diff --git a/src/event-capture.ts b/src/event-capture.ts
index 0828a0e3..2c384b5a 100644
--- a/src/event-capture.ts
+++ b/src/event-capture.ts
@@ -107,7 +107,11 @@ export class EventCaptureClient {
 
     constructor(options: EventCaptureClientOptions) {
         this.apiKey = options.apiKey;
-        this.baseUrl = options.baseUrl ?? DEFAULT_EVENT_CAPTURE_BASE_URL;
+        // Treat a blank baseUrl like an unset one: `?? default` only rescues
+        // null/undefined, so an empty string would slip through and make the
+        // endpoint `"" + "/batch"` = "/batch", silently dropping every batch.
+        this.baseUrl =
+            options.baseUrl && options.baseUrl.trim() !== "" ? options.baseUrl : DEFAULT_EVENT_CAPTURE_BASE_URL;
         this.timeoutMs = options.timeoutMs ?? DEFAULT_TIMEOUT_MS;
         this.fetcher = options.fetcher;
         this.headers = options.headers ?? {};
diff --git a/src/wrapper.ts b/src/wrapper.ts
index 6ba90dda..e06b0429 100644
--- a/src/wrapper.ts
+++ b/src/wrapper.ts
@@ -187,15 +187,28 @@ export class SchematicClient extends BaseClient {
     constructor(opts?: SchematicOptions) {
         const {
             apiKey = "",
-            basePath,
+            basePath: basePathOpt,
             eventBufferInterval,
-            eventCaptureBaseURL,
+            eventCaptureBaseURL: eventCaptureBaseURLOpt,
             flagDefaults = {},
             logLevel,
             timeoutMs,
         } = opts ?? {};
         let { offline = false } = opts ?? {};
 
+        // Treat a blank URL option the same as an unset one. Consumers routinely
+        // forward an env var straight through (`basePath: process.env.X`), which
+        // is `""` when that var is present-but-empty — an extremely common shape
+        // (a blank `SCHEMATIC_*_URL=` line copied from a .env template). An empty
+        // string would otherwise survive the downstream `?? default` (which only
+        // rescues null/undefined) and produce a broken base URL — e.g. event
+        // capture's `"" + "/batch"` = "/batch" — silently dropping every event
+        // batch, including the lease-tagged Track events that settle credit
+        // usage. Normalizing to undefined lets the built-in prod defaults apply.
+        const basePath = basePathOpt && basePathOpt.trim() !== "" ? basePathOpt : undefined;
+        const eventCaptureBaseURL =
+            eventCaptureBaseURLOpt && eventCaptureBaseURLOpt.trim() !== "" ? eventCaptureBaseURLOpt : undefined;
+
         // A consumer-provided logger owns its own level configuration, so we use
         // it as-is and ignore logLevel. Otherwise build the default
         // ConsoleLogger at the requested level (defaulting to "warn").
diff --git a/tests/unit/event-capture.test.ts b/tests/unit/event-capture.test.ts
index ec473276..894ba876 100644
--- a/tests/unit/event-capture.test.ts
+++ b/tests/unit/event-capture.test.ts
@@ -1,10 +1,7 @@
 /* eslint @typescript-eslint/no-explicit-any: 0 */
 
 import { CreateEventRequestBody } from "../../src/api";
-import {
-    DEFAULT_EVENT_CAPTURE_BASE_URL,
-    EventCaptureClient,
-} from "../../src/event-capture";
+import { DEFAULT_EVENT_CAPTURE_BASE_URL, EventCaptureClient } from "../../src/event-capture";
 import type { FetchFunction } from "../../src/core/fetcher/Fetcher";
 
 describe("EventCaptureClient", () => {
@@ -25,7 +22,9 @@ describe("EventCaptureClient", () => {
     const okResponse = { ok: true, body: {}, headers: {}, rawResponse: {} as any };
 
     const makeFetcher = (impl?: (...args: any[]) => any): jest.MockedFunction<FetchFunction> => {
-        const fn = jest.fn(impl ?? (() => Promise.resolve(okResponse))) as unknown as jest.MockedFunction<FetchFunction>;
+        const fn = jest.fn(
+            impl ?? (() => Promise.resolve(okResponse)),
+        ) as unknown as jest.MockedFunction<FetchFunction>;
         return fn;
     };
 
@@ -164,6 +163,23 @@ describe("EventCaptureClient", () => {
         expect(args.url).toBe("https://custom.example.com/batch");
     });
 
+    // A consumer that forwards `baseUrl: process.env.X` passes "" when the env
+    // var is present-but-empty. It must fall back to the default, not build a
+    // broken "/batch" endpoint that silently drops every batch.
+    it.each([
+        undefined,
+        "",
+        "   ",
+    ])("should fall back to the default base URL when baseUrl is blank (%p)", async (baseUrl) => {
+        const fetcher = makeFetcher();
+        const client = new EventCaptureClient({ apiKey, fetcher, baseUrl });
+
+        await client.sendBatch([buildEvent()]);
+
+        const args = fetcher.mock.calls[0][0];
+        expect(args.url).toBe(`${DEFAULT_EVENT_CAPTURE_BASE_URL}/batch`);
+    });
+
     it("should be a no-op when sending an empty batch", async () => {
         const fetcher = makeFetcher();
         const client = new EventCaptureClient({ apiKey, fetcher });
@@ -183,9 +199,7 @@ describe("EventCaptureClient", () => {
         );
         const client = new EventCaptureClient({ apiKey, fetcher });
 
-        await expect(client.sendBatch([buildEvent()])).rejects.toThrow(
-            "capture service returned HTTP 500: boom",
-        );
+        await expect(client.sendBatch([buildEvent()])).rejects.toThrow("capture service returned HTTP 500: boom");
     });
 
     it("should surface fetcher timeouts", async () => {
@@ -198,9 +212,7 @@ describe("EventCaptureClient", () => {
         );
         const client = new EventCaptureClient({ apiKey, fetcher });
 
-        await expect(client.sendBatch([buildEvent()])).rejects.toThrow(
-            "capture service returned request timed out",
-        );
+        await expect(client.sendBatch([buildEvent()])).rejects.toThrow("capture service returned request timed out");
     });
 
     it("should surface unknown fetcher errors", async () => {
@@ -213,9 +225,7 @@ describe("EventCaptureClient", () => {
         );
         const client = new EventCaptureClient({ apiKey, fetcher });
 
-        await expect(client.sendBatch([buildEvent()])).rejects.toThrow(
-            "capture service returned network down",
-        );
+        await expect(client.sendBatch([buildEvent()])).rejects.toThrow("capture service returned network down");
     });
 
     it("should serialize idempotency_key, trusted_client_clock, and backfill when set", async () => {