diff --git a/conformance/testdata/aggregate/config.yaml b/conformance/testdata/aggregate/config.yaml
new file mode 100644
index 0000000..8345949
--- /dev/null
+++ b/conformance/testdata/aggregate/config.yaml
@@ -0,0 +1,21 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "aggregate"
+variables:
+  - name: "resource"
+    type_name: "map"
+    params:
+      - type_name: "string"
+      - type_name: "dyn"
diff --git a/conformance/testdata/aggregate/policy.yaml b/conformance/testdata/aggregate/policy.yaml
new file mode 100644
index 0000000..6fa760f
--- /dev/null
+++ b/conformance/testdata/aggregate/policy.yaml
@@ -0,0 +1,26 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: aggregate
+rule:
+  aggregate:
+    - condition: "resource.is_pii == true"
+      emit: "'PII'"
+    - condition: "resource.is_confidential == true"
+      emit: "'CONFIDENTIAL'"
+    - condition: "true"
+      rule:
+        match:
+          - condition: "resource.nested_cond == true"
+            output: "'NESTED'"
diff --git a/conformance/testdata/aggregate/tests.yaml b/conformance/testdata/aggregate/tests.yaml
new file mode 100644
index 0000000..1e4a539
--- /dev/null
+++ b/conformance/testdata/aggregate/tests.yaml
@@ -0,0 +1,42 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+description: Aggregate semantic conformance tests
+section:
+  - name: "basic"
+    tests:
+      - name: "all_match_nested_triggered"
+        input:
+          resource:
+            expr: "{'is_pii': true, 'is_confidential': true, 'nested_cond': true}"
+        output:
+          expr: "['PII', 'CONFIDENTIAL', 'NESTED']"
+      - name: "all_match_nested_fallback"
+        input:
+          resource:
+            expr: "{'is_pii': true, 'is_confidential': true, 'nested_cond': false}"
+        output:
+          expr: "['PII', 'CONFIDENTIAL']"
+      - name: "some_match"
+        input:
+          resource:
+            expr: "{'is_pii': true, 'is_confidential': false, 'nested_cond': false}"
+        output:
+          expr: "['PII']"
+      - name: "none_match"
+        input:
+          resource:
+            expr: "{'is_pii': false, 'is_confidential': false, 'nested_cond': false}"
+        output:
+          expr: "[]"
diff --git a/conformance/testdata/aggregate_explicit_list_output/policy.yaml b/conformance/testdata/aggregate_explicit_list_output/policy.yaml
new file mode 100644
index 0000000..e75ef8c
--- /dev/null
+++ b/conformance/testdata/aggregate_explicit_list_output/policy.yaml
@@ -0,0 +1,19 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: aggregate_explicit_list_output
+rule:
+  aggregate:
+    - condition: "true"
+      emit: "['tag1', 'tag2']"
diff --git a/conformance/testdata/aggregate_explicit_list_output/tests.yaml b/conformance/testdata/aggregate_explicit_list_output/tests.yaml
new file mode 100644
index 0000000..b968310
--- /dev/null
+++ b/conformance/testdata/aggregate_explicit_list_output/tests.yaml
@@ -0,0 +1,22 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+description: Explicit list output conformance tests
+section:
+  - name: "basic"
+    tests:
+      - name: "all_match"
+        input: {}
+        output:
+          expr: "[['tag1', 'tag2']]"
diff --git a/conformance/testdata/aggregate_explicit_optional_none/policy.yaml b/conformance/testdata/aggregate_explicit_optional_none/policy.yaml
new file mode 100644
index 0000000..dc6ba7f
--- /dev/null
+++ b/conformance/testdata/aggregate_explicit_optional_none/policy.yaml
@@ -0,0 +1,19 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: aggregate_explicit_optional_none
+rule:
+  aggregate:
+    - condition: "true"
+      emit: "optional.none()"
diff --git a/conformance/testdata/aggregate_explicit_optional_none/tests.yaml b/conformance/testdata/aggregate_explicit_optional_none/tests.yaml
new file mode 100644
index 0000000..d71d854
--- /dev/null
+++ b/conformance/testdata/aggregate_explicit_optional_none/tests.yaml
@@ -0,0 +1,22 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+description: Explicit optional none conformance tests
+section:
+  - name: "basic"
+    tests:
+      - name: "all_match"
+        input: {}
+        output:
+          expr: "[optional.none()]"
diff --git a/conformance/testdata/aggregate_nested_explicit_list_double_wrapping/policy.yaml b/conformance/testdata/aggregate_nested_explicit_list_double_wrapping/policy.yaml
