diff --git a/.agents/skills/exceptionless-javascript/SKILL.md b/.agents/skills/exceptionless-javascript/SKILL.md
index 99e273e0..639fe024 100644
--- a/.agents/skills/exceptionless-javascript/SKILL.md
+++ b/.agents/skills/exceptionless-javascript/SKILL.md
@@ -9,6 +9,8 @@ Use this skill to produce source-accurate setup code, integration guidance, and
 
 Keep answers compact. Prefer pointing to official docs for broad product behavior, and use local package READMEs/source to correct stale snippets or repo-specific package details.
 
+Deployment environments use `config.environment` or `config.setEnvironment(name)` as the default, and `builder.setEnvironment(name)` for overrides. They serialize as top-level `environment`, separately from `data.@environment`, preserving the supplied casing after trimming. See [configuration.md](references/configuration.md).
+
 ## Pick References
 
 Read only the references needed for the request. Start with the runtime for setup or the topic for an API question; add others only when relevant. Each reference contains focused examples and official documentation links. Use the [JavaScript overview](https://exceptionless.com/docs/clients/javascript/) for broader product context.
diff --git a/.agents/skills/exceptionless-javascript/references/client-core.md b/.agents/skills/exceptionless-javascript/references/client-core.md
index ba51925b..2b96d49c 100644
--- a/.agents/skills/exceptionless-javascript/references/client-core.md
+++ b/.agents/skills/exceptionless-javascript/references/client-core.md
@@ -22,7 +22,7 @@ await client.startup((config) => {
   config.version = "1.2.3";
   config.setUserIdentity("12345678", "Blake");
   config.defaultTags.push("Example", "JavaScript", "Core");
-  config.defaultData["deployment"] = { environment: "production" };
+  config.environment = "production";
 });
 ```
 
diff --git a/.agents/skills/exceptionless-javascript/references/configuration.md b/.agents/skills/exceptionless-javascript/references/configuration.md
index 721cc2f9..a58e3abe 100644
--- a/.agents/skills/exceptionless-javascript/references/configuration.md
+++ b/.agents/skills/exceptionless-javascript/references/configuration.md
@@ -23,12 +23,16 @@ import { Exceptionless } from "@exceptionless/browser";
 await Exceptionless.startup((config) => {
   config.apiKey = "API_KEY_HERE";
   config.version = "1.2.3";
+  config.environment = "production";
   config.setUserIdentity("12345678", "Blake");
   config.defaultTags.push("Example", "JavaScript");
-  config.defaultData["deployment"] = { environment: "production" };
 });
 ```
 
+## Deployment environment
+
+Set `config.environment = "production"` or call `config.setEnvironment("production")`. Per-event `setEnvironment("staging")` overrides the default. Names are trimmed and retain their supplied casing; empty names, names longer than 64 characters, and names with control characters are unspecified. An invalid per-event name stays unspecified instead of using the default; pass `null` or `undefined` to `setEnvironment` to use the default. Missing values remain unspecified. The server filters case-insensitively and normalizes aggregation keys. This property is independent of `data.@environment` runtime metadata and of the application version. It does not change server stack grouping or create per-environment status.
+
 ## Privacy
 
 For deeper guidance on PII removal, read [data-exclusions.md](data-exclusions.md).
diff --git a/.agents/skills/exceptionless-javascript/references/plugins.md b/.agents/skills/exceptionless-javascript/references/plugins.md
index 1d49378a..74112bc9 100644
--- a/.agents/skills/exceptionless-javascript/references/plugins.md
+++ b/.agents/skills/exceptionless-javascript/references/plugins.md
@@ -30,24 +30,24 @@ await Exceptionless.startup((config) => {
 import type { EventPluginContext, IEventPlugin, PluginContext } from "@exceptionless/core";
 import { Exceptionless } from "@exceptionless/browser";
 
