phase: 106_document_dates

Everything is verified green. Final report:

**Phase 106 — Document dates (final verification pass; all 10 tasks already complete)**

- Verified all phase artifacts: alembic `0020` (dev DB at `0020`), `doc_dates.py`, git `file_commit_dates`, importer `doc_dates_by_root`/`dates_updated`, both entry-point wirings, date APIs + tree `created_at`/`updated_at`, LLM surfaces (prompt block, `read` line 2, appended `ls` field), `apply_recency_boost` in `retrieve()`, UI columns/badge, admin editor, mock-LLM regex — all present and correct; no defects found, no fixes needed.
- `uv run pytest --cov=app --cov-report=term-missing` → **2299 passed, TOTAL 99%** (>90% ✓)
- `uv run pytest tests/e2e/test_document_dates.py -v --no-cov` → **6/6 passed** in isolation (DB up)
- 12 regression E2E suites (retrieval_quality, whole_document_context, agent_document_tools, ls_tree_drilldown, read_truncation_cap, kb_tree, kb_tree_nav, document_viewer, edit_summaries, import_documents, sync_button, hidden_folders_toggle, smoke) → **all green in isolation**
- `uv run ruff check .` → clean; `uv run pyright` → **0 errors, 0 warnings**

**Completion criteria:** 1) non-null `created_at` + 0020 upgrade/downgrade on dev DB ✓ (real-Alembic integration tests) 2) sync refresh/older/manual-persists/content-reset/no sources_meta bump ✓ 3) zip/tar mtime + future→today ✓ 4) LLM date surfaces + cross-check ✓ 5) UI Created/Updated/badge positions ✓ 6) admin editor set+revert round-trip ✓ 7) old-correct-beats-new-similar (defaults & boost-off) + near-tie + `BOR_RECENCY_BOOST=0` byte-identical ✓ 8) full gate ✓ 9) commit/phase-move — left to harness per instructions.

- **Notable:** recency default tuned 0.001 → **0.0007** (task 07 step 5 explicitly permits; measured margins recorded in `test_recency_boost.py` docstring).
- **Next pending phase:** none — `todo/` holds only this phase.

app/api/docs.py

@@ -10,6 +10,14 @@ update or clear ``documents.summary`` and re-embed the ``is_summary``
 chunk (embed first, mutate second — a failed LLM call leaves the row and
 chunk untouched; the content chunks are never re-embedded, D4).
 
+PATCH /api/documents/date — the admin document-date editor (phase 106,
+D7): set the owner's corrected ``documents.created_at`` (normalized
+through ``app.rag.doc_dates.normalize_doc_date`` — a manually set future
+date folds to today, D3) + flag it manual, or clear the manual flag
+(null date — the stored date stands until the next sync). A pure DB
+write: NO LLM/embedding call — a date is never embedded (the
+deliberate contrast with the phase-57 ``is_summary`` re-embed).
+
 GET /api/docs/tree — the admin's full recursive KB tree in one fetch
 (phase 97, task 02): the same drill-down tree the agent's ``ls``
 walks, with the file metadata the RAG view's rows and stat cards need
@@ -40,10 +48,13 @@ from app.core.auth import require_admin, require_user
 from app.db import get_db
 from app.models import Chunk, Document, FolderSummary
 from app.rag.agent import list_source_names
+from app.rag.doc_dates import normalize_doc_date
 from app.rag.folder_summaries import MIN_DOCS_PER_FOLDER, folder_of
 from app.rag.importer import match_extension
 from app.rag.llm import EmbeddingError, LLMClient
 from app.schemas import (
+    DateResult,
+    DateUpdate,
     DocContent,
     DocList,
     DocSummary,
@@ -101,10 +112,18 @@ def list_indexed_documents(
             Document.path,
             Document.title,
             func.count(Chunk.id).label("chunks"),
+            Document.created_at,
             Document.indexed_at,
         )
         .outerjoin(Chunk, Chunk.document_id == Document.id)
-        .group_by(Document.id, Document.source, Document.path, Document.title, Document.indexed_at)
+        .group_by(
+            Document.id,
+            Document.source,
+            Document.path,
+            Document.title,
+            Document.created_at,
+            Document.indexed_at,
+        )
         .order_by(Document.source, Document.path)
     ).all()
     return DocList(
@@ -115,6 +134,7 @@ def list_indexed_documents(
                 path=row.path,
                 title=row.title,
                 chunks=row.chunks,
+                created_at=row.created_at.isoformat(),
                 indexed_at=row.indexed_at.isoformat(),
             )
             for row in rows
@@ -157,6 +177,7 @@ def get_document_content(
         title=doc.title,
         format=doc_format(doc.path, get_settings().import_extension_set),
         summary=doc.summary,
+        created_at=doc.created_at.isoformat(),
         content=doc.content,
         indexed_at=doc.indexed_at.isoformat(),
         chunks=chunks,
@@ -231,6 +252,75 @@ async def update_document_summary(
     )
 
