diff --git a/npm-packages/convex/src/cli/lib/deployment.test.ts b/npm-packages/convex/src/cli/lib/deployment.test.ts
index 24f13c750..dff7b777e 100644
--- a/npm-packages/convex/src/cli/lib/deployment.test.ts
+++ b/npm-packages/convex/src/cli/lib/deployment.test.ts
@@ -1,5 +1,14 @@
-import { test, expect } from "vitest";
-import { changesToEnvVarFile, changesToGitIgnore } from "./deployment.js";
+import { test, expect, vi, beforeEach, afterEach } from "vitest";
+import { changesToEnvVarFile, changesToGitIgnore, writeDeploymentEnvVar } from "./deployment.js";
+import { Context } from "../../bundler/context.js";
+
+vi.mock("./envvars.js", async (importOriginal) => {
+  const actual = (await importOriginal()) as any;
+  return {
+    ...actual,
+    gitIgnoreEnvVarFile: vi.fn().mockResolvedValue(false),
+  };
+});
 
 const DEPLOYMENT = {
   team: "snoops",
@@ -83,3 +92,40 @@ test("git ignore changes", () => {
     "!.env.local\n.env.local\n",
   );
 });
+
+const mockContext = {
+  fs: {
+    exists: vi.fn(),
+    readUtf8File: vi.fn(),
+    writeUtf8File: vi.fn(),
+  },
+} as unknown as Context;
+
+const originalProcessEnv = process.env;
+
+beforeEach(() => {
+  vi.clearAllMocks();
+  process.env = { ...originalProcessEnv };
+});
+
+afterEach(() => {
+  process.env = originalProcessEnv;
+});
+
+test("writeDeploymentEnvVar skips file creation when CONVEX_DEPLOYMENT exists with correct value", async () => {
+  process.env.CONVEX_DEPLOYMENT = "prod:tall-bar";
+
+  const result = await writeDeploymentEnvVar(
+    mockContext,
+    "prod",
+    DEPLOYMENT,
+    null,
+  );
+
+  expect(result).toEqual({
+    wroteToGitIgnore: false,
+    changedDeploymentEnvVar: false,
+  });
+
+  expect(mockContext.fs.writeUtf8File).not.toHaveBeenCalled();
+});
diff --git a/npm-packages/convex/src/cli/lib/deployment.ts b/npm-packages/convex/src/cli/lib/deployment.ts
index 4bb41299c..3f83c4acc 100644
--- a/npm-packages/convex/src/cli/lib/deployment.ts
+++ b/npm-packages/convex/src/cli/lib/deployment.ts
@@ -49,6 +49,17 @@ export async function writeDeploymentEnvVar(
   },
   existingValue: string | null,
 ): Promise<{ wroteToGitIgnore: boolean; changedDeploymentEnvVar: boolean }> {
+  const deploymentEnvVarValue =
+    deploymentType + ":" + deployment.deploymentName;
+
+  // Check if the correct value already exists in process.env
+  if (process.env[CONVEX_DEPLOYMENT_ENV_VAR_NAME] === deploymentEnvVarValue) {
+    return {
+      wroteToGitIgnore: false,
+      changedDeploymentEnvVar: false,
+    };
+  }
+
   const existingFile = ctx.fs.exists(ENV_VAR_FILE_PATH)
     ? ctx.fs.readUtf8File(ENV_VAR_FILE_PATH)
     : null;
@@ -57,8 +68,6 @@ export async function writeDeploymentEnvVar(
     deploymentType,
     deployment,
   );
-  const deploymentEnvVarValue =
-    deploymentType + ":" + deployment.deploymentName;
 
