Redis cacheHandlers for cacheComponents

[Haaxor1689]

Summary

So I've written a custom cache handler for cacheComponents that connects to a Redis instance. It's using Bun's Redis client and a bit more granular keys than the simple Redis example in NextJs docs. It works well, apart from few edge cases.

1. When calling "use cache" functions in route handlers, they sometimes just crash (error below). I'm calling the same cached function from both RSC context and route handler context, RSC one always works, route handler crashes when the content it loads is already cached. This crash is also pretty inconsistent, while trying to debug it, it sometimes works based on when I cleared the cache and where it's cached from. Solved
2. Some cache keys always miss, even though given cache key is in Redis. This does not seem to be the case in production build or at least when I enable logging. My only clue is that it might be caused by a constant [Fast Refresh] rebuilding spam when running in dev mode.

I've spent hours trying to debug this issue with absolutely no luck. Tried stable NextJs 16.0.7, 16.1.0 canary releases 2, 10, 12, 15 and also changing Bun's redis to node-redis. None of it helped.

Additional information

Exception thrown when reading cached function from a route handler

2025-12-06 12:45:51.936 | [ERROR] Route exception: TypeError: null is not an object (evaluating 't.reason.enqueueModel')
2025-12-06 12:45:51.936 |     at Q (.next/server/chunks/_cca5445b._.js:1:10573)
2025-12-06 12:45:51.936 |     at eR (.next/server/chunks/_cca5445b._.js:1:23345)
2025-12-06 12:45:51.936 |     at <anonymous> (.next/server/chunks/_cca5445b._.js:1:24678)
2025-12-06 12:45:51.936 |     at eT (.next/server/chunks/_cca5445b._.js:1:24703)
2025-12-06 12:45:51.936 |     at t (.next/server/chunks/_cca5445b._.js:1:25559)

Example

https://gist.github.com/Haaxor1689/55e9afd3409030211315fc80db6db462

[icyJoseph]

Some cache keys always miss, even though given cache key is in Redis. This does not seem to be the case in production build or at least when I enable logging. My only clue is that it might be caused by a constant [Fast Refresh] rebuilding spam when running in dev mode.

Could this be because the HMR refresh hash (development only) - Invalidates cache on hot module replacement?

Not really sure what could be happening with issue 1 though.

[Haaxor1689]

It only works in node runtime, bun has it's own --inspect flag but no clue how to run a next dev command with it.

bun --bun --inspect dev
bun --bun  dev --inspect

Neither of these work

[icyJoseph]

I just did bun dev --inspect and I was able to debug through the chrome dev tools

[Haaxor1689]

You need to do bun --bun dev otherwise it's not using bun runtime but node

[icyJoseph]

Aha I see - 🤔 uff I Get a lot of errors now -

Could bun be the issue in your case though? Have you tried with node?

[Haaxor1689]

I can't really switch my project to node because I use a bunch of bun features server side. I'll go with stripping a page to naked shell and try slowly adding features and see when it starts to go crazy with fast reloads. But thank you so much for you time :) I'll post an update if I figure out the case. This issue seems to be related to mine (although I'm not getting 404s) but changing to different versions doesn't help sadly.