fix: Empty error messages in add_golden_repo_index subprocess failures (Bug #361, v9.3.98)

When index creation failed and the error was in stdout (not stderr),
error messages showed "Failed to create FTS index: " with nothing
after the colon. Applied stderr→stdout→exit-code fallback chain to
all 5 index types (init, semantic, fts, temporal, scip) plus the
CalledProcessError handler.

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

Author: jsbattig

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## v9.3.98
+
+### Bug Fixes
+
+- fix: add_golden_repo_index shows empty error messages when subprocess fails (Bug #361). When index creation failed and the error was in stdout (not stderr), the error message showed "Failed to create FTS index: " with nothing after the colon. Applied stderr-or-stdout-or-exit-code fallback chain to all 5 index types (init, semantic, fts, temporal, scip) plus the CalledProcessError handler, ensuring diagnostic information is always present in error messages.
+
 ## v9.3.97
 
 ### Bug Fixes

README.md

@@ -2,7 +2,7 @@
 
 AI-powered semantic code search for your codebase. Find code by meaning, not just keywords.
 
-**Version 9.3.97** - [Changelog](CHANGELOG.md) | [Migration Guide](docs/migration-to-v8.md) | [Architecture](docs/architecture.md)
+**Version 9.3.98** - [Changelog](CHANGELOG.md) | [Migration Guide](docs/migration-to-v8.md) | [Architecture](docs/architecture.md)
 
 ## Quick Navigation
 

src/code_indexer/__init__.py

@@ -6,5 +6,5 @@
 HNSW graph indexing (O(log N) complexity).
 """
 
-__version__ = "9.3.97"
+__version__ = "9.3.98"
 __author__ = "Seba Battig"

src/code_indexer/server/repositories/golden_repo_manager.py

@@ -2388,8 +2388,13 @@ def background_worker() -> Dict[str, Any]:
                     init_result.returncode != 0
                     and "already exists" not in init_output.lower()
                 ):
+                    error_details = (
+                        init_result.stderr
+                        or init_result.stdout
+                        or f"Exit code {init_result.returncode}"
+                    )
                     raise GoldenRepoError(
-                        f"Failed to initialize repo before indexing: {init_result.stderr}"
+                        f"Failed to initialize repo before indexing: {error_details}"
                     )
                 # Capture output for logging regardless of outcome
                 if init_result.stdout:
@@ -2409,8 +2414,13 @@ def background_worker() -> Dict[str, Any]:
                     captured_stdout = result.stdout
                     captured_stderr = result.stderr
                     if result.returncode != 0:
+                        error_details = (
+                            result.stderr
+                            or result.stdout
+                            or f"Exit code {result.returncode}"
+                        )
                         raise GoldenRepoError(
-                            f"Failed to create semantic index: {result.stderr}"
+                            f"Failed to create semantic index: {error_details}"
                         )
 
                 # fts - execute cidx index --rebuild-fts-index (FTS only)
@@ -2425,8 +2435,13 @@ def background_worker() -> Dict[str, Any]:
                     captured_stdout = result.stdout
                     captured_stderr = result.stderr
                     if result.returncode != 0:
+                        error_details = (
+                            result.stderr
+                            or result.stdout
+                            or f"Exit code {result.returncode}"
+                        )
                         raise GoldenRepoError(
-                            f"Failed to create FTS index: {result.stderr}"
+                            f"Failed to create FTS index: {error_details}"
                         )
 
                 # temporal - execute cidx index --index-commits with options
@@ -2458,8 +2473,13 @@ def background_worker() -> Dict[str, Any]:
                     captured_stdout = result.stdout
                     captured_stderr = result.stderr
                     if result.returncode != 0:
+                        error_details = (
+                            result.stderr
+                            or result.stdout
+                            or f"Exit code {result.returncode}"
+                        )
                         raise GoldenRepoError(
-                            f"Failed to create temporal index: {result.stderr}"
+                            f"Failed to create temporal index: {error_details}"
                         )
 
                     # Bug #131: Update enable_temporal flag in BOTH tables after successful temporal index creation
@@ -2527,8 +2547,13 @@ def background_worker() -> Dict[str, Any]:
                     captured_stdout = result.stdout
                     captured_stderr = result.stderr
                     if result.returncode != 0:
+                        error_details = (
+                            result.stderr
+                            or result.stdout
+                            or f"Exit code {result.returncode}"
+                        )
                         raise GoldenRepoError(
-                            f"Failed to create SCIP index: {result.stderr}"
+                            f"Failed to create SCIP index: {error_details}"
                         )
 
                 return {
@@ -2539,8 +2564,13 @@ def background_worker() -> Dict[str, Any]:
                     "stderr": captured_stderr,
                 }
             except subprocess.CalledProcessError as e:
+                error_details = (
+                    e.stderr
+                    or e.stdout
+                    or f"Exit code {e.returncode}"
+                )
                 raise GoldenRepoError(
-                    f"Failed to add index: Command failed with exit code {e.returncode}: {e.stderr}"
+                    f"Failed to add index: Command failed: {error_details}"
                 )
             except Exception as e:
                 raise GoldenRepoError(f"Failed to add index: {str(e)}")