phase: 100_page_width_consistency

**Phase 100 — final verification pass: all green.**

- Verified the shipped CSS contract directly: `--chat-column: 72rem` in `:root`; 0 literal `max-width: 46rem`; no `@media (min-width: 1500px)` block; exactly 4 token-capped reading columns; tuning/theme/doc-edit shells cap-free, structurally `.sources-shell`; `mock_llm.py` diff is comment-only.
- Defect found & fixed (phase-93 suite): `test_theme_semantic_completion.py::test_reset_removes_tag_byte_identical` raced theme.js's post-PUT refetch — it asserted the `#bor-theme` tag was gone right after the result line, but tag removal lands in the reconcile after the re-fetch (failed ~1 in 5 runs after `test_chat_rag`, reproduced). Fixed with an auto-waiting `expect(...).to_have_count(0)` (settled-state wait, the file's existing house pattern). 6/6 clean on the repro loop after.
- Tests/lint/coverage: `uv run pytest --cov=app --cov-report=term-missing` → 2052 passed, **99%** on `app/`; `uv run ruff check .` + `uv run pyright` → 0 errors.
- E2E in isolation (all passed): `test_wide_desktop_column.py` 3 (the phase suite — chat==tuning==theme==RAG ±4px at 1280 & 1920, ≈1152px; shared ≈1152px; standalone doc ≈1112px; modal unchanged ≈1100px; 360px overflow-free), `test_ui_customization` 4, `test_admin_theme_tab` 5, `test_document_viewer` 7, `test_save_share_ux` 5, `test_sticky_navbar` 3, `test_markdown_tables` 6, `test_responsive_polish` 7, `test_chat_rag` 3, `test_theme_semantic_completion` 8.
- Completion criteria: ① measured 72rem everywhere (≥~1200px, ±4px) + full-width below + 360px clean — **PASS** (E2E); ② zero 46rem rules / no 1500px block / four token selectors — **PASS** (grep + unit pins); ③ B4 byte-identical no-op + mobile squeeze — **PASS** (theme + responsive suites green); ④ full suite / coverage / lint — **PASS**; ⑤ atomic commit — left to the harness per executor protocol (all changes in the working tree, uncommitted).
- Deviations: none from phase decisions; only change in this pass is the race fix above (test-only, behavior unchanged).
- Next pending phase: `98_sync_summary_visibility` (numeric order in `todo/`; also pending: 99, 101–105).

tests/e2e/mock_llm.py

@@ -327,7 +327,8 @@ Implements just enough of the aipi surface:
     a deliberately wide 5-column table — byte-stable, so the story E2E
     can assert the rendered ``<table class="md-table">`` shape, the
     escaped XSS line, and the wrapper's horizontal scroll inside the
-    46rem column. Checked BEFORE the ``DEFLECT_MODE`` branch (a
+    72rem container column (phase 100). Checked BEFORE the
+    ``DEFLECT_MODE`` branch (a
     deflection prompt never carries the marker, same reasoning as
     ``SUMMARY_MODE``), so a marker question always gets the table
     answer; the E2E asks it against an on-topic fixture (HIGH gate) and
@@ -584,7 +585,8 @@ TABLE_TRIGGER = "show me a table"
 #: The fixed table answer (phase 44) — byte-stable on purpose: the story
 #: E2E asserts the rendered table shape, the escaped ``<img onerror>``
 #: line (the XSS payload must survive the mock byte-for-byte), and the
-#: wide table's ``scrollWidth > clientWidth`` inside the 46rem column.
+#: wide table's ``scrollWidth > clientWidth`` inside the 72rem container
+#: column (phase 100).
 #: Phase 74 (chat history, TODO L4): a user message containing this
 #: substring (case-insensitive) gets the deterministic HISTORY ECHO
 #: (``_history_echo`` below — see the module docstring): the prior-turn
@@ -1653,7 +1655,8 @@ def compose_answer(body: dict[str, Any]) -> str:
         # <img onerror> XSS probe line (it must survive the mock
         # byte-for-byte so the E2E can prove the renderer neutralizes
         # it), and a wide 5-column table (guarantees scrollWidth >
-        # clientWidth inside the 46rem column). Byte-stable. Checked
+        # clientWidth inside the 72rem container column, phase 100).
+        # Byte-stable. Checked
         # BEFORE the DEFLECT_MODE branch: a deflection prompt never
         # carries the marker (it lives in the user message, same
         # reasoning as SUMMARY_MODE), so a marker question always gets

tests/e2e/test_document_viewer.py

@@ -24,7 +24,9 @@ Test → story mapping (Playwright Mapping Rule):
    renders as escaped text; no dialog fires.
 6. ``test_standalone_page_still_works`` — the dedicated ``/document.html``
    page keeps its phase-10 contract (title/content/badges, not-found,
-   dark theme, no-CDN, a11y frame, ≤736px md column).
+   dark theme, no-CDN, a11y frame, the 72rem-container md column —
+   phase 100: ≈1112px at the 1280px fixture viewport, the container's
+   inner content).
 7. ``test_modal_theme_and_no_cdn`` — dark page background, the panel on
    the Phase-08 surface colour, every asset same-origin or ``data:``.
 """
@@ -406,9 +408,16 @@ def test_standalone_page_still_works(
     expect(page.locator(".doc-shell")).to_have_attribute("aria-live", "polite")
     assert page.evaluate("() => document.activeElement && document.activeElement.id") == "main"
 
