Uncertain De‑precation Timeline for Legacy .eslintrc in ESLint 9

Goal

Determine a clear migration path for projects still using legacy .eslintrc files when upgrading to ESLint 9, given the documented shift to the flat‑config system and the ongoing ambiguity about when legacy support will be removed.

Constraints & Uncertainty

The flat‑config model replaces the directory‑based cascade of legacy .eslintrc files with an ordered array of configuration objects, changing how rule overrides and ignore patterns are processed. While ESLint 9 continues to support legacy files, the community has not yet defined a concrete de‑precation schedule, leaving teams unsure whether to invest in a gradual transition or a quick rewrite.

Specific Questions

• When will ESLint officially drop support for legacy .eslintrc files, and what version will serve as the de‑precation cutoff?
• How will rule overrides that rely on the legacy cascading behavior be preserved or mapped when converting to a flat‑config array?
• What is the recommended strategy for handling ignore patterns that were implicitly handled by legacy .eslintignore and node_modules defaults in the new flat‑config environment?