diff --git a/CHANGELOG.md b/CHANGELOG.md
index cd8e457b..2568cd0b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -29,7 +29,7 @@ All notable changes to this project will be documented in this file.
     * [Full changelog: 1.2.0...1.3.0](https://github.com/ni/nidaqmx-python/compare/1.2.0...1.3.0)
 
 * ### Resolved Issues
-    * ...
+    * [843: read methods use task.in_stream.channels_to_read, which is slow](https://github.com/ni/nidaqmx-python/issues/843)
 
 * ### Major Changes
     * (IN PROGRESS behind "WAVEFORM_SUPPORT" feature toggle) Added support for reading and writing Waveform data. 
diff --git a/generated/nidaqmx/stream_readers/_channel_reader_base.py b/generated/nidaqmx/stream_readers/_channel_reader_base.py
index ba0300bb..2b7ad00d 100644
--- a/generated/nidaqmx/stream_readers/_channel_reader_base.py
+++ b/generated/nidaqmx/stream_readers/_channel_reader_base.py
@@ -56,8 +56,7 @@ def _verify_array(self, data, number_of_samples_per_channel, is_many_chan, is_ma
         if not self._verify_array_shape:
             return
 
-        channels_to_read = self._in_stream.channels_to_read
-        number_of_channels = len(channels_to_read.channel_names)
+        number_of_channels = self._in_stream.num_chans
 
         array_shape: tuple[int, ...] | None = None
         if is_many_chan:
@@ -100,8 +99,7 @@ def _verify_array_digital_lines(self, data, is_many_chan, is_many_line):
         if not self._verify_array_shape:
             return
 
-        channels_to_read = self._in_stream.channels_to_read
-        number_of_channels = len(channels_to_read.channel_names)
+        number_of_channels = self._in_stream.num_chans
         number_of_lines = self._in_stream.di_num_booleans_per_chan
 
         array_shape: tuple[int, ...] | None = None
diff --git a/generated/nidaqmx/stream_writers/_channel_writer_base.py b/generated/nidaqmx/stream_writers/_channel_writer_base.py
index f631a220..93a00d59 100644
--- a/generated/nidaqmx/stream_writers/_channel_writer_base.py
+++ b/generated/nidaqmx/stream_writers/_channel_writer_base.py
@@ -93,8 +93,7 @@ def _verify_array(self, data, is_many_chan, is_many_samp):
         if not self._verify_array_shape:
             return
 
-        channels_to_write = self._task.channels
-        number_of_channels = len(channels_to_write.channel_names)
+        number_of_channels = self._out_stream.num_chans
 
         expected_num_dimensions = None
         if is_many_chan:
@@ -130,8 +129,7 @@ def _verify_array_digital_lines(self, data, is_many_chan, is_many_line):
         if not self._verify_array_shape:
             return
 
-        channels_to_write = self._task.channels
-        number_of_channels = len(channels_to_write.channel_names)
+        number_of_channels = self._out_stream.num_chans
         number_of_lines = self._out_stream.do_num_booleans_per_chan
 
         expected_num_dimensions = None
diff --git a/src/handwritten/stream_readers/_channel_reader_base.py b/src/handwritten/stream_readers/_channel_reader_base.py
index ba0300bb..2b7ad00d 100644
--- a/src/handwritten/stream_readers/_channel_reader_base.py
+++ b/src/handwritten/stream_readers/_channel_reader_base.py
@@ -56,8 +56,7 @@ def _verify_array(self, data, number_of_samples_per_channel, is_many_chan, is_ma
         if not self._verify_array_shape:
             return
 
-        channels_to_read = self._in_stream.channels_to_read
-        number_of_channels = len(channels_to_read.channel_names)
+        number_of_channels = self._in_stream.num_chans
 
         array_shape: tuple[int, ...] | None = None
         if is_many_chan:
@@ -100,8 +99,7 @@ def _verify_array_digital_lines(self, data, is_many_chan, is_many_line):
         if not self._verify_array_shape:
             return
 
-        channels_to_read = self._in_stream.channels_to_read
-        number_of_channels = len(channels_to_read.channel_names)
+        number_of_channels = self._in_stream.num_chans
         number_of_lines = self._in_stream.di_num_booleans_per_chan
 
         array_shape: tuple[int, ...] | None = None
diff --git a/src/handwritten/stream_writers/_channel_writer_base.py b/src/handwritten/stream_writers/_channel_writer_base.py
index f631a220..93a00d59 100644
--- a/src/handwritten/stream_writers/_channel_writer_base.py
+++ b/src/handwritten/stream_writers/_channel_writer_base.py
@@ -93,8 +93,7 @@ def _verify_array(self, data, is_many_chan, is_many_samp):
         if not self._verify_array_shape:
             return
 
-        channels_to_write = self._task.channels
-        number_of_channels = len(channels_to_write.channel_names)
+        number_of_channels = self._out_stream.num_chans
 
         expected_num_dimensions = None
         if is_many_chan:
@@ -130,8 +129,7 @@ def _verify_array_digital_lines(self, data, is_many_chan, is_many_line):
         if not self._verify_array_shape:
             return
 
-        channels_to_write = self._task.channels
-        number_of_channels = len(channels_to_write.channel_names)
+        number_of_channels = self._out_stream.num_chans
         number_of_lines = self._out_stream.do_num_booleans_per_chan
 
         expected_num_dimensions = None