Marten Files

Marten 9.18.0 focuses on raw-JSON streaming endpoints for ASP.NET Core, server-side LINQ Select() projection, and continued event-store observability work.

ASP.NET Core streaming & pagination

• StreamPaged<T> — stream a paged JSON envelope (pageNumber/pageSize/totalItemCount/pageCount/hasNextPage/hasPreviousPage/items) in a single round trip via a count(*) OVER() window column (#5014). Test coverage hardened to pin the camelCase wire contract, page-past-end behavior, and filtered totals (#5028).
• StreamPagedByCursor<T> — keyset ("seek") pagination that costs the same regardless of depth, using an opaque continuation cursor (#5016). Now streams the raw, already-persisted data column byte-identical to StreamMany/StreamPaged (no hydrate + re-serialize) by reading the next cursor's ORDER BY key values off the same reader; a malformed client-supplied cursor now returns a clean 400 instead of a 500 (#5033).
• ETag / If-None-Match (304) conditional-request support on StreamOne<T> and StreamAggregate<T> (#5015). StreamOne<T> now reads the document's mt_version inline in the same single round trip (no follow-up metadata query), and the where T : notnull constraint tightening was reversed (#5030).

LINQ

• Simple Select() projections (x => new Dto { A = x.A, B = x.Nested.B }) now translate to a server-side jsonb_build_object(...) expression that is streamable as raw JSON, instead of hydrating the full document and projecting on the client (#5017). Value-preserving conversions — widening numerics (int→long/decimal), boxing to object, nullable wrapping, enum→integral under EnumStorage.AsInteger — stay translatable and streamable; only lossy/computed conversions fall back (#5032).
• DCB tag operators usable in Where() over events (#5004).
• AggregateToMany() LINQ operator — run an event query through a multi-stream projection (#5003).

Event store, projections & daemon

• Marten.TimescaleDB extension — projection + document hypertables (#4995).
• Extended-progression telemetry: batched per-flush heartbeat writes (#5008); fixed a shutdown telemetry race in extended_progression_batch_write (#5023); running_on_node write-path regression coverage (#5001 / [#5007]). The cross-repo running_on_node population under Wolverine-managed distribution is completed via JasperFx 2.34.0 + Wolverine.
• Tenant-scoped event/tag explorer reads — ReadStreamAsync / GetRecentStreamsAsync overrides honor tenancy (#5020, [#5025]), plus a MultiStreamProjection stepthrough via the instrumented fold in EventStoreExplorer (#5002).
• HighWaterHealthCheck scoped to owned databases, with per-tenant and ExternallyManaged daemon support (#4992).
• Surface JasperFx's application-assembly-reuse warning (GH-3521) at startup (#5000).

Multi-tenancy & infrastructure

• Token-capable maintenance connection for tenant database provisioning (#5006).
• Docs: connecting to Azure Database for PostgreSQL with Entra ID / managed identity (#4993).

Dependencies

• JasperFx / JasperFx.Events 2.34.0, Weasel 9.17.0.

Full changelog: https://github.com/JasperFx/marten/compare/V9.17.0...V9.18.0