diff --git a/web/src/lib/components/CommentEditor.svelte b/web/src/lib/components/CommentEditor.svelte
new file mode 100644
index 00000000..c505b7c4
--- /dev/null
+++ b/web/src/lib/components/CommentEditor.svelte
@@ -0,0 +1,299 @@
+<script lang="ts">
+	/**
+	 * Lean WYSIWYG comment editor (TASK-1664 / PLAN-1662). A small, purpose-
+	 * built Tiptap instance — NOT the heavy block editor (Editor.svelte). It
+	 * reuses the shared attachment pipeline (AttachmentUpload plugin +
+	 * AttachmentImage/AttachmentChip nodes) and tiptap-markdown so pasted/
+	 * dropped images show as inline thumbnails while composing, yet the value
+	 * round-trips to plain markdown — comment.body stays markdown, so display,
+	 * search, and the orphan-GC are untouched.
+	 *
+	 * Deliberately excludes tables, task lists, slash commands, the block drag
+	 * handle, the import-from-URL modal, and collaboration — comments don't
+	 * need a document editor.
+	 *
+	 * Used for the new-comment composer, the reply box, and (TASK-1665) inline
+	 * edit mode.
+	 */
+	import { onMount, onDestroy } from 'svelte';
+	import { Editor } from '@tiptap/core';
+	import StarterKit from '@tiptap/starter-kit';
+	import Link from '@tiptap/extension-link';
+	import Placeholder from '@tiptap/extension-placeholder';
+	import { Markdown } from 'tiptap-markdown';
+	import { api } from '$lib/api/client';
+	import { unescapeDocLinks } from '$lib/utils/markdown';
+	import { AttachmentImage } from './editor/attachment-image';
+	import { AttachmentChip } from './editor/attachment-chip';
+	import { AttachmentUpload } from './editor/attachment-upload';
+
+	interface Props {
+		/** Initial markdown body. Parsed as markdown on mount. */
+		content?: string;
+		placeholder?: string;
+		/** Workspace slug — required for attachment upload + image URLs. */
+		wsSlug: string;
+		/** Label for the submit button (e.g. "Comment", "Reply", "Save"). */
+		submitLabel?: string;
+		/** External busy flag (network in flight in the host). */
+		submitting?: boolean;
+		autofocus?: boolean;
+		/** Show a Cancel button + enable Esc-to-cancel (reply / edit mode). */
+		onCancel?: () => void;
+		/**
+		 * Called with the current markdown when the user submits. May return a
+		 * promise; on resolution the editor clears (composer behaviour). If it
+		 * throws, the draft is kept so the user can retry.
+		 */
+		onSubmit: (markdown: string) => void | Promise<void>;
+	}
+
+	let {
+		content = '',
+		placeholder = 'Write a comment…',
+		wsSlug,
+		submitLabel = 'Comment',
+		submitting = false,
+		autofocus = false,
+		onCancel,
+		onSubmit
+	}: Props = $props();
+
+	let element: HTMLDivElement | undefined = $state();
+	let editor: Editor | undefined;
+	let pendingUploads = $state(0);
+	let empty = $state(true);
+	let saving = $state(false);
+
+	let busy = $derived(submitting || saving || pendingUploads > 0);
+
+	function currentMarkdown(): string {
+		if (!editor) return '';
+		return unescapeDocLinks((editor.storage as any).markdown?.getMarkdown?.() ?? '').trim();
+	}
+
+	async function doSubmit() {
+		if (busy || !editor) return;
+		const md = currentMarkdown();
+		if (md === '') return;
+		saving = true;
+		try {
+			await onSubmit(md);
+			// Composer behaviour: clear on success. In edit/reply mode the host
