diff --git a/.gitignore b/.gitignore
index 4ab3d4f..4c49bd7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1 @@
 .env
-entrypoint.sh
diff --git a/Dockerfile b/Dockerfile
deleted file mode 100644
index b7d0370..0000000
--- a/Dockerfile
+++ /dev/null
@@ -1,69 +0,0 @@
-FROM node:22-slim
-
-# System dependencies:
-#   - curl/ca-certificates: downloads (Claude Code installer, nvm, git-spice)
-#   - git + ripgrep: Claude Code requirements
-#   - build-essential, libssl-dev, libreadline-dev, zlib1g-dev: rbenv/ruby-build deps
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    curl \
-    ca-certificates \
-    git \
-    ripgrep \
-    bash \
-    build-essential \
-    libssl-dev \
-    libreadline-dev \
-    zlib1g-dev \
-    libffi-dev \
-    libyaml-dev \
-    libpq-dev \
-    socat \
-    chromium \
-    chromium-driver \
-    && rm -rf /var/lib/apt/lists/*
-
-# Selenium/Capybara discover Chrome via these env vars.
-# chromium-driver installs chromedriver at /usr/bin/chromedriver.
-ENV CHROME_BIN=/usr/bin/chromium
-ENV CHROMEDRIVER=/usr/bin/chromedriver
-
-# --- rbenv (installed into home volume on first run, via entrypoint) ---
-# RBENV_ROOT points into the home volume so the install persists across rebuilds.
-ENV RBENV_ROOT=/home/coder/.rbenv
-ENV PATH="$RBENV_ROOT/bin:$RBENV_ROOT/shims:$PATH"
-
-# Initialise rbenv shims for all bash sessions (no-op if not yet installed)
-RUN echo '[ -d "$RBENV_ROOT/bin" ] && eval "$(rbenv init - bash)"' >> /etc/bash.bashrc
-
-# --- nvm (installed into home volume on first run, via entrypoint) ---
-# NVM_DIR points into the home volume so the install persists across rebuilds.
-ENV NVM_DIR=/home/coder/.nvm
-
-# Source nvm for all bash sessions (nvm.sh is a no-op if not yet installed)
-RUN echo '[ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"' >> /etc/bash.bashrc
-
-# --- git-spice ---
-# Releases are named git-spice.Linux-<arch>.tar.gz; uname -m gives the right arch directly.
-RUN ARCH=$(uname -m) && \
-    GS_VERSION=$(curl -fsSL https://api.github.com/repos/abhinav/git-spice/releases/latest \
-        | grep '"tag_name"' | sed 's/.*"v\([^"]*\)".*/\1/') && \
-    mkdir -p /tmp/gs-install && \
-    curl -fsSL "https://github.com/abhinav/git-spice/releases/download/v${GS_VERSION}/git-spice.Linux-${ARCH}.tar.gz" \
-        | tar -xz -C /tmp/gs-install && \
-    find /tmp/gs-install -maxdepth 1 -type f -executable -exec cp {} /usr/local/bin/gs \; && \
-    chmod +x /usr/local/bin/gs && \
-    rm -rf /tmp/gs-install
-
-# --- non-root user ---
-RUN useradd -m -s /bin/bash -u 1001 coder
-
-# Claude Code native installer lands in ~/.local/bin or ~/.claude/bin
-ENV PATH="/home/coder/.local/bin:/home/coder/.claude/bin:$PATH"
-
-COPY --chmod=755 entrypoint.sh /usr/local/bin/entrypoint.sh
-
-USER coder
-WORKDIR /code
-
-ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
-CMD ["bash"]
diff --git a/Dockerfile.base b/Dockerfile.base
new file mode 100644
index 0000000..4d0d458
--- /dev/null
+++ b/Dockerfile.base
@@ -0,0 +1,61 @@
+# safeclaude-base — the shared base every project builds on. Keep this generic:
+# project-specific packages and language versions go in each project's own
+# .safeclaude/Dockerfile (which starts with `FROM safeclaude-base`), not here.
+#
+# This image runs as root so project Dockerfiles can install system packages
+# freely. Don't worry — the launcher locks things down at run time (normal user,
+# no special privileges), so nothing Claude does actually runs as root.
+#
+# Debian (slim) as the base: small, stable, and its apt packages behave
+# predictably in a container — notably `chromium` is a real package here, unlike
+# on Ubuntu where it's a snap stub that won't run in a container.
+FROM debian:bookworm-slim
+
+# Just the basics every project needs:
+#   - curl/ca-certificates: for downloads (the Claude installer, git-spice)
+#   - git + ripgrep: required by Claude Code
+# We leave apt's package lists in place (no cleanup) so a project Dockerfile can
+# install packages without re-fetching them — though it should still run its own
+# `apt-get update` first, since this base image may be days or weeks old.
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    curl \
+    ca-certificates \
+    git \
+    ripgrep \
+    bash
+
+# --- git-spice (a tool for stacked pull requests, handy in the Claude workflow) ---
+# Releases are named git-spice.Linux-<arch>.tar.gz, and `uname -m` gives the arch.
+RUN ARCH=$(uname -m) && \
+    GS_VERSION=$(curl -fsSL https://api.github.com/repos/abhinav/git-spice/releases/latest \
+        | grep '"tag_name"' | sed 's/.*"v\([^"]*\)".*/\1/') && \
+    mkdir -p /tmp/gs-install && \
+    curl -fsSL "https://github.com/abhinav/git-spice/releases/download/v${GS_VERSION}/git-spice.Linux-${ARCH}.tar.gz" \
+        | tar -xz -C /tmp/gs-install && \
+    find /tmp/gs-install -maxdepth 1 -type f -executable -exec cp {} /usr/local/bin/gs \; && \
+    chmod +x /usr/local/bin/gs && \
+    rm -rf /tmp/gs-install
+
+# --- the user Claude runs as ---
+# We create 'coder' with the *host* user's UID/GID (passed in by the launcher).
