fix: relax canonical model listing for custom providers

Keep strict canonical filtering for builtin/preferred providers, while allowing unknown models for custom/declarative providers. This fixes proxy-backed models disappearing from the picker despite working at runtime.

Use provider_type() for classification in fetch_recommended_models and add focused regression tests for custom-include vs builtin-exclude behavior.

Signed-off-by: Pete Gonzalez <4673363+octogonz@users.noreply.github.com>

Author: octogonz

crates/goose/src/providers/base.rs

@@ -931,6 +931,45 @@ mod tests {
         }
     }
 
+    struct ListingProvider {
+        name: String,
+        provider_type: ProviderType,
+        model_config: ModelConfig,
+        supported_models: Vec<String>,
+    }
+
+    #[async_trait::async_trait]
+    impl Provider for ListingProvider {
+        fn get_name(&self) -> &str {
+            &self.name
+        }
+
+        fn provider_type(&self) -> ProviderType {
+            self.provider_type
+        }
+
+        fn get_model_config(&self) -> ModelConfig {
+            self.model_config.clone()
+        }
+
+        async fn fetch_supported_models(&self) -> Result<Vec<String>, ProviderError> {
+            Ok(self.supported_models.clone())
+        }
+
+        async fn stream(
+            &self,
+            _model_config: &ModelConfig,
+            _session_id: &str,
+            _system: &str,
+            _messages: &[Message],
+            _tools: &[Tool],
+        ) -> Result<MessageStream, ProviderError> {
+            Err(ProviderError::ExecutionError(
+                "stream not implemented for listing tests".to_string(),
+            ))
+        }
+    }
+
     fn create_test_stream(
         items: Vec<String>,
     ) -> impl Stream<Item = Result<(Option<Message>, Option<ProviderUsage>), ProviderError>> {
@@ -1114,4 +1153,30 @@ mod tests {
         assert_eq!(info.output_token_cost, Some(0.00001));
         assert_eq!(info.currency, Some("$".to_string()));
     }
+
+    #[tokio::test]
+    async fn test_fetch_recommended_models_includes_unknown_for_custom_provider() {
+        let provider = ListingProvider {
+            name: "custom-proxy".to_string(),
+            provider_type: ProviderType::Custom,
+            model_config: ModelConfig::new_or_fail("glm-5"),
+            supported_models: vec!["glm-5".to_string()],
+        };
+
+        let recommended = provider.fetch_recommended_models().await.unwrap();
+        assert!(recommended.contains(&"glm-5".to_string()));
+    }
+
+    #[tokio::test]
+    async fn test_fetch_recommended_models_excludes_unknown_for_builtin_provider() {
+        let provider = ListingProvider {
+            name: "openai".to_string(),
+            provider_type: ProviderType::Builtin,
+            model_config: ModelConfig::new_or_fail("gpt-4o"),
+            supported_models: vec!["definitely-unknown-model-id".to_string()],
+        };
+
+        let recommended = provider.fetch_recommended_models().await.unwrap();
+        assert!(recommended.is_empty());
+    }
 }