@@ -195,7 +195,10 @@ The host runner is `tests/smoke/run_example.py`. Shipped examples are listed in
   the sidecar check owns, `{"args": [...], "expect_sidecar_fail": true}`.
   A falsifier that targets a version-specific API change takes
   `"min_version": "5.2"` and is recorded as SKIP below it (its README must
-  say it exits 0 there).
+  say it exits 0 there). When other checks in the example return the same
+  code, the falsifier also carries `"expect_output"`: a substring of the
+  targeted check's message, which must appear in the run's output
+  (`check_smoke_catalog.py` requires it, #532).
   `run_catalog.py` runs each after the row's happy path; it passes only on
   exactly that exit. `tests/check_smoke_catalog.py` rejects a row without one
   and any unknown key. The weekly cron also runs the full showcase sweep
 
@@ -158,7 +158,9 @@ example needs:
    `3` up) and a falsifier: a flag that breaks the contract so one named check
    exits with its own code.
 2. A `tests/smoke/catalog.json` row with at least one falsifier
-   (`{"args": ["--your-flag"], "expect_exit": N}`). `tests/check_smoke_catalog.py`
+   (`{"args": ["--your-flag"], "expect_exit": N}`; add `"expect_output": "<the
+   check's error message>"` when other checks return the same code).
+   `tests/check_smoke_catalog.py`
    rejects a row without one.
 3. An `examples/skills.json` entry naming the skills it proves, then
    `python scripts/build_examples_index.py` (Validate fails on a missing entry).
 
@@ -10,7 +10,9 @@
 otherwise be ignored and the falsifier silently never run), and every row
 carries at least one falsifier: {"args": [...], "expect_exit": N} with N not
 0, 1, 2 (argparse usage) or 77, or {"args": [...], "expect_sidecar_fail": true} on a row that
-declares expect_sidecar.
+declares expect_sidecar. An expect_exit falsifier may add "expect_output": a
+substring of the targeted check's message, required when other checks in the
+script exit the same code (#532).
 
     python tests/check_smoke_catalog.py [--root PATH]
 
@@ -20,9 +22,11 @@
 from __future__ import annotations
 
 import argparse
+import ast
 import json
 import re
 import sys
+from collections import Counter
 from pathlib import Path
 
 sys.path.insert(0, str(Path(__file__).resolve().parent / "smoke"))
@@ -33,7 +37,8 @@
 
 ROW_KEYS = {"name", "script", "args", "min_version", "expect_file",
             "expect_sidecar", "sidecar_contains", "falsifiers", "timeout"}
-FALSIFIER_KEYS = {"args", "expect_exit", "expect_sidecar_fail", "min_version"}
+FALSIFIER_KEYS = {"args", "expect_exit", "expect_sidecar_fail", "expect_output",
+                  "min_version"}
 # Defined once in tests/smoke/protocol.py, which explains each code.
 FORBIDDEN_EXITS = set(FORBIDDEN_FALSIFIER_EXITS)
 
@@ -70,6 +75,10 @@ def check_schema(row: dict) -> list[str]:
                 errors.append(f"{where}: expect_exit {code!r} must be an int other than 0, 1, 2, 77")
         elif not row.get("expect_sidecar"):
             errors.append(f"{where}: expect_sidecar_fail on a row with no expect_sidecar")
+        eo = f.get("expect_output")
+        if eo is not None and not (isinstance(eo, str) and eo.strip() and has_exit):
+            errors.append(f"{where}: expect_output must be a non-empty string on an "
+                          f"expect_exit falsifier")
         mv = f.get("min_version")
         if mv is not None and not (isinstance(mv, str) and re.fullmatch(r"[0-9]+[.][0-9]+", mv)):
             errors.append(f"{where}: min_version {mv!r} must look like '5.2'")
@@ -94,6 +103,41 @@ def check_readme_claims(root: Path, row: dict) -> list[str]:
             f"but it is this row's catalog falsifier" for flag in sorted(named & ran)]
 