new file mode 100644
index 0000000..bf165c9
--- /dev/null
+++ b/conformance/testdata/aggregate_nested_explicit_list_double_wrapping/policy.yaml
@@ -0,0 +1,21 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: aggregate_nested_explicit_list_double_wrapping
+rule:
+  aggregate:
+    - rule:
+        match:
+          - condition: "true"
+            output: "['tag1', 'tag2']"
diff --git a/conformance/testdata/aggregate_nested_explicit_list_double_wrapping/tests.yaml b/conformance/testdata/aggregate_nested_explicit_list_double_wrapping/tests.yaml
new file mode 100644
index 0000000..2803973
--- /dev/null
+++ b/conformance/testdata/aggregate_nested_explicit_list_double_wrapping/tests.yaml
@@ -0,0 +1,22 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "aggregate_nested_explicit_list_double_wrapping"
+description: "Tests that aggregate policies cleanly support double-wrapped lists when a nested first_match rule returns an explicit list literal"
+sections:
+- name: "compile"
+  tests:
+  - name: "nested_explicit_list"
+    output:
+      value: [["tag1", "tag2"]]
diff --git a/conformance/testdata/aggregate_nested_mixed_semantics/config.yaml b/conformance/testdata/aggregate_nested_mixed_semantics/config.yaml
new file mode 100644
index 0000000..553de54
--- /dev/null
+++ b/conformance/testdata/aggregate_nested_mixed_semantics/config.yaml
@@ -0,0 +1,21 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "aggregate_nested_mixed_semantics"
+variables:
+  - name: "resource"
+    type_name: "map"
+    params:
+      - type_name: "string"
+      - type_name: "dyn"
diff --git a/conformance/testdata/aggregate_nested_mixed_semantics/policy.yaml b/conformance/testdata/aggregate_nested_mixed_semantics/policy.yaml
new file mode 100644
index 0000000..4203ea7
--- /dev/null
+++ b/conformance/testdata/aggregate_nested_mixed_semantics/policy.yaml
@@ -0,0 +1,39 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: document_classification
+rule:
+  aggregate:
+    # PRIVACY CLASSIFICATION BLOCK
+    - condition: "resource.is_privacy_related == true"
+      rule:
+        match:
+          - condition: "resource.is_eu_origin == true"
+            rule:
+              aggregate: # In the EU, we must accumulate ALL applicable sub-tags
+                - condition: "resource.has_pii == true"
+                  rule:
+                    match:
+                      - condition: "resource.has_health_data == true"
+                        output: "'GDPR_SENSITIVE_HEALTH'"
+                      - condition: "resource.has_standard_pii == true"
+                        output: "'GDPR_STANDARD'"
+                - condition: "resource.is_b2c == true"
+                  emit: "'EU_B2C_NOTICE_REQUIRED'"
+          - condition: "resource.is_us_origin == true"
+            output: "'CCPA_APPLIES'"
+
+    # FINANCIAL RETENTION BLOCK
+    - condition: "resource.is_financial_record == true"
+      emit: "'RETAIN_7_YEARS'"
diff --git a/conformance/testdata/aggregate_nested_mixed_semantics/tests.yaml b/conformance/testdata/aggregate_nested_mixed_semantics/tests.yaml
new file mode 100644
index 0000000..42e8731
--- /dev/null
+++ b/conformance/testdata/aggregate_nested_mixed_semantics/tests.yaml
@@ -0,0 +1,77 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+description: Deeply nested document classification conformance tests
+section:
+  - name: "basic"
+    tests:
+      - name: "all_true"
+        input:
+          resource:
+            expr: >
+              {
+                'is_privacy_related': true, 'is_eu_origin': true, 'has_pii': true,
+                'has_health_data': true, 'has_standard_pii': true, 'is_b2c': true,
+                'is_us_origin': true, 'is_financial_record': true
+              }
+        output:
+          expr: "['GDPR_SENSITIVE_HEALTH', 'EU_B2C_NOTICE_REQUIRED', 'RETAIN_7_YEARS']"
+
+      - name: "fallback_in_nested_first_match"
+        input:
+          resource:
+            expr: >
+              {
+                'is_privacy_related': true, 'is_eu_origin': true, 'has_pii': true,
+                'has_health_data': false, 'has_standard_pii': true, 'is_b2c': true,
+                'is_us_origin': true, 'is_financial_record': true
+              }
+        output:
+          expr: "['GDPR_STANDARD', 'EU_B2C_NOTICE_REQUIRED', 'RETAIN_7_YEARS']"
+
+      - name: "propagation_all_fail_to_empty"
