fix: sbx mixins must be passed in directories, not as files and the files must be named spec.yaml per new sbx version

src/config/mod.rs

@@ -147,6 +147,7 @@ const SBX_KIT_DIR_NAME: &str = "sbx-kit";
 const SBX_KIT_HASH_FILE: &str = "kit.sha256";
 const SBX_MIXIN_FILE_NAME: &str = "sbx-mixin.yaml";
 const SBX_VAULT_MIXINS_DIR_NAME: &str = "sbx-vault-mixins";
+const SBX_MIXIN_KITS_DIR_NAME: &str = "sbx-mixin-kits";
 const GIT_DIR_NAME: &str = ".git";
 const GITIGNORE_FILE_NAME: &str = ".gitignore";
 const DEFAULT_VISIBLE_TOOLS: [&str; 18] = [

src/config/paths.rs

@@ -4,8 +4,8 @@ use super::{
     ENV_FILE_NAME, FUNCTIONS_BIN_DIR_NAME, FUNCTIONS_DIR_NAME, GLOBAL_TOOLS_DIR_NAME,
     GLOBAL_TOOLS_UTILS_DIR_NAME, MACROS_DIR_NAME, MCP_FILE_NAME, MEMORY_DIR_NAME,
     MEMORY_INDEX_FILE_NAME, ModelsOverride, RAGS_DIR_NAME, ROLES_DIR_NAME, SBX_KIT_DIR_NAME,
-    SBX_KIT_HASH_FILE, SBX_MIXIN_FILE_NAME, SBX_VAULT_MIXINS_DIR_NAME, SKILLS_DIR_NAME,
-    WORKSPACE_MEMORY_DIR_NAME,
+    SBX_KIT_HASH_FILE, SBX_MIXIN_FILE_NAME, SBX_MIXIN_KITS_DIR_NAME, SBX_VAULT_MIXINS_DIR_NAME,
+    SKILLS_DIR_NAME, WORKSPACE_MEMORY_DIR_NAME,
 };
 use crate::client::ProviderModels;
 use crate::utils::{get_env_name, list_file_names, normalize_env_name};
@@ -154,6 +154,10 @@ pub fn sbx_vault_mixins_hash_file() -> PathBuf {
     sbx_vault_mixins_dir().join(SBX_KIT_HASH_FILE)
 }
 
+pub fn sbx_mixin_kits_dir() -> PathBuf {
+    cache_path().join(SBX_MIXIN_KITS_DIR_NAME)
+}
+
 pub fn config_file() -> PathBuf {
     match env::var(get_env_name("config_file")) {
         Ok(value) => PathBuf::from(value),

src/sandbox/mixins.rs

@@ -1,13 +1,16 @@
 use std::env;
+use std::fs;
 use std::fs::{read_dir, read_to_string};
 use std::path::{Path, PathBuf};
 
 use anyhow::{Context, Result};
 use serde_yaml::Value;
+use sha2::{Digest, Sha256};
 
 use crate::config::paths;
 
 const SBX_MIXIN_FILE_NAME: &str = "sbx-mixin.yaml";
+const KIT_SPEC_FILE_NAME: &str = "spec.yaml";
 
 #[derive(Debug, Clone)]
 pub struct DiscoveredMixin {
@@ -17,6 +20,46 @@ pub struct DiscoveredMixin {
     pub domain_count: usize,
 }
 
+impl DiscoveredMixin {
+    pub fn kit_path(&self) -> Result<PathBuf> {
+        if self.path.is_dir() {
+            return Ok(self.path.clone());
+        }
+
+        wrap_mixin_as_kit(&self.path)
+    }
+}
+
+pub fn wrap_mixin_as_kit(mixin_path: &Path) -> Result<PathBuf> {
+    let bytes = fs::read(mixin_path)
+        .with_context(|| format!("Failed to read sbx mixin {}", mixin_path.display()))?;
+    let mut hasher = Sha256::new();
+    hasher.update(&bytes);
+    let hash = format!("{:x}", hasher.finalize());
+
+    let kit_dir = paths::sbx_mixin_kits_dir().join(&hash);
+    let spec_path = kit_dir.join(KIT_SPEC_FILE_NAME);
+
+    if let Ok(existing) = fs::read(&spec_path)
+        && existing == bytes
+    {
+        return Ok(kit_dir);
+    }
+
+    fs::create_dir_all(&kit_dir)
+        .with_context(|| format!("Failed to create mixin kit dir {}", kit_dir.display()))?;
+    fs::write(&spec_path, &bytes)
+        .with_context(|| format!("Failed to write {}", spec_path.display()))?;
+
+    debug!(
+        "Wrapped mixin {} as kit at {}",
+        mixin_path.display(),
+        kit_dir.display()
+    );
+
+    Ok(kit_dir)
+}
+
 pub fn discover() -> Result<Vec<DiscoveredMixin>> {
     let mut out = Vec::new();
 