-class DeploymentPlugin implements IEventPlugin {
+class BuildInfoPlugin implements IEventPlugin {
   priority = 90;
-  name = "DeploymentPlugin";
+  name = "BuildInfoPlugin";
 
   startup(context: PluginContext): Promise<void> {
-    context.log.info("Deployment plugin started");
+    context.log.info("Build information plugin started");
     return Promise.resolve();
   }
 
   run(context: EventPluginContext): Promise<void> {
     context.event.data ??= {};
-    context.event.data["deployment"] = "production";
+    context.event.data["build"] = "build-123";
     return Promise.resolve();
   }
 }
 await Exceptionless.startup((config) => {
   config.apiKey = "API_KEY_HERE";
-  config.addPlugin(new DeploymentPlugin());
+  config.addPlugin(new BuildInfoPlugin());
 });
 ```
 
diff --git a/.agents/skills/exceptionless-javascript/references/sending-events.md b/.agents/skills/exceptionless-javascript/references/sending-events.md
index a620ae36..c49f66c3 100644
--- a/.agents/skills/exceptionless-javascript/references/sending-events.md
+++ b/.agents/skills/exceptionless-javascript/references/sending-events.md
@@ -9,6 +9,14 @@ Use the platform package's `Exceptionless` singleton unless the user is building
 
 ## Common Events
 
+Deployment environments can be overridden per event:
+
+```js
+await Exceptionless.createLog("Deployment complete").setEnvironment("staging").submit();
+```
+
+Without an override, the event uses `config.environment`. Repeated errors from different environments are queued separately; the server still groups the same error into one stack.
+
 ```js
 import { Exceptionless } from "@exceptionless/browser";
 
diff --git a/README.md b/README.md
index 0dbf5938..2fb06058 100644
--- a/README.md
+++ b/README.md
@@ -156,6 +156,10 @@ await Exceptionless.startup((c) => {
 Please see the [docs](https://exceptionless.com/docs/clients/javascript/) for
 more information on configuring the client.
 
+#### Deployment environments
+
+Set a deployment environment in startup configuration with `config.environment = "production"` (or `config.setEnvironment("production")`). Override it on an event with `Exceptionless.createLog("Example").setEnvironment("staging").submit()`. Names are trimmed and limited to 64 characters, preserving the supplied casing. The server filters case-insensitively and normalizes aggregation keys. Missing or invalid names remain unspecified, and an invalid per-event name does not fall back to the configured default; pass `null` or `undefined` to `setEnvironment` to use the default. The top-level `environment` is separate from machine/runtime diagnostics in `data.@environment`; stacks and fixed versions remain shared across environments.
+
 ### Submitting Events and Errors
 
 Once configured, Exceptionless will automatically submit any unhandled exceptions
diff --git a/packages/core/src/EventBuilder.ts b/packages/core/src/EventBuilder.ts
index 7645e812..d2456fa0 100644
--- a/packages/core/src/EventBuilder.ts
+++ b/packages/core/src/EventBuilder.ts
@@ -62,6 +62,15 @@ export class EventBuilder {
     return this;
   }
 
+  public setEnvironment(value: string | null | undefined): EventBuilder {
+    if (value != null) {
+      this.target.environment = value;
+    } else {
+      delete this.target.environment;
+    }
+    return this;
+  }
+
   public setMessage(message: string | null | undefined): EventBuilder {
     if (message) {
       this.target.message = message;
diff --git a/packages/core/src/ExceptionlessClient.ts b/packages/core/src/ExceptionlessClient.ts
index e4590dca..18ab1cd5 100644
--- a/packages/core/src/ExceptionlessClient.ts
+++ b/packages/core/src/ExceptionlessClient.ts
@@ -7,7 +7,7 @@ import { EventContext } from "./models/EventContext.js";
 import { EventPluginContext } from "./plugins/EventPluginContext.js";
 import { EventPluginManager } from "./plugins/EventPluginManager.js";
 import { PluginContext } from "./plugins/PluginContext.js";
-import { allowProcessToExitWithoutWaitingForTimerOrInterval } from "./Utils.js";
+import { allowProcessToExitWithoutWaitingForTimerOrInterval, setNormalizedEnvironment } from "./Utils.js";
 
 export class ExceptionlessClient {
   private _intervalId: ReturnType<typeof setInterval> | undefined;
@@ -248,6 +248,9 @@ export class ExceptionlessClient {
       ev.date = new Date();
     }
 
+    // Plugins that run after the defaults can assign any value.
+    setNormalizedEnvironment(ev, ev.environment);
+
     await this.config.services.queue.enqueue(ev);
 
