Map NATS boundary failures to tagged errors

ts/EFFECT_NATIVE_REWRITE_AUDIT.md

@@ -12,8 +12,8 @@ Verified source roots:
 - Effect v4 subtree: `/home/elpresidank/YeeBois/projects/beep-effect2/.repos/effect-v4`
 - Installed Effect beta used by this workspace: `ts/node_modules/effect`
 
-Current signal counts from `ts/packages` after the 2026-06-02 base producer
-scoped runtime slice:
+Current signal counts from `ts/packages` after the 2026-06-02 NATS typed
+boundary slice:
 
 | Signal | Count |
 | --- | ---: |
@@ -26,13 +26,13 @@ scoped runtime slice:
 | `new Map` | 60 |
 | `toPromiseRequestor` | 0 |
 | `makeAsyncProcessor` | 19 |
-| `receive(` | 17 |
+| `receive(` | 18 |
 | `while (` | 2 |
 | `new Error` | 8 |
 | `new Promise` | 10 |
 | `JSON.parse` | 4 |
 | `localStorage` | 9 |
-| `JSON.stringify` | 7 |
+| `JSON.stringify` | 8 |
 | `setTimeout` | 4 |
 | `process.env` | 3 |
 
@@ -101,6 +101,10 @@ Notes:
   factory. Public `start`/`send`/`stop` remain Promise compatibility
   boundaries, while producer allocation, flush, and finalizer close now go
   through the Effect runtime path.
+- The NATS typed boundary slice removed the dynamic `import("nats")` header
+  path and maps header construction plus `ack()`/`nak()` failures into tagged
+  `PubSubError`s with `Effect.try`. The `receive(` and `JSON.stringify` count
+  increases are from the new mocked NATS backend test, not production code.
 - The gateway streaming callback slice added Effect-returning dispatcher
   streaming methods, switched the RPC stream server off nested
   `Effect.runPromiseWith(context)` queue offers, and replaced the client
@@ -1156,6 +1160,28 @@ Notes:
   - `cd ts && bun run build`
   - `cd ts && bun run test`
 
+### 2026-06-02: NATS Typed Boundary Slice
+
+- Status: migrated and root-verified.
+- Completed:
+  - Replaced the dynamic header import inside `makeNatsProducer` with the
+    static NATS `headers` export.
+  - Wrapped publish header construction in `Effect.try`, so invalid header
+    names/values fail as tagged `PubSubError` values instead of defects.
+  - Wrapped NATS `ack()` and `nak()` calls in `Effect.try`, preserving the
+    existing wrong-message guard and mapping thrown acknowledgement failures
+    into tagged `PubSubError`s.
+  - Added a mocked NATS backend test covering invalid publish headers and
+    thrown ack/nak failures through the public `makeNatsBackend` path.
+- Verification:
+  - `cd ts && bun run check:tsgo`
+  - `cd ts/packages/base && bunx --bun vitest run src/__tests__/nats-backend.test.ts`
+  - `bun run --cwd ts/packages/base build`
+  - `bun run --cwd ts/packages/base test`
+  - `cd ts && bun run check`
+  - `cd ts && bun run build`
+  - `cd ts && bun run test`
+
 ## Subagent Findings To Preserve
 
 - MCP/workbench:
@@ -1187,6 +1213,10 @@ Notes:
     runtime. Remaining broker P0 work should focus on native backend/NATS
     runtime shape and consumer polling, not replacing `PubSubBackend` with
     `effect/PubSub`.
+  - NATS header construction and ack/nak operations now map thrown SDK
+    failures into tagged `PubSubError`s. Remaining NATS work is selective
+    404 handling, scoped backend/layer construction, and stream/consumer state
+    ownership.
   - Existing constructor shims preserve callable-plus-newable public exports;
     removing them needs a public API split or real class redesign.
   - Typed string registries in `Flow` now have Schema-backed parameter specs
@@ -1257,6 +1287,9 @@ Notes:
   - Treat the producer Promise facade as a completed compatibility wrapper;
     avoid reopening it unless backend runtime changes require a narrower
     adapter.
+  - Keep NATS SDK boundary failures typed; future backend slices should avoid
+    catch-all create-on-failure behavior and move connection/stream state into
+    scoped Effect services.
 - Tests:
   - Fake backend ack/nak/backoff/stop tests, NATS close finalizer tests, and
     config-push stream tests.

