feat: Make Vitest runs more token efficient when run through a coding assistant.

Author: cpojer

docs/config/reporters.md

@@ -42,6 +42,7 @@ Note that the [coverage](/guide/coverage) feature uses a different [`coverage.re
 - [`tap-flat`](/guide/reporters#tap-flat-reporter)
 - [`hanging-process`](/guide/reporters#hanging-process-reporter)
 - [`github-actions`](/guide/reporters#github-actions-reporter)
+- [`agent`](/guide/reporters#agent-reporter)
 - [`blob`](/guide/reporters#blob-reporter)
 
 ## Example

docs/guide/browser/visual-regression-testing.md

@@ -606,7 +606,6 @@ screenshots should use the service.
 
 The cleanest approach is using [Test Projects](/guide/projects):
 
-
 ```ts [vitest.config.ts]
 import { env } from 'node:process'
 import { defineConfig } from 'vitest/config'
@@ -663,7 +662,6 @@ export default defineConfig({
 })
 ```
 
-
 Follow the [official guide to create a Playwright Workspace](https://learn.microsoft.com/en-us/azure/app-testing/playwright-workspaces/quickstart-run-end-to-end-tests?tabs=playwrightcli&pivots=playwright-test-runner#create-a-workspace).
 
 Once your workspace is created, configure Vitest to use it:

docs/guide/cli-generated.md

@@ -102,7 +102,7 @@ Hide logs for skipped tests
 - **CLI:** `--reporter <name>`
 - **Config:** [reporters](/config/reporters)
 
-Specify reporters (default, blob, verbose, dot, json, tap, tap-flat, junit, tree, hanging-process, github-actions)
+Specify reporters (default, agent, blob, verbose, dot, json, tap, tap-flat, junit, tree, hanging-process, github-actions)
 
 ### outputFile
 

docs/guide/cli.md

@@ -237,4 +237,3 @@ Merges every blob report located in the specified folder (`.vitest-reports` by d
 ```sh
 vitest --merge-reports --reporter=junit
 ```
-

docs/guide/reporters.md

@@ -98,6 +98,10 @@ This example will write separate JSON and XML reports as well as printing a verb
 
 By default (i.e. if no reporter is specified), Vitest will display summary of running tests and their status at the bottom. Once a suite passes, its status will be reported on top of the summary.
 
+::: tip
+When Vitest detects it is running inside an AI coding agent, the [`agent`](#agent-reporter) reporter is used instead to reduce output and minimize token usage. You can override this by explicitly configuring the [`reporters`](/config/reporters) option.
+:::
+
 You can disable the summary by configuring the reporter:
 
