diff --git a/apps/desktop/src/app/DesktopObservability.ts b/apps/desktop/src/app/DesktopObservability.ts
index 78be929c088c..720f9b317cc9 100644
--- a/apps/desktop/src/app/DesktopObservability.ts
+++ b/apps/desktop/src/app/DesktopObservability.ts
@@ -39,8 +39,8 @@ const DESKTOP_LOG_FILE_MAX_BYTES = 10 * 1024 * 1024;
 const DESKTOP_LOG_FILE_MAX_FILES = 10;
 const DESKTOP_BACKEND_CHILD_LOG_FIBER_ID = "#backend-child";
 const DESKTOP_TRACE_BATCH_WINDOW_MS = 1_000;
-/** What the main process calls itself when nothing named the service. */
-const DESKTOP_SERVICE_NAME = "desktop";
+/** What the main process calls itself, in the family with `t3-server` and `t3-web`. */
+const DESKTOP_SERVICE_NAME = "t3-desktop";
 const DESKTOP_BACKEND_OUTPUT_BUFFER_MAX_BYTES = 1024 * 1024;
 const DESKTOP_BACKEND_OUTPUT_BUFFER_MAX_CHUNKS = 256;
 
@@ -372,7 +372,7 @@ const resolveOtlpExport = Effect.gen(function* () {
       logs: Option.getOrUndefined(environment.otlpLogsUrl) ?? persisted.otlpLogsUrl,
     },
     namedExportIntervalMs: Option.getOrUndefined(environment.otlpExportIntervalMs),
-    defaultServiceName: DESKTOP_SERVICE_NAME,
+    serviceName: DESKTOP_SERVICE_NAME,
     runtimeAttributes: {
       "service.runtime": "desktop",
       "service.mode": environment.isDevelopment ? "development" : "packaged",
diff --git a/apps/desktop/src/app/DesktopOtlpExport.test.ts b/apps/desktop/src/app/DesktopOtlpExport.test.ts
index 5ba253e220c6..ac70ef48ea11 100644
--- a/apps/desktop/src/app/DesktopOtlpExport.test.ts
+++ b/apps/desktop/src/app/DesktopOtlpExport.test.ts
@@ -30,7 +30,7 @@ const resolve = (
         otel,
         named: { ...noNamedEndpoints, ...overrides.named },
         namedExportIntervalMs: overrides.namedExportIntervalMs,
-        defaultServiceName: "desktop",
+        serviceName: "t3-desktop",
         runtimeAttributes: { "service.runtime": "desktop", "service.mode": "development" },
       }),
     ),
@@ -154,7 +154,6 @@ describe("resolveDesktopOtlpExport", () => {
   it.effect("cannot be made to claim it is the server process", () =>
     Effect.gen(function* () {
       const resolved = yield* resolve({
-        OTEL_SERVICE_NAME: "t3-desktop",
         OTEL_SERVICE_VERSION: "1.2.3",
         OTEL_RESOURCE_ATTRIBUTES: "deployment.environment=lab,service.runtime=t3-server",
       });
@@ -165,10 +164,34 @@ describe("resolveDesktopOtlpExport", () => {
     }),
   );
 
