From 324a2cd2e2f3a2c23ceced8cae24107976ddbb6d Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 10:49:12 -0400
Subject: [PATCH 01/11] ci(python): run full mutation inventory across shards

---
 .github/workflows/ci.yml             |  44 ++++++++--
 .github/workflows/mutation-audit.yml |   2 +-
 maintainers/mutation-testing.md      |  24 ++---
 maintainers/quality-policy.lock.json |   1 -
 pyproject.toml                       |   1 -
 scripts/check_quality_policy.py      |   2 +-
 scripts/mutation.sh                  | 110 ++++++++++++-----------
 tests/unit/test_mutation_results.py  | 126 +++++++++++++++++++++++----
 8 files changed, 215 insertions(+), 95 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 041345b8..06e59e9c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -58,16 +58,36 @@ jobs:
             reports/hypothesis/seed.txt
           if-no-files-found: ignore
 
-  mutation:
-    name: Mutation Gate
+  mutation-plan:
+    name: Mutation inventory
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      contents: read
+    outputs:
+      shards: ${{ steps.plan.outputs.shards }}
+    steps:
+      - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          persist-credentials: false
+      - name: Inventory every handwritten runtime module
+        id: plan
+        run: echo "shards=$(bash scripts/mutation.sh --matrix)" >> "$GITHUB_OUTPUT"
+
+  mutation-shard:
+    name: Mutation shard (${{ matrix.shard }})
+    needs: mutation-plan
     runs-on: ubuntu-latest
     timeout-minutes: 40
     permissions:
       contents: read
+    strategy:
+      fail-fast: false
+      matrix:
+        shard: ${{ fromJSON(needs.mutation-plan.outputs.shards) }}
     steps:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
-          fetch-depth: 0
           persist-credentials: false
       - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
         with:
@@ -76,18 +96,30 @@ jobs:
         with:
           version: "0.12.17"
       - run: uv sync --locked
-      - name: Mutate changed and critical runtime modules
+      - name: Mutate assigned runtime modules
         env:
-          MUTATION_BASE_SHA: ${{ github.event.pull_request.base.sha || github.event.merge_group.base_sha || github.event.before }}
+          MUTATION_SHARD: ${{ matrix.shard }}
         run: uv run --locked poe mutation
       - name: Preserve mutation outcomes
         if: ${{ always() }}
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
-          name: mutation-outcomes
+          name: mutation-outcomes-${{ matrix.shard }}
           path: reports/mutation.json
           if-no-files-found: error
 
+  mutation:
+    name: Mutation Gate
+    if: ${{ always() }}
+    needs: [mutation-plan, mutation-shard]
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - name: Require every mutation shard to succeed
+        env:
+          RESULTS: ${{ toJSON(needs.*.result) }}
+        run: jq -e 'length == 2 and all(. == "success")' <<< "$RESULTS"
+
   quality:
     name: Quality Gate
     if: ${{ always() }}
diff --git a/.github/workflows/mutation-audit.yml b/.github/workflows/mutation-audit.yml
index 92b9b1a2..3c504c07 100644
--- a/.github/workflows/mutation-audit.yml
+++ b/.github/workflows/mutation-audit.yml
@@ -25,7 +25,7 @@ jobs:
         with:
           version: "0.12.17"
       - run: uv sync --locked
-      - run: uv run --locked poe mutation-full
+      - run: uv run --locked poe mutation
       - name: Preserve mutation outcomes
         if: ${{ always() }}
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
diff --git a/maintainers/mutation-testing.md b/maintainers/mutation-testing.md
index db16609c..a4714d5e 100644
--- a/maintainers/mutation-testing.md
+++ b/maintainers/mutation-testing.md
@@ -1,16 +1,18 @@
 # Mutation testing
 
-`uv run --locked poe quality` runs all native checks and mutates every changed
-handwritten runtime module plus the lock acquisition, guard, renewal, and worker
-modules. CI uses the same `checks` and `mutation` tasks in separate jobs, then
-requires both through `Quality Gate`. The weekly `poe mutation-full` task audits
-every handwritten runtime module without a debt baseline.
+`uv run --locked poe quality` runs all native checks and mutates every
+handwritten runtime module. CI runs the same `checks` and `mutation` tasks,
+distributing the mutation task across eight independent jobs. Git's current
+handwritten module inventory determines their assignments: each module appears
+in exactly one shard, including a newly added module. `Mutation Gate` requires
+every shard, and `Quality Gate` requires it and the Python test matrix. The
+weekly audit runs the same full mutation task without a debt baseline.
 
 Mutmut's [native configuration](https://mutmut.readthedocs.io/en/latest/) lives
 in `pyproject.toml`; it excludes only the generated OpenAPI client. Mutmut can
-select modules by name but has no Git-changed-module option and returns success
-when mutants survive. `scripts/mutation.sh` selects module names from Git and
-`scripts/mutation_results.py` reads only those modules' native metadata. The
+select modules by name but returns success when mutants survive.
+`scripts/mutation.sh` selects the full handwritten inventory from Git and
+`scripts/mutation_results.py` reads each selected module's native metadata. The
 report at `reports/mutation.json` distinguishes killed, statically invalid,
 surviving, uncovered, timed-out, crashed, interrupted, and missing results.
 A pytest internal error is a harness crash, not a killed mutant.
@@ -32,9 +34,9 @@ macOS system-proxy discovery can abort after a fork with active threads.
 The pinned pytest-order plugin runs bounded callback and presence assertions
 first when mutmut's unordered test selection could otherwise reach a blocked test.
 
-The full audit runs mutmut once across the entire source tree. It reports any
-surviving mutants without treating them as an approved baseline. Equivalent
-mutants require a reviewed, exact exception before a gate can accept them.
+The local and weekly full runs execute the inventory in one Mutmut process.
+Equivalent mutants require a reviewed, exact exception before a gate can
+accept them.
 
 Ruff, Mypy, Basedpyright, pytest, and Tox tasks pass `pyproject.toml`
 explicitly. Their documented config-file precedence can otherwise select a
diff --git a/maintainers/quality-policy.lock.json b/maintainers/quality-policy.lock.json
index 54d94fc7..8edde883 100644
--- a/maintainers/quality-policy.lock.json
+++ b/maintainers/quality-policy.lock.json
@@ -400,7 +400,6 @@
         "generated": "python -m scripts.check_openapi",
         "lint": "ruff check --config pyproject.toml .",
         "mutation": "bash scripts/mutation.sh",
-        "mutation-full": "MUTATION_FULL=1 bash scripts/mutation.sh",
         "mypy": "mypy --config-file pyproject.toml",
         "package-check": {
           "interpreter": "bash",
diff --git a/pyproject.toml b/pyproject.toml
index d012d250..b065e1e4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -498,7 +498,6 @@ types = ["mypy", "basedpyright"]
 mypy = "mypy --config-file pyproject.toml"
 basedpyright = "basedpyright --project pyproject.toml"
 mutation = "bash scripts/mutation.sh"
-mutation-full = "MUTATION_FULL=1 bash scripts/mutation.sh"
 
 [tool.poe.tasks.test]
 interpreter = "bash"
diff --git a/scripts/check_quality_policy.py b/scripts/check_quality_policy.py
index 784e2d51..b0995497 100644
--- a/scripts/check_quality_policy.py
+++ b/scripts/check_quality_policy.py
@@ -18,7 +18,7 @@
     from collections.abc import Iterable
 
 GENERATED = "src/volcano_sdk/_generated"
-LOCK_SHA256 = "489b1a41632f67d528dbb10267bb8921c38c78726c430d990b4ee99ebdd9236a"
+LOCK_SHA256 = "745adb5bd5f0168512fe5035a66006082bf02fb32ce97a945958d19284b7e4f6"
 TYPE_FIXTURES = {
     "tests/typing/contract_steps.py",
     "tests/typing/durable_callbacks.py",
diff --git a/scripts/mutation.sh b/scripts/mutation.sh
index d05e3ae7..560e512b 100644
--- a/scripts/mutation.sh
+++ b/scripts/mutation.sh
@@ -4,71 +4,69 @@ set -euo pipefail
 # Forked macOS workers must not query SystemConfiguration through urllib/httpx.
 export NO_PROXY='*' no_proxy='*'
 
-# Refresh mutmut's test-to-mutant map so newly added tests are selected.
-rm -rf -- mutants
+shard_count=8
+paths=()
+while IFS= read -r -d '' path; do
+  if [[ $path == src/volcano_sdk/*.py && $path != src/volcano_sdk/_generated/* && -f $path ]]; then
+    paths+=("$path")
+  fi
+done < <(git ls-files --cached --others --exclude-standard -z -- src/volcano_sdk)
 
-mkdir -p reports
-targets=reports/mutation-targets.bin
-failed=reports/mutation-failed.bin
-: > "$targets"
-: > "$failed"
+if (( ${#paths[@]} == 0 )); then
+  echo 'No handwritten SDK runtime modules found' >&2
+  exit 1
+fi
 
-modules=()
-add_module() {
-  for known in "${modules[@]-}"; do
-    [[ $known == "$1" ]] && return
-  done
-  modules+=("$1")
-}
-if [[ ${MUTATION_FULL:-0} == 1 ]]; then
-  git ls-files -z 'src/volcano_sdk/*.py' > reports/mutation-source.bin
-  while IFS= read -r -d '' path; do
-    if [[ $path != src/volcano_sdk/_generated/* && -f $path ]]; then
-      add_module "$path"
-    fi
-  done < reports/mutation-source.bin
-else
-  for path in \
-    src/volcano_sdk/locks.py \
-    src/volcano_sdk/_lock_guard.py \
-    src/volcano_sdk/_lock_renewer.py \
-    src/volcano_sdk/_lock_worker.py; do
-    add_module "$path"
+if [[ ${1:-} == --matrix && $# == 1 ]]; then
+  printf '['
+  for ((shard = 0; shard < shard_count; shard++)); do
+    ((shard == 0)) || printf ','
+    printf '%s' "$shard"
   done
+  printf ']\n'
+  exit
+fi
+if (( $# != 0 )); then
+  echo 'Usage: scripts/mutation.sh [--matrix]' >&2
+  exit 2
+fi
 
