diff --git a/scripts/build_docs.py b/scripts/build_docs.py
index 27776d75..2aa99f4f 100755
--- a/scripts/build_docs.py
+++ b/scripts/build_docs.py
@@ -29,7 +29,7 @@
 from pathlib import Path
 
 from strip_availability import strip_archive
-from curate_navigator import curate_navigator, validate_navigation, NavigationError
+from curate_navigator import curate_navigator, set_version_paragraph, validate_navigation, NavigationError
 
 
 class ArchiveFetchError(Exception):
@@ -140,6 +140,16 @@ def validate_sources(config):
 
     if "version" not in config:
         errors.append("Top-level 'version' field is missing")
+    elif not isinstance(config["version"], dict):
+        errors.append(
+            "Top-level 'version' field must be an object with 'slug' and "
+            "'descriptive-name'"
+        )
+    else:
+        if not config["version"].get("slug"):
+            errors.append("Top-level 'version' object is missing 'slug'")
+        if not config["version"].get("descriptive-name"):
+            errors.append("Top-level 'version' object is missing 'descriptive-name'")
 
     if "sources" not in config:
         errors.append("Top-level 'sources' field is missing")
@@ -758,7 +768,7 @@ def inject_custom_templates_into_stubs(archive_path, common_dir):
     return patched
 
 
-def _finalize_combined_archive(all_archives, output_dir, version, docc_cmd, prior_failed, common_dir=None, navigation=None, hosting_base_path=None):
+def _finalize_combined_archive(all_archives, output_dir, version_slug, docc_cmd, prior_failed, common_dir=None, navigation=None, hosting_base_path=None, version=None):
     """Merge per-source archives and apply the static-hosting transform.
 
     Returns (succeeded_steps, failed_steps): names that should be added to
@@ -790,16 +800,20 @@ def _finalize_combined_archive(all_archives, output_dir, version, docc_cmd, prio
             print(f"  - {ma}")
         return [], ["combined-merge"]
 
-    combined_output = output_dir / f"{version}"
+    combined_output = output_dir / f"{version_slug}"
     try:
         merge_archives(
             all_archives, combined_output, docc_cmd,
-            landing_page_name=f"Swift - {version}",
+            landing_page_name="Swift Documentation",
         )
     except subprocess.CalledProcessError:
         print("Error: docc merge failed")
         return [], ["combined-merge"]
 
+    descriptive_name = (version or {}).get("descriptive-name")
+    if descriptive_name:
+        set_version_paragraph(combined_output, f"Swift version: {descriptive_name}")
+
     if navigation is not None:
         try:
             curate_navigator(combined_output, navigation)
@@ -809,7 +823,7 @@ def _finalize_combined_archive(all_archives, output_dir, version, docc_cmd, prio
             return ["combined-merge"], ["navigator-curation"]
 
     try:
-        transform_static_hosting(combined_output, hosting_base_path or version, docc_cmd)
+        transform_static_hosting(combined_output, hosting_base_path or version_slug, docc_cmd)
     except subprocess.CalledProcessError:
         print("Error: docc process-archive transform-for-static-hosting failed")
         curated = ["combined-merge"]
@@ -926,7 +940,8 @@ def main():
         print("No navigation.json found — combined navigator will not be curated.")
 
     version = config["version"]
-    hosting_base_path = f"{args.extra_hosting_prefix}/{version}" if args.extra_hosting_prefix else version
+    version_slug = version["slug"]
+    hosting_base_path = f"{args.extra_hosting_prefix}/{version_slug}" if args.extra_hosting_prefix else version_slug
     sources = config["sources"]
 
     # Ensure consistent, pretty-printed DocC JSON output
@@ -1006,9 +1021,9 @@ def attempt_build(index, source, fatal=(), recoverable=()):
     # Merge all archives — only when building everything (not --only)
     if all_archives and not args.only:
         s_steps, f_steps = _finalize_combined_archive(
-            all_archives, output_dir, version, tools.docc, failed,
+            all_archives, output_dir, version_slug, tools.docc, failed,
             common_dir=common_dir, navigation=navigation,
-            hosting_base_path=hosting_base_path,
+            hosting_base_path=hosting_base_path, version=version,
         )
         succeeded.extend(s_steps)
         failed.extend(f_steps)
diff --git a/scripts/curate_navigator.py b/scripts/curate_navigator.py
index a773075a..071cf8e2 100644
--- a/scripts/curate_navigator.py
+++ b/scripts/curate_navigator.py
@@ -295,6 +295,31 @@ def _section_anchor(title):
     return "-".join(title.split())
 