-  it.effect("keeps calling itself the desktop when nothing named the service", () =>
+  it.effect("cannot be renamed by the environment", () =>
+    Effect.gen(function* () {
+      const resolved = yield* resolve({
+        OTEL_SERVICE_NAME: "some-other-app",
+        OTEL_EXPORTER_OTLP_ENDPOINT: "https://collector.example.com",
+      });
+      assert.strictEqual(resolved.resource.serviceName, "t3-desktop");
+      assert.lengthOf(resolved.warnings, 1);
+      assert.include(resolved.warnings[0] ?? "", "OTEL_SERVICE_NAME was ignored");
+    }),
+  );
+
+  it.effect("cannot be renamed through the resource attributes either", () =>
+    Effect.gen(function* () {
+      const resolved = yield* resolve({
+        OTEL_RESOURCE_ATTRIBUTES: "service.name=some-other-app,host.name=lab-01",
+      });
+      assert.strictEqual(resolved.resource.serviceName, "t3-desktop");
+      assert.strictEqual(resolved.resource.attributes["service.name"], undefined);
+      assert.strictEqual(resolved.resource.attributes["host.name"], "lab-01");
+      assert.include(resolved.warnings[0] ?? "", "service.name was ignored");
+    }),
+  );
+
+  it.effect("names itself even when the environment says nothing", () =>
     Effect.gen(function* () {
       const resolved = yield* resolve({});
-      assert.strictEqual(resolved.resource.serviceName, "desktop");
+      assert.strictEqual(resolved.resource.serviceName, "t3-desktop");
       assert.strictEqual(resolved.resource.serviceVersion, undefined);
     }),
   );
diff --git a/apps/desktop/src/app/DesktopOtlpExport.ts b/apps/desktop/src/app/DesktopOtlpExport.ts
index a10b15d760f0..f041e65d655a 100644
--- a/apps/desktop/src/app/DesktopOtlpExport.ts
+++ b/apps/desktop/src/app/DesktopOtlpExport.ts
@@ -56,12 +56,12 @@ export interface DesktopOtlpExportInput {
   readonly named: DesktopNamedOtlpEndpoints;
   /** `T3CODE_OTLP_EXPORT_INTERVAL_MS`, which deliberately covers every signal. */
   readonly namedExportIntervalMs: number | undefined;
-  /** Used when nothing named a service, so existing dashboards keep working. */
-  readonly defaultServiceName: string;
+  /** What this process calls itself. The environment cannot rename it. */
+  readonly serviceName: string;
   /**
-   * What this process is, as opposed to what the machine calls the service.
-   * Applied last so an ambient `OTEL_RESOURCE_ATTRIBUTES` cannot make the main
-   * process claim to be the server.
+   * What this process is. Applied last so an ambient
+   * `OTEL_RESOURCE_ATTRIBUTES` cannot make the main process claim to be the
+   * server.
    */
   readonly runtimeAttributes: Readonly<Record<string, string>>;
 }
@@ -106,7 +106,7 @@ const resolveSignal = (
 export const resolveDesktopOtlpExport = (input: DesktopOtlpExportInput): DesktopOtlpExport => {
   const { otel, named } = input;
   const resource: DesktopOtlpResource = {
-    serviceName: otel.resource.serviceName ?? input.defaultServiceName,
+    serviceName: input.serviceName,
     serviceVersion: otel.resource.serviceVersion,
     attributes: { ...otel.resource.attributes, ...input.runtimeAttributes },
   };
diff --git a/apps/server/src/cli/config.test.ts b/apps/server/src/cli/config.test.ts
index a30dc3c517fe..5151e07cb2de 100644
--- a/apps/server/src/cli/config.test.ts
+++ b/apps/server/src/cli/config.test.ts
@@ -539,7 +539,21 @@ it.layer(NodeServices.layer)("cli config resolution", (it) => {
       expect(resolved.otlpTracesUrl).toBe("https://collector.example.com/v1/traces");
       expect(resolved.otlpMetricsUrl).toBe("https://collector.example.com/v1/metrics");
       expect(resolved.otlpLogsUrl).toBe("https://collector.example.com/v1/logs");
-      expect(resolved.otlpServiceName).toBe("t3");
+      // The endpoint is the machine's to name. The service is not.
+      expect(resolved.otlpServiceName).toBe("t3-server");
+    }),
+  );
+
+  it.effect("cannot be renamed by the environment", () =>
+    Effect.gen(function* () {
+      // A shell profile that names the app it was written for must not decide
+      // what T3 Code calls itself, or one dashboard quietly covers two apps.
+      const resolved = yield* resolveWithEnv({
+        OTEL_SERVICE_NAME: "some-other-app",
+        OTEL_RESOURCE_ATTRIBUTES: "service.name=some-other-app",
+      });
+
+      expect(resolved.otlpServiceName).toBe("t3-server");
     }),
   );
 
