### What problem does this PR solve?
This PR adds support for parsing PDFs through an external Docling
server, so RAGFlow can connect to remote `docling serve` deployments
instead of relying only on local in-process Docling.
It addresses the feature request in
[#13426](https://github.com/infiniflow/ragflow/issues/13426) and aligns
with the external-server usage pattern already used by MinerU.
### Type of change
- [ ] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [x] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):
### What is changed?
- Add external Docling server support in `DoclingParser`:
- Use `DOCLING_SERVER_URL` to enable remote parsing mode.
- Try `POST /v1/convert/source` first, and fallback to
`/v1alpha/convert/source`.
- Keep existing local Docling behavior when `DOCLING_SERVER_URL` is not
set.
- Wire Docling env settings into parser invocation paths:
- `rag/app/naive.py`
- `rag/flow/parser/parser.py`
- Add Docling env hints in constants and update docs:
- `docs/guides/dataset/select_pdf_parser.md`
- `docs/guides/agent/agent_component_reference/parser.md`
- `docs/faq.mdx`
### Why this approach?
This keeps the change focused on one issue and one capability (external
Docling connectivity), without introducing unrelated provider-model
plumbing.
### Validation
- Static checks:
- `python -m py_compile` on changed Python files
- `python -m ruff check` on changed Python files
- Functional checks:
- Remote v1 endpoint path works
- v1alpha fallback works
- Local Docling path remains available when server URL is unset
### Related links
- Feature request: [Support external Docling server (issue
#13426)](https://github.com/infiniflow/ragflow/issues/13426)
- Compare view for this branch:
[main...feat/docling-server](https://github.com/infiniflow/ragflow/compare/main...spider-yamet:ragflow:feat/docling-server?expand=1)
##### Fixes [#13426](https://github.com/infiniflow/ragflow/issues/13426)
### What problem does this PR solve?
The _transfer_to_sections method was throwing a type hint violation
because it occasionally returns 3-item tuples instead of 2. Adjusted to
list[tuple[str, ...]] to prevent runtime crashes.
Error:
20:53:21 Page(1~10): [ERROR]Internal server error while chunking:
Method[1m[35m
deepdoc.parser.docling_parser.DoclingParser._transfer_to_sections()[0m
return [1m[31m[(1. JIRA Nasıl Kullanılır?, text,
@@1\t70.8\t194.9\t70.9\t85.5##), (1.1. Proje O...##)][0m violates type
hint [1m[32mlist[tuple[str, str]][0m, as [1m[33mlist [0mindex
[1m[33m15[0m item tuple [1m[33mtuple [0m[1m[31m(Gelen ekran
üzerinden alanları isterlerine göre doldurduğunuz taktirde Create
düğmesi i...##)[0m length 3 != 2.
20:53:21 [ERROR][Exception]: Method[1m[35m
deepdoc.parser.docling_parser.DoclingParser._transfer_to_sections()[0m
return [1m[31m[('1. JIRA Nasıl Kullanılır?', 'text',
'@@1\t70.8\t194.9\t70.9\t85.5##'), ('1.1. Proje O...##')][0m violates
type hint [1m[32mlist[tuple[str, str]][0m, as [1m[33mlist [0mindex
[1m[33m15[0m item tuple [1m[33mtuple [0m[1m[31m('Gelen ekran
üzerinden alanları isterlerine göre doldurduğunuz taktirde Create
düğmesi i...##')[0m length 3 != 2.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
Co-authored-by: Enes Delibalta <enes.delibalta@pentanom.com>
### What problem does this PR solve?
Feat: add more chunking method #11311
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Fix: manual parser with mineru #11320
Fix: missing parameter in mineru #11334
Fix: add outlines parameter for pdf parsers
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
### What problem does this PR solve?
change:
“After each dialogue turn, the agent component’s output is not reset.”
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
### What problem does this PR solve?
issue:
#3945
change:
add Docling parser
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