 
+def exit_sites(script: Path) -> Counter:
+    """How many places in the script return or exit with each integer code."""
+    tree = ast.parse(script.read_text(encoding="utf-8"))
+    sites: Counter = Counter()
+    for node in ast.walk(tree):
+        value = None
+        if isinstance(node, ast.Return):
+            value = node.value
+        elif isinstance(node, ast.Call) and node.args and ast.unparse(node.func) in (
+                "sys.exit", "SystemExit", "exit"):
+            value = node.args[0]
+        if isinstance(value, ast.Constant) and type(value.value) is int:
+            sites[value.value] += 1
+    return sites
+
+
+def check_shared_exits(root: Path, row: dict) -> list[str]:
+    """An example falsifier whose code several checks return must name its own (#532).
+
+    The harness passes a falsifier on its exit code; when two checks share it,
+    the falsifier could trip the other one while the check it targets has lost
+    the ability to fail. expect_output pins the targeted check's message.
+    """
+    script = root / row["script"]
+    if Path(row["script"]).parts[0] != "examples" or not script.is_file():
+        return []
+    sites = exit_sites(script)
+    return [f"catalog row {row['name']!r} falsifier {' '.join(f['args'])}: exit "
+            f"{f['expect_exit']} is returned from {sites[f['expect_exit']]} places in "
+            f"{row['script']}; add expect_output naming the targeted check's message"
+            for f in row.get("falsifiers", [])
+            if isinstance(f, dict) and isinstance(f.get("expect_exit"), int)
+            and sites[f["expect_exit"]] > 1 and not f.get("expect_output")]
+
+
 def check(root: Path) -> list[str]:
     catalog = json.loads((root / "tests/smoke/catalog.json").read_text(encoding="utf-8"))
     if not catalog:
@@ -109,6 +153,7 @@ def check(root: Path) -> list[str]:
         if not (root / row["script"]).is_file():
             # otherwise only Blender, at runtime, notices a renamed script (#527)
             errors.append(f"catalog row {row.get('name')!r}: script {row['script']} does not exist")
+        errors += check_shared_exits(root, row)
         parts = Path(row["script"]).parts
         if len(parts) >= 2 and parts[0] in ("examples", "showcase"):
             key = f"{parts[0]}/{parts[1]}"
 