@@ -560,7 +574,7 @@ it.layer(NodeServices.layer)("cli config resolution", (it) => {
       expect(resolved.otlpTracesUrl).toBe("https://collector.example.com/v1/traces");
       expect(resolved.otlpMetricsUrl).toBe("https://collector.example.com/v1/metrics");
       expect(resolved.otlpLogsUrl).toBe("https://collector.example.com/v1/logs");
-      expect(resolved.otlpServiceName).toBe("t3");
+      expect(resolved.otlpServiceName).toBe("t3-server");
     }),
   );
 
diff --git a/apps/server/src/cli/config.ts b/apps/server/src/cli/config.ts
index 770ace8ed1be..9b5d96cdf65c 100644
--- a/apps/server/src/cli/config.ts
+++ b/apps/server/src/cli/config.ts
@@ -421,8 +421,7 @@ export const resolveServerConfig = (
         env.otlpExportIntervalMs ?? otelEnvironment.metrics.settings?.exportIntervalMs ?? 10_000,
       otlpLogsExportIntervalMs:
         env.otlpExportIntervalMs ?? otelEnvironment.logs.settings?.exportIntervalMs ?? 10_000,
-      otlpServiceName:
-        named(env.otlpServiceName) ?? otelEnvironment.resource.serviceName ?? "t3-server",
+      otlpServiceName: named(env.otlpServiceName) ?? "t3-server",
       otelEnvironment,
       mode,
       port,
diff --git a/docs/fork/0018-the-standard-otel-variables-are-honored.md b/docs/fork/0018-the-standard-otel-variables-are-honored.md
index 5ee42491364b..553aaa52d104 100644
--- a/docs/fork/0018-the-standard-otel-variables-are-honored.md
+++ b/docs/fork/0018-the-standard-otel-variables-are-honored.md
@@ -12,10 +12,10 @@
 - Send the credentials your collector requires. `OTEL_EXPORTER_OTLP_HEADERS`
   reaches the exporter, including the proxy that forwards browser traces, so an
   authenticated endpoint stops rejecting the whole stream.
-- Get one service identity across your fleet. `OTEL_SERVICE_NAME`,
-  `OTEL_SERVICE_VERSION`, and `OTEL_RESOURCE_ATTRIBUTES` are attached to every
-  span and metric, so T3 Code sits in the same dashboards as everything else
-  rather than under a name only it uses.
+- Tell your instances apart. `OTEL_SERVICE_VERSION` and
+  `OTEL_RESOURCE_ATTRIBUTES` are attached to every span and metric, so T3 Code
+  sits in the same dashboards as everything else. Service names themselves are
+  static, and `OTEL_SERVICE_NAME` is refused with a warning; see 0023.
 - Turn export off from the environment. `OTEL_SDK_DISABLED=true` stops every
   export, including one configured in Settings, which is the one switch a
   shared machine needs.
diff --git a/docs/fork/0022-the-desktop-app-reports-its-own-work.md b/docs/fork/0022-the-desktop-app-reports-its-own-work.md
index e71dee97f4b8..e6e9f10b772d 100644
--- a/docs/fork/0022-the-desktop-app-reports-its-own-work.md
+++ b/docs/fork/0022-the-desktop-app-reports-its-own-work.md
@@ -10,18 +10,19 @@
   and metrics under the service name `desktop`, alongside the server work they
   cause.
 - Configure it the way you configure everything else. The Electron main process
-  reads the same `OTEL_*` variables as the server, in the same order, so a
-  machine that points one of them at a collector points both. It had a trace
-  exporter before, and only its own `T3CODE_OTLP_TRACES_URL` could reach it,
-  which almost nobody sets.
+  reads the same `OTEL_*` endpoint variables as the server, in the same order,
+  so a machine that points one of them at a collector points both. It had a
+  trace exporter before, and only its own `T3CODE_OTLP_TRACES_URL` could reach
+  it, which almost nobody sets.
 - Get logs and metrics from it, not only traces. A crash loop before the server
   is even up used to leave nothing behind but a local file on the machine it
   happened on.
 - Turn it off the same way. `OTEL_SDK_DISABLED=true` stops both processes.
-- Tell the two apart without trusting the environment. `service.runtime` on the
-  main process is always `desktop`, so an ambient
+- Tell the two apart without trusting the environment. The main process reports
+  as `t3-desktop`, joining `t3-server` and `t3-web`, and `service.runtime` on it
+  is always `desktop`, so an ambient
   `OTEL_RESOURCE_ATTRIBUTES=service.runtime=t3-server` cannot make it file its
-  work under the server's name.
+  work under the server's name. See 0023 for why names are static.
 
