diff --git a/.claude-plugin/marketplace.json b/.claude-plugin/marketplace.json
index 9ebded7e..1b5a43a2 100644
--- a/.claude-plugin/marketplace.json
+++ b/.claude-plugin/marketplace.json
@@ -10,7 +10,7 @@
   "plugins": [
     {
       "name": "kbagent",
-      "version": "0.30.5",
+      "version": "0.30.6",
       "source": "./plugins/kbagent",
       "description": "AI-friendly interface to Keboola Connection projects — explore configs, jobs, lineage, call MCP tools, manage dev branches, and debug SQL in workspaces",
       "category": "development"
diff --git a/plugins/kbagent/.claude-plugin/plugin.json b/plugins/kbagent/.claude-plugin/plugin.json
index 2df7c46f..5d976416 100644
--- a/plugins/kbagent/.claude-plugin/plugin.json
+++ b/plugins/kbagent/.claude-plugin/plugin.json
@@ -1,6 +1,6 @@
 {
   "name": "kbagent",
-  "version": "0.30.5",
+  "version": "0.30.6",
   "description": "AI-friendly interface to Keboola Connection projects — explore configs, jobs, lineage, call MCP tools, manage dev branches, and debug SQL in workspaces",
   "author": {
     "name": "Keboola",
diff --git a/pyproject.toml b/pyproject.toml
index 399d7a81..5aed53cb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "keboola-agent-cli"
-version = "0.30.5"
+version = "0.30.6"
 description = "AI-friendly CLI for managing Keboola projects"
 readme = "README.md"
 requires-python = ">=3.12"
diff --git a/src/keboola_agent_cli/changelog.py b/src/keboola_agent_cli/changelog.py
index e07c114f..403e1055 100644
--- a/src/keboola_agent_cli/changelog.py
+++ b/src/keboola_agent_cli/changelog.py
@@ -8,6 +8,10 @@
 
 # Ordered newest-first.  Each value is a list of brief one-line descriptions.
 CHANGELOG: dict[str, list[str]] = {
+    "0.30.6": [
+        "UX (sec-20 follow-up): malformed `.keboola/branch-mapping.json` now surfaces as a clean JSON error envelope (exit 5, `CONFIG_ERROR`) instead of a raw Python traceback. v0.30.5 introduced the descriptive `Invalid branch ID in branch-mapping.json` message but `load_branch_mapping()` raised it as a bare `ValueError` -- which CLI commands did not catch, so an end user with a hand-edited mapping file saw a multi-frame traceback dumped to stderr instead of a one-line error. Fixed by raising `ConfigError` from `load_branch_mapping()` directly; existing CLI `except ConfigError` handlers now produce the standard error envelope. Found during v0.30.5 e2e smoke test against the kbagent-e2e project; not a security regression but a clear UX cleanup. The descriptive content of the error is unchanged; only the wrapper class differs.",
+        "Tests: `test_load_branch_mapping_invalid_id_includes_path` updated to assert `ConfigError` instead of `ValueError`. `cleanup_branch_id_from_mapping()` extended to catch `ConfigError` alongside the legacy `ValueError` so its best-effort behavior is preserved. `BranchMapping.from_dict()` continues to raise `ValueError` (it's the data-parser layer); only `load_branch_mapping()` (the filesystem-aware wrapper) was promoted to `ConfigError`.",
+    ],
     "0.30.5": [
         "Security (critical): `kbagent sync pull` no longer permits API-controlled `component_id` or `component_type` to escape the sync workspace via path traversal. `naming.config_path()` now passes both fields through a new `sanitize_path_segment()` that rejects `/`, `\\`, and parent-directory references (`..`) while preserving the dots, hyphens, and underscores in legitimate component IDs (`keboola.ex-db-mysql`, `kds-team.app-custom-python`). `services/sync_service.py:pull()` adds a defense-in-depth confinement check that raises ConfigError if a resolved config path is not contained in the branch directory. Issue #269 sec-01 / sec-07; threat actor: compromised stack or supply-chain attack on the project token. Pre-fix, `component_id = '../../../etc'` would write outside the project root.",
         "Security (high): MCP HTTP transport subprocess no longer inherits Keboola tokens from the kbagent process environment. `mcp_transport.py:_start()` previously used `subprocess.Popen(cmd, ...)` with no `env=` argument, so when `KBAGENT_MCP_TRANSPORT=http` was set, the MCP server inherited `KBC_MASTER_TOKEN`, `KBC_MASTER_TOKEN_<ALIAS>`, `KBC_MANAGE_API_TOKEN`, and `KBC_TOKEN`. New `_build_minimal_env()` allow-lists only the env vars needed for binary discovery and locale handling (PATH, HOME, USER, LANG, LC_*, UV_CACHE_DIR, PYTHONPATH, ...) and explicitly drops every `KBC_*` token. Per-project Storage tokens still flow through HTTP request headers as before. Issue #269 sec-02 / sec-08; closes the gap left by v0.29.0's manage-token default-deny on the HTTP transport path.",
diff --git a/src/keboola_agent_cli/commands/sync.py b/src/keboola_agent_cli/commands/sync.py
index 3433e5a3..fb92a64c 100644
--- a/src/keboola_agent_cli/commands/sync.py
+++ b/src/keboola_agent_cli/commands/sync.py
@@ -994,6 +994,14 @@ def sync_branch_status(
     except FileNotFoundError as exc:
         formatter.error(message=str(exc), error_code=ErrorCode.NOT_INITIALIZED)
         raise typer.Exit(code=1) from None
+    except ConfigError as exc:
+        # Corrupted .keboola/branch-mapping.json -- surface as clean
+        # exit-5 envelope so the user sees the descriptive message
+        # ("Failed to parse ...: Invalid branch ID ...") instead of a
+        # Python traceback. Mirrors the handler other sync commands
+        # already have (issue #269 sec-20 follow-up).
+        formatter.error(message=exc.message, error_code=ErrorCode.CONFIG_ERROR)
+        raise typer.Exit(code=5) from None
 
