diff --git a/packages/kbn-ci-stats-reporter/src/ci_stats_reporter.ts b/packages/kbn-ci-stats-reporter/src/ci_stats_reporter.ts
index 933f4ccdde0a3..73eecbda2ff3e 100644
--- a/packages/kbn-ci-stats-reporter/src/ci_stats_reporter.ts
+++ b/packages/kbn-ci-stats-reporter/src/ci_stats_reporter.ts
@@ -96,10 +96,8 @@ export interface CiStatsReportTestsOptions {
 }
 
 /* @internal */
-interface ReportTestsResponse {
-  buildId: string;
+interface ReportTestGroupResponse {
   groupId: string;
-  testRunCount: number;
 }
 
 /* @internal */
@@ -257,18 +255,51 @@ export class CiStatsReporter {
       );
     }
 
-    return await this.req<ReportTestsResponse>({
+    const groupResp = await this.req<ReportTestGroupResponse>({
       auth: true,
-      path: '/v1/test_group',
+      path: '/v2/test_group',
       query: {
         buildId: this.config?.buildId,
       },
-      bodyDesc: `[${group.name}/${group.type}] test groups with ${testRuns.length} tests`,
-      body: [
-        JSON.stringify({ group }),
-        ...testRuns.map((testRun) => JSON.stringify({ testRun })),
-      ].join('\n'),
+      bodyDesc: `[${group.name}/${group.type}] test group`,
+      body: group,
     });
+
+    if (!groupResp) {
+      return;
+    }
+
+    let bufferBytes = 0;
+    const buffer: string[] = [];
+    const flushBuffer = async () => {
+      await this.req<{ testRunCount: number }>({
+        auth: true,
+        path: '/v2/test_runs',
+        query: {
+          buildId: this.config?.buildId,
+          groupId: groupResp.groupId,
+          groupType: group.type,
+        },
+        bodyDesc: `[${group.name}/${group.type}] Chunk of ${bufferBytes} bytes`,
+        body: buffer.join('\n'),
+      });
+      buffer.length = 0;
+      bufferBytes = 0;
+    };
+
+    // send test runs in chunks of ~500kb
+    for (const testRun of testRuns) {
+      const json = JSON.stringify(testRun);
+      bufferBytes += json.length;
+      buffer.push(json);
+      if (bufferBytes >= 450000) {
+        await flushBuffer();
+      }
+    }
+
+    if (bufferBytes) {
+      await flushBuffer();
+    }
   }
 
   /**
diff --git a/packages/kbn-pm/dist/index.js b/packages/kbn-pm/dist/index.js
index df1391fe55dd8..b0aabefb1b0f2 100644
--- a/packages/kbn-pm/dist/index.js
+++ b/packages/kbn-pm/dist/index.js
@@ -1753,19 +1753,55 @@ class CiStatsReporter {
       throw new Error('unable to report tests unless buildId is configured and auth config available');
     }
 
-    return await this.req({
+    const groupResp = await this.req({
       auth: true,
-      path: '/v1/test_group',
+      path: '/v2/test_group',
       query: {
         buildId: (_this$config7 = this.config) === null || _this$config7 === void 0 ? void 0 : _this$config7.buildId
       },
-      bodyDesc: `[${group.name}/${group.type}] test groups with ${testRuns.length} tests`,
-      body: [JSON.stringify({
-        group
-      }), ...testRuns.map(testRun => JSON.stringify({
-        testRun
-      }))].join('\n')
+      bodyDesc: `[${group.name}/${group.type}] test group`,
+      body: group
     });
+
+    if (!groupResp) {
+      return;
+    }
+
+    let bufferBytes = 0;
+    const buffer = [];
+
+    const flushBuffer = async () => {
+      var _this$config8;
+
+      await this.req({
+        auth: true,
+        path: '/v2/test_runs',
+        query: {
+          buildId: (_this$config8 = this.config) === null || _this$config8 === void 0 ? void 0 : _this$config8.buildId,
+          groupId: groupResp.groupId,
+          groupType: group.type
+        },
+        bodyDesc: `[${group.name}/${group.type}] Chunk of ${bufferBytes} bytes`,
+        body: buffer.join('\n')
+      });
+      buffer.length = 0;
+      bufferBytes = 0;
+    }; // send test runs in chunks of ~500kb
+
+
+    for (const testRun of testRuns) {
+      const json = JSON.stringify(testRun);
+      bufferBytes += json.length;
+      buffer.push(json);
+
+      if (bufferBytes >= 450000) {
+        await flushBuffer();
+      }
+    }
+
+    if (bufferBytes) {
+      await flushBuffer();
+    }
   }
   /**
    * In order to allow this code to run before @kbn/utils is built, @kbn/pm will pass