ts/packages/base/src/__tests__/nats-backend.test.ts

@@ -0,0 +1,138 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { makeNatsBackend } from "../backend/nats.js";
+
+const natsMock = vi.hoisted(() => {
+  const encoder = new TextEncoder();
+  const decoder = new TextDecoder();
+
+  const publish = vi.fn();
+  const consumersGet = vi.fn();
+  const consumersAdd = vi.fn();
+  const streamsInfo = vi.fn();
+  const streamsAdd = vi.fn();
+  const next = vi.fn();
+  const ack = vi.fn();
+  const nak = vi.fn();
+  const drain = vi.fn();
+  const headerAppend = vi.fn();
+  const headers = vi.fn();
+  const connect = vi.fn();
+
+  return {
+    ack,
+    connect,
+    consumersAdd,
+    consumersGet,
+    decoder,
+    drain,
+    encoder,
+    headerAppend,
+    headers,
+    nak,
+    next,
+    publish,
+    streamsAdd,
+    streamsInfo,
+  };
+});
+
+vi.mock("nats", () => ({
+  AckPolicy: { Explicit: "explicit" },
+  DeliverPolicy: { All: "all", New: "new" },
+  StringCodec: () => ({
+    decode: (input: Uint8Array) => natsMock.decoder.decode(input),
+    encode: (input: string) => natsMock.encoder.encode(input),
+  }),
+  connect: natsMock.connect,
+  headers: natsMock.headers,
+}));
+
+function resetNatsMock(): void {
+  vi.clearAllMocks();
+
+  natsMock.publish.mockResolvedValue({ duplicate: false, seq: 1, stream: "tg_test" });
+  natsMock.consumersGet.mockResolvedValue({ next: natsMock.next });
+  natsMock.consumersAdd.mockResolvedValue(undefined);
+  natsMock.streamsInfo.mockResolvedValue({ config: { name: "tg_test" } });
+  natsMock.streamsAdd.mockResolvedValue(undefined);
+  natsMock.next.mockResolvedValue({
+    ack: natsMock.ack,
+    data: natsMock.encoder.encode(JSON.stringify("payload")),
+    headers: undefined,
+    nak: natsMock.nak,
+  });
+  natsMock.ack.mockReturnValue(undefined);
+  natsMock.nak.mockReturnValue(undefined);
+  natsMock.drain.mockResolvedValue(undefined);
+  natsMock.headerAppend.mockReturnValue(undefined);
+  natsMock.headers.mockReturnValue({ append: natsMock.headerAppend });
+  natsMock.connect.mockResolvedValue({
+    drain: natsMock.drain,
+    jetstream: () => ({
+      consumers: { get: natsMock.consumersGet },
+      publish: natsMock.publish,
+    }),
+    jetstreamManager: () =>
+      Promise.resolve({
+        consumers: { add: natsMock.consumersAdd },
+        streams: {
+          add: natsMock.streamsAdd,
+          info: natsMock.streamsInfo,
+        },
+      }),
+  });
+}
+
+describe("NATS backend", () => {
+  beforeEach(() => {
+    resetNatsMock();
+  });
+
+  it("maps invalid publish headers to tagged PubSubError", async () => {
+    natsMock.headerAppend.mockImplementation(() => {
+      throw "invalid header";
+    });
+    const backend = makeNatsBackend("nats://test");
+    const producer = await backend.createProducer<string>({ topic: "tg.test.topic" });
+
+    const error = await producer.send("hello", { bad: "value" }).catch((caught: unknown) => caught);
+
+    expect(error).toMatchObject({
+      _tag: "PubSubError",
+      operation: "headers:tg.test.topic",
+    });
+    expect(natsMock.publish).not.toHaveBeenCalled();
+  });
+
+  it("maps thrown ack and nak failures to tagged PubSubError", async () => {
+    natsMock.ack.mockImplementation(() => {
+      throw "ack failed";
+    });
+    natsMock.nak.mockImplementation(() => {
+      throw "nak failed";
+    });
+    const backend = makeNatsBackend("nats://test");
+    const consumer = await backend.createConsumer<string>({
+      topic: "tg.test.topic",
+      subscription: "worker",
+    });
+    const message = await consumer.receive(1);
+
+    expect(message).not.toBeNull();
+    if (message === null) {
+      return;
+    }
+
+    const ackError = await consumer.acknowledge(message).catch((caught: unknown) => caught);
+    const nakError = await consumer.negativeAcknowledge(message).catch((caught: unknown) => caught);
+
+    expect(ackError).toMatchObject({
+      _tag: "PubSubError",
+      operation: "acknowledge:tg.test.topic",
+    });
+    expect(nakError).toMatchObject({
+      _tag: "PubSubError",
+      operation: "negative-acknowledge:tg.test.topic",
+    });
+  });
+});

