diff --git a/tools/bump_pyproject_deps.py b/tools/bump_pyproject_deps.py
index 7028b464..c94b5201 100644
--- a/tools/bump_pyproject_deps.py
+++ b/tools/bump_pyproject_deps.py
@@ -21,6 +21,19 @@
     ROOT / 'libs' / 'extractor-api-lib' / 'pyproject.toml',
 ]
 
+# Internal library dependency pins to keep in sync with lib versions
+LIB_DEP_PINS = {
+    ROOT / 'libs' / 'rag-core-api' / 'pyproject.toml': {
+        'tool.poetry.dependencies.rag-core-lib': '=={v}',
+    },
+    ROOT / 'libs' / 'admin-api-lib' / 'pyproject.toml': {
+        'tool.poetry.dependencies.rag-core-lib': '=={v}',
+    },
+    ROOT / 'libs' / 'extractor-api-lib' / 'pyproject.toml': {
+        'tool.poetry.dependencies.rag-core-lib': '=={v}',
+    },
+}
+
 # Service pins to update after libs are published
 SERVICE_PINS = {
     ROOT / 'services' / 'rag-backend' / 'pyproject.toml': {
@@ -86,6 +99,27 @@ def bump(version: str, bump_libs: bool = True, bump_service_pins: bool = True) -
             file.write_text(new_txt)
             print(f"Updated {file} -> tool.poetry.version = {version}")
 
+        # Keep internal lib dependency pins aligned with the bumped version.
+        for file, mapping in LIB_DEP_PINS.items():
+            txt = file.read_text()
+            doc = tomlkit.parse(txt)
+            deps = _get_table(doc, [
+                'tool', 'poetry', 'dependencies'
+            ])
+            if deps is None or not hasattr(deps, '__contains__'):
+                print(f"Skip {file}: dependencies table not found")
+                file.write_text(tomlkit.dumps(doc))
+                continue
+            for dotted, template in mapping.items():
+                pkg = dotted.split('.')[-1]
+                if pkg in deps:
+                    val = template.format(v=version)
+                    deps[pkg] = val
+                    print(f"Pinned {file} -> {pkg} = {val}")
+                else:
+                    print(f"Skip {file}: {pkg} not present in dependencies")
+            file.write_text(tomlkit.dumps(doc))
+
     # 2) bump service pins only inside [tool.poetry.group.prod.dependencies]
     if bump_service_pins:
         for file, mapping in SERVICE_PINS.items():
diff --git a/tools/tests/test_bump_pyproject_deps.py b/tools/tests/test_bump_pyproject_deps.py
index 20d9fd08..f69ad6af 100644
--- a/tools/tests/test_bump_pyproject_deps.py
+++ b/tools/tests/test_bump_pyproject_deps.py
@@ -1,5 +1,10 @@
 """Tests for tools/bump_pyproject_deps.py."""
 
+from pathlib import Path
+
+import tomlkit
+
+from tools import bump_pyproject_deps
 from tools.bump_pyproject_deps import replace_version_line
 
 
@@ -32,3 +37,60 @@ def test_replace_version_line_inserts_version_without_duplicate_section() -> Non
 
     assert "version = \"2.0.0\"" in out
     assert out.count("[tool.poetry]") == 1
+
+
+def _write_pyproject(path: Path, name: str, version: str, with_rag_core_dep: bool) -> None:
+    lines = [
+        "[tool.poetry]",
+        f"name = \"{name}\"",
+        f"version = \"{version}\"",
+        "",
+        "[tool.poetry.dependencies]",
+        "python = \"^3.13\"",
+    ]
+    if with_rag_core_dep:
+        lines.append("rag-core-lib = \"==4.0.0\"")
+    path.write_text("\n".join(lines) + "\n")
+
+
+def test_bump_updates_internal_lib_dependency_pins(tmp_path: Path, monkeypatch) -> None:
+    rag_core_lib = tmp_path / "rag-core-lib.toml"
+    rag_core_api = tmp_path / "rag-core-api.toml"
+    admin_api_lib = tmp_path / "admin-api-lib.toml"
+    extractor_api_lib = tmp_path / "extractor-api-lib.toml"
+
+    _write_pyproject(rag_core_lib, "rag-core-lib", "4.0.0", with_rag_core_dep=False)
+    _write_pyproject(rag_core_api, "rag-core-api", "4.0.0", with_rag_core_dep=True)
+    _write_pyproject(admin_api_lib, "admin-api-lib", "4.0.0", with_rag_core_dep=True)
+    _write_pyproject(extractor_api_lib, "extractor-api-lib", "4.0.0", with_rag_core_dep=True)
+
+    monkeypatch.setattr(
+        bump_pyproject_deps,
+        "LIBS_VERSION_FILES",
+        [rag_core_lib, rag_core_api, admin_api_lib, extractor_api_lib],
+    )
+    monkeypatch.setattr(
+        bump_pyproject_deps,
+        "LIB_DEP_PINS",
+        {
+            rag_core_api: {"tool.poetry.dependencies.rag-core-lib": "=={v}"},
+            admin_api_lib: {"tool.poetry.dependencies.rag-core-lib": "=={v}"},
+            extractor_api_lib: {"tool.poetry.dependencies.rag-core-lib": "=={v}"},
+        },
+    )
+
+    bump_pyproject_deps.bump("4.1.0", bump_libs=True, bump_service_pins=False)
+
+    rag_core_doc = tomlkit.parse(rag_core_lib.read_text())
+    rag_core_api_doc = tomlkit.parse(rag_core_api.read_text())
+    admin_api_doc = tomlkit.parse(admin_api_lib.read_text())
+    extractor_api_doc = tomlkit.parse(extractor_api_lib.read_text())
+
+    assert rag_core_doc["tool"]["poetry"]["version"] == "4.1.0"
+    assert rag_core_api_doc["tool"]["poetry"]["version"] == "4.1.0"
+    assert admin_api_doc["tool"]["poetry"]["version"] == "4.1.0"
+    assert extractor_api_doc["tool"]["poetry"]["version"] == "4.1.0"
+
+    assert rag_core_api_doc["tool"]["poetry"]["dependencies"]["rag-core-lib"] == "==4.1.0"
+    assert admin_api_doc["tool"]["poetry"]["dependencies"]["rag-core-lib"] == "==4.1.0"
+    assert extractor_api_doc["tool"]["poetry"]["dependencies"]["rag-core-lib"] == "==4.1.0"