Flat Dependency Hoisting in Bower 1.8.x and Zero‑Downtime Migration

Goal: Migrate a small front‑end application to a new set of Bower packages without any downtime, relying on Bower 1.8.x’s flat dependency resolution where compatible versions are hoisted to the top level of bower_components.

Constraint: Bower does not create a lock file, so the exact flat tree produced by version ranges can differ between environments, and the default registry may be unavailable, requiring a working mirror. Additionally, hoisted packages are updated in place when the dependency tree is refreshed, which raises the question whether the atomic file‑system replacement guarantees that a running server never serves a mixture of old and new files.

Uncertainty: Whether pinning exact versions in bower.json is necessary to achieve reproducible flat trees, and whether configuring a private Bower mirror alone eliminates registry‑related failure risks during the migration.

Key questions:

• Does the in‑place, atomic update of hoisted dependencies ensure that a live server never serves a mixed version set?
• Should version ranges be replaced with exact pins to guarantee identical flat trees across development and production?
• Is a private Bower mirror sufficient to prevent installation failures caused by the deprecated public registry?