diff --git a/genkit-tools/cli/README.md b/genkit-tools/cli/README.md
index 6d7c7a3e0a..aa7b2bcb27 100644
--- a/genkit-tools/cli/README.md
+++ b/genkit-tools/cli/README.md
@@ -44,6 +44,8 @@ Available commands:
 
   evaluate a flow against configured evaluators using provided data as input
 
+**Parallelism tip:** for both `eval:run` (when your dataset already includes outputs) and `eval:flow`, setting `--batchSize` greater than 1 runs inference and evaluator actions in parallel (capped at 100). Higher values can speed up runs but may hit model/API rate limits or increase resource usage—tune according to your environment.
+
 - `config`
 
   set development environment configuration
diff --git a/genkit-tools/cli/src/commands/eval-flow.ts b/genkit-tools/cli/src/commands/eval-flow.ts
index 53c7eacff8..8eb27d15bf 100644
--- a/genkit-tools/cli/src/commands/eval-flow.ts
+++ b/genkit-tools/cli/src/commands/eval-flow.ts
@@ -154,6 +154,7 @@ export const evalFlow = new Command('eval:flow')
           actionRef,
           inferenceDataset,
           context: options.context,
+          batchSize: options.batchSize,
         });
 
         const evalRun = await runEvaluation({
diff --git a/genkit-tools/common/src/eval/evaluate.ts b/genkit-tools/common/src/eval/evaluate.ts
index 596f33cfc9..bfd506b8ed 100644
--- a/genkit-tools/common/src/eval/evaluate.ts
+++ b/genkit-tools/common/src/eval/evaluate.ts
@@ -67,6 +67,7 @@ interface FullInferenceSample {
 const SUPPORTED_ACTION_TYPES = ['flow', 'model', 'executable-prompt'] as const;
 type SupportedActionType = (typeof SUPPORTED_ACTION_TYPES)[number];
 const GENERATE_ACTION_UTIL = '/util/generate';
+const MAX_CONCURRENCY = 100;
 
 /**
  * Starts a new evaluation run. Intended to be used via the reflection API.
@@ -119,6 +120,7 @@ export async function runNewEvaluation(
     inferenceDataset,
     context: request.options?.context,
     actionConfig: request.options?.actionConfig,
+    batchSize: request.options?.batchSize,
   });
   const evaluatorActions = await getMatchingEvaluatorActions(
     manager,
@@ -146,11 +148,20 @@ export async function runInference(params: {
   inferenceDataset: Dataset;
   context?: string;
   actionConfig?: any;
+  batchSize?: number;
 }): Promise<EvalInput[]> {
-  const { manager, actionRef, inferenceDataset, context, actionConfig } =
-    params;
+  const {
+    manager,
+    actionRef,
+    inferenceDataset,
+    context,
+    actionConfig,
+    batchSize,
+  } = params;
   if (!isSupportedActionRef(actionRef)) {
-    throw new Error('Inference is only supported on flows and models');
+    throw new Error(
+      'Inference is only supported on flows, models, and executable prompts'
+    );
   }
 
   const evalDataset: EvalInput[] = await bulkRunAction({
@@ -159,6 +170,7 @@ export async function runInference(params: {
     inferenceDataset,
     context,
     actionConfig,
+    batchSize,
   });
   return evalDataset;
 }
@@ -183,21 +195,23 @@ export async function runEvaluation(params: {
   const runtime = manager.getMostRecentRuntime();
   const isNodeRuntime = runtime?.genkitVersion?.startsWith('nodejs') ?? false;
 
-  for (const action of evaluatorActions) {
-    const name = evaluatorName(action);
-    const response = await manager.runAction({
-      key: name,
-      input: {
-        dataset: evalDataset.filter((row) => !row.error),
-        evalRunId,
-        batchSize: isNodeRuntime ? batchSize : undefined,
-      },
-    });
-    scores[name] = response.result;
-    logger.info(
-      `Finished evaluator '${action.name}'. Trace ID: ${response.telemetry?.traceId}`
-    );
-  }
+  await Promise.all(
+    evaluatorActions.map(async (action) => {
+      const name = evaluatorName(action);
+      const response = await manager.runAction({
+        key: name,
+        input: {
+          dataset: evalDataset.filter((row) => !row.error),
+          evalRunId,
+          batchSize: isNodeRuntime ? batchSize : undefined,
+        },
+      });
+      scores[name] = response.result;
+      logger.info(
+        `Finished evaluator '${action.name}'. Trace ID: ${response.telemetry?.traceId}`
+      );
+    })
+  );
 
