diff --git a/crates/aura-ingest/src/lib.rs b/crates/aura-ingest/src/lib.rs
index 7756f22..7134e3c 100644
--- a/crates/aura-ingest/src/lib.rs
+++ b/crates/aura-ingest/src/lib.rs
@@ -87,15 +87,23 @@ pub fn transpose_m1(bars: &[M1Parsed]) -> M1Columns {
 /// Drain a data-server M1 window into transposed SoA columns. Reads the
 /// chronological chunk iterator to exhaustion into one AoS buffer, then
 /// transposes once at the boundary (C3 — one merge point, not per chunk).
-/// `None` if the symbol has no data in `[from_ms, to_ms]` (data-server's own
-/// `None`); the inclusive Unix-ms window bounds are data-server's contract.
+/// `None` if the symbol has no data in the window (data-server's own `None`);
+/// the inclusive Unix-ms window bounds are data-server's contract.
+///
+/// Each bound is an `Option<i64>`: `None` means unbounded on that side
+/// (data-server skips the coarse `unix_ms_to_year_month` file filter rather
+/// than reaching for a sentinel). `from_ms = None` reads from the start of
+/// history; `to_ms = None` reads to the end. This threads data-server's own
+/// per-bound `Option` contract through unchanged, so "to the end of history"
+/// is expressible without an `i64::MAX` sentinel (which panics upstream in
+/// chrono's `from_timestamp_millis`).
 pub fn load_m1_window(
     server: &Arc<DataServer>,
     symbol: &str,
-    from_ms: i64,
-    to_ms: i64,
+    from_ms: Option<i64>,
+    to_ms: Option<i64>,
 ) -> Option<M1Columns> {
-    let mut it = server.stream_m1_windowed(symbol, Some(from_ms), Some(to_ms))?;
+    let mut it = server.stream_m1_windowed(symbol, from_ms, to_ms)?;
     let mut bars: Vec<M1Parsed> = Vec::new();
     // M1Parsed is Copy; &Arc<[M1Parsed]> derefs to &[M1Parsed] in arg position.
     while let Some(chunk) = it.next_chunk() {
diff --git a/crates/aura-ingest/tests/real_bars.rs b/crates/aura-ingest/tests/real_bars.rs
index 38ce5ff..cadce75 100644
--- a/crates/aura-ingest/tests/real_bars.rs
+++ b/crates/aura-ingest/tests/real_bars.rs
@@ -90,7 +90,7 @@ fn sample_strategy_runs_over_real_m1_bars_deterministically() {
     let (from_ms, to_ms) = (1_154_390_400_000_i64, 1_157_068_799_999_i64);
 
     let load = || {
-        load_m1_window(&server, "AAPL.US", from_ms, to_ms)
+        load_m1_window(&server, "AAPL.US", Some(from_ms), Some(to_ms))
             .expect("AAPL.US has data in the 2006-08 window")
             .close_stream()
     };