 
+def set_version_paragraph(archive_path, text):
+    """Set the synthesized landing page's body to a single paragraph of text.
+
+    Overwrites any existing `primaryContentSections` in data/documentation.json — the
+    freshly-merged landing page ships with none (DocC omits empty content sections), so
+    replacing the array wholesale keeps repeated builds idempotent. No-op when
+    data/documentation.json is absent. See hacking-synthesized-landing-page.md.
+    """
+    page = Path(archive_path) / "data" / "documentation.json"
+    if not page.is_file():
+        return
+    doc = json.loads(page.read_text())
+    doc["primaryContentSections"] = [{
+        "kind": "content",
+        "content": [{
+            "type": "paragraph",
+            "inlineContent": [{"type": "text", "text": text}],
+        }],
+    }]
+
+    tmp = page.with_suffix(".json.tmp")
+    tmp.write_text(json.dumps(doc, indent=2, ensure_ascii=False) + "\n")
+    os.replace(tmp, page)
+
+
 def dry_run(archive_path, navigation):
     """Compute the curated navigator WITHOUT modifying the archive.
 
diff --git a/scripts/hacking-index-json.md b/scripts/hacking-index-json.md
index 2b10b196..4b2fc186 100644
--- a/scripts/hacking-index-json.md
+++ b/scripts/hacking-index-json.md
@@ -40,10 +40,11 @@ but be aware they will be stale if something else reads them.
 **All curation happens inside `.interfaceLanguages.swift[0].children[]`.**
 
 `swift[0]` is the synthesized root node — `{ "type": "module", "title":
-"Swift - main", "path": "/documentation", "children": [...] }` (the
-`--synthesized-landing-page-name`). Its **`children`** array holds **one
-`module` node per merged module**, in merge order. That array is the curation
-surface. (In the `main` build it has **36 entries** — see below.)
+"Swift Documentation", "path": "/documentation", "children": [...] }` (the
+`--synthesized-landing-page-name`, a fixed string independent of the build's
+`version`). Its **`children`** array holds **one `module` node per merged
+module**, in merge order. That array is the curation surface. (In the `main`
+build it has **36 entries** — see below.)
 