+        input:
+          resource:
+            expr: >
+              {
+                'is_privacy_related': true, 'is_eu_origin': true, 'has_pii': true,
+                'has_health_data': false, 'has_standard_pii': false, 'is_b2c': false,
+                'is_us_origin': false, 'is_financial_record': false
+              }
+        output:
+          expr: "[]"
+
+      - name: "propagation_nested_fail_with_outer_fallback"
+        input:
+          resource:
+            expr: >
+              {
+                'is_privacy_related': true, 'is_eu_origin': true, 'has_pii': true,
+                'has_health_data': false, 'has_standard_pii': false, 'is_b2c': false,
+                'is_us_origin': false, 'is_financial_record': true
+              }
+        output:
+          expr: "['RETAIN_7_YEARS']"
+
+      - name: "failed_nested_first_match_all_fail"
+        input:
+          resource:
+            expr: >
+              {
+                'is_privacy_related': true, 'is_eu_origin': true, 'has_pii': true,
+                'has_health_data': false, 'has_standard_pii': false, 'is_b2c': true,
+                'is_us_origin': true, 'is_financial_record': true
+              }
+        output:
+          expr: "['EU_B2C_NOTICE_REQUIRED', 'RETAIN_7_YEARS']"
diff --git a/conformance/testdata/aggregate_shadowed_variables/config.yaml b/conformance/testdata/aggregate_shadowed_variables/config.yaml
new file mode 100644
index 0000000..ecab9d2
--- /dev/null
+++ b/conformance/testdata/aggregate_shadowed_variables/config.yaml
@@ -0,0 +1,21 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "aggregate_shadowed_variables"
+variables:
+  - name: "resource"
+    type_name: "map"
+    params:
+      - type_name: "string"
+      - type_name: "dyn"
diff --git a/conformance/testdata/aggregate_shadowed_variables/policy.yaml b/conformance/testdata/aggregate_shadowed_variables/policy.yaml
new file mode 100644
index 0000000..2785c37
--- /dev/null
+++ b/conformance/testdata/aggregate_shadowed_variables/policy.yaml
@@ -0,0 +1,30 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: aggregate_shadowed_variables
+rule:
+  variables:
+    - name: "x"
+      expression: "10"
+  aggregate:
+    - condition: "resource.cond1 == true"
+      emit: "variables.x"
+    - condition: "resource.cond2 == true"
+      rule:
+        variables:
+          - name: "x"
+            expression: "20"
+        match:
+          - condition: "true"
+            output: "variables.x"
diff --git a/conformance/testdata/aggregate_shadowed_variables/tests.yaml b/conformance/testdata/aggregate_shadowed_variables/tests.yaml
new file mode 100644
index 0000000..25a41dc
--- /dev/null
+++ b/conformance/testdata/aggregate_shadowed_variables/tests.yaml
@@ -0,0 +1,24 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+description: Shadowed variables conformance tests
+section:
+  - name: "basic"
+    tests:
+      - name: "shadowed_in_nested_rule"
+        input:
+          resource:
+            expr: "{'cond1': true, 'cond2': true}"
+        output:
+          expr: "[10, 20]"
diff --git a/conformance/testdata/compile_errors/aggregate_false_condition/policy.yaml b/conformance/testdata/compile_errors/aggregate_false_condition/policy.yaml
new file mode 100644
index 0000000..a33d8c0
--- /dev/null
+++ b/conformance/testdata/compile_errors/aggregate_false_condition/policy.yaml
@@ -0,0 +1,19 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: aggregate_false_condition
+rule:
+  aggregate:
+    - condition: "false"
+      emit: "'FALSE'"
diff --git a/conformance/testdata/compile_errors/aggregate_false_condition/tests.yaml b/conformance/testdata/compile_errors/aggregate_false_condition/tests.yaml
new file mode 100644
index 0000000..5c35d51
--- /dev/null
+++ b/conformance/testdata/compile_errors/aggregate_false_condition/tests.yaml
@@ -0,0 +1,23 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "aggregate_false_condition"
+description: "Tests for false condition in aggregate policy"
+sections:
+- name: "compile"
+  tests:
+  - name: "false_condition"
+    output:
+      error_set:
+      - "condition is always false"
diff --git a/conformance/testdata/compile_errors/aggregate_heterogeneous_outputs/policy.yaml b/conformance/testdata/compile_errors/aggregate_heterogeneous_outputs/policy.yaml
new file mode 100644
index 0000000..b88dac9
--- /dev/null
