[mikkel]

Patchling cannot co-install with ai-agent-toolbox 1.x because metadata caps it below 1.0. Removing only that cap still breaks imports: the real published 1.x wheel no longer exports MarkdownParser/MarkdownPromptFormatter.

Use Patchling's existing extract_diff_blocks implementation for generated Markdown diffs, remove obsolete/unused formatter imports, and retain the real XMLParser + Toolbox path for apply reasoning/tool dispatch. Relax the requirement from ai-agent-toolbox>=0.2.0,<1.0 to ai-agent-toolbox>=0.2.0. No upstream Toolbox changes are needed.

Validation:

• Original dependency resolution failure reproduced with real 1.0.3; original code also reproduces ImportError on MarkdownParser when the cap is bypassed.
• Full suites: 263 passed / 2 skipped with actual 0.2.0 (Python 3.10 editable install), 1.0.0 (Python 3.11 installed wheel), and 1.0.3 (Python 3.10 installed source distribution).
• 11 new regression cases verify the actual installed package/version, real XML events and Toolbox callback dispatch, generated multi-file diffs applied end to end, and provider failure propagation. LLM transport/token counting are mocked; Toolbox classes/events are not stubbed.
• Wheel/sdist build, strict Twine check, dependency metadata, source contents, license/type marker, all four CLI entrypoints, pip check, py_compile and diff checks passed.
• The existing CI runs the full suite with the latest compatible published dependency. An additional Python 3.10/3.12 matrix for pinned 0.2.0, 1.0.0, 1.0.3 and latest is fully prepared below, but not applied: GitHub rejected the workflow update because this OAuth credential lacks workflow scope. No credentials or permissions were changed. An owner with existing workflow-write access can apply the proposed patch.

The older task's claimed Toolbox 1.2.1 does not currently exist: official PyPI JSON returns HTTP 404 for 1.2.0 and 1.2.1 and upstream tags stop at 1.0.3. Tests use real released packages rather than inventing those versions. References: https://pypi.org/project/ai-agent-toolbox/ and https://github.com/255BITS/ai-agent-toolbox/tags .

Scope: consumer compatibility only. No version bump, package release, publishing/authentication change, main merge or documentation deployment. Previously retained release artifacts are unchanged; packaging validation used a separate test-artifact directory.

Proposed CI matrix patch (reviewable text only; not installed by this PR):

diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 56a6ad7..bb025c4 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -4,22 +4,33 @@ on: [push, pull_request]
 
 jobs:
   test:
+    name: Python ${{ matrix.python }} / Toolbox ${{ matrix.toolbox }}
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python: ["3.10", "3.12"]
+        toolbox: ["0.2.0", "1.0.0", "1.0.3", "latest"]
 
     steps:
     - name: Checkout code
       uses: actions/checkout@v4
 
-    - name: Set up Python 3.10
+    - name: Set up Python
       uses: actions/setup-python@v4
       with:
-        python-version: '3.10'
+        python-version: ${{ matrix.python }}
 
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install -e .[test]
-        pip install pytest
+        if [ "$TOOLBOX_VERSION" = "latest" ]; then
+          python -m pip install --upgrade -e '.[test]' 'ai-agent-toolbox>=0.2.0'
+        else
+          python -m pip install -e '.[test]' "ai-agent-toolbox==$TOOLBOX_VERSION"
+        fi
+        python -m pip check
+        python -c "from importlib.metadata import version; print('ai-agent-toolbox=' + version('ai-agent-toolbox'))"
 
     - name: Run tests
       run: |
@@ -27,3 +38,4 @@ jobs:
 
     env:
       GPTDIFF_LLM_API_KEY: "dummy-key"  # Required but unused in mocked tests
+      TOOLBOX_VERSION: ${{ matrix.toolbox }}