main: use jinja chat template system prompt by default

[CISC]

Using the new --jinja option would override the builtin system prompt with You are a helpful assistant if in conversation mode and/or no prompt was defined.

Fixed this behaviour so that -p option now either defines system prompt (in conversation mode) or user prompt, and does not fill in a default so that the chat template's default is used instead.

Adds some extra safety checks to be able to process an interactive user prompt with no defined system prompt.

@ochafik PTAL

---

No system prompt:

./build/bin/llama-cli -m phi-4-IQ2_M.gguf

 - Not using system message. To change it, set a different value via -sys PROMPT

> hi
Hello! How can I assist you today?

Incorrect use -p

./build/bin/llama-cli -m phi-4-IQ2_M.gguf -p test

*** User-specified prompt in conversation mode will be ignored, did you mean to set --system-prompt (-sys) instead?

 - Not using system message. To change it, set a different value via -sys PROMPT
...

Correctly using system prompt:

./build/bin/llama-cli -m phi-4-IQ2_M.gguf -sys "Your name is Sydney"

systemYour name is Sydney


> what is your name
My name is Sydney. How can I assist you today?

[ngxson]

now either defines system prompt (in conversation mode) or user prompt

From UX perspective, this is very confusing for end-user. I would suggest that we either:

• Simply remove default system prompt if jinja is set
• Or, add a dedicated argument for system prompt, for example -sp, --system-prompt

[CISC]

now either defines system prompt (in conversation mode) or user prompt
From UX perspective, this is very confusing for end-user. I would suggest that we either:

Perhaps, but it is already doing this, just wrongly. :)

* Or, add a dedicated argument for system prompt, for example `-sp, --system-prompt`

Makes sense, but maybe in a different PR?

[ngxson]

Makes sense, but maybe in a different PR?

Yes and it would be better if you we can merge that PR (adding -sp, --system-prompt) before merging this one.

[CISC]

Makes sense, but maybe in a different PR?
Yes and it would be better if you we can merge that PR (adding -sp, --system-prompt) before merging this one.

Sure, I'll take a look.

[CISC]

@ngxson See #12131 (-sp was already taken).

[CISC]

Failing tests seems to just be server outage.

[ngxson]

I'll test this with Phi-4 a bit later

[ngxson]

Ok that works, here is my test command + result (leaving it here for visibility):

No system prompt:

./build/bin/llama-cli -m phi-4-IQ2_M.gguf

 - Not using system message. To change it, set a different value via -sys PROMPT

> hi
Hello! How can I assist you today?

Incorrect use -p

./build/bin/llama-cli -m phi-4-IQ2_M.gguf -p test

*** User-specified prompt in conversation mode will be ignored, did you mean to set --system-prompt (-sys) instead?

 - Not using system message. To change it, set a different value via -sys PROMPT
...

Correctly using system prompt:

./build/bin/llama-cli -m phi-4-IQ2_M.gguf -sys "Your name is Sydney"

systemYour name is Sydney


> what is your name
My name is Sydney. How can I assist you today?

[CISC]

@ngxson I'll make a followup PR to add template formatting in non-conversation mode, and combined use of -sys and -p together.