diff --git a/apps/desktop/src/renderer/reference-shell.css b/apps/desktop/src/renderer/reference-shell.css
index 8b8fff3849..0e277bd6e0 100644
--- a/apps/desktop/src/renderer/reference-shell.css
+++ b/apps/desktop/src/renderer/reference-shell.css
@@ -96,14 +96,7 @@
   box-shadow: none;
 }
 
-.agents-chat-panel {
-  min-width: 0;
-  min-height: 0;
-  display: flex;
-  flex: 1 1 auto;
-  flex-direction: column;
-}
-
+.agents-chat-panel,
 .agents-chat-view-root {
   min-width: 0;
   min-height: 0;
diff --git a/apps/desktop/src/renderer/styles/chat-header.css b/apps/desktop/src/renderer/styles/chat-header.css
index 2a1402e19c..438d0fa3df 100644
--- a/apps/desktop/src/renderer/styles/chat-header.css
+++ b/apps/desktop/src/renderer/styles/chat-header.css
@@ -186,23 +186,16 @@
 }
 
 .maka-chatContent {
-  position: relative;
   width: 100%;
   box-sizing: border-box;
   padding-inline: var(--maka-transcript-gutter);
 }
 
 .maka-chat-layout {
-  width: 100%;
-  min-height: 0;
-  flex: 1 1 auto;
-  display: flex;
-  flex-direction: column;
   overscroll-behavior: contain;
 }
 
 .maka-chat-shell {
-  position: relative;
   min-height: 0;
   display: flex;
   flex-direction: column;
diff --git a/apps/desktop/src/renderer/styles/chat-message.css b/apps/desktop/src/renderer/styles/chat-message.css
index 45132f41f2..d3576b6b95 100644
--- a/apps/desktop/src/renderer/styles/chat-message.css
+++ b/apps/desktop/src/renderer/styles/chat-message.css
@@ -33,14 +33,6 @@
 
 /* Astryx owns sender-aware row alignment; Maka only declares the product
    reading geometry and the deliberately dense conversation type scale. */
-.maka-chat-message {
-  width: 100%;
-  opacity: 1;
-}
-
-.maka-chat-message-list {
-  width: 100%;
-}
 
 /* Native anchoring handles ordinary content growth. The scroll authority
    disables it during following and atomic range replacement, when it owns
@@ -60,7 +52,6 @@
 
 .maka-transcript-turn {
   display: flex;
-  width: 100%;
   flex-direction: column;
   gap: var(--spacing-4);
   /* Resident Turns contribute their real size before the first scroll. */
diff --git a/apps/desktop/stories/app-shell.stories.tsx b/apps/desktop/stories/app-shell.stories.tsx
index 91122169bb..de3e479a3b 100644
--- a/apps/desktop/stories/app-shell.stories.tsx
+++ b/apps/desktop/stories/app-shell.stories.tsx
@@ -3744,8 +3744,8 @@ const processDisclosureMessages: StoredMessage[] = [
   { type: 'assistant', id: 'process-check', turnId: 'process-turn', ts: NOW - 184_000, text: '我先检查登录状态的存储和恢复逻辑。', thinking: { text: '检查初始化时机与会话恢复顺序。' }, modelId: 'claude-sonnet-4-5' },
   { type: 'tool_call', id: 'process-edit', turnId: 'process-turn', ts: NOW - 160_000, toolName: 'Edit', activityKind: 'edit', stepId: 'process-fix', args: { path: 'src/auth-store.ts', old_string: 'const session = null;', new_string: 'const session = restoreSession();' } },
   { type: 'tool_result', id: 'process-edit-result', turnId: 'process-turn', ts: NOW - 150_000, toolUseId: 'process-edit', isError: false, content: { kind: 'text', text: 'Updated src/auth-store.ts' } },
-  { type: 'assistant', id: 'process-fix', turnId: 'process-turn', ts: NOW - 149_000, text: '恢复时机有问题，接下来补上初始化。', modelId: 'claude-sonnet-4-5' },
-  { type: 'tool_call', id: 'process-test', turnId: 'process-turn', ts: NOW - 90_000, toolName: 'Bash', activityKind: 'command', stepId: 'process-verify', args: { command: 'npm test -- auth-store.test.ts' } },
+  { type: 'assistant', id: 'process-fix', turnId: 'process-turn', ts: NOW - 149_000, text: '恢复时机有问题，接下来补上初始化。\n\n```text\nconst session = restoreSession(readPersistedSessionSnapshotFromStorageWithMigratedLegacyKeyFormat(storage));\n```', modelId: 'claude-sonnet-4-5' },
+  { type: 'tool_call', id: 'process-test', turnId: 'process-turn', ts: NOW - 90_000, toolName: 'Bash', activityKind: 'command', stepId: 'process-verify', args: { command: 'npm test -- auth-store.test.ts --coverage --reporter=verbose && npm run lint -- src/auth-store.ts src/session/*.test.ts --max-warnings=0' } },
   { type: 'tool_result', id: 'process-test-result', turnId: 'process-turn', ts: NOW - 5_000, toolUseId: 'process-test', isError: false, content: { kind: 'text', text: 'Tests passed: 4' } },
   { type: 'assistant', id: 'process-verify', turnId: 'process-turn', ts: NOW - 4_000, text: '初始化已补齐，现在运行登录状态的回归测试。', modelId: 'claude-sonnet-4-5' },
   { type: 'assistant', id: 'process-answer', turnId: 'process-turn', ts: NOW, text: '已修复登录状态恢复。\n\n刷新页面后会恢复已有会话；相关测试通过。', modelId: 'claude-sonnet-4-5' },
@@ -3927,6 +3927,16 @@ export const CompletedProcessExpanded: Story = {
     await waitFor(() => expect(process.getBoundingClientRect().height).toBeGreaterThanOrEqual(summary.getBoundingClientRect().height + process.querySelector<HTMLElement>('.maka-processing-body')!.clientHeight - 1));
     const processBody = process.querySelector<HTMLElement>('.maka-processing-body')!;
     await expect(getComputedStyle(processBody).overflowY).toBe('clip');
+    // One unbreakable child must not widen the body's box past the details'
+    // own: the disclosure grid's column track is pinned, so the code line
+    // scrolls inside its block instead of pushing every sibling to a
+    // clipped off-canvas width.
+    const processBox = process.getBoundingClientRect();
+    await expect(processBody.getBoundingClientRect().width).toBeLessThanOrEqual(processBox.width + 1);
+    for (const child of processBody.children) {
+      await expect(child.getBoundingClientRect().width, child.className.toString())
+        .toBeLessThanOrEqual(processBox.width + 1);
+    }
     await expect(summary).toHaveFocus();
     await expect(await within(canvasElement).findByText('我先检查登录状态的存储和恢复逻辑。')).toBeVisible();
     const answer = await within(canvasElement).findByText('已修复登录状态恢复。');
diff --git a/packages/ui/src/chat-turn.tsx b/packages/ui/src/chat-turn.tsx
index eeb1dcd2a9..f7ce207834 100644
--- a/packages/ui/src/chat-turn.tsx
+++ b/packages/ui/src/chat-turn.tsx
@@ -1456,16 +1456,10 @@ const TurnTimelineEntry = memo(function TurnTimelineEntry(props: {
 
