**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).
- task 01: relocate the .chat-actions row (New chat + Share, comments byte-identical with a Phase 65 note) from the top of the column to the bottom of .chat-shell, directly above the composer
- task 02 (owner-locked A1): wrap the row + #composer in ONE sticky .chat-bottom unit (position: sticky; bottom: env(safe-area-inset-bottom, 0), no z-index) — the pills stay at the bottom of the screen at every scroll position and settle into flow above the footer
- task 03 (owner-locked A2): right-align the bottom row to the column's right edge (justify-content: flex-end), mirroring the right-aligned Save-as-doc corner; the five action pills share one 44px / 999px-pill geometry
- task 04: dedicated Playwright suite tests/e2e/test_bottom_chat_actions.py (resting geometry, the A1 pin across the sticky range, A2 alignment + DOM order + mobile stack + 360px overflow bound + 44px touch targets, New chat / Share click-through) — green in isolation
- task 05: regression matrix green in isolation (pinned_composer 4, save_share_ux 5, chat_persistence 4, share_chat 4, chat_history 5, smoke 3); full gate green — unit + integration pass, app/ coverage 99% (>90%), ruff + pyright clean
Phase 52's first pass shipped `position: sticky; bottom` on `.composer` and
called the phase done, but the owner's requirement — "the chat message-input
textarea should be at the bottom of the screen" — still failed in the browser:
on an empty/short chat the input rested just under the empty state (~57% of
the viewport) with a dead band down to the footer.
`position: sticky` can only pull a box UP toward the scrollport's bottom edge;
it can never push a box DOWN to meet it, so on a page that does not overflow
it is a no-op. The old story suite only exercised an overflowing conversation
(one test even asserted the buggy resting position as expected), which is why
the half-fix passed.
- `.messages { flex: 1 1 auto }` — absorbs a short page's free space so the
composer's resting in-flow position is the bottom of the full-height column
(body min-height:100dvh -> .app-main flex:1 -> .chat-shell flex:1); basis
stays `auto`, no height cap, no overflow — the document stays the scroller
- `.composer { bottom: env(safe-area-inset-bottom, 0) }` — the explicit 0
fallback replaces the env()-only offset, which degraded to `auto` (no pin)
wherever env() is unsupported
- E2E: `test_empty_chat_composer_sits_in_normal_flow` ->
`..._at_the_screen_bottom` (chrome-only band below the resting composer);
the phone suite now checks the resting position as well as the pinned one
- Unit pins: the flex-grow half and the full-height column are pinned, so the
fix cannot silently regress to sticky-only
Still CSS-only — no DOM change, no JS, no new scroll call site (phase 42
never-auto-scroll contract intact), no z-index.
Verified: 1019 unit/integration tests pass (app/ coverage 99%), ruff and
pyright clean; tests/e2e/test_pinned_composer.py green in isolation (4), plus
the stop/autoscroll/persistence/mobile-nav suites and 14 layout/scroll
neighbours green in isolation.
ducoterra