   const scoredResults = enrichResultsWithScoring(scores, evalDataset);
   const metadata = extractMetricsMetadata(evaluatorActions);
@@ -258,55 +272,87 @@ async function bulkRunAction(params: {
   inferenceDataset: Dataset;
   context?: string;
   actionConfig?: any;
+  batchSize?: number;
 }): Promise<EvalInput[]> {
-  const { manager, actionRef, inferenceDataset, context, actionConfig } =
-    params;
+  const {
+    manager,
+    actionRef,
+    inferenceDataset,
+    context,
+    actionConfig,
+    batchSize,
+  } = params;
   const actionType = getSupportedActionType(actionRef);
   if (inferenceDataset.length === 0) {
     throw new Error('Cannot run inference, no data provided');
   }
 
+  const desiredConcurrency = Math.max(1, batchSize ?? 1);
+  const resolvedConcurrency = Math.min(desiredConcurrency, MAX_CONCURRENCY);
+
   // Convert to satisfy TS checks. `input` is required in `Dataset` type, but
   // ZodAny also includes `undefined` in TS checks. This explcit conversion
   // works around this.
   const fullInferenceDataset = inferenceDataset as FullInferenceSample[];
 
-  const states: InferenceRunState[] = [];
+  const total = fullInferenceDataset.length;
+  logger.info(
+    `Running inference '${actionRef}' on ${total} samples with concurrency=${resolvedConcurrency}...`
+  );
+  let completed = 0;
+
+  const states: InferenceRunState[] = new Array(total);
   const evalInputs: EvalInput[] = [];
-  for (const sample of fullInferenceDataset) {
-    logger.info(`Running inference '${actionRef}' ...`);
-    if (actionType === 'model') {
-      states.push(
-        await runModelAction({
+  const runSample = async (sample: FullInferenceSample, index: number) => {
+    try {
+      logger.info(`Running inference '${actionRef}' ...`);
+      if (actionType === 'model') {
+        states[index] = await runModelAction({
           manager,
           actionRef,
           sample,
           modelConfig: actionConfig,
-        })
-      );
-    } else if (actionType === 'flow') {
-      states.push(
-        await runFlowAction({
+        });
+      } else if (actionType === 'flow') {
+        states[index] = await runFlowAction({
           manager,
           actionRef,
           sample,
           context,
-        })
-      );
-    } else {
-      // executable-prompt action
-      states.push(
-        await runPromptAction({
+        });
+      } else {
+        // executable-prompt action
+        states[index] = await runPromptAction({
           manager,
           actionRef,
           sample,
           context,
           promptConfig: actionConfig,
-        })
-      );
+        });
+      }
+      completed++;
+      if (completed % 10 === 0 || completed === total) {
+        logger.info(`Inference progress: ${completed}/${total} completed`);
+      }
+    } catch (error: any) {
+      completed++;
+      logger.error(`Inference failed for sample ${index}:`, error);
+      states[index] = {
+        testCaseId: sample.testCaseId,
+        input: sample.input,
+        reference: sample.reference,
+        traceIds: [],
+        evalError: error instanceof Error ? error.message : String(error),
+      };
     }
-  }
+  };
 
