feat(workflow): Expected instance_ids format (no spaces) (#2502)

Co-authored-by: openhands <openhands@all-hands.dev>

Author: VascoSch92

.github/workflows/run-eval.yml

@@ -61,7 +61,10 @@ on:
                 default: main
                 type: string
             instance_ids:
-                description: Comma-separated instance IDs to evaluate (optional, overrides eval_limit for supported benchmarks)
+                description: >-
+                    Comma-separated instance IDs to evaluate (no spaces).
+                    Example: "django__django-11583,django__django-12345".
+                    Leave empty to evaluate all instances up to eval_limit.
                 required: false
                 default: ''
             num_infer_workers:
@@ -188,6 +191,17 @@ jobs:
                     exit 1
                   fi
 
+            - name: Validate instance_ids (no spaces allowed)
+              if: github.event_name == 'workflow_dispatch' && github.event.inputs.instance_ids != ''
+              run: |
+                  INSTANCE_IDS="${{ github.event.inputs.instance_ids }}"
+                  if [[ "$INSTANCE_IDS" =~ [[:space:]] ]]; then
+                    echo "::error::instance_ids must not contain spaces. Use comma-separated values without spaces."
+                    echo "Got: '$INSTANCE_IDS'"
+                    echo "Example: 'django__django-11583,django__django-12345'"
+                    exit 1
+                  fi
+
             - name: Validate SDK reference (semantic version check)
               if: github.event_name == 'workflow_dispatch'
               env: