diff --git a/pyproject.toml b/pyproject.toml
index 0c6dcb3..cec44e0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "govoplan-core"
-version = "0.1.37"
+version = "0.1.38"
 description = "Reusable GovOPlaN platform core, access, tenancy, and RBAC components."
 readme = "README.md"
 requires-python = ">=3.12"
diff --git a/src/govoplan_core/core/modules.py b/src/govoplan_core/core/modules.py
index 21a30c4..5583ee4 100644
--- a/src/govoplan_core/core/modules.py
+++ b/src/govoplan_core/core/modules.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from collections.abc import Callable, Iterable, Mapping, Sequence
-from dataclasses import dataclass, field
+from dataclasses import dataclass, field, replace
 from typing import Any, Literal, Protocol, TYPE_CHECKING
 
 from govoplan_core.core.information_governance import ModuleInformationGovernance
@@ -687,3 +687,53 @@ class ModuleManifest:
     # runtime module ID changes.
     permission_namespace: str | None = None
     workflow_definitions: tuple["WorkflowDefinitionContribution", ...] = ()
+
+
+def with_documentation_structured_translations(
+    manifest: ModuleManifest,
+    *,
+    locale: str,
+    translations: Mapping[str, Mapping[str, Any]],
+) -> ModuleManifest:
+    """Merge module-owned structured documentation translations by topic id.
+
+    The helper keeps feature prose in its owning module while giving every
+    manifest the same fail-closed merge behavior. Unknown topic ids and
+    incomplete or shape-changing locale maps are rejected immediately.
+    """
+
+    locale = locale.strip()
+    if not locale:
+        raise ValueError("structured documentation locale must not be empty")
+
+    topics_by_id = {topic.id: topic for topic in manifest.documentation}
+    unknown_topic_ids = sorted(set(translations) - set(topics_by_id))
+    if unknown_topic_ids:
+        raise ValueError(
+            "structured documentation translations reference unknown topic ids: "
+            + ", ".join(unknown_topic_ids)
+        )
+
+    localized_topics: list[DocumentationTopic] = []
+    for topic in manifest.documentation:
+        translation = translations.get(topic.id)
+        if translation is None:
+            localized_topics.append(topic)
+            continue
+
+        structured_translations = dict(topic.structured_translations)
+        structured_translations[locale] = translation
+        localized_topic = replace(
+            topic,
+            structured_translation_version=DOCUMENTATION_STRUCTURED_TRANSLATION_VERSION,
+            structured_translations=structured_translations,
+        )
+        issues = documentation_structured_translation_issues(localized_topic)
+        if issues:
+            raise ValueError(
+                f"invalid {locale!r} structured documentation translation for "
+                f"{topic.id!r}: {'; '.join(issues)}"
+            )
+        localized_topics.append(localized_topic)
+
+    return replace(manifest, documentation=tuple(localized_topics))
diff --git a/tests/test_documentation_topic_contract.py b/tests/test_documentation_topic_contract.py
index d7675fa..04b1219 100644
--- a/tests/test_documentation_topic_contract.py
+++ b/tests/test_documentation_topic_contract.py
@@ -12,6 +12,7 @@ from govoplan_core.core.modules import (
     ModuleManifest,
     localized_documentation_metadata,
     user_workflow_scope_condition_issues,
+    with_documentation_structured_translations,
 )
 from govoplan_core.core.registry import PlatformRegistry, RegistryError
 
@@ -136,6 +137,45 @@ class DocumentationTopicContractTests(unittest.TestCase):
         with self.assertRaisesRegex(RegistryError, "preserve list length"):
             registry_for(incomplete_shape).validate()
 
+    def test_manifest_helper_merges_and_validates_owner_translations(self) -> None:
+        topic = DocumentationTopic(
+            id="example.workflow.localized",
+            title="Run task",
+            summary="Run the task.",
+            metadata={"steps": ["Review", "Execute"]},
+        )
+        manifest = ModuleManifest(
+            id="example",
+            name="Example",
+            version="1.0.0",
+            documentation=(topic,),
+        )
+
+        localized = with_documentation_structured_translations(
+            manifest,
+            locale="de",
+            translations={
+                topic.id: {"steps": ["Prüfen", "Ausführen"]},
+            },
+        )
+
+        self.assertEqual(
+            ["Prüfen", "Ausführen"],
+            localized.documentation[0].structured_translations["de"]["steps"],
+        )
+        with self.assertRaisesRegex(ValueError, "unknown topic ids"):
+            with_documentation_structured_translations(
+                manifest,
+                locale="de",
+                translations={"missing.topic": {"steps": ["Prüfen", "Ausführen"]}},
+            )
+        with self.assertRaisesRegex(ValueError, "preserve list length"):
+            with_documentation_structured_translations(
+                manifest,
+                locale="de",
+                translations={topic.id: {"steps": ["Prüfen"]}},
+            )
+
     def test_documentation_configuration_and_source_extensions_are_validated(self) -> None:
         resolver = lambda _context, keys: {  # noqa: E731
             key: DocumentationConfigurationDecision(key=key, state="enabled")
diff --git a/webui/package-lock.json b/webui/package-lock.json
index ff4b706..1dd884f 100644
--- a/webui/package-lock.json
+++ b/webui/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@govoplan/core-webui",
-  "version": "0.1.37",
+  "version": "0.1.38",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@govoplan/core-webui",
-      "version": "0.1.37",
+      "version": "0.1.38",
       "dependencies": {
         "@govoplan/access-webui": "file:../../govoplan-access/webui",
         "@govoplan/addresses-webui": "file:../../govoplan-addresses/webui",
diff --git a/webui/package-lock.release.json b/webui/package-lock.release.json
index 09584a8..0823f77 100644
--- a/webui/package-lock.release.json
+++ b/webui/package-lock.release.json
@@ -1,12 +1,12 @@
 {
   "name": "@govoplan/core-webui",
-  "version": "0.1.37",
+  "version": "0.1.38",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@govoplan/core-webui",
-      "version": "0.1.37",
+      "version": "0.1.38",
       "dependencies": {
         "@govoplan/access-webui": "git+ssh://git@git.add-ideas.de/GovOPlaN/govoplan-access.git#v0.1.20",
         "@govoplan/admin-webui": "git+ssh://git@git.add-ideas.de/GovOPlaN/govoplan-admin.git#v0.1.19",
diff --git a/webui/package.json b/webui/package.json
index f4f7b3d..c4f5372 100644
--- a/webui/package.json
+++ b/webui/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@govoplan/core-webui",
-  "version": "0.1.37",
+  "version": "0.1.38",
   "private": true,
   "type": "module",
   "main": "src/index.ts",
diff --git a/webui/package.release.json b/webui/package.release.json
index 76772d6..ad47c9f 100644
--- a/webui/package.release.json
+++ b/webui/package.release.json
@@ -1,6 +1,6 @@
 {
   "name": "@govoplan/core-webui",
-  "version": "0.1.37",
+  "version": "0.1.38",
   "private": true,
   "type": "module",
   "main": "src/index.ts",