v0.18.19.

Fixed

• Prepare fixed-host-port Docker candidates before stopping the serving runtime. A creation failure leaves the previous application serving; a successful preparation hands off ports immediately before candidate start.
• Preserve the serving runtime when cancellation arrives during candidate preparation. Cleanup removes only the interrupted candidate.
• Apply the guarded handoff to multiline environment deployments through Compose create/start, preserving decoded environment values and named volumes.

Deployment behavior

• Application startup with direct host ports remains sequential. This patch does not enable persistent TCP/UDP ingress or remove the startup interruption of all-in-one stateful applications.

Verification

• The actual builder, Docker and Traefik acceptance preserved 131 successful HTTP responses across injected creation-acknowledgement failures in plain and multiline environment cases. The stopped candidate, serving old runtime, prepared successful start and persistent-volume marker were checked.
• 200 local tests across seven covering suites passed, including four assertion-based before/after regressions. Full hosted CI and primary-network readiness passed before release preparation.