fix(bash): use newline separator for sentinel to fix heredoc hangs

When the LLM sends heredoc commands (cat << 'EOF'), the semicolon
sentinel (EOF; echo '<<exit>>') prevents bash from recognizing the
terminator, causing the session to hang until the 120s timeout.
Confirmed in production logs: the exact command that caused the hang.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nanobot/agent/tools/anthropic/bash.py

@@ -71,9 +71,10 @@ class _BashSession:
         assert self._process.stdout
         assert self._process.stderr
 
-        # Send command + sentinel
+        # Send command + sentinel on its own line so heredoc terminators
+        # aren't corrupted (EOF; echo '...' ≠ EOF)
         self._process.stdin.write(
-            command.encode() + f"; echo '{self._sentinel}'\n".encode()
+            command.encode() + f"\necho '{self._sentinel}'\n".encode()
         )
         await self._process.stdin.drain()
 

tests/test_bash_heredoc.py

@@ -0,0 +1,68 @@
+"""Test that bash tool handles heredoc commands correctly.
+
+Reproduces the bug where `; echo '<<exit>>'` appended on the same line
+as a heredoc terminator prevents bash from recognizing the terminator,
+causing the session to hang forever.
+"""
+
+import asyncio
+import pytest
+from nanobot.agent.tools.anthropic.bash import BashTool20250124
+
+
+@pytest.mark.asyncio
+async def test_heredoc_command():
+    """Heredoc commands must complete without hanging."""
+    tool = BashTool20250124()
+
+    # Simple command works
+    result = await tool(command="echo hello")
+    assert result.output == "hello"
+
+    # Heredoc command — this is the exact pattern that caused the hang
+    result = await asyncio.wait_for(
+        tool(command="cat << 'EOF'\nline1\nline2\nEOF"),
+        timeout=5.0,
+    )
+    assert "line1" in result.output
+    assert "line2" in result.output
+
+
+@pytest.mark.asyncio
+async def test_heredoc_append_to_file():
+    """Heredoc append (the exact pattern the LLM uses) must work."""
+    tool = BashTool20250124()
+
+    result = await asyncio.wait_for(
+        tool(command="cat >> /tmp/test_heredoc_bash.txt << 'EOF'\nhello world\nEOF"),
+        timeout=5.0,
+    )
+    # Should complete without error
+    assert result.error is None or result.error == ""
+
+    # Verify the file was written
+    result2 = await tool(command="cat /tmp/test_heredoc_bash.txt")
+    assert "hello world" in result2.output
+
+    # Cleanup
+    await tool(command="rm -f /tmp/test_heredoc_bash.txt")
+
+
+@pytest.mark.asyncio
+async def test_regular_commands_still_work():
+    """Ensure regular commands still work after the fix."""
+    tool = BashTool20250124()
+
+    # Semicolons in commands
+    result = await tool(command="echo a; echo b")
+    assert "a" in result.output
+    assert "b" in result.output
+
+    # Multiline script
+    result = await tool(command="for i in 1 2 3; do echo $i; done")
+    assert "1" in result.output
+    assert "3" in result.output
+
+    # Command with exit code
+    result = await tool(command="true")
+    assert result.output == "(no output)" or result.output is not None

tests/test_bash_tool.py

@@ -40,7 +40,7 @@ async def test_bash_tool_restart():
 
     # Restart
     result = await tool(restart=True)
-    assert "restarted" in result.output.lower()
+    assert "restarted" in (result.system or result.output or "").lower()
 
     # Variable should be gone
     result2 = await tool(command="echo $TEST_VAR")