build(release): stop building releases with a yanked builder

Every `uv lock` in this repo prints:

  warning: `build==1.5.1` is yanked (reason: "Considers breaking changes,
  will discuss re-releasing as a new major version.")

It is easy to read past, because nothing fails. A yanked release still
installs when it is pinned exactly, and build 1.5.1 was pinned in two
places: uv.lock, which produces the wheels python-compat smoke-tests, and
publish-pypi.yml, which produces the artifacts that go to PyPI. So the
warning was not cosmetic -- it said the release path runs on a version
upstream has withdrawn, and would keep saying so until someone looked.

Both move to 1.6.0, the supported successor. Keeping them together
matters: a release built by a different builder than the one CI exercises
is the kind of difference that only shows up in the published artifact.
tests/unit/test_publish_workflows.py asserts the exact install command, so
it moves too, and the workflow now carries the reason inline.

requirements-docker.lock is unchanged -- build is a `dev` dependency and
the cloud/postgres export does not include it.

Verified locally with build 1.6.0 installed: both wheels build the way
python-compat builds them (`python -m build --wheel --no-isolation` for
the runtime and for sdk/, agentflow_runtime-2.1.0 and
agentflow_client-2.1.0), scripts/wheel_smoke.py reports "top-level policy
OK", `uv lock --check` passes (256 packages) and prints no yank warning,
`uv export` leaves requirements-docker.lock untouched, and
test_publish_workflows.py passes (5 passed).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018ybRVCaL1Lyd9d5kFTndh3

Author: JuliaEdom

.github/workflows/publish-pypi.yml

@@ -79,8 +79,14 @@ jobs:
               env.write(f"IS_RC={str('-rc' in release_version).lower()}\n")
           PY
 
+      # build 1.5.1 was yanked upstream ("considers breaking changes, will
+      # discuss re-releasing as a new major version"). A yanked release still
+      # installs when pinned exactly, so this kept working -- it just meant
+      # every published artifact came out of a withdrawn builder. 1.6.0 is the
+      # supported successor; uv.lock carries the same version for the wheels
+      # CI builds in python-compat.
       - name: Install build tooling
-        run: python -m pip install --upgrade build==1.5.1 twine==6.2.0
+        run: python -m pip install --upgrade build==1.6.0 twine==6.2.0
 
       - name: Clean previous distributions
         run: rm -rf dist sdk/dist

CHANGELOG.md

@@ -4,6 +4,20 @@ All notable changes to AgentFlow are documented in this file.
 
 ## [Unreleased]
 
+### Supply chain — releases were being built by a yanked builder
+
+* **`build` 1.5.1 is yanked upstream** ("considers breaking changes, will
+  discuss re-releasing as a new major version"), and it was pinned in two
+  places: `uv.lock`, which builds the wheels CI smoke-tests in
+  `python-compat`, and `.github/workflows/publish-pypi.yml`, which builds the
+  artifacts that go to PyPI. A yanked release still installs when pinned
+  exactly, so nothing failed — every `uv lock` just printed the warning and
+  every release came out of a withdrawn builder.
+* **Both now use 1.6.0**, the supported successor. `requirements-docker.lock`
+  is unchanged (`build` is a `dev` dependency, not part of the
+  cloud/postgres export), and `tests/unit/test_publish_workflows.py` pins the
+  new command so the two cannot drift apart.
+
 ### Dependencies — the two version ceilings that keep coming back are now explained
 
 * **`mcp<2` is load-bearing.** mcp 2.x's lowlevel `Server` no longer defines

tests/unit/test_publish_workflows.py

@@ -121,7 +121,7 @@ def test_python_publish_checks_artifacts_with_pinned_tooling_before_upload():
     names = [step.get("name") for step in steps if isinstance(step, dict)]
     commands = _step_commands(workflow)
 
-    assert "python -m pip install --upgrade build==1.5.1 twine==6.2.0" in commands
+    assert "python -m pip install --upgrade build==1.6.0 twine==6.2.0" in commands
     assert "python scripts/check_release_artifacts.py dist/* sdk/dist/*" in commands
     assert names.index("Reject unsafe release artifacts") < names.index(
         "Dry-run build and twine check"