diff --git a/mistralrs-core/src/pipeline/chat_template.rs b/mistralrs-core/src/pipeline/chat_template.rs
index 943d353e52..330512a2ce 100644
--- a/mistralrs-core/src/pipeline/chat_template.rs
+++ b/mistralrs-core/src/pipeline/chat_template.rs
@@ -114,29 +114,33 @@ pub fn calculate_eos_tokens(
     }
 
     if let Some(gen_conf) = gen_conf {
-        let ids = match gen_conf.eos_token_id {
-            Either::Left(id) => vec![id],
-            Either::Right(ids) => ids,
-        };
-        for id in ids {
-            let s = tokenizer
-                .decode(&[id], false)
-                .unwrap_or_else(|_| panic!("Unable to decode id {id})"));
-            if !eos_tok_ids.contains(&s) {
-                eos_tok_ids.push(s);
+        if let Some(eos_field) = gen_conf.eos_token_id {
+            let ids = match eos_field {
+                Either::Left(id) => vec![id],
+                Either::Right(ids) => ids,
+            };
+            for id in ids {
+                let s = tokenizer
+                    .decode(&[id], false)
+                    .unwrap_or_else(|_| panic!("Unable to decode id {id})"));
+                if !eos_tok_ids.contains(&s) {
+                    eos_tok_ids.push(s);
+                }
             }
         }
 
-        let ids = match gen_conf.bos_token_id {
-            Either::Left(id) => vec![id],
-            Either::Right(ids) => ids,
-        };
-        for id in ids {
-            let s = tokenizer
-                .decode(&[id], false)
-                .unwrap_or_else(|_| panic!("Unable to decode id {id})"));
-            if !bos_tok_ids.contains(&s) {
-                bos_tok_ids.push(s);
+        if let Some(bos_field) = gen_conf.bos_token_id {
+            let ids = match bos_field {
+                Either::Left(id) => vec![id],
+                Either::Right(ids) => ids,
+            };
+            for id in ids {
+                let s = tokenizer
+                    .decode(&[id], false)
+                    .unwrap_or_else(|_| panic!("Unable to decode id {id})"));
+                if !bos_tok_ids.contains(&s) {
+                    bos_tok_ids.push(s);
+                }
             }
         }
     }
@@ -176,10 +180,10 @@ pub fn calculate_eos_tokens(
 #[allow(dead_code)]
 #[derive(Debug, Deserialize)]
 pub struct GenerationConfig {
-    #[serde(with = "either::serde_untagged")]
-    bos_token_id: Either<u32, Vec<u32>>,
-    #[serde(with = "either::serde_untagged")]
-    eos_token_id: Either<u32, Vec<u32>>,
+    #[serde(with = "either::serde_untagged_optional")]
+    bos_token_id: Option<Either<u32, Vec<u32>>>,
+    #[serde(with = "either::serde_untagged_optional")]
+    eos_token_id: Option<Either<u32, Vec<u32>>>,
 }
 
 fn tojson(value: Value, kwargs: Kwargs) -> Result<Value, Error> {
diff --git a/mistralrs-core/src/pipeline/ggml.rs b/mistralrs-core/src/pipeline/ggml.rs
index d53fd31fdd..2becd30776 100644
--- a/mistralrs-core/src/pipeline/ggml.rs
+++ b/mistralrs-core/src/pipeline/ggml.rs
@@ -343,10 +343,9 @@ impl Loader for GGMLLoader {
         };
 
         let tokenizer = get_tokenizer(paths.get_tokenizer_filename(), None)?;
-        let gen_conf: Option<GenerationConfig> = paths.get_gen_conf_filename().map(|f| {
-            serde_json::from_str(&fs::read_to_string(f).unwrap())
-                .expect("bos_token_id/eos_token_id missing in generation_config.json")
-        });
+        let gen_conf: Option<GenerationConfig> = paths
+            .get_gen_conf_filename()
+            .map(|f| serde_json::from_str(&fs::read_to_string(f).unwrap()).unwrap());
         let chat_template_explicit = paths
             .get_chat_template_explicit()
             .as_ref()
diff --git a/mistralrs-core/src/pipeline/gguf.rs b/mistralrs-core/src/pipeline/gguf.rs
index 3957c6e9d1..fe2cc6b87c 100644
--- a/mistralrs-core/src/pipeline/gguf.rs
+++ b/mistralrs-core/src/pipeline/gguf.rs
@@ -489,10 +489,9 @@ impl Loader for GGUFLoader {
             (None, None)
         };
 
-        let gen_conf: Option<GenerationConfig> = paths.get_gen_conf_filename().map(|f| {
-            serde_json::from_str(&fs::read_to_string(f).unwrap())
-                .expect("bos_token_id/eos_token_id missing in generation_config.json")
-        });
+        let gen_conf: Option<GenerationConfig> = paths
+            .get_gen_conf_filename()
+            .map(|f| serde_json::from_str(&fs::read_to_string(f).unwrap()).unwrap());
         let chat_template_explicit = paths
             .get_chat_template_explicit()
             .as_ref()
diff --git a/mistralrs-core/src/pipeline/vision.rs b/mistralrs-core/src/pipeline/vision.rs
index 2c8733a73c..bf82d2bc85 100644
--- a/mistralrs-core/src/pipeline/vision.rs
+++ b/mistralrs-core/src/pipeline/vision.rs
@@ -539,10 +539,9 @@ impl Loader for VisionLoader {
             Some(processor.get_special_tokens()),
         )?;
 
-        let gen_conf: Option<GenerationConfig> = paths.get_gen_conf_filename().map(|f| {
-            serde_json::from_str(&fs::read_to_string(f).unwrap())
-                .expect("bos_token_id/eos_token_id missing in generation_config.json")
-        });
+        let gen_conf: Option<GenerationConfig> = paths
+            .get_gen_conf_filename()
+            .map(|f| serde_json::from_str(&fs::read_to_string(f).unwrap()).unwrap());
         let chat_template_explicit = paths
             .get_chat_template_explicit()
             .as_ref()