@@ -12,17 +12,17 @@
   {"name": "wave-displace", "script": "examples/wave-displace/wave_displace.py", "falsifiers": [{"args": ["--flat"], "expect_exit": 4}]},
   {"name": "driver-wave", "script": "examples/driver-wave/driver_wave.py", "falsifiers": [{"args": ["--flat-expr"], "expect_exit": 3}, {"args": ["--simple-expr"], "expect_exit": 5}, {"args": ["--swap-handlers"], "expect_exit": 7}]},
   {"name": "bmesh-gear", "script": "examples/bmesh-gear/bmesh_gear.py", "falsifiers": [{"args": ["--no-extrude"], "expect_exit": 3}]},
-  {"name": "shader-node-group", "script": "examples/shader-node-group/shader_node_group.py", "falsifiers": [{"args": ["--same-tint"], "expect_exit": 8}]},
+  {"name": "shader-node-group", "script": "examples/shader-node-group/shader_node_group.py", "falsifiers": [{"args": ["--same-tint"], "expect_exit": 8, "expect_output": "ERROR: rendered mug glazes not distinct"}]},
   {"name": "temp-override-join", "script": "examples/temp-override-join/temp_override_join.py", "falsifiers": [{"args": ["--no-override"], "expect_exit": 3}]},
   {"name": "gn-instance-grid", "script": "examples/gn-instance-grid/gn_instance_grid.py", "falsifiers": [{"args": ["--one-cell"], "expect_exit": 4}]},
   {"name": "gn-modifier-inputs", "script": "examples/gn-modifier-inputs/gn_modifier_inputs.py", "falsifiers": [{"args": ["--same-height"], "expect_exit": 8}, {"args": ["--api", "dict"], "expect_exit": 5, "min_version": "5.2"}]},
   {"name": "shape-key-blend", "script": "examples/shape-key-blend/shape_key_blend.py", "falsifiers": [{"args": ["--zero-blend"], "expect_exit": 5}]},
   {"name": "curve-bevel-arc", "script": "examples/curve-bevel-arc/curve_bevel_arc.py", "falsifiers": [{"args": ["--no-caps"], "expect_exit": 7}]},
-  {"name": "compositor-glare", "script": "examples/compositor-glare/compositor_glare.py", "falsifiers": [{"args": ["--threshold-high"], "expect_exit": 4}]},
+  {"name": "compositor-glare", "script": "examples/compositor-glare/compositor_glare.py", "falsifiers": [{"args": ["--threshold-high"], "expect_exit": 4, "expect_output": "ERROR: no bloom halo beyond the silhouette"}]},
   {"name": "damped-track-aim", "script": "examples/damped-track-aim/damped_track_aim.py", "falsifiers": [{"args": ["--mute"], "expect_exit": 9}]},
   {"name": "color-attribute-wheel", "script": "examples/color-attribute-wheel/color_attribute_wheel.py", "falsifiers": [{"args": ["--point-domain"], "expect_exit": 6}]},
   {"name": "parent-inverse-orrery", "script": "examples/parent-inverse-orrery/parent_inverse_orrery.py", "falsifiers": [{"args": ["--skip-mpi"], "expect_exit": 6}]},
-  {"name": "grease-pencil-rosette", "script": "examples/grease-pencil-rosette/grease_pencil_rosette.py", "falsifiers": [{"args": ["--open-strokes"], "expect_exit": 5}]},
+  {"name": "grease-pencil-rosette", "script": "examples/grease-pencil-rosette/grease_pencil_rosette.py", "falsifiers": [{"args": ["--open-strokes"], "expect_exit": 5, "expect_output": "ERROR: not every stroke is cyclic"}]},
   {"name": "gp-lineart-contour", "script": "examples/gp-lineart-contour/gp_lineart_contour.py", "falsifiers": [{"args": ["--no-contour"], "expect_exit": 5}]},
   {"name": "armature-bend", "script": "examples/armature-bend/armature_bend.py", "falsifiers": [{"args": ["--zero-curl"], "expect_exit": 8}]},
   {"name": "text-version-stamp", "script": "examples/text-version-stamp/text_version_stamp.py", "falsifiers": [{"args": ["--wrong-body"], "expect_exit": 4}]},
@@ -54,18 +54,18 @@
   {"name": "attribute-domain-shear", "script": "examples/attribute-domain-shear/attribute_domain_shear.py", "falsifiers": [{"args": ["--no-overwrite"], "expect_exit": 5}]},
   {"name": "degenerate-bevel-weld", "script": "examples/degenerate-bevel-weld/degenerate_bevel_weld.py", "falsifiers": [{"args": ["--both-safe"], "expect_exit": 4}]},
   {"name": "modular-kit-snap", "script": "examples/modular-kit-snap/modular_kit_snap.py", "falsifiers": [{"args": ["--seam-gap"], "expect_exit": 5}]},
-  {"name": "lightmap-uv-channel", "script": "examples/lightmap-uv-channel/lightmap_uv_channel.py", "falsifiers": [{"args": ["--overlap-islands"], "expect_exit": 7}]},
-  {"name": "socket-attach-points", "script": "examples/socket-attach-points/socket_attach_points.py", "falsifiers": [{"args": ["--skip-mpi"], "expect_exit": 3}]},
+  {"name": "lightmap-uv-channel", "script": "examples/lightmap-uv-channel/lightmap_uv_channel.py", "falsifiers": [{"args": ["--overlap-islands"], "expect_exit": 7, "expect_output": "overlapping UV1 triangle pairs"}]},
+  {"name": "socket-attach-points", "script": "examples/socket-attach-points/socket_attach_points.py", "falsifiers": [{"args": ["--skip-mpi"], "expect_exit": 3, "expect_output": "world matrix deviates"}]},
   {"name": "vertex-color-ao", "script": "examples/vertex-color-ao/vertex_color_ao.py", "falsifiers": [{"args": ["--uniform-hemisphere"], "expect_exit": 3}]},
-  {"name": "cross-version-property-delete", "script": "examples/cross-version-property-delete/cross_version_property_delete.py", "falsifiers": [{"args": ["--skip-delete"], "expect_exit": 7}, {"args": ["--subscript-registered"], "expect_exit": 8, "min_version": "5.0"}, {"args": ["--unset-instead"], "expect_exit": 7}]},
+  {"name": "cross-version-property-delete", "script": "examples/cross-version-property-delete/cross_version_property_delete.py", "falsifiers": [{"args": ["--skip-delete"], "expect_exit": 7}, {"args": ["--subscript-registered"], "expect_exit": 8, "min_version": "5.0", "expect_output": "on 5.0+ a registered bpy.props value is not an ID property"}, {"args": ["--unset-instead"], "expect_exit": 7}]},
   {"name": "usd-export-evaluation-mode", "script": "examples/usd-export-evaluation-mode/usd_export_evaluation_mode.py", "falsifiers": [{"args": ["--subdivision", "BEST_MATCH"], "expect_exit": 4}, {"args": ["--evaluation-mode", "VIEWPORT"], "expect_exit": 4}]},