-    # Markdown column centered and capped at 46rem (736px at 16px root).
+    # Markdown column: the 72rem container's inner content (phase 100 —
+    # the 46rem cap and its wide-desktop doubling are retired): at the
+    # 1280px fixture viewport the container is 1152px border-box, so
+    # .doc-md (width:100% inside it) measures 1152 − 2×1.25rem = 1112px.
     box = page.locator("#doc-content .doc-md").bounding_box()
-    assert box is not None and box["width"] <= 736 + 1
+    assert box is not None, "the standalone .doc-md column is not rendered"
+    assert abs(box["width"] - 1112) <= 4, (
+        f"the standalone .doc-md column is {box['width']:.0f}px, "
+        f"want 1112px (the 72rem container's inner content) ±4px"
+    )
 
     assert errors == [], f"console crashes: {errors}"
 

tests/e2e/test_markdown_tables.py

@@ -22,7 +22,8 @@ Test → story mapping (Playwright Mapping Rule):
    NOT deflected (the honesty-gate interplay is part of the contract).
 2. ``test_wide_table_scrolls`` — the wide table's wrapper has
    ``scrollWidth > clientWidth`` and horizontal scroll moves it; the
-   page itself has no horizontal overflow (the 46rem column holds).
+   page itself has no horizontal overflow (the 72rem container column
+   holds — phase 100).
 3. ``test_table_xss_safe`` — the ``<img onerror>`` line renders as
    visible, escaped text: zero injected ``<img>`` nodes, no dialog.
 4. ``test_viewer_table_renders`` — the fixture's pipe table opens from
@@ -219,8 +220,8 @@ def test_wide_table_scrolls(
     after = wrap.evaluate("el => el.scrollLeft")
     assert after > before, "the wrapper must scroll horizontally"
 
-    # The 46rem chat column must not break the page: no horizontal
-    # document overflow (PLAN §7.1).
+    # The 72rem container column must not break the page: no horizontal
+    # document overflow (PLAN §7.1, as revised by phase 100).
     page_scroll, page_client = page.evaluate(
         "() => [document.documentElement.scrollWidth, document.documentElement.clientWidth]"
     )

tests/e2e/test_responsive_polish.py

@@ -12,12 +12,13 @@ Test → story mapping:
 1. ``test_no_horizontal_overflow_at_viewports`` — 360/375/768/1280/1600 on
    both pages: ``documentElement.scrollWidth <= clientWidth``.
 2. ``test_chat_column_capped_and_centered`` — the reading column rides
-   --chat-column (46rem base; 92rem at >=1500px, phase 58 / owner
-   instruction 2026-08-31 TODO L5): at 1600px (a wide desktop) the
-   ``.chat-shell`` is 92rem (1472px, ±2%) and horizontally centered
-   (±2%); at 1280px (below the wide breakpoint) it stays ≤ 46rem
-   (736px, +2%); at 768px the column uses most of the width (no
-   mid-column dead zones).
+   --chat-column (72rem — EQUAL to the .container's cap at every
+   viewport, phase 100 / owner instruction 2026-09-12: the 46rem base
+   + the >=1500px 92rem doubling are retired): at 1600px (a wide
+   desktop) the ``.chat-shell`` is the 72rem container (1152px, ±2%)
+   and horizontally centered (±2%); at 1280px the same 1152px (the
+   container cap binds, not the viewport); at 768px the column is
+   full-width (no mid-column dead zones).
 3. ``test_sources_table_full_width`` — at 1280px ``.table-wrap`` ≥ 80% of
    the container; below 640px the table keeps its 640px min-width and the
    wrapper scrolls horizontally instead of squeezing.
@@ -55,8 +56,11 @@ REPO = Path(__file__).resolve().parents[2]
 FIXTURES = REPO / "tests" / "fixtures" / "docs"
 
 VIEWPORTS = ((360, 740), (375, 812), (768, 1024), (1280, 800), (1600, 900))
-CHAT_SHELL_CAP_PX = 46 * 16  # 736px — the --chat-column base (PLAN §7.1 lineage)
-CHAT_SHELL_WIDE_PX = 92 * 16  # 1472px — the 2x wide override (phase 58, >=1500px)
+# Phase 100: the ONE width — the 72rem container, border-box (the
+# 2×1.25rem gutters are inside the measured box). The 46rem base and
+# the 92rem wide-desktop doubling are retired (owner instruction
+# 2026-09-12: "match the width of the RAG page for all other pages").
+CHAT_SHELL_CONTAINER_PX = 72 * 16  # 1152px — the --chat-column = container cap
 
