code · pull · Sep 18, 2026 · Sep 18, 2026
diff --git a/packages/next/src/server/app-render/app-render.tsx b/packages/next/src/server/app-render/app-render.tsx
@@ -5280,7 +5280,13 @@ async function resolveLazyDevValidationInputs(
   }
 
   if ('syncInterruptReason' in inputs) {
-    await logMessagesAndSendErrorsToBrowser([inputs.syncInterruptReason], ctx)
+    await logMessagesAndSendErrorsToBrowser(
+      [inputs.syncInterruptReason],
+      ctx,
+      // We're not going to run validation, so mark this as the validation result for tests.
+      { logAsValidationResult: true }
+    )
+
     return VALIDATION_BAILOUT
   }
   return inputs
@@ -5291,7 +5297,12 @@ function forwardErrorsFromWarmRender(
   ctx: AppRenderContext
 ) {
   if ('syncInterruptReason' in inputs) {
-    void logMessagesAndSendErrorsToBrowser([inputs.syncInterruptReason], ctx)
+    void logMessagesAndSendErrorsToBrowser(
+      [inputs.syncInterruptReason],
+      ctx,
+      // We're not going to run validation, so mark this as the validation result for tests.
+      { logAsValidationResult: true }
+    )
     return true
   }
 
@@ -6397,11 +6408,24 @@ function createAsyncApiPromises(
  */
 async function logMessagesAndSendErrorsToBrowser(
   messages: unknown[],
-  ctx: AppRenderContext
+  ctx: AppRenderContext,
+  options: { logAsValidationResult?: boolean } = {}
 ): Promise<void> {
-  const { htmlRequestId, renderOpts } = ctx
+  const logAsValidationResult =
+    process.env.__NEXT_TEST_MODE &&
+    process.env.NEXT_TEST_LOG_VALIDATION &&
+    options.logAsValidationResult
+
+  const { htmlRequestId, requestId, renderOpts } = ctx
+  const url = ctx.url.href
   const { sendErrorsToBrowser } = renderOpts
 
+  if (logAsValidationResult) {
+    console.log(
+      formatValidationEvent({ type: 'validation_start', requestId, url })
+    )
+  }
+
   const errors: Error[] = []
   for (const message of messages) {
     // Log the error to the CLI. Prevent the logs from being dimmed, which we
@@ -6421,6 +6445,12 @@ async function logMessagesAndSendErrorsToBrowser(
     }
   }
 
+  if (logAsValidationResult) {
+    console.log(
+      formatValidationEvent({ type: 'validation_end', requestId, url })
+    )
+  }
+
   if (errors.length > 0) {
     if (!sendErrorsToBrowser) {
       throw new InvariantError(

diff --git a/test/e2e/app-dir/instant-validation-build/instant-validation-build.test.ts b/test/e2e/app-dir/instant-validation-build/instant-validation-build.test.ts
@@ -42,7 +42,14 @@ describe('instant-validation-build', () => {
   }
 
   beforeAll(async () => {
-    await next.build({ args: ['--experimental-build-mode', 'compile'] })
+    const result = await next.build({
+      args: ['--experimental-build-mode', 'compile'],
+    })
+    if (result.exitCode !== 0) {
+      throw new Error(
+        `Build exited with exit code ${result.exitCode}. CLI Output:\n\n${result.cliOutput}`
+      )
+    }
   })
 
   describe('basic dynamic hole detection', () => {

diff --git a/test/e2e/app-dir/instant-validation-causes/instant-validation-causes.test.ts b/test/e2e/app-dir/instant-validation-causes/instant-validation-causes.test.ts
@@ -1,6 +1,5 @@
 import { nextTestSetup } from 'e2e-utils'
-import { retry } from 'next-test-utils'
-import type { ValidationEvent } from 'next/dist/server/app-render/dev-validation-events'
+import { createGetInstantInsight } from 'e2e-utils/instant-validation'
 
 describe('instant validation causes', () => {
   const { next, skipped, isNextDev } = nextTestSetup({
@@ -28,67 +27,11 @@ describe('instant validation causes', () => {
     return next.cliOutput.slice(currentCliOutputIndex)
   }
 