 ## Why
 
diff --git a/docs/fork/0023-a-service-name-is-not-an-environment-variable.md b/docs/fork/0023-a-service-name-is-not-an-environment-variable.md
new file mode 100644
index 000000000000..c767e5d8c3e0
--- /dev/null
+++ b/docs/fork/0023-a-service-name-is-not-an-environment-variable.md
@@ -0,0 +1,58 @@
+# 0023: A service name is not an environment variable
+
+- PR: [TrogonStack/t3code#36](https://github.com/TrogonStack/t3code/pull/36)
+- Status: active
+
+## What you can do now
+
+- Trust what a service name means. T3 Code reports as `t3-server`, `t3-desktop`,
+  and `t3-web`, always, and nothing in the environment can change that. A
+  dashboard built on one of those names keeps meaning what it meant when you
+  built it.
+- Set `OTEL_SERVICE_NAME` on a machine without consequence. It is refused, and
+  the refusal is named in the startup log rather than applied quietly or
+  dropped quietly.
+- Keep telling your instances apart. `OTEL_RESOURCE_ATTRIBUTES` still works and
+  is the right lever for it, including `service.instance.id`,
+  `deployment.environment`, and `host.name`.
+- Rename the server on purpose if you need to. `T3CODE_OTLP_SERVICE_NAME` is
+  still honored, because it is T3 Code's own variable and nobody exports it
+  fleet-wide by accident.
+
+## Why
+
+This reverses part of 0018, which honored `OTEL_SERVICE_NAME` because every
+other OpenTelemetry SDK does. Consistency was the wrong thing to optimize for
+here.
+
+A service name is not a preference, it is a key. Endpoints, headers, protocols,
+and resource attributes are all things a machine legitimately knows better than
+the app does, which is why reading them from the environment is right. A service
+name is the opposite: it is the identity every dashboard, alert, and saved query
+is keyed on, and it is worth exactly as much as it is stable. One ambient
+variable, exported years ago in a shell profile for a different app, silently
+merges T3 Code into that app's dashboards and pulls it out of its own.
+
+The failure mode is what makes it worth diverging over. It is invisible from
+inside the app, the telemetry keeps flowing, and every panel still renders. What
+you get is not an empty dashboard, which someone would investigate, but a
+plausible one that is quietly describing two applications at once.
+
+Worth being honest that the specification does not settle this. It fixes the
+precedence between `OTEL_SERVICE_NAME` and a `service.name` in
+`OTEL_RESOURCE_ATTRIBUTES`, and then leaves environment-versus-code to whichever
+order an SDK happens to merge its resources in. Most SDKs let hardcoded values
+win, which is the same answer this reaches. The difference is that they reach it
+silently and this says so out loud.
+
+## Upstream considerations
+
+The server half of this is not a divergence at all: it restores upstream's
+behavior, which was static `t3-server` with `T3CODE_OTLP_SERVICE_NAME` as the
+only override. 0018 is what moved away from that, and this moves back. Upstream
+taking 0018 should take this with it.
+
+The rebase burden is one line per process plus the absence of a field. The
+environment reader has no `serviceName` in its resource type at all, so a sync
+that reintroduces the variable has to add the field back before it can be wired
+anywhere, rather than silently succeeding.
diff --git a/docs/fork/README.md b/docs/fork/README.md
index 14b71c5ac977..3a8968263182 100644
--- a/docs/fork/README.md
+++ b/docs/fork/README.md
@@ -61,3 +61,5 @@ Each entry uses these sections:
   active, [#34](https://github.com/TrogonStack/t3code/pull/34)
 - **0022** [The desktop app reports its own work](./0022-the-desktop-app-reports-its-own-work.md)
   active, [#35](https://github.com/TrogonStack/t3code/pull/35)
+- **0023** [A service name is not an environment variable](./0023-a-service-name-is-not-an-environment-variable.md)
+  active, [#36](https://github.com/TrogonStack/t3code/pull/36)
diff --git a/docs/operations/observability.md b/docs/operations/observability.md
index eaba1f8b739b..84d6eead4b9c 100644
--- a/docs/operations/observability.md
+++ b/docs/operations/observability.md
@@ -187,7 +187,7 @@ it, T3 Code joins in without being told twice. Nothing above is required:
 
 ```bash
 export OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318
-export OTEL_SERVICE_NAME=t3-local
+export OTEL_RESOURCE_ATTRIBUTES=deployment.environment=lab
 ```
 