   if (changedFile !== null) {
     ctx.fs.writeUtf8File(ENV_VAR_FILE_PATH, changedFile);
diff --git a/npm-packages/convex/src/cli/lib/envvars.test.ts b/npm-packages/convex/src/cli/lib/envvars.test.ts
new file mode 100644
index 000000000..5bf53f6ed
--- /dev/null
+++ b/npm-packages/convex/src/cli/lib/envvars.test.ts
@@ -0,0 +1,66 @@
+import {afterEach, beforeEach, expect, test, vi} from "vitest";
+import {writeConvexUrlToEnvFile} from "./envvars.js";
+import {Context} from "../../bundler/context.js";
+
+vi.mock("./utils/utils.js", () => ({
+	loadPackageJson: vi.fn().mockResolvedValue({name: "test-project"}),
+	ENV_VAR_FILE_PATH: ".env.local",
+}));
+
+const mockContext = {
+	fs: {
+		exists: vi.fn() as any,
+		readUtf8File: vi.fn() as any,
+		writeUtf8File: vi.fn() as any,
+	},
+	crash: vi.fn() as any,
+} as unknown as Context;
+
+const originalProcessEnv = process.env;
+
+beforeEach(() => {
+	vi.clearAllMocks();
+	process.env = {...originalProcessEnv};
+});
+
+afterEach(() => {
+	process.env = originalProcessEnv;
+});
+
+test("writeConvexUrlToEnvFile process.env behavior", async () => {
+	// Test core functionality: skip file creation when env var exists with correct value
+	process.env.CONVEX_URL = "https://test.convex.cloud";
+	(mockContext.fs.exists as any).mockReturnValue(false);
+
+	let result = await writeConvexUrlToEnvFile(mockContext, "https://test.convex.cloud");
+	expect(result).toBeNull(); // Should skip file creation
+	expect(mockContext.fs.writeUtf8File).not.toHaveBeenCalled();
+
+	// Test different value - should create file
+	vi.clearAllMocks();
+	process.env.CONVEX_URL = "https://different.convex.cloud";
+
+	result = await writeConvexUrlToEnvFile(mockContext, "https://test.convex.cloud");
+	expect(result).not.toBeNull(); // Should create file
+	expect(mockContext.fs.writeUtf8File).toHaveBeenCalled();
+
+	// Test missing env var - should create file
+	vi.clearAllMocks();
+	delete process.env.CONVEX_URL;
+
+	result = await writeConvexUrlToEnvFile(mockContext, "https://test.convex.cloud");
+	expect(result).not.toBeNull(); // Should create file
+	expect(mockContext.fs.writeUtf8File).toHaveBeenCalled();
+
+	// Empty string should trigger file creation
+	vi.clearAllMocks();
+	process.env.CONVEX_URL = "";
+	result = await writeConvexUrlToEnvFile(mockContext, "https://test.convex.cloud");
+	expect(result).not.toBeNull();
+
+	// Whitespace should trigger file creation
+	vi.clearAllMocks();
+	process.env.CONVEX_URL = "  ";
+	result = await writeConvexUrlToEnvFile(mockContext, "https://test.convex.cloud");
+	expect(result).not.toBeNull();
+});
diff --git a/npm-packages/convex/src/cli/lib/envvars.ts b/npm-packages/convex/src/cli/lib/envvars.ts
index 1d1f628a0..f64cfe280 100644
--- a/npm-packages/convex/src/cli/lib/envvars.ts
+++ b/npm-packages/convex/src/cli/lib/envvars.ts
@@ -29,6 +29,16 @@ export async function writeConvexUrlToEnvFile(
   ctx: Context,
   value: string,
 ): Promise<ConvexUrlWriteConfig> {
+  // Check if any of the expected environment variables already has the correct value
+  const { envVar: suggestedEnvVar } = await suggestedEnvVarName(ctx);
+  
+  // Check process.env for the suggested env var or any of the expected names
+  for (const envVarName of [suggestedEnvVar, ...EXPECTED_NAMES]) {
+    if (process.env[envVarName] === value) {
+      return null;
+    }
+  }
+
   const writeConfig = await envVarWriteConfig(ctx, value);
 
   if (writeConfig === null) {