-  function parseValidationMessages(output: string): ValidationEvent[] {
-    const messageRe = /<VALIDATION_MESSAGE>(.*?)<\/VALIDATION_MESSAGE>/g
-    const events: ValidationEvent[] = []
-    let match: RegExpExecArray | null
-    while ((match = messageRe.exec(output)) !== null) {
-      try {
-        events.push(JSON.parse(match[1]))
-      } catch (err) {
-        throw new Error(`Failed to parse message '${match[1]}'`, {
-          cause: err,
-        })
-      }
-    }
-    return events
-  }
-
-  function normalizeValidationUrl(url: string): string {
-    const parsed = new URL(url, 'http://n')
-    parsed.searchParams.delete('_rsc')
-    return parsed.pathname + parsed.search + parsed.hash
-  }
-
-  async function waitForValidation(targetUrl: string) {
-    const parsedTargetUrl = new URL(targetUrl)
-    const relativeTargetUrl =
-      parsedTargetUrl.pathname + parsedTargetUrl.search + parsedTargetUrl.hash
-
-    const requestId = await retry(
-      async () => {
-        const events = parseValidationMessages(getCliOutputSinceMark())
-        const start = events.find(
-          (e) =>
-            e.type === 'validation_start' &&
-            normalizeValidationUrl(e.url) === relativeTargetUrl
-        )
-        expect(start).toBeDefined()
-        return start!.requestId
-      },
-      undefined,
-      undefined,
-      `wait for validation of '${relativeTargetUrl}' to start`
-    )
-
-    await retry(
-      async () => {
-        const events = parseValidationMessages(getCliOutputSinceMark())
-        const end = events.find(
-          (e) => e.type === 'validation_end' && e.requestId === requestId
-        )
-        expect(end).toBeDefined()
-      },
-      undefined,
-      undefined,
-      'wait for validation to end'
-    )
-  }
+  const getInstantInsight = createGetInstantInsight(getCliOutputSinceMark, next)
 
   it('named export - export { instant }', async () => {
     const browser = await next.browser('/named-export')
-    await waitForValidation(await browser.url())
-    await expect(browser).toDisplayCollapsedRedbox(`
+    expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
      {
        "cause": [
          {
@@ -117,8 +60,7 @@ describe('instant validation causes', () => {
 
   it('aliased export - export { instantConfig as instant }', async () => {
     const browser = await next.browser('/aliased-export')
-    await waitForValidation(await browser.url())
-    await expect(browser).toDisplayCollapsedRedbox(`
+    expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
      {
        "cause": [
          {
@@ -147,8 +89,7 @@ describe('instant validation causes', () => {
 
   it('re-export - export { instant } from "./config"', async () => {
     const browser = await next.browser('/reexport')
-    await waitForValidation(await browser.url())
-    await expect(browser).toDisplayCollapsedRedbox(`
+    expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
      {
        "cause": [
          {
@@ -177,11 +118,10 @@ describe('instant validation causes', () => {
 
   it('indirect export - const instantConfig = _instant; export { instantConfig as instant }', async () => {
     const browser = await next.browser('/indirect-export')
-    await waitForValidation(await browser.url())
     // Ideally we'd be pointing at the original value declaration.
     // We're not following declarations recursively mostly to keep the implementation simpler
     // presuming that almost all configs are just `export const instant = ...`
-    await expect(browser).toDisplayCollapsedRedbox(`
+    expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
      {
        "cause": [
          {

diff --git a/test/e2e/app-dir/instant-validation-level-default/instant-validation-level-default.test.ts b/test/e2e/app-dir/instant-validation-level-default/instant-validation-level-default.test.ts
@@ -1,5 +1,8 @@
 import { nextTestSetup } from 'e2e-utils'
-import { expectBuildValidationSkipped } from 'e2e-utils/instant-validation'
+import {
+  createGetInstantInsight,
+  expectBuildValidationSkipped,
+} from 'e2e-utils/instant-validation'
 import { waitForNoErrorToast } from '../../../lib/next-test-utils'
 
