diff --git a/frontend/src/components/Chat/ChatInputArea.test.tsx b/frontend/src/components/Chat/ChatInputArea.test.tsx
index c4c893cc9..13f1ba8ae 100644
--- a/frontend/src/components/Chat/ChatInputArea.test.tsx
+++ b/frontend/src/components/Chat/ChatInputArea.test.tsx
@@ -223,10 +223,26 @@ describe("ChatInputArea", () => {
       </TestWrapper>
     );
 
-    const attachButton = screen.getByTitle("Attach files");
+    const attachButton = screen.getByRole("button", { name: /attach files/i });
     expect(attachButton).toBeInTheDocument();
   });
 
+  it("should expose all icon-only buttons via aria-label, not only title", () => {
+    // Regression guard against using only `title=` for icon buttons.
+    // `title` is not a reliable accessible name for screen readers; aria-label
+    // is. All icon-only buttons in the input area must be reachable by role
+    // + name (i.e., they have an aria-label that matches the visible tooltip).
+    render(
+      <TestWrapper>
+        <ChatInputArea {...defaultProps} />
+      </TestWrapper>
+    );
+
+    expect(screen.getByRole("button", { name: /attach files/i })).toBeInTheDocument();
+    expect(screen.getByRole("button", { name: /toggle converter panel/i })).toBeInTheDocument();
+    expect(screen.getByRole("button", { name: /send message/i })).toBeInTheDocument();
+  });
+
   it("should handle file attachment selection", async () => {
     const user = userEvent.setup();
 
@@ -478,7 +494,7 @@ describe("ChatInputArea", () => {
     });
 
     // Send button should be enabled since there's an attachment
-    expect(screen.getByTitle("Send message")).toBeEnabled();
+    expect(screen.getByRole("button", { name: /send message/i })).toBeEnabled();
   });
 
   it("should show single-turn banner when singleTurnLimitReached is true", () => {
diff --git a/frontend/src/components/Chat/ChatInputArea.tsx b/frontend/src/components/Chat/ChatInputArea.tsx
index 82c1817e6..749a7b8ee 100644
--- a/frontend/src/components/Chat/ChatInputArea.tsx
+++ b/frontend/src/components/Chat/ChatInputArea.tsx
@@ -475,23 +475,27 @@ const ChatInputArea = forwardRef<ChatInputAreaHandle, ChatInputAreaProps>(functi
           />
           <div className={styles.inputColumns}>
             <div className={styles.columnLeft}>
-              <Button
-                className={styles.iconButton}
-                appearance="subtle"
-                icon={<AttachRegular />}
-                onClick={() => fileInputRef.current?.click()}
-                disabled={disabled}
-                title="Attach files"
-              />
-              <Button
-                className={styles.iconButton}
-                appearance={isConverterPanelOpen ? 'primary' : 'subtle'}
-                icon={<ArrowShuffleRegular />}
-                onClick={onToggleConverterPanel}
-                disabled={disabled}
-                data-testid="toggle-converter-panel-btn"
-                title="Toggle converter panel"
-              />
+              <Tooltip content="Attach files" relationship="label">
+                <Button
+                  className={styles.iconButton}
+                  appearance="subtle"
+                  icon={<AttachRegular />}
+                  onClick={() => fileInputRef.current?.click()}
+                  disabled={disabled}
+                  aria-label="Attach files"
+                />
+              </Tooltip>
+              <Tooltip content="Toggle converter panel" relationship="label">
+                <Button
+                  className={styles.iconButton}
+                  appearance={isConverterPanelOpen ? 'primary' : 'subtle'}
+                  icon={<ArrowShuffleRegular />}
+                  onClick={onToggleConverterPanel}
+                  disabled={disabled}
+                  data-testid="toggle-converter-panel-btn"
+                  aria-label="Toggle converter panel"
+                />
+              </Tooltip>
             </div>
             <div className={styles.columnCenter}>
               <AttachmentList
@@ -547,15 +551,17 @@ const ChatInputArea = forwardRef<ChatInputAreaHandle, ChatInputAreaProps>(functi
                   </span>
                 </Tooltip>
               )}
-              <Button
-                className={styles.sendButton}
-                appearance="primary"
-                icon={<SendRegular />}
-                onClick={handleSend}
-                disabled={disabled || (!input && attachments.length === 0) || hasUnsupportedModalities}
-                title="Send message"
-                data-testid="send-message-btn"
-              />
+              <Tooltip content="Send message" relationship="label">
+                <Button
+                  className={styles.sendButton}
+                  appearance="primary"
+                  icon={<SendRegular />}
+                  onClick={handleSend}
+                  disabled={disabled || (!input && attachments.length === 0) || hasUnsupportedModalities}
+                  aria-label="Send message"
+                  data-testid="send-message-btn"
+                />
+              </Tooltip>
               {convertedValue && (
                 <Tooltip content="Clear conversion" relationship="label">
                   <Button
diff --git a/frontend/src/components/Chat/ChatWindow.test.tsx b/frontend/src/components/Chat/ChatWindow.test.tsx
index a2666fc18..465d921c7 100644
--- a/frontend/src/components/Chat/ChatWindow.test.tsx
+++ b/frontend/src/components/Chat/ChatWindow.test.tsx
@@ -2130,6 +2130,26 @@ describe("ChatWindow Integration", () => {
     });
   });
 
