fix: mark only IDX quotes behind the session; test the wiring

Review findings on #71:
- The IDX session rule flagged non-IDX data: US screen rows on Monday
  evening WIB, and JP/HK/SG rows on their own holidays. Only `.JK`
  quotes and `--region id` screens are marked now.
- Nothing tested the marking call sites. A screen test checks IDX rows
  online and offline, and US rows unmarked. A quote test reads a cache
  entry in 0.3.3's format (no field) offline.
- The get_quotes description now says the flag also means the stock did
  not trade, or an exchange holiday; screen_stocks mentions the field.
- latest_session is pub(crate).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V3syn2fN2LNo5pvTSqc6eh

crates/idx-cli/tests/cli.rs

@@ -2407,6 +2407,62 @@ fn msn_screen_ranks_complete_candidates_and_caches_before_limit() {
     }
 }
 
+#[test]
+fn msn_screen_flags_idx_rows_behind_the_session() {
+    let root = test_env_dir("screen-behind-session");
+    let fixture = write_large_screener_fixture(&root, Some(503));
+    let behind = |rows: &serde_json::Value| -> Vec<bool> {
+        rows.as_array()
+            .unwrap()
+            .iter()
+            .map(|row| row["behind_session"].as_bool().unwrap())
+            .collect()
+    };
+    // Every fixture row last traded on 2026-01-02, long before any session now.
+    let fresh = run_success_json(&mut screener_fixture_command(
+        &root,
+        &fixture,
+        "top-performers",
+        3,
+    ));
+    assert_eq!(behind(&fresh), [true; 3]);
+    let mut offline = screener_fixture_command(&root, &fixture, "top-performers", 3);
+    offline.env("IDX_MOCK_ERROR", "1").arg("--offline");
+    assert_eq!(behind(&run_success_json(&mut offline)), [true; 3]);
+    // IDX's session rule says nothing about other exchanges.
+    let mut us = screener_fixture_command(&root, &fixture, "top-performers", 3);
+    us.args(["--region", "us"]);
+    assert_eq!(behind(&run_success_json(&mut us)), [false; 3]);
+    fs::remove_dir_all(root).unwrap();
+}
+
+#[test]
+fn quote_read_from_a_0_3_3_cache_entry_is_behind_the_session() {
+    let root = test_env_dir("quote-behind-session");
+    let mut warm = mock_bin_with_root(&root);
+    run_success_json(warm.args(["-o", "json", "stocks", "quote", "BBCA"]));
+    let entry = fs::read_dir(root.join("cache"))
+        .unwrap()
+        .flat_map(|dir| fs::read_dir(dir.unwrap().path()).unwrap())
+        .flat_map(|bucket| fs::read_dir(bucket.unwrap().path()).unwrap())
+        .map(|file| file.unwrap().path())
+        .find(|path| path.ends_with("BBCA.JK.json"))
+        .expect("cached quote");
+    // 0.3.3 wrote quotes without the field; this one last traded long ago.
+    let mut cached: serde_json::Value =
+        serde_json::from_str(&fs::read_to_string(&entry).unwrap()).unwrap();
+    let data = cached["data"].as_object_mut().unwrap();
+    data.remove("behind_session")
+        .expect("field is cached unmarked");
+    data.insert("as_of".into(), "2026-01-02T16:15:00+07:00".into());
+    fs::write(&entry, cached.to_string()).unwrap();
+    let mut offline = mock_bin_with_root(&root);
+    let quotes =
+        run_success_json(offline.args(["--offline", "-o", "json", "stocks", "quote", "BBCA"]));
+    assert_eq!(quotes[0]["behind_session"], true);
+    fs::remove_dir_all(root).unwrap();
+}
+
 #[test]
 fn msn_screen_rejects_invalid_totals_without_populating_cache() {
     for (name, count) in [("missing", None), ("incomplete", Some(504))] {

crates/idx-core/src/api/types.rs

@@ -51,8 +51,9 @@ pub struct Quote {
     #[serde(default)]
     pub as_of: Option<DateTime<FixedOffset>>,
     /// True when `as_of` is before the latest IDX session that has ended: the
-    /// provider has not caught up yet (MSN can lag hours after the close), or
-    /// the stock did not trade. False when `as_of` is unknown. Set when the
+    /// provider has not caught up yet (MSN can lag hours after the close), the
+    /// stock did not trade, or the day was an exchange holiday. False when
+    /// `as_of` is unknown and for non-IDX symbols and regions. Set when the
     /// quote is returned, not when it is cached.
     #[serde(default)]
     pub behind_session: bool,