 # Mock-LLM marker for a 3s pre-token window (see tests/e2e/mock_llm.py).
 SLOW_QUESTION = "pretend to think slowly, please"
@@ -225,18 +229,19 @@ def test_no_horizontal_overflow_at_viewports(
 def test_chat_column_capped_and_centered(
     browser: Browser, app_url: str, db_ready: None
 ) -> None:
-    """AC1 (phase 58 contract): the reading column doubles to 92rem on
-    wide desktops (>=1500px — 1600px here), stays at the 46rem base
-    below the breakpoint (1280px), and still uses most of the width on
-    tablets (no mid-column dead zones)."""
+    """AC1 (phase 100 contract): the reading column is the 72rem
+    container at every viewport — 1600px here (the cap binds, not the
+    viewport) and 1280px alike (1152px, ±2%, centered), and still
+    full-width on tablets (no mid-column dead zones). The phase-58
+    46rem/92rem contract it used to pin is retired."""
     page = browser.new_page(viewport={"width": 1600, "height": 900})
     try:
         page.goto(f"{app_url}/")
         box = page.locator(".chat-shell").bounding_box()
         assert box is not None
-        assert CHAT_SHELL_WIDE_PX * 0.98 <= box["width"] <= CHAT_SHELL_WIDE_PX * 1.02, (
-            f"at 1600px (>=1500px) the chat column is {box['width']:.0f}px, "
-            f"not the 92rem wide override (±2%)"
+        assert CHAT_SHELL_CONTAINER_PX * 0.98 <= box["width"] <= CHAT_SHELL_CONTAINER_PX * 1.02, (
+            f"at 1600px the chat column is {box['width']:.0f}px, "
+            f"not the 72rem container (1152px, ±2%)"
         )
         center = box["x"] + box["width"] / 2
         assert abs(center - 1600 / 2) <= 0.02 * 1600, (
@@ -250,9 +255,11 @@ def test_chat_column_capped_and_centered(
         narrow.goto(f"{app_url}/")
         box = narrow.locator(".chat-shell").bounding_box()
         assert box is not None
-        assert box["width"] <= CHAT_SHELL_CAP_PX * 1.02, (
-            f"at 1280px (<1500px) the chat column {box['width']:.0f}px exceeds "
-            f"the 46rem base cap (+2%)"
+        # 1280 > 1152: the container cap binds — the SAME 72rem width as
+        # at 1600px (the cap no longer depends on the viewport at all).
+        assert box["width"] <= CHAT_SHELL_CONTAINER_PX * 1.02, (
+            f"at 1280px the chat column {box['width']:.0f}px exceeds "
+            f"the 72rem container cap (+2%)"
         )
     finally:
         narrow.close()

tests/e2e/test_save_share_ux.py

@@ -41,7 +41,8 @@ unshare, layout) are unchanged.
 * **Layout (L6 / A5)** — desktop 1280×800: ``#new-chat-btn`` and
   ``#share-chat-btn`` share one horizontal row inside ``.chat-actions``
   (overlapping y bands, Share's x beyond New chat's x + width, each
-  pill at intrinsic width — never the full 46rem column); mobile
+  pill at intrinsic width — never the full 72rem container column);
+  mobile
   390×844: stacked vertically (Share below New chat, full-width);
   360px wide: no horizontal page overflow;
 * **Admin still works (A1 sanity)** — the same auto-save machinery
@@ -502,7 +503,7 @@ def test_action_row_layout(page: Page, app_url: str, mock_llm: int, db_ready: No
 
     # Desktop (1280×800): one horizontal row — overlapping y bands,
     # Share to the right of New chat, each pill at its INTRINSIC width
-    # (never the full 46rem chat column).
+    # (never the full 72rem container column — phase 100).
     nb = new_btn.bounding_box()
     sb = share_btn.bounding_box()
     assert nb is not None and sb is not None

tests/e2e/test_sticky_navbar.py

@@ -265,7 +265,7 @@ def test_doc_header_stuck_at_top_on_long_document(
     expect(page.locator("#doc-content .doc-md")).not_to_be_empty()
 
     # The doc must actually scroll (the ~40,000-char body fills many
-    # viewports in the 46rem column).
+    # viewports in the 72rem container column — phase 100).
     sh = page.evaluate("() => document.documentElement.scrollHeight")
     assert sh > VIEWPORT_H, (
         f"the long document must make the page scroll "

tests/e2e/test_theme_semantic_completion.py

@@ -979,10 +979,11 @@ def test_reset_removes_tag_byte_identical(page: Page, app_url: str, db_ready: No
     # The tag is GONE from the live document (theme.js reconciles the
     # #bor-theme tag's DOM text to the settled, now-default values —
     # the no-op case removes the tag and clears the <html>
-    # overrides)…
-    assert 'id="bor-theme"' not in page.content(), (
-        "the reset document must be tag-free"
-    )
+    # overrides). The removal lands in the post-PUT refetch's
+    # reconcile (the result line above only signals the PUT landed),
+    # so WAIT for the settled tag-free state rather than racing the
+    # refetch round-trip…
+    expect(page.locator("#bor-theme")).to_have_count(0, timeout=30_000)
     # …and a FRESH load serves NO tag at all (the all-NULL row is the
     # no-op injection).
     r = httpx.get(app_url + "/", timeout=10)

tests/e2e/test_wide_desktop_column.py

@@ -1,16 +1,33 @@
-"""Phase 58 E2E (Playwright): the 2x reading column on wide desktops —
-measured bounding-box widths, not CSS pins.
+"""Phase 100 E2E (Playwright): every page matches the RAG page's width —
+the full 72rem container at every viewport, measured bounding boxes.
 
