diff --git a/.changeset/platform-api-url-credential-warning.md b/.changeset/platform-api-url-credential-warning.md
new file mode 100644
index 00000000..a34a0185
--- /dev/null
+++ b/.changeset/platform-api-url-credential-warning.md
@@ -0,0 +1,5 @@
+---
+"clerk": patch
+---
+
+Warn (in human mode) when `CLERK_PLATFORM_API_URL` routes requests to a host that differs from the active environment's URL, since credentials are keyed by environment name and not by URL. `clerk doctor` now also reports the active environment and its API URL so the mismatch is visible.
diff --git a/packages/cli-core/src/cli-program.ts b/packages/cli-core/src/cli-program.ts
index a8e7f113..85300be2 100644
--- a/packages/cli-core/src/cli-program.ts
+++ b/packages/cli-core/src/cli-program.ts
@@ -26,6 +26,7 @@ import {
   getCurrentEnvName,
   getAvailableEnvs,
   getPlapiBaseUrl,
+  isPlatformApiUrlOverridden,
 } from "./lib/environment.ts";
 import {
   CliError,
@@ -129,6 +130,17 @@ export function createProgram(): Program {
     if (activeEnv !== "production") {
       process.stderr.write(`[${activeEnv.toUpperCase()}]\n`);
     }
+
+    // Warn when CLERK_PLATFORM_API_URL routes requests to a different host than
+    // the active environment's platform URL. Credentials are keyed by environment
+    // name, so the active env's token will be sent to the override host. Emitted
+    // to stderr so it never corrupts stdout data output.
+    const override = isPlatformApiUrlOverridden();
+    if (override.overridden) {
+      log.warn(
+        `CLERK_PLATFORM_API_URL is routing requests to ${override.overrideUrl}, but credentials stay keyed to the "${override.envName}" environment — the "${override.envName}" token will be sent to that host.`,
+      );
+    }
   });
 
   // Show update notification after each command, except for commands that
diff --git a/packages/cli-core/src/commands/doctor/checks.ts b/packages/cli-core/src/commands/doctor/checks.ts
index b8bf9afa..53929eec 100644
--- a/packages/cli-core/src/commands/doctor/checks.ts
+++ b/packages/cli-core/src/commands/doctor/checks.ts
@@ -16,6 +16,7 @@ import {
   formatChannelLabel,
 } from "../../lib/update-check.ts";
 import { formatHostStateProbeFailures, getAgentHostStateProbe } from "../../lib/host-execution.ts";
+import { getCurrentEnvName, getPlapiBaseUrl } from "../../lib/environment.ts";
 import { isAgent } from "../../mode.ts";
 import type { CheckResult, DoctorContext, FixAction } from "./types.ts";
 
@@ -74,7 +75,7 @@ export async function checkLoggedIn(ctx: DoctorContext): Promise<CheckResult> {
       remedy: "Run `clerk auth login` to authenticate.",
     });
   }
-  return check.pass("Logged in (token found in credential store)");
+  return check.pass(`Logged in — environment "${getCurrentEnvName()}", API ${getPlapiBaseUrl()}`);
 }
 
 export async function checkHostExecution(): Promise<CheckResult> {
diff --git a/packages/cli-core/src/lib/environment.test.ts b/packages/cli-core/src/lib/environment.test.ts
new file mode 100644
index 00000000..827c51e1
--- /dev/null
+++ b/packages/cli-core/src/lib/environment.test.ts
@@ -0,0 +1,42 @@
+import { test, expect, describe, beforeEach, afterEach } from "bun:test";
+import { isPlatformApiUrlOverridden } from "./environment.ts";
+
+describe("isPlatformApiUrlOverridden", () => {
+  const original = process.env.CLERK_PLATFORM_API_URL;
+
+  beforeEach(() => {
+    delete process.env.CLERK_PLATFORM_API_URL;
+  });
+
+  afterEach(() => {
+    if (original === undefined) delete process.env.CLERK_PLATFORM_API_URL;
+    else process.env.CLERK_PLATFORM_API_URL = original;
+  });
+
+  test("returns overridden=true with URLs when the override differs from the active env URL", () => {
+    process.env.CLERK_PLATFORM_API_URL = "https://api.staging.example.com";
+    const result = isPlatformApiUrlOverridden();
+    expect(result.overridden).toBe(true);
+    if (!result.overridden) return;
+    expect(result.overrideUrl).toBe("https://api.staging.example.com");
+    expect(result.profileUrl).toBe("https://api.clerk.com");
+    expect(result.envName).toBe("production");
+  });
+
+  test("returns overridden=false when no override is set", () => {
+    const result = isPlatformApiUrlOverridden();
+    expect(result.overridden).toBe(false);
+  });
+
+  test("returns overridden=false when the override equals the active env URL", () => {
+    process.env.CLERK_PLATFORM_API_URL = "https://api.clerk.com";
+    const result = isPlatformApiUrlOverridden();
+    expect(result.overridden).toBe(false);
+  });
+
+  test("returns overridden=false when URLs differ only by trailing slash", () => {
+    process.env.CLERK_PLATFORM_API_URL = "https://api.clerk.com/";
+    const result = isPlatformApiUrlOverridden();
+    expect(result.overridden).toBe(false);
+  });
+});
diff --git a/packages/cli-core/src/lib/environment.ts b/packages/cli-core/src/lib/environment.ts
index 91643a28..c7fb9972 100644
--- a/packages/cli-core/src/lib/environment.ts
+++ b/packages/cli-core/src/lib/environment.ts
@@ -136,6 +136,42 @@ export function getPlapiBaseUrl(): string {
   return process.env.CLERK_PLATFORM_API_URL ?? getCurrentEnv().platformApiUrl;
 }
 
