[Enhancement]: Strands adapter: offer the Strands CLI's interactive mode #559

Affected area

Harness adapter; Schemas or configuration; Consumer integration; Documentation or examples

Problem or opportunity

Part of #547, which proposes one contract for serving harnesses' native interfaces.

The adapter launches strands --acp-server (CLI 0.2.1) through the shared ACP runner. Fabric exposes none of the harness's own interfaces, so a consumer such as NVIDIA NemoClaw can't offer them.

Native interfaces:

• Observed in @strands-agents/cli 0.2.1: the interactive CLI (default), -p/--print and --acp-server.

Proposed enhancement

Implement on #547's shared contract: opt-in harness.settings.interfaces.<name>, discovery of loopback ports and credential locations through the handle, owner-only credentials, the service lifecycle where an interface outlives a runtime, health checks, outbound requests off by default, and documented packaging.

• Add a terminal interface that opens the Strands interactive CLI with the runtime's configuration, and, if Strands allows, on the runtime's session.

Verify first:

• Whether the interactive CLI can load a session created through ACP.

Estimated effort: Medium.

Public contract and compatibility impact

• Schemas or adapter contract: the adapter's descriptor declares its interfaces, and its settings gain interfaces.
• Backward compatibility: additive; interfaces default to off.

Alternatives considered

• Consumer-side launching. A consumer could start the harness's interface beside Fabric, but it would duplicate configuration, credential and lifecycle handling outside Fabric, which [Enhancement]: Epic: serve harnesses' native interfaces through one adapter contract #547 avoids.

Acceptance criteria

• The interactive CLI opens with the runtime's configuration, and its conversation behavior matches the README.
• The interface is off by default, listens only on loopback, and uses [Enhancement]: Epic: serve harnesses' native interfaces through one adapter contract #547's discovery and credential handling.
• The README documents the interface, its packaging, and whether it shares conversations with Fabric invocations.

Additional context

Survey of Fabric main at 4fdf65a (2026-10-29); CLI options come from each CLI's --help in a disposable container. NemoClaw builds no Strands image yet.

Duplicate check

• I searched the existing issues and did not find a duplicate.