-TODO.md L5 (owner instruction 2026-08-31, roadmap confirmation D2 +
-expansion): "The chat response needs to be 2x wider on wide desktops.
-there's a lot of unused space." — extended to the document view. The
-owner-locked contract: viewport >=1500px doubles ``--chat-column`` to
-92rem (1472px at the 16px root) for the four reading shells —
-``.chat-shell``, ``.shared-shell``, ``.doc-md`` and
-``.doc-summary:has(+ .doc-md)`` — while everything below the breakpoint
-renders exactly as before (46rem / 736px) and ``.tuning-shell`` (a
-form, not a reading surface) never widens (CSS-pinned by the unit
-suite, task 01 — the browser proof of the MEASURED width is this file).
+Owner request (chat, 2026-09-12): "The theme, tuning, and chat pages
+are still pretty narrow, I want you to match the width of the RAG page
+for all other pages to keep things consistent." — SUPERSEDES the
+phase-58 2026-08-31 46rem/92rem reading-column contract (recorded per
+the phase-94/96/97 convention in `.agents/phases/todo/
+100_page_width_consistency/00_phase.md`, decisions D1–D4). The phase-58
+suite this file used to be updates IN PLACE to the new contract (the
+phase-97 task-07/08 precedent: a completed phase's suite follows its
+changed contract; its seeding helpers are kept).
+
+The measured contract (the 16px root, the ±4px tolerance is the task
+spec):
+
+* the container is ``min(100%, 72rem)`` border-box with the 2×1.25rem
+  gutters INSIDE the box — at any viewport ≥ ~1200px every shell
+  (``.container.*-shell``) measures **1152px** (72rem), identical on
+  the chat page, Tuning, Theme, and the RAG page;
+* the standalone ``document.html`` page's ``.doc-md`` is the container's
+  inner content — **1112px** (1152 − 2×1.25rem);
+* the same-page document MODAL is untouched (D2): the panel stays
+  **~1100px** and the panel binds the ``.doc-md`` inside it —
+  **1058px** (1100 − 2×1px borders − 2×1.25rem of
+  ``.doc-modal-content`` padding), NOT 1152;
+* below the container cap everything is full-width as before: at 360px
+  no horizontal overflow and the shell is the viewport width; at 900px
+  chat/tuning/theme all measure 900px (equal — the cap never bound
+  below 72rem anyway).
 
 Run in isolation (DB must be up: ``podman compose up -d db``):
 
@@ -18,33 +35,30 @@ Run in isolation (DB must be up: ``podman compose up -d db``):
 
 Test → contract mapping:
 
-1. ``test_chat_column_wide_vs_base`` — ``/`` at 1920×1080: the
-   ``.chat-shell`` bounding box is 1472px (92rem, ±4px) and centered;
-   at 1280×800 (below the wide breakpoint) it is back to 736px
-   (46rem, ±4px).
-2. ``test_document_column_wide_vs_base`` — a seeded markdown document
-   that carries a summary: at 1920 both ``.doc-md`` and the adjacent
-   ``.doc-summary:has(+ .doc-md)`` panel are 1472px; at 1280
-   ``.doc-md`` is 736px.
-3. ``test_shared_column_wide`` — a real auto-saved conversation shared
-   by token: ``/shared/<token>`` at 1920 renders ``.shared-shell`` at
-   1472px in a fresh anonymous context.
-4. ``test_narrow_unchanged`` — 360px: no horizontal overflow and the
-   ``.chat-shell`` is the existing mobile rule — full-bleed at the
-   viewport width (the shell IS its .container; the 0.9rem mobile
-   gutters live in its own padding, inside the measured box), 900px:
-   the shell holds the 46rem base (736px, not the 1472px wide rule —
-   at 900px a leaked wide override would pin the shell to the 860px
-   content box instead, so 736px is the discriminator) — the wide
-   rule does not leak below 1500px.
+1. ``test_all_columns_match_the_rag_page`` — the core pin: at
+   1280×800 the ``.chat-shell`` (``/``), ``.tuning-shell``
+   (``/tuning.html``), ``.theme-shell`` (``/theme.html``) and the RAG
+   page's ``.sources-shell`` (``/sources.html``) bounding boxes are ALL
+   EQUAL (±4px) — the owner's "match the width of the RAG page" as one
+   assertion; at 1920×1080 the same four are still equal to each other
+   and each measures ≈1152px (72rem, ±4px).
+2. ``test_reader_columns_wide`` — the token's consumers at 1920×1080:
+   the modal panel is still ~1100px (D2: the modal is UNCHANGED) with
+   its ``.doc-md`` at ~1058px; ``/shared/<token>``'s ``.shared-shell``
+   is ≈1152px; the standalone ``document.html`` page's ``.doc-md`` is
+   ≈1112px (the 72rem container's inner content).
+3. ``test_narrow_unchanged`` — the no-regression leg: at 360×800 no
+   horizontal overflow and ``.chat-shell`` is the viewport width
+   (full-bleed — the mobile gutters sit in the container's padding,
+   inside the measured box); at 900×600 chat/tuning/theme are all
+   900px wide, equal to each other.
 
 DB isolation: the shared-chat row is deleted in a ``finally`` (admin
 cookie — the house pattern of test_share_chat.py, whose distinctive
 question text keeps the auto-title unique); the fixture document rows
 follow the story-fixture convention of the sibling suites (truncate +
-re-import; the summary document is a direct row insert, the
-test_document_viewer.py XSS-fixture pattern — the viewer is
-database-only).
+re-import; the viewer fixture is a direct row insert — the viewer is
+database-only, the test_document_viewer.py XSS-fixture pattern).
 """
 from __future__ import annotations
 
@@ -70,14 +84,22 @@ from e2e.auth_helpers import login
 REPO = Path(__file__).resolve().parents[2]
 FIXTURES = REPO / "tests" / "fixtures" / "docs"
 
