diff --git a/crates/chanora_bridge/src/lib.rs b/crates/chanora_bridge/src/lib.rs
index 986380a..75235a5 100644
--- a/crates/chanora_bridge/src/lib.rs
+++ b/crates/chanora_bridge/src/lib.rs
@@ -98,6 +98,12 @@ pub enum BridgeError {
     Unmapped(String),
 }
 
+impl BridgeError {
+    fn unmapped_ctx(ctx: impl std::fmt::Display, e: impl std::fmt::Display) -> Self {
+        BridgeError::Unmapped(format!("{ctx}: {e}"))
+    }
+}
+
 impl From<chanora_core::CoreError> for BridgeError {
     fn from(e: chanora_core::CoreError) -> Self {
         match e {
diff --git a/crates/chanora_cache/src/lib.rs b/crates/chanora_cache/src/lib.rs
index 68f79c9..4d1cbad 100644
--- a/crates/chanora_cache/src/lib.rs
+++ b/crates/chanora_cache/src/lib.rs
@@ -29,6 +29,12 @@ pub enum BlobCacheError {
     InvalidKey(String),
 }
 
+impl BlobCacheError {
+    fn io_ctx(ctx: impl std::fmt::Display, e: impl std::fmt::Display) -> Self {
+        BlobCacheError::Io(format!("{ctx}: {e}"))
+    }
+}
+
 /// Content-addressed blob cache backed by cacache.
 pub struct BlobCache {
     cache_dir: PathBuf,
@@ -51,7 +57,7 @@ impl BlobCache {
         // cacache creates the directory on first write, but we create
         // it eagerly so total_size() works before any writes.
         std::fs::create_dir_all(&cache_dir)
-            .map_err(|e| BlobCacheError::Io(format!("mkdir cache: {e}")))?;
+            .map_err(|e| BlobCacheError::io_ctx("mkdir cache", e))?;
         Ok(Self {
             cache_dir,
             max_bytes,
@@ -73,7 +79,7 @@ impl BlobCache {
         let cache_key = format!("{prefix}{key}");
         cacache::write(&self.cache_dir, &cache_key, data)
             .await
-            .map_err(|e| BlobCacheError::Io(format!("cacache write: {e}")))?;
+            .map_err(|e| BlobCacheError::io_ctx("cacache write", e))?;
         Ok(())
     }
 
@@ -106,7 +112,7 @@ impl BlobCache {
         let cache_key = format!("{prefix}{key}");
         cacache::remove(&self.cache_dir, &cache_key)
             .await
-            .map_err(|e| BlobCacheError::Io(format!("cacache remove: {e}")))?;
+            .map_err(|e| BlobCacheError::io_ctx("cacache remove", e))?;
         Ok(())
     }
 
@@ -116,14 +122,14 @@ impl BlobCache {
         tokio::task::spawn_blocking(move || {
             if path.exists() {
                 std::fs::remove_dir_all(&path)
-                    .map_err(|e| BlobCacheError::Io(format!("clear cache: {e}")))?;
+                    .map_err(|e| BlobCacheError::io_ctx("clear cache", e))?;
                 std::fs::create_dir_all(&path)
-                    .map_err(|e| BlobCacheError::Io(format!("recreate cache dir: {e}")))?;
+                    .map_err(|e| BlobCacheError::io_ctx("recreate cache dir", e))?;
             }
             Ok(())
         })
         .await
-        .map_err(|e| BlobCacheError::Io(format!("clear task: {e}")))?
+        .map_err(|e| BlobCacheError::io_ctx("clear task", e))?
     }
 
     /// Return total bytes used by all blobs.
@@ -148,7 +154,7 @@ impl BlobCache {
             Ok(total)
         })
         .await
-        .map_err(|e| BlobCacheError::Io(format!("total_size task: {e}")))?
+        .map_err(|e| BlobCacheError::io_ctx("total_size task", e))?
     }
 
