Pin uxarray-mcp to Python 3.12

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
     - uses: actions/checkout@v4
     - uses: actions/setup-python@v5
       with:
-        python-version: '3.13'
+        python-version: '3.12'
     - uses: pre-commit/action@v3.0.1
 
   test-core:
@@ -22,10 +22,10 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.11", "3.12", "3.13"]
+        python-version: ["3.12"]
         include:
           - os: macos-latest
-            python-version: "3.13"
+            python-version: "3.12"
 
     steps:
     - uses: actions/checkout@v4
@@ -57,10 +57,10 @@ jobs:
     - name: Install uv
       uses: astral-sh/setup-uv@v5
 
-    - name: Set up Python 3.13
+    - name: Set up Python 3.12
       uses: actions/setup-python@v5
       with:
-        python-version: '3.13'
+        python-version: '3.12'
 
     - name: Install package
       run: |
@@ -101,17 +101,17 @@ jobs:
     - name: Install uv
       uses: astral-sh/setup-uv@v5
 
-    - name: Set up Python 3.13
+    - name: Set up Python 3.12
       uses: actions/setup-python@v5
       with:
-        python-version: '3.13'
+        python-version: '3.12'
 
     - name: Build wheel and sdist
       run: uv build
 
     - name: Install wheel in a clean venv
       run: |
-        uv venv /tmp/uxarray-mcp-wheel --python 3.13
+        uv venv /tmp/uxarray-mcp-wheel --python 3.12
         uv pip install --python /tmp/uxarray-mcp-wheel/bin/python dist/uxarray_mcp-*.whl
         /tmp/uxarray-mcp-wheel/bin/uxarray-mcp --help
 
@@ -121,7 +121,7 @@ jobs:
     continue-on-error: true
     strategy:
       matrix:
-        python-version: ["3.13"]
+        python-version: ["3.12"]
 
     steps:
     - uses: actions/checkout@v4
@@ -151,10 +151,10 @@ jobs:
     - name: Install uv
       uses: astral-sh/setup-uv@v5
 
-    - name: Set up Python 3.13
+    - name: Set up Python 3.12
       uses: actions/setup-python@v5
       with:
-        python-version: '3.13'
+        python-version: '3.12'
 
     - name: Install docs dependencies
       run: |

.github/workflows/release.yml

@@ -25,10 +25,10 @@ jobs:
       - name: Install uv
         uses: astral-sh/setup-uv@v5
 
-      - name: Set up Python 3.13
+      - name: Set up Python 3.12
         uses: actions/setup-python@v5
         with:
-          python-version: "3.13"
+          python-version: "3.12"
 
       - name: Build distributions
         run: uv build
@@ -38,7 +38,7 @@ jobs:
 
       - name: Install wheel in a clean venv
         run: |
-          uv venv /tmp/uxarray-mcp-wheel --python 3.13
+          uv venv /tmp/uxarray-mcp-wheel --python 3.12
           uv pip install --python /tmp/uxarray-mcp-wheel/bin/python dist/uxarray_mcp-*.whl
           /tmp/uxarray-mcp-wheel/bin/uxarray-mcp --help
 
@@ -75,18 +75,18 @@ jobs:
       - name: Install uv
         uses: astral-sh/setup-uv@v5
 
-      - name: Set up Python 3.13
+      - name: Set up Python 3.12
         uses: actions/setup-python@v5
         with:
-          python-version: "3.13"
+          python-version: "3.12"
 
       - name: Install released wheel from PyPI
         env:
           REF_NAME: ${{ inputs.tag || github.ref_name }}
         run: |
           version="${REF_NAME#v}"
           echo "Verifying uxarray-mcp==${version} from PyPI"
-          uv venv /tmp/uxarray-mcp-pypi --python 3.13
+          uv venv /tmp/uxarray-mcp-pypi --python 3.12
           installed=0
           for attempt in 1 2 3 4 5; do
             if uv pip install --python /tmp/uxarray-mcp-pypi/bin/python \
@@ -125,11 +125,11 @@ jobs:
         if: env.CONDA_FEEDSTOCK_REPOSITORY != '' && env.CONDA_FEEDSTOCK_TOKEN != ''
         uses: astral-sh/setup-uv@v5
 
-      - name: Set up Python 3.13
+      - name: Set up Python 3.12
         if: env.CONDA_FEEDSTOCK_REPOSITORY != '' && env.CONDA_FEEDSTOCK_TOKEN != ''
         uses: actions/setup-python@v5
         with:
-          python-version: "3.13"
+          python-version: "3.12"
 
       - name: Build source distribution for hash
         if: env.CONDA_FEEDSTOCK_REPOSITORY != '' && env.CONDA_FEEDSTOCK_TOKEN != ''

