1 files changed, 43 insertions, 0 deletions
diff --git a/crates/fidget-spinner-cli/src/mcp/host/binary.rs b/crates/fidget-spinner-cli/src/mcp/host/binary.rs
new file mode 100644
index 0000000..2107461
--- /dev/null
+++ b/crates/fidget-spinner-cli/src/mcp/host/binary.rs
@@ -0,0 +1,43 @@
+use std::fs;
+use std::io;
+use std::path::{Path, PathBuf};
+
+use fidget_spinner_store_sqlite::StoreError;
+
+use crate::mcp::protocol::BinaryFingerprint;
+
+pub(super) struct BinaryRuntime {
+    pub(super) path: PathBuf,
+    startup_fingerprint: BinaryFingerprint,
+    pub(super) launch_path_stable: bool,
+}
+
+impl BinaryRuntime {
+    pub(super) fn new(path: PathBuf) -> Result<Self, StoreError> {
+        let startup_fingerprint = fingerprint_binary(&path)?;
+        Ok(Self {
+            launch_path_stable: !path
+                .components()
+                .any(|component| component.as_os_str().to_string_lossy() == "target"),
+            path,
+            startup_fingerprint,
+        })
+    }
+
+    pub(super) fn rollout_pending(&self) -> Result<bool, StoreError> {
+        Ok(fingerprint_binary(&self.path)? != self.startup_fingerprint)
+    }
+}
+
+fn fingerprint_binary(path: &Path) -> Result<BinaryFingerprint, StoreError> {
+    let metadata = fs::metadata(path)?;
+    let modified_unix_nanos = metadata
+        .modified()?
+        .duration_since(std::time::UNIX_EPOCH)
+        .map_err(|error| io::Error::other(format!("invalid binary mtime: {error}")))?
+        .as_nanos();
+    Ok(BinaryFingerprint {
+        length_bytes: metadata.len(),
+        modified_unix_nanos,
+    })
+}