diff --git a/crates/streams/src/timebin/cached/reader.rs b/crates/streams/src/timebin/cached/reader.rs
index b554ad9..ec15ffd 100644
--- a/crates/streams/src/timebin/cached/reader.rs
+++ b/crates/streams/src/timebin/cached/reader.rs
@@ -1,5 +1,6 @@
 use err::thiserror;
 use err::ThisError;
+use futures_util::FutureExt;
 use futures_util::Stream;
 use items_2::binsdim0::BinsDim0;
 use netpod::BinnedRange;
@@ -14,6 +15,14 @@ pub struct Reading {
     fut: Pin<Box<dyn Future<Output = Result<BinsDim0<f32>, Box<dyn std::error::Error>>> + Send>>,
 }
 
+impl Future for Reading {
+    type Output = Result<BinsDim0<f32>, Box<dyn std::error::Error>>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
+        self.fut.poll_unpin(cx)
+    }
+}
+
 pub trait CacheReadProvider: Send {
     fn read(&self) -> Reading;
 }
diff --git a/crates/streams/src/timebin/fromlayers.rs b/crates/streams/src/timebin/fromlayers.rs
index 24fdeb3..3ed6246 100644
--- a/crates/streams/src/timebin/fromlayers.rs
+++ b/crates/streams/src/timebin/fromlayers.rs
@@ -52,12 +52,6 @@ impl TimeBinnedFromLayers {
             range,
             bin_len_layers
         );
-        // cases:
-        // if this bin_len is a cachable bin_len:
-        // - have to attempt to read from cache.
-        // expect to read bins in a stream (randomize to small max len for testing).
-        // also, if this bin_len is a cachable bin_len:
-        // must produce bins missing in cache from separate stream.
         let bin_len = DtMs::from_ms_u64(range.bin_len.ms());
         if bin_len_layers.contains(&bin_len) {
             info!("{}::new  bin_len in layers", Self::type_name());
diff --git a/crates/streams/src/timebin/gapfill.rs b/crates/streams/src/timebin/gapfill.rs
index 3628254..4703c54 100644
--- a/crates/streams/src/timebin/gapfill.rs
+++ b/crates/streams/src/timebin/gapfill.rs
@@ -64,6 +64,7 @@ impl Stream for GapFill {
         //     It does not attempt to read the given bin-len from a cache, because we just did attempt that.
         //     It still requires that bin-len is cacheable. (NO! it must work with the layering that I passed!)
         //     Then it finds the next cacheable
-        Ready(None)
+        // Ready(None)
+        todo!("poll the already created cached reader, detect and fill in gaps, send off to cache-write")
     }
 }