wtenv

Give each git worktree its own runtime: a port block, a database, a docker-compose project, and an env file. Remove it all again when the worktree goes.

Two coding agents in two worktrees both start a dev server on port 3000, both migrate the same database, and both docker compose up the same project, so one overwrites the other. wtenv up gives each worktree its own ports, its own copy of your database, its own compose project, and its own .env.local. wtenv down and wtenv gc take them away, and only what wtenv recorded creating.

wtenv is a local command-line tool for developers who run two to five coding agents (Claude Code, Codex, Cursor) in parallel worktrees. It starts no server and runs no daemon. It makes no network call except to the Postgres server and the Docker engine on your own machine.

60-second demo: three agents, three worktrees

wtenv.toml in the repository (this file is optional; without it you get ports and an env file only):

ports = ["PORT", "DB_PORT"]

One worktree per agent, each provisioned by running wtenv up in it:

$ git worktree add ../myapp-agent-1 -b agent-1
$ git worktree add ../myapp-agent-2 -b agent-2
$ git worktree add ../myapp-agent-3 -b agent-3

$ cd ../myapp-agent-1 && wtenv up
wtenv: provisioned /code/myapp-agent-1
  ports      20000-20009  PORT=20000 DB_PORT=20001
  env file   .env.local (created)
$ cd ../myapp-agent-2 && wtenv up
wtenv: provisioned /code/myapp-agent-2
  ports      20010-20019  PORT=20010 DB_PORT=20011
  env file   .env.local (created)
$ cd ../myapp-agent-3 && wtenv up
wtenv: provisioned /code/myapp-agent-3
  ports      20020-20029  PORT=20020 DB_PORT=20021
  env file   .env.local (created)

Each worktree now has its own block of ten ports and a .env.local that git does not show:

$ cat .env.local
# >>> wtenv managed (rewritten by `wtenv up`; do not edit) >>>
PORT=20010
DB_PORT=20011
# <<< wtenv managed <<<

$ wtenv ls
STATUS         PORTS        VARIABLES                 DATABASE  COMPOSE  PATH
provisioned    20000-20009  PORT=20000 DB_PORT=20001  -         -        /code/myapp-agent-1
provisioned    20010-20019  PORT=20010 DB_PORT=20011  -         -        /code/myapp-agent-2
provisioned    20020-20029  PORT=20020 DB_PORT=20021  -         -        /code/myapp-agent-3
unprovisioned  -            -                         -         -        /code/myapp

Start each agent's server through wtenv exec, which adds the variables of the worktree's .env.local section to a command's environment and then runs it:

$ cd ../myapp-agent-1 && wtenv exec -- npm run dev

When an agent is finished, release its resources and remove the worktree. Or remove the worktree first and let gc clean up after it:

$ cd ../myapp-agent-3 && wtenv down
wtenv: released for /code/myapp-agent-3
  removed      env_section /code/myapp-agent-3/.env.local
  removed      env_file /code/myapp-agent-3/.env.local
  removed      port_block 20020-20029
  removed      registry_entry /code/myapp/.git/worktrees/myapp-agent-3

$ git worktree remove --force ../myapp-agent-2
$ wtenv gc
wtenv: released 1 worktree(s)
  /code/myapp-agent-2
    removed      port_block 20010-20019
    removed      registry_entry /code/myapp/.git/worktrees/myapp-agent-2
    already gone env_section /code/myapp-agent-2/.env.local

Add a database and a compose project in wtenv.toml and the same two commands also create and remove a Postgres database per worktree and a compose project per worktree. See wtenv.toml.

Install

uv tool install wtenv
# or
pipx install wtenv

Requirements:

Need	When
Python 3.11 or later	Always (uv tool install fetches one if needed)
git 2.31 or later	Always
A local PostgreSQL server, 13 or later	Only with [database] type = "postgres"
Docker with Compose 2.24.4 or later	Only with [compose]

Platforms: macOS, Linux, and Windows through WSL2. Not native Windows.