 The base endpoint is a base, not a full URL: traces go to `<endpoint>/v1/traces`, metrics to
@@ -202,11 +202,27 @@ T3 Code exports to it, so use `OTEL_SDK_DISABLED=true` if that is not what you w
 The desktop app is two processes, and each is its own OpenTelemetry producer:
 
 - **The server**, under service name `t3-server`.
-- **The Electron main process**, under service name `desktop`. It owns app startup, window and menu
-  work, backend supervision, and updates, none of which the server can see. It reads the same
+- **The Electron main process**, under service name `t3-desktop`. It owns app startup, window and
+  menu work, backend supervision, and updates, none of which the server can see. It reads the same
   sources in the same order as the server, so a machine that points one of them at a collector
-  points both. `OTEL_SERVICE_NAME` renames it; `service.runtime` stays `desktop` no matter what
-  `OTEL_RESOURCE_ATTRIBUTES` says, so the two processes cannot be confused for each other.
+  points both.
+
+The web client reports as `t3-web`, so the three service names are `t3-server`, `t3-desktop`, and
+`t3-web`.
+
+**Service names are static and the environment cannot change them.** `OTEL_SERVICE_NAME` and a
+`service.name` inside `OTEL_RESOURCE_ATTRIBUTES` are both refused, with a warning naming the one you
+set. This is a deliberate departure from what most OpenTelemetry SDKs do, and the reason is that a
+service name is not a preference: renaming one process merges two services in every dashboard built
+on them, and a shell profile that names the app it was written for should not be able to do that to
+T3 Code. Use `OTEL_RESOURCE_ATTRIBUTES` to tell instances apart, which is what it is for:
+
+```bash
+export OTEL_RESOURCE_ATTRIBUTES=service.instance.id=laptop-01,deployment.environment=lab
+```
+
+`T3CODE_OTLP_SERVICE_NAME` still renames the server, because it is T3 Code's own variable and nobody
+sets it across a fleet by accident. There is no equivalent for the main process.
 
