fix: preserve Shell tab scroll position across periodic refresh

[CoderLuii]

problem

the Shell tab resets scroll position to the top every ~1 second. when you scroll up to review output, it snaps back almost immediately.

root cause

the useEffect in Shell.tsx (lines 157-173) calls terminalRef.current?.focus() via requestAnimationFrame and setTimeout whenever isActive, isConnected, or isInitialized change. the 1-second settings polling interval triggers React re-renders, which re-fire this effect. xterm.js focus() resets the viewport to the cursor position (bottom), losing the user's scroll position.

fix

save buffer.active.viewportY before calling focus(), restore it via scrollToLine() after. this is the same pattern VS Code uses in markNavigationAddon.ts.

     const focusTerminal = () => {
-      terminalRef.current?.focus();
+      const term = terminalRef.current;
+      if (!term) return;
+      const savedViewport = term.buffer.active.viewportY;
+      term.focus();
+      term.scrollToLine(savedViewport);
     };

auto-scroll to bottom still works when the user is already at the bottom (default xterm behavior — focus() moves viewport to cursor, scrollToLine restores the same position since cursor is at the bottom).

Summary by CodeRabbit

• Bug Fixes
  • Fixed terminal focus behavior to preserve the current viewport position, preventing accidental scrolling when the terminal regains focus.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: e37ac5f3-da22-4994-9965-52528f17ef7b

📥 Commits

Reviewing files that changed from the base of the PR and between 388134c and b61736c.

📒 Files selected for processing (1)

• src/components/shell/view/Shell.tsx

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📝 Walkthrough

Walkthrough

Updated the focusTerminal logic to preserve the terminal's viewport position when focusing. The implementation now saves the current viewport position before focusing and restores it afterward, maintaining view continuity while ensuring the terminal receives focus.

Changes

Cohort / File(s)	Summary
Terminal Focus Viewport Preservation src/components/shell/view/Shell.tsx	Modified the focusTerminal effect to capture the current viewport position before focusing, then restore it after. Focus scheduling via requestAnimationFrame and setTimeout remains unchanged.

Poem

🐰 The terminal now holds its view so tight,
When focus arrives, the viewport stays in sight,
No more jumping scrolls or vanished lines,
Just smooth refocus—a rabbit-approved design! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix: preserve Shell tab scroll position across periodic refresh' directly and accurately describes the main change: preserving scroll position in the Shell tab during periodic refreshes.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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