diff --git a/.changeset/fix-local-process-wait.md b/.changeset/fix-local-process-wait.md
new file mode 100644
index 0000000000..4c2bfec80c
--- /dev/null
+++ b/.changeset/fix-local-process-wait.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/ai-sandbox-local-process': patch
+---
+
+Fix local-process spawn handles hanging when the child exits before `wait()` is called.
diff --git a/packages/ai-sandbox-local-process/src/handle.ts b/packages/ai-sandbox-local-process/src/handle.ts
index 10a012c427..6c5b49d81d 100644
--- a/packages/ai-sandbox-local-process/src/handle.ts
+++ b/packages/ai-sandbox-local-process/src/handle.ts
@@ -875,6 +875,13 @@ export class LocalProcessHandle implements SandboxHandle {
         },
       )
     }
+    const closed = new Promise<number>((resolve, reject) => {
+      child.once('error', reject)
+      child.once('close', (code) => resolve(code ?? 0))
+    })
+    // The child can close while stdout is still being drained. Keep the
+    // rejection handled until the caller asks for the result via wait().
+    closed.catch(() => {})
     const handle: SpawnHandle = {
       pid: child.pid ?? -1,
       stdout: decodeStream(child.stdout),
@@ -889,11 +896,7 @@ export class LocalProcessHandle implements SandboxHandle {
             child.stdin.end(() => resolve())
           }),
       },
-      wait: () =>
-        new Promise<number>((resolve, reject) => {
-          child.on('error', reject)
-          child.on('close', (code) => resolve(code ?? 0))
-        }),
+      wait: () => closed,
       kill: (signal) => {
         killTree(child, signal, this.options.logger)
         return Promise.resolve()
diff --git a/packages/ai-sandbox-local-process/tests/local-process.test.ts b/packages/ai-sandbox-local-process/tests/local-process.test.ts
index cf46230cd6..cdec1262c3 100644
--- a/packages/ai-sandbox-local-process/tests/local-process.test.ts
+++ b/packages/ai-sandbox-local-process/tests/local-process.test.ts
@@ -89,6 +89,30 @@ describe('local-process process', () => {
     await sbx.destroy()
   })
 
+  it('resolves wait() when the child closes before stdout is fully consumed', async () => {
+    const sbx = await fresh()
+    // Write digits as strings. `console.log(number)` colorizes under FORCE_COLOR
+    // (CI sets that), so the assertion would see `\u001b[33m0\u001b[39m`.
+    await sbx.fs.write(
+      '/workspace/count.mjs',
+      `for (let i = 0; i < 20; i++) process.stdout.write(String(i) + '\\n')`,
+    )
+    const proc = await sbx.process.spawn('node count.mjs', {
+      cwd: '/workspace',
+    })
+    let out = ''
+    for await (const chunk of proc.stdout) {
+      out += chunk
+      await new Promise((resolve) => setTimeout(resolve, 10))
+    }
+    await expect(proc.wait()).resolves.toBe(0)
+    const lines = out.trimEnd().split(/\r?\n/)
+    expect(lines).toEqual(
+      Array.from({ length: 20 }, (_, index) => String(index)),
+    )
+    await sbx.destroy()
+  })
+
   it('advertises killableProcesses (killTree forcibly kills spawned processes)', async () => {
     const sbx = await fresh()
     // NOTE: this only reads a module constant. What makes the constant TRUE is