+  it("should expose the conversations panel toggle via aria-label", () => {
+    // Regression guard: the toggle button is icon-only and previously relied
+    // on aria-label without a visible tooltip; assert both are wired up so
+    // the button is reachable by accessible name (catches regression to
+    // missing aria-label).
+    render(
+      <TestWrapper>
+        <ChatWindow
+          {...defaultProps}
+          attackResultId="ar-aria-toggle"
+          conversationId="conv-aria-toggle"
+          activeConversationId="conv-aria-toggle"
+        />
+      </TestWrapper>
+    );
+
+    const toggleBtn = screen.getByRole("button", { name: /toggle conversations panel/i });
+    expect(toggleBtn).toBe(screen.getByTestId("toggle-panel-btn"));
+  });
+
   it("should toggle converter panel when convert button is clicked", async () => {
     render(
       <TestWrapper>
diff --git a/frontend/src/components/Chat/ChatWindow.tsx b/frontend/src/components/Chat/ChatWindow.tsx
index 43b3b438e..f96fc85ee 100644
--- a/frontend/src/components/Chat/ChatWindow.tsx
+++ b/frontend/src/components/Chat/ChatWindow.tsx
@@ -541,6 +541,7 @@ export default function ChatWindow({
                 onClick={() => setIsPanelOpen(!isPanelOpen)}
                 disabled={!attackResultId}
                 data-testid="toggle-panel-btn"
+                aria-label="Toggle conversations panel"
               />
             </Tooltip>
             <Button
diff --git a/frontend/src/components/Chat/MessageList.styles.ts b/frontend/src/components/Chat/MessageList.styles.ts
index 7273fa158..f650686e2 100644
--- a/frontend/src/components/Chat/MessageList.styles.ts
+++ b/frontend/src/components/Chat/MessageList.styles.ts
@@ -20,13 +20,15 @@ export const useMessageListStyles = makeStyles({
     flexDirection: 'row-reverse',
   },
   messageContent: {
-    backgroundColor: tokens.colorNeutralBackground3,
+    backgroundColor: tokens.colorNeutralBackground1,
+    border: `1px solid ${tokens.colorNeutralStroke2}`,
     padding: tokens.spacingVerticalM,
     borderRadius: tokens.borderRadiusMedium,
     flex: 1,
   },
   userMessageContent: {
-    backgroundColor: tokens.colorBrandBackground,
+    backgroundColor: tokens.colorBrandBackground2,
+    border: `1px solid ${tokens.colorBrandStroke2}`,
   },
   messageText: {
     whiteSpace: 'pre-wrap',
diff --git a/frontend/src/components/Chat/MessageList.test.tsx b/frontend/src/components/Chat/MessageList.test.tsx
index fd68e15ab..3dd3cfe3e 100644
--- a/frontend/src/components/Chat/MessageList.test.tsx
+++ b/frontend/src/components/Chat/MessageList.test.tsx
@@ -87,6 +87,50 @@ describe("MessageList", () => {
     expect(screen.getByText("Assistant message test")).toBeInTheDocument();
   });
 