     /// Evict oldest entries by timestamp until total size is under
@@ -198,7 +204,7 @@ impl BlobCache {
             Ok(())
         })
         .await
-        .map_err(|e| BlobCacheError::Io(format!("evict task: {e}")))?
+        .map_err(|e| BlobCacheError::io_ctx("evict task", e))?
     }
 }
 
diff --git a/crates/chanora_protocol/src/lib.rs b/crates/chanora_protocol/src/lib.rs
index 4d77ce6..9f7f0e1 100644
--- a/crates/chanora_protocol/src/lib.rs
+++ b/crates/chanora_protocol/src/lib.rs
@@ -120,3 +120,13 @@ pub enum ProtocolError {
     #[error("file transfer failed: {0}")]
     FileTransfer(String),
 }
+
+impl ProtocolError {
+    fn lost(msg: impl Into<String>) -> Self {
+        ProtocolError::Lost(msg.into())
+    }
+
+    fn backend_ctx(ctx: impl std::fmt::Display, e: impl std::fmt::Display) -> Self {
+        ProtocolError::Backend(format!("{ctx}: {e}"))
+    }
+}
diff --git a/crates/chanora_storage/src/lib.rs b/crates/chanora_storage/src/lib.rs
index 1a31609..4d4471c 100644
--- a/crates/chanora_storage/src/lib.rs
+++ b/crates/chanora_storage/src/lib.rs
@@ -79,8 +79,26 @@ pub enum StorageError {
     Crypto(String),
 }
 
+impl StorageError {
+    fn io_ctx(ctx: impl std::fmt::Display, e: impl std::fmt::Display) -> Self {
+        StorageError::Io(format!("{ctx}: {e}"))
+    }
+
+    fn crypto_ctx(ctx: impl std::fmt::Display, e: impl std::fmt::Display) -> Self {
+        StorageError::Crypto(format!("{ctx}: {e}"))
+    }
+
+    fn sqlite_ctx(ctx: impl std::fmt::Display, e: impl std::fmt::Display) -> Self {
+        StorageError::Sqlite(format!("{ctx}: {e}"))
+    }
+
+    fn migration_ctx(ctx: impl std::fmt::Display, e: impl std::fmt::Display) -> Self {
+        StorageError::Migration(format!("{ctx}: {e}"))
+    }
+}
+
 fn ensure_dir(dir: &Path) -> Result<(), StorageError> {
-    fs::create_dir_all(dir).map_err(|e| StorageError::Io(format!("mkdir {dir:?}: {e}")))
+    fs::create_dir_all(dir).map_err(|e| StorageError::io_ctx(format!("mkdir {dir:?}"), e))
 }
 
 /// Audio-related per-identity settings persisted alongside the
@@ -246,7 +264,7 @@ impl IdentityFileStore {
             Ok(b64) => {
                 let bytes = base64::engine::general_purpose::STANDARD
                     .decode(b64.as_bytes())
-                    .map_err(|e| StorageError::Crypto(format!("keyring dek decode: {e}")))?;
+                    .map_err(|e| StorageError::crypto_ctx("keyring dek decode", e))?;
                 if bytes.len() != 32 {
                     return Err(StorageError::Crypto(format!(
                         "keyring dek length {} (expected 32)",
@@ -359,9 +377,9 @@ impl IdentityFileStore {
         let _ = self.keyring_save(&key);
         let mut f = open_private(&self.dek_path)?;
         f.write_all(&key)
-            .map_err(|e| StorageError::Io(format!("write dek: {e}")))?;
+            .map_err(|e| StorageError::io_ctx("write dek", e))?;
         f.sync_all()
-            .map_err(|e| StorageError::Io(format!("sync dek: {e}")))?;
+            .map_err(|e| StorageError::io_ctx("sync dek", e))?;
         info!(target: "chanora_storage", path = ?self.dek_path, "DEK generated (file fallback)");
         key.zeroize();
         Ok(())
@@ -397,11 +415,11 @@ impl IdentityFileStore {
         let mut f = match fs::File::open(&self.path) {
             Ok(f) => f,
             Err(e) if e.kind() == std::io::ErrorKind::NotFound => return Ok(None),
-            Err(e) => return Err(StorageError::Io(format!("open {:?}: {e}", self.path))),
+            Err(e) => return Err(StorageError::io_ctx(format!("open {:?}", self.path), e)),
         };
         let mut buf = Vec::new();
         f.read_to_end(&mut buf)
-            .map_err(|e| StorageError::Io(format!("read {:?}: {e}", self.path)))?;
+            .map_err(|e| StorageError::io_ctx(format!("read {:?}", self.path), e))?;
         if buf.is_empty() {
             return Ok(None);
         }
@@ -420,11 +438,11 @@ impl IdentityFileStore {
             let nonce = Nonce::from_slice(nonce_bytes);
             let pt = cipher.decrypt(nonce, &buf[12..]).map_err(|e| {
                 key_bytes.zeroize();
-                StorageError::Crypto(format!("decrypt: {e}"))
+                StorageError::crypto_ctx("decrypt", e)
             })?;
             key_bytes.zeroize();
             let s = String::from_utf8(pt)
-                .map_err(|e| StorageError::Crypto(format!("plaintext not utf8: {e}")))?;
+                .map_err(|e| StorageError::crypto_ctx("plaintext not utf8", e))?;
             let trimmed = s.trim().to_string();
             if trimmed.is_empty() {
                 return Ok(None);
@@ -440,7 +458,7 @@ impl IdentityFileStore {
             "identity file is in legacy plaintext format; will encrypt on next save"
         );
         let s = String::from_utf8(buf)
-            .map_err(|e| StorageError::Io(format!("legacy not utf8: {e}")))?;
+            .map_err(|e| StorageError::io_ctx("legacy not utf8", e))?;
         let trimmed = s.trim().to_string();
         if trimmed.is_empty() {
             Ok(None)
@@ -462,7 +480,7 @@ impl IdentityFileStore {
         let nonce = Nonce::from_slice(&nonce_bytes);
         let ct = cipher.encrypt(nonce, plaintext).map_err(|e| {
             key_bytes.zeroize();
-            StorageError::Crypto(format!("encrypt: {e}"))
+            StorageError::crypto_ctx("encrypt", e)
         })?;
         key_bytes.zeroize();
 