     if (ev.reference_id && ev.reference_id.length > 0) {
diff --git a/packages/core/src/Utils.ts b/packages/core/src/Utils.ts
index 1d64be44..5df2f5ba 100644
--- a/packages/core/src/Utils.ts
+++ b/packages/core/src/Utils.ts
@@ -1,3 +1,5 @@
+import type { Event } from "./models/Event.js";
+
 export function getHashCode(source: string): number {
   if (!source || source.length === 0) {
     return 0;
@@ -559,3 +561,23 @@ export function allowProcessToExitWithoutWaitingForTimerOrInterval(timeoutOrInte
     (timeoutOrIntervalId as { unref: () => ReturnType<typeof setTimeout> }).unref();
   }
 }
+export function normalizeEnvironment(value: string | null | undefined): string | undefined {
+  if (typeof value !== "string") {
+    return undefined;
+  }
+  const name = value.trim();
+  // eslint-disable-next-line no-control-regex -- Deployment names cannot contain control characters.
+  return name && name.length <= 64 && !/[\u0000-\u001f\u007f-\u009f]/u.test(name) ? name : undefined;
+}
+
+/**
+ * Sets the event's environment to the normalized value, or removes it when the value is not a valid name.
+ */
+export function setNormalizedEnvironment(event: Event, value: string | null | undefined): void {
+  const environment = normalizeEnvironment(value);
+  if (environment) {
+    event.environment = environment;
+  } else {
+    delete event.environment;
+  }
+}
diff --git a/packages/core/src/configuration/Configuration.ts b/packages/core/src/configuration/Configuration.ts
index 8bb93381..bab53683 100644
--- a/packages/core/src/configuration/Configuration.ts
+++ b/packages/core/src/configuration/Configuration.ts
@@ -13,7 +13,7 @@ import { DefaultEventQueue } from "../queue/DefaultEventQueue.js";
 import { IEventQueue } from "../queue/IEventQueue.js";
 import { ISubmissionClient } from "../submission/ISubmissionClient.js";
 import { DefaultSubmissionClient } from "../submission/DefaultSubmissionClient.js";
-import { guid } from "../Utils.js";
+import { guid, normalizeEnvironment } from "../Utils.js";
 import { KnownEventDataKeys } from "../models/Event.js";
 import { InMemoryStorage } from "../storage/InMemoryStorage.js";
 import { IStorage } from "../storage/IStorage.js";
@@ -21,6 +21,21 @@ import { LocalStorage } from "../storage/LocalStorage.js";
 import { ServerSettings } from "../configuration/SettingsManager.js";
 
 export class Configuration {
+  private _environment: string | undefined;
+
+  /** The default deployment environment for every event. */
+  public get environment(): string | undefined {
+    return this._environment;
+  }
+
+  public set environment(value: string | null | undefined) {
+    this._environment = normalizeEnvironment(value);
+  }
+
+  public setEnvironment(value: string | null | undefined): void {
+    this.environment = value;
+  }
+
   constructor() {
     this.services = {
       lastReferenceIdManager: new DefaultLastReferenceIdManager(),
diff --git a/packages/core/src/models/Event.ts b/packages/core/src/models/Event.ts
index 1c8dd053..f499fe25 100644
--- a/packages/core/src/models/Event.ts
+++ b/packages/core/src/models/Event.ts
@@ -8,6 +8,8 @@ import { ManualStackingInfo } from "../models/data/ManualStackingInfo.js";
 export type EventType = "error" | "usage" | "log" | "404" | "session" | string;
 
 export interface Event {
+  /** The deployment environment, such as production or staging. */
+  environment?: string;
   /** The event type (ie. error, log message, feature usage). */
   type?: EventType;
   /** The event source (ie. machine name, log name, feature name). */
diff --git a/packages/core/src/plugins/default/ConfigurationDefaultsPlugin.ts b/packages/core/src/plugins/default/ConfigurationDefaultsPlugin.ts
index 414ca136..6a010a4c 100644
--- a/packages/core/src/plugins/default/ConfigurationDefaultsPlugin.ts
+++ b/packages/core/src/plugins/default/ConfigurationDefaultsPlugin.ts
@@ -1,4 +1,4 @@
-import { isEmpty, stringify } from "../../Utils.js";
+import { isEmpty, setNormalizedEnvironment, stringify } from "../../Utils.js";
 import { EventPluginContext } from "../../plugins/EventPluginContext.js";
 import { IEventPlugin } from "../../plugins/IEventPlugin.js";
 
