Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@docs/tasks/archive/2026/05/20260508-sheets-comments-todo.md`:
- Line 15: The heading "### Task 1: Comment data model & pure helpers (sheets
package)" is an H3 with no preceding H2 which triggers markdownlint MD001; fix
it by either promoting this line to an H2 (change "###" to "##") or by inserting
an appropriate H2 section above it (e.g., "## Tasks" or "## Sheet tasks") so the
heading hierarchy is contiguous and markdownlint passes.

In
`@packages/frontend/src/app/spreadsheet/components/comments/CommentComposer.tsx`:
- Around line 39-43: The submit function currently validates using trimmed but
calls onSubmit with the untrimmed body, causing stored comments to include
surrounding whitespace; change the submit handler (submit) to pass trimmed to
onSubmit (or trim inside onSubmit) and then clear body via setBody(""), ensuring
the same trimmed value used for the empty-guard/button-disabled check is what
gets submitted (identify submit, onSubmit, body, trimmed, and setBody in
CommentComposer.tsx).

In
`@packages/frontend/src/app/spreadsheet/components/comments/CommentPopover.tsx`:
- Around line 88-91: The expression computing canEditOrDelete assumes
currentUser is non-null and can throw if currentUser is null; update the logic
in the canEditOrDelete calculation to guard access to currentUser (e.g., use a
null-check or optional chaining on currentUser.userId) so it only compares IDs
when currentUser exists, and ensure any early-return or fallback provides a
clear debug-friendly message/context where appropriate; refer to
canEditOrDelete, currentUser, isReadOnly, c.author.userId and editingCommentId
to locate and fix the check.

In
`@packages/frontend/src/app/spreadsheet/components/comments/CommentSidePanel.tsx`:
- Around line 42-67: The tab buttons in CommentSidePanel.tsx use aria-pressed
(toggle semantics) instead of ARIA tabs; change the container <div> to
role="tablist", change each tab button to role="tab" and replace aria-pressed
with aria-selected={tab === "open"/"resolved"} (remove aria-pressed), and add
role="tabpanel" to the content <ul> that renders the tab panels; also implement
keyboard handling (onKeyDown either on the tab buttons or the tablist) to
support Left/Right (and Home/End) to move focus and call setTab appropriately,
ensuring the active tab receives focus when selected so screen readers and
keyboard users get correct tab semantics (reference symbols: CommentSidePanel,
tab state variable, setTab, openCount, resolvedCount, and the <ul> panel).

In `@packages/frontend/src/app/spreadsheet/sheet-view.tsx`:
- Around line 1242-1258: The computed commentPopoverPosition is only updated
during React renders, so when the grid scrolls the popover becomes stale; fix
this by making the position reactive to sheet viewport changes: move the
computation out of a plain IIFE and into React state (e.g.,
commentPopoverPosition state or a render-key) and add a useEffect that
subscribes to the sheet viewport/scroll change events on sheetRef.current (use
the sheet API methods that emit viewport/scroll events or listen to native
scroll if needed) and recomputes/sets the position using getGridViewportRect()
and getCellRect(activeCellForComment) whenever the sheet viewport changes or
when activeCellForComment changes; also clean up the event listener in the
effect cleanup to avoid leaks.
- Around line 809-816: handleCommentResolve currently closes the cell comment
popover unconditionally after resolving any thread; instead, after calling
storeRef.current?.setThreadResolved(threadId, true, commentAuthor) use the store
to check whether that thread's cell still has any unresolved threads (e.g.
retrieve the thread via storeRef.current?.getThread(threadId) to get its cell
id, then query remaining threads for that cell or a hasUnresolvedThreads(cellId)
helper) and only call setCommentPopoverOpen(false) when no unresolved threads
remain; update handleCommentResolve to perform this conditional close while
preserving the existing commentAuthor and storeRef usage.

In `@packages/frontend/src/app/spreadsheet/yorkie-store.ts`:
- Around line 1221-1239: addThread currently ignores anchor.tabId and will
persist a thread into root.sheets[this.tabId] even if anchor.tabId differs;
update addThread to validate that anchor.tabId === this.tabId (or return/reject)
before creating/applying the thread. Specifically, in the addThread function
check anchor.tabId against this.tabId and throw or return an error (or no-op)
when they differ, ensuring applyAddThread is only called on the matching sheet;
also update callers/tests if they expect a different behavior.
- Around line 1287-1307: listThreads currently returns live objects from
ws.comments allowing external mutation; modify listThreads (in yorkie-store.ts)
to materialize and return detached snapshots instead of the raw live objects —
for each thread from Object.values(ws?.comments ?? {}), produce a shallow/deep
copy (e.g., clone top-level properties, clone anchor object and clone comments
array/objects) so callers get immutable snapshots consistent with other getters
in this class; ensure filtering logic (opts?.cellAnchor and opts?.resolved) runs
against the clones or clone after filtering and return the array of cloned
Thread objects.