+# This is what makes the bind-mounted project at /code writable: the files there
+# keep the host's ownership, so the container can only write them if it runs as
+# that same ID. It also means files Claude creates come out owned by you on the
+# host — not root or some stray ID. The launcher rebuilds this image if the host
+# ID ever changes (it reads the labels below to notice), so the default here is
+# just a placeholder for a from-scratch build.
+ARG HOST_UID=1000
+ARG HOST_GID=1000
+RUN if ! getent group "${HOST_GID}" >/dev/null; then groupadd -g "${HOST_GID}" coder; fi && \
+    useradd -m -s /bin/bash -u "${HOST_UID}" -g "${HOST_GID}" coder
+LABEL safeclaude.uid="${HOST_UID}" safeclaude.gid="${HOST_GID}"
+
+# Claude installs itself into one of these folders, so add them to PATH.
+ENV PATH="/home/coder/.local/bin:/home/coder/.claude/bin:$PATH"
+
+COPY --chmod=755 entrypoint.sh /usr/local/bin/entrypoint.sh
+
+WORKDIR /code
+
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
+CMD ["bash"]
diff --git a/README.md b/README.md
index e4bfadd..4c7218b 100644
--- a/README.md
+++ b/README.md
@@ -1,33 +1,88 @@
-# Claude Code — Dockerized
+# safeclaude
 
-A minimal, guardrailed container for running Claude Code.
+Run Claude Code inside a locked-down container, one per project. Your code is
+shared with the container so Claude can edit it, but everything Claude *runs*
+stays boxed in — so a bad command can't touch the rest of your machine.
 
-## Setup
+It works like a language version manager (think `rvm`/`nvm`/`pyenv`): this repo
+holds only the **shared plumbing**, and each project keeps its own setup in a
+small `.safeclaude/` folder. When you launch, safeclaude reads that folder,
+builds the container once, and reuses it after that.
+
+## Install
 
 ```bash
-# 1. Build the image
-docker compose build
-
-# 2. Link the binary where it's accessible
-ln -s `readlink -f ./safeclaude` `readlink -f ~/.local/bin`
-
-# 3. Run against your code
-cd ~/zenmaid-webapp && safeclaude .
+# Put the launcher on your PATH (any dir on your PATH works)
+ln -s "$(readlink -f ./safeclaude)" ~/.local/bin/safeclaude
 ```
 
-## Security notes
+That's it — the first launch builds what it needs automatically.
 
-- Runs as a non-root user (`coder`, uid 1001)
-- All Linux capabilities are dropped except `NET_BIND_SERVICE`
-- Privilege escalation is disabled (`no-new-privileges`)
-- The container has no network restrictions beyond what Docker provides —
-  add a custom network or `--network none` with `--add-host` if you want
-  to lock that down further
+## Use
 
-## Limitations & future updates
+```bash
+cd ~/my-project
+safeclaude init        # create a .safeclaude/ folder, then edit it for your project
+safeclaude             # launch Claude in this project's container
+```
 
-- System package requirement changes require updates to the Dockerfile and a restart/rebuild - the claude user can't make these changes itself due to restricted access.
+| Command | What it does |
+| --- | --- |
+| `safeclaude [claude-args...]` | Launch Claude for the project here. Anything extra is passed straight to `claude`. |
+| `safeclaude build` | Rebuild the project's container from scratch. |
+| `safeclaude init` | Create a starter `.safeclaude/` in the current directory. |
+| `safeclaude envs` | List the containers and stored data safeclaude has created. |
+| `safeclaude version` | Print the safeclaude version. |
 
-- Bundles need to be updated separately inside the container
+safeclaude always works on the project you're in — the current directory, or the
+nearest parent that has a `.safeclaude/` folder, so launching from a
+subdirectory still finds the right one.
 
-- The setup is fairly tightly married to a ruby/psql application and would need to be tweaked to be configurable for other environments or platforms
+## What goes in `.safeclaude/`
+
+```
+.safeclaude/
+  Dockerfile   # which system packages / language versions this project needs
+  hooks/       # setup scripts that run each time the container starts
+  cache/       # scratch space on the host, gitignored (dependencies, downloads…)
+  .env         # secrets, kept out of git (.env.example shows the format)
+  version      # the safeclaude version this config was created with
+  README.md    # how this environment works and how to change it
+```
+
+That `README.md` is also what the sandboxed Claude reads to learn how the
+environment is set up — so it can tell you exactly what to change without
+digging through your project.
+
+A few things worth knowing:
+
+- **Two places setup can live, and the difference matters.** Slow, one-time
+  installs (system packages, a pinned language version) go in the `Dockerfile` —
+  these get cached, so they don't repeat. Anything that needs your actual code
+  present, or that should persist between runs (installing dependencies,
+  starting a database proxy), goes in a `hooks/` script that runs at launch.
+- **It only rebuilds when something changed.** safeclaude remembers what it
+  already built, so a normal launch starts right up with no waiting.
+- **Hooks are safe to run every time.** They check before doing work, so a
+  launch with nothing to do is near-instant.
+- **`cache/` is your scratch space.** It lives on the host and is gitignored, so
+  it survives rebuilds and `docker volume` resets without ending up in your repo
+  — a good home for installed dependencies, downloads, or "already did this"
+  markers.
