docs/usermanuals/en/training/dpo.md: broken example — Reference SFT rows via data.extra_datasets: ["data/sft.jsonl"] if you genuinely need to mix (DOC-D3B05-013) #239

Wave 1 · theme D1-10: Documentation-only fixes · highest severity High · 1 finding(s) · effort docs fix

Summary

Following the advice crashes training.

Primary finding

DOC-D3B05-013 — docs/usermanuals/en/training/dpo.md: broken example — Reference SFT rows via data.extra_datasets: ["data/sft.jsonl"] if you genuinely need to mix

severity High

Where. docs/usermanuals/en/training/dpo.md:220 (Turkish mirror: docs/usermanuals/tr/training/dpo.md (danger box, Mixing SFT and DPO)) · type: broken example

The document says. Reference SFT rows via data.extra_datasets: ["data/sft.jsonl"] if you genuinely need to mix

What the code does. Concatenation produces union columns padded with None (data.py:512-546). A DPO run with an SFT extra dataset crashed with AttributeError 'NoneType' object has no attribute 'endswith', exit 2 (repro).

Code references. forgelm/data.py:512-546

User impact. Following the advice crashes training.

Proposed correction. Replace with: "Run SFT and DPO as separate stages (pipeline:); extra_datasets must share the DPO format."

Turkish mirror. the Turkish page has no such statement

Acceptance criteria

• Each statement is re-checked against the code at fix time.
• Documentation listed above is corrected in English and in its Turkish mirror in the same PR.
• Every finding in this issue is resolved or explicitly closed with a reason.

_{Found by the October 2026 ForgeLM code and documentation review against commit cab2947. Code links point at that commit; line numbers may have moved since. Finding IDs (CR-…, DOC-…, TECH-…) are stable references for this backlog.}