@@ -31,7 +31,20 @@ def execute(self, render_context: RenderContext, previous_action_payload: Any |
         ctx.fix_attempts += 1
 
         if ctx.fix_attempts >= MAX_CONFORMANCE_TEST_FIX_ATTEMPTS:
-            if ctx.conformance_tests_render_attempts >= MAX_CONFORMANCE_TEST_RERENDER_ATTEMPTS:
+            # Regeneration only produces a coherent result for a test the module under
+            # render owns. RenderConformanceTests builds the replacement's folder under
+            # `render_context.module_name` and its specifications from
+            # `render_context.frid_context`, but records the entry against
+            # `current_testing_module_name` - so for a required module's test the files,
+            # the index entry and the specification all belong to different modules.
+            # Exhausting the fix attempts on one of those is a failed render, not a
+            # candidate for regeneration.
+            regeneration_would_apply_to_another_module = ctx.current_testing_module_name != render_context.module_name
+
+            if (
+                ctx.conformance_tests_render_attempts >= MAX_CONFORMANCE_TEST_RERENDER_ATTEMPTS
+                or regeneration_would_apply_to_another_module
+            ):
                 error_msg = f"The renderer was unable to produce an implementation that passes conformance tests for functionality '{render_context.frid_context.frid}' after many attempts. Please review and rewrite the specification. (Render ID: {render_context.run_state.render_id})"
                 render_context.last_error_message = error_msg
                 return (
 
@@ -396,8 +396,20 @@ def _handle_test_regeneration(self):
 
         console.info(f"Recreating conformance tests for functionality {ctx.current_testing_frid}.")
 
-        existing_folder = ctx.get_conformance_tests_json(ctx.current_testing_module_name).pop(ctx.current_testing_frid)
-        file_utils.delete_folder(existing_folder["folder_name"])
+        # Popped with a default: the entry is gone if a previous regeneration removed it
+        # and the re-render recorded the replacement elsewhere. There is then nothing to
+        # delete, and the test is rendered fresh either way - a state that should not
+        # arise is not worth ending a render that has run for an hour.
+        existing_folder = ctx.get_conformance_tests_json(ctx.current_testing_module_name).pop(
+            ctx.current_testing_frid, None
+        )
+        if existing_folder is None:
+            console.warning(
+                f"No conformance test recorded for functionality {ctx.current_testing_frid} of module "
+                f"{ctx.current_testing_module_name}; regenerating without deleting one."
+            )
+        else:
+            file_utils.delete_folder(existing_folder["folder_name"])
 
         ctx.conformance_tests_render_attempts += 1
         ctx.fix_attempts = 0
 
@@ -0,0 +1,93 @@
+"""Regenerating a conformance test after the fix attempts run out.
+
+Two things went wrong on the same path. The regeneration branch was taken for any test
+that exhausted its fix attempts, including one belonging to a required module - which
+RenderConformanceTests cannot rebuild coherently, because it writes the replacement under
+the module being rendered while recording the entry against the module the test belongs
+to. And the handler removed the recorded entry with an unguarded `pop`, so a state where
+the entry was already gone ended the render with a bare `KeyError` naming the
+functionality id.
+"""
+
+from unittest.mock import MagicMock
+
+from render_machine.actions.fix_conformance_test import (
+    MAX_CONFORMANCE_TEST_FIX_ATTEMPTS,
+    MAX_CONFORMANCE_TEST_RERENDER_ATTEMPTS,
+    FixConformanceTest,
+)
+from render_machine.render_context import RenderContext
+
+
+def exhausted_context(current_module="inventory_api", testing_module="inventory_api", entry=None):
+    """A conformance loop one attempt short of its limit, with its regeneration budget intact."""
+    render_context = MagicMock()
+    render_context.module_name = current_module
+    render_context.frid_context.frid = "2"
+
+    ctx = render_context.conformance_tests_running_context
+    ctx.fix_attempts = MAX_CONFORMANCE_TEST_FIX_ATTEMPTS - 1
+    ctx.conformance_tests_render_attempts = MAX_CONFORMANCE_TEST_RERENDER_ATTEMPTS - 1
+    ctx.current_testing_module_name = testing_module
+    ctx.current_testing_frid = "2"
+    ctx.get_conformance_tests_json.return_value = {} if entry is None else {"2": entry}
+    return render_context
+
+
+class TestOnlyTheRenderedModulesTestIsRegenerated:
+    def test_the_current_modules_test_is_regenerated(self):
+        render_context = exhausted_context()
+
+        outcome, payload = FixConformanceTest().execute(render_context, None)
+
+        assert outcome == FixConformanceTest.REGENERATE_CONFORMANCE_TESTS_OUTCOME
+        assert payload is None
+        assert render_context.conformance_tests_running_context.regenerating_conformance_tests is True
+
+    def test_a_required_modules_test_fails_the_render_instead(self):
+        """The replacement would be written for the wrong module, so there is nothing to
+        regenerate - the render has failed."""
+        render_context = exhausted_context(current_module="inventory_api", testing_module="store_core")
+
+        outcome, payload = FixConformanceTest().execute(render_context, None)
+
+        assert outcome == FixConformanceTest.LIMIT_EXCEEDED_OUTCOME
+        assert payload["error"]["message"]
+        assert render_context.conformance_tests_running_context.regenerating_conformance_tests is not True
+
+
+class TestRegenerationSurvivesAMissingEntry:
+    @staticmethod
+    def _context_with(entry):
+        context = RenderContext.__new__(RenderContext)
+        ctx = MagicMock()
+        ctx.current_testing_frid = "2"
+        ctx.current_testing_module_name = "store_core"
+        ctx.conformance_tests_render_attempts = 0
+        ctx.get_conformance_tests_json.return_value = {} if entry is None else {"2": entry}
+        context.conformance_tests_running_context = ctx
+        return context, ctx
+
+    def test_a_recorded_entry_is_removed_and_its_folder_deleted(self, monkeypatch):
+        deleted = []
+        monkeypatch.setattr("render_machine.render_context.file_utils.delete_folder", deleted.append)
+        context, ctx = self._context_with({"folder_name": "/tmp/tests/store_core_2"})
+
+        context._handle_test_regeneration()
+
+        assert deleted == ["/tmp/tests/store_core_2"]
+        assert ctx.conformance_tests_render_attempts == 1
+        assert ctx.fix_attempts == 0
+
+    def test_a_missing_entry_does_not_end_the_render(self, monkeypatch):
+        """This raised `KeyError('2')` out of the render, an hour into it, reported to the
+        user as the bare string `'2'`."""
+        deleted = []
+        monkeypatch.setattr("render_machine.render_context.file_utils.delete_folder", deleted.append)
+        context, ctx = self._context_with(None)
+
+        context._handle_test_regeneration()
+
+        assert deleted == []
+        assert ctx.conformance_tests_render_attempts == 1
+        assert ctx.fix_attempts == 0