REDDIT · REDDIT// 32d agoINFRASTRUCTURE

llama.cpp tool calls break with Qwen3.5

A Reddit report says recent `llama-server` runs can still handle plain OpenAI-compatible chat with Qwen3.5, but fail on tool calls with an automatic parser-generation error tied to the Jinja chat template. Related llama.cpp GitHub issues suggest this is part of a broader pattern of Qwen tool-calling brittleness in the project’s parser and template stack rather than a simple user misconfiguration.

// ANALYSIS

This looks more like a llama.cpp tool-calling regression than a knock on Qwen itself, especially since the same setup reportedly works through Ollama.

–The reported failure happens at the parser/template layer, with `Unexpected message role` thrown while generating the tool-call parser for `/v1/responses`
–A separate March 2026 llama.cpp issue documents Qwen3.5 repeatedly failing tool calls under longer context, which points to a real ecosystem bug cluster rather than one broken local setup
–An older 2025 llama.cpp issue shows similar Qwen tool-calling trouble around Jinja templates and missing `content` keys, so this is not a brand-new edge case
–For local-agent developers, this is the painful kind of bug because basic chat still works and can hide the fact that function calling is silently degraded
–The practical takeaway is that Qwen-on-llama.cpp remains powerful, but tool use is still sensitive to template, parser, and server-version drift

// TAGS

llama-cppqwen3-5llminferenceapiagentopen-source

DISCOVERED

32d ago

2026-03-10

PUBLISHED

33d ago

2026-03-09

RELEVANCE

7/ 10

AUTHOR

chibop1