-# The two proof viewports (task spec): wide desktop vs just below the
-# 1500px breakpoint, at the 16px root the phase-58 rem contract:
-# 92rem = 1472px, 46rem = 736px. ±4px tolerance (task spec).
-WIDE_PX = 92 * 16  # 1472px — the 2x wide override (>=1500px)
-BASE_PX = 46 * 16  # 736px — the --chat-column base
-TOL_PX = 4
-WIDE_VIEWPORT: ViewportSize = {"width": 1920, "height": 1080}
-BASE_VIEWPORT: ViewportSize = {"width": 1280, "height": 800}
+# The phase-100 measured contract (16px root, the task spec):
+# * CONTAINER_PX — 72rem border-box, the 2×1.25rem gutters INSIDE the
+#   box; every .container.*-shell measures this at any viewport
+#   >= ~1200px (the RAG page's width — the owner's ask).
+# * DOC_MD_STANDALONE_PX — the standalone document page's .doc-md: the
+#   container's inner content (CONTAINER_PX minus the gutters).
+# * MODAL_PANEL_PX / DOC_MD_MODAL_PX — the SAME-PAGE modal is untouched
+#   (D2): the 1100px border-box panel (minus its 1px borders) and
+#   .doc-modal-content's 2×1.25rem padding bind the .doc-md inside it.
+CONTAINER_PX = 72 * 16  # 1152px — the 72rem container (border-box)
+DOC_MD_STANDALONE_PX = CONTAINER_PX - 2 * 20  # 1112px — inner content
+MODAL_PANEL_PX = 1100  # the phase-26 panel ceiling (D2: unchanged)
+DOC_MD_MODAL_PX = MODAL_PANEL_PX - 2 - 2 * 20  # 1058px — panel-inner
+TOL_PX = 4  # the task spec's ±4px tolerance
+VIEWPORT_1280: ViewportSize = {"width": 1280, "height": 800}
+VIEWPORT_1920: ViewportSize = {"width": 1920, "height": 1080}
 
 MOCK_ANSWER_MARKER = "Deterministic mock answer for E2E"
 SHARE_URL_RE = re.compile(r"^/shared/[0-9a-f-]{36}$")
@@ -139,11 +161,11 @@ def _reset_db(mock_port: int, seed: bool) -> ImportSummary | None:
 
 
 def _seed_summary_doc() -> None:
-    """One markdown document carrying a stored summary — the ONLY shape
-    that renders both reading-column pins on one page: ``.doc-summary``
-    (the phase-36 panel) directly above ``.doc-md`` (the ``:has(
-    + .doc-md)`` sibling match). Direct row insert — the viewer is
-    database-only (the test_document_viewer.py XSS-fixture pattern)."""
+    """One markdown document carrying a stored summary — the viewer
+    fixture the phase-100 suite opens in BOTH the same-page modal and
+    the standalone document page (the test_document_viewer.py
+    XSS-fixture pattern: a direct row insert, the viewer is
+    database-only)."""
     with SessionLocal() as db:
         db.add(
             Document(
@@ -153,11 +175,11 @@ def _seed_summary_doc() -> None:
                 title=FIXTURE_TITLE,
                 content=(
                     "# Wide Column Fixture\n\n"
-                    "Phase-58 width pin: a markdown document with a "
-                    "summary, so the viewer renders the .doc-summary "
-                    "panel directly above the .doc-md column."
+                    "Phase-100 width pin: a markdown document with a "
+                    "summary, opened in the same-page modal and the "
+                    "standalone document page."
                 ),
-                summary="A phase-58 fixture summary for the wide-column pin.",
+                summary="A phase-100 fixture summary for the width pin.",
                 content_hash="w" * 64,
                 indexed_at=datetime.now(UTC),
             )
@@ -170,14 +192,29 @@ def _seed_summary_doc() -> None:
 # ---------------------------------------------------------------------------
 
 
+def _drill(page: Page, *names: str) -> None:
+    """Phase 97: the catalog is the drill-down tree — click through the
+    source/folder rows (exact name match, one per name) to the level
+    that holds the asserted file."""
+    for name in names:
+        page.click(f'#folders-tbody a.folder-link:text-is("{name}")')
+
+
+def _box_width(page: Page, selector: str, label: str) -> float:
+    """The element's bounding-box width (the measured rendered width,
+    not the computed style) — None means the element is not rendered,
+    which is a test error, not a measurement."""
+    box = page.locator(selector).first.bounding_box()
+    assert box is not None, f"{selector} not rendered ({label})"
+    return box["width"]
+
+
 def _assert_width(page: Page, selector: str, expected_px: int, label: str) -> None:
     """The element's bounding-box width is ``expected_px`` ±4px (task
     spec) — the measured rendered width, not the computed style."""
-    box = page.locator(selector).first.bounding_box()
-    assert box is not None, f"{selector} not rendered ({label})"
-    assert abs(box["width"] - expected_px) <= TOL_PX, (
-        f"{label}: {selector} is {box['width']:.1f}px, "
-        f"want {expected_px}px ±{TOL_PX}px"
+    width = _box_width(page, selector, label)
+    assert abs(width - expected_px) <= TOL_PX, (
+        f"{label}: {selector} is {width:.1f}px, want {expected_px}px ±{TOL_PX}px"
     )
 
 
@@ -265,170 +302,206 @@ def _delete_chat(app_url: str, cookies: dict[str, str], chat_id: str) -> None:
     httpx.delete(f"{app_url}/api/chats/{chat_id}", timeout=10, cookies=cookies)
 