@@ -234,4 +277,166 @@ network:
         let found = collect_subdir_mixins(&absent);
         assert!(found.is_empty());
     }
+
+    mod wrap_as_kit {
+        use super::*;
+        use serial_test::serial;
+        use std::ffi::OsString;
+
+        struct TestCacheDirGuard {
+            key: String,
+            previous: Option<OsString>,
+            path: PathBuf,
+        }
+
+        impl TestCacheDirGuard {
+            fn new() -> Self {
+                let key = crate::utils::get_env_name("cache_dir");
+                let previous = env::var_os(&key);
+                let nanos = time::SystemTime::now()
+                    .duration_since(time::UNIX_EPOCH)
+                    .unwrap()
+                    .as_nanos();
+                let path = env::temp_dir().join(format!("coyote-mixin-wrap-cache-{nanos}"));
+                fs::create_dir_all(&path).unwrap();
+                unsafe {
+                    env::set_var(&key, &path);
+                }
+                Self {
+                    key,
+                    previous,
+                    path,
+                }
+            }
+        }
+
+        impl Drop for TestCacheDirGuard {
+            fn drop(&mut self) {
+                unsafe {
+                    match &self.previous {
+                        Some(v) => env::set_var(&self.key, v),
+                        None => env::remove_var(&self.key),
+                    }
+                }
+                let _ = fs::remove_dir_all(&self.path);
+            }
+        }
+
+        fn write_mixin(name: &str, content: &str) -> PathBuf {
+            let root = unique_root(&format!("wrap-src-{name}"));
+            let path = root.join("sbx-mixin.yaml");
+            fs::write(&path, content).unwrap();
+            path
+        }
+
+        #[test]
+        #[serial]
+        fn wrap_mixin_as_kit_creates_spec_yaml_with_original_content() {
+            let _guard = TestCacheDirGuard::new();
+            let content = "schemaVersion: \"1\"\nkind: mixin\nname: probe\n";
+            let mixin = write_mixin("content", content);
+
+            let kit_dir = wrap_mixin_as_kit(&mixin).unwrap();
+            let spec = kit_dir.join("spec.yaml");
+
+            assert!(spec.exists(), "spec.yaml must exist in wrapped kit dir");
+            assert_eq!(fs::read_to_string(&spec).unwrap(), content);
+        }
+
+        #[test]
+        #[serial]
+        fn wrap_mixin_as_kit_is_deterministic_for_identical_content() {
+            let _guard = TestCacheDirGuard::new();
+            let content = "schemaVersion: \"1\"\nkind: mixin\nname: probe\n";
+            let mixin_one = write_mixin("dedup-1", content);
+            let mixin_two = write_mixin("dedup-2", content);
+
+            let kit_a = wrap_mixin_as_kit(&mixin_one).unwrap();
+            let kit_b = wrap_mixin_as_kit(&mixin_two).unwrap();
+
+            assert_eq!(
+                kit_a, kit_b,
+                "same content should share the same content-addressed kit dir"
+            );
+        }
+
+        #[test]
+        #[serial]
+        fn wrap_mixin_as_kit_different_content_yields_different_dirs() {
+            let _guard = TestCacheDirGuard::new();
+            let mixin_a = write_mixin("diff-a", "kind: mixin\nname: a\n");
+            let mixin_b = write_mixin("diff-b", "kind: mixin\nname: b\n");
+
+            let kit_a = wrap_mixin_as_kit(&mixin_a).unwrap();
+            let kit_b = wrap_mixin_as_kit(&mixin_b).unwrap();
+
+            assert_ne!(
+                kit_a, kit_b,
+                "different content must hash to different kit dirs"
+            );
+        }
+
+        #[test]
+        #[serial]
+        fn wrap_mixin_as_kit_is_idempotent_on_cache_hit() {
+            let _guard = TestCacheDirGuard::new();
+            let mixin = write_mixin("idempotent", "kind: mixin\nname: probe\n");
+
+            let kit_first = wrap_mixin_as_kit(&mixin).unwrap();
+            let spec = kit_first.join("spec.yaml");
+            let mtime_first = fs::metadata(&spec).unwrap().modified().unwrap();
+
+            std::thread::sleep(std::time::Duration::from_millis(10));
+
+            let kit_second = wrap_mixin_as_kit(&mixin).unwrap();
+            let mtime_second = fs::metadata(kit_second.join("spec.yaml"))
+                .unwrap()
+                .modified()
+                .unwrap();
+
+            assert_eq!(kit_first, kit_second);
+            assert_eq!(
+                mtime_first, mtime_second,
+                "cache hit must not rewrite spec.yaml"
+            );
+        }
+
+        #[test]
+        #[serial]
+        fn kit_path_passes_through_existing_directory() {
+            let _guard = TestCacheDirGuard::new();
+            let dir = unique_root("kit-path-dir-passthrough");
+
+            let m = DiscoveredMixin {
+                path: dir.clone(),
+                label: "vault".into(),
+                install_count: 1,
+                domain_count: 1,
+            };
+
+            assert_eq!(m.kit_path().unwrap(), dir);
+        }
+
+        #[test]
+        #[serial]
+        fn kit_path_wraps_file_into_kit_dir() {
+            let _guard = TestCacheDirGuard::new();
+            let mixin = write_mixin("kit-path-wrap", "kind: mixin\nname: probe\n");
+
+            let m = DiscoveredMixin {
+                path: mixin.clone(),
+                label: mixin.display().to_string(),
+                install_count: 0,
+                domain_count: 0,
+            };
+
+            let wrapped = m.kit_path().unwrap();
+            assert!(wrapped.is_dir(), "kit_path of a file should be a directory");
+            assert!(wrapped.join("spec.yaml").exists());
+            assert_ne!(
+                wrapped, mixin,
+                "kit_path should not return the original file path"
+            );
+        }
+    }
 }