-  base=${MUTATION_BASE_SHA:-origin/main}
-  ancestor=$(git merge-base "$base" HEAD)
-  changed() {
-    git diff --name-only --diff-filter=ACMRT -z "$ancestor" HEAD
-    git diff --name-only --diff-filter=ACMRT -z HEAD
-    git ls-files -z --others --exclude-standard
-  }
-  changed > reports/mutation-changed.bin
-  while IFS= read -r -d '' path; do
-    if [[ $path == src/volcano_sdk/*.py && $path != src/volcano_sdk/_generated/* && -f $path ]]; then
-      add_module "$path"
-    fi
-  done < reports/mutation-changed.bin
+if [[ -n ${MUTATION_SHARD:-} ]]; then
+  if [[ ! $MUTATION_SHARD =~ ^(0|[1-9][0-9]*)$ ]] || (( MUTATION_SHARD >= shard_count )); then
+    echo "Invalid mutation shard: $MUTATION_SHARD" >&2
+    exit 2
+  fi
 fi
 
-for path in "${modules[@]}"; do
+mkdir -p reports
+targets=reports/mutation-targets.bin
+failed=reports/mutation-failed.bin
+: > "$targets"
+: > "$failed"
+patterns=()
+for index in "${!paths[@]}"; do
+  if [[ -n ${MUTATION_SHARD:-} ]] && (( index % shard_count != MUTATION_SHARD )); then
+    continue
+  fi
+  path=${paths[$index]}
   printf '%s\0' "$path" >> "$targets"
+  module=${path#src/}
+  module=${module%.py}
+  if [[ $module == */__init__ ]]; then
+    module=${module%/__init__}
+  fi
+  patterns+=("${module//\//.}.x*")
 done
 
-if [[ ${MUTATION_FULL:-0} == 1 ]]; then
-  if ! mutmut run --max-children 1; then
-    printf '%s\0' "full mutation run" >> "$failed"
-  fi
-else
-  patterns=()
-  for path in "${modules[@]}"; do
-    module=${path#src/}
-    module=${module%.py}
-    patterns+=("${module//\//.}.x*")
-  done
-  if ! mutmut run --max-children 1 "${patterns[@]}"; then
-    printf '%s\0' "scoped mutation run" >> "$failed"
-  fi
+if (( ${#patterns[@]} == 0 )); then
+  echo 'Selected mutation shard has no runtime modules' >&2
+  exit 1
+fi
+
+# A fresh run must not inherit stale test-to-mutant mappings or verdicts.
+rm -rf -- mutants
+if ! mutmut run --max-children 1 "${patterns[@]}"; then
+  printf '%s\0' 'mutation run' >> "$failed"
 fi
 
 python -m scripts.mutation_results "$targets" "$failed"
diff --git a/tests/unit/test_mutation_results.py b/tests/unit/test_mutation_results.py
index 626a5c08..908c093a 100644
--- a/tests/unit/test_mutation_results.py
+++ b/tests/unit/test_mutation_results.py
@@ -15,14 +15,17 @@
 PROJECT = Path(__file__).parents[2]
 
 
-def test_scoped_mutation_excludes_prefix_sibling_module(
-    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+def mutation_harness(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, modules: list[str]
 ) -> None:
-    source = tmp_path / "src/volcano_sdk/durable.py"
-    source.parent.mkdir(parents=True)
-    _ = source.write_text("def durable() -> bool: return True\n", encoding="utf-8")
-    sibling = source.with_name("durable_authoring.py")
-    _ = sibling.write_text("def authoring() -> bool: return True\n", encoding="utf-8")
+    """Install shell stubs for testing the native Mutmut selector."""
+    for module in modules:
+        source = tmp_path / module
+        source.parent.mkdir(parents=True, exist_ok=True)
+        _ = source.write_text("def probe() -> bool: return True\n", encoding="utf-8")
+    _ = (tmp_path / "git-paths.bin").write_bytes(
+        b"\0".join(module.encode() for module in modules) + b"\0"
+    )
     scripts = tmp_path / "scripts"
     scripts.mkdir()
     _ = (scripts / "mutation.sh").write_bytes(
@@ -31,12 +34,7 @@ def test_scoped_mutation_excludes_prefix_sibling_module(
     bin_dir = tmp_path / "bin"
     bin_dir.mkdir()
     stubs = {
-        "git": """#!/bin/sh
-case "$1" in
-  merge-base) printf 'base\\n' ;;
-  diff) printf 'src/volcano_sdk/durable.py\\0' ;;
-esac
-""",
+        "git": "#!/bin/sh\ncat git-paths.bin\n",
         "mutmut": "#!/bin/sh\nprintf '%s\\n' \"$@\" > mutation-args.txt\n",
         "python": "#!/bin/sh\nexit 0\n",
     }
@@ -46,7 +44,15 @@ def test_scoped_mutation_excludes_prefix_sibling_module(
         stub.chmod(0o755)
     monkeypatch.setenv("PATH", f"{bin_dir}:{os.environ['PATH']}")
 
-    result = subprocess.run(
+
+def run_mutation_script(tmp_path: Path) -> subprocess.CompletedProcess[str]:
+    """Run the mutation orchestrator against the shell stubs.
+
+    Returns:
+        Completed script process.
+
+    """
+    return subprocess.run(
         ["/bin/bash", "scripts/mutation.sh"],
         cwd=tmp_path,
         capture_output=True,
@@ -54,10 +60,94 @@ def test_scoped_mutation_excludes_prefix_sibling_module(
         check=False,
     )
 
-    assert result.returncode == 0, result.stdout + result.stderr
-    arguments = (tmp_path / "mutation-args.txt").read_text(encoding="utf-8")
-    assert "volcano_sdk.durable.x*" in arguments.splitlines()
-    assert "volcano_sdk.durable*" not in arguments.splitlines()
+
+def run_mutation_matrix(tmp_path: Path) -> subprocess.CompletedProcess[str]:
+    """Read the complete CI shard plan.
+
+    Returns:
+        Completed script process.
+
+    """
+    return subprocess.run(
+        ["/bin/bash", "scripts/mutation.sh", "--matrix"],
+        cwd=tmp_path,
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+
+
+def mutant_pattern(module: str) -> str:
+    """Mirror Mutmut's package-init name normalization.
+
+    Returns:
+        Exact function-prefix selector for the module.
+
+    """
+    name = module.removeprefix("src/").removesuffix(".py")
+    return f"{name.removesuffix('/__init__').replace('/', '.')}.x*"
+
+
+def test_mutation_shards_cover_all_handwritten_modules(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    modules = [f"src/volcano_sdk/module_{index}.py" for index in range(8)]
+    modules.extend(
+        [
+            "src/volcano_sdk/__init__.py",
+            "src/volcano_sdk/durable.py",
+            "src/volcano_sdk/durable_authoring.py",
+            "src/volcano_sdk/nested/cache.py",
+            "src/volcano_sdk/nested/__init__.py",
+        ]
+    )
+    generated = "src/volcano_sdk/_generated/wire.py"
+    mutation_harness(tmp_path, monkeypatch, [*modules, generated])
+
+    plan = run_mutation_matrix(tmp_path)
+    assert plan.returncode == 0, plan.stderr
+    assert json.loads(plan.stdout) == list(range(8))
+
+    selected: list[str] = []
+    selected_patterns: list[str] = []
+    for shard in range(8):
+        monkeypatch.setenv("MUTATION_SHARD", str(shard))
+        result = run_mutation_script(tmp_path)
+        assert result.returncode == 0, result.stderr
+        paths = (tmp_path / "reports/mutation-targets.bin").read_bytes().split(b"\0")
+        shard_modules = [os.fsdecode(path) for path in paths if path]
+        selected.extend(shard_modules)
+        patterns = [mutant_pattern(module) for module in shard_modules]
+        selected_patterns.extend(patterns)
+        arguments = (tmp_path / "mutation-args.txt").read_text(encoding="utf-8")
+        assert arguments.splitlines() == ["run", "--max-children", "1", *patterns]
+
+    assert sorted(selected) == sorted(modules)
+    assert len(selected) == len(set(selected))
+    assert "volcano_sdk.durable.x*" in selected_patterns
+    assert "volcano_sdk.durable*" not in selected_patterns
+    assert "volcano_sdk.nested.x*" in selected_patterns
+    assert "volcano_sdk.x*" in selected_patterns
+
+
+def test_empty_mutation_inventory_fails(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    mutation_harness(tmp_path, monkeypatch, [])
+    result = run_mutation_matrix(tmp_path)
+    assert result.returncode == 1
+    assert "No handwritten SDK runtime modules found" in result.stderr
+
+
+@pytest.mark.parametrize("shard", ["8", "-1", "not-a-number"])
+def test_invalid_mutation_shard_fails(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, shard: str
+) -> None:
+    mutation_harness(tmp_path, monkeypatch, ["src/volcano_sdk/probe.py"])
+    monkeypatch.setenv("MUTATION_SHARD", shard)
+    result = run_mutation_script(tmp_path)
+    assert result.returncode == 2
+    assert "Invalid mutation shard" in result.stderr
 
 
 def fixture_report(tmp_path: Path, code: int | None) -> tuple[Path, Path]:

From d823765633ed1484787a45034a89a632fb21526e Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 10:46:18 -0400
Subject: [PATCH 02/11] test: preserve zero-window realtime fetch batching

---
 tests/unit/test_realtime_fetch_lifecycle.py | 33 +++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/tests/unit/test_realtime_fetch_lifecycle.py b/tests/unit/test_realtime_fetch_lifecycle.py
index 9f06716f..ac4b6e7e 100644
--- a/tests/unit/test_realtime_fetch_lifecycle.py
+++ b/tests/unit/test_realtime_fetch_lifecycle.py
@@ -230,3 +230,36 @@ async def test_batch_capacity_and_zero_window_preserve_delivery_order(
         assert [item.record for item in deliver.items] == [{"id": 1}, {"id": 2}]
     finally:
         await worker.abort()
+
+
+async def test_zero_batch_window_keeps_queued_followup_fetches_separate() -> None:
+    first_fetch_started = asyncio.Event()
+    release_first_fetch = asyncio.Event()
+    recording_fetch = RecordingBatchFetch()
+
+    async def fetch(
+        requests: tuple[_PostgresFetchRequest, ...],
+    ) -> tuple[dict[str, int], ...]:
+        if requests[0].row_id == 1:
+            first_fetch_started.set()
+            _ = await release_first_fetch.wait()
+        return await recording_fetch(requests)
+
+    worker = PostgresFetchWorker(
+        fetch,
+        OutcomeRecorder(),
+        queue_limit=3,
+        max_batch_size=3,
+        batch_window_seconds=0,
+    )
+    try:
+        await worker.enqueue(fetch_job(1))
+        _ = await asyncio.wait_for(first_fetch_started.wait(), timeout=1)
+        await worker.enqueue(fetch_job(2))
+        await worker.enqueue(fetch_job(3))
+        release_first_fetch.set()
+        await asyncio.wait_for(worker.close(), timeout=1)
+
+        assert recording_fetch.calls == [(1,), (2,), (3,)]
+    finally:
+        await worker.abort()

