and which security settings cannot be overridden locally.
Document an allowlist with the publisher, repository, pinned release, permitted network destinations, and review owner. Re-review a mod when its commit, hooks, MCP configuration, or requested permissions change. Keep production credentials out of development sessions whenever possible, and separate repositories or accounts when a mod requires broader access.
How to evaluate two mods
When two mods appear to offer the same feature, compare the boundaries below rather than the marketing description:
| Comparison axis | Questions to answer |
|---|---|
| Privilege surface | Can it read or write files, start processes, access environment variables, use the network, or view session context? |
| Event coverage | Which prompts, tool calls, permission checks, lifecycle events, and UI actions does it intercept? |
| Supply-chain trust | Who publishes it, how old is the repository history, are releases signed or pinned, and can the source be reviewed? |
| Containment | Does it work with sandboxing, respect managed policy, and provide a clear disable or uninstall path? |
| Data handling | What telemetry or external calls occur, what data is transmitted, and are destinations disclosed and limited? |
A mod with fewer features but a narrow, auditable event scope is generally easier to trust than one that intercepts every prompt and tool call. “Open source” helps only when the source is complete, the published artifact matches it, and someone has actually reviewed the relevant code.
What to do if a mod behaves unexpectedly
- Stop the session. Do not approve additional commands or continue entering sensitive prompts.
- Disable the mod. Remove or deactivate it using the supported configuration path. If you need a clean diagnostic session, use Claude Code’s
--safe-modeoption. - Turn off hooks when appropriate. In managed settings, administrators can use
disableAllHooksto prevent hook execution while investigating. - Preserve evidence. Save the pinned version, manifest, logs, changed files, process list, and relevant network records before cleanup.
- Contain the account. Revoke or rotate API keys, cloud tokens, SSH keys, and other credentials that were present in the environment or readable files.
- Review changes. Compare the repository with a known-good commit, inspect shell history and scheduled tasks, and check for newly created binaries, scripts, or configuration entries.
- Escalate internally. For a team installation, notify the security owner and block the source until the code and any data exposure are understood.
Bottom line
Claude Code mods are safe only to the extent that their code, publisher, permissions, and data flows are trustworthy. They are not sandboxed, catalog checks are not a code audit, and hooks and MCP servers currently are not scanned according to Anthropic’s scanning guidance. Review and pin the source, test without sensitive data, use available sandboxing and managed settings, and keep a rapid disable-and-rotate plan for every mod you install.
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