Replace model system with specific GPT-4.1 family variants (#58)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: oleander <220827+oleander@users.noreply.github.com>

Author: Copilot

src/commit.rs

@@ -234,7 +234,7 @@ mod tests {
     let result = generate(
       "diff --git a/test.txt b/test.txt\n+Hello World".to_string(),
       1024,
-      Model::GPT4oMini,
+      Model::GPT41Mini,
       Some(&settings)
     )
     .await;
@@ -268,7 +268,7 @@ mod tests {
     let result = generate(
       "diff --git a/test.txt b/test.txt\n+Hello World".to_string(),
       1024,
-      Model::GPT4oMini,
+      Model::GPT41Mini,
       Some(&settings)
     )
     .await;

src/config.rs

@@ -12,7 +12,7 @@ use console::Emoji;
 const DEFAULT_TIMEOUT: i64 = 30;
 const DEFAULT_MAX_COMMIT_LENGTH: i64 = 72;
 const DEFAULT_MAX_TOKENS: i64 = 2024;
-const DEFAULT_MODEL: &str = "gpt-4o-mini";
+const DEFAULT_MODEL: &str = "gpt-4.1"; // Matches Model::default()
 const DEFAULT_API_KEY: &str = "<PLACE HOLDER FOR YOUR API KEY>";
 
 #[derive(Debug, Default, Deserialize, PartialEq, Eq, Serialize)]

src/model.rs

@@ -18,26 +18,26 @@ use crate::config::AppConfig;
 static TOKENIZER: OnceLock<CoreBPE> = OnceLock::new();
 
 // Model identifiers - using screaming case for constants
-const MODEL_GPT4: &str = "gpt-4";
-const MODEL_GPT4_OPTIMIZED: &str = "gpt-4o";
-const MODEL_GPT4_MINI: &str = "gpt-4o-mini";
 const MODEL_GPT4_1: &str = "gpt-4.1";
+const MODEL_GPT4_1_MINI: &str = "gpt-4.1-mini";
+const MODEL_GPT4_1_NANO: &str = "gpt-4.1-nano";
+const MODEL_GPT4_5: &str = "gpt-4.5";
 // TODO: Get this from config.rs or a shared constants module
 const DEFAULT_MODEL_NAME: &str = "gpt-4.1";
 
 /// Represents the available AI models for commit message generation.
 /// Each model has different capabilities and token limits.
 #[derive(Debug, PartialEq, Eq, Hash, Copy, Clone, Serialize, Deserialize, Default)]
 pub enum Model {
-  /// Standard GPT-4 model
-  GPT4,
-  /// Optimized GPT-4 model for better performance
-  GPT4o,
-  /// Mini version of optimized GPT-4 for faster processing
-  GPT4oMini,
   /// Default model - GPT-4.1 latest version
   #[default]
-  GPT41
+  GPT41,
+  /// Mini version of GPT-4.1 for faster processing
+  GPT41Mini,
+  /// Nano version of GPT-4.1 for very fast processing
+  GPT41Nano,
+  /// GPT-4.5 model for advanced capabilities
+  GPT45
 }
 
 impl Model {
@@ -59,10 +59,7 @@ impl Model {
 
     // Always use the proper tokenizer for accurate counts
     // We cannot afford to underestimate tokens as it may cause API failures
-    let tokenizer = TOKENIZER.get_or_init(|| {
-      let model_str: &str = self.into();
-      get_tokenizer(model_str)
-    });
+    let tokenizer = TOKENIZER.get_or_init(|| get_tokenizer(self.as_ref()));
 
     // Use direct tokenization for accurate token count
     let tokens = tokenizer.encode_ordinary(text);
@@ -75,8 +72,7 @@ impl Model {
   /// * `usize` - The maximum number of tokens the model can process
   pub fn context_size(&self) -> usize {
     profile!("Get context size");
-    let model_str: &str = self.into();
-    get_context_size(model_str)
+    get_context_size(self.as_ref())
   }
 
   /// Truncates the given text to fit within the specified token limit.
@@ -167,41 +163,80 @@ impl Model {
   }
 }
 