 
+def _measure_shells(
+    browser: Browser, app_url: str, viewport: ViewportSize
+) -> dict[str, float]:
+    """One signed-in page at ``viewport``; measure the bounding-box
+    width of every shell under test after its view is shown:
+
+    * ``.chat-shell`` on ``/`` (the chat view — the div IS
+      ``.container.chat-shell``);
+    * ``.tuning-shell`` on ``/tuning.html``, ``.theme-shell`` on
+      ``/theme.html``, and the RAG page's ``.sources-shell`` on
+      ``/sources.html`` (admin deep-links — A11's one shell document).
+    """
+    page = browser.new_page(viewport=viewport)
+    widths: dict[str, float] = {}
+    try:
+        login(page, app_url, next="/")
+        page.locator(".chat-shell").wait_for(state="visible", timeout=10_000)
+        widths[".chat-shell"] = _box_width(page, ".chat-shell", "chat")
+        for path, selector in (
+            ("/tuning.html", ".tuning-shell"),
+            ("/theme.html", ".theme-shell"),
+            ("/sources.html", ".sources-shell"),
+        ):
+            page.goto(app_url + path)
+            page.locator(selector).wait_for(state="visible", timeout=10_000)
+            widths[selector] = _box_width(page, selector, path)
+    finally:
+        page.close()
+    return widths
+
+
 # ---------------------------------------------------------------------------
-# 1. Chat: 1472px at 1920, back to 736px at 1280 (centered both ways)
+# 1. The core pin: chat == tuning == theme == RAG page (±4px), at both
+#    proof viewports; each ≈1152px (the 72rem container) at 1920
 # ---------------------------------------------------------------------------
 
 
-def test_chat_column_wide_vs_base(
+def test_all_columns_match_the_rag_page(
     browser: Browser, app_url: str, db_ready: None
 ) -> None:
-    """The chat page's .chat-shell doubles at the 1500px breakpoint:
-    92rem (1472px, ±4px) at 1920×1080, centered; 46rem (736px, ±4px)
-    at 1280×800 — the base below the breakpoint."""
-    wide = browser.new_page(viewport=WIDE_VIEWPORT)
-    try:
-        login(wide, app_url, next="/")  # phase 79: the chips need a session
-        wide.locator("#suggestions .suggestion-chip").first.wait_for(
-            state="visible", timeout=10_000
+    """The owner's "match the width of the RAG page" as ONE assertion:
+    at 1280×800 the four shells are all EQUAL (±4px); at 1920×1080
+    they are still equal to each other and each measures ≈1152px
+    (72rem at the 16px root, ±4px — the box includes the container's
+    2×1.25rem padding, border-box)."""
+    # --- 1280×800 (just above the container cap — the owner's report) ---
+    widths = _measure_shells(browser, app_url, VIEWPORT_1280)
+    ref_selector, ref = next(iter(widths.items()))
+    for selector, width in widths.items():
+        assert abs(width - ref) <= TOL_PX, (
+            f"@1280px {selector} is {width:.1f}px but {ref_selector} is "
+            f"{ref:.1f}px — the columns must match the RAG page (±{TOL_PX}px)"
         )
-        _assert_width(wide, ".chat-shell", WIDE_PX, "chat @ 1920px")
-        _assert_centered(wide, ".chat-shell", 1920, "chat @ 1920px")
-    finally:
-        wide.close()
 
-    base = browser.new_page(viewport=BASE_VIEWPORT)
-    try:
-        login(base, app_url, next="/")  # phase 79: the chips need a session
-        base.locator("#suggestions .suggestion-chip").first.wait_for(
-            state="visible", timeout=10_000
+    # --- 1920×1080: equal AND each the 72rem container (≈1152px) ------
+    widths = _measure_shells(browser, app_url, VIEWPORT_1920)
+    ref_selector, ref = next(iter(widths.items()))
+    for selector, width in widths.items():
+        assert abs(width - ref) <= TOL_PX, (
+            f"@1920px {selector} is {width:.1f}px but {ref_selector} is "
+            f"{ref:.1f}px — the columns must match the RAG page (±{TOL_PX}px)"
+        )
+        assert abs(width - CONTAINER_PX) <= TOL_PX, (
+            f"@1920px {selector} is {width:.1f}px, want "
+            f"{CONTAINER_PX}px (the 72rem container) ±{TOL_PX}px"
         )
-        _assert_width(base, ".chat-shell", BASE_PX, "chat @ 1280px")
-        _assert_centered(base, ".chat-shell", 1280, "chat @ 1280px")
-    finally:
-        base.close()
 
 
 # ---------------------------------------------------------------------------
-# 2. Document viewer: .doc-md (and its .doc-summary panel) at both
-#    widths — the owner-expanded surface
+# 2. The token's consumers at 1920×1080: the modal (unchanged, D2), the
+#    shared page, and the standalone document page
 # ---------------------------------------------------------------------------
 
 
-def test_document_column_wide_vs_base(
+def test_reader_columns_wide(
     browser: Browser, app_url: str, mock_llm: int, db_ready: None
 ) -> None:
-    """A seeded md document (with a summary) renders .doc-md at 1472px
-    at 1920 and 736px at 1280 — and the adjacent .doc-summary panel
-    matches the column at 1920 (.doc-summary:has(+ .doc-md))."""
+    """At 1920×1080: the same-page document MODAL is untouched (D2 —
+    the panel is still ~1100px and IT binds the ``.doc-md`` inside,
+    ~1058px, not 1152); ``/shared/<token>``'s ``.shared-shell`` is
+    ≈1152px; the standalone ``document.html`` page's ``.doc-md`` is
+    ≈1112px (the 72rem container's inner content)."""
     _reset_db(mock_llm, seed=True)
     _seed_summary_doc()
 
