Surface subagent posix dispose failures

Author: TheGreatAxios

src/subagent/dispose.ts

@@ -120,9 +120,5 @@ export async function disposeSubAgentSession(input: SubAgentSessionDisposeInput)
   } catch {
     // ignore
   }
-  try {
-    await input.posixTools.dispose();
-  } catch {
-    // LSP shutdown can fail when several sub-agents exit together.
-  }
+  await input.posixTools.dispose();
 }

src/subagent/index.test.ts

@@ -72,6 +72,21 @@ describe("sub-agent teardown", () => {
     expect(disposeCount).toBe(2);
   });
 
+  test("disposeSubAgentSession does not treat a throwing posix dispose as success", async () => {
+    const posixTools = {
+      dispose: async () => {
+        throw new Error("1 shell child process still live after 2000ms reap");
+      },
+    };
+
+    await expect(
+      disposeSubAgentSession({
+        agent: { close: async () => undefined },
+        posixTools,
+      }),
+    ).rejects.toThrow(/still live after 2000ms reap/);
+  });
+
   test("spawn registry tracks in-flight plugin tool calls", async () => {
     const { plugin, snapshot } = createSubAgentSpawnRegistryPlugin();
     expect(plugin.middleware).toBeDefined();

src/subagent/run.ts

@@ -1078,11 +1078,6 @@ async function runSubAgentInner(
         } catch {
           // close is idempotent; ignore races with disposeSubAgentSession.
         }
-        try {
-          await posixTools.dispose();
-        } catch {
-          // ignore
-        }
       })();
     };
     if (runController.signal.aborted) {