diff --git a/.github/.copilot-collections.yaml b/.github/.copilot-collections.yaml
index e09312f3a..887b507f0 100644
--- a/.github/.copilot-collections.yaml
+++ b/.github/.copilot-collections.yaml
@@ -4,4 +4,4 @@ copilot:
   version: v0.12.0
   collections:
     - starcraft-core
-    - starcraft-docs
\ No newline at end of file
+    - starcraft-docs
diff --git a/.github/workflows/copilot-collections-update.yaml b/.github/workflows/copilot-collections-update.yaml
index 9d57e3ee6..df28b1aff 100644
--- a/.github/workflows/copilot-collections-update.yaml
+++ b/.github/workflows/copilot-collections-update.yaml
@@ -8,4 +8,4 @@ jobs:
   check-update:
     # Pinned to @main to get the latest logic, but the content version is controlled by .github/.copilot-collections.yaml
     uses: canonical/copilot-collections/.github/workflows/auto_update_collections.yaml@main
-    secrets: inherit
\ No newline at end of file
+    secrets: inherit
diff --git a/charmcraft/extensions/app.py b/charmcraft/extensions/app.py
index 4b61ab04e..39d2f02aa 100644
--- a/charmcraft/extensions/app.py
+++ b/charmcraft/extensions/app.py
@@ -20,6 +20,7 @@
 from pathlib import Path
 from typing import Any
 
+import yaml
 from overrides import override
 
 from ..errors import ExtensionError
@@ -71,6 +72,8 @@
 }
 
 COS_SUBDIRS = {"grafana_dashboards", "loki_alert_rules", "prometheus_alert_rules"}
+PAAS_CONFIG_FILE = "paas-config.yaml"
+JSON_LOGGING_SUPPORTED_FRAMEWORKS = {"fastapi", "flask", "django"}
 
 
 class _AppBase(Extension):
@@ -194,6 +197,34 @@ def _check_input(self) -> None:
                 "Non-optional configuration options can not have default values.\n"
                 f"Please either remove the default value or set optional field to true or remove it for the {', '.join(invalid_non_optionals)} configuration option(s)."
             )
+        self._check_paas_config()
+
+    def _check_paas_config(self) -> None:
+        """Validate ``paas-config.yaml`` syntax and framework logging compatibility."""
+        config_path = self.project_root / PAAS_CONFIG_FILE
+        if not config_path.exists():
+            return
+
+        try:
+            parsed = yaml.safe_load(config_path.read_text(encoding="utf-8"))
+        except yaml.YAMLError as exc:
+            raise ExtensionError(f"invalid YAML in {PAAS_CONFIG_FILE}: {exc}") from exc
+
+        if parsed is None:
+            return
+        if not isinstance(parsed, dict):
+            raise ExtensionError(f"{PAAS_CONFIG_FILE} must contain a top-level mapping")
+
+        framework_logging_format = parsed.get("framework_logging_format")
+        if (
+            isinstance(framework_logging_format, str)
+            and framework_logging_format.lower() == "json"
+            and self.framework not in JSON_LOGGING_SUPPORTED_FRAMEWORKS
+        ):
+            raise ExtensionError(
+                f"framework_logging_format: json in {PAAS_CONFIG_FILE} is not supported "
+                f"for '{self.framework}-framework'"
+            )
 
     def _validate_cos_custom_dir(self) -> None:
         """Validate the custom COS directory if present."""
diff --git a/tests/extensions/test_app.py b/tests/extensions/test_app.py
index 6854ff5eb..17778a1e7 100644
--- a/tests/extensions/test_app.py
+++ b/tests/extensions/test_app.py
@@ -687,6 +687,46 @@ def test_handle_charm_part_adds_part(flask_input_yaml, tmp_path):
     }
 
 
+def test_invalid_paas_config_yaml_fails_pack(flask_input_yaml, tmp_path):
+    (tmp_path / "paas-config.yaml").write_text(
+        "framework_logging_format: [json", encoding="utf-8"
+    )
+
+    with pytest.raises(ExtensionError, match=r"invalid YAML in paas-config.yaml"):
+        extensions.apply_extensions(tmp_path, flask_input_yaml)
+
+
+def test_json_framework_logging_disallowed_framework_fails_pack(tmp_path):
+    go_input_yaml = {
+        "type": "charm",
+        "name": "test-go",
+        "summary": "test summary",
+        "description": "test description",
+        "base": "ubuntu@24.04",
+        "platforms": {
+            "amd64": None,
+        },
+        "extensions": ["go-framework"],
+        "config": NON_OPTIONAL_OPTIONS,
+    }
+    (tmp_path / "paas-config.yaml").write_text(
+        "framework_logging_format: json\n", encoding="utf-8"
+    )
+
+    with pytest.raises(
+        ExtensionError,
+        match=r"framework_logging_format: json in paas-config.yaml is not supported for 'go-framework'",
+    ):
+        extensions.apply_extensions(tmp_path, go_input_yaml)
+
+
+def test_json_framework_logging_supported_framework_passes(flask_input_yaml, tmp_path):
+    (tmp_path / "paas-config.yaml").write_text(
+        "framework_logging_format: json\n", encoding="utf-8"
+    )
+    extensions.apply_extensions(tmp_path, flask_input_yaml)
+
+
 @pytest.mark.parametrize(
     ("input_yaml", "requires", "expected_options"),
     [