Commands

wtenv has nine commands and no others. up, down, exec, hook install, and hook uninstall act on the worktree that contains the current directory. ls, gc, and doctor run anywhere. wtenv never prompts and never reads standard input (except exec, which passes it to the command it runs).

Command	What it does	Example
wtenv --version	Prints the version	wtenv --version
wtenv up	Provisions the current worktree, or brings it up to date with its wtenv.toml. Running it again with nothing changed changes nothing	wtenv up
wtenv down [--dry-run]	Releases everything recorded for the current worktree: compose project, database, port block, env-file section	wtenv down --dry-run
wtenv gc [--dry-run] [--release PATH]...	Releases the entries of worktrees that git confirms are gone, across all repositories. --release PATH names an entry whose worktree cannot be confirmed gone, such as a deleted repository	wtenv gc
wtenv ls	Lists every known worktree with its status, ports, database, and compose project	wtenv ls
wtenv exec -- COMMAND [ARG]...	Runs COMMAND with the worktree's variables in its environment, and exits with its status	wtenv exec -- pytest
wtenv doctor	Checks git, Docker, Postgres, and the registry, and finds assigned ports that another process holds	wtenv doctor
wtenv hook install	Adds a post-checkout hook block, so git worktree add runs wtenv up in the new worktree	wtenv hook install
wtenv hook uninstall [--dry-run]	Removes exactly what install added	wtenv hook uninstall

Every command takes --json.

--json and exit statuses

With --json, standard output holds exactly one JSON document, and everything else goes to standard error:

$ wtenv --version --json
{"schema_version":1,"command":"version","ok":true,"error":null,"warnings":[],"version":"0.1.0"}

$ cd /tmp && wtenv up --json
{"schema_version":1,"command":"up","ok":false,"error":{"code":"not_in_worktree","exit_status":4,"message":"not inside a git worktree: /tmp","hint":"Run wtenv from a directory inside a git worktree.","details":{"cwd":"/tmp"}},"warnings":[],"worktree":null,"changes":[],"post_up":[]}

The error codes and their exit statuses are stable. Each failure has one code and one status:

Exit	Code	Meaning
0		Success
1	internal_error	Unexpected failure inside wtenv
2	usage_error	Unknown command, option, or argument
3	config_invalid	wtenv.toml is invalid, or asks for more than the block holds
4	not_in_worktree	The current directory is not inside a git worktree
5	not_provisioned	The worktree has no completed up
6	no_free_block	No free port block in the range
7	env_file_unusable	The env file cannot be written safely
8	dependency_unavailable	git, Docker, or the Postgres server is missing, too old, not local, or refuses the connection
9	template_missing	The template database or file does not exist
10	template_in_use	The template database has open connections and cannot be copied
11	ownership_conflict	Something exists where wtenv would create a resource, and wtenv has no record of creating it
12	post_up_failed	A post_up command exited non-zero
13	partial_failure	down or gc could not remove some items; they stay recorded
14	registry_busy	The registry lock was not free within 10 seconds
15	worktree_busy	Another up or down held this worktree for more than 60 seconds
16	registry_unreadable	The registry cannot be read or locked; nothing was changed
17	problems_found	doctor found at least one problem
18	worktree_exists	gc --release named a worktree that still exists
19	unsupported	The request is valid, but v1 cannot carry it out safely in this setup

exec is the one exception, and follows env(1): it exits with the status of the command it ran. It exits 125 when wtenv itself fails (for example not_provisioned), 126 when the command was found but could not be run, and 127 when it was not found.

wtenv.toml

wtenv.toml is optional. It lives in the root of the worktree, is committed with the repository, and is read from the worktree a command runs in. Any other key, or an invalid value, is a config_invalid error that names the setting, and the command changes nothing.

