diff --git a/src/shared/excluded-dirs.test.ts b/src/shared/excluded-dirs.test.ts
new file mode 100644
index 000000000..21a488907
--- /dev/null
+++ b/src/shared/excluded-dirs.test.ts
@@ -0,0 +1,50 @@
+import { describe, expect, test } from "bun:test"
+import { EXCLUDED_DIRS } from "./excluded-dirs"
+import { EXCLUDED_DIRS as EXCLUDED_DIRS_FROM_BARREL } from "."
+
+describe("EXCLUDED_DIRS", () => {
+  test("contains the well-known junk directories we never want to recurse into", () => {
+    // given
+    const expected = [
+      "node_modules",
+      ".git",
+      "dist",
+      "build",
+      ".next",
+      ".sisyphus",
+      ".omx",
+      ".turbo",
+      "coverage",
+      "out",
+      ".cache",
+      ".vscode-test",
+      "target",
+      ".local-ignore",
+    ]
+
+    // when / then
+    for (const name of expected) {
+      expect(EXCLUDED_DIRS.has(name)).toBe(true)
+    }
+  })
+
+  test("does not contain commonly-wanted project directories", () => {
+    // given
+    const shouldBeAllowed = ["src", "lib", "tests", "test", "docs", ".github", ".cursor", ".claude", ".opencode"]
+
+    // when / then
+    for (const name of shouldBeAllowed) {
+      expect(EXCLUDED_DIRS.has(name)).toBe(false)
+    }
+  })
+
+  test("is frozen so consumers cannot mutate shared state", () => {
+    // given / when / then
+    expect(Object.isFrozen(EXCLUDED_DIRS)).toBe(true)
+  })
+
+  test("is re-exported from the shared barrel", () => {
+    // given / when / then
+    expect(EXCLUDED_DIRS_FROM_BARREL).toBe(EXCLUDED_DIRS)
+  })
+})
diff --git a/src/shared/excluded-dirs.ts b/src/shared/excluded-dirs.ts
new file mode 100644
index 000000000..059a01406
--- /dev/null
+++ b/src/shared/excluded-dirs.ts
@@ -0,0 +1,18 @@
+const EXCLUDED_DIR_NAMES = [
+  "node_modules",
+  ".git",
+  "dist",
+  "build",
+  ".next",
+  ".sisyphus",
+  ".omx",
+  ".turbo",
+  "coverage",
+  "out",
+  ".cache",
+  ".vscode-test",
+  "target",
+  ".local-ignore",
+] as const
+
+export const EXCLUDED_DIRS: ReadonlySet<string> = Object.freeze(new Set<string>(EXCLUDED_DIR_NAMES))
diff --git a/src/shared/index.ts b/src/shared/index.ts
index 140f88192..e99234c33 100644
--- a/src/shared/index.ts
+++ b/src/shared/index.ts
@@ -79,3 +79,4 @@ export * from "./log-legacy-plugin-startup-warning"
 export * from "./task-system-enabled"
 export * from "./parse-tools-config"
 export { parseModelString } from "./model-string-parser"
+export { EXCLUDED_DIRS } from "./excluded-dirs"