-    wide = browser.new_page(viewport=WIDE_VIEWPORT)
+    page = browser.new_page(viewport=VIEWPORT_1920)
     try:
-        login(wide, app_url, next="/")  # phase 79: the viewer content is gated
-        wide.goto(app_url + FIXTURE_DOC_URL)
-        expect(wide.locator("#doc-title")).to_have_text(FIXTURE_TITLE, timeout=15_000)
-        expect(wide.locator("#doc-content .doc-md")).to_be_visible(timeout=15_000)
-        expect(
-            wide.locator(".doc-summary:has(+ .doc-md)")
-        ).to_have_count(1, timeout=15_000)
-        _assert_width(wide, "#doc-content .doc-md", WIDE_PX, "document @ 1920px")
+        # (a) the same-page modal — the 1100px panel stays its effective
+        # ceiling (D2: pin the PANEL, not the 1152 the column would be).
+        login(page, app_url, next="/sources.html")
+        page.locator("#folders-tbody .folder-link").first.wait_for(
+            state="visible", timeout=15_000
+        )
+        _drill(page, FIXTURE_SOURCE, "notes")
+        row = page.locator("#docs-tbody tr", has_text="wide-column-fixture.md")
+        expect(row).to_have_count(1)
+        row.locator("td:nth-child(2) a.doc-link").click()
+        expect(page.locator(".doc-modal")).to_be_visible()
+        expect(page.locator("#doc-modal-title")).to_have_text(FIXTURE_TITLE)
+        _assert_width(page, "#doc-modal-panel", MODAL_PANEL_PX, "modal panel @ 1920px")
         _assert_width(
-            wide, ".doc-summary:has(+ .doc-md)", WIDE_PX, "summary panel @ 1920px"
+            page,
+            "#doc-modal-content .doc-md",
+            DOC_MD_MODAL_PX,
+            "modal .doc-md @ 1920px",
         )
-    finally:
-        wide.close()
 
-    base = browser.new_page(viewport=BASE_VIEWPORT)
-    try:
-        login(base, app_url, next="/")  # phase 79: the viewer content is gated
-        base.goto(app_url + FIXTURE_DOC_URL)
-        expect(base.locator("#doc-title")).to_have_text(FIXTURE_TITLE, timeout=15_000)
-        expect(base.locator("#doc-content .doc-md")).to_be_visible(timeout=15_000)
-        _assert_width(base, "#doc-content .doc-md", BASE_PX, "document @ 1280px")
+        # (b) the standalone document page: the 72rem container's inner
+        # content (1152 − 2×1.25rem gutters).
+        page.goto(app_url + FIXTURE_DOC_URL)
+        expect(page.locator("#doc-title")).to_have_text(FIXTURE_TITLE, timeout=15_000)
+        expect(page.locator("#doc-content .doc-md")).to_be_visible(timeout=15_000)
+        _assert_width(
+            page,
+            "#doc-content .doc-md",
+            DOC_MD_STANDALONE_PX,
+            "standalone .doc-md @ 1920px",
+        )
+
+        # (c) the shared page: .shared-shell at the full 72rem container.
+        page.goto(app_url + "/")
+        q = "How is my Kubernetes cluster set up? (wide-column)"
+        _ask(page, q)
+        cookies = _admin_cookies(page)
+        saved_row = _wait_saved_row(app_url, cookies, _auto_title(q))
+        chat_id: str = saved_row["id"]
+        anon_ctx = None
+        try:
+            # Public since phase 55 — the share endpoint takes no session.
+            r = httpx.post(f"{app_url}/api/chats/{chat_id}/share", timeout=10)
+            assert r.status_code == 200
+            share_url = r.json()["share_url"]
+            assert SHARE_URL_RE.fullmatch(share_url), f"bad share_url shape: {share_url}"
+
+            anon_ctx = browser.new_context(viewport=VIEWPORT_1920)
+            anon = anon_ctx.new_page()
+            anon.set_default_timeout(30_000)
+            anon.goto(app_url + share_url)
+            expect(anon.locator("#shared-title")).to_have_text(
+                _auto_title(q), timeout=15_000
+            )
+            expect(anon.locator(".msg.brain .bubble")).to_contain_text(
+                MOCK_ANSWER_MARKER, timeout=30_000
+            )
+            _assert_width(anon, ".shared-shell", CONTAINER_PX, "shared @ 1920px")
+            _assert_centered(anon, ".shared-shell", 1920, "shared @ 1920px")
+        finally:
+            if anon_ctx is not None:
+                anon_ctx.close()
+            _delete_chat(app_url, cookies, chat_id)
     finally:
-        base.close()
+        page.close()
 