+
+See [`example/`](example/) for a real, filled-in Ruby + Postgres setup you can
+copy from.
+
+## Security
+
+These are applied every launch, by safeclaude itself — a project's own config
+can't loosen them:
+
+- Claude runs as a normal user, not root, so it can't make system-wide changes.
+- The container is stripped of special privileges it doesn't need.
+- It can't gain new privileges partway through.
+- Each project gets its own private storage, so one project can't see or break
+  another's setup.
+
+Network access is otherwise normal. If you want to cut it off, that's a small
+change in the launcher.
diff --git a/docker-compose.yml b/docker-compose.yml
deleted file mode 100644
index 6551c94..0000000
--- a/docker-compose.yml
+++ /dev/null
@@ -1,40 +0,0 @@
-services:
-  claude-code:
-    build: .
-    image: claude-code:local
-    container_name: claude-code
-
-    volumes:
-      # Fixed home volume — persists Claude Code install, config, and credentials
-      # across container restarts and image rebuilds.
-      - claude-home:/home/coder
-
-      # Swappable project folder — override PROJECT_DIR to point at any directory:
-      #   PROJECT_DIR=/path/to/myproject docker compose run --rm claude-code
-      - ${PROJECT_DIR:-./code}:/code
-
-    # Drop all Linux capabilities except NET_BIND_SERVICE, which socat needs
-    # to proxy port 5432 on 127.0.0.1 inside the container.
-    cap_drop:
-      - ALL
-    cap_add:
-      - NET_BIND_SERVICE
-    security_opt:
-      - no-new-privileges:true
-
-    # Allow the container to reach the host's network (e.g. a local postgres).
-    # On Linux, host.docker.internal isn't automatic — this creates it.
-    # On Mac/Windows Docker Desktop it's already available but this is harmless.
-    extra_hosts:
-      - "host.docker.internal:host-gateway"
-
-    # Interactive terminal so `claude` works properly
-    stdin_open: true
-    tty: true
-
-    working_dir: /code
-
-volumes:
-  claude-home:
-    # Named volume — Docker manages it; survives `docker compose down`
-    # (use `docker compose down -v` to wipe it along with the install)
diff --git a/entrypoint.sh b/entrypoint.sh
new file mode 100755
index 0000000..0306505
--- /dev/null
+++ b/entrypoint.sh
@@ -0,0 +1,26 @@
+#!/bin/bash
+# This runs every time a container starts. Keep it generic — anything specific
+# to a project (language versions, installing dependencies, and so on) belongs
+# in that project's .safeclaude/hooks/, not here.
+set -e
+
+# Install Claude if it isn't already here. The home folder is saved between
+# runs, so this only actually downloads the first time.
+if ! command -v claude &>/dev/null; then
+  echo "[safeclaude] Claude Code not found — installing..."
+  curl -fsSL https://claude.ai/install.sh | bash
+fi
+
+# Run the project's setup scripts, in name order. They're read straight from the
+# project folder, so editing one takes effect next launch — no rebuild needed.
+# If a script fails we stop here, rather than start in a half-set-up container.
+HOOK_DIR="/code/.safeclaude/hooks"
+if [ -d "$HOOK_DIR" ]; then
+  for hook in "$HOOK_DIR"/*.sh; do
+    [ -e "$hook" ] || continue
+    echo "[safeclaude] hook: $(basename "$hook")"
+    bash "$hook"
+  done
+fi
+
+exec "$@"
diff --git a/entrypoint.sh.example b/entrypoint.sh.example
deleted file mode 100644
index f29fc3e..0000000
--- a/entrypoint.sh.example
+++ /dev/null
@@ -1,73 +0,0 @@
-#!/bin/bash
-set -e
-
-# Install nvm if not already present in the home volume.
-if [ ! -s "$NVM_DIR/nvm.sh" ]; then
-  echo "nvm not found — running installer..."
-  curl -fsSL https://raw.githubusercontent.com/nvm-sh/nvm/HEAD/install.sh |
-    NVM_DIR="$NVM_DIR" PROFILE=/dev/null bash
-  echo "nvm installed successfully."
-fi
-. "$NVM_DIR/nvm.sh"
-
-# Install rbenv + ruby-build if not already present in the home volume.
-if [ ! -d "$RBENV_ROOT/bin" ]; then
-  echo "rbenv not found — installing..."
-  git clone --depth=1 https://github.com/rbenv/rbenv.git "$RBENV_ROOT"
-  git clone --depth=1 https://github.com/rbenv/ruby-build.git "$RBENV_ROOT/plugins/ruby-build"
-  echo "rbenv installed successfully."
-fi
-eval "$(rbenv init - bash)"
-
-# Determine the desired Ruby version: prefer .ruby-version in the workspace,
-# fall back to the rbenv global setting, then a hardcoded default.
-if [ -f "/code/.ruby-version" ]; then
-  RUBY_VERSION=$(tr -d '[:space:]' </code/.ruby-version)
-elif [ -f "$RBENV_ROOT/version" ]; then
-  RUBY_VERSION=$(cat "$RBENV_ROOT/version")
-else
-  RUBY_VERSION="3.3.6"
-fi
-
-# Install the Ruby version if it isn't already built.
-if ! rbenv versions --bare 2>/dev/null | grep -qx "$RUBY_VERSION"; then
-  echo "Ruby $RUBY_VERSION not found — installing (this may take a few minutes)..."
-  rbenv install "$RUBY_VERSION"
-  echo "Ruby $RUBY_VERSION installed."
