feat: discover subject session history

crates/session-store/src/lib.rs

@@ -75,6 +75,7 @@ pub mod history;
 mod legacy_session_log;
 pub mod logged_item;
 mod paste_artifact;
+pub mod public_index;
 pub mod public_snapshot;
 pub mod segment;
 pub mod segment_log;
@@ -95,6 +96,14 @@ pub use history::{
 };
 pub use logged_item::{LoggedContentPart, LoggedItem, LoggedRole, from_logged, to_logged};
 pub use paste_artifact::PasteArtifactLimits;
+pub use public_index::{
+    DEFAULT_SESSION_PUBLIC_INDEX_MAX_BYTES, DEFAULT_SESSION_PUBLIC_INDEX_MAX_ENTRIES,
+    DEFAULT_SESSION_PUBLIC_INDEX_MAX_SEGMENTS, SESSION_PUBLIC_INDEX_COMPACT_TEXT_MAX_BYTES,
+    SessionPublicIndex, SessionPublicIndexEntry, SessionPublicIndexEntryKind,
+    SessionPublicIndexLimits, SessionPublicIndexLineage, SessionPublicIndexOriginKind,
+    SessionPublicIndexReadError, SessionPublicIndexSegment, SessionPublicIndexToolPart,
+    read_session_public_index,
+};
 pub use public_snapshot::{
     DEFAULT_RETAINED_HISTORY_MAX_ENTRIES, DEFAULT_RETAINED_HISTORY_MAX_RESPONSE_BYTES,
     DEFAULT_RETAINED_HISTORY_MAX_SCAN_BYTES, DEFAULT_RETAINED_HISTORY_MAX_SEGMENTS,

crates/session-store/src/public_snapshot.rs

@@ -978,7 +978,7 @@ pub fn project_session_snapshot(session_id: SessionId, log: &[LogEntry]) -> Sess
     project_session_snapshot_for_segment(session_id, None, log)
 }
 
-fn project_session_snapshot_for_segment(
+pub(crate) fn project_session_snapshot_for_segment(
     session_id: SessionId,
     segment_id: Option<SegmentId>,
     log: &[LogEntry],

crates/session-store/src/worker_session_store.rs

@@ -468,6 +468,23 @@ impl WorkerSessionStore {
         Ok(())
     }
 
+    /// Enumerate canonical Segment logs in ascending identity order without
+    /// creating or migrating state. Unlike the general [`Store`] listing, this
+    /// observation boundary rejects malformed names and non-regular files so a
+    /// persisted Segment cannot be silently omitted from a public index.
+    pub(crate) fn list_segments_read_only(
+        &self,
+        session_id: SessionId,
+    ) -> Result<Vec<SegmentId>, StoreError> {
+        self.validate_retained_session(session_id)?;
+        segment_log_paths(&self.root).map(|paths| {
+            paths
+                .into_iter()
+                .map(|(segment_id, _)| segment_id)
+                .collect()
+        })
+    }
+
     pub fn segment_log_len(&self, segment_id: SegmentId) -> Result<u64, StoreError> {
         Ok(fs::metadata(self.log_path(segment_id))?.len())
     }