+  describe("bubble class composition", () => {
+    // Regression guard for an earlier bug where the user-bubble background
+    // override silently lost to the assistant-bubble base style. The cause was
+    // string-concatenated class names — Griffel's atomic CSS doesn't dedupe
+    // conflicting properties unless mergeClasses is used. We assert here that
+    // the two bubble containers receive distinguishable className strings, so
+    // the override always has a chance to win.
+    it("renders user and assistant bubbles with distinct class signatures", () => {
+      render(
+        <TestWrapper>
+          <MessageList
+            messages={[
+              {
+                role: "user",
+                content: "u",
+                timestamp: new Date().toISOString(),
+              },
+              {
+                role: "assistant",
+                content: "a",
+                timestamp: new Date().toISOString(),
+              },
+            ]}
+          />
+        </TestWrapper>
+      );
+      const userBubble = screen.getByTestId("message-bubble-0");
+      const assistantBubble = screen.getByTestId("message-bubble-1");
+      // The two bubble class strings must differ — otherwise the user
+      // override silently lost (which was the original bug).
+      expect(userBubble.className).not.toBe(assistantBubble.className);
+      // Both bubbles must carry at least one style hook (catches a future
+      // refactor that drops the className entirely).
+      expect(userBubble.className.trim()).not.toBe('');
+      expect(assistantBubble.className.trim()).not.toBe('');
+      // The user bubble must carry at least one style hook the assistant
+      // bubble doesn't have — that's the override actually being applied.
+      const userClasses = userBubble.className.split(/\s+/).filter(Boolean);
+      const assistantClasses = new Set(assistantBubble.className.split(/\s+/).filter(Boolean));
+      const userOnly = userClasses.filter(c => !assistantClasses.has(c));
+      expect(userOnly.length).toBeGreaterThan(0);
+    });
+  });
+
   it("should handle messages with image attachments", () => {
     const messagesWithAttachments: Message[] = [
       {
@@ -800,6 +844,40 @@ describe("MessageList", () => {
       expect(btn).toBeInTheDocument();
       expect(btn).toBeDisabled();
     });
+
+    it("should give the four disabled action buttons distinct accessible names", () => {
+      // Regression guard: previously several disabled-state tooltips collapsed
+      // to identical strings (e.g. both branch buttons read
+      // "Cannot branch — target is single-turn"), so a screen reader could
+      // not tell them apart. Each disabled action's accessible name must be
+      // unique.
+      render(
+        <TestWrapper>
+          <MessageList
+            messages={assistantMessage}
+            onCopyToInput={jest.fn()}
+            onCopyToNewConversation={jest.fn()}
+            onBranchConversation={jest.fn()}
+            onBranchAttack={jest.fn()}
+            isSingleTurn={true}
+          />
+        </TestWrapper>
+      );
+
+      const btns = [
+        screen.getByTestId("copy-to-input-btn-0"),
+        screen.getByTestId("copy-to-new-conv-btn-0"),
+        screen.getByTestId("branch-conv-btn-0"),
+        screen.getByTestId("branch-attack-btn-0"),
+      ];
+      const names = btns.map(b => b.getAttribute("aria-label") ?? "");
+      // None empty
+      for (const name of names) {
+        expect(name).not.toBe("");
+      }
+      // All distinct
+      expect(new Set(names).size).toBe(names.length);
+    });
   });
 