-fi
-rbenv global "$RUBY_VERSION"
-
-# Ensure bundler is available for this Ruby version.
-if ! gem list bundler -i &>/dev/null; then
-  gem install bundler --no-document
-fi
-
-# Install gem dependencies for the linked workspace so rspec (and other gems)
-# are available without needing an explicit `bundle install` step.
-if [ -f "/code/Gemfile" ]; then
-  echo "Gemfile found — running bundle install..."
-  pushd /code
-  BUNDLE_GEMS__GRAPHQL__PRO="gql_2e0_d66f5103067:70c113ba329" bundle install
-  popd
-fi
-
-# Install Claude Code if not already present in the home volume.
-# Because the home directory is a volume, this install persists across
-# container restarts and rebuilds.
-if ! command -v claude &>/dev/null; then
-  echo "Claude Code not found — running installer..."
-  curl -fsSL https://claude.ai/install.sh | bash
-  echo "Claude Code installed successfully."
-else
-  echo "Claude Code $(claude --version 2>/dev/null || echo '(version unknown)') ready."
-fi
-
-# Proxy host postgres to 127.0.0.1:5432 inside the container so the app can
-# use the same DATABASE_URL whether running inside or outside Docker.
-if ! ss -tlnp 2>/dev/null | grep -q ':5432'; then
-  echo "Starting postgres proxy 127.0.0.1:5432 -> host.docker.internal:5432"
-  socat TCP-LISTEN:5432,bind=127.0.0.1,fork,reuseaddr \
-    TCP:host.docker.internal:5432 &
-fi
-
-exec "$@"
diff --git a/example/.safeclaude/.env.example b/example/.safeclaude/.env.example
new file mode 100644
index 0000000..d39450c
--- /dev/null
+++ b/example/.safeclaude/.env.example
@@ -0,0 +1,3 @@
+# Copy to .env (gitignored) for secrets injected into the container at runtime.
+# Private gem registry token used by hooks/20-bundle.sh:
+# BUNDLE_GEMS__GRAPHQL__PRO=user:token
diff --git a/example/.safeclaude/.gitignore b/example/.safeclaude/.gitignore
new file mode 100644
index 0000000..dd7d4ab
--- /dev/null
+++ b/example/.safeclaude/.gitignore
@@ -0,0 +1,2 @@
+.env
+cache/
diff --git a/example/.safeclaude/Dockerfile b/example/.safeclaude/Dockerfile
new file mode 100644
index 0000000..3814e68
--- /dev/null
+++ b/example/.safeclaude/Dockerfile
@@ -0,0 +1,50 @@
+# Example .safeclaude/Dockerfile for a Ruby + Postgres app.
+#
+# Everything here runs once when the container is built (and is cached), so it
+# won't slow down launches. You're root during the build, so apt just works.
+FROM safeclaude-base:latest
+
+# System packages: what's needed to build Ruby, talk to Postgres, proxy the
+# database (socat), run browser tests (headless Chrome), and unpack the Node
+# download below (xz-utils).
+RUN apt-get update && apt-get install -y --no-install-recommends \
+      build-essential \
+      libssl-dev libreadline-dev zlib1g-dev libffi-dev libyaml-dev \
+      libpq-dev \
+      socat \
+      chromium chromium-driver \
+      xz-utils
+
+# Capybara/Selenium look for Chrome at these paths.
+ENV CHROME_BIN=/usr/bin/chromium
+ENV CHROMEDRIVER=/usr/bin/chromedriver
+
+# --- Ruby (one pinned version) ---
+# A project only ever needs one Ruby, so we install it straight into /usr/local
+# instead of running a version manager. ruby-build (the tool rbenv uses under the
+# hood) does the download + compile. To change versions, bump RUBY_VERSION and
+# rebuild with `safeclaude build`.
+ARG RUBY_VERSION=3.3.6
+RUN git clone --depth 1 https://github.com/rbenv/ruby-build.git /tmp/ruby-build && \
+    PREFIX=/usr/local /tmp/ruby-build/install.sh && \
+    rm -rf /tmp/ruby-build && \
+    ruby-build "$RUBY_VERSION" /usr/local && \
+    gem install bundler --no-document
+
+# Gems install into the project's cache folder (which lives on the host), so they
+# persist between runs and survive container/volume resets. The bundle hook
+# relies on this too. BUNDLE_PATH is set here so both the hook and your app see it.
+ENV BUNDLE_PATH=/code/.safeclaude/cache/bundle
+
+# --- Node (one pinned version) ---
+# Same idea: download one Node and unpack it into /usr/local. Bump NODE_VERSION
+# and rebuild to change it.
+ARG NODE_VERSION=22.11.0
+RUN arch="$(uname -m)" && \
+    case "$arch" in \
+      x86_64) narch=x64 ;; \
+      aarch64) narch=arm64 ;; \
+      *) echo "unsupported arch: $arch" >&2; exit 1 ;; \
+    esac && \
+    curl -fsSL "https://nodejs.org/dist/v${NODE_VERSION}/node-v${NODE_VERSION}-linux-${narch}.tar.xz" \
+      | tar -xJ -C /usr/local --strip-components=1
diff --git a/example/.safeclaude/README.md b/example/.safeclaude/README.md
new file mode 100644
index 0000000..0add8b9
--- /dev/null
+++ b/example/.safeclaude/README.md
@@ -0,0 +1,35 @@
+# .safeclaude/ — this project's sandboxed environment
+
+This folder defines the container that `safeclaude` runs Claude in. The container
+is built from these files, so changing the environment means editing them on the
+host and rebuilding — not installing things inside the running container (which
+is a non-root sandbox and gets reset each run).