 
+@router.patch("/documents/date", response_model=DateResult)
+def update_document_date(
+    payload: DateUpdate,
+    db: Session = Depends(get_db),  # noqa: B008
+    _admin: None = Depends(require_admin),  # noqa: B008
+) -> DateResult:
+    """Set or clear the owner's correction of a document's creation date.
+
+    Admin-only (phase 106, D7 — the phase-57 split): the document
+    viewer itself stays user-gated (``/documents/content`` — admin OR
+    token holder); only this edit affordance is admin-gated. DB-only
+    (the ``/documents/content`` row-lookup rule): the ``(source, path)``
+    pair is looked up as a row — an unknown pair, including traversal
+    strings such as ``../../etc/passwd``, is simply not a row (→ 404
+    ``document not found``), and there is no filesystem access. NO
+    LLM/embedding call — a date is never embedded (no chunk, no
+    retrieval role) — the deliberate contrast with the phase-57
+    ``is_summary`` re-embed in :func:`update_document_summary`.
+
+    * **Set** (``date`` present) — ``datetime.fromisoformat`` accepts a
+      bare ``YYYY-MM-DD`` (midnight) and full ISO datetimes; a
+      MALFORMED value 422s here (the model field is an unconstrained
+      ``str | None`` on purpose, so the detail can name the field). The
+      parse goes through
+      :func:`app.rag.doc_dates.normalize_doc_date` (D3 — the single
+      choke point: naive → UTC, aware → converted, a manually set
+      FUTURE date also folds to today — consistency with the sourced
+      path) and stores ``created_at`` + ``created_at_manual = True``
+      (the owner's correction — the sync-time importer then SKIPS the
+      refresh on this row, D1/D4).
+    * **Clear** (``date`` null/absent — the "revert to sync"
+      operation) — ``created_at_manual = False`` ONLY: the stored date
+      stands until the next sync refreshes it (the API cannot
+      re-read the source, D7).
+
+    The response echoes the stored state — ``created_at`` (ISO-8601)
+    + ``created_at_manual`` — the viewer re-renders its Created badge
+    from it (no second fetch).
+    """
+    doc = db.scalar(
+        select(Document).where(
+            Document.source == payload.source, Document.path == payload.path
+        )
+    )
+    if doc is None:
+        raise HTTPException(status_code=404, detail="document not found")
+    if payload.date:
+        try:
+            parsed = datetime.fromisoformat(payload.date)
+        except ValueError:
+            raise HTTPException(
+                status_code=422,
+                detail="date must be an ISO date or datetime (e.g. 2024-06-15)",
+            ) from None
+        doc.created_at = normalize_doc_date(parsed)
+        doc.created_at_manual = True
+    else:
+        # The CLEAR (D7): drop the manual flag only — the stored date
+        # stands until the next sync refreshes it.
+        doc.created_at_manual = False
+    db.commit()
+    return DateResult(
+        source=doc.source,
+        path=doc.path,
+        created_at=doc.created_at.isoformat(),
+        created_at_manual=doc.created_at_manual,
+    )
+
+
 @router.patch("/folders/summary", response_model=FolderSummaryResult)
 def update_folder_summary(
     payload: FolderSummaryUpdate,
@@ -305,16 +395,17 @@ def update_folder_summary(
 
 
 #: One catalogue row the tree builder consumes:
-#: ``(source, path, title, chunks, indexed_at)`` — the ``GET /api/docs``
-#: query's columns minus the document ``id`` (the tree has no document
-#: ids), in the same ``(source, path)`` order; ``indexed_at`` is the
-#: ISO-8601 string the endpoint converts (the builder stays pure over
-#: plain types — unit-testable without a DB).
-TreeDocRow = tuple[str, str, str, int, str]
+#: ``(source, path, title, chunks, indexed_at, created_at)`` — the
+#: ``GET /api/docs`` query's columns minus the document ``id`` (the
+#: tree has no document ids), in the same ``(source, path)`` order;
+#: ``indexed_at`` / ``created_at`` are the ISO-8601 strings the
+#: endpoint converts (the builder stays pure over plain types —
+#: unit-testable without a DB).
+TreeDocRow = tuple[str, str, str, int, str, str]
 