ts/packages/base/src/backend/nats.ts

@@ -14,7 +14,9 @@ import {
   type JetStreamClient,
   type JetStreamManager,
   type Consumer as NatsJsConsumer,
+  headers,
   type JsMsg,
+  type JetStreamPublishOptions,
   StringCodec,
   AckPolicy,
   DeliverPolicy,
@@ -78,6 +80,25 @@ function makeNatsProducer<T>(
   subject: string,
   schema?: S.Codec<T, unknown>,
 ): BackendProducer<T> {
+  const makePublishOptions = (
+    properties: Record<string, string> | undefined,
+  ): Effect.Effect<Partial<JetStreamPublishOptions>, ReturnType<typeof pubSubError>> => {
+    if (properties === undefined || Object.keys(properties).length === 0) {
+      return Effect.succeed({});
+    }
+
+    return Effect.try({
+      try: () => {
+        const hdrs = headers();
+        for (const [key, val] of Object.entries(properties)) {
+          hdrs.append(key, val);
+        }
+        return { headers: hdrs };
+      },
+      catch: (error) => pubSubError(`headers:${subject}`, error),
+    });
+  };
+
   return {
     send: (message, properties) =>
       Effect.runPromise(
@@ -91,19 +112,7 @@ function makeNatsProducer<T>(
             Effect.mapError((error) => pubSubError(`encode-json:${subject}`, error)),
           );
           const data = sc.encode(json);
-          const opts: Record<string, unknown> = {};
-
-          if (properties !== undefined && Object.keys(properties).length > 0) {
-            const { headers } = yield* Effect.tryPromise({
-              try: () => import("nats"),
-              catch: (error) => pubSubError("import:nats-headers", error),
-            });
-            const hdrs = headers();
-            for (const [key, val] of Object.entries(properties)) {
-              hdrs.append(key, val);
-            }
-            opts.headers = hdrs;
-          }
+          const opts = yield* makePublishOptions(properties);
 
           yield* Effect.tryPromise({
             try: () => js.publish(subject, data, opts),
@@ -204,8 +213,11 @@ function makeNatsConsumer<T>(
           if (!isNatsMessage(message)) {
             return yield* pubSubError(`acknowledge:${subject}`, "Message was not produced by NATS backend");
           }
-          yield* Effect.sync(() => {
-            message._jsMsg.ack();
+          yield* Effect.try({
+            try: () => {
+              message._jsMsg.ack();
+            },
+            catch: (error) => pubSubError(`acknowledge:${subject}`, error),
           });
         }),
       ),
@@ -218,8 +230,11 @@ function makeNatsConsumer<T>(
               "Message was not produced by NATS backend",
             );
           }
-          yield* Effect.sync(() => {
-            message._jsMsg.nak();
+          yield* Effect.try({
+            try: () => {
+              message._jsMsg.nak();
+            },
+            catch: (error) => pubSubError(`negative-acknowledge:${subject}`, error),
           });
         }),
       ),