diff --git a/packages/cli/src/analytics.test.ts b/packages/cli/src/analytics.test.ts
index 91bf3543..8cd8bd5b 100644
--- a/packages/cli/src/analytics.test.ts
+++ b/packages/cli/src/analytics.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from "vitest";
+import { afterEach, describe, expect, it, vi } from "vitest";
 
 import {
 	analyticsUserId,
@@ -8,6 +8,10 @@ import {
 	telemetryCredential,
 } from "./analytics.js";
 
+afterEach(() => {
+	vi.unstubAllEnvs();
+});
+
 describe("analyticsUserId", () => {
 	it("reports a run nothing identified as anonymous, not as an empty identity", () => {
 		expect(analyticsUserId("")).toBe("anonymous");
@@ -124,10 +128,12 @@ describe("getErrorAnalyticsEventProperties", () => {
 			{
 				version: "2.33.2",
 				ci: true,
+				agent: "codex",
 			},
 		);
 
 		expect(properties).toMatchObject({
+			agent: "codex",
 			ci: true,
 			errCode: "API_ERROR",
 			message: "branch already exists",
@@ -168,4 +174,17 @@ describe("getAnalyticsEventProperties", () => {
 			}).flags.output,
 		).toBe("secret-value");
 	});
+
+	it("attributes commands run by a coding agent", () => {
+		vi.stubEnv("CODEX_CI", undefined);
+		vi.stubEnv("CODEX_THREAD_ID", undefined);
+		vi.stubEnv("CODEX_SESSION_ID", undefined);
+		vi.stubEnv("CLAUDE_CODE_CHILD_SESSION", "1");
+
+		expect(
+			getAnalyticsEventProperties({
+				_: ["branches", "list"],
+			}).agent,
+		).toBe("claude-code");
+	});
 });
diff --git a/packages/cli/src/analytics.ts b/packages/cli/src/analytics.ts
index 6a2c201d..20ab66c0 100644
--- a/packages/cli/src/analytics.ts
+++ b/packages/cli/src/analytics.ts
@@ -5,7 +5,7 @@ import { type AuthContext, getAuthContext } from "./auth_context.js";
 import { credentialsPath } from "./config.js";
 import { isCurrentBranchProbe } from "./context.js";
 import { storeFor } from "./credential_io.js";
-import { getGithubEnvVars, isCi } from "./env.js";
+import { getCliAgent, getGithubEnvVars, isCi } from "./env.js";
 import type { ErrorCode } from "./errors.js";
 import { log } from "./log.js";
 import pkg from "./pkg.js";
@@ -124,12 +124,14 @@ type AnalyticsEventProperties = {
 		output: string | undefined;
 	};
 	ci: boolean;
+	agent: ReturnType<typeof getCliAgent>;
 	githubEnvVars: ReturnType<typeof getGithubEnvVars>;
 };
 
 type ErrorEventContext = {
 	version: string;
 	ci: boolean;
+	agent: ReturnType<typeof getCliAgent>;
 };
 
 /**
@@ -331,6 +333,7 @@ const getErrorAnalyticsEventContext = (
 ): ErrorEventContext => ({
 	version: pkg.version,
 	ci: isCi(),
+	agent: getCliAgent(process.env),
 });
 
 export const getAnalyticsEventProperties = (
@@ -342,5 +345,6 @@ export const getAnalyticsEventProperties = (
 		output: args.output,
 	},
 	ci: isCi(),
+	agent: getCliAgent(process.env),
 	githubEnvVars: getGithubEnvVars(process.env),
 });
diff --git a/packages/cli/src/env.test.ts b/packages/cli/src/env.test.ts
index 8860decc..ca607766 100644
--- a/packages/cli/src/env.test.ts
+++ b/packages/cli/src/env.test.ts
@@ -1,5 +1,74 @@
 import { describe, expect, it } from "vitest";
-import { getGithubEnvVars } from "./env";
+import { getCliAgent, getGithubEnvVars } from "./env";
+
+describe("getCliAgent", () => {
+	it("attributes a Claude Code child session", () => {
+		expect(getCliAgent({ CLAUDE_CODE_CHILD_SESSION: "1" })).toBe(
+			"claude-code",
+		);
+	});
+
+	it("attributes a Codex thread", () => {
+		expect(
+			getCliAgent({
+				CODEX_CI: "1",
+				CODEX_THREAD_ID: "thread-123",
+			}),
+		).toBe("codex");
+	});
+
+	it("attributes a Codex session", () => {
+		expect(
+			getCliAgent({
+				CODEX_CI: "1",
+				CODEX_SESSION_ID: "session-123",
+			}),
+		).toBe("codex");
+	});
+
+	it("does not attribute a user-initiated Codex shell command", () => {
+		expect(
+			getCliAgent({
+				CODEX_THREAD_ID: "thread-123",
+				CODEX_SESSION_ID: "session-123",
+			}),
+		).toBeUndefined();
+	});
+
+	it("does not attribute disabled or empty direct markers", () => {
+		expect(
+			getCliAgent({
+				CLAUDE_CODE_CHILD_SESSION: "false",
+				CODEX_THREAD_ID: "",
+				CODEX_SESSION_ID: " ",
+			}),
+		).toBeUndefined();
+	});
+
+	it("does not attribute ambient or sandbox utility markers", () => {
+		expect(
+			getCliAgent({
+				CLAUDECODE: "1",
+				CLAUDE_CODE: "1",
+				CLAUDE_CLI: "1",
+				CODEX: "1",
+				CODEX_CI: "1",
+				CODEX_SANDBOX: "seatbelt",
+				CODEX_SANDBOX_NETWORK_DISABLED: "1",
+			}),
+		).toBeUndefined();
+	});
+
+	it("omits attribution when nested agent markers conflict", () => {
+		expect(
+			getCliAgent({
+				CLAUDE_CODE_CHILD_SESSION: "1",
+				CODEX_CI: "1",
+				CODEX_THREAD_ID: "thread-123",
+			}),
+		).toBeUndefined();
+	});
+});
 