   {"name": "gn-zone-iterate", "script": "examples/gn-zone-iterate/gn_zone_iterate.py", "falsifiers": [{"args": ["--unpair-repeat"], "expect_exit": 3}, {"args": ["--no-offset"], "expect_exit": 4}, {"args": ["--unpair-foreach"], "expect_exit": 5}, {"args": ["--foreach-main"], "expect_exit": 5}]},
-  {"name": "gn-sim-fountain", "script": "examples/gn-sim-fountain/gn_sim_fountain.py", "falsifiers": [{"args": ["--unpair"], "expect_exit": 3}, {"args": ["--euler"], "expect_exit": 4}, {"args": ["--prebake-trap"], "expect_exit": 5}, {"args": ["--calc-to-frame"], "expect_exit": 6}]},
+  {"name": "gn-sim-fountain", "script": "examples/gn-sim-fountain/gn_sim_fountain.py", "falsifiers": [{"args": ["--unpair"], "expect_exit": 3, "expect_output": "an unpaired zone outputs nothing"}, {"args": ["--euler"], "expect_exit": 4, "expect_output": "miss p0 + v0 t - g t^2/2"}, {"args": ["--prebake-trap"], "expect_exit": 5}, {"args": ["--calc-to-frame"], "expect_exit": 6}]},
   {
     "name": "gn-bundle-roundtrip",
     "script": "examples/gn-bundle-roundtrip/gn_bundle_roundtrip.py",
     "min_version": "5.0",
-    "falsifiers": [{"args": ["--legacy-rna"], "expect_exit": 7}, {"args": ["--mismatch"], "expect_exit": 3}, {"args": ["--bypass"], "expect_exit": 4}, {"args": ["--mismatch-mark"], "expect_exit": 5}]
+    "falsifiers": [{"args": ["--legacy-rna"], "expect_exit": 7}, {"args": ["--mismatch"], "expect_exit": 3}, {"args": ["--bypass"], "expect_exit": 4}, {"args": ["--mismatch-mark"], "expect_exit": 5, "expect_output": "ERROR: bundle_mark"}]
   },
   {
     "name": "exit-pre-sidecar",
@@ -83,7 +83,7 @@
   },
   {"name": "mesh-normals-after-41", "script": "examples/mesh-normals-after-41/mesh_normals_after_41.py", "falsifiers": [{"args": ["--legacy-api"], "expect_exit": 3}, {"args": ["--sharp-angle", "10"], "expect_exit": 4}, {"args": ["--flatten-after"], "expect_exit": 5}, {"args": ["--skip-set-sharp"], "expect_exit": 6}]},
   {"name": "addon-register-lifecycle", "script": "examples/addon-register-lifecycle/addon_register_lifecycle.py", "falsifiers": [{"args": ["--drop-manifest"], "expect_exit": 3}, {"args": ["--legacy-gets-manifest"], "expect_exit": 4}, {"args": ["--skip-pointer"], "expect_exit": 5}, {"args": ["--classes-first"], "expect_exit": 6}]},
-  {"name": "ngon-triangulate", "script": "examples/ngon-triangulate/ngon_triangulate.py", "falsifiers": [{"args": ["--no-dissolve"], "expect_exit": 3}, {"args": ["--skip-triangulate"], "expect_exit": 4}]},
+  {"name": "ngon-triangulate", "script": "examples/ngon-triangulate/ngon_triangulate.py", "falsifiers": [{"args": ["--no-dissolve"], "expect_exit": 3, "expect_output": "ERROR: pathology missing"}, {"args": ["--skip-triangulate"], "expect_exit": 4, "expect_output": "ERROR: triangulate handling failed"}]},
   {"name": "unapplied-scale-gltf", "script": "examples/unapplied-scale-gltf/unapplied_scale_gltf.py", "falsifiers": [{"args": ["--identity"], "expect_exit": 3}, {"args": ["--bake"], "expect_exit": 4}]},
   {"name": "coincident-vert-weld", "script": "examples/coincident-vert-weld/coincident_vert_weld.py", "falsifiers": [{"args": ["--no-duplicate"], "expect_exit": 3}, {"args": ["--weld"], "expect_exit": 4}]},
   {"name": "bake-normal-high-to-low", "script": "examples/bake-normal-high-to-low/bake_normal_high_to_low.py", "falsifiers": [{"args": ["--flat-source"], "expect_exit": 5}, {"args": ["--unselect-target"], "expect_exit": 4, "min_version": "5.0"}]},
@@ -93,9 +93,9 @@
   {"name": "timers-modal-threading", "script": "examples/timers-modal-threading/timers_modal_threading.py", "falsifiers": [{"args": ["--windowed-background-child"], "expect_exit": 3}, {"args": ["--return-zero-once"], "expect_exit": 5}, {"args": ["--return-late-once"], "expect_exit": 5}, {"args": ["--apply-in-worker"], "expect_exit": 6}, {"args": ["--no-event-timer"], "expect_exit": 7}, {"args": ["--non-persistent"], "expect_exit": 8}, {"args": ["--stop-after-first"], "expect_exit": 9}, {"args": ["--no-catch"], "expect_exit": 12}]},
   {"name": "eval-mesh-datablock-name", "script": "examples/eval-mesh-datablock-name/eval_mesh_datablock_name.py", "falsifiers": [{"args": ["--assume-distinct-names"], "expect_exit": 6, "min_version": "5.2"}]},
   {"name": "mesh-automasking-settings", "script": "examples/mesh-automasking-settings/mesh_automasking_settings.py", "falsifiers": [{"args": ["--assume-brush-attrs"], "expect_exit": 5, "min_version": "5.2"}]},
-  {"name": "ray-cast-space", "script": "examples/ray-cast-space/ray_cast_space.py", "falsifiers": [{"args": ["--world-to-object"], "expect_exit": 4}]},
-  {"name": "lattice-deform", "script": "examples/lattice-deform/lattice_deform.py", "falsifiers": [{"args": ["--bspline"], "expect_exit": 4}]},
-  {"name": "solidify-even-thickness", "script": "examples/solidify-even-thickness/solidify_even_thickness.py", "falsifiers": [{"args": ["--no-even"], "expect_exit": 4}]},
+  {"name": "ray-cast-space", "script": "examples/ray-cast-space/ray_cast_space.py", "falsifiers": [{"args": ["--world-to-object"], "expect_exit": 4, "expect_output": "ERROR: Object.ray_cast ray"}]},
+  {"name": "lattice-deform", "script": "examples/lattice-deform/lattice_deform.py", "falsifiers": [{"args": ["--bspline"], "expect_exit": 4, "expect_output": "verts off the trilinear closed form"}]},
+  {"name": "solidify-even-thickness", "script": "examples/solidify-even-thickness/solidify_even_thickness.py", "falsifiers": [{"args": ["--no-even"], "expect_exit": 4, "expect_output": "ERROR: even shell is"}]},
   {"name": "boolean-exact-volume", "script": "examples/boolean-exact-volume/boolean_exact_volume.py", "falsifiers": [{"args": ["--float-solver"], "expect_exit": 3}]},
   {"name": "extension-template-lifecycle", "script": "tests/smoke/check_extension_template.py", "falsifiers": [{"args": ["--skip-unregister"], "expect_exit": 4}]},
   {"name": "shipping-crate", "script": "showcase/shipping-crate/shipping_crate.py", "falsifiers": [{"args": ["--short-skids"], "expect_exit": 16}]},
 