 On macOS, ambient variables reach the desktop app only when it is launched from a shell. Opening it
 from the Dock, Finder, or Spotlight inherits `launchd`'s environment instead, which is why the
@@ -245,7 +261,8 @@ Settings.
 | `OTEL_EXPORTER_OTLP_HEADERS`, `OTEL_EXPORTER_OTLP_{TRACES,METRICS,LOGS}_HEADERS`     | Export headers, per signal overriding the shared ones                        |
 | `OTEL_EXPORTER_OTLP_PROTOCOL`, `OTEL_EXPORTER_OTLP_{TRACES,METRICS,LOGS}_PROTOCOL`   | `http/protobuf` (default) or `http/json`                                     |
 | `OTEL_{TRACES,METRICS,LOGS}_EXPORTER`                                                | A list; the signal is exported when it contains `otlp`, which is the default |
-| `OTEL_SERVICE_NAME`, `OTEL_SERVICE_VERSION`, `OTEL_RESOURCE_ATTRIBUTES`              | Resource identity attached to every span, metric, and log record             |
+| `OTEL_SERVICE_VERSION`, `OTEL_RESOURCE_ATTRIBUTES`                                   | Resource identity attached to every span, metric, and log record             |
+| `OTEL_SERVICE_NAME`                                                                  | Refused with a warning; service names are static                             |
 | `OTEL_BSP_SCHEDULE_DELAY`, `OTEL_METRIC_EXPORT_INTERVAL`, `OTEL_BLRP_SCHEDULE_DELAY` | Export interval, one per signal                                              |
 | `OTEL_BSP_MAX_EXPORT_BATCH_SIZE`, `OTEL_BLRP_MAX_EXPORT_BATCH_SIZE`                  | Spans per batch, log records per batch                                       |
 | `OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE`                                  | `cumulative` or `delta`                                                      |
@@ -292,6 +309,10 @@ Not everything in the specification is implemented. These are the ones worth kno
 - **`OTEL_SERVICE_VERSION` is not a specification variable.** It is read as a convenience because
   the exporter library reads it too. `OTEL_RESOURCE_ATTRIBUTES=service.version=...` is the portable
   spelling.
+- **`service.name` cannot be set from the environment.** See Which Processes Export above.
+  `OTEL_SERVICE_NAME` and `OTEL_RESOURCE_ATTRIBUTES=service.name=...` are both refused with a
+  warning, and the `service.name` key is dropped rather than passed through so the exporter never
+  receives two of them.
 
 Everything else not listed above is ignored, including `OTEL_BSP_MAX_QUEUE_SIZE`,
 `OTEL_BLRP_MAX_QUEUE_SIZE`, `OTEL_BSP_EXPORT_TIMEOUT`, `OTEL_BLRP_EXPORT_TIMEOUT`, sampler
@@ -309,8 +330,9 @@ and both are logged once at startup:
 - **Export off.** Only `OTEL_EXPORTER_OTLP_PROTOCOL=grpc` does this, because it names a transport
   T3 Code does not speak rather than a value it failed to parse.
 
-An empty value means the same thing as an unset one, so `OTEL_SERVICE_NAME=` reads as if the
-variable were not there at all. `OTEL_SDK_DISABLED` follows the specification's one rule for
+An empty value means the same thing as an unset one, so `OTEL_SERVICE_VERSION=` reads as if the
+variable were not there at all. An empty `OTEL_SERVICE_NAME` is not an attempt to rename anything,
+so it is not warned about either. `OTEL_SDK_DISABLED` follows the specification's one rule for
 booleans: the case-insensitive string `true` is the only value that switches export off, and
 anything else, including `yes` and `1`, leaves it on.
 
@@ -686,7 +708,7 @@ OTLP export:
 - `T3CODE_OTLP_LOGS_URL`: OTLP log endpoint
 - `T3CODE_OTLP_EXPORT_INTERVAL_MS`: export interval, default `10000`
 - `T3CODE_OTLP_SERVICE_NAME`: server service name, default `t3-server`. The Electron main process
-  does not read it; rename that one with `OTEL_SERVICE_NAME`.
+  does not read it and is always `t3-desktop`.
 
