diff --git a/codex-rs/core/src/client_common.rs b/codex-rs/core/src/client_common.rs
index dda69a7e..0d634165 100644
--- a/codex-rs/core/src/client_common.rs
+++ b/codex-rs/core/src/client_common.rs
@@ -41,8 +41,9 @@ impl Prompt {
             .unwrap_or(model.base_instructions.deref());
         let mut sections: Vec<&str> = vec![base];
 
-        // When there are no custom instructions, add apply_patch_tool_instructions if either:
-        // - the model needs special instructions (4.1), or
+        // When there are no custom instructions, add apply_patch_tool_instructions if:
+        // - the model needs special instructions (4.1)
+        // AND
         // - there is no apply_patch tool present
         let is_apply_patch_tool_present = self.tools.iter().any(|tool| match tool {
             OpenAiTool::Function(f) => f.name == "apply_patch",
@@ -50,7 +51,8 @@ impl Prompt {
             _ => false,
         });
         if self.base_instructions_override.is_none()
-            && (model.needs_special_apply_patch_instructions || !is_apply_patch_tool_present)
+            && model.needs_special_apply_patch_instructions
+            && !is_apply_patch_tool_present
         {
             sections.push(APPLY_PATCH_TOOL_INSTRUCTIONS);
         }
@@ -174,22 +176,64 @@ impl Stream for ResponseStream {
 #[cfg(test)]
 mod tests {
     use crate::model_family::find_family_for_model;
+    use pretty_assertions::assert_eq;
 
     use super::*;
 
+    struct InstructionsTestCase {
+        pub slug: &'static str,
+        pub expects_apply_patch_instructions: bool,
+    }
     #[test]
     fn get_full_instructions_no_user_content() {
         let prompt = Prompt {
             ..Default::default()
         };
-        let model_family = find_family_for_model("gpt-4.1").expect("known model slug");
+        let test_cases = vec![
+            InstructionsTestCase {
+                slug: "gpt-3.5",
+                expects_apply_patch_instructions: true,
+            },
+            InstructionsTestCase {
+                slug: "gpt-4.1",
+                expects_apply_patch_instructions: true,
+            },
+            InstructionsTestCase {
+                slug: "gpt-4o",
+                expects_apply_patch_instructions: true,
+            },
+            InstructionsTestCase {
+                slug: "gpt-5",
+                expects_apply_patch_instructions: true,
+            },
+            InstructionsTestCase {
+                slug: "codex-mini-latest",
+                expects_apply_patch_instructions: true,
+            },
+            InstructionsTestCase {
+                slug: "gpt-oss:120b",
+                expects_apply_patch_instructions: false,
+            },
+            InstructionsTestCase {
+                slug: "swiftfox",
+                expects_apply_patch_instructions: false,
+            },
+        ];
+        for test_case in test_cases {
+            let model_family = find_family_for_model(test_case.slug).expect("known model slug");
+            let expected = if test_case.expects_apply_patch_instructions {
+                format!(
+                    "{}\n{}",
+                    model_family.clone().base_instructions,
+                    APPLY_PATCH_TOOL_INSTRUCTIONS
+                )
+            } else {
+                model_family.clone().base_instructions
+            };
 
-        let expected = format!(
-            "{}\n{}",
-            model_family.base_instructions, APPLY_PATCH_TOOL_INSTRUCTIONS
-        );
-        let full = prompt.get_full_instructions(&model_family);
-        assert_eq!(full, expected);
+            let full = prompt.get_full_instructions(&model_family);
+            assert_eq!(full, expected);
+        }
     }
 
     #[test]
diff --git a/codex-rs/core/src/model_family.rs b/codex-rs/core/src/model_family.rs
index 93ab947e..d3a5d005 100644
--- a/codex-rs/core/src/model_family.rs
+++ b/codex-rs/core/src/model_family.rs
@@ -66,23 +66,6 @@ macro_rules! model_family {
     }};
 }
 
-macro_rules! simple_model_family {
-    (
-        $slug:expr, $family:expr
-    ) => {{
-        Some(ModelFamily {
-            slug: $slug.to_string(),
-            family: $family.to_string(),
-            needs_special_apply_patch_instructions: false,
-            supports_reasoning_summaries: false,
-            reasoning_summary_format: ReasoningSummaryFormat::None,
-            uses_local_shell_tool: false,
-            apply_patch_tool_type: None,
-            base_instructions: BASE_INSTRUCTIONS.to_string(),
-        })
-    }};
-}
-
 /// Returns a `ModelFamily` for the given model slug, or `None` if the slug
 /// does not match any known model family.
 pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
@@ -90,17 +73,20 @@ pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
         model_family!(
             slug, "o3",
             supports_reasoning_summaries: true,
+            needs_special_apply_patch_instructions: true,
         )
     } else if slug.starts_with("o4-mini") {
         model_family!(
             slug, "o4-mini",
             supports_reasoning_summaries: true,
+            needs_special_apply_patch_instructions: true,
         )
     } else if slug.starts_with("codex-mini-latest") {
         model_family!(
             slug, "codex-mini-latest",
             supports_reasoning_summaries: true,
             uses_local_shell_tool: true,
+            needs_special_apply_patch_instructions: true,
         )
     } else if slug.starts_with("gpt-4.1") {
         model_family!(
@@ -110,26 +96,21 @@ pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
     } else if slug.starts_with("gpt-oss") || slug.starts_with("openai/gpt-oss") {
         model_family!(slug, "gpt-oss", apply_patch_tool_type: Some(ApplyPatchToolType::Function))
     } else if slug.starts_with("gpt-4o") {
-        simple_model_family!(slug, "gpt-4o")
+        model_family!(slug, "gpt-4o", needs_special_apply_patch_instructions: true)
     } else if slug.starts_with("gpt-3.5") {
-        simple_model_family!(slug, "gpt-3.5")
-    } else if slug.starts_with("codex-") {
+        model_family!(slug, "gpt-3.5", needs_special_apply_patch_instructions: true)
+    } else if slug.starts_with("codex-") || slug.starts_with("swiftfox") {
         model_family!(
             slug, slug,
             supports_reasoning_summaries: true,
             reasoning_summary_format: ReasoningSummaryFormat::Experimental,
+            base_instructions: SWIFTFOX_INSTRUCTIONS.to_string(),
         )
     } else if slug.starts_with("gpt-5") {
         model_family!(
             slug, "gpt-5",
             supports_reasoning_summaries: true,
-        )
-    } else if slug.starts_with("swiftfox") {
-        model_family!(
-            slug, "swiftfox",
-            supports_reasoning_summaries: true,
-            reasoning_summary_format: ReasoningSummaryFormat::Experimental,
-            base_instructions: SWIFTFOX_INSTRUCTIONS.to_string(),
+            needs_special_apply_patch_instructions: true,
         )
     } else {
         None