-impl From<&Model> for &str {
-  fn from(model: &Model) -> Self {
-    match model {
-      Model::GPT4o => MODEL_GPT4_OPTIMIZED,
-      Model::GPT4 => MODEL_GPT4,
-      Model::GPT4oMini => MODEL_GPT4_MINI,
-      Model::GPT41 => MODEL_GPT4_1
+impl AsRef<str> for Model {
+  fn as_ref(&self) -> &str {
+    match self {
+      Model::GPT41 => MODEL_GPT4_1,
+      Model::GPT41Mini => MODEL_GPT4_1_MINI,
+      Model::GPT41Nano => MODEL_GPT4_1_NANO,
+      Model::GPT45 => MODEL_GPT4_5
     }
   }
 }
 
+// Keep conversion to String for cases that need owned strings
+impl From<&Model> for String {
+  fn from(model: &Model) -> Self {
+    model.as_ref().to_string()
+  }
+}
+
+// Keep the old impl for backwards compatibility where possible
+impl Model {
+  pub fn as_str(&self) -> &str {
+    self.as_ref()
+  }
+}
+
 impl FromStr for Model {
   type Err = anyhow::Error;
 
   fn from_str(s: &str) -> Result<Self> {
-    match s.trim().to_lowercase().as_str() {
-      "gpt-4o" => Ok(Model::GPT4o),
-      "gpt-4" => Ok(Model::GPT4),
-      "gpt-4o-mini" => Ok(Model::GPT4oMini),
+    let normalized = s.trim().to_lowercase();
+    match normalized.as_str() {
       "gpt-4.1" => Ok(Model::GPT41),
-      model => bail!("Invalid model name: {}", model)
+      "gpt-4.1-mini" => Ok(Model::GPT41Mini),
+      "gpt-4.1-nano" => Ok(Model::GPT41Nano),
+      "gpt-4.5" => Ok(Model::GPT45),
+      // Backward compatibility for deprecated models - map to closest GPT-4.1 equivalent
+      "gpt-4" | "gpt-4o" => {
+        log::warn!(
+          "Model '{}' is deprecated. Mapping to 'gpt-4.1'. \
+          Please update your configuration with: git ai config set model gpt-4.1",
+          s
+        );
+        Ok(Model::GPT41)
+      }
+      "gpt-4o-mini" | "gpt-3.5-turbo" => {
+        log::warn!(
+          "Model '{}' is deprecated. Mapping to 'gpt-4.1-mini'. \
+          Please update your configuration with: git ai config set model gpt-4.1-mini",
+          s
+        );
+        Ok(Model::GPT41Mini)
+      }
+      model =>
+        bail!(
+          "Invalid model name: '{}'. Supported models: gpt-4.1, gpt-4.1-mini, gpt-4.1-nano, gpt-4.5",
+          model
+        ),
     }
   }
 }
 
 impl Display for Model {
   fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    write!(f, "{}", <&str>::from(self))
+    write!(f, "{}", self.as_ref())
   }
 }
 
 // Implement conversion from string types to Model with fallback to default
 impl From<&str> for Model {
   fn from(s: &str) -> Self {
-    s.parse().unwrap_or_default()
+    s.parse().unwrap_or_else(|e| {
+      log::error!("Failed to parse model '{}': {}. Falling back to default model 'gpt-4.1'.", s, e);
+      Model::default()
+    })
   }
 }
 

src/openai.rs

@@ -37,7 +37,7 @@ pub async fn generate_commit_message(diff: &str) -> Result<String> {
   if let Ok(api_key) = std::env::var("OPENAI_API_KEY") {
     if !api_key.is_empty() {
       // Use the commit function directly without parsing
-      match commit::generate(diff.to_string(), 256, Model::GPT4oMini, None).await {
+      match commit::generate(diff.to_string(), 256, Model::GPT41Mini, None).await {
         Ok(response) => return Ok(response.response.trim().to_string()),
         Err(e) => {
           log::warn!("Direct generation failed, falling back to local: {e}");