+
+## What's here
+
+- `Dockerfile` — the container image: system packages and pinned language
+  versions (one Ruby, one Node, etc.). Built once, then cached.
+- `hooks/*.sh` — scripts that run at every startup, with the project at `/code`.
+  Use these for setup that needs your code present or should run each launch
+  (installing dependencies, starting a service proxy). Keep them safe to re-run.
+- `cache/` — scratch space on the host, gitignored. A good home for installed
+  dependencies, downloads, or "already did this" markers; survives rebuilds and
+  `docker volume` resets.
+- `.env` — secrets passed into the container at runtime (gitignored; copy from
+  `.env.example`).
+- `version` — the safeclaude version this config was created with.
+
+## How to change the environment
+
+The container runs as a non-root user with no sudo, so you can't install system
+packages from inside it. Instead, edit these files on the host:
+
+- **Add a system package:** add it to `Dockerfile`, then run `safeclaude build`.
+- **Add a language or tool:** install a specific version in `Dockerfile` — pin
+  it, since a project only needs one. See the repo's `example/` for a worked
+  Ruby + Node setup.
+- **Run setup at startup:** add or edit a script in `hooks/` (no rebuild needed).
+- **Add a secret:** put it in `.env` (see `.env.example`).
+
+After editing the `Dockerfile`, run `safeclaude build` to rebuild. Hook, `.env`,
+and `cache/` changes take effect on the next launch with no rebuild.
diff --git a/example/.safeclaude/hooks/20-bundle.sh b/example/.safeclaude/hooks/20-bundle.sh
new file mode 100755
index 0000000..c7358fa
--- /dev/null
+++ b/example/.safeclaude/hooks/20-bundle.sh
@@ -0,0 +1,25 @@
+#!/bin/bash
+# Installs gems, but only when Gemfile.lock has changed: it remembers the last
+# version it installed, so an unchanged lockfile is a near-instant no-op.
+#
+# Both the gems (via BUNDLE_PATH, set in the Dockerfile) and the marker below
+# live in /code/.safeclaude/cache — on the host, so they persist between runs
+# and stay out of git. Ruby is already on PATH from the Dockerfile, so there's
+# no version manager to initialize here.
+set -euo pipefail
+
+[ -f /code/Gemfile ] || exit 0
+
+CACHE=/code/.safeclaude/cache
+mkdir -p "$CACHE"
+LOCK=/code/Gemfile.lock
+MARKER="$CACHE/gemfile.sha"
+CUR="$( [ -f "$LOCK" ] && sha256sum "$LOCK" | cut -d' ' -f1 || echo no-lock )"
+
+if [ "$(cat "$MARKER" 2>/dev/null || true)" != "$CUR" ]; then
+  echo "[bundle] installing gems..."
+  # The token below (for a private gem source) comes from .safeclaude/.env — see
+  # .env.example. It's fine to leave unset if your project doesn't need it.
+  ( cd /code && BUNDLE_GEMS__GRAPHQL__PRO="${BUNDLE_GEMS__GRAPHQL__PRO:-}" bundle install )
+  echo "$CUR" > "$MARKER"
+fi
diff --git a/example/.safeclaude/hooks/30-pg-proxy.sh b/example/.safeclaude/hooks/30-pg-proxy.sh
new file mode 100755
index 0000000..353bd8c
--- /dev/null
+++ b/example/.safeclaude/hooks/30-pg-proxy.sh
@@ -0,0 +1,15 @@
+#!/bin/bash
+# Makes the host machine's Postgres reachable at the usual 127.0.0.1:5432 inside
+# the container, so your database settings work the same in or out of Docker.
+set -euo pipefail
+
+# If something's already answering on 5432 (like a proxy from a previous launch),
+# leave it be. We test the port with a built-in bash trick so we don't have to
+# install extra tools just to check.
+if (exec 3<>/dev/tcp/127.0.0.1/5432) 2>/dev/null; then
+  exec 3>&-   # port answered — already running
+else
+  echo "[pg] proxying 127.0.0.1:5432 -> host.docker.internal:5432"
+  socat TCP-LISTEN:5432,bind=127.0.0.1,fork,reuseaddr \
+        TCP:host.docker.internal:5432 &
+fi
diff --git a/example/.safeclaude/version b/example/.safeclaude/version
new file mode 100644
index 0000000..6e8bf73
--- /dev/null
+++ b/example/.safeclaude/version
@@ -0,0 +1 @@
+0.1.0
diff --git a/example/README.md b/example/README.md
new file mode 100644
index 0000000..2bced8b
--- /dev/null
+++ b/example/README.md
@@ -0,0 +1,34 @@
+# Example: a Ruby + Postgres project
+
+A filled-in `.safeclaude/` for a typical Rails-style app — a pinned Ruby and
+Node, the Postgres client, and headless Chrome for browser tests. It's here as a
+reference you can copy from when setting up your own project.
+
+## How to use it
+
+- **Start fresh, then borrow:** run `safeclaude init` in your project for a blank
+  starter, then copy whatever pieces you need from here. (Recommended — you only
+  pull in what applies to you.)
+- **Copy the whole thing:** `cp -r .../safeclaude/example/.safeclaude ~/your-project/`
+  and tweak from there.
