Fix DeepSeek4 crafted template

[pwilkin]

Overview

It seems like I've been a bit lazy implementing the DS4 template. I used the standard behavior (retain last reasoning trace). However, the reference behavior is different. DS4 will retain all reasoning traces in one of two cases:

• if drop_reasoning is set to false
• in case the message history contains at least one tool call

I've patched the template and added a test to verify this.

Additional information

Note that under the current behavior llama.cpp defaults to setting drop_reasoning to true, so if you want it set to false you'll have to add --preserve-reasoning - not that it matters that much because for all agentic cases, DS4 will still force the retain of traces due to the presence of tool calls.

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: Yes, a bit of GLM-5.2 and Claude to make the tests (funny thing: GLM-5.2 tripped on reading stuff that contained <think> and </think> :))

[aldehir]

If we want to start testing templates, probably best to move those to a separate test suite as this one is already pretty large.

IMO Python tests are more appropriate for the Jinja templates.

[pwilkin]

Yeah, I'll probably move to refactor test-chat.cpp in a followup PR.

Personally, I'm against Python tests because the C++ tests double down as a check on the template rendering / message passing, which Python won't do - I prefer the tests to run inside the same engine as the actual template processing.

[tarruda]

As I had explained in the reddit thread, this is not the only issue and I had to opt out of the autoparser in order to properly run DSV4. In particular, parallel tool calling is not working with the autoparser and while running on pi I was getting random stops with tool calls within the reasoning block.

Everything done to fix are contained in these two commits sent to fairydreaming's lightining indexer branch: fairydreaming#4

[pwilkin]

@tarruda yeah, working on the parser extension next :)

[aldehir]

@tarruda can you please include your response from Reddit for visibility purposes. Also because the link appears broken on my end.

[pwilkin]

This is basically pretty similar to @tarruda 's branch :) a few style differences.

@tarruda technically your approach to the template flag isn't in line with the reference: they require reasoning traces not if tools are declared, but if any tool calls are actually present (I know, practically it doesn't really matter too much, but just nitpicking :))

[tarruda]

@aldehir https://old.reddit.com/r/LocalLLaMA/comments/1une2il/i_merged_fixes_for_quantized_kv_cache_into_my/ovuun8r/