 
 # ---------------------------------------------------------------------------
-# 3. Shared page: .shared-shell at 1472px for a guest at 1920
-# ---------------------------------------------------------------------------
-
-
-def test_shared_column_wide(
-    page: Page,
-    browser: Browser,
-    app_url: str,
-    mock_llm: int,
-    db_ready: None,
-) -> None:
-    """A real auto-saved conversation, shared by token, renders its
-    .shared-shell at 1472px (±4px) at 1920 in a FRESH anonymous
-    context (no cookies — the guest's only credential is the token)."""
-    _reset_db(mock_llm, seed=True)
-    page.set_default_timeout(30_000)
-
-    login(page, app_url, next="/")
-    expect(page).to_have_url(app_url + "/", timeout=30_000)
-
-    q = "How is my Kubernetes cluster set up? (wide-column)"
-    _ask(page, q)
-
-    cookies = _admin_cookies(page)
-    row = _wait_saved_row(app_url, cookies, _auto_title(q))
-    chat_id: str = row["id"]
-    anon_ctx = None
-    try:
-        # Public since phase 55 — the share endpoint takes no session.
-        r = httpx.post(f"{app_url}/api/chats/{chat_id}/share", timeout=10)
-        assert r.status_code == 200
-        share_url = r.json()["share_url"]
-        assert SHARE_URL_RE.fullmatch(share_url), f"bad share_url shape: {share_url}"
-
-        anon_ctx = browser.new_context(viewport=WIDE_VIEWPORT)
-        anon = anon_ctx.new_page()
-        anon.set_default_timeout(30_000)
-        anon.goto(app_url + share_url)
-        expect(anon.locator("#shared-title")).to_have_text(
-            _auto_title(q), timeout=15_000
-        )
-        expect(anon.locator(".msg.brain .bubble")).to_contain_text(
-            MOCK_ANSWER_MARKER, timeout=30_000
-        )
-        _assert_width(anon, ".shared-shell", WIDE_PX, "shared @ 1920px")
-        _assert_centered(anon, ".shared-shell", 1920, "shared @ 1920px")
-    finally:
-        if anon_ctx is not None:
-            anon_ctx.close()
-        _delete_chat(app_url, cookies, chat_id)
-
-
-# ---------------------------------------------------------------------------
-# 4. Below the breakpoint: 360px and 900px are byte-for-byte the old
-#    rules — no overflow, no leaked wide column
+# 3. Below the container cap: full-width as today — 360px overflow-free,
+#    900px chat == tuning == theme (the cap never bound below 72rem)
 # ---------------------------------------------------------------------------
 
 
 def test_narrow_unchanged(
     browser: Browser, app_url: str, db_ready: None
 ) -> None:
-    """The min-width:1500px override must not leak below the
-    breakpoint: at 360px no horizontal overflow and the shell is the
-    existing mobile rule — full-bleed at the viewport width (the shell
-    IS its .container, so the 0.9rem mobile gutters sit in its own
-    padding, inside the measured box); at 900px the shell holds the
-    46rem base (736px — a leaked 92rem rule would pin it to the 860px
-    content box instead, so 736px is the discriminator)."""
-    phone = browser.new_page(viewport={"width": 360, "height": 740})
+    """The mobile/tablet layouts are UNCHANGED (D3): at 360×800 no
+    horizontal overflow and ``.chat-shell`` is the viewport width
+    (full-bleed — the shell IS its .container, so the mobile gutters sit
+    in its padding, inside the measured box); at 900×600 the
+    chat/tuning/theme shells are ALL 900px wide, equal to each other
+    (the cap never bound below 72rem anyway)."""
+    phone = browser.new_page(viewport={"width": 360, "height": 800})
     try:
-        login(phone, app_url, next="/")  # phase 79: the chips need a session
-        phone.locator("#suggestions .suggestion-chip").first.wait_for(
-            state="visible", timeout=10_000
-        )
+        login(phone, app_url, next="/")
+        phone.locator(".chat-shell").wait_for(state="visible", timeout=10_000)
         _assert_no_doc_overflow(phone, "chat @ 360px")
         _assert_width(phone, ".chat-shell", 360, "chat @ 360px")
     finally:
         phone.close()
 
-    tablet = browser.new_page(viewport={"width": 900, "height": 800})
+    tablet = browser.new_page(viewport={"width": 900, "height": 600})
     try:
-        login(tablet, app_url, next="/")  # phase 79: the chips need a session
-        tablet.locator("#suggestions .suggestion-chip").first.wait_for(
-            state="visible", timeout=10_000
-        )
+        login(tablet, app_url, next="/")
+        tablet.locator(".chat-shell").wait_for(state="visible", timeout=10_000)
         _assert_no_doc_overflow(tablet, "chat @ 900px")
-        _assert_width(tablet, ".chat-shell", BASE_PX, "chat @ 900px")
-        _assert_centered(tablet, ".chat-shell", 900, "chat @ 900px")
+        widths = {".chat-shell": _box_width(tablet, ".chat-shell", "chat @ 900px")}
+        for path, selector in (
+            ("/tuning.html", ".tuning-shell"),
+            ("/theme.html", ".theme-shell"),
+        ):
+            tablet.goto(app_url + path)
+            tablet.locator(selector).wait_for(state="visible", timeout=10_000)
+            widths[selector] = _box_width(tablet, selector, f"{path} @ 900px")
+        ref_selector, ref = next(iter(widths.items()))
+        for selector, width in widths.items():
+            assert abs(width - ref) <= TOL_PX, (
+                f"@900px {selector} is {width:.1f}px but {ref_selector} is "
+                f"{ref:.1f}px — the cap must not bind below the container cap"
+            )
+            assert abs(width - 900) <= TOL_PX, (
+                f"@900px {selector} is {width:.1f}px, want the full 900px "
+                f"viewport width ±{TOL_PX}px"
+            )
     finally:
         tablet.close()