In `@packages/frontend/src/components/sheet-context-menu.tsx`:
- Around line 206-208: The UI currently hardcodes the Option symbol (⌥)
regardless of platform; update the span in the SheetContextMenu component (where
navigator.platform.startsWith("Mac") is used) to render "⌥" for Mac and "Alt"
for non-Mac, so the text becomes either "⌘+⌥+M" on Mac or "Ctrl+Alt+M" on
Windows/Linux; modify the expression in that span to compute both the modifier
prefix (navigator.platform.startsWith("Mac") ? "⌘" : "Ctrl") and the middle
modifier (navigator.platform.startsWith("Mac") ? "⌥" : "Alt") and concatenate
them appropriately.

In `@packages/sheets/src/store/memory.ts`:
- Around line 553-629: The store is returning references to the internal
Thread/Comment objects (e.g., from addThread, addReply, listThreads) so callers
can mutate MemStore state; instead, return deep-cloned snapshots. After
creating/updating a thread with createThreadHelper, addReplyHelper,
editCommentHelper, deleteCommentHelper, setThreadResolvedHelper, keep the
internal object as-is in this.threads but return a deep clone to callers (use
structuredClone or a reusable cloneThread/cloneComment helper). Ensure
listThreads maps the stored threads to clones before returning and that addReply
returns a clone of the newly appended comment rather than the internal
reference.

In `@packages/sheets/src/view/render-comments.ts`:
- Around line 4-6: JSDoc is out of sync with the MARKER_SIZE constant (docs say
"7x7" but MARKER_SIZE = 9); update the JSDoc on the comment marker function (the
block above the marker drawing logic that references MARKER_SIZE) so it
accurately describes the marker size (e.g., "9x9" or reference MARKER_SIZE) and
its placement, or alternatively change MARKER_SIZE to 7 if the intended marker
is truly 7x7—ensure the JSDoc and the MARKER_SIZE constant (and any calculations
using it) are consistent.

---

Outside diff comments:
In `@packages/sheets/src/view/worksheet.ts`:
- Around line 5041-5074: After awaiting sheet.getStore().listThreads() you must
re-check the render staleness/version guard (the same guard used after
fetchGrid()) before calling buildOpenThreadKeySet/gridCanvas.render; if the
sheet/version has changed or a newer render has won, bail out to avoid painting
stale comment markers. Locate the async path where listThreads() is awaited and
add the same conditional check (using the existing render token/version or sheet
identity check used elsewhere) and return early when stale, then proceed to call
buildOpenThreadKeySet and gridCanvas.render only when current.

---

Nitpick comments:
In `@docs/design/sheets/comments.md`:
- Around line 54-75: The fenced code blocks in the documentation (the directory
tree starting with "packages/sheets/src/comment/" and the component tree under
"packages/frontend/src/app/spreadsheet/") lack language identifiers, which
breaks rendering and highlighting; update those fenced blocks to include an
appropriate language tag such as "text" (e.g., change ``` to ```text) for the
directory/component trees so the tree structures render correctly in the docs
(apply to the block showing packages/sheets/src/comment/ and the block showing
the SpreadsheetPage/component tree around lines 278–285).

In `@packages/frontend/tests/app/spreadsheet/comments-concurrency.test.ts`:
- Around line 149-188: Add a new test mirroring the "concurrent resolve" case
but for reopen: use createTwoUserSpreadsheet to create a thread via
ctx.storeA.addThread, sync, then perform concurrent reopen calls with
ctx.storeA.setThreadResolved(thread.id, false, authorA) and
ctx.storeB.setThreadResolved(thread.id, false, authorB) (or vice versa) inside
Promise.all, await ctx.sync(), then assert both ctx.storeA.listThreads() and
ctx.storeB.listThreads() return the same single thread and that its resolved
flag is false; place it alongside the existing concurrent-resolve test and
ensure cleanup via ctx.cleanup().

In `@packages/frontend/tests/app/spreadsheet/yorkie-comments-orphan.test.ts`:
- Around line 16-59: Add a test that verifies deleteThreadsForAxis preserves
threads whose anchor.kind !== "sheet-cell": create a workspace object with
comments containing a normal cell thread (use thread('t1', ...)) and a second
thread object (e.g., t2) copied from thread('t2', ...) but with anchor: { kind:
'sheet-range', tabId: 't' } cast to Thread; call deleteThreadsForAxis(ws, 'row',
new Set(['r1'])); assert the cell thread (t1) was removed and that the
non-sheet-cell thread (t2) still exists. Target the test file where other cases
live and reference deleteThreadsForAxis, Thread, thread, and anchor to locate
the code under test.