Dutch case law and legislation search via rechtspraak.nl and wetten.overheid.nl

Jeroen1991z adds native search across the Dutch legal corpus: four new tools give the LLM access to rechtspraak.nl judgments, BWB legislation, and individual article text. The diff includes a significant amount of API-wrangling to get the external endpoints to actually return useful data.

searchi18n

A new backend/src/lib/rechtspraak.ts is the core of this change. It exposes four functions that become LLM tools: search_case_law (rechtspraak.nl Atom/XML, ECLI results), fetch_case_law (full judgment text by ECLI), search_legislation (wetten.overheid.nl SRU, finds laws by title), and fetch_legislation_article (fetches individual articles by BWB ID and article number via the BWB XML repository).

Getting the external APIs to work correctly took most of the commits. The case law search initially used subject as the keyword parameter; the actual parameter is zoekterm. The legislation SRU endpoint required version=1.2, a switch from title any to overheidbwb.titel any, and dropping the dcx record schema. The XML parser was then wrong because the real response used <record> not <srw:record>, and rechtsgebied instead of description. The tool description for search_legislation was also corrected to make explicit that it searches law titles not article content - so the right query is Burgerlijk Wetboek Boek 6, not onrechtmatige daad.

The citation schema gains ecli, court, judgment_date, article, and r.o. (rechtsoverweging) fields. formatCitationPage is rewritten so case law renders r.o. X, legislation renders the article reference, and documents render pagina N - fixing a "Page undefined" bug that existed in the upstream.

A sources dropdown appears in ChatInput.tsx with toggles for Rechtspraak.nl and Wetten.overheid.nl. A Memorie van Toelichting (MvT) source and an "AI kennis" override were added and then removed; what's left is searchSources: { rechtspraak?: boolean; wetten?: boolean } threaded through the API and routes.

One bundled change worth noting: the first commit in this topic (7711127a) also flips the default chat model from gemini-2.0-flash-preview to claude-sonnet-4-6. If you take that commit, you're taking the model default change too.

So what Worth a look if you're building for a Dutch-market audience. The API clients are functional after the fix commits, but they were clearly developed by trial and error against live endpoints - re-validate the parsers when you pick this up, as the upstream SRU and XML formats have shifted before and will again.

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Spotted something wrong? Or know the PR text has fresher detail than the writeup above?

Commits in this thread

11 commits from Jeroen1991z/mikeNL, oldest first. Source extracted verbatim from the harvested git log.

