diff --git a/TASKS.md b/TASKS.md
index 09f6bcb..b382a39 100644
--- a/TASKS.md
+++ b/TASKS.md
@@ -109,3 +109,13 @@ These commands were derived from the manifests at the repository root. Confirm o
   [ORCHESTRATION.md](./ORCHESTRATION.md) is met and the verification commands
   were actually run.
 - `blocked` requires a note naming what it is blocked on and who can unblock it.
+
+## Baseline findings during static-archive validation
+
+Unchanged commit `76970c9` and the archive fix both have nine failing tests
+caused by missing `PackageRecipe.to_dict`, plus one offline-index test denied
+access to the home cache by the local sandbox. Mypy also reports the missing
+method. Ruff reports four existing findings in `test_build_dir_resolution.py`,
+`test_package_recipe.py`, and `test_ci_gate.py`. These are outside the archive
+fix; the before/after full-suite results are respectively 669/672 passed,
+10 failed, and 2 skipped on macOS with Python 3.13.
diff --git a/TESTING.md b/TESTING.md
index 7039b08..767795e 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -66,3 +66,16 @@ passed, failed and skipped. A skipped test is not a passing test.
 
 Any test that could not be run in this environment is named, with the reason,
 and marked `NOT RUN` or `UNKNOWN` per [VERIFY.md](./VERIFY.md).
+
+## Static-library source removal regression
+
+Run `python -m pytest tests/ebuild/test_ninja_backend.py -v` to check native
+archive rebuilding. The source-removal test requires a host C compiler, `ar`,
+and the Ninja Python package. It builds a library, removes a source, and
+checks that the old object is absent and its function no longer links. It
+also verifies that retained code still links, unchanged archives are not
+rebuilt, and project paths containing spaces work. A separate test checks
+that an archiver failure makes Ninja fail.
+
+Static archives are recreated when their build step runs: updating an existing
+archive with `ar rcs` alone retains members removed from the source list.
diff --git a/ebuild/build/ninja_backend.py b/ebuild/build/ninja_backend.py
index de417bd..5bf2cec 100644
--- a/ebuild/build/ninja_backend.py
+++ b/ebuild/build/ninja_backend.py
@@ -9,6 +9,8 @@
 from __future__ import annotations
 
 import json
+import shlex
+import subprocess
 import sys
 from dataclasses import dataclass, field
 from pathlib import Path
@@ -187,6 +189,10 @@ def _object_path(self, target, src: str) -> Path:
     def _write_ninja(self) -> None:
         """Write the build.ninja file."""
         ninja_path = self.build_dir / "build.ninja"
+        python_command = (
+            subprocess.list2cmdline([sys.executable])
+            if sys.platform == "win32" else shlex.quote(sys.executable)
+        ).replace("$", "$$")
         lines = [
             f"# Generated by ebuild",
             f"cc = {self.toolchain.cc}",
@@ -204,7 +210,12 @@ def _write_ninja(self) -> None:
             "  description = LINK $out",
             "",
             "rule ar_rule",
-            "  command = $ar rcs $out $in",
+            # ar replaces supplied members but keeps omitted ones. Recreate
+            # the archive when Ninja rebuilds it so removed sources cannot
+            # survive as stale code. Python also works on Windows, unlike rm.
+            f'  command = {python_command} -c "from pathlib import Path; import subprocess, sys; '
+            'Path(sys.argv[1]).unlink(missing_ok=True); '
+            'sys.exit(subprocess.call(sys.argv[2:]))" $out $ar rcs $out $in',
             "  description = AR $out",
             "",
             # A shared_library edge names this rule. Without the rule the
diff --git a/tests/ebuild/test_ninja_backend.py b/tests/ebuild/test_ninja_backend.py
index d19dd8e..1d97f30 100644
--- a/tests/ebuild/test_ninja_backend.py
+++ b/tests/ebuild/test_ninja_backend.py
@@ -194,3 +194,88 @@ def run_ninja():
         "was reused and the build wrongly reported success"
     )
     assert "header was recompiled" in (second.stdout + second.stderr)
+
+
+@pytest.mark.parametrize("directory", ["project", "project with spaces"])
+def test_removing_source_removes_archive_member(tmp_path, directory):
+    """Incremental archives must contain only the current source objects."""
