Runtime

What are least-privilege API keys?

A least-privilege API key can do only what its one job needs, such as reading without changing, so a leaked key does less harm.

On Runtime any key can be made read-only or given a daily spending limit, and no key can loosen its own terms. A read-only key sees the whole account and spends nothing; a limited key's agent can commit at most the sum you set in any 24 hours (security).

Why it matters for AI agents

NIST defines least privilege as restricting access "to the minimum necessary to accomplish assigned tasks". An agent is the case the rule was written for. It runs on instructions it did not write, it can be steered by text in a file or a web page, and it acts fast and without pause. A dashboard that only reads should hold a key that only reads. A coding agent that creates sandboxes all night should hold a key with a ceiling on what it can spend. Then a mistake or an injected instruction is bounded by the key, not by the account.

One key per agent helps too. Each shows up separately in the audit log, and revoking one leaves the others working.

Runtime's key controls

Control What it does
Read-only key Sees every sandbox's state, spec and cost, images, volumes, snapshots, balance; changes nothing
Not visible to it Files and command output inside sandboxes, job runs and secrets
Daily spending limit The most a key's agent may commit in any 24 hours, settled charges plus money on hold
Past the limit Create, wake, extension or renewal fails with spending_limit_reached (HTTP 402), no charge
Per create maxCostMicros refuses a create whose first lease would cost more
Who sets limits The member who made the key, or an owner or admin, on the website; no key can
Record Every key made, revoked or limited is in the audit log, with who and from where

Both controls are optional, and they cover every Cloud product, including products added later.

Make and check one

From a terminal, each request opens a browser approval for an owner, admin or developer:

Terminalruntime keys create --name monitor --read-onlyruntime keys create --name nightly-agent --daily-limit 25

Code running on a key can read its own terms before it starts work:

TypeScriptimport { Runtime } from "withruntime";const runtime = new Runtime();const { access, daily } = await runtime.limits.get();console.log(access, daily.remainingMicros); // "read", "full" or "selected"
Pythonfrom withruntime import Runtimewith Runtime() as runtime:    limits = runtime.limits.get()    print(limits["access"], limits["daily"]["remainingMicros"])

An agent connected through MCP asks the same with runtime_limits_get. A client that asks for the scope runtime:read during MCP sign-in gets a read-only key (remote connection). A spending_limit_reached error is not retried by the SDKs: the agent should stop and tell the person it works for.

Room under a limit comes back as older spending leaves the 24-hour window. A running sandbox keeps its current lease when the limit is reached; one that needs a renewal past it stops or pauses when its lease ends.

Sources

Facts on this page were checked on 25 September 2026.

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