@@ -9,6 +9,7 @@ export class ConfigurationDefaultsPlugin implements IEventPlugin {
   public run(context: EventPluginContext): Promise<void> {
     const { dataExclusions, defaultData, defaultTags } = context.client.config;
     const ev = context.event;
+    setNormalizedEnvironment(ev, ev.environment ?? context.client.config.environment);
 
     if (defaultTags) {
       ev.tags = [...(ev.tags || []), ...defaultTags];
diff --git a/packages/core/src/plugins/default/DuplicateCheckerPlugin.ts b/packages/core/src/plugins/default/DuplicateCheckerPlugin.ts
index bd04a429..1203c7f4 100644
--- a/packages/core/src/plugins/default/DuplicateCheckerPlugin.ts
+++ b/packages/core/src/plugins/default/DuplicateCheckerPlugin.ts
@@ -1,6 +1,6 @@
 import { InnerErrorInfo } from "../../models/data/ErrorInfo.js";
 import { KnownEventDataKeys } from "../../models/Event.js";
-import { allowProcessToExitWithoutWaitingForTimerOrInterval, getHashCode } from "../../Utils.js";
+import { allowProcessToExitWithoutWaitingForTimerOrInterval, getHashCode, setNormalizedEnvironment } from "../../Utils.js";
 import { EventPluginContext } from "../../plugins/EventPluginContext.js";
 import { IEventPlugin } from "../../plugins/IEventPlugin.js";
 
@@ -51,11 +51,12 @@ export class DuplicateCheckerPlugin implements IEventPlugin {
 
     const error = context.event.data?.[KnownEventDataKeys.Error];
     const hashCode = calculateHashCode(error);
+    const environment = context.event.environment;
     if (hashCode) {
       const count = context.event.count || 1;
       const now = this._getCurrentTime();
 
-      const merged = this._mergedEvents.filter((s) => s.hashCode === hashCode)[0];
+      const merged = this._mergedEvents.find((s) => s.hashCode === hashCode && s.environment === environment);
       if (merged) {
         merged.incrementCount(count);
         merged.updateDate(context.event.date);
@@ -63,7 +64,10 @@ export class DuplicateCheckerPlugin implements IEventPlugin {
         context.cancelled = true;
       }
 
-      if (!context.cancelled && this._processedHashCodes.some((h) => h.hash === hashCode && h.timestamp >= now - this._interval)) {
+      if (
+        !context.cancelled &&
+        this._processedHashCodes.some((h) => h.hash === hashCode && h.environment === environment && h.timestamp >= now - this._interval)
+      ) {
         context.log.trace("Adding event with hash: " + hashCode);
         this._mergedEvents.push(new MergedEvent(hashCode, context, count));
         context.cancelled = true;
@@ -73,6 +77,7 @@ export class DuplicateCheckerPlugin implements IEventPlugin {
         context.log.trace(`Enqueueing event with hash: ${hashCode} to cache`);
         this._processedHashCodes.push({
           hash: hashCode,
+          environment,
           timestamp: now
         });
 
@@ -95,16 +100,19 @@ export class DuplicateCheckerPlugin implements IEventPlugin {
 
 interface TimestampedHash {
   hash: number;
+  environment: string | undefined;
   timestamp: number;
 }
 
 class MergedEvent {
   public hashCode: number;
+  public readonly environment: string | undefined;
   private _count: number;
   private _context: EventPluginContext;
 
   constructor(hashCode: number, context: EventPluginContext, count: number) {
     this.hashCode = hashCode;
+    this.environment = context.event.environment;
     this._context = context;
     this._count = count;
   }
@@ -115,6 +123,8 @@ class MergedEvent {
 
   public async resubmit(): Promise<void> {
     this._context.event.count = this._count;
+    // Plugins between the defaults and this one can assign any value.
+    setNormalizedEnvironment(this._context.event, this._context.event.environment);
     await this._context.client.config.services.queue.enqueue(this._context.event);
   }
 
diff --git a/packages/core/test/ExceptionlessClient.test.ts b/packages/core/test/ExceptionlessClient.test.ts
index a12185ea..c48fd4a5 100644
--- a/packages/core/test/ExceptionlessClient.test.ts
+++ b/packages/core/test/ExceptionlessClient.test.ts
@@ -37,6 +37,25 @@ describe("ExceptionlessClient", () => {
     expect(context.event.reference_id).toBe(lastReferenceIdManager.getLast());
   });
 