 ## The `Node` object
 
diff --git a/scripts/hacking-synthesized-landing-page.md b/scripts/hacking-synthesized-landing-page.md
new file mode 100644
index 00000000..0be73511
--- /dev/null
+++ b/scripts/hacking-synthesized-landing-page.md
@@ -0,0 +1,176 @@
+# Hacking the Synthesized Landing Page Body — DocC Merge Post-Processing
+
+Companion to `hacking-index-json.md` (sidebar/navigator). This file covers the
+**page body** of the combined archive's synthesized landing page
+(`/documentation/`), rendered from `data/documentation.json`, and specifically
+how to inject prose (e.g. a "Swift version: X" paragraph) into it.
+
+Verified against the
+[`swiftlang/swift-docc`](https://github.com/swiftlang/swift-docc) source
+(specifically
+[`MergeAction+SynthesizedLandingPage.swift`](https://github.com/swiftlang/swift-docc/blob/main/Sources/DocCCommandLine/Action/Actions/Merge/MergeAction%2BSynthesizedLandingPage.swift)
+and
+[`Sources/SwiftDocC/Model/Rendering/`](https://github.com/swiftlang/swift-docc/tree/main/Sources/SwiftDocC/Model/Rendering)),
+not just observed output — the mechanics below are read from the code that
+produces the page, not guessed from a JSON sample.
+
+## What `docc merge` builds
+
+`MergeAction.makeSynthesizedLandingPage(...)` constructs a `RenderNode` with:
+
+- `identifier`, `kind: .article`
+- `metadata.title` = `--synthesized-landing-page-name`
+- `metadata.roleHeading` = `--synthesized-landing-page-kind` (e.g. `"Project"`)
+- `metadata.role` = `"collection"`
+- `topicSectionsStyle` from `--synthesized-landing-page-topics-style`
+- `topicSections` = one or two sections (`"Modules"` / `"Tutorials"`, or a
+  single unnamed section) built from every root-level render reference found
+  under the merged archives' `data/documentation/` and `data/tutorials/`
+- `sections = []` — **the synthesized page starts with zero primary content
+  sections.** There is no auto-generated abstract or body prose.
+
+`renderNode.sections` is the in-memory name for what encodes to the JSON key
+**`primaryContentSections`** (see
+[`RenderNode.swift`](https://github.com/swiftlang/swift-docc/blob/main/Sources/SwiftDocC/Model/Rendering/RenderNode.swift)
+/
+[`RenderNode+Codable.swift`](https://github.com/swiftlang/swift-docc/blob/main/Sources/SwiftDocC/Model/Rendering/RenderNode/RenderNode%2BCodable.swift):
+`primaryContentSectionsVariants`, encoded via `encodeVariantCollectionArrayIfNotEmpty`).
+Because it starts empty, **the key is absent from the emitted JSON entirely**
+(empty variant collections are omitted, not written as `[]`). Don't assume the
+key exists — check for it before indexing into it.
+
+## Where prose paragraphs live: `primaryContentSections`
+
+A content section on any `RenderNode` (landing page included) has exactly two
+JSON keys — confirmed from
+[`ContentRenderSection.swift`](https://github.com/swiftlang/swift-docc/blob/main/Sources/SwiftDocC/Model/Rendering/Symbol/ContentRenderSection.swift):
+
+```jsonc
+{
+  "kind": "content",
+  "content": [ /* RenderBlockContent[] */ ]
+}
+```
+
+`heading` is a constructor convenience on the Swift side only — passing one
+inserts a `heading` block at index 0 of `content`; it is **not** a separate
+JSON key.
+
+A plain paragraph block (confirmed against real fixtures under
+[`Tests/SwiftDocCTests/Rendering/Rendering Fixtures/tables.json`](<https://github.com/swiftlang/swift-docc/blob/main/Tests/SwiftDocCTests/Rendering/Rendering%20Fixtures/tables.json>)
+and
+[`Tests/SwiftDocCTests/Test Resources/link-button-render-node.json`](<https://github.com/swiftlang/swift-docc/blob/main/Tests/SwiftDocCTests/Test%20Resources/link-button-render-node.json>)):
+
+```jsonc
+{
+  "type": "paragraph",
+  "inlineContent": [
+    { "type": "text", "text": "Swift version: 6.3" }
+  ]
+}
+```
+
+So the minimal addition to make the landing page show one paragraph of body
+text is:
+
+```jsonc
+"primaryContentSections": [
+  {
+    "kind": "content",
+    "content": [
+      {
+        "type": "paragraph",
+        "inlineContent": [
+          { "type": "text", "text": "Swift version: 6.3" }
+        ]
+      }
+    ]
+  }
+]
+```
+
+This renders as normal running prose **above the Topics section** and below
+the title/role-heading — it is body content, not the short one-line
+`abstract` teaser (a separate, also-currently-absent top-level key).
+
+## Where this lives in our pipeline
+
+`scripts/curate_navigator.py` → `set_version_paragraph(archive_path, text)`:
+reads `data/documentation.json`, unconditionally replaces
+`doc["primaryContentSections"]` with a single content section containing one
+paragraph, writes atomically. No-op if the file is missing. Because it
+replaces the array wholesale rather than appending, calling it repeatedly
+(e.g. re-running the build) is idempotent — it does not accumulate
+paragraphs.
+
+Called from `scripts/build_docs.py` → `_finalize_combined_archive()`,
+**unconditionally** (not gated on `navigation.json` existing, unlike
+`curate_navigator()`/topic-section curation), right after `merge_archives()`
+succeeds and before the static-hosting transform:
+
+```python
+descriptive_name = (version or {}).get("descriptive-name")
+if descriptive_name:
+    set_version_paragraph(combined_output, f"Swift version: {descriptive_name}")
+```
+
+`version` is the full `sources.json` `"version"` object
+(`{"slug": ..., "descriptive-name": ...}`); the text is built here in
+`build_docs.py`, not inside `curate_navigator.py`, so `set_version_paragraph`
+stays a generic "set this text as the landing page body" primitive.
+
+### Why it must run before the static-hosting transform
+
+`transform_static_hosting()` runs `docc process-archive
+transform-for-static-hosting`, which produces a **fresh archive** at a temp
+path and then replaces the original wholesale (`shutil.rmtree` +
+`shutil.move`). Whatever is in `data/documentation.json` at the time that
+command runs is what gets baked into the final per-route HTML; editing the
+JSON afterward doesn't help because the static-hosting archive may not carry
+the same `data/*.json` structure forward. Same ordering constraint as
+`curate_navigator()`'s landing-page section rewriting — see
+`hacking-index-json.md`.
+
+## Extending this further
+
+To add more structure (multiple paragraphs, a heading, a link, an aside) to
+the landing page body, grow the `content` array inside the single content
+section using the same `RenderBlockContent` shapes DocC itself emits —
+check
+[`Sources/SwiftDocC/Model/Rendering/Content/RenderBlockContent.swift`](https://github.com/swiftlang/swift-docc/blob/main/Sources/SwiftDocC/Model/Rendering/Content/RenderBlockContent.swift)
+for the `type` enum and each case's JSON shape, and cross-reference a fixture
+under
+[`Tests/SwiftDocCTests/Rendering/Rendering Fixtures/`](<https://github.com/swiftlang/swift-docc/tree/main/Tests/SwiftDocCTests/Rendering/Rendering%20Fixtures>)
+before trusting a shape. Useful block `type`s seen in fixtures: `paragraph`,
+`heading`, `aside`, `codeListing`, `orderedList`/`unorderedList`, `table`,
+`links` (card grid).
+
+If a change needs a different *inline* content shape (e.g. a link, code
+voice, or emphasis inside the paragraph), the encoding for `RenderInlineContent`
+follows the same "read the Swift source, confirm against a fixture" approach —
+don't guess key names from memory, DocC's render JSON schema evolves.
+
+For a broader, HTML-rendered walkthrough of the RenderNode/RenderIndex JSON
+structures (a faster first stop than grepping Swift source for an unfamiliar
+shape), see [`heckj/DocCArchive`](https://github.com/heckj/DocCArchive)'s
+[`docs/`](https://github.com/heckj/DocCArchive/tree/main/docs) directory,
+published at <https://heckj.github.io/DocCArchive/>.
+
+## Gotchas
+
+- **Don't assume `primaryContentSections` exists.** It's omitted, not `[]`,
+  when empty — `doc.get("primaryContentSections")` before indexing.
+- **`abstract` is a different, separate key** (the short one-line teaser under
+  the title) — also omitted when empty on the synthesized landing page. Don't
+  conflate it with `primaryContentSections`; this doc's approach targets body
+  prose, not the teaser line.
+- **Ordering vs. navigator curation:** `set_version_paragraph()` and
+  `curate_navigator()` both rewrite `data/documentation.json` but touch
+  disjoint keys (`primaryContentSections` vs. `topicSections`/`references`),
+  so call order between them doesn't matter — verified by both being simple
+  read-modify-write-atomic passes over the same file.
+- **Local toolchain mismatches are real.** A quick empirical `docc convert`/
+  `docc merge` smoke test against a much newer local Xcode beta toolchain
+  produced *no* `data/` directory at all (content baked directly into HTML
+  instead) — don't trust ad hoc local repro against a toolchain newer than the
+  one this repo pins; prefer reading the pinned `swift-docc` source directly.
diff --git a/scripts/sources.json b/scripts/sources.json
index 256ad072..1a260a97 100644
--- a/scripts/sources.json
+++ b/scripts/sources.json
@@ -1,5 +1,8 @@
 {
-  "version": "main",
+  "version": {
+    "slug": "main",
+    "descriptive-name": "prototype"
+  },
   "sources": [
     {
       "id": "swift-book",
diff --git a/scripts/test_build_docs.py b/scripts/test_build_docs.py
index 88402173..1bb6530a 100644
--- a/scripts/test_build_docs.py
+++ b/scripts/test_build_docs.py
@@ -46,7 +46,49 @@ def _validate(config):
 