 If the OTLP URLs are unset, local tracing still works and metrics stay in-process only.
 
diff --git a/packages/shared/src/otelEnvironment.test.ts b/packages/shared/src/otelEnvironment.test.ts
index e0609c41d8d0..dda0afb7f6dd 100644
--- a/packages/shared/src/otelEnvironment.test.ts
+++ b/packages/shared/src/otelEnvironment.test.ts
@@ -130,18 +130,17 @@ describe("OtelEnvironment", () => {
     }),
   );
 
-  it.effect("reads the service identity and the leftover resource attributes", () =>
+  it.effect("reads the service version and the leftover resource attributes", () =>
     Effect.gen(function* () {
       const resolved = yield* OtelEnvironment.load.pipe(
         withEnv({
-          OTEL_RESOURCE_ATTRIBUTES: "org.name=Example,service.name=from-attributes,deployment=prod",
+          OTEL_RESOURCE_ATTRIBUTES: "org.name=Example,deployment=prod",
           OTEL_SERVICE_VERSION: "1.2.3",
         }),
       );
-      assert.strictEqual(resolved.resource.serviceName, "from-attributes");
       assert.strictEqual(resolved.resource.serviceVersion, "1.2.3");
-      // service.name and service.version become the named fields, so leaving
-      // them in the attribute bag too would send each one twice.
+      // service.version becomes a named field, so leaving it in the attribute
+      // bag too would send it twice.
       assert.deepStrictEqual(resolved.resource.attributes, {
         "org.name": "Example",
         deployment: "prod",
@@ -149,7 +148,30 @@ describe("OtelEnvironment", () => {
     }),
   );
 
-  it.effect("lets OTEL_SERVICE_NAME win over the resource attribute", () =>
+  it.effect("refuses to rename the service, and says so", () =>
+    Effect.gen(function* () {
+      const resolved = yield* OtelEnvironment.load.pipe(
+        withEnv({ OTEL_SERVICE_NAME: "some-other-app" }),
+      );
+      assert.deepStrictEqual(resolved.resource.attributes, {});
+      assert.lengthOf(resolved.warnings, 1);
+      assert.include(resolved.warnings[0] ?? "", "OTEL_SERVICE_NAME was ignored");
+    }),
+  );
+
+  it.effect("drops a service.name hidden in the resource attributes", () =>
+    Effect.gen(function* () {
+      const resolved = yield* OtelEnvironment.load.pipe(
+        withEnv({ OTEL_RESOURCE_ATTRIBUTES: "service.name=some-other-app,host.name=lab-01" }),
+      );
+      // Dropped rather than passed through, or the exporter would receive a
+      // second service.name beside the one the process chose.
+      assert.deepStrictEqual(resolved.resource.attributes, { "host.name": "lab-01" });
+      assert.include(resolved.warnings[0] ?? "", "service.name was ignored");
+    }),
+  );
+
+  it.effect("names OTEL_SERVICE_NAME rather than the attribute when both are set", () =>
     Effect.gen(function* () {
       const resolved = yield* OtelEnvironment.load.pipe(
         withEnv({
@@ -157,7 +179,8 @@ describe("OtelEnvironment", () => {
           OTEL_RESOURCE_ATTRIBUTES: "service.name=from-attributes",
         }),
       );
-      assert.strictEqual(resolved.resource.serviceName, "explicit");
+      assert.lengthOf(resolved.warnings, 1);
+      assert.include(resolved.warnings[0] ?? "", "OTEL_SERVICE_NAME was ignored");
     }),
   );
 
