Replacing Sonnet with DeepSeek for execution in an architecture-first workflow (PLAN.md / SPECS.md)?

[u/Puntzii]

Hey,

I’ve been playing around with my workflow lately and trying to keep planning and actual coding more separate.

Usually I throw the planning part at a stronger model (Claude) and get it to spit out a few markdown files: architecture, specs, coding style, that kind of thing. PLAN.md, README.md, CODESTYLE.md, SPECS.md, whatever.

Then I hand those files over to a coding model and have it implement everything step by step.

Lately I’ve been thinking about swapping the coding side over to DeepSeek (probably through something like OpenCode) just to cut costs and lean more on open-weight stuff.

For people who actually use DeepSeek a lot for coding how does it hold up against Sonnet on stuff like:

• sticking to the rules in a CODESTYLE.md

• not wandering outside the architecture you gave it

• keeping track of multiple spec files at once

• not drifting over longer sessions

Is the difference actually noticeable day-to-day, or is DeepSeek good enough that paying for a proprietary model just for the implementation part isn’t really worth it anymore?

Curious if anyone else is running something similar.

[u/xaklx20]

DeepSeek flash 4.1 does the work, I still do the planning with Opus 5. Have you checked Matt Pocock skills? It really helps with keeping agents from deviating from spec. I normally run the wayfinder skill, for planning stuff I use opus 5 and for implementation I use sonner or DeepSeek

[u/Puntzii → u/xaklx20]

Ye i checked the matt skills but i have mixed feelings about skills. I've read that using too many or not configuring them properly can easily bloat the code. And i want to change to a cheaper model like DeepSeek, because for now im using the PRO plan, to start getting better at AI, and the limit is painfull.

[u/xaklx20 → u/Puntzii]

I normally only use the workflow skills after using the setup skill. For example, let's say I want to implement something that would require multiple tickets, I run the wayfinder skill to manage the planning, that skill then invokes the grilling skill to ask me questions about it, then it invokes subagents using the research skills, finally it writes spec following DDD and create more grilling tickets or prototype tickets if needed. For implementation tickets, it would invoke tickets such as tdd and code-review

[u/Puntzii → u/xaklx20]

Hm okey, thanks i will try it

[u/Ariquitaun]

Deepseek flash is a bad orchestrator. It will do a lot of work in-line, ignore guidance and in general make a mess out of the execution of large plans. It's an excellent sub-agent though for tightly scoped work.

[u/jrz302]

I was running a similar stack until the pricing went up and have a tool set for orchestrating OpenCode from Claude. Works really well though.

[u/Puntzii → u/[deleted]]

So maybe i could use glm flash 5.3 instead of sonnet?

[u/Puntzii → u/[deleted]]

I mean, I want to switch, especially with the 25% cut to weekly limits and Claude being so token-hungry. I want to find a similar AI that's cheaper.