+			// unmounts this component, so the clear is harmless there.
+			editor.commands.clearContent();
+		} catch {
+			// Keep the draft so the user can retry.
+		} finally {
+			saving = false;
+		}
+	}
+
+	const attachmentUrl = (uuid: string, variant?: 'thumb-sm' | 'thumb-md' | 'original') =>
+		wsSlug ? api.attachments.downloadUrl(wsSlug, uuid, variant) : `pad-attachment:${uuid}`;
+
+	onMount(() => {
+		if (!element) return;
+
+		editor = new Editor({
+			element,
+			content,
+			autofocus: autofocus ? 'end' : false,
+			extensions: [
+				StarterKit.configure({ link: false }),
+				Link.configure({ openOnClick: false, autolink: true, linkOnPaste: true }),
+				Placeholder.configure({ placeholder }),
+				Markdown.configure({ html: true, transformPastedText: true, transformCopiedText: true }),
+				AttachmentImage.configure({
+					getDownloadUrl: attachmentUrl,
+					workspaceSlug: wsSlug,
+					// Rotate/crop stays disabled in comments — keep it lean.
+					supportedFormats: [] as string[],
+					transform: async () => {
+						throw new Error('Image transforms are not available in comments.');
+					}
+				}),
+				AttachmentChip.configure({ getDownloadUrl: attachmentUrl, workspaceSlug: wsSlug }),
+				AttachmentUpload.configure({
+					// Wrap upload so the host can track in-flight uploads and gate
+					// submit — the plugin doesn't expose its placeholder count.
+					upload: async (file) => {
+						if (!wsSlug) {
+							throw new Error('No workspace context — open a comment inside a workspace to attach files.');
+						}
+						pendingUploads += 1;
+						try {
+							return await api.attachments.upload(wsSlug, file);
+						} finally {
+							pendingUploads -= 1;
+						}
+					},
+					onError: (filename, message) => {
+						console.error(`[comment attachment] ${filename}: ${message}`);
+						if (typeof window !== 'undefined' && typeof window.alert === 'function') {
+							window.alert(`Couldn't upload ${filename}: ${message}`);
+						}
+					}
+				})
+			],
+			editorProps: {
+				handleKeyDown: (_view, event) => {
+					if ((event.metaKey || event.ctrlKey) && event.key === 'Enter') {
+						event.preventDefault();
+						doSubmit();
+						return true;
+					}
+					if (event.key === 'Escape' && onCancel) {
+						event.preventDefault();
+						onCancel();
+						return true;
+					}
+					return false;
+				}
+			},
+			onUpdate: ({ editor: e }) => {
+				empty = e.isEmpty;
+			}
+		});
+		empty = editor.isEmpty;
+	});
+
+	onDestroy(() => {
+		editor?.destroy();
+	});
+</script>
+
+<div class="comment-editor" class:busy>
+	<div class="ce-surface prose" bind:this={element}></div>
+	<div class="ce-actions">
+		<span class="ce-hint">
+			{#if pendingUploads > 0}
+				Uploading {pendingUploads} file{pendingUploads === 1 ? '' : 's'}…
+			{:else}
+				{onCancel ? 'Ctrl+Enter to submit · Esc to cancel' : 'Ctrl+Enter to submit · paste or drop an image'}
+			{/if}
+		</span>
+		<div class="ce-buttons">
+			{#if onCancel}
+				<button class="ce-cancel" type="button" onclick={onCancel} disabled={saving}>Cancel</button>
+			{/if}
+			<button class="ce-submit" type="button" onclick={doSubmit} disabled={busy || empty}>
+				{saving || submitting ? 'Posting…' : submitLabel}
+			</button>
+		</div>
+	</div>
+</div>
+
+<style>
+	.comment-editor {
+		display: flex;
+		flex-direction: column;
