diff --git a/.changeset/next-root-detection.md b/.changeset/next-root-detection.md
new file mode 100644
index 0000000000..e16f8d1d37
--- /dev/null
+++ b/.changeset/next-root-detection.md
@@ -0,0 +1,5 @@
+---
+"@workflow/next": patch
+---
+
+Derive the workflow builder project root from Next.js workspace root configuration.
diff --git a/packages/next/src/index.ts b/packages/next/src/index.ts
index 82ace59902..6b0e885914 100644
--- a/packages/next/src/index.ts
+++ b/packages/next/src/index.ts
@@ -1,4 +1,6 @@
+import { statSync } from 'node:fs';
 import { readFile } from 'node:fs/promises';
+import { dirname, isAbsolute, join, resolve } from 'node:path';
 import type { NextConfig } from 'next';
 import semver from 'semver';
 import { getNextBuilder } from './builder.js';
@@ -193,6 +195,82 @@ function resolveNextVersion(workingDir: string): string {
   }
 }
 
+function fileExists(path: string): boolean {
+  try {
+    return statSync(path).isFile();
+  } catch {
+    return false;
+  }
+}
+
+function findRootFile(names: string[], workingDir: string): string | undefined {
+  let current = resolve(workingDir);
+
+  while (true) {
+    for (const name of names) {
+      const file = join(current, name);
+      if (fileExists(file)) {
+        return file;
+      }
+    }
+
+    const parent = dirname(current);
+    if (parent === current) {
+      return undefined;
+    }
+    current = parent;
+  }
+}
+
+function findNextRootFile(workingDir: string): string | undefined {
+  return (
+    findRootFile(['pnpm-workspace.yaml'], workingDir) ??
+    findRootFile(
+      [
+        'pnpm-lock.yaml',
+        'package-lock.json',
+        'yarn.lock',
+        'bun.lock',
+        'bun.lockb',
+      ],
+      workingDir
+    )
+  );
+}
+
+function resolveNextProjectRoot(
+  nextConfig: NextConfig,
+  workingDir: string
+): string {
+  const configuredRoot =
+    nextConfig.outputFileTracingRoot ?? nextConfig.turbopack?.root;
+
+  if (configuredRoot) {
+    return isAbsolute(configuredRoot)
+      ? configuredRoot
+      : resolve(workingDir, configuredRoot);
+  }
+
+  let rootFile = findNextRootFile(workingDir);
+  if (!rootFile) {
+    return workingDir;
+  }
+
+  while (true) {
+    const currentDir = dirname(rootFile);
+    const parentDir = dirname(currentDir);
+    if (parentDir === currentDir) {
+      return currentDir;
+    }
+
+    const parentRootFile = findNextRootFile(parentDir);
+    if (!parentRootFile) {
+      return currentDir;
+    }
+    rootFile = parentRootFile;
+  }
+}
+
 export function withWorkflow(
   nextConfigOrFn:
     | NextConfig
@@ -288,7 +366,9 @@ export function withWorkflow(
       nextConfig.turbopack.rules = {};
     }
     const existingRules = nextConfig.turbopack.rules as any;
-    const nextVersion = resolveNextVersion(process.cwd());
+    const workingDir = process.cwd();
+    const nextVersion = resolveNextVersion(workingDir);
+    const projectRoot = resolveNextProjectRoot(nextConfig, workingDir);
     const supportsTurboCondition = semver.gte(nextVersion, 'v16.0.0');
 
     const shouldWatch = process.env.NODE_ENV === 'development';
@@ -308,9 +388,9 @@ export function withWorkflow(
               'jsx',
               'js',
             ],
-            projectRoot: nextConfig.outputFileTracingRoot,
-            moduleSpecifierRoot: process.cwd(),
-            workingDir: process.cwd(),
+            projectRoot,
+            moduleSpecifierRoot: workingDir,
+            workingDir,
             distDir: nextConfig.distDir || '.next',
             buildTarget: 'next',
             workflowsBundlePath: '', // not used in base