feat(memory): add snapshot-based memory_diff module for change tracking

src/core/all.rs

@@ -219,6 +219,8 @@ fn build_registered_controllers() -> Vec<RegisteredController> {
     // Memory sources — user-configured data connectors registry
     controllers
         .extend(crate::openhuman::memory_sources::all_memory_sources_registered_controllers());
+    // Memory diff — snapshot-based change tracking for memory sources
+    controllers.extend(crate::openhuman::memory_diff::all_memory_diff_registered_controllers());
     // Link shortener for long tracking URLs — saves LLM tokens
     controllers
         .extend(crate::openhuman::redirect_links::all_redirect_links_registered_controllers());
@@ -366,6 +368,7 @@ fn build_declared_controller_schemas() -> Vec<ControllerSchema> {
         crate::openhuman::memory_sync::sync_status::all_memory_sync_status_controller_schemas(),
     );
     schemas.extend(crate::openhuman::memory_sources::all_memory_sources_controller_schemas());
+    schemas.extend(crate::openhuman::memory_diff::all_memory_diff_controller_schemas());
     schemas.extend(crate::openhuman::redirect_links::all_redirect_links_controller_schemas());
     schemas.extend(crate::openhuman::referral::all_referral_controller_schemas());
     schemas.extend(crate::openhuman::billing::all_billing_controller_schemas());
@@ -478,6 +481,9 @@ pub fn namespace_description(namespace: &str) -> Option<&'static str> {
         "memory_sources" => Some(
             "User-configured data connectors (Composio, folders, GitHub repos, RSS, web pages) that feed memory.",
         ),
+        "memory_diff" => Some(
+            "Snapshot-based change tracking for memory sources — capture state, compute diffs, and surface changes to agents.",
+        ),
         "redirect_links" => Some(
             "Shorten long tracking URLs to `openhuman://link/<id>` placeholders (SQLite-backed) to save tokens in prompts, with round-trip rewrite helpers.",
         ),

src/core/event_bus/events.rs

@@ -252,6 +252,25 @@ pub enum DomainEvent {
         queue_depth: usize,
     },
 
+    // ── Memory Diff ─────────────────────────────────────────────────────
+    /// A snapshot of a memory source's chunk state was captured.
+    MemoryDiffSnapshotTaken {
+        snapshot_id: String,
+        source_id: String,
+        source_kind: String,
+        item_count: usize,
+        trigger: String,
+    },
+    /// A diff was computed between two snapshots.
+    MemoryDiffComputed {
+        source_id: String,
+        from_snapshot_id: Option<String>,
+        to_snapshot_id: String,
+        added: usize,
+        removed: usize,
+        modified: usize,
+    },
+
     // ── Channels ────────────────────────────────────────────────────────
     /// An inbound channel message from the transport layer, ready for processing.
     ///
@@ -1020,7 +1039,9 @@ impl DomainEvent {
             | Self::MemorySyncStageChanged { .. }
             | Self::MemoryIngestionStarted { .. }
             | Self::MemoryIngestionCompleted { .. }
-            | Self::DocumentCanonicalized { .. } => "memory",
+            | Self::DocumentCanonicalized { .. }
+            | Self::MemoryDiffSnapshotTaken { .. }
+            | Self::MemoryDiffComputed { .. } => "memory",
 
             Self::CacheRebuilt { .. } => "learning",
 
@@ -1152,6 +1173,8 @@ impl DomainEvent {
             Self::MemoryIngestionStarted { .. } => "MemoryIngestionStarted",
             Self::MemoryIngestionCompleted { .. } => "MemoryIngestionCompleted",
             Self::DocumentCanonicalized { .. } => "DocumentCanonicalized",
+            Self::MemoryDiffSnapshotTaken { .. } => "MemoryDiffSnapshotTaken",
+            Self::MemoryDiffComputed { .. } => "MemoryDiffComputed",
             Self::CacheRebuilt { .. } => "CacheRebuilt",
             Self::ChannelInboundMessage { .. } => "ChannelInboundMessage",
             Self::ChannelMessageReceived { .. } => "ChannelMessageReceived",

src/openhuman/memory_diff/mod.rs

@@ -0,0 +1,32 @@
+//! Snapshot-based change tracking for memory sources.
+//!
+//! After each sync, this module captures what's in the chunk store for
+//! that source, then diffs against previous snapshots to surface
+//! additions, removals, and modifications — helping agents understand
+//! how their world view has changed over time.
+//!
+//! Snapshots are built from already-ingested data in `mem_tree_chunks`
+//! (not by re-calling source readers), making them free of API calls.
+//!
+//! Features:
+//! - Per-source snapshots (auto after sync, or manual via RPC)
+//! - Diff between any two snapshots
+//! - Named checkpoints for cross-source "what changed since X" queries
+//! - Agent tool for in-conversation diff queries
+
+pub mod ops;
+pub mod rpc;
+pub mod schemas;
+pub mod store;
+pub mod tools;
+pub mod types;
+
+pub use schemas::{
+    all_controller_schemas as all_memory_diff_controller_schemas,
+    all_registered_controllers as all_memory_diff_registered_controllers,
+};
+pub use tools::MemoryDiffTool;
+pub use types::{
+    ChangeKind, Checkpoint, CrossSourceDiff, DiffResult, DiffSummary, ItemChange, Snapshot,
+    SnapshotItem, SnapshotTrigger,
+};