fix(sandbox): run containers as host user instead of root#355
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asheshgoplani merged 4 commits intoasheshgoplani:mainfrom Mar 18, 2026
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--cap-drop=ALL drops DAC_OVERRIDE, preventing root from reading bind-mounted files owned by the host user. Run as --user uid:gid so the container process owns the files naturally.
The host UID has no /etc/passwd entry inside the container, so HOME defaults to /. Explicitly set HOME to containerHome so tools find their config directories.
The container now runs as the host user instead of root. /root must be traversable (execute bit) so the non-root user can reach installed binaries at /root/.local/bin/ and /root/.opencode/bin/.
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Summary
--user <uid>:<gid>todocker createso sandbox containers run as the host user instead of rootHOME=/rootexplicitly since the host UID has no/etc/passwdentry in the containerchmod 755 /rootin the Dockerfile so the non-root user can traverse to installed binariesProblem
--cap-drop=ALLdropsDAC_OVERRIDE, which prevents root from reading files it doesn't own. Sandbox file sync (sandbox.go) creates files owned by the host user (UID 1000, mode 0600). The container runs as root (UID 0), so root can't read.credentials.json,settings.json, etc. — causing Claude to hang on startup.Fix
Run the container as the host user (
--user uid:gid) instead of root. This is cleaner than re-addingDAC_OVERRIDEbecause:--cap-drop=ALLhardening--dangerously-skip-permissionscontinues to work because Claude Code gates it viaIS_SANDBOX=1env var, not a UID check.Test plan
internal/dockerunit tests pass (3 new tests forHOMEenv var)--cap-drop=ALLclaude --versionworks inside container as non-root user