From 5f10448fd753d50f4ba3ebcaeab9ce00cf4e8167 Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 11:16:08 -0400
Subject: [PATCH 03/11] ci(python): select every runtime module in mutation
 matrix

---
 .github/workflows/ci.yml             | 20 +++---
 maintainers/mutation-testing.md      | 10 +--
 maintainers/quality-policy.lock.json | 13 +---
 pyproject.toml                       | 12 +---
 scripts/check_quality_policy.py      |  2 +-
 scripts/mutation.sh                  | 46 +++++++-------
 scripts/mutation_results.py          |  2 +-
 tests/unit/test_mutation_results.py  | 91 +++++++++++++++++++++++-----
 8 files changed, 125 insertions(+), 71 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 06e59e9c..5de1e780 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -65,17 +65,19 @@ jobs:
     permissions:
       contents: read
     outputs:
-      shards: ${{ steps.plan.outputs.shards }}
+      modules: ${{ steps.plan.outputs.modules }}
     steps:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           persist-credentials: false
       - name: Inventory every handwritten runtime module
         id: plan
-        run: echo "shards=$(bash scripts/mutation.sh --matrix)" >> "$GITHUB_OUTPUT"
+        run: |
+          modules=$(bash scripts/mutation.sh --matrix)
+          echo "modules=$modules" >> "$GITHUB_OUTPUT"
 
-  mutation-shard:
-    name: Mutation shard (${{ matrix.shard }})
+  mutation-module:
+    name: Mutation module (${{ matrix.module }})
     needs: mutation-plan
     runs-on: ubuntu-latest
     timeout-minutes: 40
@@ -84,7 +86,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        shard: ${{ fromJSON(needs.mutation-plan.outputs.shards) }}
+        module: ${{ fromJSON(needs.mutation-plan.outputs.modules) }}
     steps:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
@@ -98,24 +100,24 @@ jobs:
       - run: uv sync --locked
       - name: Mutate assigned runtime modules
         env:
-          MUTATION_SHARD: ${{ matrix.shard }}
+          MUTATION_MODULE: ${{ matrix.module }}
         run: uv run --locked poe mutation
       - name: Preserve mutation outcomes
         if: ${{ always() }}
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
-          name: mutation-outcomes-${{ matrix.shard }}
+          name: mutation-outcomes-${{ matrix.module }}
           path: reports/mutation.json
           if-no-files-found: error
 
   mutation:
     name: Mutation Gate
     if: ${{ always() }}
-    needs: [mutation-plan, mutation-shard]
+    needs: [mutation-plan, mutation-module]
     runs-on: ubuntu-latest
     timeout-minutes: 5
     steps:
-      - name: Require every mutation shard to succeed
+      - name: Require every mutation module to succeed
         env:
           RESULTS: ${{ toJSON(needs.*.result) }}
         run: jq -e 'length == 2 and all(. == "success")' <<< "$RESULTS"
diff --git a/maintainers/mutation-testing.md b/maintainers/mutation-testing.md
index a4714d5e..93c2b6ab 100644
--- a/maintainers/mutation-testing.md
+++ b/maintainers/mutation-testing.md
@@ -2,10 +2,9 @@
 
 `uv run --locked poe quality` runs all native checks and mutates every
 handwritten runtime module. CI runs the same `checks` and `mutation` tasks,
-distributing the mutation task across eight independent jobs. Git's current
-handwritten module inventory determines their assignments: each module appears
-in exactly one shard, including a newly added module. `Mutation Gate` requires
-every shard, and `Quality Gate` requires it and the Python test matrix. The
+assigning one handwritten module to each independent matrix job. Git's current
+handwritten module inventory determines the jobs, including newly added modules.
+`Mutation Gate` requires every module job, and `Quality Gate` requires it and the Python test matrix. The
 weekly audit runs the same full mutation task without a debt baseline.
 
 Mutmut's [native configuration](https://mutmut.readthedocs.io/en/latest/) lives
@@ -16,7 +15,8 @@ select modules by name but returns success when mutants survive.
 report at `reports/mutation.json` distinguishes killed, statically invalid,
 surviving, uncovered, timed-out, crashed, interrupted, and missing results.
 A pytest internal error is a harness crash, not a killed mutant.
-The pinned Pyrefly check rejects type-invalid realtime and auth mutants before pytest;
+The pinned Pyrefly check covers the handwritten runtime and rejects
+type-invalid mutants before pytest;
 the report counts these as `type_checked`, separately from test-killed mutants.
 Surviving, uncovered, timed-out, crashed, and incomplete mutants still fail.
 Mutmut passes pytest `-x` so a selected test's first assertion failure kills the
diff --git a/maintainers/quality-policy.lock.json b/maintainers/quality-policy.lock.json
index 8edde883..b795e3f4 100644
--- a/maintainers/quality-policy.lock.json
+++ b/maintainers/quality-policy.lock.json
@@ -299,16 +299,9 @@
         "pyrefly",
         "check",
         "--output-format=json",
-        "src/volcano_sdk/realtime.py",
-        "src/volcano_sdk/auth.py",
-        "src/volcano_sdk/storage.py",
-        "src/volcano_sdk/functions.py",
-        "src/volcano_sdk/durable_authoring.py",
-        "src/volcano_sdk/database.py",
-        "src/volcano_sdk/_function_resolution.py",
-        "src/volcano_sdk/_transport.py",
-        "src/volcano_sdk/_session.py",
-        "src/volcano_sdk/_session_operations.py"
+        "--project-excludes",
+        "src/volcano_sdk/_generated/**",
+        "src/volcano_sdk"
       ]
     },
     "mypy": {
diff --git a/pyproject.toml b/pyproject.toml
index b065e1e4..d7ef67f6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -458,16 +458,8 @@ partial_branches = []
 source_paths = ["src/volcano_sdk"]
 type_check_command = [
   "pyrefly", "check", "--output-format=json",
-  "src/volcano_sdk/realtime.py",
-  "src/volcano_sdk/auth.py",
-  "src/volcano_sdk/storage.py",
-  "src/volcano_sdk/functions.py",
-  "src/volcano_sdk/durable_authoring.py",
-  "src/volcano_sdk/database.py",
-  "src/volcano_sdk/_function_resolution.py",
-  "src/volcano_sdk/_transport.py",
-  "src/volcano_sdk/_session.py",
-  "src/volcano_sdk/_session_operations.py",
+  "--project-excludes", "src/volcano_sdk/_generated/**",
+  "src/volcano_sdk",
 ]
 cache_invalidation_files = ["tests/**/*.py"]
 pytest_add_cli_args_test_selection = ["tests/unit"]
diff --git a/scripts/check_quality_policy.py b/scripts/check_quality_policy.py
index b0995497..9b401358 100644
--- a/scripts/check_quality_policy.py
+++ b/scripts/check_quality_policy.py
@@ -18,7 +18,7 @@
     from collections.abc import Iterable
 
 GENERATED = "src/volcano_sdk/_generated"
-LOCK_SHA256 = "745adb5bd5f0168512fe5035a66006082bf02fb32ce97a945958d19284b7e4f6"
+LOCK_SHA256 = "3eea92085dce48f7454bc9e2b82854cc99a8787083da471609ae41da57d75560"
 TYPE_FIXTURES = {
     "tests/typing/contract_steps.py",
     "tests/typing/durable_callbacks.py",
diff --git a/scripts/mutation.sh b/scripts/mutation.sh
index 560e512b..e7876317 100644
--- a/scripts/mutation.sh
+++ b/scripts/mutation.sh
@@ -4,11 +4,28 @@ set -euo pipefail
 # Forked macOS workers must not query SystemConfiguration through urllib/httpx.
 export NO_PROXY='*' no_proxy='*'
 
-shard_count=8
 paths=()
+modules=()
 while IFS= read -r -d '' path; do
   if [[ $path == src/volcano_sdk/*.py && $path != src/volcano_sdk/_generated/* && -f $path ]]; then
+    module=${path#src/}
+    module=${module%.py}
+    if [[ $module == */__init__ ]]; then
+      module=${module%/__init__}
+    fi
+    module=${module//\//.}
+    if [[ ! $module =~ ^[a-zA-Z_][a-zA-Z_0-9]*(\.[a-zA-Z_][a-zA-Z_0-9]*)*$ ]]; then
+      echo "Invalid Python runtime module: $path" >&2
+      exit 1
+    fi
+    for existing in "${modules[@]-}"; do
+      if [[ $module == "$existing" ]]; then
+        echo "Duplicate Python runtime module: $module" >&2
+        exit 1
+      fi
+    done
     paths+=("$path")
+    modules+=("$module")
   fi
 done < <(git ls-files --cached --others --exclude-standard -z -- src/volcano_sdk)
 
@@ -16,12 +33,11 @@ if (( ${#paths[@]} == 0 )); then
   echo 'No handwritten SDK runtime modules found' >&2
   exit 1
 fi
-
 if [[ ${1:-} == --matrix && $# == 1 ]]; then
   printf '['
-  for ((shard = 0; shard < shard_count; shard++)); do
-    ((shard == 0)) || printf ','
-    printf '%s' "$shard"
+  for index in "${!modules[@]}"; do
+    ((index == 0)) || printf ','
+    printf '"%s"' "${modules[$index]}"
   done
   printf ']\n'
   exit
@@ -31,13 +47,6 @@ if (( $# != 0 )); then
   exit 2
 fi
 
