# rentctl **Category:** ๐Ÿ’ป Developer Tools **Repository:** https://github.com/Michael-Drake/rentctl **Views:** 0 **Installs:** 0 **Upvotes:** 0 **Directory Page:** https://allmcps.com/mcp/rentctl ## Description Leased dev environments โ€” every server dies when its AI session ends. ## Claude Desktop Quick Installation Heuristic fallback โ€” verify the package name and runner against the repository README before running it. Uses `npx` (confidence: low): ```json "mcpServers": { "rentctl": { "command": "npx", "args": ["-y","rentctl"] } } ``` ## Documentation & README # rentctl **A dev server should never outlive the work that needed it.** `rentctl` *rents* dev environments to your AI coding sessions. Every environment is a **lease**: it dies when the session ends, when the lease expires, or when you say so โ€” whichever comes first. Cleanup is owned by code, not by an agent remembering to clean up. Ships as both a CLI (`rent`) and an MCP server, so an agent can start and stop environments through tools instead of shelling out to a raw `npm run dev` it will forget about. ## Why An AI coding session starts a dev server. Then the session ends โ€” crashes, is closed, or just moves on โ€” and the server keeps running. By Friday there are six of them, three are on ports you've forgotten, and one is quietly serving stale code that makes a bug look unreproducible. Telling the agent to clean up doesn't fix this, because the failure mode *is* the agent not doing what it was told. `rentctl` makes the cleanup structural: the environment has an expiry, and something other than the agent enforces it. ## Install ``` pip install rentctl ``` Requires Python 3.12+. **macOS and Linux.** There is no Windows support and no Windows claim โ€” process-group teardown is the safety-critical mechanism here, and it has no tested Windows equivalent yet. ## Enroll a project A project describes itself in a `rentctl.toml` at its repo root (a `devctl.toml` left over from before the rename is still read, so nothing needs renaming to keep working): ```toml [project] name = "myapp" # lowercase, no separators โ€” it is used as a filename runner = "process" [profiles.default] cmd = 'npm run dev -- --port "$PORT" --strictPort' cwd = "frontend" # repo-relative, never absolute port_env = "PORT" # rentctl sets this in the child's environment ``` Then, from the repo: ``` rent init ``` `init` shows you the exact command it will run, asks you to approve it, claims a block of ports for the project, and wires both the MCP server and the cleanup hooks. Nobody else has to edit anything. **There is no port field.** Ports are drawn when a server starts, not written down in a tracked file โ€” so two checkouts of the same repo get different ports instead of fighting, and a config file can't hand out a number the allocator never heard of. Each project owns a contiguous block of 10 ports. ## Use ``` rent up myapp # start (or renew) โ€” prints the URL and the port rent down --all --cwd . # stop everything leased to this directory rent ls # every environment on this machine rent sweep # reconcile: stop what's expired or dead rent events --summary # what happened, and which cleanup layer did it rent sync # re-approve a changed rentctl.toml rent report-kill myapp --note "โ€ฆ" # "you killed something I was using" ``` `report-kill` exists because `rentctl` cannot tell, on its own, whether a teardown was unwanted โ€” a kill you asked for and a kill you regret look identical from the inside. The report lands in the same append-only log as everything else and is matched to the teardown it disputes, so an unwanted kill becomes a fact on the record rather than an anecdote. Leases default to **120 minutes** and are capped at **480**. `rent up` on a live lease renews it rather than starting a second server. ## How cleanup actually happens Four independent layers, so no single failure leaves an orphan: 1. **You ask** โ€” `rent down`. 2. **The session ends** โ€” a `SessionEnd` hook, installed by `init`, tears down everything leased to that directory. 3. **The lease expires** โ€” a detached watchdog per lease kills it at expiry, even if the session died without running its hook. 4. **The next sweep** โ€” `rent sweep` reconciles anything the first three missed. There is **no daemon.** State lives on disk and the OS process table is the source of truth, so there is no background service to babysit, and nothing to resurrect after a reboot. ### It won't kill things it doesn't own Every lease records the process's PID **and its start time**. Before killing anything, `rentctl` re-checks both. If the PID was recycled onto some unrelated process, the start times disagree and it refuses โ€” a stale lease can't get your database killed. A listener inside a project's port block with no lease behind it is a **squatter**: `rentctl` routes around it and reports it. It does not kill it. And when it genuinely cannot tell whether a port is in use โ€” no usable probe on the host โ€” it says so, rather than reporting the port as free. "No squatters found" means something looked. ## Security: what you are trusting Read this part. `rentctl` runs a command out of a config file in your repo. **That is arbitrary code execution, and no tool can make it not be.** If you can run `npm run dev`, you can run anything. What `rentctl` guarantees is narrower and more useful: **it adds no *silent* path to it.** - The command from `rentctl.toml` is shown to you and approved **once**, explicitly, at `rent init`. - On approval it is copied into `rentctl`'s own registry along with a hash of the execution-determining fields. - If the repo's `rentctl.toml` later changes that command, the next start **stops** and shows you a diff of approved-versus-current. It does not run the new command. You re-approve with `rent sync` or you don't. The hash deliberately covers only the fields that determine execution, not the whole file โ€” hashing everything trains you to click through re-approvals for comment edits, which defeats the point. Consequences worth being explicit about: - **`git pull` cannot change what `rentctl` runs.** It can change the file; it cannot change the approved command. - **A repo cannot walk `rentctl` out of its own directory.** `cwd` is repo-relative and rejected if it is absolute, contains `..`, or symlinks outside the repo. Project names are filename-safe or refused. - **Non-interactive enrollment is explicit.** CI passes `--trust-repo`, which is recorded as trust-on-first-use rather than being the quiet default. - **`rentctl` only manages what you enrolled.** Test-framework servers (pytest fixtures, Playwright's `webServer`) own their own lifecycle and use ephemeral ports; `rentctl` never touches them. ### Development machines only **Install this on machines where dev servers are meant to be disposable.** Not on a host running anything you would mind losing. A default install is safe: enforcement is **advisory** everywhere, and `rentctl` only scans the port blocks of projects you enrolled. Nothing else on the machine is examined and nothing unenrolled is ever signalled. But `rentctl`'s whole job is killing processes that outlive a session, and strict enforcement exists to make that unavoidable. A tool built to reap servers you forgot about is the wrong tool to arm on a host serving traffic โ€” there, the servers outliving their session are *supposed* to. Keep it on development machines. ## Known gaps Stated plainly, because a tool making safety claims should be honest about its edges: - `runner = "compose"` is designed but not implemented. Asking for it fails with a clear error rather than doing nothing. - The only environment beyond the port is `port_env`. Anything else a server needs has to ride inside `cmd` today. - Windows: see Install. Not supported, not claimed. ## A note on the comments in the source The source cites its own design decisions โ€” `ADR-0008`, `WI-0040`, `spec ยง10`. Those refer to this project's design log, which is kept privately; the reasoning around each citation is written out where it is cited, so nothing is missing if you can't follow the pointer. ## License Apache License 2.0 โ€” see [LICENSE](https://github.com/Michael-Drake/rentctl/blob/HEAD/LICENSE) and [NOTICE](https://github.com/Michael-Drake/rentctl/blob/HEAD/NOTICE). Copyright 2026 Michael Drake.