+		gap: var(--space-2);
+	}
+
+	.ce-surface {
+		width: 100%;
+		min-height: 60px;
+		max-height: 360px;
+		overflow-y: auto;
+		padding: var(--space-2) var(--space-3);
+		background: var(--bg-secondary);
+		border: 1px solid var(--border);
+		border-radius: var(--radius);
+		color: var(--text-primary);
+		font-size: 0.9em;
+		line-height: 1.5;
+	}
+
+	.ce-surface :global(.ProseMirror) {
+		outline: none;
+		min-height: 44px;
+	}
+
+	/* Placeholder (Placeholder extension renders a data-attr on the empty doc). */
+	.ce-surface :global(.ProseMirror p.is-editor-empty:first-child::before) {
+		content: attr(data-placeholder);
+		color: var(--text-muted);
+		float: left;
+		height: 0;
+		pointer-events: none;
+	}
+
+	.ce-surface :global(p:first-child) {
+		margin-top: 0;
+	}
+	.ce-surface :global(p:last-child) {
+		margin-bottom: 0;
+	}
+
+	/* Inline image previews render as compact thumbnails while composing,
+	   matching the rendered-comment display. */
+	.ce-surface :global(img[data-attachment-id]) {
+		max-width: 280px;
+		max-height: 180px;
+		width: auto;
+		height: auto;
+		object-fit: contain;
+		border: 1px solid var(--border);
+		border-radius: var(--radius-sm);
+	}
+
+	.ce-surface:focus-within {
+		border-color: var(--accent-blue);
+	}
+
+	.comment-editor.busy .ce-surface {
+		opacity: 0.85;
+	}
+
+	.ce-actions {
+		display: flex;
+		align-items: center;
+		justify-content: space-between;
+		gap: var(--space-2);
+	}
+
+	.ce-hint {
+		font-size: 0.75em;
+		color: var(--text-muted);
+	}
+
+	.ce-buttons {
+		display: flex;
+		gap: var(--space-2);
+	}
+
+	.ce-submit {
+		padding: var(--space-1) var(--space-4);
+		background: var(--accent-blue);
+		border: none;
+		border-radius: var(--radius);
+		color: #fff;
+		font-size: 0.85em;
+		font-weight: 500;
+		cursor: pointer;
+	}
+
+	.ce-submit:hover:not(:disabled) {
+		filter: brightness(1.1);
+	}
+
+	.ce-submit:disabled {
+		opacity: 0.5;
+		cursor: not-allowed;
+	}
+
+	.ce-cancel {
+		padding: var(--space-1) var(--space-3);
+		background: transparent;
+		border: 1px solid var(--border);
+		border-radius: var(--radius);
+		color: var(--text-secondary);
+		font-size: 0.85em;
+		cursor: pointer;
+	}
+
+	.ce-cancel:hover:not(:disabled) {
+		background: var(--bg-tertiary);
+	}
+</style>
diff --git a/web/src/lib/components/timeline/ItemTimeline.svelte b/web/src/lib/components/timeline/ItemTimeline.svelte
index 86517801..6c47884a 100644
--- a/web/src/lib/components/timeline/ItemTimeline.svelte
+++ b/web/src/lib/components/timeline/ItemTimeline.svelte
@@ -8,16 +8,11 @@
 	import TimelineCommentCard from './TimelineCommentCard.svelte';
 	import TimelineActivityCard from './TimelineActivityCard.svelte';
 	import TimelineVersionCard from './TimelineVersionCard.svelte';
-	import {
-		filesFromPaste,
-		filesFromDrop,
-		isFileDrag,
-		uploadIntoTextarea,
-		attachmentRefsIn
-	} from '$lib/utils/commentAttachments';
+	import { attachmentRefsIn } from '$lib/utils/commentAttachments';
 	import { fetchAttachmentMetadata } from '$lib/components/editor/attachment-metadata';
 	import { attachmentDownloadUrl, type AttachmentMeta } from '$lib/markdown/attachments';
 	import Lightbox, { type LightboxImage } from '$lib/components/common/Lightbox.svelte';
+	import CommentEditor from '$lib/components/CommentEditor.svelte';
 