-if [[ -n ${MUTATION_SHARD:-} ]]; then
-  if [[ ! $MUTATION_SHARD =~ ^(0|[1-9][0-9]*)$ ]] || (( MUTATION_SHARD >= shard_count )); then
-    echo "Invalid mutation shard: $MUTATION_SHARD" >&2
-    exit 2
-  fi
-fi
-
 mkdir -p reports
 targets=reports/mutation-targets.bin
 failed=reports/mutation-failed.bin
@@ -45,22 +54,17 @@ failed=reports/mutation-failed.bin
 : > "$failed"
 patterns=()
 for index in "${!paths[@]}"; do
-  if [[ -n ${MUTATION_SHARD:-} ]] && (( index % shard_count != MUTATION_SHARD )); then
+  if [[ -n ${MUTATION_MODULE:-} ]] && [[ ${modules[$index]} != "$MUTATION_MODULE" ]]; then
     continue
   fi
   path=${paths[$index]}
   printf '%s\0' "$path" >> "$targets"
-  module=${path#src/}
-  module=${module%.py}
-  if [[ $module == */__init__ ]]; then
-    module=${module%/__init__}
-  fi
-  patterns+=("${module//\//.}.x*")
+  patterns+=("${modules[$index]}.x*")
 done
 
 if (( ${#patterns[@]} == 0 )); then
-  echo 'Selected mutation shard has no runtime modules' >&2
-  exit 1
+  echo "Unknown mutation module: ${MUTATION_MODULE:-}" >&2
+  exit 2
 fi
 
 # A fresh run must not inherit stale test-to-mutant mappings or verdicts.
diff --git a/scripts/mutation_results.py b/scripts/mutation_results.py
index 3c8c774d..d5892e42 100644
--- a/scripts/mutation_results.py
+++ b/scripts/mutation_results.py
@@ -134,7 +134,7 @@ def main(targets_path: Path, failed_path: Path) -> int:
         counts.update(module_counts)
         if empty:
             unmutatable.append(name)
-    if not counts:
+    if not counts and (not targets or len(unmutatable) != len(targets)):
         failures.append("No mutants were tested")
     failures.extend(
         f"{name}: {count} mutant(s)"
diff --git a/tests/unit/test_mutation_results.py b/tests/unit/test_mutation_results.py
index 908c093a..6aac0df7 100644
--- a/tests/unit/test_mutation_results.py
+++ b/tests/unit/test_mutation_results.py
@@ -9,6 +9,7 @@
 from typing import cast
 
 import pytest
+from mutmut.utils.format_utils import get_mutant_name
 
 from scripts.mutation_results import main
 
@@ -34,7 +35,12 @@ def mutation_harness(
     bin_dir = tmp_path / "bin"
     bin_dir.mkdir()
     stubs = {
-        "git": "#!/bin/sh\ncat git-paths.bin\n",
+        "git": (
+            "#!/bin/sh\n"
+            '[ "$*" = \'ls-files --cached --others --exclude-standard '
+            "-z -- src/volcano_sdk' ] || exit 1\n"
+            "cat git-paths.bin\n"
+        ),
         "mutmut": "#!/bin/sh\nprintf '%s\\n' \"$@\" > mutation-args.txt\n",
         "python": "#!/bin/sh\nexit 0\n",
     }
@@ -62,7 +68,7 @@ def run_mutation_script(tmp_path: Path) -> subprocess.CompletedProcess[str]:
 
 
 def run_mutation_matrix(tmp_path: Path) -> subprocess.CompletedProcess[str]:
-    """Read the complete CI shard plan.
+    """Read the complete CI module plan.
 
     Returns:
         Completed script process.
@@ -88,7 +94,31 @@ def mutant_pattern(module: str) -> str:
     return f"{name.removesuffix('/__init__').replace('/', '.')}.x*"
 
 
-def test_mutation_shards_cover_all_handwritten_modules(
+def module_name(path: str) -> str:
+    """Return the Python module selected by the native Mutmut wildcard.
+
+    Returns:
+        Import name for a handwritten Python source file.
+
+    """
+    return mutant_pattern(path).removesuffix(".x*")
+
+
+@pytest.mark.parametrize(
+    ("path", "expected"),
+    [
+        ("src/volcano_sdk/__init__.py", "volcano_sdk.x_probe__mutmut_1"),
+        ("src/volcano_sdk/nested/__init__.py", "volcano_sdk.nested.x_probe__mutmut_1"),
+    ],
+)
+def test_package_init_selector_matches_native_mutmut_name(
+    path: str, expected: str
+) -> None:
+    assert get_mutant_name(Path(path), "x_probe__mutmut_1") == expected
+    assert expected.startswith(mutant_pattern(path).removesuffix("*"))
+
+
+def test_mutation_matrix_covers_all_handwritten_modules(
     tmp_path: Path, monkeypatch: pytest.MonkeyPatch
 ) -> None:
     modules = [f"src/volcano_sdk/module_{index}.py" for index in range(8)]
@@ -106,18 +136,19 @@ def test_mutation_shards_cover_all_handwritten_modules(
 
     plan = run_mutation_matrix(tmp_path)
     assert plan.returncode == 0, plan.stderr
-    assert json.loads(plan.stdout) == list(range(8))
+    assert json.loads(plan.stdout) == [module_name(path) for path in modules]
 
     selected: list[str] = []
     selected_patterns: list[str] = []
-    for shard in range(8):
-        monkeypatch.setenv("MUTATION_SHARD", str(shard))
+    for module in json.loads(plan.stdout):
+        monkeypatch.setenv("MUTATION_MODULE", module)
         result = run_mutation_script(tmp_path)
         assert result.returncode == 0, result.stderr
         paths = (tmp_path / "reports/mutation-targets.bin").read_bytes().split(b"\0")
-        shard_modules = [os.fsdecode(path) for path in paths if path]
-        selected.extend(shard_modules)
-        patterns = [mutant_pattern(module) for module in shard_modules]
+        selected_modules = [os.fsdecode(path) for path in paths if path]
+        assert len(selected_modules) == 1
+        selected.extend(selected_modules)
+        patterns = [mutant_pattern(path) for path in selected_modules]
         selected_patterns.extend(patterns)
         arguments = (tmp_path / "mutation-args.txt").read_text(encoding="utf-8")
         assert arguments.splitlines() == ["run", "--max-children", "1", *patterns]
@@ -139,15 +170,28 @@ def test_empty_mutation_inventory_fails(
     assert "No handwritten SDK runtime modules found" in result.stderr
 
 
-@pytest.mark.parametrize("shard", ["8", "-1", "not-a-number"])
-def test_invalid_mutation_shard_fails(
-    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, shard: str
+def test_duplicate_import_name_fails_inventory(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    mutation_harness(
+        tmp_path,
+        monkeypatch,
+        ["src/volcano_sdk/nested.py", "src/volcano_sdk/nested/__init__.py"],
+    )
+    result = run_mutation_matrix(tmp_path)
+    assert result.returncode == 1
+    assert "Duplicate Python runtime module" in result.stderr
+
+
+@pytest.mark.parametrize("module", ["volcano_sdk.missing", "-1", "not-a-module"])
+def test_invalid_mutation_module_fails(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, module: str
 ) -> None:
     mutation_harness(tmp_path, monkeypatch, ["src/volcano_sdk/probe.py"])
-    monkeypatch.setenv("MUTATION_SHARD", shard)
+    monkeypatch.setenv("MUTATION_MODULE", module)
     result = run_mutation_script(tmp_path)
     assert result.returncode == 2
-    assert "Invalid mutation shard" in result.stderr
+    assert "Unknown mutation module" in result.stderr
 
 
 def fixture_report(tmp_path: Path, code: int | None) -> tuple[Path, Path]:
@@ -205,6 +249,25 @@ def test_killed_mutant_passes(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -
     assert main(targets, failed) == 0
 
 
+def test_functionless_package_init_is_reported(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.chdir(tmp_path)
+    source = Path("src/volcano_sdk/__init__.py")
+    source.parent.mkdir(parents=True)
+    _ = source.write_text('"""Public package exports."""\n', encoding="utf-8")
+    targets = tmp_path / "targets.bin"
+    _ = targets.write_bytes(f"{source}\0".encode())
+    failed = tmp_path / "failed.bin"
+    _ = failed.write_bytes(b"")
+    assert main(targets, failed) == 0
+    report = cast(
+        "object", json.loads(Path("reports/mutation.json").read_text(encoding="utf-8"))
+    )
+    assert isinstance(report, dict)
+    assert report["unmutatable_modules"] == [str(source)]
+
+
 def test_statically_invalid_mutant_is_reported_separately(
     tmp_path: Path, monkeypatch: pytest.MonkeyPatch
 ) -> None:

From d1fcc2ba349fff010207f66b6cde9377bc4ce16f Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 11:08:32 -0400
Subject: [PATCH 04/11] test: fail fast on unsupported durable wait timeout

---
 tests/unit/test_durable_authoring.py | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/tests/unit/test_durable_authoring.py b/tests/unit/test_durable_authoring.py
index 64178228..b9c0d9d3 100644
--- a/tests/unit/test_durable_authoring.py
+++ b/tests/unit/test_durable_authoring.py
@@ -989,17 +989,16 @@ def handler(_event: object, ctx: DurableContext) -> object:
 
 
 def test_wait_until_refuses_a_timeout() -> None:
-    @durable
-    def handler(_event: object, ctx: DurableContext) -> object:
-        return ctx.wait_until(
+    context = DurableContext(RecordingContext(), durable_authoring._Engine())
+
+    # Validate before handing the condition to the runtime, which may wait
+    # indefinitely when the unsupported timeout is silently ignored.
+    with pytest.raises(TypeError, match="has no `timeout`"):
+        _ = context.wait_until(
             lambda state, _scope: state,
             WaitUntilOptions(until=bool, initial_state=False, timeout="1h"),
         )
 
-    # A condition is bounded by checks, not by a deadline: the platform holds
-    # the wait between them and has no clock to compare against on resume.
-    assert "has no `timeout`" in failing_handler(handler)
-
 
 def test_wait_until_requires_an_initial_state() -> None:
     @durable

From 11f0dc11968677c5170032345823f37c7c6edbea Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 11:11:00 -0400
Subject: [PATCH 05/11] test: verify durable runtime adapter cache identity

---
 tests/unit/test_durable_authoring.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tests/unit/test_durable_authoring.py b/tests/unit/test_durable_authoring.py
index b9c0d9d3..cffae24e 100644
--- a/tests/unit/test_durable_authoring.py
+++ b/tests/unit/test_durable_authoring.py
@@ -185,6 +185,18 @@ def record(
     assert configured.initial_state is False
 
