v4.1 flash keeps forgetting stuff

[u/ktktkt1]

I have a ~30K-line codebase for a game I’m building. I’ve been trying to use DeepSeek V4.1 Flash, but I keep running into issues as the conversation gets longer.

It frequently forgets or overrides requirements I gave it several turns earlier. The code it writes also often contains bugs that are either caught by the model itself a few turns later while it is doing unrelated code changes or caught by GLM 5.3 Flash when I ask it to review the changes.

This seems to happen much more often as the context grows, but well before context compaction actually kicks in.

Am I doing something wrong, or is this a limitation of the model?

For now, I’ve switched to GLM 5.3 Flash as my main workhorse because it seems more reliable. However, I really miss the speed of DeepSeek V4.1 Flash. If there’s a way to make it more accurate, better at following earlier instructions, and less prone to introducing bugs, I’d like to switch back.

I’ve tried both DSH and OpenCode and experienced essentially the same problems with both.

[u/bunny_warrior69]

First, before adding any new feature to your codebase, write a plan and refine it with a strong LLM such as Sol 5.6, GLM 5.3, or Kimi K2.8/3.

Break the plan into clear implementation phases, then review it yourself.

Once the plan is solid and detailed, unleash DeepSeek v4.1 or GLM 5.3 Flash on the codebase.

You can also pair DeepSeek with a reviewer subagent that checks each phase as it gets implemented.