     if formatter.json_mode:
         formatter.output(result)
diff --git a/src/keboola_agent_cli/sync/branch_mapping.py b/src/keboola_agent_cli/sync/branch_mapping.py
index acbbb389..1b4a8f28 100644
--- a/src/keboola_agent_cli/sync/branch_mapping.py
+++ b/src/keboola_agent_cli/sync/branch_mapping.py
@@ -11,6 +11,7 @@
 from typing import Any
 
 from ..constants import BRANCH_MAPPING_FILENAME, KEBOOLA_DIR_NAME
+from ..errors import ConfigError
 
 
 def _coerce_keboola_id(raw: Any) -> int | None:
@@ -94,9 +95,13 @@ def load_branch_mapping(project_root: Path) -> BranchMapping:
 
     Raises:
         FileNotFoundError: If the mapping file does not exist.
-        ValueError: If the JSON cannot be parsed or contains a malformed
+        ConfigError: If the JSON cannot be parsed or contains a malformed
             branch ID. The descriptive message names the offending file
-            so the user can find and fix it (issue #269 sec-20).
+            so the user can find and fix it. Surfacing this as ConfigError
+            (rather than raw ValueError) lets CLI commands catch it via
+            the existing ``except ConfigError`` handler and emit a clean
+            JSON error envelope with exit code 5 instead of a Python
+            traceback (issue #269 sec-20 + smoke-test follow-up).
     """
     path = project_root / KEBOOLA_DIR_NAME / BRANCH_MAPPING_FILENAME
     if not path.exists():
@@ -105,9 +110,10 @@ def load_branch_mapping(project_root: Path) -> BranchMapping:
         data = json.loads(path.read_text(encoding="utf-8"))
         return BranchMapping.from_dict(data)
     except ValueError as exc:
-        # _coerce_keboola_id raises ValueError on malformed IDs; wrap with
-        # path context so the user knows which file to fix.
-        raise ValueError(f"Failed to parse {path}: {exc}") from exc
+        # _coerce_keboola_id and json.loads both raise ValueError on
+        # malformed input; wrap with path context and convert to
+        # ConfigError so the CLI surfaces a clean error envelope.
+        raise ConfigError(f"Failed to parse {path}: {exc}") from exc
 
 
 def save_branch_mapping(project_root: Path, mapping: BranchMapping) -> None:
@@ -150,7 +156,10 @@ def cleanup_branch_id_from_mapping(branch_id: int) -> dict[str, Any] | None:
         return None
     try:
         mapping = load_branch_mapping(project_root)
-    except (FileNotFoundError, ValueError):
+    except (FileNotFoundError, ConfigError, ValueError):
+        # ValueError preserved for backward compat with callers that may
+        # still trigger it via custom paths; ConfigError is the new shape
+        # raised by load_branch_mapping itself.
         return None
 
     removed: list[str] = []
diff --git a/tests/test_sync_branch_mapping.py b/tests/test_sync_branch_mapping.py
index 011ab19e..a062aa34 100644
--- a/tests/test_sync_branch_mapping.py
+++ b/tests/test_sync_branch_mapping.py
@@ -12,6 +12,7 @@
 import pytest
 
 from keboola_agent_cli.constants import BRANCH_MAPPING_FILENAME, KEBOOLA_DIR_NAME
+from keboola_agent_cli.errors import ConfigError
 from keboola_agent_cli.sync.branch_mapping import (
     BranchMapping,
     BranchMappingEntry,
@@ -175,8 +176,11 @@ def test_branch_mapping_from_dict_invalid_id_descriptive_error(self) -> None:
         with pytest.raises(ValueError, match="Invalid branch ID"):
             BranchMapping.from_dict(data)
 
