diff --git a/ebuild/cli/commands.py b/ebuild/cli/commands.py
index d16b9ee..b8366e1 100644
--- a/ebuild/cli/commands.py
+++ b/ebuild/cli/commands.py
@@ -508,15 +508,28 @@ def _selected_board(default: str = "generic") -> str:
     the documented walk, so the value has to survive from `ebuild new` or
     `ebuild configure`.
     """
-    path = Path("eos.yaml")
+    data = _read_yaml_mapping(Path(_EOS_PROJECT_CONFIG)) or {}
+    system = data.get("system")
+    board = system.get("board") if isinstance(system, dict) else None
+    return board or default
+
+
+def _read_yaml_mapping(path: Path) -> Optional[Dict[str, Any]]:
+    """The top-level mapping in ``path``, or None if there is not one.
+
+    For optional project files read after a build has already succeeded:
+    a missing, unreadable, malformed or non-mapping file is treated as
+    absent rather than raised, because callers index into the result and
+    a traceback there would fail a build that linked.
+    """
     if not path.is_file():
-        return default
+        return None
     try:
         import yaml
-        data = yaml.safe_load(path.read_text(encoding="utf-8")) or {}
+        data = yaml.safe_load(path.read_text(encoding="utf-8"))
     except Exception:
-        return default
-    return (data.get("system") or {}).get("board") or default
+        return None
+    return data if isinstance(data, dict) else None
 
 
 def _build_summary(cfg: "ProjectConfig", compiler, package_paths, log: Logger) -> None:
@@ -622,15 +635,7 @@ def _board_config() -> Optional[Dict[str, Any]]:
     A project that states its part's real capacity should not be measured
     against the reference part for its family.
     """
-    path = Path("board.yaml")
-    if not path.is_file():
-        return None
-    try:
-        import yaml
-        data = yaml.safe_load(path.read_text(encoding="utf-8"))
-    except Exception:
-        return None
-    return data if isinstance(data, dict) else None
+    return _read_yaml_mapping(Path("board.yaml"))
 
 
 def _configure_ninja_backend(
diff --git a/tests/unit/test_golden_path.py b/tests/unit/test_golden_path.py
index 230777d..ce576d7 100644
--- a/tests/unit/test_golden_path.py
+++ b/tests/unit/test_golden_path.py
@@ -1,6 +1,7 @@
 """ebuild init / sim / platforms: the getting-started guide's commands."""
 from __future__ import annotations
 
+import shlex
 import stat
 import sys
 import textwrap
@@ -15,9 +16,19 @@
 
 
 def _fake_qemu(tmp_path: Path, body: str) -> str:
-    """A stand-in qemu: a Python script that prints like a guest would."""
+    """A stand-in qemu: a Python script that prints like a guest would.
+
+    Launched through a /bin/sh wrapper rather than a `#!{sys.executable}`
+    shebang, because a shebang cannot carry an interpreter path containing
+    spaces (e.g. a checkout under "My Projects/"), and the exec then fails
+    with ENOENT before the test exercises anything.
+    """
+    guest = tmp_path / "fake_guest.py"
+    guest.write_text(textwrap.dedent(body), encoding="utf-8")
     script = tmp_path / "fake-qemu"
-    script.write_text(f"#!{sys.executable}\n" + textwrap.dedent(body), encoding="utf-8")
+    script.write_text(
+        f'#!/bin/sh\nexec {shlex.quote(sys.executable)} {shlex.quote(str(guest))} "$@"\n',
+        encoding="utf-8")
     script.chmod(script.stat().st_mode | stat.S_IEXEC)
     return str(script)
 
diff --git a/tests/unit/test_golden_path_commands.py b/tests/unit/test_golden_path_commands.py
index 951ac26..794ec62 100644
--- a/tests/unit/test_golden_path_commands.py
+++ b/tests/unit/test_golden_path_commands.py
@@ -76,6 +76,19 @@ def test_board_defaults_when_unset(self, tmp_path, monkeypatch):
         monkeypatch.chdir(tmp_path)
         assert _selected_board() == "generic"
 
+    @pytest.mark.parametrize("text", [
+        "- stm32f4\n",            # top level is a list
+        "system: stm32f4\n",      # system is a string, not a mapping
+        "system: {board: [unclosed\n",  # not valid YAML
+    ])
+    def test_a_malformed_eos_yaml_falls_back_instead_of_raising(
+            self, tmp_path, monkeypatch, text):
+        """`ebuild build` reads the board back after the image has linked, to
+        print its summary. A traceback there would fail a successful build."""
+        monkeypatch.chdir(tmp_path)
+        Path("eos.yaml").write_text(text, encoding="utf-8")
+        assert _selected_board() == "generic"
+
     def test_board_without_a_project_is_an_error(self, tmp_path, monkeypatch):
         """Refuse rather than write an eos.yaml into whatever directory the
         developer happened to be standing in."""