The History tool: past chats become a primitive (v1.20.0)

RFC BE ships the History tool in v1.20.0, providing ten operations for accessing past chats including list, get, search, rename, annotate, pin, archive, recap, resume, and related. The tool introduces session-level metadata such as title, description, tags, and summaries, with scoped access controlled by history_scope and server-side identity resolution. It supersedes the Context op=history and includes five post-merge review fixes.

RFC BE ships the History tool: a built-in surface with ten ops for reaching past chats — list chats in a scope, pinned-first, paginated, per-chat token/cost/run-count aggregates , get metadata + full transcript, format:markdown renders it , search case-insensitive title match; body-search FTS deferred , rename / annotate / pin / archive, recap idempotent LLM summary stored on the session row, live-and-parked-chat-safe , resume returns a continuation handle for a new run against the chat's session id , related semantic similar-chats via the configured embedder, cosine ranking in Go, no pgvector . Owner scopes self / user / tenant / global, gated per agent by history scope, resolved server-side from RunIdentity ctx and never the wire. Cross-scope by-id reads fold to an opaque not-found so session IDs are never an existence oracle. Global is stripped for non-admin principals at policy resolution and fails closed. A "chat" is a session session → runs → events ; History adds the human and organizational layer on top: title, description, tags, pinned, archived at, summary, summary updated at migration 0057 . Related's index is session embeddings migration 0058 , filled lazily on recap / rename / annotate. Transcripts are persisted already-redacted RFC Z so a History reader can never see a secret. Transports: HTTP POST /v1/ history, gRPC History RPC, MCP history meta-tool, @loomcycle/client + Python at 1.20.0. Supersedes and removes Context op=history. Also folds in five post-merge review fixes 723 including the strict identity-required rule for self and user scope.