# Port variables, in order. Each gets its own port from the worktree's block.
ports = ["PORT", "DB_PORT", "VITE_PORT"]
block_size = 10
env_file = ".env.local"
post_up = ["uv run alembic upgrade head"]

[database]
type = "postgres"
template = "myapp_template"
url = "postgresql://myapp:{env:MYAPP_DB_PASSWORD}@localhost:5432/{name}"

[compose]
file = "compose.yaml"

Setting	Type	Default	Rules
ports	list of strings	["PORT"]	At least one name. Names are unique and match [A-Za-z_][A-Za-z0-9_]*. DATABASE_URL is not allowed. Each gets a different port of the block, in this order
block_size	integer	10	1 to 1000. Must be at least the number of ports plus the compose ports not tied to a variable; otherwise the error states the smallest size that fits. Changing it moves the worktree to a new block
env_file	string	".env.local"	A relative path inside the worktree. Its directory must exist. The file may not be tracked by git
post_up	list of strings	[]	Shell commands, run in order with sh -c after every successful provisioning. Each must be non-empty
database	table	absent	Present: database isolation is on
database.type	"postgres" or "sqlite"	required
database.template	string	required	Postgres: the name of the template database on the shared server. SQLite: the path of the template file, relative to the worktree root or absolute
database.url	string	required	Pattern for DATABASE_URL; see below
compose	table	absent	Present: compose isolation is on
compose.file	string	required	Relative path of the compose file inside the worktree. Its file name must be compose.yaml, compose.yml, docker-compose.yaml, or docker-compose.yml

Ports come from the range 20000 to 29999, in blocks of block_size. Each worktree keeps its block until down or gc releases it.

The database URL pattern

The URL is written to DATABASE_URL in the env file. wtenv has no setting to rename the variable.

Placeholder	Replaced by
{name}	Postgres: the worktree's database name, for example wtenv_feature_x_3f9a1c2b
{path}	SQLite: the absolute path of the worktree's copy of the template
{env:NAME}	The value of the environment variable NAME when the command runs. Use it for passwords, so they are not committed. An unset variable is config_invalid

Postgres: each worktree gets CREATE DATABASE wtenv_<slug>_<id8> TEMPLATE <template> on the server named in the URL (<slug> comes from the worktree's directory name, <id8> is eight hex digits that keep two worktrees with the same name apart), so the template must exist and have no open connections. The URL must use postgresql:// or postgres://, contain {name}, and name the host explicitly as localhost, 127.0.0.1, or [::1]. SQLite: the template file is copied to <worktree>/.wtenv/, and the URL must contain {path}, for example sqlite:///{path}.

Passwords are never printed in any mode and never recorded in the registry.

Compose

With [compose], up writes a compose.override.yaml beside your compose file. It sets the project name to a name unique to the worktree and remaps every published host port to a port of the worktree's block. Plain docker compose up in the worktree then uses them, with no extra flags. Tie a service's port to one of your variables inside the compose file, the way Compose users already do:

services:
  cache:
    image: redis:7-alpine
    ports:
      - "${CACHE_PORT:-6379}:6379"

with ports = ["PORT", "CACHE_PORT"] in wtenv.toml. A published port that is not tied to a variable gets the next free port of the block. The override file is added to .git/info/exclude, as is the env file, so git status stays clean.

Changing the configuration later

The next up applies the change: a new ports list reassigns ports inside the same block; a new block_size moves the worktree to a new block; a new env_file moves the section and removes it from the old file; a changed database.url rewrites DATABASE_URL and keeps the existing database (it is never re-created from a new template); removing [database] or [compose] stops managing them but keeps what exists recorded until down.

Working with Claude Code

Claude Code switches git hooks off when it creates a worktree (claude --worktree), so the post-checkout hook does not provision worktrees Claude Code makes. Add this line to your project's CLAUDE.md:

Before starting servers or running migrations in a new worktree, run `wtenv up` in it.

wtenv exec fails with not_provisioned and a hint naming wtenv up if an agent forgets.

Do not list wtenv's env file in .worktreeinclude: Claude Code would copy the main checkout's file, with its ports, into each new worktree until wtenv up rewrites it.