 #: One of a source's file rows, already source-scoped:
-#: ``(path, title, chunks, indexed_at)``.
-TreeFileRow = tuple[str, str, int, str]
+#: ``(path, title, chunks, indexed_at, created_at)``.
+TreeFileRow = tuple[str, str, int, str, str]
 
 
 def _folder_counts(
@@ -339,13 +430,13 @@ def _folder_counts(
     own descendants, or the file wearing its name, exist).
     """
     folders: set[str] = set()
-    for path, _title, _chunks, _indexed_at in rows:
+    for path, _title, _chunks, _indexed_at, _created_at in rows:
         folder = folder_of(path)
         while folder:
             folders.add(folder)
             folder = folder_of(folder)
     counts: dict[str, int] = {folder: 0 for folder in folders}
-    for path, _title, _chunks, _indexed_at in rows:
+    for path, _title, _chunks, _indexed_at, _created_at in rows:
         if path in folders:
             counts[path] += 1
         folder = folder_of(path)
@@ -381,27 +472,60 @@ def _level_children(
     flag: the recursive count ≥ :data:`MIN_DOCS_PER_FOLDER` AND no
     stored ``folder_summaries`` row for ``(source, sub)`` — the same
     rule the source node applies (see :func:`build_kb_tree`).
+
+    And, since phase 106 (D9), each folder node carries ``updated_at``
+    = the subtree's MAX document ``created_at``: the max over this
+    folder's direct files' dates and its subfolder children's (already
+    recursive) ``updated_at`` values, via :func:`_subtree_max`.
     """
     children: list[KbTreeFolder | KbTreeFile] = []
     for sub in sorted(g for g in folders if folder_of(g) == folder):
+        sub_children = _level_children(source, sub, folders, counts, rows, summaries)
         children.append(
             KbTreeFolder(
                 path=sub,
                 documents=counts[sub],
+                updated_at=_subtree_max(sub_children),
                 summary=summaries.get((source, sub)),
                 summary_pending=counts[sub] >= MIN_DOCS_PER_FOLDER
                 and (source, sub) not in summaries,
-                children=_level_children(source, sub, folders, counts, rows, summaries),
+                children=sub_children,
             )
         )
-    for path, title, chunks, indexed_at in rows:
+    for path, title, chunks, indexed_at, created_at in rows:
         if folder_of(path) == folder:
             children.append(
-                KbTreeFile(path=path, title=title, chunks=chunks, indexed_at=indexed_at)
+                KbTreeFile(
+                    path=path,
+                    title=title,
+                    chunks=chunks,
+                    created_at=created_at,
+                    indexed_at=indexed_at,
+                )
             )
     return children
 
 
+def _subtree_max(children: Sequence[KbTreeFolder | KbTreeFile]) -> str | None:
+    """A node's ``updated_at`` (phase 106, D9): the subtree's MAX
+    document ``created_at``, computed from the node's direct children —
+    files contribute their ``created_at``, subfolder nodes contribute
+    their (already recursive) ``updated_at``.
+
+    All values share the same UTC ``isoformat()`` shape (the endpoint
+    converts every ``created_at`` before the builder runs), so the
+    LEXICOGRAPHIC max is the chronological max — ISO-8601 strings of
+    one offset order by instant. ``None`` when no child carries a date
+    (a node with no documents at all — the 0-document source).
+    """
+    dates = [
+        child.created_at if child.kind == "file" else child.updated_at
+        for child in children
+    ]
+    dates = [d for d in dates if d is not None]
+    return max(dates) if dates else None
+
+
 def build_kb_tree(
     names: Sequence[str],
     doc_rows: Sequence[TreeDocRow],
@@ -413,8 +537,9 @@ def build_kb_tree(
 