 	interface Props {
 		wsSlug: string;
@@ -51,13 +46,6 @@
 	let loading: boolean = $state(false);
 	let loadingMore: boolean = $state(false);
 	let error: string = $state('');
-	let newBody: string = $state('');
-
-	// Comment composer attachment state (IDEA-1650). pendingUploads gates
-	// submit while a paste/drop upload is in flight; composeTextarea is the
-	// caret anchor the upload helper splices markdown into.
-	let pendingUploads: number = $state(0);
-	let composeTextarea: HTMLTextAreaElement | undefined = $state();
 
 	// Resolver for `pad-attachment:UUID` references in comment bodies.
 	// Metadata (MIME + size) is fetched lazily per UUID via a HEAD probe and
@@ -98,29 +86,6 @@
 		}
 	});
 
-	function startComposeUploads(files: File[]) {
-		if (!composeTextarea) return;
-		uploadIntoTextarea(files, composeTextarea, wsSlug, {
-			getValue: () => newBody,
-			setValue: (v) => {
-				newBody = v;
-			},
-			onPendingDelta: (d) => {
-				pendingUploads += d;
-			},
-			onError: (msg) => {
-				error = msg;
-			}
-		});
-	}
-
-	function handleComposePaste(e: ClipboardEvent) {
-		const files = filesFromPaste(e);
-		if (files.length === 0) return;
-		e.preventDefault();
-		startComposeUploads(files);
-	}
-
 	// Lightbox state (IDEA-1660). Set when a thumbnail is activated; cleared
 	// on close. Null = closed, so the host remounts fresh on each open.
 	let lightbox: { images: LightboxImage[]; index: number } | null = $state(null);
@@ -194,20 +159,6 @@
 		});
 	});
 
-	function handleComposeDragOver(e: DragEvent) {
-		// Cancel only file drags so the browser delivers the drop here
-		// instead of navigating; text drag-drop within the textarea is left
-		// to default handling.
-		if (isFileDrag(e)) e.preventDefault();
-	}
-
-	function handleComposeDrop(e: DragEvent) {
-		const files = filesFromDrop(e);
-		if (files.length === 0) return;
-		e.preventDefault();
-		startComposeUploads(files);
-	}
-
 	// Current user ID for reaction toggle — read from the global auth store.
 	let currentUserId = $derived(authStore.userId);
 
@@ -311,31 +262,26 @@
 
 	let submitting: boolean = $state(false);
 
-	async function submitComment() {
-		if (!newBody.trim() || submitting || pendingUploads > 0) return;
+	// Posts a new comment. Throws on failure so CommentEditor preserves the
+	// draft; clears itself on success.
+	async function submitComment(body: string) {
 		submitting = true;
+		error = '';
 		try {
 			await api.comments.create(wsSlug, itemSlug, {
-				body: newBody.trim(),
+				body,
 				created_by: 'user',
 				source: 'web'
 			});
-			newBody = '';
 			await loadTimeline();
 		} catch (err: any) {
 			error = err?.message ?? 'Failed to post comment';
+			throw err;
 		} finally {
 			submitting = false;
 		}
 	}
 
-	function handleKeydown(e: KeyboardEvent) {
-		if (e.key === 'Enter' && (e.ctrlKey || e.metaKey)) {
-			e.preventDefault();
-			submitComment();
-		}
-	}
-
 	async function handleReply(commentId: string, body: string) {
 		try {
 			await api.comments.reply(wsSlug, commentId, {
@@ -397,32 +343,13 @@
 	     thread but cannot post; the composer is hidden entirely. -->
 	{#if canEdit}
 		<div class="compose">
-			<textarea
-				class="compose-input"
-				bind:this={composeTextarea}
-				placeholder="Write a comment... (paste or drop an image to attach)"
-				bind:value={newBody}
-				onkeydown={handleKeydown}
-				onpaste={handleComposePaste}
-				ondragover={handleComposeDragOver}
-				ondrop={handleComposeDrop}
-				disabled={submitting}
-			></textarea>
-			<div class="compose-actions">
-				<span class="shortcut-hint">
-					{pendingUploads > 0
-						? `Uploading ${pendingUploads} file${pendingUploads === 1 ? '' : 's'}…`
-						: 'Ctrl+Enter to submit'}
-				</span>
-				<button
-					class="submit-btn"
-					type="button"
-					disabled={!newBody.trim() || submitting || pendingUploads > 0}
-					onclick={submitComment}
-				>
-					{submitting ? 'Posting...' : 'Comment'}
-				</button>
-			</div>
+			<CommentEditor
+				{wsSlug}
+				placeholder="Write a comment… (paste or drop an image to attach)"
+				submitLabel="Comment"
+				{submitting}
+				onSubmit={submitComment}
+			/>
 		</div>
 	{/if}
 