+
+## What's where
+
+| File | When it runs | What it does |
+| --- | --- | --- |
+| `.safeclaude/Dockerfile` | once, then cached | installs system packages, a pinned Ruby + Node, Chrome, and bundler |
+| `hooks/20-bundle.sh` | each launch | runs `bundle install`, but only when `Gemfile.lock` changed |
+| `hooks/30-pg-proxy.sh` | each launch | lets the app reach the host's Postgres at the usual `127.0.0.1:5432` |
+| `.env.example` | — | copy to `.env` for a private gem token (kept out of git) |
+| `version` | — | the safeclaude version this config was created with |
+| `README.md` | — | how this environment works (also read by the sandboxed Claude) |
+
+A couple of things to take away:
+
+- Slow, one-time installs go in the **Dockerfile** so they're cached. Pin one
+  Ruby and one Node there directly — a project only needs one of each, so a
+  version manager would just be overhead. Anything that needs your code present,
+  or has to stick around between runs, goes in a **hook**.
+- `cache/` is the project's scratch space, on the host and gitignored. Here the
+  gems install into it (`BUNDLE_PATH`), so they survive container and volume
+  resets without ever touching your repo.
diff --git a/safeclaude b/safeclaude
index 4f123f5..e2db711 100755
--- a/safeclaude
+++ b/safeclaude
@@ -1,14 +1,191 @@
 #!/usr/bin/env bash
+# safeclaude — run Claude in a locked-down container, one per project.
+#
+# Like nvm/pyenv, but for whole environments: each project keeps its setup in a
+# .safeclaude/ folder. We find it, build the container once, then reuse it.
 set -euo pipefail
 
-if [[ $# -lt 1 ]]; then
-  echo "Usage: $(basename "$0") <path-to-project> [claude-args...]" >&2
-  exit 1
-fi
-
-PROJECT_DIR="$(cd "$1" && pwd)" # resolve to absolute path
-shift
-
+SAFECLAUDE_VERSION="0.1.0"
 SCRIPT_DIR="$(cd "$(dirname "$(readlink -f "$0")")" && pwd)"
+SKELETON_DIR="$SCRIPT_DIR/skeleton"
+BASE_IMAGE="safeclaude-base:latest"
 
-PROJECT_DIR="$PROJECT_DIR" docker compose -f "$SCRIPT_DIR/docker-compose.yml" run -w /code --rm claude-code claude "$@"
+die() { echo "safeclaude: $*" >&2; exit 1; }
+
+usage() {
+  cat >&2 <<'EOF'
+safeclaude — run Claude in a locked-down container, one per project
+
+Usage:
+  safeclaude [claude-args...]   Launch Claude for the project here (args pass to claude)
+  safeclaude build              Rebuild the project's container from scratch
+  safeclaude init               Create a starter .safeclaude/ in the current directory
+  safeclaude envs               List the containers and saved data safeclaude made
+  safeclaude version            Print the safeclaude version
+  safeclaude help               Show this help
+
+Run from inside a project — the current directory, or the nearest parent that
+has a .safeclaude/ folder.
+EOF
+}
+
+# Turn a folder name into something Docker is happy to use as a name fragment:
+# lowercase, only [a-z0-9_.-], and no leading/trailing separators (Docker rejects
+# those). We capture basename into a variable first so the trailing newline is
+# gone before tr runs — otherwise tr -c turns that newline into a stray '-'.
+proj_name() {
+  local n; n="$(basename "$1")"
+  n="$(printf '%s' "$n" | tr '[:upper:]' '[:lower:]' | tr -c 'a-z0-9_.-' '-')"
+  n="$(printf '%s' "$n" | sed -e 's/^[-_.]*//' -e 's/[-_.]*$//')"
+  printf '%s' "${n:-project}"
+}
+
+# Look in this folder, then its parents, for a project (one that has a
+# .safeclaude/) — so you can launch from a subdirectory and still find it.
+find_project_root() {
+  local dir; dir="$(cd "$1" 2>/dev/null && pwd)" || return 1
+  while [ -n "$dir" ] && [ "$dir" != "/" ]; do
+    [ -f "$dir/.safeclaude/Dockerfile" ] && { echo "$dir"; return 0; }
+    dir="$(dirname "$dir")"
+  done
+  [ -f "/.safeclaude/Dockerfile" ] && { echo "/"; return 0; }
+  return 1
+}
+
+# Fingerprint the project's setup so we can tell when it changed. If the
+# fingerprint matches what we already built, we skip rebuilding. We skip .env
+# (changing a secret shouldn't force a rebuild) and cache/ (it's scratch space
+# the hooks write to constantly — hashing it would rebuild on every run).
+context_hash() {
+  local sc="$1/.safeclaude"
+  {
+    find "$sc" -type f -not -name '.env' -not -name '.env.*' -not -path "$sc/cache/*" -print0 \
+      | sort -z | xargs -0 sha256sum
+    docker image inspect --format '{{.Id}}' "$BASE_IMAGE" 2>/dev/null || true
+  } | sha256sum | cut -c1-12
+}
+
+# Build the shared base image, baking in the host user's UID/GID so the container
+# can write the bind-mounted project (see Dockerfile.base). We rebuild if the
+# image is missing, or if its baked-in IDs don't match the current host user —
+# e.g. a different user runs safeclaude, or the repo moved to another machine.
