fix: use platform cache dir for fastembed models

Previously, fastembed created .fastembed_cache in the current working
directory, polluting project folders with symlinks.

Now uses platform-appropriate cache directories:
- macOS: ~/Library/Caches/com.vestige.core/fastembed
- Linux: ~/.cache/vestige/fastembed
- Windows: %LOCALAPPDATA%\vestige\cache\fastembed

Can still be overridden with FASTEMBED_CACHE_PATH env var.

Fixes user feedback about .fastembed_cache appearing in random folders.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -136,12 +136,14 @@ claude mcp add vestige /full/path/to/vestige-mcp -s user
 </details>
 
 <details>
-<summary>.fastembed_cache appearing in project folders</summary>
+<summary>Model cache location</summary>
 
-Run once from home directory to create cache there:
-```bash
-cd ~ && vestige health
-```
+The embedding model (~130MB) is cached in platform-specific directories:
+- **macOS**: `~/Library/Caches/com.vestige.core/fastembed`
+- **Linux**: `~/.cache/vestige/fastembed`
+- **Windows**: `%LOCALAPPDATA%\vestige\cache\fastembed`
+
+Override with: `export FASTEMBED_CACHE_PATH=/custom/path`
 </details>
 
 <details>

crates/vestige-core/src/embeddings/local.rs

@@ -35,14 +35,47 @@ pub const BATCH_SIZE: usize = 32;
 /// Result type for model initialization
 static EMBEDDING_MODEL_RESULT: OnceLock<Result<Mutex<TextEmbedding>, String>> = OnceLock::new();
 
+/// Get the default cache directory for fastembed models
+/// Uses FASTEMBED_CACHE_PATH env var, or falls back to platform cache directory
+fn get_cache_dir() -> std::path::PathBuf {
+    if let Ok(path) = std::env::var("FASTEMBED_CACHE_PATH") {
+        return std::path::PathBuf::from(path);
+    }
+
+    // Use platform-appropriate cache directory via directories crate
+    // macOS: ~/Library/Caches/com.vestige.core/fastembed
+    // Linux: ~/.cache/vestige/fastembed
+    // Windows: %LOCALAPPDATA%\vestige\cache\fastembed
+    if let Some(proj_dirs) = directories::ProjectDirs::from("com", "vestige", "core") {
+        return proj_dirs.cache_dir().join("fastembed");
+    }
+
+    // Fallback to home directory
+    if let Some(base_dirs) = directories::BaseDirs::new() {
+        return base_dirs.home_dir().join(".cache/vestige/fastembed");
+    }
+
+    // Last resort fallback (shouldn't happen)
+    std::path::PathBuf::from(".fastembed_cache")
+}
+
 /// Initialize the global embedding model
 /// Using nomic-embed-text-v1.5 (768d) - 8192 token context, Matryoshka support
 fn get_model() -> Result<std::sync::MutexGuard<'static, TextEmbedding>, EmbeddingError> {
     let result = EMBEDDING_MODEL_RESULT.get_or_init(|| {
+        // Get cache directory (respects FASTEMBED_CACHE_PATH env var)
+        let cache_dir = get_cache_dir();
+
+        // Create cache directory if it doesn't exist
+        if let Err(e) = std::fs::create_dir_all(&cache_dir) {
+            tracing::warn!("Failed to create cache directory {:?}: {}", cache_dir, e);
+        }
+
         // nomic-embed-text-v1.5: 768 dimensions, 8192 token context
         // Matryoshka representation learning, fully open source
-        let options =
-            InitOptions::new(EmbeddingModel::NomicEmbedTextV15).with_show_download_progress(true);
+        let options = InitOptions::new(EmbeddingModel::NomicEmbedTextV15)
+            .with_show_download_progress(true)
+            .with_cache_dir(cache_dir);
 
         TextEmbedding::try_new(options)
             .map(Mutex::new)

docs/CONFIGURATION.md

@@ -10,19 +10,19 @@ Vestige downloads the **Nomic Embed Text v1.5** model (~130MB) from Hugging Face
 
 **All subsequent runs are fully offline.**
 
-Model cache location:
-- Creates `.fastembed_cache/` in the current working directory on first run
-- Contains symlinks to model files in `~/.cache/huggingface/`
+### Model Cache Location
 
-**Recommended**: Run your first Vestige command from your home directory:
-```bash
-cd ~
-vestige health   # Creates ~/.fastembed_cache/ once
-```
+The embedding model is cached in platform-specific directories:
 
-Or set the environment variable:
+| Platform | Cache Location |
+|----------|----------------|
+| macOS | `~/Library/Caches/com.vestige.core/fastembed` |
+| Linux | `~/.cache/vestige/fastembed` |
+| Windows | `%LOCALAPPDATA%\vestige\cache\fastembed` |
+
+Override with environment variable:
 ```bash
-export FASTEMBED_CACHE_PATH="$HOME/.fastembed_cache"
+export FASTEMBED_CACHE_PATH="/custom/path"
 ```
 
 ---