From 3d77e60a02d8286b45829e505291a8892570d3be Mon Sep 17 00:00:00 2001
From: Riz Ashraf <reazul.ashraf@inseinc.com>
Date: Wed, 7 Oct 2026 17:04:52 +0100
Subject: [PATCH] feat(embedding,notes): implement ADR-0056 Blake3 stable
 hashing and ADR-0057 priority-aware retention

---
 server/src/embedding.rs      | 22 +++++++++++++++-------
 server/src/handlers/meta.rs  | 17 +++++++++++++++--
 server/src/handlers/notes.rs |  9 ++++++++-
 3 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/server/src/embedding.rs b/server/src/embedding.rs
index 7994b9a..317cc1a 100644
--- a/server/src/embedding.rs
+++ b/server/src/embedding.rs
@@ -152,7 +152,6 @@ fn fallback_embed(text: &str) -> Vec<f32> {
         return vec;
     }
 
-    use std::hash::{Hash, Hasher};
     for word in words {
         let clean: String = word
             .chars()
@@ -163,18 +162,17 @@ fn fallback_embed(text: &str) -> Vec<f32> {
             continue;
         }
 
-        let mut hasher = std::collections::hash_map::DefaultHasher::new();
-        clean.hash(&mut hasher);
-        let h = hasher.finish();
+        let hash_bytes = blake3::hash(clean.as_bytes());
+        let h = u64::from_le_bytes(hash_bytes.as_bytes()[0..8].try_into().unwrap());
         let idx = (h as usize) % DIM;
         let sign = if (h >> 32) & 1 == 0 { 1.0f32 } else { -1.0f32 };
         vec[idx] += sign;
 
         let chars: Vec<char> = clean.chars().collect();
         for window in chars.windows(3) {
-            let mut h2 = std::collections::hash_map::DefaultHasher::new();
-            window.hash(&mut h2);
-            let hv = h2.finish();
+            let window_str: String = window.iter().collect();
+            let h2_bytes = blake3::hash(window_str.as_bytes());
+            let hv = u64::from_le_bytes(h2_bytes.as_bytes()[0..8].try_into().unwrap());
             let idx2 = (hv as usize) % DIM;
             let s2 = if (hv >> 32) & 1 == 0 { 0.5f32 } else { -0.5f32 };
             vec[idx2] += s2;
@@ -378,4 +376,14 @@ mod tests {
             assert_eq!(embedding.len(), 384);
         }
     }
+
+    #[test]
+    fn test_fallback_embed_deterministic_stability() {
+        let text = "The quick brown fox jumps over the lazy dog";
+        let emb1 = fallback_embed(text);
+        let emb2 = fallback_embed(text);
+        assert_eq!(emb1.len(), 384);
+        assert_eq!(emb1, emb2);
+        assert!((cosine_similarity(&emb1, &emb2) - 1.0).abs() < 1e-5);
+    }
 }
diff --git a/server/src/handlers/meta.rs b/server/src/handlers/meta.rs
index 2ce8aa2..8dad604 100644
--- a/server/src/handlers/meta.rs
+++ b/server/src/handlers/meta.rs
@@ -665,7 +665,20 @@ impl McpTool for TechDebtHandler {
                         effort_estimate: req.effort_estimate,
                     });
                     if debts.len() > 300 {
-                        debts.remove(0);
+                        let severity_rank = |sev: Option<&str>| match sev.unwrap_or("").to_lowercase().as_str() {
+                            "critical" => 4,
+                            "high" => 3,
+                            "medium" => 2,
+                            "low" => 1,
+                            _ => 1,
+                        };
+                        if let Some((idx_to_remove, _)) = debts.iter().enumerate().min_by_key(|(_, d)| {
+                            let status_score = if d.is_resolved { 0 } else { 10 };
+                            let sev_score = severity_rank(d.severity.as_deref());
+                            (status_score + sev_score, d.created_at)
+                        }) {
+                            debts.remove(idx_to_remove);
+                        }
                     }
                 });
                 Ok("Tech debt logged".to_string())
@@ -2827,4 +2840,4 @@ mod tests {
             .unwrap();
         assert!(pre_res.contains("active_tasks"));
     }
-}
+
diff --git a/server/src/handlers/notes.rs b/server/src/handlers/notes.rs
index 6ec454d..1c89eef 100644
--- a/server/src/handlers/notes.rs
+++ b/server/src/handlers/notes.rs
@@ -108,7 +108,14 @@ impl McpTool for AddSessionSummaryHandler {
                 next_steps: req.next_steps.unwrap_or_default(),
             });
             if summaries.len() > 200 {
-                summaries.remove(0);
+                let now = crate::handlers::utils::now_secs();
+                if let Some((idx_to_remove, _)) = summaries.iter().enumerate().min_by_key(|(_, s)| {
+                    let is_expired = s.expires_at.map(|exp| exp < now).unwrap_or(false);
+                    let status_score = if is_expired { 0 } else { 1 };
+                    (status_score, s.timestamp)
+                }) {
+                    summaries.remove(idx_to_remove);
+                }
             }
         });
         Ok("Session summary added".to_string())