SHA	Subject	Author	Date
`7711127a`	Add Dutch legal market integrations: rechtspraak.nl + wetten.overheid.nl	Claude	2026-05-04	↗ GitHub
commit body - New `backend/src/lib/rechtspraak.ts`: API client for Dutch case law (rechtspraak.nl Atom/XML) and legislation (wetten.overheid.nl SRU), with court code → name mapping and full-text extraction capped at 15 kB. - `chatTools.ts`: Three new agentic tools (search_case_law, fetch_case_law, search_legislation) registered in RECHTSPRAAK_TOOLS; handlers in runToolCalls emit SSE activity events; runLLMStream accepts `rechtspraakEnabled` param (default ON); ParsedCitation/normalizeCitation/ extractAnnotations extended for case_law and legislation citation types; system prompt extended with Dutch law search strategy and citation format. - `chat.ts` / `projectChat.ts`: Accept `rechtspraak_enabled` from request body. - `llm/models.ts`: Claude Sonnet 4.6 is now the default model for chat, tabular review, and title generation. - `types.ts`: New AssistantEvent variants for case law / legislation activity; MikeCitationAnnotation extended with ecli, external_url, court, judgment_date, title, article optional fields; MikeMessage gains `rechtspraakEnabled`. - `mikeApi.ts`: `rechtspraak_enabled` added to streamChat / streamProjectChat. - `useAssistantChat.ts`: Pass rechtspraakEnabled through to API; handle four new SSE event types with streaming placeholders and thinking indicator. - `ChatInput.tsx`: Scale icon toggle button (default ON) for rechtspraak.nl lookup. - `AssistantMessage.tsx`: Render case_law_searched_start/searched, case_law_fetched, legislation_searched event blocks with blue dot indicators. - `ChatView.tsx`: Citation click opens external URL in new tab when citation.external_url is set (case law / legislation), otherwise opens the document side panel as before. - `ModelToggle.tsx`: DEFAULT_MODEL_ID changed from gemini-3-flash-preview to claude-sonnet-4-6. https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex
`0eba5bc1`	Fix rechtspraak.nl search: use zoekterm param for keyword search	Claude	2026-05-04	↗ GitHub
The open data API uses zoekterm for full-text search, not subject. The subject parameter is for URI-based taxonomy filtering only. https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex
`dc55a874`	Fix wetten.overheid.nl legislation search	Claude	2026-05-04	↗ GitHub
commit body - Add required version=1.2 SRU parameter - Use correct BWB index overheidbwb.titel instead of unsupported title/text - Remove unsupported dcx recordSchema (use default) - Update XML parsing to use dcterms: namespace https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex
`177826a6`	Fix legislation XML parser for actual BWB response format	Claude	2026-05-04	↗ GitHub
Response uses <record> not <srw:record>, and has rechtsgebied not description. Also deduplicate results by BWB ID since the API returns multiple versions of the same law. https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex
`633dd8d2`	Add per-source search toggles and Memorie van Toelichting search	Claude	2026-05-04	↗ GitHub
commit body - Add searchMvT function querying SGD (Staten-Generaal Digitaal) via SRU - Split RECHTSPRAAK_TOOLS into CASE_LAW_TOOLS, LEGISLATION_TOOLS, MVT_TOOLS - Add searchSources param to runLLMStream for per-source control - Inject Dutch-only instruction when internet/AI knowledge is disabled - Replace single rechtspraak button with Bronnen dropdown in ChatInput showing toggles for rechtspraak.nl, wetten.overheid.nl, MvT, and AI kennis - Wire searchSources through frontend types → mikeApi → route handlers https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex
`b1507b3b`	Fix legislation search tool description: clarify it searches law titles	Claude	2026-05-04	↗ GitHub
commit body The overheidbwb.titel index searches law titles, not article content. Guide the AI to search by law name (e.g. 'Burgerlijk Wetboek Boek 6') rather than by topic keywords like 'onrechtmatige daad'. https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex
`adcbdc67`	Add fetch_legislation_article tool to read specific BW articles	Claude	2026-05-04	↗ GitHub
commit body - Add fetchLegislationArticle() that fetches BWB XML via manifest or locatie_toestand URL, then extracts article text by number - Store xml_url (latest version) in LegislationResult from search - Deduplicate search results keeping the newest version's XML URL - Add fetch_legislation_article tool to LEGISLATION_TOOLS - Add tool handler in runLLMStream https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex
`a8ea2cc9`	Remove MvT and internet-toggle sources; simplify search to rechtspraak + wetten	Claude	2026-05-05	↗ GitHub
commit body The Memorie van Toelichting source is removed from backend tools and frontend UI. The "Eigen kennis AI" toggle is also removed - the AI always uses its own training. The sources dropdown button is gone entirely; rechtspraak.nl and wetten.overheid.nl are now always enabled and hardcoded on submit. https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex
`cec09de7`	Restore sources dropdown with only rechtspraak.nl and wetten.overheid.nl	Claude	2026-05-05	↗ GitHub
Both sources are on by default and user-toggleable. MvT and internet toggle remain removed. https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex
`cfd7ce74`	Improve case law and legislation citations	Claude	2026-05-05	↗ GitHub
commit body - Add r.o. (rechtsoverweging) field to case law citations; system prompt instructs model to fill it from fetched judgment text - Fix formatCitationPage: show "r.o. X" for case law, article ref for legislation, pagina N for documents - eliminating "Page undefined" - System prompt: place citation marker directly after the legal reference (after "BW"/"Rv"), not after "geldt dat" - System prompt: instruct model to use URL from fetch_legislation_article (which now includes today's date) rather than constructing its own - fetchLegislationArticle: include current date in returned URL https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex
`89f5a7fc`	Remove mvt and internet from search_sources type in mikeApi	Claude	2026-05-05	↗ GitHub
Aligns frontend type with the simplified SearchSources that only supports rechtspraak and wetten. https://claude.ai/code/session_016JxWnFc3baeDgkzDgxY6ex

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