 
+def test_durable_runtime_adapter_is_loaded_once(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setattr(durable_authoring._Engine, "_loaded", None)
+
+    first = durable_authoring._Engine.load()
+    second = durable_authoring._Engine.load()
+
+    assert isinstance(first, durable_authoring._Engine)
+    assert first is second
+
+
 def test_wait_options_name_invalid_timing_fields() -> None:
     engine = durable_authoring._Engine()
 

From d4445dd050ce6c52dcb045b7c7ae1ec895013e57 Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 11:33:29 -0400
Subject: [PATCH 06/11] fix: report functionless mutation modules without stale
 results

---
 scripts/mutation.sh                 | 14 +++++++++
 tests/unit/test_mutation_results.py | 49 ++++++++++++++++++++++++++---
 2 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/scripts/mutation.sh b/scripts/mutation.sh
index e7876317..1f40d14c 100644
--- a/scripts/mutation.sh
+++ b/scripts/mutation.sh
@@ -58,6 +58,7 @@ for index in "${!paths[@]}"; do
     continue
   fi
   path=${paths[$index]}
+  selected_path=$path
   printf '%s\0' "$path" >> "$targets"
   patterns+=("${modules[$index]}.x*")
 done
@@ -69,6 +70,19 @@ fi
 
 # A fresh run must not inherit stale test-to-mutant mappings or verdicts.
 rm -rf -- mutants
+
+# Mutmut rejects an exact wildcard for a module with no functions. Record that
+# module explicitly instead of treating a native no-match assertion as a kill.
+if [[ -n ${MUTATION_MODULE:-} ]] && ! python -c '
+import sys
+from pathlib import Path
+from scripts.mutation_results import has_functions
+raise SystemExit(0 if has_functions(Path(sys.argv[1])) else 1)
+' "$selected_path"; then
+  python -m scripts.mutation_results "$targets" "$failed"
+  exit
+fi
+
 if ! mutmut run --max-children 1 "${patterns[@]}"; then
   printf '%s\0' 'mutation run' >> "$failed"
 fi
diff --git a/tests/unit/test_mutation_results.py b/tests/unit/test_mutation_results.py
index 6aac0df7..e4df23b6 100644
--- a/tests/unit/test_mutation_results.py
+++ b/tests/unit/test_mutation_results.py
@@ -5,6 +5,7 @@
 import json
 import os
 import subprocess
+import sys
 from pathlib import Path
 from typing import cast
 
@@ -17,7 +18,11 @@
 
 
 def mutation_harness(
-    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, modules: list[str]
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+    modules: list[str],
+    *,
+    real_python: bool = False,
 ) -> None:
     """Install shell stubs for testing the native Mutmut selector."""
     for module in modules:
@@ -32,6 +37,10 @@ def mutation_harness(
     _ = (scripts / "mutation.sh").write_bytes(
         (PROJECT / "scripts/mutation.sh").read_bytes()
     )
+    if real_python:
+        _ = (scripts / "mutation_results.py").write_bytes(
+            (PROJECT / "scripts/mutation_results.py").read_bytes()
+        )
     bin_dir = tmp_path / "bin"
     bin_dir.mkdir()
     stubs = {
@@ -42,12 +51,17 @@ def mutation_harness(
             "cat git-paths.bin\n"
         ),
         "mutmut": "#!/bin/sh\nprintf '%s\\n' \"$@\" > mutation-args.txt\n",
-        "python": "#!/bin/sh\nexit 0\n",
     }
     for name, content in stubs.items():
         stub = bin_dir / name
         _ = stub.write_text(content, encoding="utf-8")
         stub.chmod(0o755)
+    python = bin_dir / "python"
+    if real_python:
+        python.symlink_to(sys.executable)
+    else:
+        _ = python.write_text("#!/bin/sh\nexit 0\n", encoding="utf-8")
+        python.chmod(0o755)
     monkeypatch.setenv("PATH", f"{bin_dir}:{os.environ['PATH']}")
 
 
@@ -136,11 +150,18 @@ def test_mutation_matrix_covers_all_handwritten_modules(
 
     plan = run_mutation_matrix(tmp_path)
     assert plan.returncode == 0, plan.stderr
-    assert json.loads(plan.stdout) == [module_name(path) for path in modules]
+    planned: object = cast("object", json.loads(plan.stdout))
+    assert isinstance(planned, list)
+    values = cast("list[object]", planned)
+    matrix_modules: list[str] = []
+    for name in values:
+        assert isinstance(name, str)
+        matrix_modules.append(name)
+    assert matrix_modules == [module_name(path) for path in modules]
 
     selected: list[str] = []
     selected_patterns: list[str] = []
-    for module in json.loads(plan.stdout):
+    for module in matrix_modules:
         monkeypatch.setenv("MUTATION_MODULE", module)
         result = run_mutation_script(tmp_path)
         assert result.returncode == 0, result.stderr
@@ -183,6 +204,26 @@ def test_duplicate_import_name_fails_inventory(
     assert "Duplicate Python runtime module" in result.stderr
 
 
+def test_functionless_package_init_skips_native_no_match(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    source = "src/volcano_sdk/__init__.py"
+    mutation_harness(tmp_path, monkeypatch, [source], real_python=True)
+    _ = (tmp_path / source).write_text('"""Public exports."""\n', encoding="utf-8")
+    stale_metadata = tmp_path / "mutants" / f"{source}.meta"
+    stale_metadata.parent.mkdir(parents=True)
+    _ = stale_metadata.write_text('{"exit_code_by_key": {"stale": 1}}\n')
+    monkeypatch.setenv("MUTATION_MODULE", "volcano_sdk")
+    result = run_mutation_script(tmp_path)
+    assert result.returncode == 0, result.stderr
+    assert not (tmp_path / "mutation-args.txt").exists()
+    report = cast(
+        "object", json.loads((tmp_path / "reports/mutation.json").read_text())
+    )
+    assert isinstance(report, dict)
+    assert report["unmutatable_modules"] == [source]
+
+
 @pytest.mark.parametrize("module", ["volcano_sdk.missing", "-1", "not-a-module"])
 def test_invalid_mutation_module_fails(
     tmp_path: Path, monkeypatch: pytest.MonkeyPatch, module: str

From f79bd869ef06f543cb18dd7753ec7efa56299f23 Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 11:34:43 -0400
Subject: [PATCH 07/11] refactor: simplify connection string query handling

---
 src/volcano_sdk/connection_string.py | 30 +++++++++++++---------------
 tests/unit/test_connection_string.py |  6 ++++++
 2 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/src/volcano_sdk/connection_string.py b/src/volcano_sdk/connection_string.py
index b69ad544..dabce2a5 100644
--- a/src/volcano_sdk/connection_string.py
+++ b/src/volcano_sdk/connection_string.py
@@ -1,7 +1,7 @@
 """Postgres connection helpers for Volcano functions."""
 
 import re
-from urllib.parse import quote, unquote
+from urllib.parse import quote, unquote, urlencode
 
 _FULL_ACCESS_APP_NAME = "volcano_full_access"
 _USER_ACCESS_APP_NAME = "volcano_user_access"
@@ -40,8 +40,11 @@ def database_connection_string(
 
     target, query = _connection_parts(base_connection_string)
     parameters = _query_parameters(query)
-    application_name = quote(_database_application_name(user_id), safe="")
-    parameters.append(f"application_name={application_name}")
+    parameters.append(
+        urlencode(
+            {"application_name": _database_application_name(user_id)}, quote_via=quote
+        )
+    )
     return f"{target}?{'&'.join(parameters)}"
 
 
@@ -50,15 +53,11 @@ def _connection_parts(value: str) -> tuple[str, str]:
     if prefix is None or _INVALID_PERCENT_ENCODING.search(value):
         raise ValueError(_INVALID_ERROR)
 
-    authority_end = value.find("/", prefix.end())
-    possible_userinfo_end = value.find("@", prefix.end())
-    userinfo_end = (
-        possible_userinfo_end
-        if possible_userinfo_end != -1
-        and (authority_end == -1 or possible_userinfo_end < authority_end)
-        else -1
-    )
-    query_start = value.find("?", max(prefix.end(), userinfo_end + 1))
+    before_at, at_separator, _ = value[prefix.end() :].partition("@")
+    query_search_start = prefix.end()
+    if at_separator and "/" not in before_at:
+        query_search_start += len(before_at) + 1
+    query_start = value.find("?", query_search_start)
     if query_start == -1:
         return value, ""
     return value[:query_start], value[query_start + 1 :]
@@ -72,10 +71,9 @@ def _query_parameters(query: str) -> list[str]:
         for parameter in query.split("&")
         if unquote(parameter.partition("=")[0]) != "application_name"
     ]
-    for index in range(len(parameters) - 1, -1, -1):
-        if parameters[index]:
-            return parameters[: index + 1]
-    return []
+    while parameters and not parameters[-1]:
+        _ = parameters.pop()
+    return parameters
 
 
 def _database_application_name(user_id: str | None) -> str:
diff --git a/tests/unit/test_connection_string.py b/tests/unit/test_connection_string.py
index 3ad56efc..de407370 100644
--- a/tests/unit/test_connection_string.py
+++ b/tests/unit/test_connection_string.py
@@ -109,6 +109,12 @@ def test_database_connection_string_keeps_credential_question_mark() -> None:
     )
 
 
+def test_database_connection_string_finds_query_immediately_after_userinfo() -> None:
+    assert database_connection_string("postgres://u@?sslmode=require") == (
+        "postgres://u@?sslmode=require&application_name=volcano_full_access"
+    )
+
+
 def test_database_connection_string_ignores_later_at_sign_in_query() -> None:
     base = "postgres://u@host?options=a@b"
 

From 103febee13c2035cbc4363cdd975dd681e2004ce Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 11:36:58 -0400
Subject: [PATCH 08/11] test(python): bound client mutation failure paths

---
 tests/unit/test_database_refresh.py |  3 +++
 tests/unit/test_token_bootstrap.py  | 11 +++++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/tests/unit/test_database_refresh.py b/tests/unit/test_database_refresh.py
index d409bad0..43a31064 100644
--- a/tests/unit/test_database_refresh.py
+++ b/tests/unit/test_database_refresh.py
@@ -362,6 +362,9 @@ def test_refresh_listener_can_wait_for_another_refresh_thread() -> None:
     def on_refresh(event: str, _session: Session | None) -> None:
         if event != "TOKEN_REFRESHED":
             return
+        if workers:
+            completed.append(False)
+            return
         subscription.unsubscribe()
         worker = Thread(target=client.auth.refresh_session)
         workers.append(worker)
diff --git a/tests/unit/test_token_bootstrap.py b/tests/unit/test_token_bootstrap.py
index 90144fba..ba59ae07 100644
--- a/tests/unit/test_token_bootstrap.py
+++ b/tests/unit/test_token_bootstrap.py
@@ -84,18 +84,21 @@ def make_transport(*, api_url: str, timeout: float) -> GeneratedTransport:
     assert observed == [("https://api.volcano.dev", 60.0)]
 