-    def test_load_branch_mapping_invalid_id_includes_path(self, tmp_path: Path) -> None:
-        """``load_branch_mapping`` wraps the descriptive error with the file path."""
+    def test_load_branch_mapping_invalid_id_raises_config_error(self, tmp_path: Path) -> None:
+        """``load_branch_mapping`` wraps the descriptive error with the file
+        path AND raises ConfigError so CLI commands surface a clean exit-5
+        envelope instead of a Python traceback (issue #269 sec-20 follow-up).
+        """
         keboola_dir = tmp_path / KEBOOLA_DIR_NAME
         keboola_dir.mkdir()
         (keboola_dir / BRANCH_MAPPING_FILENAME).write_text(
@@ -189,7 +193,7 @@ def test_load_branch_mapping_invalid_id_includes_path(self, tmp_path: Path) -> N
                 }
             )
         )
-        with pytest.raises(ValueError, match=r"Failed to parse .*branch-mapping\.json"):
+        with pytest.raises(ConfigError, match=r"Failed to parse .*branch-mapping\.json"):
             load_branch_mapping(tmp_path)
 
 
diff --git a/tests/test_sync_cli.py b/tests/test_sync_cli.py
index 1190ca2f..3ade3529 100644
--- a/tests/test_sync_cli.py
+++ b/tests/test_sync_cli.py
@@ -1563,6 +1563,47 @@ def test_sync_branch_status_disabled_human(self, tmp_path: Path) -> None:
         assert result.exit_code == 0, f"Exit code {result.exit_code}: {result.output}"
         assert "not enabled" in result.output
 
+    def test_sync_branch_status_corrupted_mapping_clean_envelope(self, tmp_path: Path) -> None:
+        """A corrupted .keboola/branch-mapping.json must produce a clean
+        JSON error envelope (exit 5, CONFIG_ERROR), not a Python traceback
+        (issue #269 sec-20 follow-up + #273 reviewer feedback)."""
+        from keboola_agent_cli.errors import ConfigError
+
+        config_dir = tmp_path / "config"
+        config_dir.mkdir()
+
+        store = _setup_config(config_dir, {"prod": {"token": TEST_TOKEN}})
+
+        mock_sync = _make_sync_service_mock()
+        # Service raises ConfigError as load_branch_mapping now does for
+        # malformed mappings. CLI must catch it.
+        mock_sync.branch_status.side_effect = ConfigError(
+            "Failed to parse /tmp/.keboola/branch-mapping.json: "
+            "Invalid branch ID in branch-mapping.json: 'not-a-number'. "
+            "Expected null or an integer; got str."
+        )
+
+        with (
+            patch("keboola_agent_cli.cli.ConfigStore") as MockStore,
+            patch("keboola_agent_cli.cli.ProjectService") as MockProjService,
+            patch("keboola_agent_cli.cli.SyncService") as MockSyncService,
+        ):
+            MockStore.return_value = store
+            MockProjService.return_value = ProjectService(config_store=store)
+            MockSyncService.return_value = mock_sync
+
+            result = runner.invoke(
+                app,
+                ["--json", "sync", "branch-status", "--directory", str(tmp_path)],
+            )
+
+        assert result.exit_code == 5, f"expected exit 5, got {result.exit_code}: {result.output}"
+        assert "Traceback" not in result.output
+        data = json.loads(result.output)
+        assert data["status"] == "error"
+        assert data["error"]["code"] == "CONFIG_ERROR"
+        assert "Invalid branch ID" in data["error"]["message"]
+
 
 class TestSyncInitAdoptExistingCli:
     """Tests for `kbagent sync init --adopt-existing`."""
diff --git a/uv.lock b/uv.lock
index 2ccb8ed7..f1101073 100644
--- a/uv.lock
+++ b/uv.lock
@@ -439,7 +439,7 @@ wheels = [
 
 [[package]]
 name = "keboola-agent-cli"
-version = "0.30.5"
+version = "0.30.6"
 source = { editable = "." }
 dependencies = [
     { name = "httpx" },