diff --git a/v2ecoli/composites/ecoli_baseline.py b/v2ecoli/composites/ecoli_baseline.py
index 382377cd8..7b3075896 100644
--- a/v2ecoli/composites/ecoli_baseline.py
+++ b/v2ecoli/composites/ecoli_baseline.py
@@ -129,7 +129,7 @@ def _listener_leaf_paths(listeners: dict, *, prefix: str = "listeners"):
 
 
 def _single_cell_xarray_config(*, out_uri: str, metadata: dict | None = None,
-                                buffer_size: int = 3) -> dict:
+                                buffer_size: int = 600) -> dict:
     """Build the STATIC XArrayEmitter ``config`` skeleton for a single-cell,
     agent-relative, in-document capture.
 
@@ -162,7 +162,9 @@ def _single_cell_xarray_config(*, out_uri: str, metadata: dict | None = None,
         out_uri: zarr store path/URI.
         metadata: non-empty run-identity metadata (experiment_id / variant /
             lineage_seed). Falls back to a non-empty placeholder if omitted.
-        buffer_size: transducer buffer size (streaming, bounded). Default 3.
+        buffer_size: transducer buffer size (streaming, bounded), in emit steps.
+            Default 600 — matches the viva-emitters library default; flushes a
+            handful of times per generation rather than every few steps.
 
     Returns:
         The static XArrayEmitter config skeleton (no ``view`` /
diff --git a/v2ecoli/library/vivarium_ecoli_engine.py b/v2ecoli/library/vivarium_ecoli_engine.py
index b9a3fc5f8..d881eef69 100644
--- a/v2ecoli/library/vivarium_ecoli_engine.py
+++ b/v2ecoli/library/vivarium_ecoli_engine.py
@@ -802,7 +802,9 @@ def run_vivarium_ecoli_pbg_multigen(
         em = _build_emitter(
             core=core, store_path=store_path, view=view, metadata_base=metadata_base,
             generation=gen + 1,  # 1-indexed to match run_multigen_xarray (v2ecoli side)
-            agent_id=partition_agent_id, output_metadata={}, buffer_size=3)
+            # Inherit build_emitter_config's buffer_size default (600): flush a
+            # handful of times per generation, not every few steps.
+            agent_id=partition_agent_id, output_metadata={})
 
         steps = 1
         divided = False
diff --git a/v2ecoli/library/xarray_run.py b/v2ecoli/library/xarray_run.py
index a9d58fb9a..69672336c 100644
--- a/v2ecoli/library/xarray_run.py
+++ b/v2ecoli/library/xarray_run.py
@@ -386,7 +386,7 @@ def build_emitter_config(
     metadata_base: dict,
     generation: int,
     agent_id: str,
-    buffer_size: int = 4,
+    buffer_size: int = 600,
     output_metadata: dict | None = None,
     writer: dict | None = None,
     predicate: list | None = None,
@@ -466,7 +466,7 @@ def run_multigen_xarray(
     chunk: int = 60,
     initial_agent_id: str = "0",
     overwrite: bool = True,
-    buffer_size: int = 3,
+    buffer_size: int = 600,
     single_daughters: bool = False,
     division_detector: Callable[[set[str], set[str]], tuple[bool, str | None]] | None = None,
     provenance: dict | None = None,
@@ -485,12 +485,17 @@ def run_multigen_xarray(
       chunk: how many ticks between emitter updates.
       initial_agent_id: agent_id to start following.
       overwrite: if True, delete ``store_path`` before starting.
-      buffer_size: XArrayEmitter transducer buffer size. Default 3 (NOT the
-        config builder's 4): the installed pbg-emitters trips an
-        ``assert not include_static`` in its ``flush(final=True)`` path when the
-        buffer is exactly full at close (i.e. ``n_updates % buffer_size == 0``);
-        3 is the value the single-generation runner uses to dodge it. Override
-        only if you know the emit count won't land on a multiple of it.
+      buffer_size: XArrayEmitter transducer buffer size, in *emit steps*, held
+        in memory before each flush to the zarr store. Default 600, matching the
+        viva-emitters library default — sized to flush only a handful of times
+        per generation (see :py:class:`viva_emitters.xarray_emitter.transducer.
+        XarrayTransducer`). A tiny buffer (the old default of 3) forces a flush
+        every few emit steps, degrading latency and compression by ~2 orders of
+        magnitude; it was originally chosen to dodge a ``flush(final=True)``
+        assertion in an early vendored emitter, which current viva-emitters has
+        since fixed (the buffer-full/partial/aligned close paths are all
+        regression-tested). The ``except AssertionError`` guards around the
+        closes below are now belt-and-suspenders against that fixed quirk.
       division_detector: optional ``(prev_ids, curr_ids) -> (divided?, daughter_id|None)``.
         Default: detect division when ``len(curr) > len(prev)`` and pick the
         first new agent_id sorted.
diff --git a/v2ecoli/workflow/lineage.py b/v2ecoli/workflow/lineage.py
index 56caf5ab8..184a08bd1 100644
--- a/v2ecoli/workflow/lineage.py
+++ b/v2ecoli/workflow/lineage.py
@@ -270,7 +270,10 @@ def _open_xarray_emitter(self, emit_cell):
         raw_view = [dict(e, root=tuple(e["root"])) for e in raw_view]
         transducer = arg.get("transducer") or {}
         buf = ((transducer.get("buffer") or {}).get("size"))
-        buf = max(3, int(buf or 4))  # transducer requires buffer.size > 2
+        # Default 600 (viva-emitters library default: a handful of flushes per
+        # generation, not one every few steps); floor 3 since the transducer
+        # requires buffer.size > 2.
+        buf = max(3, int(buf or 600))
         predicate = transducer.get("predicate")
         writer = arg.get("writer")
         out_dir = arg.get("out_dir") or self.config["out_dir"]