+++ b/conformance/testdata/compile_errors/aggregate_heterogeneous_outputs/policy.yaml
@@ -0,0 +1,23 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: aggregate_heterogeneous_outputs
+rule:
+  aggregate:
+    - condition: "true"
+      emit: "'PII'"
+    - condition: "true"
+      emit: "403"
+    - condition: "true"
+      emit: "{'reason': 'blocked'}"
diff --git a/conformance/testdata/compile_errors/aggregate_heterogeneous_outputs/tests.yaml b/conformance/testdata/compile_errors/aggregate_heterogeneous_outputs/tests.yaml
new file mode 100644
index 0000000..1dcf688
--- /dev/null
+++ b/conformance/testdata/compile_errors/aggregate_heterogeneous_outputs/tests.yaml
@@ -0,0 +1,23 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "aggregate_heterogeneous_outputs"
+description: "Tests for heterogeneous outputs in aggregate policy"
+sections:
+- name: "compile"
+  tests:
+  - name: "incompatible_types"
+    output:
+      error_set:
+      - "incompatible output types: block has output type map(string, string), but previous outputs have type int"
diff --git a/conformance/testdata/compile_errors/aggregate_nested_mixed_semantics_error/config.yaml b/conformance/testdata/compile_errors/aggregate_nested_mixed_semantics_error/config.yaml
new file mode 100644
index 0000000..bb0f3aa
--- /dev/null
+++ b/conformance/testdata/compile_errors/aggregate_nested_mixed_semantics_error/config.yaml
@@ -0,0 +1,21 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+variables:
+  - name: cond1
+    type:
+      type_name: "bool"
+  - name: cond2
+    type:
+      type_name: "bool"
diff --git a/conformance/testdata/compile_errors/aggregate_nested_mixed_semantics_error/policy.yaml b/conformance/testdata/compile_errors/aggregate_nested_mixed_semantics_error/policy.yaml
new file mode 100644
index 0000000..8c88605
--- /dev/null
+++ b/conformance/testdata/compile_errors/aggregate_nested_mixed_semantics_error/policy.yaml
@@ -0,0 +1,23 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: aggregate_nested_mixed_semantics_error
+rule:
+  aggregate:
+    - rule:
+        match:
+          - condition: "cond1"
+            output: "'PII'"
+          - condition: "cond2"
+            output: "403"
diff --git a/conformance/testdata/compile_errors/aggregate_nested_mixed_semantics_error/tests.yaml b/conformance/testdata/compile_errors/aggregate_nested_mixed_semantics_error/tests.yaml
new file mode 100644
index 0000000..a04ce37
--- /dev/null
+++ b/conformance/testdata/compile_errors/aggregate_nested_mixed_semantics_error/tests.yaml
@@ -0,0 +1,23 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "aggregate_nested_mixed_semantics_error"
+description: "Tests that nested first_match subrule under an aggregate outer rule correctly formats its type mismatch errors on raw unwrapped types instead of leaked list wrapper"
+sections:
+- name: "compile"
+  tests:
+  - name: "mixed_semantics_type_error"
+    output:
+      error_set:
+      - "incompatible output types: block has output type int, but previous outputs have type string"
diff --git a/conformance/testdata/compile_errors/aggregate_unreachable_in_nested_first_match/config.yaml b/conformance/testdata/compile_errors/aggregate_unreachable_in_nested_first_match/config.yaml
new file mode 100644
index 0000000..04399fe
--- /dev/null
+++ b/conformance/testdata/compile_errors/aggregate_unreachable_in_nested_first_match/config.yaml
@@ -0,0 +1,21 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "aggregate_unreachable_in_nested_first_match"
+variables:
+  - name: "resource"
+    type_name: "map"
+    params:
+      - type_name: "string"
+      - type_name: "dyn"
diff --git a/conformance/testdata/compile_errors/aggregate_unreachable_in_nested_first_match/policy.yaml b/conformance/testdata/compile_errors/aggregate_unreachable_in_nested_first_match/policy.yaml
new file mode 100644
index 0000000..49ddb7f
--- /dev/null
+++ b/conformance/testdata/compile_errors/aggregate_unreachable_in_nested_first_match/policy.yaml
@@ -0,0 +1,24 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: aggregate_unreachable_in_nested_first_match
+rule:
+  aggregate:
+    - condition: "true"
+      rule:
+        match:
+          - condition: "true"
+            output: "'PII'"
+          - condition: "resource.is_admin == true"
+            output: "'ADMIN'"
