How do you monitor whether your investment thesis is still valid after buying a stock?

I realized that most of my investment work happens before buying a stock. Once I buy it, I mostly monitor price movements and earnings.

But price is not the thesis.

For example:

For Vertiv (VRT), the thesis might depend on hyperscaler capex and AI data center growth.

For Circle (CRCL), the thesis may depend on USDC adoption and interest rates.

I'm curious:

How do you monitor whether your thesis is still intact?

What signals would make you sell?

Do you use any tools for this today?

I feel that most tools show prices and news, but not whether the underlying drivers have changed.