RTK Proxy

RTK Proxy

rtk gain and the agent hooks work on bash output — what a command prints before your agent reads it. The RTK Proxy works one layer up, on the request your agent sends to the model: conversation history, tool results, file contents. It is a local HTTP daemon your agent talks to instead of talking to the model provider directly. The daemon binary is rtk-proxy; you drive it with rtk llm-proxy.

  Claude Code ──▶ rtk-proxy ──▶ api.anthropic.com
                     │
                     ├─ normalize: strip ANSI / redraws / dupes
                     ├─ your proxy.request.tool_result rules
                     ├─ (opt-in) cache-align
                     └─ record usage ──▶ rtk gain

It is local: one background process on your machine. It does four things — intercept, compress, forward, record — and does not store prompt or completion text (the opt-in CCR keeps the originals it compresses). What it compresses is in What the Proxy Compresses; its settings and endpoints are in Proxy Configuration.

Both layers are optional and independent. You can run the hooks without the proxy, the proxy without the hooks, or both — rtk gain reports them side by side.

Separate download, separate licence

The daemon is a second binary, rtk-proxy, shipped as its own release archive (rtk-proxy-<target>). It is not inside the rtk archive, because it is licensed separately — the rtk CLI is Apache-2.0, rtk-proxy is BUSL-1.1. See Editions and licensing.

Install the daemon

Download the rtk-proxy-<target> archive for your platform from the releases page and put the binary next to rtk (anywhere on your PATH also works).

From a source checkout:

cargo build --release --manifest-path proxy/Cargo.toml

rtk looks for the daemon next to its own binary first, then on PATH. If it cannot find it, rtk llm-proxy tells you exactly where it looked.

Quick start

rtk llm-proxy setup     # check the daemon is present, list agents it can serve
rtk llm-proxy start     # launch it in the background (no-op if already up)
rtk llm-proxy status    # is it running and reachable?
rtk llm-proxy stats     # usage and savings from the running daemon
rtk llm-proxy stop      # ask it to shut down

setup is the one to run first: it reports which AI agents on this machine can be pointed at the proxy, and how.

You rarely need start by hand — rtk claude starts the daemon for you. See Getting your agent onto the proxy.

Getting your agent onto the proxy

Two independent ways in. rtk init configures your agent once and persists it; rtk <harness> needs no configuration at all.

rtk init -g — the guided setup

On a Claude Code init, RTK asks:

Set up the RTK proxy (routes Claude Code's API traffic through a local daemon)? [y/N]

Say yes and it writes env.ANTHROPIC_BASE_URL into settings.json and adds extends = "rtk:proxy" to your pipeline. Then it asks how the daemon should come back after a reboot:

Choice	What it does
1. SessionStart hook (default)	Registers a hook that starts the daemon when a Claude session begins
2. Background service	rtk llm-proxy service install — a per-user service, independent of any agent
3. Neither	Prints the export line and leaves settings.json untouched

Declining leaves everything alone: “Skipped — enable later with rtk init -g or rtk llm-proxy start --env.”

If you already have the base URL set but nothing restarting the daemon, re-running rtk init -g asks only the persistence question.

What the SessionStart hook actually does

It does not do the redirection — that is the settings.json entry above. The hook is a keep-alive: when a session whose ANTHROPIC_BASE_URL points at a loopback address finds nothing listening there, it runs rtk llm-proxy start.

It reports through systemMessage, which is user-visible and never enters model context — RTK spends no tokens configuring itself. Every failure path stays silent rather than disrupting the session.

This route only exists on harnesses that have a SessionStart hook, which is why the next one matters.

rtk <harness> — the launcher

rtk claude

One command, no configuration, nothing persisted: it starts the daemon if it is not already up, points the harness at it, and execs the real binary. On Unix this is a genuine exec, so signals, stdio and the exit code behave exactly as if you had launched the harness directly.

This route needs no hook system. Not every harness has a SessionStart hook, but most offer a base-URL override — so this is how an agent without hooks still gets onto the proxy.

The daemon is agent-agnostic by design: it speaks the provider’s dialect, not the agent’s. A subcommand exists only where that redirection has been verified end to end, so rtk <harness> resolving is itself the signal that traffic really goes through the daemon. Today the list is:

Subcommand	Base-URL variable
rtk claude	ANTHROPIC_BASE_URL

A harness absent from the list is never silently unproxied — it falls through to plain passthrough. rtk llm-proxy setup reports what can be launched on this machine.

The launcher never blocks you: if the daemon cannot start, the harness launches unproxied with a warning rather than failing.

--env — one shell, by hand

eval "$(rtk llm-proxy start --env)"

Any agent launched from that shell routes through the proxy. This is choice 3 above, done manually.

Binding to another address

Start it on a different address with --bind:

rtk llm-proxy start --bind 127.0.0.1:9090

Every subcommand that talks to a running daemon (stop, status, stats) takes the same --bind flag, so you can manage a proxy that is not on the default 127.0.0.1:8080.

Runtime settings and background service

Two subcommands forward straight through to the daemon’s own CLI:

rtk llm-proxy config <args...>    # get/set runtime settings on a running proxy
rtk llm-proxy service <args...>   # manage a per-user background service

Run either with --help to see the daemon’s own options; the settings themselves are listed in Proxy Configuration. service is choice 2 of the guided setup — a per-user background service that survives logins independently of any agent.

Where it keeps its state

One fixed location, so the daemon’s state does not depend on the shell’s working directory when it was started:

Path	Contents
~/.config/rtk/llm-proxy/	daemon log and databases — on macOS ~/Library/Application Support/rtk/llm-proxy/, on Windows %APPDATA%\rtk\llm-proxy\
rtk-proxy.log	daemon log, started fresh on every start
rtk-proxy.db	usage records — the file rtk gain reads
rtk-proxy-memory.db	originals kept by CCR (opt-in), 7 days

Because the usage database lives at a known path, rtk gain can report proxy savings whether or not the daemon is currently running.

Seeing the savings

With the proxy running, a bare rtk gain switches to a live dashboard covering both layers. See Live dashboard and Attribution.

rtk gain              # live dashboard (proxy running, interactive terminal)
rtk gain --text       # force the static view
rtk gain --text --by-method  # which compression method saved what