 :::code-group
@@ -637,6 +641,26 @@ export default defineConfig({
 })
 ```
 
+### Agent Reporter
+
+Outputs a minimal report optimized for AI coding assistants and LLM-based workflows. Only failed tests and their error messages are displayed. Console logs from passing tests and the summary section are suppressed to reduce token usage.
+
+This reporter is automatically enabled when no `reporters` option is configured and Vitest detects it is running inside an AI coding agent. If you configure custom reporters, you can explicitly add `agent`:
+
+:::code-group
+```bash [CLI]
+npx vitest --reporter=agent
+```
+
+```ts [vitest.config.ts]
+export default defineConfig({
+  test: {
+    reporters: ['agent']
+  },
+})
+```
+:::
+
 ### Blob Reporter
 
 Stores test results on the machine so they can be later merged using [`--merge-reports`](/guide/cli#merge-reports) command.

packages/vitest/src/node/config/resolveConfig.ts

@@ -23,7 +23,7 @@ import {
   defaultPort,
 } from '../../constants'
 import { benchmarkConfigDefaults, configDefaults } from '../../defaults'
-import { isCI, stdProvider } from '../../utils/env'
+import { isAgent, isCI, stdProvider } from '../../utils/env'
 import { getWorkersCountByPercentage } from '../../utils/workers'
 import { BaseSequencer } from '../sequencers/BaseSequencer'
 import { RandomSequencer } from '../sequencers/RandomSequencer'
@@ -729,7 +729,7 @@ export function resolveConfig(
   }
 
   if (!resolved.reporters.length) {
-    resolved.reporters.push(['default', {}])
+    resolved.reporters.push([isAgent ? 'agent' : 'default', {}])
 
     // also enable github-actions reporter as a default
     if (process.env.GITHUB_ACTIONS === 'true') {

packages/vitest/src/node/reporters/agent.ts

@@ -0,0 +1,46 @@
+import type { Task } from '@vitest/runner'
+import type { UserConsoleLog } from '../../types/general'
+import type { TestSpecification } from '../test-specification'
+import type { DefaultReporterOptions } from './default'
+import type { TestCase, TestModule, TestModuleState, TestResult } from './reported-tasks'
+import { DefaultReporter } from './default'
+
+export class AgentReporter extends DefaultReporter {
+  renderSucceed = false
+
+  constructor(options: DefaultReporterOptions = {}) {
+    super({ ...options, summary: false })
+  }
+
+  onTestRunStart(specifications: ReadonlyArray<TestSpecification>): void {
+    super.onTestRunStart(specifications)
+    this.renderSucceed = false
+  }
+
+  protected logFailedTask(task: Task): void {
+    for (const log of task.logs || []) {
+      this.onUserConsoleLog(log, 'failed')
+    }
+  }
+
+  protected printTestModule(testModule: TestModule): void {
+    if (testModule.state() !== 'failed') {
+      return
+    }
+    super.printTestModule(testModule)
+  }
+
+  protected printTestCase(moduleState: TestModuleState, test: TestCase): void {
+    const testResult = test.result()
+    if (testResult.state === 'failed') {
+      super.printTestCase(moduleState, test)
+    }
+  }
+
+  shouldLog(log: UserConsoleLog, taskState?: TestResult['state']): boolean {
+    if (taskState !== 'failed') {
+      return false
+    }
+    return super.shouldLog(log, taskState)
+  }
+}

packages/vitest/src/node/reporters/base.ts

@@ -117,7 +117,7 @@ export abstract class BaseReporter implements Reporter {
     this.printTestModule(testModule)
   }
 
-  private logFailedTask(task: Task) {
+  protected logFailedTask(task: Task): void {
     if (this.ctx.config.silent === 'passed-only') {
       for (const log of task.logs || []) {
         this.onUserConsoleLog(log, 'failed')

packages/vitest/src/node/reporters/index.ts

@@ -6,6 +6,7 @@ import type { GithubActionsReporterOptions } from './github-actions'
 import type { HTMLOptions } from './html'
 import type { JsonOptions } from './json'
 import type { JUnitOptions } from './junit'
+import { AgentReporter } from './agent'
 import { BlobReporter } from './blob'
 import { DefaultReporter } from './default'
 import { DotReporter } from './dot'
@@ -19,6 +20,7 @@ import { TreeReporter } from './tree'
 import { VerboseReporter } from './verbose'
 
 export {
+  AgentReporter,
   DefaultReporter,
   DotReporter,
   GithubActionsReporter,
@@ -46,6 +48,7 @@ export type {
 
 export const ReportersMap = {
   'default': DefaultReporter as typeof DefaultReporter,
+  'agent': AgentReporter as typeof AgentReporter,
   'blob': BlobReporter as typeof BlobReporter,
   'verbose': VerboseReporter as typeof VerboseReporter,
   'dot': DotReporter as typeof DotReporter,
@@ -62,6 +65,7 @@ export type BuiltinReporters = keyof typeof ReportersMap
 
 export interface BuiltinReporterOptions {
   'default': DefaultReporterOptions
+  'agent': DefaultReporterOptions
   'verbose': DefaultReporterOptions
   'dot': BaseOptions
   'tree': BaseOptions

packages/vitest/src/public/node.ts

@@ -43,6 +43,7 @@ export { VmThreadsPoolWorker } from '../node/pools/workers/vmThreadsWorker'
 export type { SerializedTestProject, TestProject } from '../node/project'
 
 export {
+  AgentReporter,
   BenchmarkReporter,
   BenchmarkReportsMap,
   DefaultReporter,