Grok Build v1.0.39 is out with a few practical updates. Standouts include subagents can always use the parent model, with that choice locked in when. Earlier image attachments now survive multiple compactions via a persisted path list. Also worth noting: subagent spawning no longer requires choosing a type. Release Notes: v1.0.39 - 2026-09-20 Features - Subagents can always use the parent model, with that choice locked in when the session starts. - Earlier image attachments now survive multiple compactions via a persisted path list. - Subagent spawning no longer requires choosing a type; omitted calls default to general-purpose. - The agent now keeps helper scripts, logs, and PR drafts in the system temp directory instead of the repository. - read_file descriptions now tell the model when offset/limit are ignored for SKILL.md and instruction files. - Effort levels for models now come from the API instead of hard-coded lists, and config aliases inherit the menu. - MCP tools that receive the wrong JSON shape are now automatically fixed when the mismatch is unambiguous. Bug Fixes - Local worktree capture no longer refuses repositories that contain uninitialized submodules. - Memory captures no longer include opaque model reasoning blobs. - Idle timeouts now show a clear message instead of raw internal text. - Images attached to the last user prompt now survive compaction. - Custom agent profiles now persist correctly across session resume and reload. - Subagent labels now appear as "Subagent" instead of "General" in transcripts and the tasks pane. Listen to the video below for more details.