   describe("original vs converted display", () => {
diff --git a/frontend/src/components/Chat/MessageList.tsx b/frontend/src/components/Chat/MessageList.tsx
index 6e2a54086..054ad2a82 100644
--- a/frontend/src/components/Chat/MessageList.tsx
+++ b/frontend/src/components/Chat/MessageList.tsx
@@ -8,6 +8,7 @@ import {
   Button,
   Tooltip,
   Spinner,
+  mergeClasses,
 } from '@fluentui/react-components'
 import { ArrowDownloadRegular, ArrowReplyRegular, ArrowForwardRegular, ChatAddRegular, BranchForkRegular } from '@fluentui/react-icons'
 import { Message, MessageAttachment } from '../../types'
@@ -138,13 +139,16 @@ export default function MessageList({ messages, onCopyToInput, onCopyToNewConver
         return (
           <div
             key={index}
-            className={`${styles.message} ${isUser ? styles.userMessage : ''}`}
+            className={mergeClasses(styles.message, isUser && styles.userMessage)}
           >
             <Avatar
               name={avatarName}
               color={isUser ? 'colorful' : isSimulated ? 'steel' : 'brand'}
             />
-            <div className={`${styles.messageContent} ${isUser ? styles.userMessageContent : ''}`}>
+            <div
+              className={mergeClasses(styles.messageContent, isUser && styles.userMessageContent)}
+              data-testid={`message-bubble-${index}`}
+            >
               {/* Error rendering */}
               {message.error && (
                 <div className={styles.errorContainer}>
@@ -248,13 +252,13 @@ export default function MessageList({ messages, onCopyToInput, onCopyToNewConver
                   {onCopyToInput && (() => {
                     const disabled = Boolean(noTargetSelected || isSingleTurn || isOperatorLocked || isCrossTarget)
                     const tip = noTargetSelected
-                      ? 'Cannot copy — no target selected'
+                      ? 'Cannot copy to this conversation — no target selected'
                       : isSingleTurn
-                        ? 'Cannot copy — target is single-turn'
+                        ? 'Cannot copy to this conversation — target is single-turn'
                         : isOperatorLocked
-                          ? 'Cannot copy — you are not the operator of this attack'
+                          ? 'Cannot copy to this conversation — you are not the operator of this attack'
                           : isCrossTarget
-                            ? 'Cannot copy — conversation used a different target'
+                            ? 'Cannot copy to this conversation — it used a different target'
                             : 'Copy to input box in this conversation'
                     return (
                       <Tooltip content={tip} relationship="label">
@@ -275,11 +279,11 @@ export default function MessageList({ messages, onCopyToInput, onCopyToNewConver
                   {onCopyToNewConversation && (() => {
                     const disabled = Boolean(noTargetSelected || isOperatorLocked || isCrossTarget)
                     const tip = noTargetSelected
-                      ? 'Cannot copy — no target selected'
+                      ? 'Cannot copy to a new conversation — no target selected'
                       : isOperatorLocked
-                        ? 'Cannot add to this attack — you are not the operator'
+                        ? 'Cannot copy to a new conversation — you are not the operator of this attack'
                         : isCrossTarget
-                          ? 'Cannot add to this attack — conversation used a different target'
+                          ? 'Cannot copy to a new conversation — this attack used a different target'
                           : 'Copy to input box in a new conversation'
                     return (
                       <Tooltip content={tip} relationship="label">
@@ -300,13 +304,13 @@ export default function MessageList({ messages, onCopyToInput, onCopyToNewConver
                   {onBranchConversation && (() => {
                     const disabled = Boolean(noTargetSelected || isSingleTurn || isOperatorLocked || isCrossTarget)
                     const tip = noTargetSelected
-                      ? 'Cannot branch — no target selected'
+                      ? 'Cannot branch into new conversation — no target selected'
                       : isSingleTurn
-                        ? 'Cannot branch — target is single-turn'
+                        ? 'Cannot branch into new conversation — target is single-turn'
                         : isOperatorLocked
-                          ? 'Cannot add to this attack — you are not the operator'
+                          ? 'Cannot branch into new conversation — you are not the operator of this attack'
                           : isCrossTarget
-                            ? 'Cannot add to this attack — conversation used a different target'
+                            ? 'Cannot branch into new conversation — this attack used a different target'
                             : 'Branch into new conversation'
                     return (
                       <Tooltip content={tip} relationship="label">
@@ -342,9 +346,9 @@ export default function MessageList({ messages, onCopyToInput, onCopyToNewConver
                     }
                     // Show disabled button with reason
                     const tip = noTargetSelected
-                      ? 'Cannot branch — no target selected'
+                      ? 'Cannot branch into new attack — no target selected'
                       : singleTurnBlock
-                        ? 'Cannot branch — target is single-turn'
+                        ? 'Cannot branch into new attack — target is single-turn'
                         : undefined
                     if (!tip) return null
                     return (