+/**
+ * Returns whether CLERK_PLATFORM_API_URL is set to a URL that differs from the
+ * active environment's configured platform URL, along with both URLs so the
+ * caller can surface a warning.
+ *
+ * Comparison normalises both URLs via `new URL().href` so trailing-slash and
+ * case differences are ignored; falls back to raw string comparison if either
+ * value is not a valid URL.
+ */
+export function isPlatformApiUrlOverridden():
+  | {
+      overridden: false;
+    }
+  | {
+      overridden: true;
+      overrideUrl: string;
+      profileUrl: string;
+      envName: string;
+    } {
+  const override = process.env.CLERK_PLATFORM_API_URL;
+  if (!override) return { overridden: false };
+
+  const profileUrl = getCurrentEnv().platformApiUrl;
+  const normalize = (u: string) => {
+    try {
+      return new URL(u).href;
+    } catch {
+      return u;
+    }
+  };
+
+  if (normalize(override) === normalize(profileUrl)) return { overridden: false };
+
+  return { overridden: true, overrideUrl: override, profileUrl, envName: getCurrentEnvName() };
+}
+
 export function getBapiBaseUrl(): string {
   return process.env.CLERK_BACKEND_API_URL ?? getCurrentEnv().backendApiUrl;
 }
diff --git a/packages/cli-core/src/test/integration/error-codes.test.ts b/packages/cli-core/src/test/integration/error-codes.test.ts
index 06c81e83..311675df 100644
--- a/packages/cli-core/src/test/integration/error-codes.test.ts
+++ b/packages/cli-core/src/test/integration/error-codes.test.ts
@@ -9,7 +9,12 @@ import { useIntegrationTestHarness, clerk, mockState } from "./lib/harness.ts";
 useIntegrationTestHarness();
 
 function parseJsonError(stderr: string): { code: string; message: string; docsUrl?: string } {
-  const parsed = JSON.parse(stderr);
+  const jsonLine = stderr
+    .split("\n")
+    .map((l) => l.trim())
+    .find((l) => l.startsWith("{"));
+  if (!jsonLine) throw new SyntaxError(`No JSON line found in stderr:\n${stderr}`);
+  const parsed = JSON.parse(jsonLine);
   return parsed.error;
 }
 
diff --git a/packages/cli-core/src/test/integration/input-json.test.ts b/packages/cli-core/src/test/integration/input-json.test.ts
index 0c23560b..13ef9238 100644
--- a/packages/cli-core/src/test/integration/input-json.test.ts
+++ b/packages/cli-core/src/test/integration/input-json.test.ts
@@ -18,6 +18,15 @@ useIntegrationTestHarness();
 
 const devInstance = getInstance(MOCK_APP, "development");
 
+function parseJsonFromStderr(stderr: string): { error: { code?: string } } {
+  const jsonLine = stderr
+    .split("\n")
+    .map((l) => l.trim())
+    .find((l) => l.startsWith("{"));
+  if (!jsonLine) throw new SyntaxError(`No JSON line found in stderr:\n${stderr}`);
+  return JSON.parse(jsonLine) as { error: { code?: string } };
+}
+
 beforeEach(async () => {
   await setProfile("github.com/test/project", {
     workspaceId: "",
@@ -40,7 +49,7 @@ test("explicit CLI flags override --input-json values", async () => {
   const result = await clerk.raw("init", "--input-json", '{"mode":"human"}', "--mode", "agent");
   expect(result.exitCode).not.toBe(0);
   // Agent mode emits structured JSON to stderr; human mode emits plain text.
-  const parsed = JSON.parse(result.stderr);
+  const parsed = parseJsonFromStderr(result.stderr);
   expect(parsed.error).toBeDefined();
 });
 
@@ -234,14 +243,14 @@ test("--input-json is registered as a global option", async () => {
   // stderr is the agent-mode signature, which proves --mode agent was applied.
   const result = await clerk.raw("--input-json", '{"mode":"agent"}', "doctor", "--json");
   expect(result.exitCode).not.toBe(0);
-  const parsed = JSON.parse(result.stderr);
+  const parsed = parseJsonFromStderr(result.stderr);
   expect(parsed.error).toBeDefined();
 });
 
 test("structured JSON error in agent mode for invalid JSON", async () => {
   const result = await clerk.raw("--mode", "agent", "init", "--input-json", "{bad}");
   expect(result.exitCode).not.toBe(0);
-  const parsed = JSON.parse(result.stderr);
+  const parsed = parseJsonFromStderr(result.stderr);
   expect(parsed.error.code).toBe("invalid_json");
 });
 
@@ -254,7 +263,7 @@ test("structured JSON error in agent mode for file not found", async () => {
     "@/tmp/does-not-exist-clerk.json",
   );
   expect(result.exitCode).not.toBe(0);
-  const parsed = JSON.parse(result.stderr);
+  const parsed = parseJsonFromStderr(result.stderr);
   expect(parsed.error.code).toBe("file_not_found");
 });
 
@@ -267,6 +276,6 @@ test("structured JSON error in agent mode for nested objects", async () => {
     '{"nested":{"key":"value"}}',
   );
   expect(result.exitCode).not.toBe(0);
-  const parsed = JSON.parse(result.stderr);
+  const parsed = parseJsonFromStderr(result.stderr);
   expect(parsed.error.code).toBe("invalid_json");
 });