+  for (let i = 0; i < total; i += resolvedConcurrency) {
+    const batch = fullInferenceDataset.slice(i, i + resolvedConcurrency);
+    await Promise.all(
+      batch.map((sample, offset) => runSample(sample, i + offset))
+    );
+  }
   logger.info(`Gathering evalInputs...`);
   for (const state of states) {
     evalInputs.push(await gatherEvalInput({ manager, actionRef, state }));
diff --git a/genkit-tools/common/tests/eval/evaluate_test.ts b/genkit-tools/common/tests/eval/evaluate_test.ts
new file mode 100644
index 0000000000..2c6295e43d
--- /dev/null
+++ b/genkit-tools/common/tests/eval/evaluate_test.ts
@@ -0,0 +1,176 @@
+/**
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { describe, expect, it, jest } from '@jest/globals';
+
+// Mock utils used inside evaluate.ts to avoid touching real traces/config.
+jest.mock('../../src/utils', () => {
+  const logger = {
+    info: jest.fn(),
+    warn: jest.fn(),
+    error: jest.fn(),
+  };
+  return {
+    evaluatorName: (action: any) => `/evaluator/${action.name}`,
+    generateTestCaseId: () => 'test-case',
+    getEvalExtractors: jest.fn(async () => ({
+      input: (trace: any) => trace.mockInput,
+      output: (trace: any) => trace.mockOutput,
+      context: () => [],
+    })),
+    getModelInput: (data: any) => data,
+    hasAction: jest.fn().mockResolvedValue(true),
+    isEvaluator: (key: string) => key.startsWith('/evaluator'),
+    logger,
+    stackTraceSpans: jest.fn(() => ({ attributes: {}, spans: [] })),
+  };
+});
+
+import type { Action, EvalInput } from '../../src/types';
+import * as evaluate from '../../src/eval/evaluate';
+
+const bulkRunAction = (evaluate as any)
+  .bulkRunAction as (args: any) => Promise<EvalInput[]>;
+
+function createMockManager() {
+  return {
+    runAction: jest.fn(),
+    getTrace: jest.fn(),
+    getMostRecentRuntime: jest.fn(() => ({ genkitVersion: 'nodejs-1.0' })),
+  };
+}
+
+function createAction(name: string): Action {
+  return {
+    key: `/evaluator/${name}`,
+    name,
+    description: '',
+    inputSchema: null,
+    outputSchema: null,
+    metadata: null,
+  };
+}
+
+describe('bulkRunAction', () => {
+  it('runs samples in batches respecting batchSize', async () => {
+    const manager = createMockManager();
+    const delayMs = 40;
+    manager.runAction.mockImplementation(async (_req: any) => {
+      await new Promise((resolve) => setTimeout(resolve, delayMs));
+      return {
+        result: 'ok',
+        telemetry: { traceId: 'trace' },
+      };
+    });
+    manager.getTrace.mockResolvedValue({
+      spans: {},
+      mockInput: 'input',
+      mockOutput: 'output',
+    });
+
+    const dataset = Array.from({ length: 4 }, (_, i) => ({
+      testCaseId: `case-${i}`,
+      input: { value: i },
+    }));
+
+    const start = Date.now();
+    const results: EvalInput[] = await bulkRunAction({
+      manager: manager as any,
+      actionRef: '/flow/test',
+      inferenceDataset: dataset as any,
+      batchSize: 2,
+    });
+    const duration = Date.now() - start;
+
+    expect(results).toHaveLength(4);
+    // With batchSize 2, the total time should be roughly two batches of delayMs.
+    expect(duration).toBeLessThan(delayMs * 4); // faster than fully sequential
+    expect(manager.runAction).toHaveBeenCalledTimes(4);
+  });
+
+  it('continues processing after an error', async () => {
+    const manager = createMockManager();
+    manager.runAction
+      .mockImplementationOnce(async () => {
+        throw new Error('boom');
+      })
+      .mockImplementation(async () => ({
+        result: 'ok',
+        telemetry: { traceId: 'trace' },
+      }));
+    manager.getTrace.mockResolvedValue({
+      spans: {},
+      mockInput: 'input',
+      mockOutput: 'output',
+    });
+
+    const dataset = [
+      { testCaseId: 'case-1', input: {} },
+      { testCaseId: 'case-2', input: {} },
+      { testCaseId: 'case-3', input: {} },
+    ];
+
+    const results: EvalInput[] = await bulkRunAction({
+      manager: manager as any,
+      actionRef: '/flow/test',
+      inferenceDataset: dataset as any,
+      batchSize: 2,
+    });
+
+    expect(results).toHaveLength(3);
+    expect(results.some((r) => r.error)).toBe(true);
+    expect(manager.runAction).toHaveBeenCalledTimes(3);
+  });
+});
+
+describe('runEvaluation', () => {
+  it('executes evaluator actions in parallel', async () => {
+    const manager = createMockManager();
+    let started = 0;
+    let release!: () => void;
+    const gate = new Promise<void>((resolve) => {
+      release = resolve;
+    });
+
+    manager.runAction.mockImplementation(async () => {
+      started++;
+      if (started === 2) {
+        release();
+      }
+      await gate;
+      return { result: { ok: true }, telemetry: { traceId: 'trace' } };
+    });
+
+    const actions = [createAction('a'), createAction('b')];
+    const evalDataset: EvalInput[] = [
+      { testCaseId: 't1', input: 'in', output: 'out', traceIds: ['trace'] },
+    ];
+
+    const evalPromise = evaluate.runEvaluation({
+      manager: manager as any,
+      evaluatorActions: actions,
+      evalDataset,
+    });
+
+    // Give both runAction calls a moment to start and block on the gate.
+    await new Promise((resolve) => setTimeout(resolve, 10));
+    expect(manager.runAction).toHaveBeenCalledTimes(2);
+
+    // Unblock both and finish.
+    release();
+    await evalPromise;
+  });
+});