3 Commits

Author	SHA1	Message	Date
rob thijssen	c8bcaabc38	fix(neuron): render HF chat templates via minijinja pycompat ... The Qwen3.6 chat_template.jinja (now loaded after the precedence fix) failed to render in minijinja: it uses Python str methods (content.startswith/endswith/split/rstrip/lstrip) and the raise_exception global that HF transformers patches into its Jinja env but minijinja doesn't provide. The render error tripped the text-only fallback, so image requests still produced zero <|image_pad|> tokens. Wire the standard bridge into render_chat_template: - minijinja-contrib `pycompat::unknown_method_callback` supplies the Python string/list/dict methods; - a `raise_exception` global maps to a render error (so malformed inputs — e.g. an image in a system message — surface cleanly). Add the real Qwen3.6-27B chat_template.jinja (verbatim from beast's HF cache) as a test fixture and assert it renders one <|image_pad|> for a text+image turn — the end-to-end check that would have caught this before deploy. Refs #16 / TP-vision. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-04 16:32:23 +03:00
rob thijssen	7ad56c6a86	fix(neuron): load chat_template.jinja (transformers precedence) ... The chat-template loader only read the `chat_template` field from tokenizer_config.json. Qwen3.6-27B ships its vision-aware template *only* in a standalone `chat_template.jinja` (and has no tokenizer_config.json at all), so the loader returned None and image requests fell back to the text-only format_qwen3_prompt — rendering zero `<|image_pad|>` tokens and tripping "expand_image_pad_tokens: prompt has 0 image_token_id occurrences". load_chat_template_alongside now follows HF transformers precedence: standalone chat_template.jinja → chat_template.json → the chat_template field in tokenizer_config.json. Tests cover the precedence, the text-only fallback, and that an OpenAI image_url content part renders `<|image_pad|>` through the real template condition (`'image_url' in item`). Refs #16 / TP-vision. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-04 16:25:30 +03:00
rob thijssen	cb303832bc	feat(neuron): render the model's chat_template with chat_template_kwargs ... Closes #9. Replaces the hardcoded `format_qwen3_prompt` ChatML glue with `minijinja`-driven rendering of the model's own `chat_template` from `tokenizer_config.json`. The request's `chat_template_kwargs` flow into the Jinja context so model-specific levers (Qwen3's `enable_thinking: false`, etc.) actually take effect. ## Implementation - New `harness::chat_template` module with three entry points: - `load_chat_template_alongside(tokenizer_json_path)` — probes `tokenizer_config.json` in the same hf-hub snapshot directory. Supports both the canonical string-form `chat_template` and the array-form some tokenizers ship (multi-template models). - `render_chat_template(template, messages, tools, kwargs)` — renders via `minijinja`. Messages flatten into the `[{role, content}]` shape HF templates iterate, with per-message extras (`tool_calls`, `tool_call_id`) preserved. `tools` and `kwargs` add into the Jinja context so templates that reference them work without us interpreting their shape. - `chat_templates_enabled()` reads `NEURON_USE_CHAT_TEMPLATE` (default true). Falsy values force the fallback path everywhere — a kill switch for emergency rollback without a rebuild. - `LoadedModel.chat_template: Option<String>` and the TP equivalent are populated once at load time. `None` (no tokenizer_config.json, parse error, missing field) routes the fallback path silently; logs go through `tracing::debug`/`warn` per condition. - New `build_prompt_for_request(chat_template, request)` wraps the decision: when both the template is present AND the kill switch is off, render with kwargs from `request.extra` (looks up `chat_template_kwargs` and `tools` lazily). On render error → warn + fallback to `format_qwen3_prompt`. Wired into all four current prompt-build sites (single-GPU stream + non-stream, TP stream + non-stream). ## Dependency `minijinja = "2"` with the `builtins`, `json`, and `serde` features. Pure-Rust Jinja2 implementation, ~80KB compiled. Used internally by HF's `tokenizers-rs` for its own chat templating; the API surface we touch (`Environment::add_template` + `Template::render(serde_value)`) is stable. ## Validation strategy I can't byte-compare the new path's output against `format_qwen3_prompt` for live models without GPU (CI doesn't have one). The fallback path and kill switch are the mitigations — a deploy can flip `NEURON_USE_CHAT_TEMPLATE=false` in the neuron service env if the chat template renders surprisingly on Qwen3-8B in production. The legacy formatter stays the fail-closed default. ## Scope cuts (documented in module header) - Tool-definition lifting from helexa-acp's system-prompt injection into the chat_template's native tools block is deferred. Today the request's `tools` array threads into the Jinja context, but helexa-acp continues to inject Hermes-format tool descriptions into the system prompt for backwards-compat with non-cortex endpoints. ## Tests 9 unit tests in `chat_template`: kill-switch matrix (truthy / falsy / unset), template loading (string form, array form, missing file, unparseable JSON, missing field), rendering (basic conversation threading, kwargs forwarding, message-extras threading for tool_calls). 215 workspace tests pass; clippy + fmt clean across all workspace features (default). Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>	2026-05-31 23:43:11 +03:00