+  test.each([
+    [" QA\t", "QA"],
+    ["x".repeat(65), undefined]
+  ])("should normalize environment %j assigned by a later plugin", async (environment, expected) => {
+    const client = new ExceptionlessClient();
+    client.config.apiKey = "UNIT_TEST_API_KEY";
+    client.config.environment = "production";
+    client.config.addPlugin("late-environment", 90, (context) => {
+      context.event.environment = environment;
+      return Promise.resolve();
+    });
+    const enqueue = vi.spyOn(client.config.services.queue, "enqueue").mockResolvedValue();
+
+    await client.submitLog("test");
+
+    expect(enqueue).toHaveBeenCalledOnce();
+    expect(enqueue.mock.calls[0]?.[0].environment).toBe(expected);
+  });
+
   test("should accept undefined source", () => {
     const client = new ExceptionlessClient();
     client.config.apiKey = "UNIT_TEST_API_KEY";
diff --git a/packages/core/test/configuration/Configuration.test.ts b/packages/core/test/configuration/Configuration.test.ts
index fc2aec8e..4d0a6881 100644
--- a/packages/core/test/configuration/Configuration.test.ts
+++ b/packages/core/test/configuration/Configuration.test.ts
@@ -3,6 +3,25 @@ import { describe, expect, test } from "vitest";
 import { Configuration } from "../../src/configuration/Configuration.js";
 
 describe("Configuration", () => {
+  test("should trim deployment environments, preserve casing, and allow clearing the default", () => {
+    const config = new Configuration();
+    expect(config.environment).toBeUndefined();
+    config.setEnvironment(" Production ");
+    expect(config.environment).toBe("Production");
+    config.environment = "Staging";
+    expect(config.environment).toBe("Staging");
+    config.environment = "İ".repeat(64);
+    expect(config.environment).toBe("İ".repeat(64));
+    config.setEnvironment("");
+    expect(config.environment).toBeUndefined();
+    config.setEnvironment("x".repeat(65));
+    expect(config.environment).toBeUndefined();
+    config.setEnvironment("prod\ninvalid");
+    expect(config.environment).toBeUndefined();
+    config.setEnvironment("\tProduction\n");
+    expect(config.environment).toBe("Production");
+  });
+
   test("should override configuration defaults", () => {
     let config = new Configuration();
     expect(config.apiKey).toEqual("");
diff --git a/packages/core/test/plugins/default/ConfigurationDefaultsPlugin.test.ts b/packages/core/test/plugins/default/ConfigurationDefaultsPlugin.test.ts
index 90e948fa..a30ece8f 100644
--- a/packages/core/test/plugins/default/ConfigurationDefaultsPlugin.test.ts
+++ b/packages/core/test/plugins/default/ConfigurationDefaultsPlugin.test.ts
@@ -7,6 +7,62 @@ import { EventPluginContext } from "../../../src/plugins/EventPluginContext.js";
 import { EventContext } from "../../../src/models/EventContext.js";
 
 describe("ConfigurationDefaultsPlugin", () => {
+  test("should apply deployment defaults to all event types and preserve overrides and runtime metadata", async () => {
+    const client = new ExceptionlessClient();
+    client.config.setEnvironment(" Production ");
+    const plugin = new ConfigurationDefaultsPlugin();
+    for (const type of ["error", "log", "usage", "session"]) {
+      const event: Event = {
+        type,
+        data: {
+          "@environment": {
+            machine_name: "worker-1"
+          }
+        }
+      };
+      await plugin.run(new EventPluginContext(client, event, new EventContext()));
+      expect(event.environment).toBe("Production");
+      expect(event.data?.["@environment"]?.machine_name).toBe("worker-1");
+    }
+
+    const builder = client.createLog("test", "message").setEnvironment(" Staging ");
+    await plugin.run(new EventPluginContext(client, builder.target, new EventContext()));
+    expect(builder.target.environment).toBe("Staging");
+    expect(JSON.parse(JSON.stringify(builder.target)).environment).toBe("Staging");
+  });
+
+  test.each(["", " ", "x".repeat(65), "prod\ninvalid"])("should keep invalid override %j unspecified", async (environment) => {
+    const client = new ExceptionlessClient();
+    client.config.environment = "production";
+    const builder = client.createLog("test", "message").setEnvironment(environment);
+    await new ConfigurationDefaultsPlugin().run(new EventPluginContext(client, builder.target, new EventContext()));
+    expect(builder.target.environment).toBeUndefined();
+  });
+
+  test.each([null, undefined])("should apply the default when the override is cleared with %j", async (environment) => {
+    const client = new ExceptionlessClient();
+    client.config.environment = "production";
+    const builder = client.createLog("test", "message").setEnvironment("staging").setEnvironment(environment);
+    await new ConfigurationDefaultsPlugin().run(new EventPluginContext(client, builder.target, new EventContext()));
+    expect(builder.target.environment).toBe("production");
+  });
+
+  test("should trim surrounding control whitespace from an override", async () => {
+    const client = new ExceptionlessClient();
+    client.config.environment = "production";
+    const builder = client.createLog("test", "message").setEnvironment("\tStaging\n");
+    await new ConfigurationDefaultsPlugin().run(new EventPluginContext(client, builder.target, new EventContext()));
+    expect(builder.target.environment).toBe("Staging");
+  });
+
+  test("should omit an unspecified environment from the serialized event", async () => {
+    const client = new ExceptionlessClient();
+    const builder = client.createLog("test", "message");
+    await new ConfigurationDefaultsPlugin().run(new EventPluginContext(client, builder.target, new EventContext()));
+    const serialized = JSON.parse(JSON.stringify(builder.target)) as Record<string, unknown>;
+    expect(Object.keys(serialized)).not.toContain("environment");
+  });
+
   describe("should add default", () => {
     const userDataKey: string = "user";
     const user = {
diff --git a/packages/core/test/plugins/default/DuplicateCheckerPlugin.test.ts b/packages/core/test/plugins/default/DuplicateCheckerPlugin.test.ts
index ad758afc..864f1b89 100644
--- a/packages/core/test/plugins/default/DuplicateCheckerPlugin.test.ts
+++ b/packages/core/test/plugins/default/DuplicateCheckerPlugin.test.ts
@@ -1,4 +1,4 @@
-import { beforeEach, describe, expect, test } from "vitest";
+import { beforeEach, describe, expect, test, vi } from "vitest";
 