@@ -538,65 +465,6 @@
 		gap: var(--space-2);
 	}
 
-	.compose-input {
-		width: 100%;
-		padding: var(--space-2) var(--space-3);
-		background: var(--bg-secondary);
-		border: 1px solid var(--border);
-		border-radius: var(--radius);
-		color: var(--text-primary);
-		font-size: 0.9em;
-		font-family: inherit;
-		line-height: 1.5;
-		resize: vertical;
-		min-height: 60px;
-	}
-
-	.compose-input::placeholder {
-		color: var(--text-muted);
-	}
-
-	.compose-input:focus {
-		outline: none;
-		border-color: var(--accent-blue);
-	}
-
-	.compose-input:disabled {
-		opacity: 0.6;
-	}
-
-	.compose-actions {
-		display: flex;
-		align-items: center;
-		justify-content: flex-end;
-		gap: var(--space-3);
-	}
-
-	.shortcut-hint {
-		font-size: 0.75em;
-		color: var(--text-muted);
-	}
-
-	.submit-btn {
-		padding: var(--space-1) var(--space-4);
-		background: var(--accent-blue);
-		border: none;
-		border-radius: var(--radius);
-		color: #fff;
-		font-size: 0.85em;
-		font-weight: 500;
-		cursor: pointer;
-	}
-
-	.submit-btn:hover:not(:disabled) {
-		filter: brightness(1.1);
-	}
-
-	.submit-btn:disabled {
-		opacity: 0.5;
-		cursor: not-allowed;
-	}
-
 	/* ── Loading / Error ──────────────────────────────────────────────────── */
 
 	.loading {
diff --git a/web/src/lib/components/timeline/TimelineCommentCard.svelte b/web/src/lib/components/timeline/TimelineCommentCard.svelte
index 8786b117..f61b0892 100644
--- a/web/src/lib/components/timeline/TimelineCommentCard.svelte
+++ b/web/src/lib/components/timeline/TimelineCommentCard.svelte
@@ -2,7 +2,7 @@
 	import type { Comment, Item, Reaction } from '$lib/types';
 	import { relativeTime, renderMarkdown } from '$lib/utils/markdown';
 	import type { AttachmentResolver } from '$lib/markdown/attachments';
-	import { filesFromPaste, filesFromDrop, isFileDrag, uploadIntoTextarea } from '$lib/utils/commentAttachments';
+	import CommentEditor from '$lib/components/CommentEditor.svelte';
 	import ReactionPicker from './ReactionPicker.svelte';
 
 	interface Props {
@@ -36,75 +36,22 @@
 	let { comment, wsSlug, username = '', items, currentUserId = '', canEdit = true, attachmentResolver, onDelete, onReply, onReaction, onRemoveReaction }: Props = $props();
 
 	let showReplyForm = $state(false);
-	let replyBody = $state('');
 	let submittingReply = $state(false);
 
-	// Reply-box attachment upload (IDEA-1650). Mirrors the top-level
-	// composer in ItemTimeline; replyPending gates submit while a
-	// paste/drop upload is in flight.
-	let replyTextarea: HTMLTextAreaElement | undefined = $state();
-	let replyPending = $state(0);
-
-	function startReplyUploads(files: File[]) {
-		if (!replyTextarea) return;
-		uploadIntoTextarea(files, replyTextarea, wsSlug, {
-			getValue: () => replyBody,
-			setValue: (v) => {
-				replyBody = v;
-			},
-			onPendingDelta: (d) => {
-				replyPending += d;
-			},
-			onError: (msg) => {
-				if (typeof window !== 'undefined') window.alert(`Couldn't upload: ${msg}`);
-			}
-		});
-	}
-
-	function handleReplyPaste(e: ClipboardEvent) {
-		const files = filesFromPaste(e);
-		if (files.length === 0) return;
-		e.preventDefault();
-		startReplyUploads(files);
-	}
-
-	function handleReplyDragOver(e: DragEvent) {
-		if (isFileDrag(e)) e.preventDefault();
-	}
-
-	function handleReplyDrop(e: DragEvent) {
-		const files = filesFromDrop(e);
-		if (files.length === 0) return;
-		e.preventDefault();
-		startReplyUploads(files);
-	}
-
-	async function submitReply() {
-		const body = replyBody.trim();
-		if (!body || submittingReply || replyPending > 0) return;
+	// Posts a reply via the host callback. Throws on failure so CommentEditor
+	// keeps the draft; closes the form on success.
+	async function submitReply(body: string) {
 		submittingReply = true;
 		try {
 			await onReply(comment.id, body);
-			replyBody = '';
 			showReplyForm = false;
-		} catch {
-			// Keep draft on failure so the user can retry.
+		} catch (err) {
+			throw err;
 		} finally {
 			submittingReply = false;
 		}
 	}
 