 describe("getGithubEnvVars", () => {
 	it("success all keys", () => {
diff --git a/packages/cli/src/env.ts b/packages/cli/src/env.ts
index 6b5132e2..fd0f1dd2 100644
--- a/packages/cli/src/env.ts
+++ b/packages/cli/src/env.ts
@@ -6,6 +6,19 @@ export const isDebug = () => {
 	return Boolean(process.env.DEBUG);
 };
 
+export type CliAgent = "claude-code" | "codex";
+
+export const getCliAgent = (env: NodeJS.Dict<string>): CliAgent | undefined => {
+	const claudeCode = env.CLAUDE_CODE_CHILD_SESSION === "1";
+	const codex =
+		env.CODEX_CI === "1" &&
+		(Boolean(env.CODEX_THREAD_ID?.trim()) ||
+			Boolean(env.CODEX_SESSION_ID?.trim()));
+
+	if (claudeCode === codex) return undefined;
+	return claudeCode ? "claude-code" : "codex";
+};
+
 export const getGithubEnvVars = (env: NodeJS.Dict<string>) => {
 	const vars = [
 		// github action info
diff --git a/packages/cli/src/init/agent_snapshot.test.ts b/packages/cli/src/init/agent_snapshot.test.ts
index f816583f..d6cd1d55 100644
--- a/packages/cli/src/init/agent_snapshot.test.ts
+++ b/packages/cli/src/init/agent_snapshot.test.ts
@@ -344,7 +344,8 @@ async function runInit(
 		});
 	}
 
-	const child = spawn(process.execPath, [CLI, "init", ...args], {
+	const cliArgs = [CLI, "--no-analytics", "init", ...args];
+	const child = spawn(process.execPath, cliArgs, {
 		cwd,
 		stdio: ["ignore", "pipe", "pipe"],
 		env: {
@@ -355,7 +356,6 @@ async function runInit(
 			NEON_CONFIG_DIR: configDir,
 			NEON_STUB_LOG: stubLog,
 			NEON_BOOTSTRAP_MANIFEST_URL: manifestUrl,
-			NEON_NO_ANALYTICS: "1",
 			CI: "true",
 			NO_COLOR: "1",
 			FORCE_COLOR: "0",
diff --git a/packages/cli/src/init/auth.test.ts b/packages/cli/src/init/auth.test.ts
index 98626225..5335d799 100644
--- a/packages/cli/src/init/auth.test.ts
+++ b/packages/cli/src/init/auth.test.ts
@@ -204,7 +204,8 @@ describe("`neon init` failure output", { timeout: 20_000 }, () => {
 		writeFileSync(resolve(configDir, "credentials.json"), credentials, {
 			mode: 0o600,
 		});
-		const result = spawnSync(process.execPath, [CLI, "init", ...args], {
+		const cliArgs = [CLI, "--no-analytics", "init", ...args];
+		const result = spawnSync(process.execPath, cliArgs, {
 			cwd,
 			encoding: "utf8",
 			stdio: ["ignore", "pipe", "pipe"],
@@ -212,7 +213,6 @@ describe("`neon init` failure output", { timeout: 20_000 }, () => {
 				PATH: process.env.PATH ?? "",
 				HOME: process.env.HOME ?? "",
 				NEON_CONFIG_DIR: configDir,
-				NEON_NO_ANALYTICS: "1",
 			},
 		});
 		return { ...result, configDir };