d-v-b · Oct 8, 2026 · Oct 8, 2026 · Oct 8, 2026 · Oct 9, 2026 · Oct 9, 2026
diff --git a/.github/workflows/downstream.yml b/.github/workflows/downstream.yml
@@ -68,13 +68,16 @@ jobs:
           import xarray; print(f'xarray {xarray.__version__}')
           "
 
-      - name: Run xarray zarr backend tests
+      # xarray keeps its backend tests in the `xarray/tests/backends` package
+      # (pydata/xarray#11633 split the former `test_backends*.py` modules into
+      # it). Running the package covers the zarr store, region/append, API and
+      # DataTree tests; the other backends are installed by the `io` extra, so
+      # their tests run too, as they did before the split.
+      - name: Run xarray backend tests
         working-directory: xarray
         run: |
           uv run --no-sync python -m pytest --no-header -q \
-            xarray/tests/test_backends.py \
-            xarray/tests/test_backends_api.py \
-            xarray/tests/test_backends_datatree.py
+            xarray/tests/backends
 
   numcodecs:
     name: numcodecs zarr3 codec tests

diff --git a/.github/workflows/issue-metrics.yml b/.github/workflows/issue-metrics.yml
@@ -33,7 +33,7 @@ jobs:
         echo "last_month=$first_day..$last_day" >> "$GITHUB_ENV"
 
     - name: Run issue-metrics tool
-      uses: github-community-projects/issue-metrics@a7dc2fb675661e208d4fc6fa321a6b95fc4a06f9 # v5.0.2
+      uses: github-community-projects/issue-metrics@671528652402b9b8a33da44b5c693b3161bc090f # v5.0.3
       env:
         GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         SEARCH_QUERY: 'repo:zarr-developers/zarr-python is:issue created:${{ env.last_month }} -reason:"not planned"'

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
@@ -17,7 +17,7 @@ default_language_version:
 
 repos:
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.16.6
+    rev: v0.16.10
     hooks:
       - id: ruff-check
         args: ["--fix", "--show-fixes"]
@@ -34,7 +34,7 @@ repos:
         exclude: mkdocs.yml
       - id: trailing-whitespace
   - repo: https://github.com/DavidAnson/markdownlint-cli2
-    rev: v0.23.2
+    rev: v0.23.3
     hooks:
       # Markdown structure/hygiene. Rule selection and ignores are in
       # .markdownlint-cli2.jsonc; complements ci/lint_docs.py (RST residue,
@@ -76,7 +76,7 @@ repos:
     hooks:
       - id: sp-repo-review
   - repo: https://github.com/numpy/numpydoc
-    rev: v1.11.0rc0
+    rev: v1.11.0
     hooks:
       - id: numpydoc-validation
   - repo: local
@@ -89,7 +89,7 @@ repos:
         types: [python]
         files: ^(src|tests)/
   - repo: https://github.com/zizmorcore/zizmor-pre-commit
-    rev: v1.30.0
+    rev: v1.30.1
     hooks:
       - id: zizmor
   - repo: https://github.com/twisted/towncrier

diff --git a/changes/3850.doc.md b/changes/3850.doc.md
@@ -0,0 +1 @@
+Document the removal of `LRUStoreCache` in the v3 migration guide, and point to the experimental `zarr.experimental.cache_store.CacheStore` as its replacement.
diff --git a/changes/404.bugfix.md b/changes/404.bugfix.md
@@ -0,0 +1 @@
+A stored fill value for the `bool` data type must now be a JSON boolean, or, in Zarr format 2, the integer `0` or `1`. Previously any JSON value was read by its truthiness, so `"false"` was read as `True` and, in Zarr format 3, `null` as `False`. Other values now raise `TypeError`.
diff --git a/changes/4051.doc.md b/changes/4051.doc.md
@@ -0,0 +1,6 @@
+Added a deprecation policy to the contributing guide. It defines when a
+deprecation cycle is required for public API changes, a shared framework for
+deciding whether a removal is worthwhile, the mechanics a deprecation must
+follow (warning class, message contents, documentation, and changelog entry),
+and a minimum deprecation period of at least 6 months and at least one minor
+release before removal.
diff --git a/changes/4334.bugfix.md b/changes/4334.bugfix.md
diff --git a/changes/4340.bugfix.md b/changes/4340.bugfix.md
diff --git a/changes/4342.bugfix.md b/changes/4342.bugfix.md
diff --git a/changes/4344.bugfix.md b/changes/4344.bugfix.md
@@ -0,0 +1,8 @@
+Resizing an array with `delete_outside_chunks=True` now generates only the
+out-of-bounds chunk coordinates and deletes them with a bounded pool of
+workers, instead of materializing the entire old and new grids and all
+deletion tasks. This bounds auxiliary memory during shrinking and mixed
+growing/shrinking resizes while preserving retained chunks. Growing, or
+shrinking within the last chunk of each axis, no longer schedules any
+deletion work. When a deletion fails, the remaining deletions are now
+cancelled before the error is raised; previously they ran to completion.
diff --git a/changes/4353.bugfix.md b/changes/4353.bugfix.md
diff --git a/changes/4356.bugfix.md b/changes/4356.bugfix.md
diff --git a/changes/4363.bugfix.md b/changes/4363.bugfix.md
diff --git a/changes/4368.misc.md b/changes/4368.misc.md
diff --git a/changes/4372.misc.md b/changes/4372.misc.md
diff --git a/changes/4375.bugfix.md b/changes/4375.bugfix.md
diff --git a/changes/4376.bugfix.md b/changes/4376.bugfix.md
diff --git a/changes/4377.misc.md b/changes/4377.misc.md
diff --git a/changes/4381.bugfix.md b/changes/4381.bugfix.md
diff --git a/changes/4382.bugfix.md b/changes/4382.bugfix.md
diff --git a/changes/4385.bugfix.md b/changes/4385.bugfix.md
diff --git a/changes/4387.bugfix.md b/changes/4387.bugfix.md
diff --git a/changes/4391.bugfix.md b/changes/4391.bugfix.md
diff --git a/changes/4392.misc.md b/changes/4392.misc.md
diff --git a/changes/4397.bugfix.md b/changes/4397.bugfix.md
diff --git a/changes/4402.bugfix.md b/changes/4402.bugfix.md
diff --git a/changes/4407.misc.md b/changes/4407.misc.md
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Document the removal of `LRUStoreCache` in the v3 migration guide, and point to the experimental `zarr.experimental.cache_store.CacheStore` as its replacement.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		A stored fill value for the `bool` data type must now be a JSON boolean, or, in Zarr format 2, the integer `0` or `1`. Previously any JSON value was read by its truthiness, so `"false"` was read as `True` and, in Zarr format 3, `null` as `False`. Other values now raise `TypeError`.