fix(codemode): return promises from combinators (#35782)

packages/core/test/tool-execute.test.ts

@@ -0,0 +1,47 @@
+import { expect, test } from "bun:test"
+import { ExecuteTool } from "@opencode-ai/core/tool/execute"
+import { Tool } from "@opencode-ai/core/tool/tool"
+import { Agent } from "@opencode-ai/schema/agent"
+import { Session } from "@opencode-ai/schema/session"
+import { SessionMessage } from "@opencode-ai/schema/session-message"
+import { Effect, Schema } from "effect"
+
+test("execute preserves successful results with visible unhandled rejections", async () => {
+  const child = Tool.make({
+    description: "Always fail",
+    input: Schema.Struct({}),
+    output: Schema.String,
+    execute: () => Effect.fail(new Tool.Failure({ message: "Lookup refused" })),
+  })
+  const execute = ExecuteTool.create(new Map([["fail", { tool: child, name: "fail" }]]))
+  const result = await Effect.runPromise(
+    Tool.settle(
+      execute,
+      {
+        type: "tool-call",
+        id: "call_execute",
+        name: "execute",
+        input: { code: `tools.fail({}); return "done"` },
+      },
+      {
+        sessionID: Session.ID.make("ses_execute"),
+        agent: Agent.ID.make("build"),
+        assistantMessageID: SessionMessage.ID.make("msg_execute"),
+        toolCallID: "call_execute",
+      },
+    ),
+  )
+
+  expect(result.structured).toEqual({ toolCalls: [{ tool: "fail", status: "error" }] })
+  expect(result.content).toEqual([
+    {
+      type: "text",
+      text: [
+        "done",
+        "",
+        "Warnings:",
+        "- [ToolFailure] Unhandled rejection from an un-awaited promise: Lookup refused",
+      ].join("\n"),
+    },
+  ])
+})