-	function handleReplyKeydown(e: KeyboardEvent) {
-		if (e.key === 'Enter' && (e.ctrlKey || e.metaKey)) {
-			e.preventDefault();
-			submitReply();
-		}
-		if (e.key === 'Escape') {
-			showReplyForm = false;
-			replyBody = '';
-		}
-	}
-
 	interface ReactionGroup {
 		emoji: string;
 		count: number;
@@ -245,30 +192,15 @@
 
 	{#if showReplyForm && canEdit}
 		<div class="reply-compose">
-			<textarea
-				class="reply-input"
-				bind:this={replyTextarea}
-				placeholder="Write a reply... (paste or drop an image to attach)"
-				bind:value={replyBody}
-				onkeydown={handleReplyKeydown}
-				onpaste={handleReplyPaste}
-				ondragover={handleReplyDragOver}
-				ondrop={handleReplyDrop}
-				disabled={submittingReply}
-			></textarea>
-			<div class="reply-actions">
-				<span class="reply-hint">
-					{replyPending > 0
-						? `Uploading ${replyPending} file${replyPending === 1 ? '' : 's'}…`
-						: 'Ctrl+Enter to submit · Esc to cancel'}
-				</span>
-				<div class="reply-buttons">
-					<button class="reply-cancel" type="button" onclick={() => { showReplyForm = false; replyBody = ''; }}>Cancel</button>
-					<button class="reply-submit" type="button" disabled={!replyBody.trim() || submittingReply || replyPending > 0} onclick={submitReply}>
-						{submittingReply ? 'Posting...' : 'Reply'}
-					</button>
-				</div>
-			</div>
+			<CommentEditor
+				{wsSlug}
+				placeholder="Write a reply… (paste or drop an image to attach)"
+				submitLabel="Reply"
+				autofocus
+				submitting={submittingReply}
+				onSubmit={submitReply}
+				onCancel={() => { showReplyForm = false; }}
+			/>
 		</div>
 	{/if}
 
@@ -549,80 +481,7 @@
 		display: flex;
 		flex-direction: column;
 		gap: var(--space-2);
-	}
-
-	.reply-input {
-		width: 100%;
-		padding: var(--space-2) var(--space-3);
-		background: var(--bg-tertiary);
-		border: 1px solid var(--border);
-		border-radius: var(--radius-sm);
-		color: var(--text-primary);
-		font-size: 0.85em;
-		font-family: inherit;
-		line-height: 1.5;
-		resize: vertical;
-		min-height: 52px;
-	}
-
-	.reply-input::placeholder {
-		color: var(--text-muted);
-	}
-
-	.reply-input:focus {
-		outline: none;
-		border-color: var(--accent-blue);
-	}
-
-	.reply-actions {
-		display: flex;
-		align-items: center;
-		justify-content: space-between;
-	}
-
-	.reply-hint {
-		font-size: 0.7em;
-		color: var(--text-muted);
-	}
-
-	.reply-buttons {
-		display: flex;
-		gap: var(--space-2);
-	}
-
-	.reply-cancel {
-		padding: var(--space-1) var(--space-3);
-		border: 1px solid var(--border);
-		border-radius: var(--radius-sm);
-		background: var(--bg-secondary);
-		color: var(--text-muted);
-		font-size: 0.8em;
-		cursor: pointer;
-	}
-
-	.reply-cancel:hover {
-		color: var(--text-primary);
-		border-color: var(--text-muted);
-	}
-
-	.reply-submit {
-		padding: var(--space-1) var(--space-3);
-		background: var(--accent-blue);
-		border: none;
-		border-radius: var(--radius-sm);
-		color: #fff;
-		font-size: 0.8em;
-		font-weight: 500;
-		cursor: pointer;
-	}
-
-	.reply-submit:hover:not(:disabled) {
-		filter: brightness(1.1);
-	}
-
-	.reply-submit:disabled {
-		opacity: 0.5;
-		cursor: not-allowed;
+		margin-top: var(--space-2);
 	}
 
 	.replies {