agent-block-core — host runtime + Lua stdlib bridge + EventBus.

Depends on agent-block-types (error / obs) and agent-block-mcp (rmcp wrapper). The bin crate agent-block is a thin CLI on top.

Cargo features

All three are on by default, so the default build (and the agent-block CLI) keeps the full runtime surface. SDK embedders that only need a subset can opt out with default-features = false and re-enable individual axes:

The stdio MCP transport (mcp.connect), http.*, tool.*, sh.*, log.*, bus.*, and the embedded StdPkg blocks are always available.

When a feature is off:

• mesh: the mesh.* bridge is not registered; BlockConfig::relay_url / secret_key are accepted but ignored.
• sqlite: the sql.* / kv.* / ts.* bridges are not registered; BlockConfig::sql_path / kv_path / ts_path are accepted but ignored (fields retained for API stability). It does not gate SQLite itself: the kernel ([knl]) keeps every session's event log in a SQLite table — the log is read with SQL — so rusqlite and rusqlite-isle are ordinary dependencies and a session is a session in every build. They are the same versions mlua-batteries-sqlite builds on (rusqlite 0.37 / libsqlite3-sys 0.35), which is not a coincidence: libsqlite3-sys declares links = "sqlite3", so a build graph may hold exactly one of it, whichever way the feature is set.
• mcp-http: mcp.connect_http returns an explicit error when called.

Sandbox

[sandbox] installs an optional process-wide execution boundary (Landlock + seccomp, Linux only): filesystem writes are confined to an allowlist and io_uring is denied, while reads and executes stay open. It is inherited by sh.exec / mcp.connect children, and must be applied before any async runtime spawns worker threads — see the module docs.