 
-def test_token_bootstrap_is_local_until_profile_validation() -> None:
+@pytest.mark.parametrize("refresh_token", [None, "supplied-refresh"])
+def test_token_bootstrap_is_local_until_profile_validation(
+    refresh_token: str | None,
+) -> None:
     requests: list[httpx.Request] = []
 
     def handle(request: httpx.Request) -> httpx.Response:
         requests.append(request)
         return httpx.Response(200, json={"user": PROFILE})
 
-    client = token_client(handle)
+    client = token_client(handle, refresh_token=refresh_token)
     initial = client.auth.get_session()
     assert initial is not None
     assert initial.access_token == "supplied-access"
-    assert initial.refresh_token is None
+    assert initial.refresh_token == refresh_token
     assert initial.user_id is None
     assert initial.user is None
     assert not requests
@@ -105,7 +108,7 @@ def handle(request: httpx.Request) -> httpx.Response:
     assert current.user_id == USER_ID
     assert current.user == PROFILE
     assert current.access_token == initial.access_token
-    assert current.refresh_token is None
+    assert current.refresh_token == refresh_token
     assert initial.user_id is None
     assert requests[0].headers["authorization"] == "Bearer supplied-access"
 

From e7300896917f74c308b34c077ac65f8f5a3e88c8 Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 11:57:42 -0400
Subject: [PATCH 09/11] test: close remaining full-runtime mutation gaps

---
 maintainers/mutation-testing.md             |   8 +-
 src/volcano_sdk/_realtime_fetch_worker.py   |   8 +-
 src/volcano_sdk/connection_string.py        |   7 +-
 tests/unit/test_connection_string.py        |  13 ++
 tests/unit/test_realtime_fetch_cleanup.py   | 198 ++++++++++++++++++++
 tests/unit/test_realtime_fetch_lifecycle.py |  66 +++----
 tests/unit/test_realtime_fetch_worker.py    |  47 ++---
 7 files changed, 284 insertions(+), 63 deletions(-)
 create mode 100644 tests/unit/test_realtime_fetch_cleanup.py

diff --git a/maintainers/mutation-testing.md b/maintainers/mutation-testing.md
index 93c2b6ab..1f386acc 100644
--- a/maintainers/mutation-testing.md
+++ b/maintainers/mutation-testing.md
@@ -14,6 +14,9 @@ select modules by name but returns success when mutants survive.
 `scripts/mutation_results.py` reads each selected module's native metadata. The
 report at `reports/mutation.json` distinguishes killed, statically invalid,
 surviving, uncovered, timed-out, crashed, interrupted, and missing results.
+Mutmut creates mutants inside functions. Export-only modules remain in the
+inventory; the runner verifies that they define no functions and records them
+as unmutatable. Coverage and installed-package checks still include them.
 A pytest internal error is a harness crash, not a killed mutant.
 The pinned Pyrefly check covers the handwritten runtime and rejects
 type-invalid mutants before pytest;
@@ -31,8 +34,9 @@ Mutmut uses its native forkserver isolation because forking from a process that
 has already run asyncio tests can crash a worker before its tests report a result.
 The mutation runner sets `NO_PROXY=*` for its hermetic transport tests because
 macOS system-proxy discovery can abort after a fork with active threads.
-The pinned pytest-order plugin runs bounded callback and presence assertions
-first when mutmut's unordered test selection could otherwise reach a blocked test.
+The pinned pytest-order plugin runs bounded callback, presence, and fetch-worker
+assertions first when mutmut's unordered test selection could otherwise reach a
+blocked test.
 
 The local and weekly full runs execute the inventory in one Mutmut process.
 Equivalent mutants require a reviewed, exact exception before a gate can
diff --git a/src/volcano_sdk/_realtime_fetch_worker.py b/src/volcano_sdk/_realtime_fetch_worker.py
index 421e73f5..e0f0b835 100644
--- a/src/volcano_sdk/_realtime_fetch_worker.py
+++ b/src/volcano_sdk/_realtime_fetch_worker.py
@@ -293,9 +293,11 @@ async def _fetch_and_deliver(
         if isinstance(result, BaseException):
             await self._deliver_failure(jobs, result)
             return
-        if len(result) != len(jobs):
-            raise RuntimeError(_INVALID_RESULT_COUNT)
-        for job, record in zip(jobs, result, strict=True):
+        try:
+            pairs = tuple(zip(jobs, result, strict=True))
+        except ValueError:
+            raise RuntimeError(_INVALID_RESULT_COUNT) from None
+        for job, record in pairs:
             await self._deliver(PostgresFetchOutcome(job=job, record=record))
 
     async def _deliver_failure(
diff --git a/src/volcano_sdk/connection_string.py b/src/volcano_sdk/connection_string.py
index dabce2a5..55bef179 100644
--- a/src/volcano_sdk/connection_string.py
+++ b/src/volcano_sdk/connection_string.py
@@ -64,16 +64,13 @@ def _connection_parts(value: str) -> tuple[str, str]:
 
 
 def _query_parameters(query: str) -> list[str]:
-    if not query:
-        return []
     parameters = [
         parameter
         for parameter in query.split("&")
         if unquote(parameter.partition("=")[0]) != "application_name"
     ]
-    while parameters and not parameters[-1]:
-        _ = parameters.pop()
-    return parameters
+    serialized = "&".join(parameters).rstrip("&")
+    return serialized.split("&") if serialized else []
 
 
 def _database_application_name(user_id: str | None) -> str:
diff --git a/tests/unit/test_connection_string.py b/tests/unit/test_connection_string.py
index de407370..f92c9006 100644
--- a/tests/unit/test_connection_string.py
+++ b/tests/unit/test_connection_string.py
@@ -89,6 +89,19 @@ def test_database_connection_string_drops_only_empty_parameters() -> None:
     )
 