src/sandbox/mod.rs

@@ -347,12 +347,13 @@ fn build_create_args(
     ];
 
     for mixin in mixins {
-        let mixin_str = mixin
-            .path
+        let mixin_kit = mixin.kit_path()?;
+        let mixin_str = mixin_kit
             .to_str()
-            .ok_or_else(|| anyhow!("Mixin path is not valid UTF-8: {}", mixin.path.display()))?;
+            .ok_or_else(|| anyhow!("Mixin kit path is not valid UTF-8: {}", mixin_kit.display()))?
+            .to_string();
         args.push("--kit".to_string());
-        args.push(mixin_str.to_string());
+        args.push(mixin_str);
     }
 
     args.push(SANDBOX_AGENT.to_string());
@@ -590,15 +591,24 @@ mod tests {
     #[test]
     fn build_create_args_emits_base_kit_before_mixins() {
         let kit = PathBuf::from("/cache/sbx-kit");
+        let unique = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap()
+            .as_nanos();
+        let dir_a = env::temp_dir().join(format!("coyote-mixin-a-{unique}"));
+        let dir_b = env::temp_dir().join(format!("coyote-mixin-b-{unique}"));
+        fs::create_dir_all(&dir_a).unwrap();
+        fs::create_dir_all(&dir_b).unwrap();
+
         let mixins = vec![
             DiscoveredMixin {
-                path: PathBuf::from("/cfg/sbx-mixin.yaml"),
+                path: dir_a.clone(),
                 label: "user".into(),
                 install_count: 0,
                 domain_count: 0,
             },
             DiscoveredMixin {
-                path: PathBuf::from("/cfg/agents/sql/sbx-mixin.yaml"),
+                path: dir_b.clone(),
                 label: "sql".into(),
                 install_count: 0,
                 domain_count: 0,
@@ -614,15 +624,18 @@ mod tests {
                 "--kit".to_string(),
                 "/cache/sbx-kit".to_string(),
                 "--kit".to_string(),
-                "/cfg/sbx-mixin.yaml".to_string(),
+                dir_a.display().to_string(),
                 "--kit".to_string(),
-                "/cfg/agents/sql/sbx-mixin.yaml".to_string(),
+                dir_b.display().to_string(),
                 "coyote".to_string(),
                 "--name".to_string(),
                 "my-box".to_string(),
                 ".".to_string(),
             ]
         );
+
+        let _ = fs::remove_dir_all(&dir_a);
+        let _ = fs::remove_dir_all(&dir_b);
     }
 
     #[test]