Preserve supplied environment casing

exceptionless · ejsmith · Sep 10, 2026 · Sep 10, 2026 · Sep 10, 2026 · Sep 10, 2026
commit 0e675b4caa5dcd9909156cd22c0219e864680df3
diff --git a/.agents/skills/exceptionless-javascript/SKILL.md b/.agents/skills/exceptionless-javascript/SKILL.md
@@ -9,7 +9,7 @@ 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`. See [configuration.md](references/configuration.md).
+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).
 
 ## Official Docs
 

diff --git a/.agents/skills/exceptionless-javascript/references/configuration.md b/.agents/skills/exceptionless-javascript/references/configuration.md
@@ -31,7 +31,7 @@ await Exceptionless.startup((config) => {
 
 ## Deployment environment
 
-Set `config.environment = "production"` or call `config.setEnvironment("production")`. Per-event `setEnvironment("staging")` overrides the default. Names are trimmed and lowercased; empty names, names longer than 64 characters, and control characters are ignored. Missing values remain unspecified. 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.
+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 control characters are ignored. 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
 

diff --git a/README.md b/README.md
@@ -8,7 +8,7 @@ The definition of the word exceptionless is: to be without exception. Exceptionl
 
 ## Browser
 
-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, lowercased, and limited to 64 characters. Missing or invalid names remain unspecified. The top-level `environment` is separate from machine/runtime diagnostics in `data.@environment`; stacks and fixed versions remain shared across 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. The top-level `environment` is separate from machine/runtime diagnostics in `data.@environment`; stacks and fixed versions remain shared across environments.
 
 You can install the npm package via `npm install @exceptionless/browser --save`
 or via cdn [`https://unpkg.com/@exceptionless/browser`](https://unpkg.com/@exceptionless/browser).

diff --git a/packages/core/src/Utils.ts b/packages/core/src/Utils.ts
@@ -563,7 +563,7 @@ export function normalizeEnvironment(value: string | null | undefined): string |
   if (typeof value !== "string") {
     return undefined;
   }
-  const name = value.trim().toLowerCase();
+  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;
 }
diff --git a/packages/core/test/configuration/Configuration.test.ts b/packages/core/test/configuration/Configuration.test.ts
@@ -3,13 +3,15 @@ import { describe, expect, test } from "vitest";
 import { Configuration } from "../../src/configuration/Configuration.js";
 
 describe("Configuration", () => {
-  test("should normalize deployment environments and allow clearing the default", () => {
+  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");
+    expect(config.environment).toBe("Production");
     config.environment = "Staging";
-    expect(config.environment).toBe("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));

diff --git a/packages/core/test/plugins/default/ConfigurationDefaultsPlugin.test.ts b/packages/core/test/plugins/default/ConfigurationDefaultsPlugin.test.ts
@@ -14,17 +14,17 @@ describe("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.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");
+    expect(builder.target.environment).toBe("Staging");
+    expect(JSON.parse(JSON.stringify(builder.target)).environment).toBe("Staging");
   });
 
-  test.each(["", " ", "x".repeat(65), "prod\ninvalid", "İ".repeat(64)])("should keep invalid override %j unspecified", async (environment) => {
+  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);

diff --git a/packages/core/test/plugins/default/DuplicateCheckerPlugin.test.ts b/packages/core/test/plugins/default/DuplicateCheckerPlugin.test.ts
@@ -86,14 +86,16 @@ describe("DuplicateCheckerPlugin", () => {
 
   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", "staging", undefined]);
+    expect(enqueue.mock.calls.map(([event]) => event.environment).sort()).toEqual(["Production", "production", "staging", undefined]);
   });
 
   test("should ignore error without stack", async () => {