[Enrique Saurez (esaurez)]

Part of #822 (PR 6 of 11: the guest's order).

The runtime adapter's worker answered Ready once it assembled its root, then ran the host's executions at once: it had no host export to map from, took no mapping table, and nothing told it when the sandbox's workloads could start, so an execution could run on a root whose mappings were missing.

Changes

• After the assembly, the worker mounts the host export that the kernel command line names, with nvx::protocol::export::HostExport::parse and Root::mount_export, then answers Ready.
• It applies the parts of the host's mapping table in order, with Root::map, from the export, and answers each Maps with Mapped or MapFailed. A part that does not decode, or does not continue the table whose length the root configuration's mapping count announces, is refused as a whole. A mapping that the root refuses or fails to apply latches the root, and the worker refuses every later part.
• Start, which the worker confirms with Started, comes once every announced mapping is applied, and only then does the worker run executions. An execution before the start, a premature or second Start, and a part after the start end the session. A table of zero mappings does no work.
• The layout stage refuses a mapping count without an export, and export tokens that break their rules. An export that fails to mount fails the assembly. The root operations gain mount_export and map, which the tests' fake root records.

Tests

tests/guest_session.rs, with a fake root: the export and the order; a table applied in parts across a session reset, then the start; zero mappings, with and without an export; parts that do not continue the table; a mapping that the root refuses, which latches the root; and executions, Start, and parts refused out of order.

Validation

On dev at b69f40b, with #822's PRs 1-5 merged:

• Linux: the adapter's protocol-only, host-only, and guest-only (static musl) configurations (fmt, clippy, build, tests, MSRV).
• Windows: the protocol-only and host-only configurations (fmt, clippy, build, tests, MSRV).
• VM suites (vm_layered 25, vm_restart 2, vm_steps 3): WHP 30/30 and MSHV 30/30. KVM runs in CI.

[Copilot]

🟢 Approval recommended

No blocking issues were identified in the guest-side ordering, mapping failure handling, export lifecycle, or accompanying tests.

No open issues 🎉

What changed in this PR

Implements the guest-side sequencing for #822’s runtime adapter: mount the host export, apply the mapping table, and require Start before running executions.

Changes:

• Mounts and validates the host export before reporting Ready.
• Enforces mapping order and completion, blocks startup after mapping failures, and preserves progress across session resets.
• Adds session tests and documents the updated worker lifecycle.

File	Description
tests/​runtime-adapter/​tests/​guest_session.rs	Tests export mounting, mapping progress, failures, resets, and startup ordering.
tests/​runtime-adapter/​src/​worker/​order.rs	Adds mapping progress and sandbox startup state handling.
tests/​runtime-adapter/​src/​worker.rs	Integrates export mounting, mapping operations, execution gating, and export cleanup.
tests/​runtime-adapter/​src/​lib.rs	Updates the adapter overview for mappings and explicit startup.
tests/​runtime-adapter/​README.md	Documents sequencing rules, failure handling, and test coverage.

_{Review effort: Balanced}

[Copilot]

🟢 Approval recommended

The ordering and export lifecycle match the guest-side scope, with targeted regression coverage and no blocking issues identified.

No open issues 🎉

_{Review effort: Balanced}