Concepts

Operations and discovery

Declare input and output with Zod. Stable module IDs identify authority. Names become model-facing aliases. Input ordering does not choose either identity. Forage prepares the bounded discovery catalog for the captured graph.

Mule receives this runtime’s one top-level execute tool. Inner operations, including forage.search and forage.describe, stay behind that tool. The operation callback receives only its declared input and execution context. Authorization gates run before the operation. Product membership, resource ownership and final external access checks remain host responsibilities.

Changing capabilities and lifetime

Use sources when a host must acquire a current Computer, Connection or other capability projection. A source returns its bounded snapshot and an awaited release function. Its invalidate() callback marks that snapshot stale. The next lease builds a new coherent graph. An existing lease keeps its captured snapshot.

Release each lease and close the runtime. Partial acquisition unwinds already acquired sources in reverse order. Mycelium owns the scoped resources it acquires, while the host owns durable relationships, credentials and current policy. A captured snapshot does not excuse a missing final authority check.

Cancellation and errors

Execution has a deadline, a cancellation acknowledgement grace and a bounded JSON result. Cancellation aborts the invocation signal and waits for backing sandbox settlement. If the sandbox ignores it, the result reports acknowledged: false. Do not report that work as stopped.

The typed failure channel includes syntax errors, guest exceptions, lost transport, bad responses, failed capabilities, deadline/cancellation and invalid or oversized results. A foreign throw becomes Unknown. The model receives the bounded sandboxFailureMessage projection with a reference. The host receives operator evidence through onSandboxFailure and the existing reporting path. Preserve that evidence without sending host diagnostics to the guest.

An Effect host with a Promise sandbox uses fromTypedSandbox, which waits for that Promise to settle when interrupted. The concrete sandbox and broker decide how backing work is stopped. Mycelium does not implement a Worker loader, MCP server or credential vault.