 
+@pytest.mark.parametrize(
+    "query", ["mode=X", "mode=with space", "mode=XX&XX", "mode=x&&other=y"]
+)
+def test_database_connection_string_preserves_unrelated_query_fields(
+    query: str,
+) -> None:
+    base = f"postgresql://host/db?{query}"
+
+    assert database_connection_string(base) == (
+        f"{base}&application_name=volcano_full_access"
+    )
+
+
 def test_database_connection_string_ignores_at_sign_in_query_value() -> None:
     assert database_connection_string("postgresql://host/db?options=foo@bar") == (
         "postgresql://host/db?options=foo@bar&application_name=volcano_full_access"
diff --git a/tests/unit/test_realtime_fetch_cleanup.py b/tests/unit/test_realtime_fetch_cleanup.py
new file mode 100644
index 00000000..60c3287c
--- /dev/null
+++ b/tests/unit/test_realtime_fetch_cleanup.py
@@ -0,0 +1,198 @@
+from __future__ import annotations
+
+import asyncio
+
+import pytest
+from test_realtime_fetch_lifecycle import cancel_operation
+from test_realtime_fetch_worker import (
+    BlockingRowFetch,
+    OutcomeRecorder,
+    RecordingBatchFetch,
+    fetch_job,
+)
+from typing_extensions import override
+
+from volcano_sdk._realtime_fetch_worker import (
+    PostgresFetchJob,
+    PostgresFetchWorker,
+    _StopWorker,
+    _wait_for_close,
+)
+
+
+class DelayedCancellation:
+    def __init__(self) -> None:
+        self.started: asyncio.Event = asyncio.Event()
+        self.cancelled: asyncio.Event = asyncio.Event()
+        self.release_cleanup: asyncio.Event = asyncio.Event()
+
+    async def wait(self) -> None:
+        self.started.set()
+        try:
+            _ = await asyncio.Event().wait()
+        except asyncio.CancelledError:
+            self.cancelled.set()
+            _ = await self.release_cleanup.wait()
+            raise
+
+
+class CleanupQueue(asyncio.Queue[PostgresFetchJob[str] | _StopWorker]):
+    def __init__(self) -> None:
+        super().__init__(maxsize=1)
+        self.started: asyncio.Event = asyncio.Event()
+        self.cancelled: asyncio.Event = asyncio.Event()
+        self.release_cleanup: asyncio.Event = asyncio.Event()
+
+    @override
+    async def put(self, item: PostgresFetchJob[str] | _StopWorker) -> None:
+        self.started.set()
+        try:
+            await super().put(item)
+        except asyncio.CancelledError:
+            self.cancelled.set()
+            _ = await self.release_cleanup.wait()
+            raise
+
+
+async def fail_worker() -> None:
+    message = "delivery failed"
+    raise RuntimeError(message)
+
+
+async def test_close_waits_for_cancelled_stop_cleanup() -> None:
+    stop = DelayedCancellation()
+    stop_task = asyncio.create_task(stop.wait())
+    task = asyncio.create_task(fail_worker())
+    closing = asyncio.create_task(_wait_for_close(task, stop_task))
+    try:
+        _ = await asyncio.wait_for(stop.cancelled.wait(), timeout=1)
+        await asyncio.sleep(0)
+        assert not closing.done()
+        stop.release_cleanup.set()
+        with pytest.raises(RuntimeError, match="delivery failed"):
+            await asyncio.wait_for(closing, timeout=1)
+        assert stop_task.cancelled()
+    finally:
+        stop.release_cleanup.set()
+        await cancel_operation(closing)
+        await cancel_operation(stop_task)
+        await cancel_operation(task)
+
+
+async def test_cancelled_enqueue_waits_for_its_queue_put_cleanup() -> None:
+    queue = CleanupQueue()
+    queue.put_nowait(fetch_job(1))
+    worker = PostgresFetchWorker(
+        RecordingBatchFetch(), OutcomeRecorder(), queue_limit=1
+    )
+    worker._queue = queue
+    waiting = DelayedCancellation()
+    task = asyncio.create_task(waiting.wait())
+    enqueueing = asyncio.create_task(worker._put_while_running(fetch_job(2), task))
+    try:
+        _ = await asyncio.wait_for(queue.started.wait(), timeout=1)
+        _ = enqueueing.cancel()
+        _ = await asyncio.wait_for(queue.cancelled.wait(), timeout=1)
+        await asyncio.sleep(0)
+        assert not enqueueing.done()
+        queue.release_cleanup.set()
+        with pytest.raises(asyncio.CancelledError):
+            await asyncio.wait_for(enqueueing, timeout=1)
+        assert queue.get_nowait() == fetch_job(1)
+        assert queue.empty()
+    finally:
+        queue.release_cleanup.set()
+        waiting.release_cleanup.set()
+        if not queue.empty():
+            _ = queue.get_nowait()
+        await cancel_operation(enqueueing)
+        await cancel_operation(task)
+
+
+async def test_abort_cancels_an_outstanding_stop_request() -> None:
+    fetch = BlockingRowFetch()
+    worker = PostgresFetchWorker(fetch, OutcomeRecorder(), queue_limit=1)
+    closing = None
+    try:
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
+        _ = await asyncio.wait_for(fetch.started.wait(), timeout=1)
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
+        closing = asyncio.create_task(worker.close())
+        await asyncio.sleep(0)
+        stop_task = worker._stop_task
+        assert stop_task is not None
+        assert not stop_task.done()
+        await cancel_operation(closing)
+        await asyncio.wait_for(worker.abort(), timeout=1)
+        assert stop_task.cancelled()
+        assert fetch.cancelled.is_set()
+    finally:
+        fetch.release.set()
+        await cancel_operation(closing)
+        await asyncio.wait_for(worker.abort(), timeout=1)
+
+
+async def test_closed_worker_rejects_jobs_before_abort() -> None:
+    worker = PostgresFetchWorker(
+        RecordingBatchFetch(), OutcomeRecorder(), queue_limit=1
+    )
+    try:
+        await asyncio.wait_for(worker.close(), timeout=1)
+        with pytest.raises(RuntimeError, match="fetch worker is closed"):
+            await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
+    finally:
+        await asyncio.wait_for(worker.abort(), timeout=1)
+
+
+async def test_repeated_close_completes_all_queued_tasks() -> None:
+    worker = PostgresFetchWorker(
+        RecordingBatchFetch(),
+        OutcomeRecorder(),
+        queue_limit=2,
+        batch_window_seconds=1,
+        max_batch_size=2,
+    )
+    try:
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
+        await asyncio.wait_for(worker.close(), timeout=1)
+        await asyncio.wait_for(worker.close(), timeout=1)
+        await asyncio.wait_for(worker._queue.join(), timeout=1)
+    finally:
+        await asyncio.wait_for(worker.abort(), timeout=1)
+
+
+async def test_batch_capacity_flushes_without_an_extra_row() -> None:
+    fetch = RecordingBatchFetch()
+    delivered = asyncio.Event()
+
+    async def deliver(_outcome: object) -> None:
+        delivered.set()
+
+    worker = PostgresFetchWorker[str](
+        fetch, deliver, queue_limit=3, max_batch_size=2, batch_window_seconds=60
+    )
+    try:
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
+        _ = await asyncio.wait_for(delivered.wait(), timeout=1)
+        assert fetch.calls == [(1, 2)]
+        await asyncio.wait_for(worker.enqueue(fetch_job(3)), timeout=1)
+        await asyncio.wait_for(worker.close(), timeout=1)
+        assert fetch.calls == [(1, 2), (3,)]
+    finally:
+        await asyncio.wait_for(worker.abort(), timeout=1)
+
+
+async def test_expired_batch_deadline_preserves_queued_row(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    worker = PostgresFetchWorker(
+        RecordingBatchFetch(), OutcomeRecorder(), queue_limit=1
+    )
+    worker._queue.put_nowait(fetch_job(1))
+    loop = asyncio.get_running_loop()
+    with monkeypatch.context() as scoped:
+        scoped.setattr(loop, "time", lambda: 42.0)
+        assert await worker._next_before(42.0) is None
+    assert worker._queue.get_nowait() == fetch_job(1)
diff --git a/tests/unit/test_realtime_fetch_lifecycle.py b/tests/unit/test_realtime_fetch_lifecycle.py
index ac4b6e7e..669ac63d 100644
--- a/tests/unit/test_realtime_fetch_lifecycle.py
+++ b/tests/unit/test_realtime_fetch_lifecycle.py
@@ -51,11 +51,11 @@ async def test_unused_worker_can_close_and_abort_repeatedly() -> None:
 
     await worker.close()
     await worker.close()
-    await worker.abort()
-    await worker.abort()
+    await asyncio.wait_for(worker.abort(), timeout=1)
+    await asyncio.wait_for(worker.abort(), timeout=1)
 
     with pytest.raises(RuntimeError, match="fetch worker is closed"):
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
     assert fetch.calls == []
     assert deliver.items == []
 
@@ -70,9 +70,9 @@ async def fail_delivery(_outcome: PostgresFetchOutcome[str]) -> None:
     worker = PostgresFetchWorker(fetch, fail_delivery, queue_limit=1)
     closing = None
     try:
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         _ = await asyncio.wait_for(fetch.started.wait(), timeout=1)
-        await worker.enqueue(fetch_job(2))
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
         closing = asyncio.create_task(worker.close())
         await asyncio.sleep(0)
         stop_task = worker._stop_task
@@ -87,7 +87,7 @@ async def fail_delivery(_outcome: PostgresFetchOutcome[str]) -> None:
         assert stop_task.cancelled()
         assert fetch.row_ids == [1]
     finally:
-        await worker.abort()
+        await asyncio.wait_for(worker.abort(), timeout=1)
         await cancel_operation(closing)
 
 
@@ -97,9 +97,9 @@ async def test_abort_unblocks_close_with_a_full_queue() -> None:
     worker = PostgresFetchWorker(fetch, deliver, queue_limit=1)
     closing = None
     try:
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         _ = await asyncio.wait_for(fetch.started.wait(), timeout=1)
-        await worker.enqueue(fetch_job(2))
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
         closing = asyncio.create_task(worker.close())
         await asyncio.sleep(0)
         stop_task = worker._stop_task
@@ -115,7 +115,7 @@ async def test_abort_unblocks_close_with_a_full_queue() -> None:
         assert fetch.cancelled.is_set()
         assert deliver.items == []
     finally:
-        await worker.abort()
+        await asyncio.wait_for(worker.abort(), timeout=1)
         await cancel_operation(closing)
 
 
@@ -125,9 +125,9 @@ async def test_abort_rejects_an_enqueue_waiting_for_capacity() -> None:
     worker = PostgresFetchWorker(fetch, deliver, queue_limit=1)
     enqueueing = None
     try:
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         _ = await asyncio.wait_for(fetch.started.wait(), timeout=1)
-        await worker.enqueue(fetch_job(2))
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
         enqueueing = asyncio.create_task(worker.enqueue(fetch_job(3)))
         await asyncio.sleep(0)
         assert not enqueueing.done()
@@ -139,29 +139,32 @@ async def test_abort_rejects_an_enqueue_waiting_for_capacity() -> None:
         assert fetch.cancelled.is_set()
         assert deliver.items == []
     finally:
-        await worker.abort()
+        await asyncio.wait_for(worker.abort(), timeout=1)
         await cancel_operation(enqueueing)
 
 
-async def test_wrong_batch_result_count_fails_before_delivery() -> None:
+@pytest.mark.parametrize("records", [(), ({"id": 1}, {"id": 2})])
+async def test_wrong_batch_result_count_fails_before_delivery(
+    records: tuple[dict[str, int], ...],
+) -> None:
     release = asyncio.Event()
 
-    async def no_results(
+    async def malformed_results(
         _requests: tuple[_PostgresFetchRequest, ...],
     ) -> tuple[dict[str, int], ...]:
         _ = await release.wait()
-        return ()
+        return records
 
     deliver = OutcomeRecorder()
-    worker = PostgresFetchWorker(no_results, deliver, queue_limit=1)
+    worker = PostgresFetchWorker(malformed_results, deliver, queue_limit=1)
     try:
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         release.set()
         with pytest.raises(RuntimeError, match="unexpected result count"):
             await asyncio.wait_for(worker.close(), timeout=1)
         assert deliver.items == []
     finally:
-        await worker.abort()
+        await asyncio.wait_for(worker.abort(), timeout=1)
 
 
 async def test_fetch_cancellation_propagates_without_delivering_a_fallback() -> None:
@@ -178,7 +181,7 @@ async def cancelled_fetch(
     deliver = OutcomeRecorder()
     worker = PostgresFetchWorker(cancelled_fetch, deliver, queue_limit=1)
     try:
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         _ = await asyncio.wait_for(started.wait(), timeout=1)
         release.set()
 
@@ -187,7 +190,7 @@ async def cancelled_fetch(
 
         assert deliver.items == []
     finally:
-        await worker.abort()
+        await asyncio.wait_for(worker.abort(), timeout=1)
 
 
 async def test_batch_window_flushes_without_waiting_for_another_row_or_close() -> None:
@@ -202,13 +205,13 @@ async def deliver(outcome: PostgresFetchOutcome[str]) -> None:
         fetch, deliver, queue_limit=2, max_batch_size=2, batch_window_seconds=0.1
     )
     try:
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         _ = await asyncio.wait_for(delivered.wait(), timeout=1)
         await asyncio.wait_for(worker.close(), timeout=1)
 
         assert fetch.calls == [(1,)]
     finally:
-        await worker.abort()
+        await asyncio.wait_for(worker.abort(), timeout=1)
 