 
 def _wrap(entry):
-    return {"version": "main", "sources": [entry]}
+    return {
+        "version": {"slug": "main", "descriptive-name": "prototype"},
+        "sources": [entry],
+    }
+
+
+class ValidateVersionField(unittest.TestCase):
+    def _config(self, version):
+        return {
+            "version": version,
+            "sources": [{
+                "id": "stdlib",
+                "type": "archive",
+                "url": "https://example.com/Swift.doccarchive.tar.gz",
+                "docc_archive_name": "Swift.doccarchive",
+            }],
+        }
+
+    def test_valid_version_object(self):
+        output = _validate(self._config({"slug": "main", "descriptive-name": "prototype"}))
+        self.assertIsNone(output)
+
+    def test_version_missing_is_rejected(self):
+        config = self._config({"slug": "main", "descriptive-name": "prototype"})
+        del config["version"]
+        output = _validate(config)
+        self.assertIsNotNone(output)
+        self.assertIn("version", output)
+
+    def test_version_as_plain_string_is_rejected(self):
+        output = _validate(self._config("main"))
+        self.assertIsNotNone(output)
+        self.assertIn("version", output)
+
+    def test_version_missing_slug_is_rejected(self):
+        output = _validate(self._config({"descriptive-name": "prototype"}))
+        self.assertIsNotNone(output)
+        self.assertIn("slug", output)
+
+    def test_version_missing_descriptive_name_is_rejected(self):
+        output = _validate(self._config({"slug": "main"}))
+        self.assertIsNotNone(output)
+        self.assertIn("descriptive-name", output)
 