Worktrees that Claude Code removes become orphaned, and wtenv gc reclaims them. Run gc after removal: git has no hook for worktree removal, so nothing can run down for you.

For worktrees you create yourself with git worktree add, run wtenv hook install once per clone and the hook provisions each new worktree.

Known limits

wtenv v1 prefers to refuse than to guess. These are the limits you can hit.

Cleanup

• Anonymous volumes stay on disk. Docker gives the compose project label only to named volumes, so an anonymous volume of a removed project cannot be tied to it. down and gc never remove one; they list it under kept_volumes. Remove it yourself with docker volume rm NAME once you are sure it holds nothing you need.
• A volume with a fixed name: stays too, because the main checkout and every worktree share it. up warns about it (compose_fixed_volume_name). That warning fires only for a volume a service mounts: Compose leaves unused top-level volumes out of the resolved model wtenv reads, so an unused one is neither warned about nor listed.
• Nothing is removed unless wtenv recorded creating it. A database or file that merely has a wtenv_ name is left alone.

Compose

• One compose file per worktree, named compose.yaml, compose.yml, docker-compose.yaml, or docker-compose.yml. Those are the only names plain docker compose finds, and wtenv adds no flags.
• If an override file with one of the four override names already exists and wtenv did not create it, up fails with ownership_conflict. wtenv does not modify your override.
• COMPOSE_PROJECT_NAME or COMPOSE_FILE set in the environment or in .env beside the compose file beats the override, so up fails with unsupported instead of silently not isolating.
• A host port range published onto one container port ("8000-9000:80") is unsupported: Compose picks the port at start, so it cannot be pinned.
• Compose 2.24.4 or later is required (!override).

Databases

• Postgres over local TCP only: the host must be localhost, 127.0.0.1, or [::1]. Unix-socket URLs and remote servers are refused.
• Postgres cannot copy a database with open connections. If something is connected to the template, up fails at once with template_in_use and changes nothing.
• A SQLite template with a non-empty write-ahead log (-wal) file is refused for the same reason.

Platform and git

• macOS and Linux (WSL2 counts). No native Windows.
• Ports are tested for TCP only.
• The hook runs only for a plain git worktree add. --no-checkout and --orphan run no post-checkout hook, hooks are not cloned (install once per clone), and a caller can switch them off. If core.hooksPath points elsewhere, hook install refuses and prints the block for you to add to your hook manager.
• A worktree you deleted by hand while git still lists it is kept until git worktree prune. A deleted repository is kept until you name it with gc --release PATH.

wtenv and the alternatives

wtenv does one narrow job. It is not a replacement for the tools below, and for some situations they are the better choice.

Dev containers. A dev container puts your whole toolchain and your code in a container, so every developer and every worktree starts from the same environment. wtenv does not do that: your code and tools run on your machine as they do today, and wtenv only separates the runtime resources they use (ports, database, compose project, env file). That makes it light, with no container to build and no editor integration, and it also means it cannot give you a reproducible toolchain or isolate the filesystem. If you need those, use a dev container. Each dev container still needs its own answer to "which port, which database", which is the part wtenv covers.

Hand-rolled scripts. A shell script or Makefile target that picks a port and runs createdb is quick to write and does exactly what you tell it. If your need is one port and one SQLite file, it may be all you need. What it usually lacks is what wtenv adds: ports that cannot collide when two agents start at the same moment, a record of what was created so down removes that and nothing else, cleanup after a worktree is deleted without running down, a dry run, and the same exit codes and JSON every time. The price is that wtenv supports only what is listed above; a script can do anything.

Cloud preview environments. A preview environment gives each branch or pull request a full, production-like deployment with a shareable URL, and it costs your machine nothing. It needs a push, a build, and time to deploy, and it fits review better than the edit-and-run loop of an agent working on uncommitted code. wtenv is local: free, immediate, and nothing leaves your machine, but it cannot share a running environment with a teammate and it is not production-like.

License

Apache License 2.0. See LICENSE.