diff --git a/src/telemetry.ts b/src/telemetry.ts
index dd4993c..bdf99cf 100644
--- a/src/telemetry.ts
+++ b/src/telemetry.ts
@@ -213,6 +213,7 @@ export function createTelemetry({
   if (
     config.enabled === false
     || isTelemetryDisabledByEnv(env)
+    || isRunningInCI(env)
     || !INSTALL_ID_PATTERN.test(config.installId)
     || !resolvedSink
   ) {
@@ -332,6 +333,17 @@ function isTelemetryDisabledByEnv(env: Record<string, string | undefined>): bool
   return value !== undefined && DISABLED_ENV_VALUES.has(value);
 }
 
+function isRunningInCI(env: Record<string, string | undefined>): boolean {
+  // Most CI providers set `CI=true` (GitHub Actions, CircleCI, GitLab,
+  // Travis, Buildkite, Jenkins via plugins, etc.). We also check the
+  // GitHub Actions-specific marker as belt-and-braces, in case some
+  // future provider drops the conventional `CI` variable.
+  return (
+    env.CI?.trim().toLowerCase() === "true"
+    || env.GITHUB_ACTIONS?.trim().toLowerCase() === "true"
+  );
+}
+
 function resolveConfiguredHost(
   env: Record<string, string | undefined>,
   config: TelemetryConfig,
diff --git a/test/telemetry.test.ts b/test/telemetry.test.ts
index 2f4ce07..4977981 100644
--- a/test/telemetry.test.ts
+++ b/test/telemetry.test.ts
@@ -196,6 +196,73 @@ test("AGENTRAIL_TELEMETRY_DISABLED=1 wins over enabled config", async () => {
   assert.deepEqual(delivered, []);
 });
 
+test("CI=true suppresses telemetry even with enabled config", async () => {
+  const delivered: TelemetrySinkEvent[] = [];
+  const telemetry = createTelemetry({
+    source: "cli",
+    version: "0.1.6",
+    config: {
+      enabled: true,
+      installId,
+      provider: "posthog",
+      host: DEFAULT_POSTHOG_HOST,
+    },
+    env: { CI: "true" },
+    sink: async (event) => {
+      delivered.push(event);
+    },
+  });
+
+  await telemetry.capture("init_started", { provider: "github" });
+
+  assert.deepEqual(delivered, []);
+});
+
+test("GITHUB_ACTIONS=true suppresses telemetry even without CI variable", async () => {
+  const delivered: TelemetrySinkEvent[] = [];
+  const telemetry = createTelemetry({
+    source: "cli",
+    version: "0.1.6",
+    config: {
+      enabled: true,
+      installId,
+      provider: "posthog",
+      host: DEFAULT_POSTHOG_HOST,
+    },
+    env: { GITHUB_ACTIONS: "true" },
+    sink: async (event) => {
+      delivered.push(event);
+    },
+  });
+
+  await telemetry.capture("init_started", { provider: "github" });
+
+  assert.deepEqual(delivered, []);
+});
+
+test("CI=false does not suppress telemetry", async () => {
+  const delivered: TelemetrySinkEvent[] = [];
+  const telemetry = createTelemetry({
+    source: "cli",
+    version: "0.1.6",
+    config: {
+      enabled: true,
+      installId,
+      provider: "posthog",
+      host: DEFAULT_POSTHOG_HOST,
+    },
+    env: { CI: "false" },
+    sink: async (event) => {
+      delivered.push(event);
+    },
+  });
+
+  await telemetry.capture("init_started", { provider: "github" });
+
+  assert.equal(delivered.length, 1);
+  assert.equal(delivered[0].event, "init_started");
+});
+
 test("invalid install id telemetry sends nothing", async () => {
   const delivered: TelemetrySinkEvent[] = [];
   const telemetry = createTelemetry({