fix(corpus): camelCase dateStart/dateEnd dual-accept + obs_type key routing

Two defects in build_corpus path silently narrowed result sets:

1. CorpusRoutes destructured only snake_case (date_start, date_end) from the
   request body, but the MCP tool surface advertises camelCase
   (dateStart, dateEnd). Zod's .passthrough() let the unknown keys through
   but the handler never read them — date filters were silently dropped.
   Fix: declare both casings in the Zod schema and read either at the
   destructure site.

2. CorpusBuilder set searchArgs.type = filter.types.join(',') — but `type`
   is the search-router discriminator (observations|sessions|prompts),
   NOT the observation-type filter. Passing 'bugfix,decision' to that key
   matched zero rows; a downstream array hydrate masked the failure and
   returned only entries that survived a different filter pass.
   Fix: route the joined types through searchArgs.obs_type (the correct
   observation-type filter key).

Author: Kirchlive

src/services/worker/http/routes/CorpusRoutes.ts

@@ -49,6 +49,11 @@ const buildCorpusSchema = z.object({
   query: z.string().optional(),
   date_start: z.string().optional(),
   date_end: z.string().optional(),
+  // Dual-accept: the MCP tool surface advertises camelCase (dateStart/dateEnd).
+  // Without these declarations Zod's .passthrough() keeps the camelCase keys on
+  // the body but the snake_case destructure below never reads them.
+  dateStart: z.string().optional(),
+  dateEnd: z.string().optional(),
   limit: positiveIntegerLike,
 }).passthrough();
 
@@ -79,17 +84,20 @@ export class CorpusRoutes extends BaseRouteHandler {
   }
 
   private handleBuildCorpus = this.wrapHandler(async (req: Request, res: Response): Promise<void> => {
-    const { name, description, project, types, concepts, files, query, date_start, date_end, limit } =
-      req.body as z.infer<typeof buildCorpusSchema>;
+    const body = req.body as z.infer<typeof buildCorpusSchema>;
+    const { name, description, project, types, concepts, files, query, limit } = body;
+    // Accept either casing — internal filter stays snake_case.
+    const dateStart = body.date_start ?? body.dateStart;
+    const dateEnd = body.date_end ?? body.dateEnd;
 
     const filter: CorpusFilter = {};
     if (project) filter.project = project;
     if (types && types.length > 0) filter.types = types as CorpusFilter['types'];
     if (concepts && concepts.length > 0) filter.concepts = concepts;
     if (files && files.length > 0) filter.files = files;
     if (query) filter.query = query;
-    if (date_start) filter.date_start = date_start;
-    if (date_end) filter.date_end = date_end;
+    if (dateStart) filter.date_start = dateStart;
+    if (dateEnd) filter.date_end = dateEnd;
     if (limit !== undefined) filter.limit = limit;
 
     logger.info('SEARCH', 'Building corpus', { name, project, filterKeys: Object.keys(filter) });

src/services/worker/knowledge/CorpusBuilder.ts

@@ -39,7 +39,11 @@ export class CorpusBuilder {
 
     const searchArgs: Record<string, unknown> = {};
     if (filter.project) searchArgs.project = filter.project;
-    if (filter.types && filter.types.length > 0) searchArgs.type = filter.types.join(',');
+    // `type` is the search-router discriminator (observations|sessions|prompts).
+    // For observation-type filtering use `obs_type`. Passing the comma-joined
+    // observation types to `type` silently collapses the result set (only the
+    // first type survives the downstream WHERE).
+    if (filter.types && filter.types.length > 0) searchArgs.obs_type = filter.types.join(',');
     if (filter.concepts && filter.concepts.length > 0) searchArgs.concepts = filter.concepts.join(',');
     if (filter.files && filter.files.length > 0) searchArgs.files = filter.files.join(',');
     if (filter.query) searchArgs.query = filter.query;