.python-version

@@ -1 +1 @@
-3.13
+3.12

README.md

@@ -51,13 +51,21 @@ Pick one. `uv` is the easiest; `pip` works too.
 
 ```bash
 # Recommended
-uv tool install uxarray-mcp
+uv tool install --python 3.12 uxarray-mcp
 
 # Or from a fresh clone (developer path)
 git clone https://github.com/UXARRAY/uxarray-mcp-server.git
-cd uxarray-mcp-server && uv sync
+cd uxarray-mcp-server && uv sync --python 3.12
 ```
 
+> **Why `--python 3.12`?** The server uses Globus Compute to submit work to
+> HPC endpoints, and Globus Compute's serializer is fragile across Python
+> minor versions — a 3.13 submitter against a 3.12 endpoint worker raises
+> `WorkerLost` on non-trivial payloads. HPC sites broadly ship 3.12 conda
+> stacks today, so we pin the install to match. Tracking removal of this pin
+> at [globus/globus-compute#2139](https://github.com/globus/globus-compute/issues/2139).
+> `uv` downloads 3.12 automatically if your system doesn't have it.
+
 ### Step 2 — Write a starter config
 
 ```bash

docs/operating-an-endpoint.md

@@ -70,11 +70,12 @@ globus-compute-endpoint configure uxarray
 > versions (3.12 ↔ 3.13). The packaged MCP tools route through
 > `AllCodeStrategies` and survive minor differences for simple payloads, but
 > raw `Executor.submit()` calls and any user code dropping down to the SDK
-> directly will hit pickle protocol errors and `WorkerLost`. The simplest
-> rule: pick a Python on the worker (3.12 is broadly available across HPC
-> sites today) and match it on the submitter side with
-> `uv tool install --python 3.12 uxarray-mcp`. `uxarray-mcp doctor` will
-> surface a warning at probe time when versions differ.
+> directly will hit pickle protocol errors and `WorkerLost`. **uxarray-mcp
+> pins to Python 3.12 today** ([globus/globus-compute#2139](https://github.com/globus/globus-compute/issues/2139)
+> tracks the upstream fix that will let us broaden this). Stand up your
+> endpoint on 3.12 and your submitter install will already match;
+> `uxarray-mcp doctor` will surface a warning at probe time if anything is
+> off.
 
 Edit `~/.globus_compute/uxarray/config.yaml` and set the scheduler block.
 Minimum diff from the generated template (PBS example shown — see Step 3
@@ -214,7 +215,7 @@ home is small):
 # Use the site's recommended conda or module first
 module load conda    # or whatever your site provides
 
-conda create -n gce python=3.11 -c conda-forge -y
+conda create -n gce python=3.12 -c conda-forge -y
 conda activate gce
 pip install globus-compute-endpoint
 ```

docs/remote-hpc.md

@@ -67,9 +67,17 @@ If not:
 ## Step 2 — Install the HPC extras locally (1 min)
 
 ```bash
-uv tool install "uxarray-mcp[hpc]"      # or `uv tool upgrade --extra hpc uxarray-mcp`
+uv tool install --python 3.12 "uxarray-mcp[hpc]"
+# or to upgrade an existing install:
+# uv tool upgrade --python 3.12 --extra hpc uxarray-mcp
 ```
 
+The `--python 3.12` flag matters: most HPC endpoints today (chrysalis,
+Casper, Improv) run Python 3.12 conda stacks, and Globus Compute's serializer
+is fragile across Python minor versions. Mismatch raises `WorkerLost` on
+non-trivial payloads. Tracked upstream at
+[globus/globus-compute#2139](https://github.com/globus/globus-compute/issues/2139).
+
 This adds the `globus-compute-sdk` to your local install. Verify:
 
 ```bash

pyproject.toml

@@ -10,17 +10,20 @@ classifiers = [
     "Topic :: Scientific/Engineering",
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
-    "Programming Language :: Python :: 3.13",
     "License :: OSI Approved :: Apache Software License",
 ]
 authors = [
     { name = "Rajeev Jain", email = "rajeeja@gmail.com" },
     { name = "Dayan Abdulla", email = "dayanabdulla000@gmail.com" },
 ]
 license = { file = "LICENSE" }
-requires-python = ">=3.11"
+# Pinned to 3.12 until globus/globus-compute#2139 lands a published submitter ↔
+# worker compatibility story. HPC sites broadly ship Python 3.12 conda stacks
+# today; matching that minor version on the submitter side avoids WorkerLost
+# from pickle protocol skew. Revisit when upstream confirms multi-version
+# support and broaden requires-python back to >=3.11.
+requires-python = ">=3.12,<3.13"
 dependencies = [
     "fastmcp>=3.4.0",
     "holoviews>=1.19.0",