feat(core): add NX_PROJECT_ROOT environment variable to runtime cache inputs (#31428)

Add NX_PROJECT_ROOT environment variable to runtime cache inputs

## Current Behavior

Runtime cache input commands do not have access to project-specific
context, making it impossible to create project-aware runtime inputs.

## Expected Behavior

Runtime cache input commands can access `$NX_PROJECT_ROOT` environment
variable containing the project's root directory path.

## Related Issue(s)

Fixes #20949

Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
Co-authored-by: AgentEnder <AgentEnder@users.noreply.github.com>
Co-authored-by: nx-cloud[bot] <71083854+nx-cloud[bot]@users.noreply.github.com>

packages/nx/src/hasher/native-task-hasher-impl.spec.ts

@@ -761,4 +761,62 @@ describe('native task hasher', () => {
   //   );
   //   console.dir(hashes, { depth: null });
   // });
+
+  it('should provide NX_PROJECT_ROOT environment variable to runtime commands', async () => {
+    const workspaceFiles = await retrieveWorkspaceFiles(tempFs.tempDir, {
+      'libs/parent': 'parent',
+    });
+    const builder = new ProjectGraphBuilder(
+      undefined,
+      workspaceFiles.fileMap.projectFileMap
+    );
+
+    builder.addNode({
+      name: 'parent',
+      type: 'lib',
+      data: {
+        root: 'libs/parent',
+        targets: {
+          build: {
+            executor: 'nx:run-commands',
+            inputs: [
+              // Use a runtime command that outputs the NX_PROJECT_ROOT
+              { runtime: 'echo "NX_PROJECT_ROOT: $NX_PROJECT_ROOT"' },
+            ],
+          },
+        },
+      },
+    });
+
+    const projectGraph = builder.getUpdatedProjectGraph();
+    const taskGraph = createTaskGraph(
+      projectGraph,
+      { build: ['^build'] },
+      ['parent'],
+      ['build'],
+      undefined,
+      {}
+    );
+
+    const hash = await new NativeTaskHasherImpl(
+      tempFs.tempDir,
+      nxJson,
+      projectGraph,
+      workspaceFiles.rustReferences,
+      { selectivelyHashTsConfig: false }
+    ).hashTask(taskGraph.tasks['parent:build'], taskGraph, {});
+
+    // The runtime command should have access to NX_PROJECT_ROOT
+    // and the hash should include that output
+    expect(hash.details).toHaveProperty(
+      'runtime:echo "NX_PROJECT_ROOT: $NX_PROJECT_ROOT"'
+    );
+
+    // Verify the hash is deterministic and non-empty, proving NX_PROJECT_ROOT was available
+    const runtimeHash =
+      hash.details['runtime:echo "NX_PROJECT_ROOT: $NX_PROJECT_ROOT"'];
+    expect(runtimeHash).toBeDefined();
+    expect(runtimeHash).not.toBe('3244421341483603138'); // Should not be empty hash
+    expect(runtimeHash).toBe('17104739612706417536'); // Should be consistent hash for "libs/parent"
+  });
 });

packages/nx/src/native/tasks/hash_planner.rs

@@ -359,7 +359,10 @@ impl HashPlanner {
             )]
         };
         let runtime_and_env_inputs = self_inputs.iter().filter_map(|i| match i {
-            Input::Runtime(runtime) => Some(HashInstruction::Runtime(runtime.to_string())),
+            Input::Runtime(runtime) => Some(HashInstruction::Runtime(
+                project_name.to_string(),
+                runtime.to_string(),
+            )),
             Input::Environment(env) => Some(HashInstruction::Environment(env.to_string())),
             _ => None,
         });

packages/nx/src/native/tasks/task_hasher.rs

@@ -179,11 +179,18 @@ impl TaskHasher {
                 trace!(parent: &span, "hash_workspace_files: {:?}", now.elapsed());
                 hashed_workspace_files?
             }
-            HashInstruction::Runtime(runtime) => {
+            HashInstruction::Runtime(project_name, runtime) => {
+                // Create a modified environment with NX_PROJECT_ROOT
+                let mut env_with_project_root = js_env.clone();
+                if let Some(project) = self.project_graph.nodes.get(project_name) {
+                    env_with_project_root
+                        .insert("NX_PROJECT_ROOT".to_string(), project.root.clone());
+                }
+
                 let hashed_runtime = hash_runtime(
                     &self.workspace_root,
                     runtime,
-                    js_env,
+                    &env_with_project_root,
                     Arc::clone(&self.runtime_cache),
                 )?;
                 trace!(parent: &span, "hash_runtime: {:?}", now.elapsed());

packages/nx/src/native/tasks/types.rs

@@ -47,7 +47,7 @@ pub struct TaskGraph {
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone)]
 pub enum HashInstruction {
     WorkspaceFileSet(Vec<String>),
-    Runtime(String),
+    Runtime(String, String), // (project_name, runtime)
     Environment(String),
     ProjectFileSet(String, Vec<String>),
     ProjectConfiguration(String),
@@ -89,7 +89,8 @@ impl fmt::Display for HashInstruction {
                 }
                 HashInstruction::WorkspaceFileSet(file_set) =>
                     format!("workspace:[{}]", file_set.join(",")),
-                HashInstruction::Runtime(runtime) => format!("runtime:{}", runtime),
+                HashInstruction::Runtime(project_name, runtime) =>
+                    format!("{}:runtime:{}", project_name, runtime),
                 HashInstruction::Environment(env) => format!("env:{}", env),
                 HashInstruction::TaskOutput(task_output, dep_outputs) => {
                     let dep_outputs = dep_outputs.join(",");