+ensure_base() {
+  local want_uid want_gid
+  want_uid="$(id -u)"; want_gid="$(id -g)"
+  if docker image inspect "$BASE_IMAGE" &>/dev/null; then
+    local have_uid have_gid
+    have_uid="$(docker image inspect --format '{{index .Config.Labels "safeclaude.uid"}}' "$BASE_IMAGE" 2>/dev/null || true)"
+    have_gid="$(docker image inspect --format '{{index .Config.Labels "safeclaude.gid"}}' "$BASE_IMAGE" 2>/dev/null || true)"
+    [ "$have_uid" = "$want_uid" ] && [ "$have_gid" = "$want_gid" ] && return 0
+    echo "[safeclaude] base image user ${have_uid:-?}:${have_gid:-?} != host $want_uid:$want_gid — rebuilding ..." >&2
+  else
+    echo "[safeclaude] building base image $BASE_IMAGE ..." >&2
+  fi
+  docker build -t "$BASE_IMAGE" \
+    --build-arg HOST_UID="$want_uid" --build-arg HOST_GID="$want_gid" \
+    -f "$SCRIPT_DIR/Dockerfile.base" "$SCRIPT_DIR" >&2
+}
+
+# Build the project's container if we haven't already (force=1 rebuilds it
+# regardless). Prints the name of the image so the caller can run it.
+ensure_project_image() {
+  local proj="$1" force="${2:-0}" image
+  image="safeclaude-$(proj_name "$proj"):$(context_hash "$proj")"
+  if [ "$force" = "1" ] || ! docker image inspect "$image" &>/dev/null; then
+    echo "[safeclaude] building $image ..." >&2
+    docker build -t "$image" "$proj/.safeclaude" >&2
+  fi
+  echo "$image"
+}
+
+cmd_run() {
+  # Always operate on the current directory's project; every argument is for claude.
+  local proj; proj="$(find_project_root ".")" \
+    || die "no .safeclaude/ found here or in any parent — run: safeclaude init"
+
+  ensure_base
+  local image; image="$(ensure_project_image "$proj")"
+
+  local home_vol="safeclaude-home-$(proj_name "$proj")"
+  local env_args=() tty_args=()
+  [ -f "$proj/.safeclaude/.env" ] && env_args=(--env-file "$proj/.safeclaude/.env")
+  [ -t 0 ] && tty_args=(-it)
+
+  # Tell the inner Claude where it is and what it can/can't do. The host path is
+  # included so it can give the developer exact instructions. Built here (not in
+  # the container) because only the launcher knows the real host path.
+  local sys_prompt
+  sys_prompt="You are running inside safeclaude, a sandboxed Docker container — not directly on the host machine.
+
+- This project is mounted at /code. On the host it lives at: ${proj}
+- You run as the non-root user 'coder'. You cannot use sudo or install system packages.
+- The .safeclaude/ directory configures this container. NEVER edit anything under .safeclaude/ yourself — instead, tell the developer exactly what to change and have them do it on the host.
+- How this environment is set up and how to change it is documented in /code/.safeclaude/README.md — read it before advising on environment changes.
+- To add a system package: ask the developer to add it to .safeclaude/Dockerfile and run 'safeclaude build' on the host.
+- To add setup that runs at container startup: ask the developer to add a script to .safeclaude/hooks/.
+- /home/coder persists between runs. Edits under /code are real and shared with the host. Everything else is discarded when the container exits."
+
+  # Run as the host user so writes to the mounted /code (and its cache/) land with
+  # the right ownership. The base image creates this exact UID/GID as 'coder', so
+  # HOME and the home volume resolve correctly. Still non-root, still locked down.
+  exec docker run --rm "${tty_args[@]}" \
+    --user "$(id -u):$(id -g)" \
+    --cap-drop ALL \
+    --security-opt no-new-privileges:true \
+    --add-host host.docker.internal:host-gateway \
+    -v "${home_vol}:/home/coder" \
+    -v "${proj}:/code" \
+    -w /code \
+    "${env_args[@]}" \
+    "$image" claude --append-system-prompt "$sys_prompt" "$@"
+}
+
+cmd_build() {
+  local proj; proj="$(find_project_root ".")" \
+    || die "no .safeclaude/ found here or in any parent — run: safeclaude init"
+  ensure_base
+  ensure_project_image "$proj" 1 >/dev/null
+  echo "[safeclaude] env ready for $(proj_name "$proj")"
+}
+
+cmd_envs() {
+  echo "Built env images:"
+  docker images --filter 'reference=safeclaude-*' \
+    --format '  {{.Repository}}:{{.Tag}}  ({{.Size}}, {{.CreatedSince}})' || true
+  echo
+  echo "Home volumes:"
+  docker volume ls --filter 'name=safeclaude-home-' --format '  {{.Name}}' || true
+}
+
+cmd_init() {
+  local sc; sc="$(pwd)/.safeclaude"
+  [ -e "$sc" ] && die ".safeclaude/ already exists at $sc"
+  [ -d "$SKELETON_DIR" ] || die "skeleton not found at $SKELETON_DIR"
+
+  # Copy the template files (see skeleton/), then add the bits that are generated
+  # rather than templated: the cache dir and the version stamp.
+  mkdir -p "$sc"
+  cp -R "$SKELETON_DIR/." "$sc/"
+  mkdir -p "$sc/cache"
+  echo "$SAFECLAUDE_VERSION" > "$sc/version"
+
+  echo "[safeclaude] created $sc"
+  echo "  - edit Dockerfile to add the packages and language versions you need"
+  echo "  - edit hooks/10-setup.sh for any startup setup"
+  echo "  - then run:        safeclaude"
+}
+
+main() {
+  local cmd="${1:-run}"
+  case "$cmd" in
+    build)        cmd_build ;;
+    init)         cmd_init ;;
+    envs|ls|list) cmd_envs ;;
+    version|-v|--version) echo "safeclaude $SAFECLAUDE_VERSION" ;;
+    help|-h|--help) usage ;;
+    run)          shift || true; cmd_run "$@" ;;  # tolerate no args (bare `safeclaude`)
+    *)            cmd_run "$@" ;;   # default: all args go to claude
+  esac
+}
+
+main "$@"
diff --git a/skeleton/.env.example b/skeleton/.env.example
new file mode 100644
index 0000000..063145d
--- /dev/null
+++ b/skeleton/.env.example
@@ -0,0 +1,4 @@
+# Put secrets here, then copy this file to .env (which stays out of git).
