slicervm Slicer Worktrees — git worktrees and repos inside a microVM
For coding agent sandboxes, prefer slicer <agent> --worktree [path]: it launches the VM, pushes a git worktree with a working, self-contained .git, installs the agent into that path, and attaches in one command.
Use lower-level slicer wt push when you are working with a plain VM, reusing a separately created VM, or need explicit control over the push/pull lifecycle. The host repository is never mounted and its hooks never run inside the VM.
This skill assumes a running Slicer daemon — see the use-slicer skill for connecting to one.
Why slicer wt (and not a plain copy)
A git worktree's .git is a file, not a directory:
gitdir: /home/you/src/project/.git/worktrees/feature-x
That is an absolute host path. Tar-copying the worktree directory into a VM leaves the pointer dangling — every git command in the VM fails with fatal: not a git repository. And even for a normal repo, copying .git wholesale drags host hooks and config along.
Worktree mode and slicer wt push stage a fresh, sanitised .git instead, so git works correctly in the VM and the host repo stays untouchable.
Quick start
slicer codex --worktree . # launch a persistent Codex VM and push the current worktree in
# ...let the agent work and commit in the VM...
slicer wt pull <vm> . # commits + files back, your branch fast-forwarded
git push # from the host, under your own identity
<vm> is the VM name printed by the agent command. Use slicer amp, slicer claude, slicer copilot, slicer opencode, slicer pi, or slicer workspace the same way. Use --rm when you want a disposable VM; worktree and agent sandboxes are persistent by default.
Commands
| Command | Purpose |
|---|---|
slicer codex --worktree [path] |
Launch/provision Codex, push path as a git worktree, and attach |
slicer codex --wt [path] |
Alias for --worktree |
slicer workspace --worktree [path] |
Launch a clean shell VM with a pushed worktree and no coding agent |
The same --worktree / --wt flags are available on slicer amp, slicer claude, slicer copilot, slicer opencode, and slicer pi.
Lower-level worktree commands:
| Command | Purpose |
|---|---|
slicer wt push [vm] [path] |
Push the worktree at path into an existing VM |
slicer wt push --launch [path] |
Launch a fresh persistent VM, then push |
slicer wt pull <vm> [path] |
Import the VM's commits (auto fast-forward) and files |
slicer wt list |
List worktree VMs (* marks the current directory's VM) |
path defaults to . (the current directory).
Useful flags on wt push:
| Flag | Purpose |
|---|---|
--launch |
Provision a fresh VM before pushing |
--depth N |
Shallow clone — much faster for large repos |
--force / -f |
Re-push into a VM that already has the worktree (wipes the VM-side copy first) |
--hostgroup NAME |
Host group for --launch — auto-selected only when the daemon has exactly one; required when several exist (Slicer for Mac ships with slicer and sbox, so pass e.g. --hostgroup sbox) |
--tag key=value |
Extra tags on the launched VM, or tags to match when vm is omitted |
--persistent |
Keep VM state across shutdown/restart; default true |
--rm |
Make the launched VM ephemeral, discarding state on stop/delete |
Useful flags on wt pull:
| Flag | Purpose |
|---|---|
--force / -f |
If fast-forward is impossible, reset the host branch to the VM-side branch and overwrite tracked local changes |
--no-files |
Import refs only; do not overwrite working-tree files |
--no-merge |
Import refs but skip the automatic fast-forward |
--tag key=value |
Find the VM by matching tags when vm is omitted |
--verbose / -v |
Show additional review commands |
Useful flags on wt list:
| Flag | Purpose |
|---|---|
--tag key=value |
Only list worktree VMs matching the tag; can be repeated |
What wt push does for you
- Stages a fresh, sanitised
.git— empty hooks, no foreign config — so the VM cannot reach or corrupt the host repo. - Carries over dirty and untracked files (honouring
.slicerignore). - Points
originat the https upstream (rewritinggit@…SSH remotes) so the VM cangit push— including through Slicer Proxy in isolated-network VMs. - Syncs your git identity (
user.name/user.email) and safe preferences. Credentials are never copied in. - Tags launched VMs with worktree metadata, repo name, branch, working directory, and client host/user, so
wt list,vm list, and tag matching can find them later.
What wt pull does for you
- Bundles the VM's commits and fetches them into namespaced refs
refs/slicer/<vm>/*— your own branches and refs are never clobbered. - Fast-forwards your current branch onto the VM's work, so agent commits land as real commits with a clean working tree.
- Brings back changed files.
- With
--force, preserves the previous hostHEADunderrefs/slicerbefore resetting the host branch to the VM-side branch.
⚠️ One rule
Don't edit the host worktree while a VM holds it. wt pull overwrites host files with the VM's copy — anything you changed on the host since the push is lost. Push it, let the VM/agent work, pull it back. Treat the host worktree as "checked out to the VM".
Agent sandbox worktree mode
The agent sandbox and workspace commands (slicer codex, slicer amp, slicer claude, slicer copilot, slicer opencode, slicer pi, and slicer workspace — see the use-slicer skill) accept --worktree / --wt to launch a VM, push the current git worktree, and attach in one command. Agent commands install the agent into that path; slicer workspace opens a clean shell VM instead:
slicer codex --worktree . # launch Codex with the current worktree
# ...let the agent work and commit...
slicer wt pull codex-1 . # bring the commits back, host branch fast-forwarded
git push
These VMs are persistent by default and can be relaunched/reused. Add --rm for a one-shot sandbox.
Avoid creating a provision-only agent sandbox first and then pushing into it unless you deliberately need that extra control. For normal agent work, slicer <agent> --worktree . is the intended path.
Manual VM loop
cd ~/src/myrepo
git worktree add ../myrepo-feature -b feature
cd ../myrepo-feature
slicer wt push --launch . # note the VM name it prints; persistent by default
# add --hostgroup sbox if the daemon has more than one host group
# ...work in the VM and commit there...
slicer wt pull <vm> .
git push
Availability
slicer wt is a recent addition. Run slicer wt --help to confirm it is present in your build, and update Slicer if the command is missing.