 
 class ValidateArchiveType(unittest.TestCase):
@@ -749,7 +791,7 @@ def fake_run(cmd, **kw):
             with mock.patch.object(build_docs.subprocess, "run", side_effect=fake_run):
                 build_docs.merge_archives(
                     [archive], output, ["docc"],
-                    landing_page_name=f"Swift - {version}",
+                    landing_page_name="Swift Documentation",
                 )
             return captured["cmd"]
 
@@ -758,7 +800,7 @@ def test_passes_landing_page_name_and_list_style(self):
 
         self.assertIn("--synthesized-landing-page-name", cmd)
         name_idx = cmd.index("--synthesized-landing-page-name") + 1
-        self.assertEqual(cmd[name_idx], "Swift - 6.2")
+        self.assertEqual(cmd[name_idx], "Swift Documentation")
 
         self.assertIn("--synthesized-landing-page-topics-style", cmd)
         style_idx = cmd.index("--synthesized-landing-page-topics-style") + 1
@@ -768,10 +810,13 @@ def test_passes_landing_page_name_and_list_style(self):
         kind_idx = cmd.index("--synthesized-landing-page-kind") + 1
         self.assertEqual(cmd[kind_idx], "Project")
 
-    def test_landing_page_name_uses_version_verbatim(self):
-        cmd = self._capture_merge_cmd("main")
-        name_idx = cmd.index("--synthesized-landing-page-name") + 1
-        self.assertEqual(cmd[name_idx], "Swift - main")
+    def test_landing_page_name_is_version_independent(self):
+        cmd_main = self._capture_merge_cmd("main")
+        cmd_6_2 = self._capture_merge_cmd("6.2")
+        name_idx_main = cmd_main.index("--synthesized-landing-page-name") + 1
+        name_idx_6_2 = cmd_6_2.index("--synthesized-landing-page-name") + 1
+        self.assertEqual(cmd_main[name_idx_main], "Swift Documentation")
+        self.assertEqual(cmd_6_2[name_idx_6_2], "Swift Documentation")
 
 
 class FinalizeCombinedArchive(unittest.TestCase):
@@ -841,6 +886,29 @@ def fake_run(cmd, **kw):
         self.assertEqual(succeeded, ["combined-merge"])
         self.assertEqual(failed, ["static-hosting-transform"])
 
+    def test_merge_uses_fixed_landing_page_name_regardless_of_version(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            tmp_path = Path(tmp)
+            archive = tmp_path / "a.doccarchive"
+            archive.mkdir()
+
+            calls = []
+
+            def fake_run(cmd, **kw):
+                calls.append(cmd)
+                out_idx = cmd.index("--output-path") + 1
+                Path(cmd[out_idx]).mkdir(parents=True, exist_ok=True)
+                raise subprocess.CalledProcessError(1, cmd)
+
+            with mock.patch.object(build_docs.subprocess, "run", side_effect=fake_run):
+                build_docs._finalize_combined_archive(
+                    [archive], tmp_path, "6.2", ["docc"], prior_failed=[]
+                )
+
+            merge_cmd = calls[0]
+            name_idx = merge_cmd.index("--synthesized-landing-page-name") + 1
+            self.assertEqual(merge_cmd[name_idx], "Swift Documentation")
+
     def test_full_success_records_both_steps(self):
         with tempfile.TemporaryDirectory() as tmp:
             tmp_path = Path(tmp)
@@ -870,6 +938,44 @@ def fake_run(cmd, **kw):
         self.assertEqual(succeeded, ["combined-merge", "static-hosting-transform"])
         self.assertEqual(failed, [])
 
