diff --git a/desktop/src-tauri/src/commands/agents.rs b/desktop/src-tauri/src/commands/agents.rs
index 398fc7b719..7cdb7a361e 100644
--- a/desktop/src-tauri/src/commands/agents.rs
+++ b/desktop/src-tauri/src/commands/agents.rs
@@ -46,7 +46,13 @@ fn build_deploy_payload(
 
     // Resolve system prompt and model via the persona (same as local spawn).
     // Re-reads the persona store so edits take effect without recreating the agent.
-    let personas = load_personas(app).unwrap_or_default();
+    let personas = load_personas(app).unwrap_or_else(|e| {
+        eprintln!(
+            "sprout-desktop: failed to load personas for deploy payload (agent {}) — proceeding without persona context: {e}",
+            record.name
+        );
+        Vec::new()
+    });
     let (effective_prompt, effective_model) =
         crate::managed_agents::resolve_effective_prompt_and_model(
             record.persona_id.as_deref(),
diff --git a/desktop/src-tauri/src/managed_agents/runtime.rs b/desktop/src-tauri/src/managed_agents/runtime.rs
index baee5f443b..80f1f64685 100644
--- a/desktop/src-tauri/src/managed_agents/runtime.rs
+++ b/desktop/src-tauri/src/managed_agents/runtime.rs
@@ -672,7 +672,13 @@ pub fn spawn_agent_child(
     // Resolve system prompt and model via the extracted helper. Re-reads
     // the persona store at spawn time so edits take effect without
     // deleting and recreating the agent.
-    let personas = super::load_personas(app).unwrap_or_default();
+    let personas = super::load_personas(app).unwrap_or_else(|e| {
+        eprintln!(
+            "sprout-desktop: failed to load personas for agent {} — spawning with no persona context: {e}",
+            record.name
+        );
+        Vec::new()
+    });
     let (effective_prompt, effective_model) = resolve_effective_prompt_and_model(
         record.persona_id.as_deref(),
         &personas,
diff --git a/desktop/src-tauri/src/managed_agents/storage.rs b/desktop/src-tauri/src/managed_agents/storage.rs
index f373a1226d..70e661e1da 100644
--- a/desktop/src-tauri/src/managed_agents/storage.rs
+++ b/desktop/src-tauri/src/managed_agents/storage.rs
@@ -40,7 +40,36 @@ pub fn load_managed_agents(app: &AppHandle) -> Result<Vec<ManagedAgentRecord>, S
 
     let content = fs::read_to_string(&path)
         .map_err(|error| format!("failed to read agent store: {error}"))?;
-    serde_json::from_str(&content).map_err(|error| format!("failed to parse agent store: {error}"))
+    let mut records: Vec<ManagedAgentRecord> =
+        serde_json::from_str(&content).map_err(|error| format!("failed to parse agent store: {error}"))?;
+
+    // One-time migration: clear stale system_prompt/model snapshots on
+    // persona-backed agents. Before this fix, creation snapshotted the
+    // persona's values onto the agent record. With the new precedence logic
+    // (agent record wins when set), those stale snapshots would be treated as
+    // explicit user overrides and block persona updates from taking effect.
+    //
+    // Safe to clear unconditionally: the old code ignored agent-level overrides
+    // for persona-backed agents, so no user has ever set a meaningful override.
+    let mut migrated = false;
+    for record in &mut records {
+        if record.persona_id.is_some() {
+            if record.system_prompt.is_some() {
+                record.system_prompt = None;
+                migrated = true;
+            }
+            if record.model.is_some() {
+                record.model = None;
+                migrated = true;
+            }
+        }
+    }
+    if migrated {
+        // Persist the migration so it only runs once.
+        save_managed_agents(app, &records)?;
+    }
+
+    Ok(records)
 }
 
 pub fn save_managed_agents(app: &AppHandle, records: &[ManagedAgentRecord]) -> Result<(), String> {