+# Anything in .env is handed to the container when it starts — for example, a
+# token for a private gem source:
+# BUNDLE_GEMS__GRAPHQL__PRO=user:token
diff --git a/skeleton/.gitignore b/skeleton/.gitignore
new file mode 100644
index 0000000..dd7d4ab
--- /dev/null
+++ b/skeleton/.gitignore
@@ -0,0 +1,2 @@
+.env
+cache/
diff --git a/skeleton/Dockerfile b/skeleton/Dockerfile
new file mode 100644
index 0000000..bf6acc9
--- /dev/null
+++ b/skeleton/Dockerfile
@@ -0,0 +1,16 @@
+# safeclaude builds this on top of its shared base. Everything here happens once
+# and is cached, so it won't slow down your day-to-day launches.
+FROM safeclaude-base:latest
+
+# Add the system packages and language versions your project needs below.
+# (You're root during the build, so apt just works.)
+#
+# Example — Ruby + Postgres client + headless Chrome (see the repo's example/):
+#
+# RUN apt-get update && apt-get install -y --no-install-recommends \
+#       build-essential libssl-dev libreadline-dev zlib1g-dev \
+#       libffi-dev libyaml-dev libpq-dev socat chromium chromium-driver
+#
+# Tip: pin specific language versions here (install one Ruby, one Node, etc.)
+# rather than a version manager — a project only needs one. See the repo's
+# example/ for how.
diff --git a/skeleton/README.md b/skeleton/README.md
new file mode 100644
index 0000000..0add8b9
--- /dev/null
+++ b/skeleton/README.md
@@ -0,0 +1,35 @@
+# .safeclaude/ — this project's sandboxed environment
+
+This folder defines the container that `safeclaude` runs Claude in. The container
+is built from these files, so changing the environment means editing them on the
+host and rebuilding — not installing things inside the running container (which
+is a non-root sandbox and gets reset each run).
+
+## What's here
+
+- `Dockerfile` — the container image: system packages and pinned language
+  versions (one Ruby, one Node, etc.). Built once, then cached.
+- `hooks/*.sh` — scripts that run at every startup, with the project at `/code`.
+  Use these for setup that needs your code present or should run each launch
+  (installing dependencies, starting a service proxy). Keep them safe to re-run.
+- `cache/` — scratch space on the host, gitignored. A good home for installed
+  dependencies, downloads, or "already did this" markers; survives rebuilds and
+  `docker volume` resets.
+- `.env` — secrets passed into the container at runtime (gitignored; copy from
+  `.env.example`).
+- `version` — the safeclaude version this config was created with.
+
+## How to change the environment
+
+The container runs as a non-root user with no sudo, so you can't install system
+packages from inside it. Instead, edit these files on the host:
+
+- **Add a system package:** add it to `Dockerfile`, then run `safeclaude build`.
+- **Add a language or tool:** install a specific version in `Dockerfile` — pin
+  it, since a project only needs one. See the repo's `example/` for a worked
+  Ruby + Node setup.
+- **Run setup at startup:** add or edit a script in `hooks/` (no rebuild needed).
+- **Add a secret:** put it in `.env` (see `.env.example`).
+
+After editing the `Dockerfile`, run `safeclaude build` to rebuild. Hook, `.env`,
+and `cache/` changes take effect on the next launch with no rebuild.
diff --git a/skeleton/hooks/10-setup.sh b/skeleton/hooks/10-setup.sh
new file mode 100755
index 0000000..eafd3a5
--- /dev/null
+++ b/skeleton/hooks/10-setup.sh
@@ -0,0 +1,17 @@
+#!/bin/bash
+# Runs every time the container starts, with your project at /code. Put your
+# project's startup setup here — installing dependencies, preparing services,
+# and so on. It's empty by default; add what you need.
+#
+# Keep it safe to run every launch: check whether something is already done
+# before doing it, so repeat launches stay quick.
+#
+# Need to keep things between runs? Write them to /code/.safeclaude/cache. That
+# folder lives on the host (not inside the container), so it survives rebuilds
+# and `docker volume` resets, and it's gitignored so it won't land in your repo.
+# It's a good home for installed dependencies, downloads, or "already did this"
+# markers.
+#
+# For example, you might install gems into the cache, run `npm install`, or wait
+# for a service to come up. See the repo's example/ for a worked version.
+set -euo pipefail
diff --git a/skeleton/hooks/README.md b/skeleton/hooks/README.md
new file mode 100644
index 0000000..e513e9c
--- /dev/null
+++ b/skeleton/hooks/README.md
@@ -0,0 +1,12 @@
+# Hooks
+
+Each `*.sh` file here runs when the container starts, with your project available
+at `/code`. They run in name order, so prefix them with numbers (`10-`, `20-`)
+to control the sequence.
+
+Because they run every launch, keep them quick and make them safe to re-run —
+check whether the work is already done before doing it. If one fails, startup
+stops rather than continuing half-configured.
+
+Edits take effect on the next launch (no rebuild needed). Rename a
+`*.sh.example` file to `*.sh` to turn it on.