 import { DuplicateCheckerPlugin } from "../../../src/plugins/default/DuplicateCheckerPlugin.js";
 import { ExceptionlessClient } from "../../../src/ExceptionlessClient.js";
@@ -51,7 +51,7 @@ describe("DuplicateCheckerPlugin", () => {
     plugin = new DuplicateCheckerPlugin(() => now, 50);
   });
 
-  const run = async (stackTrace?: StackFrameInfo[]): Promise<EventPluginContext> => {
+  const run = async (stackTrace?: StackFrameInfo[], environment?: string): Promise<EventPluginContext> => {
     // TODO: Generate unique stack traces based on test data.
     const context = new EventPluginContext(
       client,
@@ -68,6 +68,9 @@ describe("DuplicateCheckerPlugin", () => {
       new EventContext()
     );
 
+    if (environment) {
+      context.event.environment = environment;
+    }
     await plugin.run(context);
     return context;
   };
@@ -83,6 +86,28 @@ describe("DuplicateCheckerPlugin", () => {
     }, 100);
   });
 
+  test("should merge duplicates only within the same environment", async () => {
+    const enqueue = vi.spyOn(client.config.services.queue, "enqueue");
+    expect((await run(Exception1StackTrace, "Production")).cancelled).not.toBe(true);
+    expect((await run(Exception1StackTrace, "production")).cancelled).not.toBe(true);
+    expect((await run(Exception1StackTrace, "staging")).cancelled).not.toBe(true);
+    expect((await run(Exception1StackTrace)).cancelled).not.toBe(true);
+    expect((await run(Exception1StackTrace, "Production")).cancelled).toBe(true);
+    expect((await run(Exception1StackTrace, "production")).cancelled).toBe(true);
+    expect((await run(Exception1StackTrace, "staging")).cancelled).toBe(true);
+    expect((await run(Exception1StackTrace)).cancelled).toBe(true);
+    await plugin.suspend();
+    expect(enqueue.mock.calls.map(([event]) => event.environment).sort()).toEqual(["Production", "production", "staging", undefined]);
+  });
+
+  test("should normalize the environment of a resubmitted duplicate", async () => {
+    const enqueue = vi.spyOn(client.config.services.queue, "enqueue").mockResolvedValue();
+    await run(Exception1StackTrace, " staging\n");
+    expect((await run(Exception1StackTrace, " staging\n")).cancelled).toBe(true);
+    await plugin.suspend();
+    expect(enqueue.mock.calls.map(([event]) => event.environment)).toEqual(["staging"]);
+  });
+
   test("should ignore error without stack", async () => {
     await run();
     const contextOfSecondRun = await run();
diff --git a/packages/react-native/README.md b/packages/react-native/README.md
index 5751f0ed..c75818d1 100644
--- a/packages/react-native/README.md
+++ b/packages/react-native/README.md
@@ -78,8 +78,8 @@ await Exceptionless.startup((c) => {
   // Optional: add default tags
   c.defaultTags.push("react-native", "ios");
 
-  // Optional: add default data
-  c.defaultData["environment"] = "production";
+  // Optional: set the deployment environment
+  c.environment = "production";
 });
 ```