diff --git a/packages/dashboard/app/components/SelectionCommentPopover.css b/packages/dashboard/app/components/SelectionCommentPopover.css
index a71ddcc3fd..1dd90d52ac 100644
--- a/packages/dashboard/app/components/SelectionCommentPopover.css
+++ b/packages/dashboard/app/components/SelectionCommentPopover.css
@@ -30,8 +30,26 @@ FileEditor (editor and preview), desktop and mobile.
   transform: translate(-50%, calc(-1 * var(--space-xl))) scale(0.97);
 }
 
+/*
+FNXC:ArtifactsView 2026-07-10-18:20:
+The composer panel carries the shared `.card` class, and `.card { position: relative }` loads AFTER
+this file in the bundle, so at equal specificity it silently replaced the panel's `position: fixed`.
+The panel then flowed inside `.documents-content-viewer` with the left/top vars applied as relative
+offsets — rendering clipped at the bottom-right of the viewport nowhere near the selection.
+`.selection-comment-panel.card` (0,2,0) makes the fixed positioning immune to bundle order.
+The `left` clamp keeps the whole panel inside the viewport on every width: it accounts for half the
+panel width (the panel is centered on the selection via translate(-50%)), and the `top` clamp stops
+a selection near the bottom of the viewport from pushing the composer off-screen.
+*/
+.selection-comment-panel.card {
+  position: fixed;
+}
+
 .selection-comment-panel {
-  width: min(var(--selection-comment-panel-width, calc(var(--space-2xl) * 12)), calc(100vw - (var(--space-lg) * 2)));
+  --scp-width: min(var(--selection-comment-panel-width, calc(var(--space-2xl) * 12)), calc(100vw - (var(--space-lg) * 2)));
+  width: var(--scp-width);
+  left: clamp(calc(var(--space-lg) + (var(--scp-width) / 2)), var(--selection-comment-left), calc(100vw - var(--space-lg) - (var(--scp-width) / 2)));
+  top: min(var(--selection-comment-top), calc(100vh - var(--space-lg) - 20rem));
   transform: translate(-50%, var(--space-xs));
   padding: var(--space-md);
   display: flex;
@@ -71,8 +89,13 @@ FileEditor (editor and preview), desktop and mobile.
 }
 
 @media (max-width: 768px) {
-  .selection-comment-trigger,
-  .selection-comment-panel {
+  /*
+  FNXC:ArtifactsView 2026-07-10-18:20:
+  Only the trigger keeps the simple center-point clamp here — the panel's base rule already applies
+  a width-aware clamp on all viewports, and re-declaring `left` in this later block would override
+  it with a clamp that lets half the panel hang past the edge.
+  */
+  .selection-comment-trigger {
     left: max(var(--space-lg), min(var(--selection-comment-left), calc(100vw - var(--space-lg))));
   }
 
diff --git a/packages/dashboard/app/components/SelectionCommentPopover.tsx b/packages/dashboard/app/components/SelectionCommentPopover.tsx
index efd8d8045e..267ae759bc 100644
--- a/packages/dashboard/app/components/SelectionCommentPopover.tsx
+++ b/packages/dashboard/app/components/SelectionCommentPopover.tsx
@@ -87,7 +87,14 @@ export function SelectionCommentPopover({
 
   useEffect(() => {
     if (!expanded) return;
-    textareaRef.current?.focus();
+    /*
+    FNXC:ArtifactsView 2026-07-10-18:20:
+    The panel is position:fixed, so the default focus scroll-into-view is meaningless for it — but
+    the browser still scrolled the underlying preview pane, yanking the selected content out of
+    view the moment the composer opened. preventScroll keeps the pane exactly where the user
+    selected the text.
+    */
+    textareaRef.current?.focus({ preventScroll: true });
   }, [expanded]);
 
   const setPanelExpanded = useCallback((open: boolean) => {
diff --git a/packages/dashboard/app/components/__tests__/SelectionCommentPopover.test.tsx b/packages/dashboard/app/components/__tests__/SelectionCommentPopover.test.tsx
index 97b08d8240..9945cfbfab 100644
--- a/packages/dashboard/app/components/__tests__/SelectionCommentPopover.test.tsx
+++ b/packages/dashboard/app/components/__tests__/SelectionCommentPopover.test.tsx
@@ -104,6 +104,35 @@ describe("SelectionCommentPopover", () => {
     expect(activeBlocks.length, "both desktop and mobile need an :active override that restates the translate").toBeGreaterThanOrEqual(2);
   });
 
+  /*
+  FNXC:ArtifactsView 2026-07-10-18:20:
+  Regression guard for the composer-panel drift: the panel carries the shared `.card` class, and
+  `.card { position: relative }` loads after this stylesheet, so a bare `.selection-comment-panel`
+  rule lost `position: fixed` to bundle order and the panel rendered clipped at the viewport's
+  bottom-right, far from the selection. The fixed positioning must live on a selector that
+  out-specifies `.card` regardless of order, and the panel's `left` must be a width-aware clamp so
+  a selection near a viewport edge cannot push half the panel off-screen.
+  */
+  it("keeps the composer panel fixed-positioned over .card and clamps it inside the viewport", () => {
+    const css = readFileSync(join(__dirname, "..", "SelectionCommentPopover.css"), "utf8");
+    const uncommented = css.replace(/\/\*[\s\S]*?\*\//g, "");
+
+    const rulePattern = /([^{}]+)\{([^{}]*)\}/g;
+    const blocks = [...uncommented.matchAll(rulePattern)].map((m) => ({ selector: m[1].trim(), block: m[2] }));
+
+    const fixedOverCard = blocks.find(({ selector, block }) =>
+      selector.split(",").some((part) => {
+        const s = part.trim();
+        return s.includes(".selection-comment-panel") && s.includes(".card");
+      }) && /position\s*:\s*fixed/.test(block));
+    expect(fixedOverCard, "a .selection-comment-panel selector compounded with .card must restate position: fixed").toBeTruthy();
+
+    const panelBlocks = blocks.filter(({ selector }) => selector.split(",").some((p) => p.trim() === ".selection-comment-panel"));
+    const clampBlock = panelBlocks.find(({ block }) => /left\s*:\s*clamp\(/.test(block));
+    expect(clampBlock, "panel must declare a width-aware left clamp").toBeTruthy();
+    expect(clampBlock!.block, "left clamp must account for half the panel width").toContain("--scp-width) / 2");
+  });
+
   it("uses a longer markdown fence when the snippet contains backticks", () => {
     expect(composeSelectionCommentDescription({
       filePath: "README.md",