From 84989836f1f46c476eb34ced94da7ed38854e4a4 Mon Sep 17 00:00:00 2001
From: ooiuuii <al3060388206@gmail.com>
Date: Wed, 7 Oct 2026 02:23:11 -0700
Subject: [PATCH] fix(background-terminals): preserve shell-significant command
 whitespace

---
 extensions/background-terminals/index.ts      |   4 +-
 .../background-terminals/index.test.ts        | 117 ++++++++++++++++++
 2 files changed, 119 insertions(+), 2 deletions(-)

diff --git a/extensions/background-terminals/index.ts b/extensions/background-terminals/index.ts
index 7817340a4..9c756d5f1 100644
--- a/extensions/background-terminals/index.ts
+++ b/extensions/background-terminals/index.ts
@@ -382,8 +382,8 @@ export default function (pi: ExtensionAPI) {
     async execute(_toolCallId, params, _signal, _onUpdate, ctx) {
       const manager = await getManager();
 
-      const command = params.command.trim();
-      if (!command) throw new Error("command must not be empty.");
+      const command = params.command;
+      if (!command.trim()) throw new Error("command must not be empty.");
 
       const cwd = path.resolve(ctx.cwd, params.working_dir ?? ".");
       if (!fs.existsSync(cwd) || !fs.statSync(cwd).isDirectory()) {
diff --git a/tests/extensions/background-terminals/index.test.ts b/tests/extensions/background-terminals/index.test.ts
index ce5e77b29..481030df2 100644
--- a/tests/extensions/background-terminals/index.test.ts
+++ b/tests/extensions/background-terminals/index.test.ts
@@ -1,10 +1,12 @@
 import assert from "node:assert/strict";
+import { spawnSync } from "node:child_process";
 import test from "node:test";
 import type {
   ExtensionAPI,
   ExtensionContext,
 } from "@earendil-works/pi-coding-agent";
 import backgroundTerminals from "../../../extensions/background-terminals/index.ts";
+import { webCapabilityDetail } from "../../../extensions/shared/web-observer-registry.ts";
 
 type CapturedTool = {
   name: string;
@@ -132,3 +134,118 @@ test("a successful start exposes lifecycle tools but a rejected start does not",
     }
   }
 });
+
+test("bg_start preserves shell-significant trailing whitespace", {
+  skip: process.platform === "win32",
+  timeout: 20_000,
+}, async () => {
+  const tools = new Map<string, CapturedTool>();
+  const handlers = new Map<
+    string,
+    Array<(event: unknown, ctx: ExtensionContext) => unknown>
+  >();
+  let active: string[] = [];
+  const pi = {
+    on(event: string, handler: unknown) {
+      handlers.set(event, [
+        ...(handlers.get(event) ?? []),
+        handler as (event: unknown, ctx: ExtensionContext) => unknown,
+      ]);
+    },
+    registerTool(tool: CapturedTool) {
+      tools.set(tool.name, tool);
+      active.push(tool.name);
+    },
+    getActiveTools: () => [...active],
+    setActiveTools(names: string[]) {
+      active = [...names];
+    },
+    registerMessageRenderer() {},
+    registerCommand() {},
+    sendMessage() {},
+  } as unknown as ExtensionAPI;
+  const scope = { getSessionId: () => "command-preservation" };
+  const ctx = {
+    cwd: process.cwd(),
+    hasUI: false,
+    isIdle: () => false,
+    sessionManager: scope,
+  } as unknown as ExtensionContext;
+  backgroundTerminals(pi);
+  const emit = async (event: string) => {
+    for (const handler of handlers.get(event) ?? []) await handler({}, ctx);
+  };
+  await emit("session_start");
+  try {
+    const start = tools.get("bg_start"),
+      list = tools.get("bg_list");
+    assert(start && list);
+    const before = await list.execute("before", {}, undefined, undefined, ctx);
+    await assert.rejects(
+      start.execute(
+        "blank",
+        { command: " \t\n ", title: "blank" },
+        undefined,
+        undefined,
+        ctx,
+      ),
+      /command must not be empty/,
+    );
+    assert.deepEqual(
+      await list.execute("after", {}, undefined, undefined, ctx),
+      before,
+    );
+    for (const command of [
+      "printf %s hello",
+      "printf %s hello" + String.fromCharCode(92) + " ",
+    ]) {
+      const control = spawnSync("/bin/sh", ["-c", command], { timeout: 5_000 });
+      assert.ifError(control.error);
+      assert.equal(control.status, 0);
+      assert.equal(
+        control.stdout.toString(),
+        command.endsWith(" ") ? "hello " : "hello",
+      );
+      const result = (await start.execute(
+        "start",
+        { command, title: "command preservation", timeout_seconds: 3 },
+        undefined,
+        undefined,
+        ctx,
+      )) as { details: { id: string } };
+      const deadline = Date.now() + 5_000;
+      let observed = webCapabilityDetail(
+        scope,
+        "background-terminals",
+        result.details.id,
+      );
+      while (
+        observed.status === "found" &&
+        observed.detail.status === "running" &&
+        Date.now() < deadline
+      ) {
+        await new Promise((resolve) => setTimeout(resolve, 10));
+        observed = webCapabilityDetail(
+          scope,
+          "background-terminals",
+          result.details.id,
+        );
+      }
+      assert.equal(observed.status, "found");
+      if (observed.status !== "found")
+        assert.fail("missing registered terminal");
+      const snapshot = observed.detail;
+      assert.equal(snapshot.kind, "background-terminals");
+      if (snapshot.kind !== "background-terminals")
+        assert.fail("wrong capability kind");
+      assert.equal(snapshot.status, "done");
+      assert.equal(snapshot.exitCode, 0);
+      assert.equal(snapshot.stdout.totalBytes, control.stdout.length);
+      assert.deepEqual(Buffer.from(snapshot.stdout.text), control.stdout);
+      assert.equal(snapshot.stderr.text, "");
+      assert.equal(snapshot.command, command);
+    }
+  } finally {
+    await emit("session_shutdown");
+  }
+});