Support both Podman and Docker as container runtime

CLAUDE.md

@@ -33,7 +33,7 @@ Container config lives at `~/.config/claude-isolated/home/` (override with `CLAU
 ./tests/test-lifecycle.sh
 ```
 
-Requires Podman running. Builds image, starts a container, verifies tools (python3, uv, claude, git, zellij), checks workspace, then stops and cleans up.
+Requires Podman or Docker. Builds image, starts a container, verifies tools (python3, uv, claude, git, zellij), checks workspace, then stops and cleans up.
 
 ## Conventions
 
@@ -43,4 +43,5 @@ Requires Podman running. Builds image, starts a container, verifies tools (pytho
 - Image tag is `claude-isolated:latest`
 - No nodejs/npm — Claude Code installed via `claude.ai/install.sh`
 - No zellij — Claude runs directly in the container
+- Supports both Podman and Docker (auto-detected, prefers Podman)
 - Requires git 2.48+ in the container (for relative worktree paths); installed from Debian sid

src/claude_isolated/cli.py

@@ -1,4 +1,4 @@
-"""Run Claude Code in isolated Podman containers."""
+"""Run Claude Code in isolated containers (Podman or Docker)."""
 
 import argparse
 import contextlib
@@ -15,6 +15,17 @@
 IMAGE = "claude-isolated:latest"
 
 
+def runtime() -> str:
+    for cmd in ("podman", "docker"):
+        if shutil.which(cmd):
+            return cmd
+    print("Neither podman nor docker found in PATH", file=sys.stderr)
+    sys.exit(1)
+
+
+RUNTIME = runtime()
+
+
 def generate_name() -> str:
     if shutil.which("random-name"):
         return f"claude-isolated-{subprocess.check_output(['random-name'], text=True).strip()}"
@@ -111,7 +122,8 @@ def cmd_init(args: argparse.Namespace) -> None:
 
 def cmd_build(args: argparse.Namespace, silent: bool = False) -> None:
     kwargs = {"stdout": subprocess.DEVNULL, "stderr": subprocess.DEVNULL} if silent else {}
-    subprocess.run(["podman", "build", "-t", IMAGE, str(PROJECT_ROOT)], check=True, **kwargs)
+    containerfile = str(PROJECT_ROOT / "Containerfile")
+    subprocess.run([RUNTIME, "build", "-f", containerfile, "-t", IMAGE, str(PROJECT_ROOT)], check=True, **kwargs)
     if not silent:
         print(f"Image built: {IMAGE}")
 
@@ -146,7 +158,7 @@ def cmd_start(args: argparse.Namespace) -> None:
     # TODO: consider re-adding per-file required checks
 
     run_args = [
-        "podman", "run", "-it",
+        RUNTIME, "run", "-it",
         "--name", name,
         *[flag for src, dest, mode in volumes for flag in ("-v", f"{src}:{dest}:{mode}")],
     ]
@@ -166,19 +178,19 @@ def cmd_start(args: argparse.Namespace) -> None:
         subprocess.run(run_args)
     finally:
         # Ensure the container gets stopped and removed on exit (including on Ctrl+C or SIGHUP, which happens when closing a terminal tab for example).
-        subprocess.run(["podman", "stop", "-t", "10", name],
+        subprocess.run([RUNTIME, "stop", "-t", "10", name],
                         capture_output=True)
-        subprocess.run(["podman", "rm", name],
+        subprocess.run([RUNTIME, "rm", name],
                         capture_output=True)
 
 
 
 def cmd_stop(args: argparse.Namespace) -> None:
-    stop = subprocess.run(["podman", "stop", "-t", "2", args.name], capture_output=True)
+    stop = subprocess.run([RUNTIME, "stop", "-t", "2", args.name], capture_output=True)
     if stop.returncode != 0:
         print(f"Failed to stop container: {args.name}", file=sys.stderr)
         sys.exit(1)
-    rm = subprocess.run(["podman", "rm", args.name], capture_output=True)
+    rm = subprocess.run([RUNTIME, "rm", args.name], capture_output=True)
     if rm.returncode != 0:
         print(f"Stopped but failed to remove container: {args.name}", file=sys.stderr)
         sys.exit(1)
@@ -187,7 +199,7 @@ def cmd_stop(args: argparse.Namespace) -> None:
 
 def cmd_ls(args: argparse.Namespace) -> None:
     subprocess.run([
-        "podman", "ps",
+        RUNTIME, "ps",
         "--filter", f"ancestor={IMAGE}",
         "--format", "table {{.Names}}\t{{.Status}}\t{{.Created}}",
     ], check=True)
@@ -206,7 +218,7 @@ def main() -> None:
         cmd_start(argparse.Namespace(prompt=prompt))
         return
 
-    parser = argparse.ArgumentParser(description="Run Claude Code in isolated Podman containers")
+    parser = argparse.ArgumentParser(description="Run Claude Code in isolated containers")
     sub = parser.add_subparsers(dest="command")
 
     sub.add_parser("init", help="Create config directory from template")