diff --git a/scripts/ci/build_input_fingerprint.py b/scripts/ci/build_input_fingerprint.py
deleted file mode 100755
index 010a0746a5c7..000000000000
--- a/scripts/ci/build_input_fingerprint.py
+++ /dev/null
@@ -1,60 +0,0 @@
-#!/usr/bin/env python3
-"""Hash everything compile admission can read, so equal hashes mean an equal build.
-
-The hash covers the git tree entries (mode, object id, path) of every tracked
-path except those known not to reach the Xcode build, plus any extra strings the
-caller pins (the selected Xcode). Two commits with the same fingerprint compile
-the same sources with the same toolchain, whatever else differs between them.
-"""
-
-from __future__ import annotations
-
-import argparse
-import hashlib
-import subprocess
-import sys
-from pathlib import Path
-
-sys.path.insert(0, str(Path(__file__).resolve().parent))
-
-from detect_ci_change_areas import is_macos_change  # noqa: E402
-
-CI_WORKFLOW = ".github/workflows/ci.yml"
-
-
-def reaches_the_build(path: str) -> bool:
-    """False only for paths the router already calls macOS-neutral, and for CI
-    plumbing the Xcode build never opens: guard tests, other workflows, Markdown."""
-    if path == CI_WORKFLOW:
-        return True
-    if path.startswith((".github/", "tests/", "tests_v2/")) or path.endswith(".md"):
-        return False
-    return is_macos_change(path)
-
-
-def fingerprint(tree_lines: list[str], extra: list[str]) -> str:
-    digest = hashlib.sha256()
-    for line in sorted(tree_lines):
-        # "<mode> <type> <object>\t<path>"
-        path = line.split("\t", 1)[1]
-        if reaches_the_build(path):
-            digest.update(line.encode("utf-8") + b"\n")
-    for value in extra:
-        digest.update(b"extra:" + value.encode("utf-8") + b"\n")
-    return digest.hexdigest()
-
-
-def main(argv: list[str]) -> int:
-    parser = argparse.ArgumentParser(description=__doc__.splitlines()[0])
-    parser.add_argument("--revision", default="HEAD")
-    parser.add_argument("--extra", action="append", default=[])
-    args = parser.parse_args(argv)
-    lines = subprocess.check_output(
-        ["git", "-c", "core.quotepath=off", "ls-tree", "-r", args.revision], text=True
-    ).splitlines()
-    print(fingerprint(lines, args.extra))
-    return 0
-
-
-if __name__ == "__main__":
-    sys.exit(main(sys.argv[1:]))
diff --git a/tests/test_ci_change_areas.py b/tests/test_ci_change_areas.py
index b0c724df3f5c..d56ed3fd39ad 100644
--- a/tests/test_ci_change_areas.py
+++ b/tests/test_ci_change_areas.py
@@ -1360,25 +1360,6 @@ def gate(**kwargs) -> int:
     ).returncode == 1
 
 
-def test_build_input_fingerprint_ignores_only_what_the_build_cannot_read() -> None:
-    sys.path.insert(0, str(ROOT / "scripts/ci"))
-    from build_input_fingerprint import fingerprint, reaches_the_build
-
-    def tree(**files: str) -> list[str]:
-        return [f"100644 blob {object_id}\t{path}" for path, object_id in files.items()]
-
-    base = tree(**{"Sources/App.swift": "a1", "tests/test_x.py": "b1", "docs/x.md": "c1", ".github/workflows/nightly.yml": "d1"})
-    same_build = tree(**{"Sources/App.swift": "a1", "tests/test_x.py": "b2", "docs/x.md": "c2", ".github/workflows/nightly.yml": "d2", "web/app/page.tsx": "e1"})
-    assert fingerprint(base, ["xcode=1"]) == fingerprint(same_build, ["xcode=1"])
-    assert fingerprint(base, ["xcode=1"]) != fingerprint(base, ["xcode=2"])
-    for path in ("Sources/App.swift", "Packages/macOS/CmuxCore/Package.swift", "cmuxTests/T.swift", "cmux.xcodeproj/project.pbxproj",
-                 "scripts/build-ghostty-cli-helper.sh", "ghostty", ".github/workflows/ci.yml", ".xcode-version", "unknown/new-dir/file"):
-        assert reaches_the_build(path), path
-        assert fingerprint(base, []) != fingerprint(base + tree(**{path: "z9"}), []), path
-    for path in ("tests/test_ci_change_areas.py", ".github/workflows/nightly.yml", "docs/a.md", "web/app/page.tsx", "README.md", "CLAUDE.md"):
-        assert not reaches_the_build(path), path
-
-
 def admission_api(runs: list[dict], artifacts: dict[int, list[str]], jobs: dict[int, list[dict]], branch: str = "feature"):
     """Fake GitHub API: `artifacts` lists the artifact names each run holds."""
     from urllib.parse import parse_qs, urlsplit