A pre-warmed pool of Claude Code sessions. Skip the startup wait.

Made by AI, mostly. I described the idea. Claude built it.

Why

A Claude Code session that reads a real CLAUDE.md and runs a startup protocol takes 30 to 60 seconds before you can type. Fine once. Friction when you switch contexts, reopen after a break, or want to ask one quick thing.

llm-primer keeps a couple of sessions warm in the background. When you want one, it's already past the protocol.

Install

brew tap asakin/llm-primer
brew install llm-primer

Requires tmux.

Use

primer start      # start the daemon (lazy pool of 2)
primer            # attach to a warm session
primer switch     # pre-warm a replacement when your context fills up
primer status     # see which slots are warm
primer stop       # stop the daemon

That's the default surface. Two optional modes extend it: hold mode and log filter (both opt-in, off by default, additive since v0.2.0).

How it works

primerd keeps a tmux session with N windows. Each window runs your CLI (default claude) and receives a warmup message that asks it to run its startup routine and print a marker when ready. When the pane output contains that marker (default SESSION START), the slot is marked warm.

primer attaches you to the first warm slot. A file watcher on an optional config dir rewarms slots when your CLAUDE.md changes.

Warmth is signaled by the CLI printing the marker, so detection is only as reliable as the CLI following the warmup prompt. If a slot stalls, primer logs will show the timeout.

Configuration

Environment variables, or ~/.llm-primer/config with KEY=value lines:

PRIMER_CLI=claude
PRIMER_POOL_SIZE=2
PRIMER_WARMUP_MARKER=SESSION START
PRIMER_WATCH_DIR=/path/to/your/vault/_config

The default warmup message already asks Claude to print SESSION START when its startup routine finishes, so this works on a stock Claude Code install. Override PRIMER_WARMUP_MSG or PRIMER_WARMUP_MARKER if your CLI prints something different or you want your own protocol.

Hold mode (v0.2)

Some setups don't need the warmup-and-detect dance. They just want N persistent Claude sessions that stay alive in the background, each pinned to a specific agent or flag set, attachable by name.

Hold mode does exactly that:

PRIMER_HOLD=1
PRIMER_SLOTS=claude|claude --agent engineer|claude --agent writer

Every pipe-separated entry in PRIMER_SLOTS becomes its own tmux session, named by the --agent value (or Claude for a bare claude). Each session runs under a respawn loop so if Claude exits, it comes back up within a couple of seconds.

primer              # attach to the first slot
primer attach writer # attach to a specific named slot
primer switch writer # kill + respawn that slot with a fresh process
primer status       # list slots and whether their sessions are alive

No warmup message is sent. No marker is expected. Use this when you want llm-primer to be the session holder and you want to drive Claude yourself.

Log filter (v0.2)

Optional. Off by default. When set, pipes each pane's output through a filter command into ~/.llm-primer/logs/<slot>.log, so you have a tailable record of your sessions.

PRIMER_LOG_FILTER=primer-log-filter

primer-log-filter ships with llm-primer — it strips ANSI escapes and spinner frames so the log file is plaintext-friendly. You can substitute any command that reads stdin and writes filtered stdout.

This is a privacy-sensitive feature, so it behaves loudly when enabled:

• It is off by default. You must explicitly set PRIMER_LOG_FILTER to turn it on.
• When on, primerd sends a one-time prompt into each session at startup telling Claude to announce to the user that DEBUG MODE is active and that output is being logged to a specific file. Claude will say so in its first response.
• The log path is included in the announcement so you (or anyone sharing the machine) can see exactly where logs go.

Don't use this to log somebody else's work without telling them. That's what the announcement prompt is there to prevent — the session tells the user it's logged before anything useful happens.

Tail a specific slot's log: primer logs <slot>.

What's coming

Weekly releases. Each one adds a feature and ships with a post about what we built. Open an issue if you want something specific.

License

MIT