+    def test_version_paragraph_written_to_landing_page(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            tmp_path = Path(tmp)
+            archive = tmp_path / "a.doccarchive"
+            archive.mkdir()
+            captured = {}
+
+            def fake_run(cmd, **kw):
+                if "merge" in cmd:
+                    out_idx = cmd.index("--output-path") + 1
+                    out = Path(cmd[out_idx])
+                    out.mkdir(parents=True, exist_ok=True)
+                    (out / "index.html").write_text("merged")
+                    _write_landing_page(out, [("Modules", ["doc://Test/documentation/Swift"])])
+                    return subprocess.CompletedProcess(cmd, 0)
+                # transform-for-static-hosting: capture the landing page as it
+                # stood right before docc replaces the archive in place.
+                archive_arg = Path(cmd[cmd.index("transform-for-static-hosting") + 1])
+                captured["doc"] = json.loads(
+                    (archive_arg / "data" / "documentation.json").read_text()
+                )
+                out_idx = cmd.index("--output-path") + 1
+                out = Path(cmd[out_idx])
+                out.mkdir(parents=True, exist_ok=True)
+                (out / "index.html").write_text("transformed")
+                return subprocess.CompletedProcess(cmd, 0)
+
+            with mock.patch.object(build_docs.subprocess, "run", side_effect=fake_run):
+                build_docs._finalize_combined_archive(
+                    [archive], tmp_path, "main", ["docc"], prior_failed=[],
+                    version={"slug": "main", "descriptive-name": "6.3"},
+                )
+
+        self.assertEqual(
+            captured["doc"]["primaryContentSections"][0]["content"][0]["inlineContent"][0]["text"],
+            "Swift version: 6.3",
+        )
+
     def _merge_writes_index(self, modules):
         """Build a fake subprocess.run that writes a merged index.json on merge.
 
@@ -887,7 +993,7 @@ def fake_run(cmd, **kw):
                     "schemaVersion": {"major": 0, "minor": 1, "patch": 2},
                     "interfaceLanguages": {
                         "swift": [{
-                            "title": "Swift - main",
+                            "title": "Swift Documentation",
                             "children": [
                                 {"type": "module", "title": t, "path": p}
                                 for t, p in modules
@@ -1229,7 +1335,7 @@ def _make_index(tmp_path, children, langs=("swift",)):
         "interfaceLanguages": {
             lang: [
                 {
-                    "title": "Swift - main",
+                    "title": "Swift Documentation",
                     "children": [dict(c) for c in children],
                     "path": "/documentation",
                     "type": "module",
@@ -1248,7 +1354,10 @@ def _children_of(archive, lang="swift"):
 
 
 class ValidateNavigation(unittest.TestCase):
-    SOURCES = {"version": "main", "sources": [{"id": "a"}, {"id": "b"}]}
+    SOURCES = {
+        "version": {"slug": "main", "descriptive-name": "prototype"},
+        "sources": [{"id": "a"}, {"id": "b"}],
+    }
 
     def _nav(self, **over):
         nav = {
@@ -1470,6 +1579,46 @@ def test_unlisted_module_raises(self):
                 curate_navigator.dry_run(archive, self._nav())
 
 
+class AutoArchiveVersionSlug(unittest.TestCase):
+    """_auto_archive must resolve the {slug, descriptive-name} version object."""
+
+    def _sources_path(self, tmp_path):
+        scripts_dir = tmp_path / "scripts"
+        scripts_dir.mkdir()
+        return scripts_dir / "sources.json"
+
+    def test_uses_slug_from_version_object(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            tmp_path = Path(tmp)
+            sources_path = self._sources_path(tmp_path)
+            sources = {
+                "version": {"slug": "main", "descriptive-name": "prototype"},
+                "sources": [],
+            }
+            index_dir = tmp_path / ".build-output" / "main" / "index"
+            index_dir.mkdir(parents=True)
+            (index_dir / "index.json").write_text("{}")
+
+            found = validate_navigation_cli._auto_archive(sources, sources_path)
+            self.assertEqual(found, tmp_path.resolve() / ".build-output" / "main")
+
+    def test_missing_slug_returns_none(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            tmp_path = Path(tmp)
+            sources_path = self._sources_path(tmp_path)
+            sources = {
+                "version": {"descriptive-name": "prototype"},
+                "sources": [],
+            }
+            self.assertIsNone(validate_navigation_cli._auto_archive(sources, sources_path))
+
+    def test_version_missing_entirely_returns_none(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            tmp_path = Path(tmp)
+            sources_path = self._sources_path(tmp_path)
+            self.assertIsNone(validate_navigation_cli._auto_archive({"sources": []}, sources_path))
+
+
 class ValidateNavigationCLI(unittest.TestCase):
     def _setup(self, tmp, nav, sources, archive_modules=None):
         """Write nav + sources files (and optionally an archive); return argv."""
@@ -1484,7 +1633,10 @@ def _setup(self, tmp, nav, sources, archive_modules=None):
             argv += ["--archive", str(archive)]
         return argv
 