crates/idx-core/src/market.rs

@@ -34,10 +34,11 @@ impl Market<'_> {
     ) -> Result<Vec<Fetched<Quote>>, IdxError> {
         let idx = self.idx;
         let bucket = idx.bucket("quote");
+        let session = latest_session(Utc::now());
         let mut quotes = Vec::with_capacity(symbols.len());
         for symbol in symbols {
             let resolved = idx.resolve(symbol.as_ref())?;
-            quotes.push(cached_fetch(
+            let mut quote = cached_fetch(
                 &idx.cache,
                 CacheSpec {
                     bucket: &bucket,
@@ -49,11 +50,12 @@ impl Market<'_> {
                 policy,
                 || idx.provider.market().quote(&resolved),
                 Ok,
-            )?);
-        }
-        let session = latest_session(Utc::now());
-        for quote in &mut quotes {
-            mark_behind_session(&mut quote.data, session);
+            )?;
+            // The session rule is IDX's; other exchanges keep other hours.
+            if resolved.ends_with(".JK") {
+                mark_behind_session(&mut quote.data, session);
+            }
+            quotes.push(quote);
         }
         Ok(quotes)
     }
@@ -137,9 +139,11 @@ impl Market<'_> {
         )?;
         sort_screener_quotes(&mut fetched.data, filter);
         fetched.data.truncate(limit);
-        let session = latest_session(Utc::now());
-        for quote in &mut fetched.data {
-            mark_behind_session(quote, session);
+        if region == ScreenRegion::Id {
+            let session = latest_session(Utc::now());
+            for quote in &mut fetched.data {
+                mark_behind_session(quote, session);
+            }
         }
         Ok(fetched)
     }
@@ -151,7 +155,7 @@ const SESSION_END: NaiveTime = NaiveTime::from_hms_opt(16, 15, 0).expect("valid
 
 /// The latest weekday whose IDX session has ended by `now`. Exchange holidays
 /// are not known offline, so on a weekday holiday this is the holiday itself.
-pub fn latest_session(now: DateTime<Utc>) -> NaiveDate {
+pub(crate) fn latest_session(now: DateTime<Utc>) -> NaiveDate {
     let now = now.with_timezone(&idx_offset());
     let mut day = now.date_naive();
     if now.time() < SESSION_END {

crates/idx-mcp/src/server.rs

@@ -116,7 +116,8 @@ impl IdxServer {
     #[tool(
         description = "Latest quotes (price, change, volume, 52-week range, market cap) \
 for one or more IDX tickers. `as_of` is the last trade in WIB; `behind_session` is true \
-when that is before the latest IDX session, so the price is not that session's close."
+when that is before the latest IDX session, so the price is not that session's close: the \
+provider lags, the stock did not trade, or the day was an exchange holiday."
     )]
     async fn get_quotes(&self, params: Parameters<SymbolsParams>) -> ToolResult {
         let symbols = match checked_symbols(params.0.symbols) {
@@ -149,7 +150,8 @@ when that is before the latest IDX session, so the price is not that session's c
 
     #[tool(
         description = "Run a stock screen (top/worst performers, high dividend, low P/E, \
-52-week highs/lows, high volume, large cap)."
+52-week highs/lows, high volume, large cap). Rows carry `as_of` and, for the IDX region, \
+`behind_session` as in get_quotes."
     )]
     async fn screen_stocks(&self, params: Parameters<ScreenParams>) -> ToolResult {
         let ScreenParams {

crates/idx-mcp/tests/golden/tools.json

@@ -397,7 +397,7 @@
     "name": "get_price_history"
   },
   {
-    "description": "Latest quotes (price, change, volume, 52-week range, market cap) for one or more IDX tickers. `as_of` is the last trade in WIB; `behind_session` is true when that is before the latest IDX session, so the price is not that session's close.",
+    "description": "Latest quotes (price, change, volume, 52-week range, market cap) for one or more IDX tickers. `as_of` is the last trade in WIB; `behind_session` is true when that is before the latest IDX session, so the price is not that session's close: the provider lags, the stock did not trade, or the day was an exchange holiday.",
     "inputSchema": {
       "$schema": "https://json-schema.org/draft/2020-12/schema",
       "properties": {
@@ -457,7 +457,7 @@
     "name": "ownership_sync"
   },
   {
-    "description": "Run a stock screen (top/worst performers, high dividend, low P/E, 52-week highs/lows, high volume, large cap).",
+    "description": "Run a stock screen (top/worst performers, high dividend, low P/E, 52-week highs/lows, high volume, large cap). Rows carry `as_of` and, for the IDX region, `behind_session` as in get_quotes.",
     "inputSchema": {
       "$schema": "https://json-schema.org/draft/2020-12/schema",
       "properties": {