     *names* — the registry source names in order (``app.rag.agent.
     list_source_names`` — deduped, registry order). *doc_rows* — the
-    catalogue ``(source, path, title, chunks, indexed_at)`` tuples in
-    the ``GET /api/docs`` query order (``source, path``). *summaries* —
+    catalogue ``(source, path, title, chunks, indexed_at, created_at)``
+    tuples (both stamps ISO-8601) in the ``GET /api/docs`` query order
+    (``source, path``). *summaries* —
     ``{(source, folder_path): summary}`` over the stored
     ``folder_summaries`` rows (``folder_path = ""`` = the source root;
     rows for sources the tree does not list are simply never
@@ -433,13 +558,21 @@ def build_kb_tree(
       source node IS the root); direct subfolders only, in path
       (sorted) order, a folder existing only under the phase-94
       existence rule; ``documents`` = the recursive subtree count;
-      ``summary`` = the stored row (AI OR manual — any row) or null;
-      ``children`` = the folder's own subfolders + direct files, same
-      shape.
+      ``updated_at`` (phase 106, D9) = the subtree's MAX document
+      ``created_at`` — DERIVED as the builder recurses (the max of the
+      direct files' dates and the children's ``updated_at`` values via
+      :func:`_subtree_max`; the ISO-8601 strings share one
+      ``isoformat()`` shape, so the lexicographic max is the
+      chronological one), never stored — ``null`` when the node has no
+      documents at all; ``summary`` = the stored row (AI OR manual —
+      any row) or null; ``children`` = the folder's own subfolders +
+      direct files, same shape.
     * **File nodes** — direct files only, in input (catalog) order;
-      ``path`` source-relative; ``title`` / ``chunks`` / ``indexed_at``
-      verbatim from the catalogue row. File nodes carry NO pending
-      flag (the file table has no description column).
+      ``path`` source-relative; ``title`` / ``chunks`` / ``created_at``
+      (phase 106) / ``indexed_at`` verbatim from the catalogue row.
+      File nodes carry NO pending flag (the file table has no
+      description column) and no ``updated_at`` (a file's date IS its
+      ``created_at``).
     * **Pending** — ``summary_pending`` on the SOURCE and every FOLDER
       node (phase 98, decision D3 — ONE concept): true iff the node's
       recursive ``documents`` count ≥
@@ -460,13 +593,20 @@ def build_kb_tree(
     existence / count rules, so — for a single-source dataset — its
     level equals :func:`app.rag.agent.group_folder_listing`'s output
     (same subfolder ``(path, count, summary)`` triples in order, same
-    file ``(path, title)`` pairs in order — the "UI shows what the
-    agent sees" cross-check, unit-pinned at the root and a nested
-    level).
+    file ``(source, path, title, date)`` 4-tuples in order — phase
+    106, D5: the agent's file lines carry the appended ``date`` field
+    and the tree's file nodes carry ``created_at``; the "UI shows
+    what the agent sees" cross-check, unit-pinned at the root and a
+    nested level, compares the extended shapes).
+
+    D9 (phase 106): ``updated_at`` on every SOURCE and FOLDER node is
+    the subtree's MAX document ``created_at`` — derived, never stored;
+    ``None`` for a node with no documents at all (the registered
+    0-document source).
     """
     by_source: dict[str, list[TreeFileRow]] = {}
-    for source, path, title, chunks, indexed_at in doc_rows:
-        by_source.setdefault(source, []).append((path, title, chunks, indexed_at))
+    for source, path, title, chunks, indexed_at, created_at in doc_rows:
+        by_source.setdefault(source, []).append((path, title, chunks, indexed_at, created_at))
     tree: list[KbTreeSource] = []
     listed: set[str] = set()
     for name in names:
@@ -499,14 +639,20 @@ def _source_node(
     ``summary_pending`` (phase 98, D3): the whole-source count ≥
     :data:`MIN_DOCS_PER_FOLDER` AND no stored ``(source, "")`` row —
     the source-root arm of the rule :func:`build_kb_tree` documents.
+
+    ``updated_at`` (phase 106, D9): the source's subtree max —
+    :func:`_subtree_max` over the root level's children; ``None`` for a
+    0-document source (no children, no dates).
     """
     folders, counts = _folder_counts(rows)
+    children = _level_children(source, "", folders, counts, rows, summaries)
     return KbTreeSource(
         name=source,
         documents=len(rows),
+        updated_at=_subtree_max(children),
         summary=summaries.get((source, "")),
         summary_pending=len(rows) >= MIN_DOCS_PER_FOLDER and (source, "") not in summaries,
-        children=_level_children(source, "", folders, counts, rows, summaries),
+        children=children,
     )
 
 
@@ -540,15 +686,23 @@ def list_kb_tree(
             Document.path,
             Document.title,
             func.count(Chunk.id).label("chunks"),
+            Document.created_at,
             Document.indexed_at,
         )
         .outerjoin(Chunk, Chunk.document_id == Document.id)
-        .group_by(Document.id, Document.source, Document.path, Document.title, Document.indexed_at)
+        .group_by(
+            Document.id,
+            Document.source,
+            Document.path,
+            Document.title,
+            Document.created_at,
+            Document.indexed_at,
+        )
         .order_by(Document.source, Document.path)
     ).all()
     doc_rows: list[TreeDocRow] = [
-        (source, path, title, chunks, indexed_at.isoformat())
-        for source, path, title, chunks, indexed_at in rows
+        (source, path, title, chunks, indexed_at.isoformat(), created_at.isoformat())
+        for source, path, title, chunks, created_at, indexed_at in rows
     ]
     summaries: dict[tuple[str, str], str] = {
         (source, folder_path): summary