@@ -471,14 +489,14 @@ impl IdentityFileStore {
         {
             let mut f = open_private(&tmp)?;
             f.write_all(&nonce_bytes)
-                .map_err(|e| StorageError::Io(format!("write nonce: {e}")))?;
+                .map_err(|e| StorageError::io_ctx("write nonce", e))?;
             f.write_all(&ct)
-                .map_err(|e| StorageError::Io(format!("write ct: {e}")))?;
+                .map_err(|e| StorageError::io_ctx("write ct", e))?;
             f.sync_all()
-                .map_err(|e| StorageError::Io(format!("sync {tmp:?}: {e}")))?;
+                .map_err(|e| StorageError::io_ctx(format!("sync {tmp:?}"), e))?;
         }
         fs::rename(&tmp, &self.path)
-            .map_err(|e| StorageError::Io(format!("rename {tmp:?} -> {:?}: {e}", self.path)))?;
+            .map_err(|e| StorageError::io_ctx(format!("rename {tmp:?} -> {:?}", self.path), e))?;
         info!(target: "chanora_storage", path = ?self.path, "identity persisted (encrypted)");
         Ok(())
     }
@@ -507,17 +525,17 @@ impl IdentityFileStore {
         let path = self.meta_path();
         let tmp = path.with_extension("json.tmp");
         let body = serde_json::to_vec_pretty(m)
-            .map_err(|e| StorageError::Io(format!("meta serialize: {e}")))?;
+            .map_err(|e| StorageError::io_ctx("meta serialize", e))?;
         {
             let mut f = fs::File::create(&tmp)
-                .map_err(|e| StorageError::Io(format!("open meta {tmp:?}: {e}")))?;
+                .map_err(|e| StorageError::io_ctx(format!("open meta {tmp:?}"), e))?;
             f.write_all(&body)
-                .map_err(|e| StorageError::Io(format!("write meta: {e}")))?;
+                .map_err(|e| StorageError::io_ctx("write meta", e))?;
             f.sync_all()
-                .map_err(|e| StorageError::Io(format!("sync meta: {e}")))?;
+                .map_err(|e| StorageError::io_ctx("sync meta", e))?;
         }
         fs::rename(&tmp, &path)
-            .map_err(|e| StorageError::Io(format!("rename meta {tmp:?} -> {path:?}: {e}")))?;
+            .map_err(|e| StorageError::io_ctx(format!("rename meta {tmp:?} -> {path:?}"), e))?;
         Ok(())
     }
 
