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ShellPermit Shell Command Policy Guard
x402
ShellPermit Shell Command Policy Guard is a paid API for AI agents from shellpermit.schemasure.com, paid per call via x402, $0.03/call, status unknown (last checked 2026-10-11).
Validates a bash command against a configurable execution policy using a real shell tokenizer, returning compliance decisions with reason codes and optional short-lived execution permits — without ever executing the command.
Price / call$0.03
Success—
StatusUnknown
How this service works
Decide whether an agent-authored bash command complies with an execution policy, using a real shell tokenizer rather than pattern matching. Catches recursive deletes, force pushes, cluster and infrastructure teardown, raw device writes, path escapes, privilege escalation, and curl-piped-to-shell through pipelines, substitutions, quoting games and base64. Returns reason codes with spans and an optional short-lived permit bound to the exact canonical command. Never executes anything.
Output
Returns a compliance decision (permit or deny), one or more structured reason codes identifying the violation category (e.g. recursive-delete, force-push, privilege-escalation, path-escape, curl-pipe-shell), span offsets into the original command string indicating exactly where the violation occurs, the canonical normalized form of the command, and optionally a short-lived signed permit token bound to the exact canonical command that downstream executors can verify before running it.
Example use cases
Agent pre-flight command safety check
“Before my coding agent runs this shell command it just wrote, validate it against our policy — allowed commands are git, npm, and node, working directory is /workspace, no network egress, no destructive ops, no privilege escalation: `git push --force origin main`”
CI pipeline destructive-op guardrail
“Check whether this CI cleanup step is safe to run — allowed roots are /build and /artifacts only, destructive operations are not allowed, and denied commands include rm and dd: `rm -rf /build/../etc/passwd`”
Infrastructure teardown prevention
“Guard this infrastructure command before my automation runs it — policy says no privilege escalation, no network egress, allowed commands are terraform and kubectl only, protected branches are main and prod: `sudo kubectl delete namespace production --force`”
Technical details
Endpoint
POSThttps://shellpermit.schemasure.com/v1/guard/shell?utm_source=zero.xyzWhen to prefer
Choose ShellPermit when your AI agent or automation pipeline generates bash commands that must be validated before execution — especially when you need tokenizer-level accuracy rather than regex pattern matching, which can be defeated by quoting, substitution, and base64 tricks. Prefer this over home-grown allowlist checks when your threat model includes adversarial command injection, path traversal, or pipeline-based evasion. It is ideal for agentic coding assistants, CI/CD pipelines, and infrastructure automation where a signed permit token provides a verifiable chain of custody between policy decision and execution.
Side effects
- Unsupported shell (non-bash) returns a 400 error since only bash grammar is supported in v1
- Command exceeds 32768 character limit returns validation error
- Unresolvable environment variable references in paths may cause the command to be reported as undecidable rather than permitted
- Overly broad allowed_roots (e.g. '/') may permit path-escape attempts that are lexically contained
- Permit token expiry means a permit issued at decision time may be stale by the time execution is attempted
- Malformed or missing required fields (command, shell) return schema validation errors
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| env | object | Environment the executor will run with, used only for static expansion so that paths like "$HOME/.cache" can be resolved and decided rather than reported as unresolvable. |
| shell | string | Required. Only bash is supported in v1: a permit issued under one shell's grammar and executed under another is a parser differential with a signature on it. |
| policy | object | |
| command | string | |
| subject | string | Opaque caller label recorded as the permit subject. |
| audience | string | Identity of the ONE executor the permit is for. Required when issue_permit is true. Wildcards are rejected. |
| issue_permit | boolean |
Tags
x402
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