+    cc = shutil.which("cc") or shutil.which("gcc")
+    ar = shutil.which("ar")
+    if not cc or not ar or importlib.util.find_spec("ninja") is None:
+        pytest.skip("host C compiler, ar, and ninja are required")
+
+    source_dir = tmp_path / directory
+    source_dir.mkdir()
+    (source_dir / "keep.c").write_text("int keep(void) { return 1; }\n")
+    (source_dir / "removed.c").write_text("int removed(void) { return 42; }\n")
+    main = source_dir / "main.c"
+    main.write_text("int removed(void); int main(void) { return removed(); }\n")
+    library = TargetConfig(
+        name="helpers", target_type="static_library",
+        sources=["keep.c", "removed.c"],
+    )
+    config = ProjectConfig(
+        name="archive-regression", version="1.0", source_dir=source_dir,
+        targets=[library],
+    )
+    build_dir = source_dir / "build"
+    archive = build_dir / "libhelpers.a"
+    toolchain = SimpleNamespace(cc=cc, cxx="c++", ar=ar)
+
+    def build():
+        NinjaBackend(config, build_dir, toolchain).generate()
+        result = subprocess.run(
+            [sys.executable, "-m", "ninja", "-f", str(build_dir / "build.ninja")],
+            cwd=source_dir, capture_output=True, text=True,
+        )
+        assert result.returncode == 0, result.stdout + result.stderr
+
+    def link():
+        return subprocess.run(
+            [cc, str(main), str(archive), "-o", str(build_dir / "app")],
+            capture_output=True, text=True,
+        )
+
+    build()
+    assert link().returncode == 0
+    initial_mtime = archive.stat().st_mtime_ns
+    build()
+    assert archive.stat().st_mtime_ns == initial_mtime, "unchanged archive rebuilt"
+
+    library.sources.remove("removed.c")
+    (source_dir / "removed.c").unlink()
+    build()
+    members = subprocess.check_output([ar, "t", str(archive)], text=True)
+    assert "removed.o" not in members.splitlines(), members
+    assert "keep.o" in members.splitlines(), members
+    assert link().returncode != 0, "deleted function still links from stale code"
+
+    # The retained function still links, so this is not merely a broken archive.
+    main.write_text("int keep(void); int main(void) { return keep() - 1; }\n")
+    result = link()
+    assert result.returncode == 0, result.stdout + result.stderr
+
+
+def test_archive_failure_is_reported_by_ninja(tmp_path):
+    """The Python wrapper must preserve the archiver's failure status."""
+    cc = shutil.which("cc") or shutil.which("gcc")
+    if not cc or importlib.util.find_spec("ninja") is None:
+        pytest.skip("host C compiler and ninja are required")
+    (tmp_path / "lib.c").write_text("int value(void) { return 1; }\n")
+    config = ProjectConfig(
+        name="archive-failure", version="1.0", source_dir=tmp_path,
+        targets=[TargetConfig(
+            name="helpers", target_type="static_library", sources=["lib.c"],
+        )],
+    )
+    # Python receives 'rcs' as a script name and fails: a portable stand-in
+    # for an archiver returning a nonzero status, without a shell script.
+    toolchain = SimpleNamespace(cc=cc, cxx="c++", ar=sys.executable)
+    build_dir = tmp_path / "build"
+    NinjaBackend(config, build_dir, toolchain).generate()
+    result = subprocess.run(
+        [sys.executable, "-m", "ninja", "-f", str(build_dir / "build.ninja")],
+        cwd=tmp_path, capture_output=True, text=True,
+    )
+    assert result.returncode != 0, result.stdout + result.stderr
+    assert "rcs" in result.stdout + result.stderr