From b83678ad47df1064e964020550d49a9c789d3ebc Mon Sep 17 00:00:00 2001
From: f3ranmi <ibitoyeferanmi70@gmail.com>
Date: Mon, 5 Jan 2026 19:12:02 +0100
Subject: [PATCH] [testselect] KeyError in equivalence_sets[group] #5577 fix

---
 bugbug/models/testselect.py        | 29 +++++++++++++++++++++++++++++
 http_service/bugbug_http/models.py |  3 ++-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/bugbug/models/testselect.py b/bugbug/models/testselect.py
index bdb2709101..fcf4be64df 100644
--- a/bugbug/models/testselect.py
+++ b/bugbug/models/testselect.py
@@ -311,6 +311,35 @@ def select_configs(
         # Create constraints to ensure at least one task from each set of equivalent
         # groups is selected.
 
+        # Generate equivalence sets for groups that don't exist in the precomputed sets
+        if group not in equivalence_sets:
+            logger.warning(
+                f"Group {group} not found in equivalence sets, generating on-the-fly"
+            )
+            key = test_scheduling.failing_together_key(group)
+            try:
+                failing_together_stats = pickle.loads(failing_together[key])
+            except KeyError:
+                failing_together_stats = {}
+
+            def load_failing_together(
+                config: str,
+            ) -> dict[str, tuple[float, float]]:
+                try:
+                    return failing_together_stats[config]
+                except KeyError:
+                    return {}
+
+            configs = (
+                all_configs_by_group[group]
+                if group in all_configs_by_group
+                else all_configs
+            )
+
+            equivalence_sets[group] = _generate_equivalence_sets(
+                configs, min_redundancy_confidence, load_failing_together, True
+            )
+
         mutually_exclusive = True
         seen = set()
         for equivalence_set in equivalence_sets[group]:
diff --git a/http_service/bugbug_http/models.py b/http_service/bugbug_http/models.py
index 77a73d0c5d..e07d418fd6 100644
--- a/http_service/bugbug_http/models.py
+++ b/http_service/bugbug_http/models.py
@@ -279,7 +279,8 @@ def get_config_specific_groups(config: str) -> str:
             [
                 {"name": group}
                 for group in past_failures_data.all_runnables
-                if any(
+                if group in equivalence_sets
+                and any(
                     equivalence_set == {config}
                     for equivalence_set in equivalence_sets[group]
                 )