 // This fixture intentionally omits `experimental.instantInsights` from
@@ -27,9 +30,30 @@ describe('instant validation - default level', () => {
     return
   }
 
+  let currentCliOutputIndex = 0
+  beforeEach(() => {
+    currentCliOutputIndex = next.cliOutput.length
+  })
+
+  function getCliOutputSinceMark(): string {
+    if (next.cliOutput.length < currentCliOutputIndex) {
+      currentCliOutputIndex = 0
+    }
+    return next.cliOutput.slice(currentCliOutputIndex)
+  }
+
+  const getInstantInsight = createGetInstantInsight(getCliOutputSinceMark, next)
+
   if (isNextStart) {
     beforeAll(async () => {
-      await next.build({ args: ['--experimental-build-mode', 'compile'] })
+      const result = await next.build({
+        args: ['--experimental-build-mode', 'compile'],
+      })
+      if (result.exitCode !== 0) {
+        throw new Error(
+          `Build exited with exit code ${result.exitCode}. CLI Output:\n\n${result.cliOutput}`
+        )
+      }
     })
     afterEach(async () => {
       await next.stop()
@@ -55,7 +79,7 @@ describe('instant validation - default level', () => {
     describe('dev', () => {
       it('bare page: framework default matches `warning`, implicit validation fires', async () => {
         const browser = await next.browser('/bare')
-        await expect(browser).toDisplayCollapsedRedbox(`
+        expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
          {
            "description": "Next.js encountered uncached data during a navigation.",
            "environmentLabel": "Server",

diff --git a/test/e2e/app-dir/instant-validation-level-error/instant-validation-level-error.test.ts b/test/e2e/app-dir/instant-validation-level-error/instant-validation-level-error.test.ts
@@ -1,5 +1,6 @@
 import { nextTestSetup } from 'e2e-utils'
 import {
+  createGetInstantInsight,
   expectBuildValidationSkipped,
   extractBuildValidationError,
 } from 'e2e-utils/instant-validation'
@@ -21,9 +22,30 @@ describe('instant validation - level error', () => {
     return
   }
 
+  let currentCliOutputIndex = 0
+  beforeEach(() => {
+    currentCliOutputIndex = next.cliOutput.length
+  })
+
+  function getCliOutputSinceMark(): string {
+    if (next.cliOutput.length < currentCliOutputIndex) {
+      currentCliOutputIndex = 0
+    }
+    return next.cliOutput.slice(currentCliOutputIndex)
+  }
+
+  const getInstantInsight = createGetInstantInsight(getCliOutputSinceMark, next)
+
   if (isNextStart) {
     beforeAll(async () => {
-      await next.build({ args: ['--experimental-build-mode', 'compile'] })
+      const result = await next.build({
+        args: ['--experimental-build-mode', 'compile'],
+      })
+      if (result.exitCode !== 0) {
+        throw new Error(
+          `Build exited with exit code ${result.exitCode}. CLI Output:\n\n${result.cliOutput}`
+        )
+      }
     })
     afterEach(async () => {
       await next.stop()
@@ -58,7 +80,7 @@ describe('instant validation - level error', () => {
     describe('dev', () => {
       it('bare page: implicit validation surfaces a redbox (error level fires)', async () => {
         const browser = await next.browser('/bare')
-        await expect(browser).toDisplayCollapsedRedbox(`
+        expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
          {
            "description": "Next.js encountered uncached data during a navigation.",
            "environmentLabel": "Server",
@@ -75,7 +97,7 @@ describe('instant validation - level error', () => {
 
