{"slug": "warm-containers-cloneable-agents-resident-sub-agents-v1-23-2-to-v1-28-0", "title": "Warm containers, cloneable agents, resident sub-agents (v1.23.2 to v1.28.0)", "summary": "Loom SDK releases v1.23.2 through v1.28.0 deliver three major feature arcs: RFC BI P2 hardens sandbox isolation with durable per-principal workspaces, attested run tagging, and static-MCP re-probe; RFC BJ personalizes chat agents with Library Clone, self-service SkillDef, and cross-provider replay; RFC BK ships resident sub-agents with warm containers, bounded execution, and Web UI visibility, composing into a compile-test-fix loop.", "body_md": "Three interlocking arcs across seven releases. RFC BI P2 hardens the sandbox: durable per-principal workspaces via sandbox_open workspace: (bind-mounted /work, fenced as //, build caches survive container reap and sidecar restart), attested run tagging via the X-Loom-Root-Run header loomcycle forwards (server-set, unforgeable), sandbox_touch keepalive + sandbox_close_run bulk close, plus a static-MCP re-probe at run start so a sidecar that comes up second recovers on the next run. RFC BJ personalizes chat agents: a Library Clone action derives a new agent whose tool list is editable and may widen (only over the operator bearer, never from an in-run LLM), chat agents get self-service SkillDef, the fork ceiling check is now glob-aware, and POST /v1/sessions/{id}/replay copies a transcript into a new session bound to a possibly different target agent (cross-provider safe, reasoning stripped, optional compress). Adapters bump to 1.25.0 for replaySession. RFC BK ships resident sub-agents: Agent open/send/close keeps a child alive across turns with a warm sandbox container and full conversation state, then bounded and interruptible via timeout_ms + poll + cancel, then Web UI visibility with per-run listing + close + turn-cancel. Composes into a real compile-test-fix loop.", "url": "https://wpnews.pro/news/warm-containers-cloneable-agents-resident-sub-agents-v1-23-2-to-v1-28-0", "canonical_source": "https://loomcycle.dev/blog/warm-containers-cloneable-agents-resident-sub-agents.html", "published_at": "2026-07-21 05:35:16.073894+00:00", "updated_at": "2026-07-21 05:35:18.403507+00:00", "lang": "en", "topics": ["ai-agents", "developer-tools", "ai-infrastructure"], "entities": ["Loom SDK", "RFC BI P2", "RFC BJ", "RFC BK", "Library Clone", "SkillDef", "Web UI"], "alternates": {"html": "https://wpnews.pro/news/warm-containers-cloneable-agents-resident-sub-agents-v1-23-2-to-v1-28-0", "markdown": "https://wpnews.pro/news/warm-containers-cloneable-agents-resident-sub-agents-v1-23-2-to-v1-28-0.md", "text": "https://wpnews.pro/news/warm-containers-cloneable-agents-resident-sub-agents-v1-23-2-to-v1-28-0.txt", "jsonld": "https://wpnews.pro/news/warm-containers-cloneable-agents-resident-sub-agents-v1-23-2-to-v1-28-0.jsonld"}}