diff --git a/packages/web-shell/client/hooks/useComposerCore.dom.test.tsx b/packages/web-shell/client/hooks/useComposerCore.dom.test.tsx
index bb787a79e0..289adf824b 100644
--- a/packages/web-shell/client/hooks/useComposerCore.dom.test.tsx
+++ b/packages/web-shell/client/hooks/useComposerCore.dom.test.tsx
@@ -122,6 +122,72 @@ describe('useComposerCore inline tags', () => {
     warn.mockRestore();
   });
 
+  it('uses a custom inline tooltip without a native title', async () => {
+    await mount({
+      composerInput: {
+        tags: [{ id: 'orders', label: 'Table', value: 'orders' }],
+        tagPlacement: 'inline',
+      },
+      renderComposerTagTooltip: () => 'Details',
+    });
+
+    const tooltip = document.body.querySelector('[role="tooltip"]');
+    expect(tooltip?.textContent).toBe('Details');
+    expect(tooltip?.parentElement?.getAttribute('title')).toBeNull();
+    expect(tooltip?.id).toBeTruthy();
+    expect(tooltip?.parentElement?.getAttribute('aria-describedby')).toBe(
+      tooltip?.id,
+    );
+  });
+
+  it('falls back to a native title when attaching an inline tooltip fails', async () => {
+    const error = new Error('append failed');
+    const appendChild = HTMLElement.prototype.appendChild;
+    let failingTooltip: HTMLElement | null = null;
+    let readFailingChipTitle: (() => string) | null = null;
+    let dispatchOnFailingChip: ((event: Event) => boolean) | null = null;
+    const appendChildSpy = vi
+      .spyOn(HTMLElement.prototype, 'appendChild')
+      .mockImplementation(function (child) {
+        if (
+          child instanceof HTMLElement &&
+          child.getAttribute('role') === 'tooltip'
+        ) {
+          failingTooltip = child;
+          readFailingChipTitle = () => this.title;
+          dispatchOnFailingChip = (event) => this.dispatchEvent(event);
+          throw error;
+        }
+        return appendChild.call(this, child);
+      });
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {
+      expect(readFailingChipTitle?.()).toBe('Details');
+    });
+
+    try {
+      await mount({
+        composerInput: {
+          tags: [{ id: 'orders', label: 'Table', value: 'orders' }],
+          tagPlacement: 'inline',
+        },
+        renderComposerTagTooltip: () => 'Details',
+      });
+
+      expect(warn).toHaveBeenCalledWith(
+        '[WebShell] inline tag tooltip render failed',
+        error,
+      );
+      const chip = document.body.querySelector('[title="Details"]');
+      expect(chip).not.toBeNull();
+      expect(document.body.querySelector('[role="tooltip"]')).toBeNull();
+      dispatchOnFailingChip?.(new MouseEvent('mouseenter'));
+      expect(failingTooltip?.style.display).toBe('none');
+    } finally {
+      warn.mockRestore();
+      appendChildSpy.mockRestore();
+    }
+  });
+
   it('guards inline mask icon sources', async () => {
     await mount({
       composerInput: {
diff --git a/packages/web-shell/client/hooks/useComposerCore.ts b/packages/web-shell/client/hooks/useComposerCore.ts
index 8a2aa86284..ed13529174 100644
--- a/packages/web-shell/client/hooks/useComposerCore.ts
+++ b/packages/web-shell/client/hooks/useComposerCore.ts
@@ -604,6 +604,8 @@ export const removeInlineTagEffect = StateEffect.define<{
 }>();
 export const clearInlineTagsEffect = StateEffect.define<void>();
 
+let nextComposerTagTooltipId = 0;
+
 class ComposerTagWidget extends WidgetType {
   private contentRoot: Root | null = null;
   private tooltipRoot: Root | null = null;
@@ -634,7 +636,6 @@ class ComposerTagWidget extends WidgetType {
     const publicTag = toPublicComposerTag(this.tag);
     chip.style.cssText =
       'position:relative;display:inline-flex;align-items:center;max-width:min(44ch,100%);min-height:20px;margin:0 0.25ch;border:1px solid var(--border);border-radius:4px;background:var(--secondary);color:var(--foreground);font-family:var(--font-mono,monospace);font-size:12px;line-height:1.2;vertical-align:baseline;';
-    if (this.tag.tooltipText) chip.title = this.tag.tooltipText;
     if (this.tag.onClick) {
       chip.setAttribute('role', 'button');
       chip.tabIndex = 0;
@@ -760,6 +761,21 @@ class ComposerTagWidget extends WidgetType {
     tooltipElement.setAttribute('role', 'tooltip');
     tooltipElement.style.cssText =
       'position:absolute;z-index:calc(var(--web-shell-tooltip-z-index,1000) + 1);top:calc(100% + 6px);left:0;display:none;min-width:160px;max-width:min(320px,80vw);padding:8px 10px;border:1px solid var(--border);border-radius:6px;background:var(--background);box-shadow:0 8px 24px rgba(0,0,0,0.18);color:var(--foreground);font-family:var(--font-sans,system-ui,sans-serif);font-size:12px;line-height:1.5;white-space:normal;';
+    try {
+      this.tooltipRoot = createRoot(tooltipElement);
+      this.tooltipRoot.render(tooltip);
+      chip.appendChild(tooltipElement);
+      tooltipElement.id = `composer-tag-tooltip-${++nextComposerTagTooltipId}`;
+      chip.setAttribute('aria-describedby', tooltipElement.id);
+    } catch (error) {
+      this.tooltipRoot?.unmount();
+      this.tooltipRoot = null;
+      if (this.tag.tooltipText) {
+        chip.title = this.tag.tooltipText;
+      }
+      console.warn('[WebShell] inline tag tooltip render failed', error);
+      return;
+    }
     const show = () => {
       tooltipElement.style.display = 'block';
     };
@@ -770,15 +786,6 @@ class ComposerTagWidget extends WidgetType {
     chip.addEventListener('mouseleave', hide);
     chip.addEventListener('focusin', show);
     chip.addEventListener('focusout', hide);
-    try {
-      this.tooltipRoot = createRoot(tooltipElement);
-      this.tooltipRoot.render(tooltip);
-      chip.appendChild(tooltipElement);
-    } catch (error) {
-      this.tooltipRoot?.unmount();
-      this.tooltipRoot = null;
-      console.warn('[WebShell] inline tag tooltip render failed', error);
-    }
   }
 
   private appendRemoveButton(chip: HTMLElement, view: EditorView) {