fix: prevent error toasts from overflowing the viewport

[henrytran1803]

Description

Error toasts (e.g. from repeated session share failures) could accumulate without bound, causing the toast stack to overflow the visible window with no way to scroll or dismiss older toasts.

The fix applies a three-layer defense:

1. Cap persistent toast count (MAX_PERSISTENT_TOASTS = 5): When the limit is exceeded, the oldest toast is evicted from the stack.
2. Deduplication by object_id: show_persistent_toast() now sets an object_id based on the toast text, so repeated identical error messages replace older toasts instead of stacking. The existing dismiss_older_toasts mechanism handles this automatically.
3. Layout safety net (ConstrainedBox + Clipped): The rendered toast stack is constrained to a 500px max height with clipping, ensuring toasts never overflow the viewport even in edge cases.

Changes

• app/src/view_components/dismissible_toast.rs:
  • Add MAX_PERSISTENT_TOASTS constant (5) and TOAST_STACK_MAX_HEIGHT constant (500px)
  • Cap persistent toast count in add_persistent_toast() by removing oldest toasts when limit exceeded
  • Wrap toast stack render in ConstrainedBox with Clipped to prevent viewport overflow
• app/src/terminal/view.rs:
  • Add object_id to persistent toasts in show_persistent_toast() for deduplication

Linked Issue

• The linked issue is labeled ready-to-implement.
• Fixes Error toasts can render outside of the viewport, without a way to scroll them. #9733

Testing

The fix is defensive — it caps count, deduplicates, and constrains layout. Manual verification:

• Repeatedly trigger session share failures → older duplicate toasts are replaced (dedup)
• After 5+ unique persistent toasts → oldest evicted (cap)
• Toast stack never exceeds 500px height (layout constraint)

No automated test was added because the toast stack depends on UI rendering infrastructure that requires the full Warp app bootstrap. The logic changes (cap + dedup) are straightforward guards that are easy to verify visually.

Co-Authored-By: Warp agent@warp.dev

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@henrytran1803

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[oz-for-oss]

Overview

This PR caps and deduplicates persistent toasts and adds a render-time max-height clipping guard to keep the toast stack from overflowing the viewport.

Concerns

• No blocking correctness or security concerns found in the annotated diff.

Verdict

Found: 0 critical, 0 important, 0 suggestions

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[RokeJulianLockhart]

1. Cap persistent toast count (MAX_PERSISTENT_TOASTS = 5): When the limit is exceeded, the oldest toast is evicted from the stack.

@henrytran1803, that might be problematic if more than 5 unique toasts are rendered. (Is having them be scrollable infeasible?)

2. Deduplication by object_id: show_persistent_toast() now sets an object_id based on the toast text, so repeated identical error messages replace older toasts instead of stacking. The existing dismiss_older_toasts mechanism handles this automatically.

Rendering a counter, for each time a duplicate toast is replaced, so that the user knows how many times that toast has been produced, would be helpful.

3. Layout safety net (ConstrainedBox + Clipped): The rendered toast stack is constrained to a 500px max height with clipping, ensuring toasts never overflow the viewport even in edge cases.

Can we not, instead, calculate the geometry of the interface, rather than define an arbitrary constant? This might not be sufficient on low-DPI (1 024 × 720 px) displays:

• issues/3328

• issues/7495

• issues/6391

[henrytran1803]

@RokeJulianLockhart great points, all three — pushed a fix that addresses each of them!

1. Scrollable instead of capped — yep, agreed. I dropped the MAX_PERSISTENT_TOASTS cap entirely. Now the toast stack is just constrained to whatever vertical space the tab content actually has, so all unique toasts stay visible (and don't get silently evicted).

2. Counter for duplicates — nice idea! Instead of replacing the duplicate, I now increment a counter on the existing toast and display it as (x3) in the text. That way the user can see something's going wrong repeatedly without the toast stack growing.

3. Viewport geometry instead of 500px — good catch on low-DPI, that would've been embarrassing 😅 Replaced the hardcoded constant with a computed height from TAB_CONTENT_POSITION_ID's actual rect (height - 32px for margins). Should scale correctly on any display size now.

Let me know if anything else needs tweaking!