@@ -623,10 +641,10 @@ fn is_plausibly_legacy_plaintext(buf: &[u8]) -> bool {
 /// and the legacy migration path inside `ensure_dek`.
 fn read_file_dek(path: &Path) -> Result<[u8; 32], StorageError> {
     let mut f =
-        fs::File::open(path).map_err(|e| StorageError::Io(format!("open dek {:?}: {e}", path)))?;
+        fs::File::open(path).map_err(|e| StorageError::io_ctx(format!("open dek {path:?}"), e))?;
     let mut key = [0u8; 32];
     f.read_exact(&mut key)
-        .map_err(|e| StorageError::Io(format!("read dek: {e}")))?;
+        .map_err(|e| StorageError::io_ctx("read dek", e))?;
     Ok(key)
 }
 
@@ -656,7 +674,7 @@ fn open_private(p: &Path) -> Result<fs::File, StorageError> {
         .truncate(true)
         .mode(0o600)
         .open(p)
-        .map_err(|e| StorageError::Io(format!("open {p:?}: {e}")))
+        .map_err(|e| StorageError::io_ctx(format!("open {p:?}"), e))
 }
 
 #[cfg(not(unix))]
@@ -670,7 +688,7 @@ fn open_private(p: &Path) -> Result<fs::File, StorageError> {
         .write(true)
         .truncate(true)
         .open(p)
-        .map_err(|e| StorageError::Io(format!("open {p:?}: {e}")))
+        .map_err(|e| StorageError::io_ctx(format!("open {p:?}"), e))
 }
 
 /// Public abstraction over the per-install envelope-encryption
@@ -725,7 +743,7 @@ impl DekCrypto {
         let nonce = Nonce::from_slice(&nonce_bytes);
         let ct = cipher
             .encrypt(nonce, plaintext)
-            .map_err(|e| StorageError::Crypto(format!("encrypt: {e}")))?;
+            .map_err(|e| StorageError::crypto_ctx("encrypt", e))?;
         let mut out = Vec::with_capacity(12 + ct.len());
         out.extend_from_slice(&nonce_bytes);
         out.extend_from_slice(&ct);
@@ -744,7 +762,7 @@ impl DekCrypto {
         let nonce = Nonce::from_slice(&blob[..12]);
         cipher
             .decrypt(nonce, &blob[12..])
-            .map_err(|e| StorageError::Crypto(format!("decrypt: {e}")))
+            .map_err(|e| StorageError::crypto_ctx("decrypt", e))
     }
 }
 
@@ -821,9 +839,9 @@ impl BookmarkRepository {
         ensure_dir(dir)?;
         let path = dir.join("chanora.db");
         let conn = Connection::open(&path)
-            .map_err(|e| StorageError::Sqlite(format!("open {path:?}: {e}")))?;
+            .map_err(|e| StorageError::sqlite_ctx(format!("open {path:?}"), e))?;
         conn.pragma_update(None, "foreign_keys", "ON")
-            .map_err(|e| StorageError::Sqlite(format!("pragma: {e}")))?;
+            .map_err(|e| StorageError::sqlite_ctx("pragma", e))?;
         conn.execute_batch(
             "CREATE TABLE IF NOT EXISTS bookmarks (
                 id INTEGER PRIMARY KEY AUTOINCREMENT,
@@ -837,7 +855,7 @@ impl BookmarkRepository {
             );
             INSERT OR IGNORE INTO schema_version(v) VALUES (1);",
         )
-        .map_err(|e| StorageError::Migration(format!("init schema: {e}")))?;
+        .map_err(|e| StorageError::migration_ctx("init schema", e))?;
         // Schema v2 migration: encrypted password column. Idempotent.
         let has_blob: i64 = conn
             .query_row(
@@ -845,12 +863,12 @@ impl BookmarkRepository {
                 [],
                 |r| r.get(0),
             )
-            .map_err(|e| StorageError::Migration(format!("table_info: {e}")))?;
+            .map_err(|e| StorageError::migration_ctx("table_info", e))?;
         if has_blob == 0 {
             conn.execute("ALTER TABLE bookmarks ADD COLUMN password_blob BLOB", [])
-                .map_err(|e| StorageError::Migration(format!("add password_blob: {e}")))?;
+                .map_err(|e| StorageError::migration_ctx("add password_blob", e))?;
             conn.execute("INSERT OR IGNORE INTO schema_version(v) VALUES (2)", [])
-                .map_err(|e| StorageError::Migration(format!("bump version: {e}")))?;
+                .map_err(|e| StorageError::migration_ctx("bump version", e))?;
             info!(target: "chanora_storage", "bookmark db migrated to v2 (password_blob)");
         }
         info!(target: "chanora_storage", path = ?path, "bookmark db opened");
@@ -886,7 +904,7 @@ impl BookmarkRepository {
             "INSERT INTO bookmarks (display_name, host, nickname, password, password_blob) VALUES (?1, ?2, ?3, ?4, ?5)",
             params![b.display_name, b.host, b.nickname, plain, blob],
         )
-        .map_err(|e| StorageError::Sqlite(format!("insert: {e}")))?;
+        .map_err(|e| StorageError::sqlite_ctx("insert", e))?;
         Ok(conn.last_insert_rowid())
     }
 
