diff --git a/.agents/rules/starlark.md b/.agents/rules/starlark.md
index b7dd65961a..f0f798074f 100644
--- a/.agents/rules/starlark.md
+++ b/.agents/rules/starlark.md
@@ -69,6 +69,8 @@ globs: "*.bzl,BUILD,BUILD.bazel,*.bazel"
   `@bazel_skylib//lib:types.bzl` instead of `type(x)` comparisons.
 * **Non-Info Provider Naming**: Add `# buildifier: disable=name-conventions`
   above `provider()` declarations that do not end in `Info` (e.g. `*Fileset`).
+* **`config_setting` Naming**: Prefix `config_setting` names with `is_` (e.g.
+  `is_linux_x86_64`), so that `select()` keys read as conditions.
 * **Docstring Formatting Invariants**: Use triple-quoted strings for multi-line
   docstrings without trailing backslashes (`\`) for line continuation.
 * **No Bazel Copyright Headers**: Do not add Bazel copyright headers to new or
diff --git a/.agents/skills/review-code/review-starlark-prompt.md b/.agents/skills/review-code/review-starlark-prompt.md
index 3d99f226c7..95113440f5 100644
--- a/.agents/skills/review-code/review-starlark-prompt.md
+++ b/.agents/skills/review-code/review-starlark-prompt.md
@@ -16,5 +16,6 @@ in `git diff` against the project's Starlark coding rules and conventions:
    `python/private/common_labels.bzl` rather than redefining `Label("//...")`.
 8. Prefer `types.is_*` helpers from `@bazel_skylib//lib:types.bzl` over
    `type(x)` comparisons.
+9. Verify `config_setting` names start with `is_` (or `_is_` when private).
 
 @.agents/skills/review-code/review-report-format.md