Fix cover/remaster/extend failing with HTTP 422 (null params.title)

src/api/cover.rs

@@ -14,10 +14,15 @@ impl SunoClient {
         clip_id: &str,
         model_key: &str,
         tags: Option<&str>,
+        title: Option<&str>,
     ) -> Result<Vec<Clip>, CliError> {
         let mut req = GenerateRequest::new(model_key, "cover");
         req.tags = tags.map(String::from);
         req.cover_clip_id = Some(clip_id.to_string());
+        // v2-web rejects a null `params.title` with HTTP 422, so it must always
+        // be a string. Use the caller's title, else inherit the source clip's
+        // title (matching the web app), else a generic fallback.
+        req.title = Some(self.resolve_title(clip_id, title, "Cover").await);
         self.generate(&req).await
     }
 }

src/api/generate.rs

@@ -19,6 +19,33 @@ impl SunoClient {
         .await
     }
 
+    /// Resolve the title for a clip-derived generation (cover/remaster/extend).
+    /// Prefers an explicit override, then the source clip's own title, then a
+    /// generic fallback. `/api/generate/v2-web/` requires `params.title` to be a
+    /// non-null string, so this never returns an empty value.
+    pub async fn resolve_title(
+        &self,
+        clip_id: &str,
+        override_title: Option<&str>,
+        fallback: &str,
+    ) -> String {
+        if let Some(t) = override_title {
+            let t = t.trim();
+            if !t.is_empty() {
+                return t.to_string();
+            }
+        }
+        if let Ok(clips) = self.get_clips(&[clip_id.to_string()]).await
+            && let Some(c) = clips.into_iter().next()
+        {
+            let t = c.title.trim();
+            if !t.is_empty() {
+                return t.to_string();
+            }
+        }
+        fallback.to_string()
+    }
+
     /// Poll clip status by IDs until all are complete or errored.
     /// "streaming" means still generating — we wait for "complete".
     pub async fn poll_clips(

src/api/remaster.rs

@@ -11,9 +11,13 @@ impl SunoClient {
         &self,
         clip_id: &str,
         remaster_model_key: &str,
+        title: Option<&str>,
     ) -> Result<Vec<Clip>, CliError> {
         let mut req = GenerateRequest::new(remaster_model_key, "remaster");
         req.cover_clip_id = Some(clip_id.to_string());
+        // v2-web rejects a null `params.title` with HTTP 422; always send a
+        // string (caller override, else the source clip's title, else fallback).
+        req.title = Some(self.resolve_title(clip_id, title, "Remaster").await);
         self.generate(&req).await
     }
 }

src/cli.rs

@@ -243,6 +243,10 @@ pub struct ExtendArgs {
     #[arg(long)]
     pub tags: Option<String>,
 
+    /// Title for the new clip (defaults to the source clip's title)
+    #[arg(long)]
+    pub title: Option<String>,
+
     /// Wait for completion
     #[arg(short, long)]
     pub wait: bool,
@@ -267,6 +271,10 @@ pub struct CoverArgs {
     #[arg(long)]
     pub tags: Option<String>,
 
+    /// Title for the cover (defaults to the source clip's title)
+    #[arg(long)]
+    pub title: Option<String>,
+
     /// Model version for the cover
     #[arg(short, long, default_value = "v5.5")]
     pub model: ModelVersion,
@@ -289,6 +297,10 @@ pub struct RemasterArgs {
     #[arg(long, default_value = "v5.5")]
     pub model: RemasterModel,
 
+    /// Title for the remaster (defaults to the source clip's title)
+    #[arg(long)]
+    pub title: Option<String>,
+
     /// Wait for completion
     #[arg(short, long)]
     pub wait: bool,

src/main.rs

@@ -375,13 +375,18 @@ async fn run() -> Result<(), CliError> {
         }
 
         Commands::Extend(args) => {
+            let c = client().await?;
             let mut req = GenerateRequest::new("chirp-fenix", "custom");
             req.prompt = args.lyrics.unwrap_or_default();
             req.tags = args.tags;
+            // v2-web requires a non-null `params.title`.
+            req.title = Some(
+                c.resolve_title(&args.clip_id, args.title.as_deref(), "Extend")
+                    .await,
+            );
             req.continue_clip_id = Some(args.clip_id);
             req.continue_at = Some(args.at);
 
-            let c = client().await?;
             let clips = c.generate(&req).await?;
             handle_generation(&c, clips, args.wait, None, &fmt, cli.quiet).await?;
         }
@@ -400,7 +405,12 @@ async fn run() -> Result<(), CliError> {
             }
             let c = client().await?;
             let clips = c
-                .cover(&args.clip_id, args.model.to_api_key(), args.tags.as_deref())
+                .cover(
+                    &args.clip_id,
+                    args.model.to_api_key(),
+                    args.tags.as_deref(),
+                    args.title.as_deref(),
+                )
                 .await?;
             handle_generation(
                 &c,
@@ -418,7 +428,9 @@ async fn run() -> Result<(), CliError> {
                 eprintln!("Remastering with {}...", args.model.to_api_key());
             }
             let c = client().await?;
-            let clips = c.remaster(&args.clip_id, args.model.to_api_key()).await?;
+            let clips = c
+                .remaster(&args.clip_id, args.model.to_api_key(), args.title.as_deref())
+                .await?;
             handle_generation(
                 &c,
                 clips,