-    SOURCES = {"version": "main", "sources": [{"id": "a"}, {"id": "b"}]}
+    SOURCES = {
+        "version": {"slug": "main", "descriptive-name": "prototype"},
+        "sources": [{"id": "a"}, {"id": "b"}],
+    }
 
     def _nav(self):
         return {
@@ -1721,5 +1873,53 @@ def test_landing_page_idempotent(self):
         self.assertEqual(once, twice)
 
 
+class SetVersionParagraph(unittest.TestCase):
+    def test_adds_paragraph_content_section(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            archive = Path(tmp)
+            _write_landing_page(archive, [("Modules", ["doc://Test/documentation/Swift"])])
+            curate_navigator.set_version_paragraph(archive, "Swift version: 6.3")
+            doc = json.loads((archive / "data" / "documentation.json").read_text())
+
+        self.assertEqual(doc["primaryContentSections"], [{
+            "kind": "content",
+            "content": [{
+                "type": "paragraph",
+                "inlineContent": [{"type": "text", "text": "Swift version: 6.3"}],
+            }],
+        }])
+
+    def test_overwrites_existing_primary_content_sections(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            archive = Path(tmp)
+            _write_landing_page(archive, [("Modules", ["doc://Test/documentation/Swift"])])
+            curate_navigator.set_version_paragraph(archive, "Swift version: 6.3")
+            curate_navigator.set_version_paragraph(archive, "Swift version: 6.4")
+            doc = json.loads((archive / "data" / "documentation.json").read_text())
+
+        self.assertEqual(len(doc["primaryContentSections"]), 1)
+        self.assertEqual(
+            doc["primaryContentSections"][0]["content"][0]["inlineContent"][0]["text"],
+            "Swift version: 6.4",
+        )
+
+    def test_preserves_topic_sections_and_references(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            archive = Path(tmp)
+            _write_landing_page(archive, [("Modules", ["doc://Test/documentation/Swift"])])
+            before = json.loads((archive / "data" / "documentation.json").read_text())
+            curate_navigator.set_version_paragraph(archive, "Swift version: 6.3")
+            after = json.loads((archive / "data" / "documentation.json").read_text())
+
+        self.assertEqual(after["topicSections"], before["topicSections"])
+        self.assertEqual(after["references"], before["references"])
+
+    def test_missing_landing_page_is_noop(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            archive = Path(tmp)
+            curate_navigator.set_version_paragraph(archive, "Swift version: 6.3")
+            self.assertFalse((archive / "data" / "documentation.json").exists())
+
+
 if __name__ == "__main__":
     unittest.main()
\ No newline at end of file
diff --git a/scripts/validate_navigation.py b/scripts/validate_navigation.py
index c6c98cc6..6627221d 100755
--- a/scripts/validate_navigation.py
+++ b/scripts/validate_navigation.py
@@ -60,14 +60,17 @@ def _load_json(path):
 def _auto_archive(sources, sources_path):
     """Return the conventional combined archive path if it exists, else None.
 
-    Resolved relative to sources.json (…/<dir>/../.build-output/<version>), so
+    Resolved relative to sources.json (…/<dir>/../.build-output/<slug>), so
     pointing --sources at a throwaway file does not pick up the real build.
     """
     version = sources.get("version")
-    if not version:
+    if not isinstance(version, dict):
+        return None
+    slug = version.get("slug")
+    if not slug:
         return None
     repo_root = Path(sources_path).resolve().parent.parent
-    candidate = repo_root / ".build-output" / str(version)
+    candidate = repo_root / ".build-output" / slug
     return candidate if (candidate / "index" / "index.json").is_file() else None