@@ -468,7 +491,8 @@ describe("OtelEnvironment", () => {
           OTEL_EXPORTER_OTLP_TRACES_ENDPOINT: "",
         }),
       );
-      assert.strictEqual(resolved.resource.serviceName, undefined);
+      // An empty rename is not a rename, so it is not worth a warning either.
+      assert.deepStrictEqual(resolved.warnings, []);
       assert.strictEqual(resolved.traces.settings?.url, "https://collector.example.com/v1/traces");
     }),
   );
@@ -545,11 +569,11 @@ describe("OtelEnvironment", () => {
       const resolved = yield* OtelEnvironment.load.pipe(
         withEnv({
           OTEL_EXPORTER_OTLP_ENDPOINT: "  https://collector.example.com/  ",
-          OTEL_SERVICE_NAME: "  t3  ",
+          OTEL_SERVICE_VERSION: "  1.2.3  ",
         }),
       );
       assert.strictEqual(resolved.traces.settings?.url, "https://collector.example.com/v1/traces");
-      assert.strictEqual(resolved.resource.serviceName, "t3");
+      assert.strictEqual(resolved.resource.serviceVersion, "1.2.3");
     }),
   );
 
diff --git a/packages/shared/src/otelEnvironment.ts b/packages/shared/src/otelEnvironment.ts
index dcf90dee3d7e..b8e53e49a8e7 100644
--- a/packages/shared/src/otelEnvironment.ts
+++ b/packages/shared/src/otelEnvironment.ts
@@ -71,8 +71,15 @@ export interface OtlpSignal {
   readonly declined: string | undefined;
 }
 
+/**
+ * What the environment may contribute to the resource. `service.name` is
+ * deliberately absent: each T3 Code process names itself and nothing here can
+ * rename it, so a fleet-wide `OTEL_SERVICE_NAME` cannot quietly merge two
+ * processes into one service or file T3 Code under some other app's name. An
+ * attempt to set it is reported through `warnings` rather than ignored in
+ * silence.
+ */
 export interface OtlpResourceSettings {
-  readonly serviceName: string | undefined;
   readonly serviceVersion: string | undefined;
   readonly attributes: Readonly<Record<string, string>>;
 }
@@ -412,13 +419,28 @@ const resolveResource = Effect.gen(function* () {
     "service.version": attributeVersion,
     ...rest
   } = parsed.value ?? {};
+  // Named here only to say it was refused. Dropping it without a word is the
+  // failure this variable is prone to: the name never changes, the dashboards
+  // stay empty, and nothing in the log connects the two.
+  const declinedName =
+    (yield* optionalString("OTEL_SERVICE_NAME")) === undefined
+      ? attributeName === undefined
+        ? undefined
+        : "OTEL_RESOURCE_ATTRIBUTES=service.name"
+      : "OTEL_SERVICE_NAME";
   return {
     value: {
-      serviceName: (yield* optionalString("OTEL_SERVICE_NAME")) ?? attributeName,
       serviceVersion: (yield* optionalString("OTEL_SERVICE_VERSION")) ?? attributeVersion,
       attributes: rest,
     },
-    warnings: parsed.warnings,
+    warnings: [
+      ...parsed.warnings,
+      ...(declinedName === undefined
+        ? []
+        : [
+            `${declinedName} was ignored; every T3 Code process names itself, so use OTEL_RESOURCE_ATTRIBUTES to tell instances apart instead`,
+          ]),
+    ],
   } satisfies Parsed<OtlpResourceSettings>;
 });
 
@@ -486,7 +508,7 @@ export const load: Effect.Effect<OtelEnvironment> = Effect.gen(function* () {
         traces: { settings: undefined, declined: UNREADABLE },
         metrics: { settings: undefined, declined: UNREADABLE },
         logs: { settings: undefined, declined: UNREADABLE },
-        resource: { serviceName: undefined, serviceVersion: undefined, attributes: {} },
+        resource: { serviceVersion: undefined, attributes: {} },
       }),
     ),
   ),
@@ -502,5 +524,5 @@ export const none: OtelEnvironment = {
   traces: noSignal,
   metrics: noSignal,
   logs: noSignal,
-  resource: { serviceName: undefined, serviceVersion: undefined, attributes: {} },
+  resource: { serviceVersion: undefined, attributes: {} },
 };