@@ -915,20 +933,20 @@ impl BookmarkRepository {
                 |row| row.get(0),
             )
             .optional()
-            .map_err(|e| StorageError::Sqlite(format!("select: {e}")))?;
+            .map_err(|e| StorageError::sqlite_ctx("select", e))?;
         if let Some(id) = existing {
             conn.execute(
                 "UPDATE bookmarks SET nickname = ?1, password = ?2, password_blob = ?3 WHERE id = ?4",
                 params![b.nickname, plain, blob, id],
             )
-            .map_err(|e| StorageError::Sqlite(format!("update: {e}")))?;
+            .map_err(|e| StorageError::sqlite_ctx("update", e))?;
             Ok(id)
         } else {
             conn.execute(
                 "INSERT INTO bookmarks (display_name, host, nickname, password, password_blob) VALUES (?1, ?2, ?3, ?4, ?5)",
                 params![b.display_name, b.host, b.nickname, plain, blob],
             )
-            .map_err(|e| StorageError::Sqlite(format!("insert: {e}")))?;
+            .map_err(|e| StorageError::sqlite_ctx("insert", e))?;
             Ok(conn.last_insert_rowid())
         }
     }
@@ -957,7 +975,7 @@ impl BookmarkRepository {
                 "UPDATE bookmarks SET display_name=?1, host=?2, nickname=?3, password=?4, password_blob=?5 WHERE id=?6",
                 params![b.display_name, b.host, b.nickname, plain, blob, b.id],
             )
-            .map_err(|e| StorageError::Sqlite(format!("update: {e}")))?;
+            .map_err(|e| StorageError::sqlite_ctx("update", e))?;
         if n == 0 {
             Err(StorageError::NotFound)
         } else {
@@ -972,7 +990,7 @@ impl BookmarkRepository {
             .lock()
             .map_err(|_| StorageError::Sqlite("poisoned lock".to_string()))?;
         conn.execute("DELETE FROM bookmarks WHERE id = ?1", params![id])
-            .map_err(|e| StorageError::Sqlite(format!("delete: {e}")))?;
+            .map_err(|e| StorageError::sqlite_ctx("delete", e))?;
         Ok(())
     }
 
@@ -988,7 +1006,7 @@ impl BookmarkRepository {
             .prepare(
                 "SELECT id, display_name, host, nickname, password, password_blob FROM bookmarks ORDER BY id",
             )
-            .map_err(|e| StorageError::Sqlite(format!("prepare: {e}")))?;
+            .map_err(|e| StorageError::sqlite_ctx("prepare", e))?;
         let rows = stmt
             .query_map([], |row| {
                 let id: i64 = row.get(0)?;
@@ -999,15 +1017,15 @@ impl BookmarkRepository {
                 let blob: Option<Vec<u8>> = row.get(5)?;
                 Ok((id, display_name, host, nickname, plain, blob))
             })
-            .map_err(|e| StorageError::Sqlite(format!("query: {e}")))?;
+            .map_err(|e| StorageError::sqlite_ctx("query", e))?;
         let mut out = Vec::new();
         for r in rows {
             let (id, display_name, host, nickname, plain, blob) =
-                r.map_err(|e| StorageError::Sqlite(format!("row: {e}")))?;
+                r.map_err(|e| StorageError::sqlite_ctx("row", e))?;
             let password = match (blob.as_ref(), self.crypto.as_ref()) {
                 (Some(b), Some(c)) => Some(
                     String::from_utf8(c.decrypt(b)?)
-                        .map_err(|e| StorageError::Crypto(format!("blob utf8: {e}")))?,
+                        .map_err(|e| StorageError::crypto_ctx("blob utf8", e))?,
                 ),
                 (Some(_), None) => {
                     // We have an encrypted blob but no key. Skip the