       it('explicit-error page: explicit override at the configured level, instant redbox in dev', async () => {
         const browser = await next.browser('/explicit-error')
-        await expect(browser).toDisplayCollapsedRedbox(`
+        expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
          {
            "cause": [
              {
@@ -104,7 +126,7 @@ describe('instant validation - level error', () => {
 
       it('explicit-true page: aliases to error level, instant redbox in dev', async () => {
         const browser = await next.browser('/explicit-true')
-        await expect(browser).toDisplayCollapsedRedbox(`
+        expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
          {
            "cause": [
              {
@@ -133,7 +155,7 @@ describe('instant validation - level error', () => {
 
       it('explicit-warning page: per-segment de-escalation still validates in dev', async () => {
         const browser = await next.browser('/explicit-warning')
-        await expect(browser).toDisplayCollapsedRedbox(`
+        expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
          {
            "cause": [
              {
@@ -171,7 +193,7 @@ describe('instant validation - level error', () => {
         // that's per-segment — it doesn't shield descendants. The bare
         // page should still surface an instant redbox in dev.
         const browser = await next.browser('/layered')
-        await expect(browser).toDisplayCollapsedRedbox(`
+        expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
          {
            "description": "Next.js encountered uncached data during a navigation.",
            "environmentLabel": "Server",

diff --git a/...p-dir/instant-validation-level-manual-error/instant-validation-level-manual-error.test.ts b/...p-dir/instant-validation-level-manual-error/instant-validation-level-manual-error.test.ts
@@ -1,5 +1,6 @@
 import { nextTestSetup } from 'e2e-utils'
 import {
+  createGetInstantInsight,
   expectBuildValidationSkipped,
   extractBuildValidationError,
 } from 'e2e-utils/instant-validation'
@@ -21,9 +22,30 @@ describe('instant validation - level manual-error', () => {
     return
   }
 
+  let currentCliOutputIndex = 0
+  beforeEach(() => {
+    currentCliOutputIndex = next.cliOutput.length
+  })
+
+  function getCliOutputSinceMark(): string {
+    if (next.cliOutput.length < currentCliOutputIndex) {
+      currentCliOutputIndex = 0
+    }
+    return next.cliOutput.slice(currentCliOutputIndex)
+  }
+
+  const getInstantInsight = createGetInstantInsight(getCliOutputSinceMark, next)
+
   if (isNextStart) {
     beforeAll(async () => {
-      await next.build({ args: ['--experimental-build-mode', 'compile'] })
+      const result = await next.build({
+        args: ['--experimental-build-mode', 'compile'],
+      })
+      if (result.exitCode !== 0) {
+        throw new Error(
+          `Build exited with exit code ${result.exitCode}. CLI Output:\n\n${result.cliOutput}`
+        )
+      }
     })
     afterEach(async () => {
       await next.stop()
@@ -65,7 +87,7 @@ describe('instant validation - level manual-error', () => {
 
       it('explicit-error page: explicit override at the configured level, instant redbox in dev', async () => {
         const browser = await next.browser('/explicit-error')
-        await expect(browser).toDisplayCollapsedRedbox(`
+        expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
          {
            "cause": [
              {
@@ -94,7 +116,7 @@ describe('instant validation - level manual-error', () => {
 
       it('explicit-true page: aliases to error level, instant redbox in dev', async () => {
         const browser = await next.browser('/explicit-true')
-        await expect(browser).toDisplayCollapsedRedbox(`
+        expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
          {
            "cause": [
              {
@@ -123,7 +145,7 @@ describe('instant validation - level manual-error', () => {
 
       it('explicit-warning page: per-segment de-escalation still validates in dev', async () => {
         const browser = await next.browser('/explicit-warning')
-        await expect(browser).toDisplayCollapsedRedbox(`
+        expect(await getInstantInsight(browser)).toMatchInlineSnapshot(`
          {
            "cause": [
              {