@@ -82,6 +82,7 @@ def classify(
     sidecar_contains: Optional[str] = None,
     expect_exit: Optional[int] = None,
     expect_sidecar_fail: bool = False,
+    expect_output: Optional[str] = None,
 ) -> Tuple[str, str]:
     """Return (PASS|SKIP|FAIL, detail).
 
@@ -91,7 +92,10 @@ def classify(
 
     Falsifier runs invert the verdict. With ``expect_exit=N`` the run passes
     only when Blender exits exactly N: not 0 (the check did not fire), not
-    another code (an earlier check fired), not 1 (it crashed). With
+    another code (an earlier check fired), not 1 (it crashed). When several
+    checks share N, ``expect_output`` names the targeted check's message, which
+    must appear in the output too, so a different check exiting N cannot stand
+    in for the one the falsifier was written to break (#532). With
     ``expect_sidecar_fail`` the run passes only when the script exits 0 and
     the post-exit sidecar check then fails (falsifiers the harness, not the
     script, is meant to catch). A legal skip stays a skip either way.
@@ -112,6 +116,9 @@ def classify(
         if expect_exit in FORBIDDEN_FALSIFIER_EXITS:
             return FAIL, f"falsifier expects exit {expect_exit}, which names no check"
         if proc_exit == expect_exit:
+            if expect_output and expect_output not in output:
+                return FAIL, (f"falsifier exited {proc_exit} as declared, but not from the "
+                              f"targeted check: output lacks {expect_output!r}")
             return PASS, f"falsifier exited {proc_exit} as declared"
         if proc_exit == 0:
             return FAIL, f"falsifier did not fail (exit 0, expected {expect_exit})"
 
@@ -94,6 +94,8 @@ def row_cmd(item, run_name, extra, falsifier=None):
                 cmd.append("--expect-sidecar-fail")
             else:
                 cmd.extend(["--expect-exit", str(falsifier["expect_exit"])])
+                if falsifier.get("expect_output"):
+                    cmd.extend(["--expect-output", falsifier["expect_output"]])
         if extra:
             cmd.append("--")
             cmd.extend(extra)