diff --git a/conformance/testdata/compile_errors/aggregate_unreachable_in_nested_first_match/tests.yaml b/conformance/testdata/compile_errors/aggregate_unreachable_in_nested_first_match/tests.yaml
new file mode 100644
index 0000000..3352795
--- /dev/null
+++ b/conformance/testdata/compile_errors/aggregate_unreachable_in_nested_first_match/tests.yaml
@@ -0,0 +1,24 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "aggregate_unreachable_in_nested_first_match"
+description: "Tests for unreachable matches inside nested first_match subrule of aggregate policy"
+sections:
+- name: "compile"
+  tests:
+  - name: "unreachable_match"
+    output:
+      error_set:
+      - "match creates unreachable outputs"
+
diff --git a/conformance/testdata/compile_errors/unreachable_under_unconditional_aggregate_subrule/policy.yaml b/conformance/testdata/compile_errors/unreachable_under_unconditional_aggregate_subrule/policy.yaml
new file mode 100644
index 0000000..0ba59c1
--- /dev/null
+++ b/conformance/testdata/compile_errors/unreachable_under_unconditional_aggregate_subrule/policy.yaml
@@ -0,0 +1,24 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: unreachable_under_unconditional_aggregate_subrule
+rule:
+  match:
+    - condition: "true"
+      rule:
+        aggregate:
+          - condition: "1 == 2"
+            emit: "'ADMIN'"
+    - condition: "true"
+      output: "['FALLBACK']"
diff --git a/conformance/testdata/compile_errors/unreachable_under_unconditional_aggregate_subrule/tests.yaml b/conformance/testdata/compile_errors/unreachable_under_unconditional_aggregate_subrule/tests.yaml
new file mode 100644
index 0000000..3e7cd72
--- /dev/null
+++ b/conformance/testdata/compile_errors/unreachable_under_unconditional_aggregate_subrule/tests.yaml
@@ -0,0 +1,23 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "unreachable_under_unconditional_aggregate_subrule"
+description: "Tests that dead code is flagged when a first_match rule has an unconditional aggregate subrule followed by another match"
+sections:
+- name: "compile"
+  tests:
+  - name: "unreachable_match"
+    output:
+      error_set:
+      - "rule creates unreachable outputs"
diff --git a/conformance/testdata/first_match_nested_aggregate/config.yaml b/conformance/testdata/first_match_nested_aggregate/config.yaml
new file mode 100644
index 0000000..c9b688b
--- /dev/null
+++ b/conformance/testdata/first_match_nested_aggregate/config.yaml
@@ -0,0 +1,24 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+variables:
+  - name: cond1
+    type:
+      type_name: "bool"
+  - name: cond2
+    type:
+      type_name: "bool"
+  - name: cond3
+    type:
+      type_name: "bool"
diff --git a/conformance/testdata/first_match_nested_aggregate/policy.yaml b/conformance/testdata/first_match_nested_aggregate/policy.yaml
new file mode 100644
index 0000000..8db0ca0
--- /dev/null
+++ b/conformance/testdata/first_match_nested_aggregate/policy.yaml
@@ -0,0 +1,26 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: first_match_nested_aggregate
+rule:
+  match:
+    - condition: "cond1"
+      rule:
+        aggregate:
+          - condition: "cond2"
+            emit: "'A'"
+          - condition: "cond3"
+            emit: "'B'"
+    - condition: "true"
+      output: "['FALLBACK']"
diff --git a/conformance/testdata/first_match_nested_aggregate/tests.yaml b/conformance/testdata/first_match_nested_aggregate/tests.yaml
new file mode 100644
index 0000000..8cb47df
--- /dev/null
+++ b/conformance/testdata/first_match_nested_aggregate/tests.yaml
@@ -0,0 +1,48 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+description: Bidirectional scoping conformance tests nesting aggregate inside first_match parent
+section:
+  - name: "basic"
+    tests:
+      - name: "all_true"
+        input:
+          cond1:
+            value: true
+          cond2:
+            value: true
+          cond3:
+            value: true
+        output:
+          value: ["A", "B"]
+      - name: "fallback_outer"
+        input:
+          cond1:
+            value: false
+          cond2:
+            value: true
+          cond3:
+            value: true
+        output:
+          value: ["FALLBACK"]
+      - name: "nested_failed_to_empty"
+        input:
+          cond1:
+            value: true
+          cond2:
+            value: false
+          cond3:
+            value: false
+        output:
+          value: []