Three query-value paths change or lose the caller's values on current master (e32547ac):

• A literal @RequestLine("GET /x?ids=1,2") becomes ?ids=1&ids=2, changing one value into two parameters. A percent-encoded comma would be fine; repeated parameters are the problem. Collection expressions should still expand as before.
• @QueryMap with Map.of("ids", new int[]{1, 2}) sends an array identity such as ids=%5BI%40.... The same happens for primitive-array fields of query-map DTOs. String[] values in a query map already work.
• @RequestLine("GET /x?ids={ids}") with @Param("ids") int[] also sends the array identity; @Param String[] is affected too. This is a separate expression-expansion path from the query-map case.

I reproduced these with a recording Client and ran the regression tests using the dev profile (Java 8 main compilation and a JDK 27 test JVM). I'll prepare a focused fix with collection, scalar, empty/null-array and reserved-character controls. Existing custom Param.Expander behavior will be preserved.

The inherited-field collision candidate is outside this scope; it needs a separate decision about name precedence. No changes to #3613 or #3612 are intended.