 
 @pytest.mark.parametrize(("window", "expected"), [(0, [(1,), (2,)]), (60, [(1, 2)])])
@@ -221,15 +224,15 @@ async def test_batch_capacity_and_zero_window_preserve_delivery_order(
         fetch, deliver, queue_limit=2, max_batch_size=2, batch_window_seconds=window
     )
     try:
-        await worker.enqueue(fetch_job(1))
-        await worker.enqueue(fetch_job(2))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
         await asyncio.wait_for(worker.close(), timeout=1)
-        await worker.abort()
+        await asyncio.wait_for(worker.abort(), timeout=1)
 
         assert fetch.calls == expected
         assert [item.record for item in deliver.items] == [{"id": 1}, {"id": 2}]
     finally:
-        await worker.abort()
+        await asyncio.wait_for(worker.abort(), timeout=1)
 
 
 async def test_zero_batch_window_keeps_queued_followup_fetches_separate() -> None:
@@ -250,16 +253,15 @@ async def fetch(
         OutcomeRecorder(),
         queue_limit=3,
         max_batch_size=3,
-        batch_window_seconds=0,
     )
     try:
-        await worker.enqueue(fetch_job(1))
-        _ = await asyncio.wait_for(first_fetch_started.wait(), timeout=1)
-        await worker.enqueue(fetch_job(2))
-        await worker.enqueue(fetch_job(3))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
+        _ = await asyncio.wait_for(first_fetch_started.wait(), timeout=0.2)
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
+        await asyncio.wait_for(worker.enqueue(fetch_job(3)), timeout=1)
         release_first_fetch.set()
         await asyncio.wait_for(worker.close(), timeout=1)
 
         assert recording_fetch.calls == [(1,), (2,), (3,)]
     finally:
-        await worker.abort()
+        await asyncio.wait_for(worker.abort(), timeout=1)
diff --git a/tests/unit/test_realtime_fetch_worker.py b/tests/unit/test_realtime_fetch_worker.py
index a7effb92..006bf7da 100644
--- a/tests/unit/test_realtime_fetch_worker.py
+++ b/tests/unit/test_realtime_fetch_worker.py
@@ -96,6 +96,7 @@ def passthrough_job(name: str) -> PostgresFetchJob[str]:
     return PostgresFetchJob(request=None, fallback=name)
 
 
+@pytest.mark.order(0)
 def test_postgres_fetch_worker_bounds_and_orders_fetches() -> None:
     async def scenario() -> None:
         fetch = BlockingRowFetch()
@@ -103,9 +104,9 @@ async def scenario() -> None:
         outcomes = deliver.items
 
         worker = PostgresFetchWorker(fetch, deliver, queue_limit=1)
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         _ = await asyncio.wait_for(fetch.started.wait(), timeout=0.2)
-        await worker.enqueue(fetch_job(2))
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
         third_enqueue = asyncio.create_task(worker.enqueue(fetch_job(3)))
         await asyncio.sleep(0)
 
@@ -143,9 +144,9 @@ async def scenario() -> None:
             batch_window_seconds=0.05,
             max_batch_size=3,
         )
-        await worker.enqueue(fetch_job(1))
-        await worker.enqueue(fetch_job(2))
-        await worker.enqueue(fetch_job(3))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
+        await asyncio.wait_for(worker.enqueue(fetch_job(3)), timeout=1)
         await asyncio.wait_for(worker.close(), timeout=0.2)
 
         assert fetch.calls == [(1, 2, 3)]
@@ -176,8 +177,8 @@ async def scenario() -> None:
             batch_window_seconds=0.01,
             max_batch_size=2,
         )
-        await worker.enqueue(fetch_job(1))
-        await worker.enqueue(fetch_job(2, table="archive"))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
+        await asyncio.wait_for(worker.enqueue(fetch_job(2, table="archive")), timeout=1)
         await asyncio.wait_for(worker.close(), timeout=0.2)
 
         assert fetch.calls == [(1,), (2,)]
@@ -202,8 +203,8 @@ async def scenario() -> None:
             batch_window_seconds=0.01,
             max_batch_size=2,
         )
-        await worker.enqueue(fetch_job(1))
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         await asyncio.wait_for(worker.close(), timeout=0.2)
 
         assert fetch.calls == [(1,), (1,)]
@@ -219,9 +220,11 @@ async def scenario() -> None:
         outcomes = deliver.items
 
         worker = PostgresFetchWorker(fetch, deliver, queue_limit=1)
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         _ = await asyncio.wait_for(fetch.started.wait(), timeout=0.2)
-        await worker.enqueue(passthrough_job("full-payload"))
+        await asyncio.wait_for(
+            worker.enqueue(passthrough_job("full-payload")), timeout=1
+        )
 
         assert outcomes == []
 
@@ -237,6 +240,7 @@ async def scenario() -> None:
     asyncio.run(scenario())
 
 
+@pytest.mark.order(0)
 def test_postgres_fetch_worker_aborts_obsolete_jobs_without_waiting() -> None:
     async def scenario() -> None:
         fetch = BlockingRowFetch()
@@ -244,9 +248,9 @@ async def scenario() -> None:
         outcomes = deliver.items
 
         worker = PostgresFetchWorker(fetch, deliver, queue_limit=1)
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         _ = await asyncio.wait_for(fetch.started.wait(), timeout=0.2)
-        await worker.enqueue(fetch_job(2))
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
 
         await asyncio.wait_for(worker.abort(), timeout=0.2)
 
@@ -274,8 +278,8 @@ async def scenario() -> None:
             deliver,
             queue_limit=2,
         )
-        await worker.enqueue(fetch_job(1))
-        await worker.enqueue(fetch_job(2))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
         await asyncio.wait_for(worker.close(), timeout=0.2)
 
         assert outcomes == [
@@ -302,15 +306,16 @@ async def fail_delivery(_outcome: PostgresFetchOutcome[str]) -> None:
             fail_delivery,
             queue_limit=1,
         )
-        await worker.enqueue(fetch_job(2))
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
         _ = await delivery_started.wait()
         release_delivery.set()
         await asyncio.sleep(0)
 
         with pytest.raises(RuntimeError) as raised:
-            await worker.enqueue(fetch_job(3))
+            await asyncio.wait_for(worker.enqueue(fetch_job(3)), timeout=1)
 
         assert raised.value is failure
+        assert worker._queue.empty()
 
     asyncio.run(scenario())
 
@@ -322,9 +327,9 @@ async def scenario() -> None:
         outcomes = deliver.items
 
         worker = PostgresFetchWorker(fetch, deliver, queue_limit=1)
-        await worker.enqueue(fetch_job(1))
+        await asyncio.wait_for(worker.enqueue(fetch_job(1)), timeout=1)
         _ = await asyncio.wait_for(fetch.started.wait(), timeout=0.2)
-        await worker.enqueue(fetch_job(2))
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
 
         interrupted_close = asyncio.create_task(worker.close())
         await asyncio.sleep(0)
@@ -362,9 +367,9 @@ async def fail_delivery(_outcome: PostgresFetchOutcome[str]) -> None:
             fail_delivery,
             queue_limit=1,
         )
-        await worker.enqueue(fetch_job(2))
+        await asyncio.wait_for(worker.enqueue(fetch_job(2)), timeout=1)
         _ = await delivery_started.wait()
-        await worker.enqueue(fetch_job(3))
+        await asyncio.wait_for(worker.enqueue(fetch_job(3)), timeout=1)
         blocked_enqueue = asyncio.create_task(worker.enqueue(fetch_job(4)))
         await asyncio.sleep(0)
         assert not blocked_enqueue.done()

From 49e73ec2d908ceaccf0aaa3a7b23d70b1db2c246 Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 12:26:25 -0400
Subject: [PATCH 10/11] test: fail fast when a durable step drops its retry
 policy

---
 tests/unit/test_durable_authoring.py | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tests/unit/test_durable_authoring.py b/tests/unit/test_durable_authoring.py
index cffae24e..0c873662 100644
--- a/tests/unit/test_durable_authoring.py
+++ b/tests/unit/test_durable_authoring.py
@@ -131,6 +131,22 @@ def test_retry_false_produces_an_immediate_no_retry_decision() -> None:
     assert decision.delay.to_seconds() == 0
 
 
+@pytest.mark.order(0)
+def test_step_forwards_a_disabled_retry_before_scheduling() -> None:
+    runtime = RecordingContext()
+    context = DurableContext(runtime, durable_authoring._Engine())
+
+    with pytest.raises(AssertionError, match="unexpected runtime operation"):
+        _ = context.step("once", lambda _scope: "done", retry=False)
+
+    assert isinstance(runtime.config, StepConfig)
+    retry = runtime.config.retry_strategy
+    assert retry is not None
+    decision = retry(RuntimeError("failed"), 1)
+    assert decision.should_retry is False
+    assert decision.delay.to_seconds() == 0
+
+
 def test_custom_retry_receives_the_original_error() -> None:
     engine = durable_authoring._Engine()
     failure = RuntimeError("failed")

From 37fe230a5b9f95b4f1985a40d7be207c4f210e47 Mon Sep 17 00:00:00 2001
From: Sean Keever <33592180+swkeever@users.noreply.github.com>
Date: Thu, 24 Sep 2026 12:42:23 -0400
Subject: [PATCH 11/11] test: bound EOF and bootstrap mutation failures

---
 tests/unit/test_storage_boundaries.py | 22 ++++++++++++++++++++++
 tests/unit/test_token_bootstrap.py    |  1 +
 2 files changed, 23 insertions(+)

diff --git a/tests/unit/test_storage_boundaries.py b/tests/unit/test_storage_boundaries.py
index dbf2a5a0..a44194c2 100644
--- a/tests/unit/test_storage_boundaries.py
+++ b/tests/unit/test_storage_boundaries.py
@@ -31,6 +31,28 @@
     from volcano_sdk.storage import StorageBucket
 
 
+class EndOfUploadSource:
+    """Record the terminal read and fail if an upload retries EOF."""
+
+    def __init__(self) -> None:
+        self.sizes: list[int] = []
+
+    def read(self, size: int = -1, /) -> bytes:
+        if self.sizes:
+            message = "upload source read after end of stream"
+            raise AssertionError(message)
+        self.sizes.append(size)
+        return b""
+
+
+@pytest.mark.order(0)
+def test_upload_part_stops_reading_at_end_of_stream() -> None:
+    source = EndOfUploadSource()
+
+    assert _read_upload_part(source, 4) == b""
+    assert source.sizes == [4]
+
+
 class UnavailableRawStream(RawIOBase):
     @override
     def readable(self) -> bool:
diff --git a/tests/unit/test_token_bootstrap.py b/tests/unit/test_token_bootstrap.py
index ba59ae07..c764f22c 100644
--- a/tests/unit/test_token_bootstrap.py
+++ b/tests/unit/test_token_bootstrap.py
@@ -84,6 +84,7 @@ def make_transport(*, api_url: str, timeout: float) -> GeneratedTransport:
     assert observed == [("https://api.volcano.dev", 60.0)]
 
 
+@pytest.mark.order(0)
 @pytest.mark.parametrize("refresh_token", [None, "supplied-refresh"])
 def test_token_bootstrap_is_local_until_profile_validation(
     refresh_token: str | None,