- easy-fs gains stable inode identity (inode_id/size) and a polling head-read helper; the kernel attribute store keeps the authoritative per-file record (name, bounded key/value attributes, sanitized first-128-byte summary) plus a FNV-1a hash index from (key,value) to sorted inode lists.

- New syscalls 4020-4023: attr_set / attr_get / attr_del / file_query. Conditions are key=value text; summary=<needle> is a fuzzy summary search; file_query supports a linear-scan baseline (bit 0) and count-only (bit 1). Replies are bounded structured records; an oversized reply is EMSGSIZE, never a silent truncation.

- query_file joins the tool catalog as the fourth tool (ARG_FILE_QUERY parameter type), and its reply lands in the Agent Context slot - the structured result is already resident in the fast region.

- agent_fs_demo creates 256 attributed memory files, verifies retrieval, AND queries, fuzzy summary queries and deletion, then times the index against the full scan: 182 ms vs 404 ms over 2000 selective queries (256 files), i.e. about 2.6x faster matching cost after subtracting the syscall baseline.

- The SIGKILL signal lets the single-process demo end its yield helper, which works around the documented limitation that an only-runnable task blocks on its first block-device write. The user heap grows to 128 KiB for structured reply decoding.

- Docs: new task-4 document (protocol, index structure, measured comparison, limitations); task-2 protocol/catalog updates; README architecture, quick start, delivery table and limitations.