fix(backend/copilot): return sandbox path from bridge, inform model of copy location

Address CodeRabbit review: _bridge_to_sandbox now returns the sandbox
path (or None on failure) so callers can append "[Sandbox copy available
at /tmp/file.json]" to the Read result. This gives the model explicit
feedback about where to find the file in the sandbox, instead of
silently bridging with no indication.

autogpt_platform/backend/backend/copilot/sdk/e2b_file_tools.py

@@ -141,7 +141,11 @@ async def _handle_read_file(args: dict[str, Any]) -> dict[str, Any]:
         if not result.get("isError"):
             sandbox = _get_sandbox()
             if sandbox is not None:
-                await _bridge_to_sandbox(sandbox, file_path, offset, limit)
+                bridged = await _bridge_to_sandbox(sandbox, file_path, offset, limit)
+                if bridged:
+                    result["content"][0][
+                        "text"
+                    ] += f"\n[Sandbox copy available at {bridged}]"
         return result
 
     result = _get_sandbox_and_path(file_path)
@@ -321,7 +325,7 @@ _BRIDGE_SKIP_BYTES = 50 * 1024 * 1024  # 50 MB
 
 async def _bridge_to_sandbox(
     sandbox: Any, file_path: str, offset: int, limit: int
-) -> None:
+) -> str | None:
     """Best-effort copy of a host-side SDK file into the E2B sandbox.
 
     When the model reads an SDK-internal file (e.g. tool-results), it often
@@ -331,6 +335,8 @@ async def _bridge_to_sandbox(
     Only copies when offset=0 and limit is large enough to indicate the model
     wants the full file.  Errors are logged but never propagated.
 
+    Returns the sandbox path on success, or ``None`` on skip/failure.
+
     Size handling:
     - <= 5 MB: written to ``/tmp/<basename>`` via shell base64 (``_sandbox_write``).
     - 5-50 MB: written to ``/home/user/<basename>`` via ``sandbox.files.write()``
@@ -338,7 +344,7 @@ async def _bridge_to_sandbox(
     - > 50 MB: skipped entirely with a warning.
     """
     if offset != 0 or limit < 2000:
-        return
+        return None
     basename = os.path.basename(file_path)
     try:
         expanded = os.path.realpath(os.path.expanduser(file_path))
@@ -365,12 +371,14 @@ async def _bridge_to_sandbox(
         logger.info(
             "[E2B] Bridged SDK file to sandbox: %s -> %s", basename, sandbox_path
         )
+        return sandbox_path
     except Exception:
         logger.debug(
             "[E2B] Failed to bridge SDK file to sandbox: %s",
             basename,
             exc_info=True,
         )
+        return None
 
 
 # Local read (for SDK-internal paths)

autogpt_platform/backend/backend/copilot/sdk/e2b_file_tools_test.py

@@ -380,8 +380,9 @@ class TestBridgeToSandbox:
         f.write_text('{"ok": true}')
         sandbox = _make_bridge_sandbox()
 
-        await _bridge_to_sandbox(sandbox, str(f), offset=0, limit=2000)
+        result = await _bridge_to_sandbox(sandbox, str(f), offset=0, limit=2000)
 
+        assert result == "/tmp/result.json"
         sandbox.commands.run.assert_called_once()
         cmd = sandbox.commands.run.call_args[0][0]
         assert "result.json" in cmd
@@ -394,8 +395,9 @@ class TestBridgeToSandbox:
         f.write_text("content")
         sandbox = _make_bridge_sandbox()
 
-        await _bridge_to_sandbox(sandbox, str(f), offset=10, limit=2000)
+        result = await _bridge_to_sandbox(sandbox, str(f), offset=10, limit=2000)
 
+        assert result is None
         sandbox.commands.run.assert_not_called()
         sandbox.files.write.assert_not_called()
 
@@ -424,14 +426,16 @@ class TestBridgeToSandbox:
         sandbox.files.write.assert_not_called()
 
     @pytest.mark.asyncio
-    async def test_sandbox_write_failure_does_not_raise(self, tmp_path):
-        """If sandbox write fails, the error is swallowed (best-effort)."""
+    async def test_sandbox_write_failure_returns_none(self, tmp_path):
+        """If sandbox write fails, returns None (best-effort)."""
         f = tmp_path / "data.txt"
         f.write_text("content")
         sandbox = _make_bridge_sandbox()
         sandbox.commands.run.side_effect = RuntimeError("E2B timeout")
 
-        await _bridge_to_sandbox(sandbox, str(f), offset=0, limit=2000)
+        result = await _bridge_to_sandbox(sandbox, str(f), offset=0, limit=2000)
+
+        assert result is None
 
     @pytest.mark.asyncio
     async def test_large_file_uses_files_api(self, tmp_path):
@@ -440,8 +444,9 @@ class TestBridgeToSandbox:
         f.write_bytes(b"x" * (_BRIDGE_SHELL_MAX_BYTES + 1))
         sandbox = _make_bridge_sandbox()
 
-        await _bridge_to_sandbox(sandbox, str(f), offset=0, limit=2000)
+        result = await _bridge_to_sandbox(sandbox, str(f), offset=0, limit=2000)
 
+        assert result == "/home/user/big.json"
         sandbox.files.write.assert_called_once()
         call_args = sandbox.files.write.call_args[0]
         assert call_args[0] == "/home/user/big.json"
@@ -457,7 +462,9 @@ class TestBridgeToSandbox:
             fh.write(b"\0")
         sandbox = _make_bridge_sandbox()
 
-        await _bridge_to_sandbox(sandbox, str(f), offset=0, limit=2000)
+        result = await _bridge_to_sandbox(sandbox, str(f), offset=0, limit=2000)
+
+        assert result is None
 
         sandbox.commands.run.assert_not_called()
         sandbox.files.write.assert_not_called()

autogpt_platform/backend/backend/copilot/sdk/tool_adapter.py

@@ -390,10 +390,13 @@ async def _read_file_handler(args: dict[str, Any]) -> dict[str, Any]:
         #
         # When E2B is active, also copy the file into the sandbox so
         # bash_exec can process it (the model often uses Read then bash).
+        text = "".join(selected)
         sandbox = _current_sandbox.get(None)
         if sandbox is not None:
-            await _bridge_to_sandbox(sandbox, file_path, offset, limit)
-        return _mcp_ok("".join(selected))
+            bridged = await _bridge_to_sandbox(sandbox, file_path, offset, limit)
+            if bridged:
+                text += f"\n[Sandbox copy available at {bridged}]"
+        return _mcp_ok(text)
     except FileNotFoundError:
         return _mcp_err(f"File not found: {file_path}")
     except Exception as e: