fix(backend/copilot): split broad except in _read_cli_session_from_disk, clean up dataclass field comment

- Split `except Exception` into `UnicodeDecodeError` (returns raw) + nested
  `OSError` on write-back (returns stripped for GCS despite local failure) +
  fallback `Exception` — eliminates path leak via OSError str() and clarifies
  each fallback path's intent
- Move write-back into its own nested try/except so pyright can verify
  `stripped_bytes` is always bound before use
- Simplify `TranscriptDownload.mode` default: use conventional comment on
  separate line instead of parenthesized expression
- Add `TestReadCliSessionFromDisk` tests covering both new exception branches

autogpt_platform/backend/backend/copilot/sdk/service.py

@@ -939,8 +939,18 @@ def _read_cli_session_from_disk(
         raw_text = raw_bytes.decode("utf-8")
         stripped_text = strip_for_upload(raw_text)
         stripped_bytes = stripped_text.encode("utf-8")
-        if len(stripped_bytes) < len(raw_bytes):
-            # Write back locally so same-pod turns also benefit.
+    except UnicodeDecodeError:
+        logger.warning("%s CLI session is not valid UTF-8, uploading raw", log_prefix)
+        return raw_bytes
+    except Exception as e:
+        logger.warning(
+            "%s Failed to strip CLI session, uploading raw: %s", log_prefix, e
+        )
+        return raw_bytes
+
+    if len(stripped_bytes) < len(raw_bytes):
+        # Write back locally so same-pod turns also benefit.
+        try:
             Path(real_path).write_bytes(stripped_bytes)
             logger.info(
                 "%s Stripped CLI session: %dB → %dB",
@@ -948,12 +958,15 @@ def _read_cli_session_from_disk(
                 len(raw_bytes),
                 len(stripped_bytes),
             )
-        return stripped_bytes
-    except Exception as e:
-        logger.warning(
-            "%s Failed to strip CLI session, uploading raw: %s", log_prefix, e
-        )
-        return raw_bytes
+        except OSError as e:
+            # write_bytes failed — stripped content is still valid for GCS upload even
+            # though the local write-back failed (same-pod optimization silently skipped).
+            logger.warning(
+                "%s Failed to write back stripped CLI session: %s",
+                log_prefix,
+                e.strerror or str(e),
+            )
+    return stripped_bytes
 
 
 def _process_cli_restore(

autogpt_platform/backend/backend/copilot/sdk/transcript_test.py

@@ -1451,3 +1451,89 @@ class TestProcessCliRestore:
 
         assert not ok
         assert stripped_str == ""
+
+
+class TestReadCliSessionFromDisk:
+    """``_read_cli_session_from_disk`` reads, strips, and optionally writes back the session."""
+
+    def _build_session_file(self, tmp_path, session_id: str):
+        """Build the session file path inside tmp_path using the same encoding as cli_session_path."""
+        import os
+        import re
+        from pathlib import Path
+
+        sdk_cwd = str(tmp_path)
+        encoded_cwd = re.sub(r"[^a-zA-Z0-9]", "-", os.path.realpath(sdk_cwd))
+        session_dir = Path(str(tmp_path)) / encoded_cwd
+        session_dir.mkdir(parents=True, exist_ok=True)
+        return sdk_cwd, session_dir / f"{session_id}.jsonl"
+
+    def test_returns_raw_bytes_for_invalid_utf8(self, tmp_path):
+        """Non-UTF-8 bytes trigger UnicodeDecodeError — returns raw bytes (upload-raw fallback)."""
+        from unittest.mock import patch
+
+        from backend.copilot.sdk.service import _read_cli_session_from_disk
+
+        session_id = "12345678-0000-0000-0000-aabbccdd0001"
+        projects_base_dir = str(tmp_path)
+        sdk_cwd, session_file = self._build_session_file(tmp_path, session_id)
+
+        # Write raw invalid UTF-8 bytes
+        session_file.write_bytes(b"\xff\xfe invalid utf-8\n")
+
+        with (
+            patch(
+                "backend.copilot.sdk.service.projects_base",
+                return_value=projects_base_dir,
+            ),
+            patch(
+                "backend.copilot.transcript.projects_base",
+                return_value=projects_base_dir,
+            ),
+        ):
+            result = _read_cli_session_from_disk(sdk_cwd, session_id, "[Test]")
+
+        # UnicodeDecodeError path returns the raw bytes (upload-raw fallback)
+        assert result == b"\xff\xfe invalid utf-8\n"
+
+    def test_write_back_oserror_still_returns_stripped_bytes(self, tmp_path):
+        """OSError on write-back returns stripped bytes for GCS upload (not raw)."""
+        from unittest.mock import patch
+
+        from backend.copilot.sdk.service import _read_cli_session_from_disk
+
+        session_id = "12345678-0000-0000-0000-aabbccdd0002"
+        projects_base_dir = str(tmp_path)
+        sdk_cwd, session_file = self._build_session_file(tmp_path, session_id)
+
+        # Content with a strippable progress entry so stripped_bytes < raw_bytes
+        raw_content = (
+            '{"type":"progress","uuid":"p1","subtype":"agent_progress","parentUuid":null}\n'
+            '{"type":"user","uuid":"u1","parentUuid":null,"message":{"role":"user","content":"hi"}}\n'
+            '{"type":"assistant","uuid":"a1","parentUuid":"u1","message":{"role":"assistant","content":[{"type":"text","text":"hello"}]}}\n'
+        )
+        session_file.write_bytes(raw_content.encode("utf-8"))
+        # Make the file read-only so write_bytes raises OSError on the write-back
+        session_file.chmod(0o444)
+
+        try:
+            with (
+                patch(
+                    "backend.copilot.sdk.service.projects_base",
+                    return_value=projects_base_dir,
+                ),
+                patch(
+                    "backend.copilot.transcript.projects_base",
+                    return_value=projects_base_dir,
+                ),
+            ):
+                result = _read_cli_session_from_disk(sdk_cwd, session_id, "[Test]")
+        finally:
+            session_file.chmod(0o644)
+
+        # Must return stripped bytes (not raw, not None) so GCS gets the clean version
+        assert result is not None
+        assert (
+            b"progress" not in result
+        ), "Stripped bytes must not contain progress entry"
+        assert b"hello" in result, "Stripped bytes should contain assistant turn"

autogpt_platform/backend/backend/copilot/transcript.py

@@ -55,9 +55,8 @@ TranscriptMode = Literal["sdk", "baseline"]
 class TranscriptDownload:
     content: bytes
     message_count: int = 0
-    mode: TranscriptMode = (
-        "sdk"  # "sdk" = Claude CLI native, "baseline" = TranscriptBuilder
-    )
+    # "sdk" = Claude CLI native, "baseline" = TranscriptBuilder
+    mode: TranscriptMode = "sdk"
 
 
 # Storage prefix for the CLI's native session JSONL files (for cross-pod --resume).