[$500] [Due for payment 2025-11-10] [Tracking] Improve the bottom tab switching

[mountiny]

This is to track various approaches to improve bottom tab switching. We can see that currently, especially as accounts become larger, switching between the bottom tabs from Inbox to Reports is slow.

These delays lead to user frustration, especially when users frequently switch between tabs and use the app often, making the delay clearly noticeable.

From past investigations, the pages are heavy to render, which leads to delays.

Let's systematically:

• Drive these delays down so we can ensure switching between all the bottom tabs feels instant, as you would expect for any other native app
• Put automated tests and reassure performance tests in place to guardrail from performance regressions for important methods in these flows
• Identify patterns in the code that are leading to extra rendering work and performance degradation and propose how to prevent those in other places of the codebase, either with ESLint rule or with AI Reviewer rules
• Implement metrics and guardrails in Sentry or similar tool so we can measure how long switching between bottom tabs takes

Coming from this thread https://expensify.slack.com/archives/C05LX9D6E07/p1759244556002359?thread_ts=1759240468.058169&cid=C05LX9D6E07

cc @adhorodyski @staszekscp

Issue Owner

Current Issue Owner: @

Upwork Automation - Do Not Edit

• Upwork Job URL: https://www.upwork.com/jobs/~021999509364288964530
• Upwork Job ID: 1999509364288964530
• Last Price Increase: 2025-12-12

[melvin-bot]

Triggered auto assignment to @trjExpensify (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details. Please add this bug to a GH project, as outlined in the SO.

[trjExpensify]

Do you need BZ on this if it's a tracking issue?

[sumo-slonik]

I’d be happy to help with the investigation of this topic and see what I can find.

[mountiny]

@sumo-slonik thanks! Can you please make holistic plan of how to tackle the improvements here? cc @kacper-mikolajczak for help too

[kacper-mikolajczak]

@mountiny Adding to your already comprehensive list of improvements we will undertake, what is the approach to e2e tests? For example, measuring most critical parts of the app like Inbox -> Reports tab transition. Would that be a part of automated tests initiative you've mentioned or are we talking only about synthetic tests?

[sumo-slonik]

@sumo-slonik thanks! Can you please make holistic plan of how to tackle the improvements here? cc @kacper-mikolajczak for help too

Before we dive into the detailed tasks, I want to start an investigation in the Profiler to assess the performance of navigation between tabs using the bottom tab switching. This will help us identify areas with potential for improvement. Once we know which areas could benefit from enhancements, we can define specific improvement tasks and then focus on determining how to test whether any new PRs might affect performance in this area.

[kacper-mikolajczak]

Same here @sumo-slonik!

What really stood out during my profiling sessions (apart from cost of list rendering) was the overhead that comes from NavigationTabBar and SearchTypeMenuPopover. During transitions they are re-rendered quite often and with their compute time hitting 50+ms each can lead up to significant delays.

I noticed that NavigationTabBar is also being mounted for each tab separately with TopNavigationTabBar on top. Constant mounting of those can be costly.

I will dive deeper as of why they are like that and what causes them to render. Let me know if you found similar issues, so we can validate they are really the parts of the root cause. Thanks!