 /**
  * The turn's whole execution process (reasoning, intermediate commentary, tool
- * activity) as ONE bounded, scrollable card: a titled header row and, when
- * open, a body that grows with its content up to a cap and then scrolls. The
- * container's border is the card's frame, so a collapsed box keeps its outline
- * and shows only the title row.
- *
- * The body owns its own scroll, not the transcript: a turn with hundreds of
- * steps scrolls here instead of becoming an unreadable wall the reader has to
- * traverse. While the body overflows, its top and/or bottom edge fades the
- * content out, so the clipped rows read as "more above/below" rather than
- * abruptly cut off.
+ * activity) as one in-flow disclosure: a titled header row and, when open, the
+ * full body laid out in the transcript's own scroll path. The container's
+ * border is the frame, so a collapsed box keeps its outline and shows only the
+ * title row.
  */
 export const ProcessingBlock = memo(function ProcessingBlock(props: {
   activityObserved?: boolean;
diff --git a/packages/ui/src/styles.css b/packages/ui/src/styles.css
index ff581cc4a3..1e273f7789 100644
--- a/packages/ui/src/styles.css
+++ b/packages/ui/src/styles.css
@@ -304,7 +304,13 @@
    Product CSS keeps only what is layout: it is a block-level note under the
    bubble, so it needs its own line and the gap above it. */
 .maka-turn-truncation-badge { display: flex; width: fit-content; margin-top: 6px; cursor: help; }
-.maka-processing-sequence { min-width: 0; }
+.maka-processing-sequence {
+  min-width: 0;
+  /* Astryx tool rows overhang their text by 4px on each inline edge so hover
+     surfaces reach the card edge (their padding/negative-margin pair); this
+     padding is where that overhang lands inside the paint boundary. */
+  padding-inline: var(--space-1);
+}
 .maka-processing-summary {
   display: flex;
   align-items: center;
@@ -327,7 +333,9 @@
   min-height: 0;
   flex-direction: column;
   gap: 8px;
-  overflow: clip;
+  /* Block-axis clip for the disclosure wipe only; the rows' inline overhang
+     must reach the sequence's padding edge, so it cannot be clipped here. */
+  overflow-y: clip;
 }
 .maka-processing-body > :first-child { margin-top: var(--space-2); }
 /* Match Astryx ChatToolCalls' grid disclosure motion. The native details
@@ -336,6 +344,11 @@
 @supports selector(::details-content) {
   .maka-processing-sequence::details-content {
     display: grid;
+    /* An implicit `auto` column track grows to the item's max-content, so one
+       unbreakable row would widen the whole body past the reading measure and
+       every row would clip at the sequence's paint boundary. Pin the column to
+       the grid's inline size; overflow stays each child's own problem. */
+    grid-template-columns: minmax(0, 1fr);
     grid-template-rows: 0fr;
     transition: grid-template-rows var(--duration-medium) var(--ease-standard),
       content-visibility var(--duration-medium) allow-discrete;