diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 33f4a44..02ce4f9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -4,6 +4,13 @@ on:
   push:
     branches: [main]
   pull_request:
+  # Mondays, 06:00 UTC. Every other trigger here is caused by someone pushing,
+  # so without this the suite is only ever run against the dependency versions
+  # `uv.lock` pins -- see the `upstream-drift` job for what that hides. Note
+  # GitHub disables a scheduled workflow after 60 days with no repository
+  # activity, so a long quiet spell stops these runs rather than failing them.
+  schedule:
+    - cron: "0 6 * * 1"
   workflow_dispatch:
 
 permissions:
@@ -167,6 +174,85 @@ jobs:
         # `addopts` in pyproject.toml supplies `-m 'not live'`.
         run: uv run pytest
 
+  upstream-drift:
+    # `uv.lock` is what every other job resolves against, so nothing in this
+    # workflow would notice a new `langgraph` minor breaking the runtime until a
+    # user on a fresh `pip install grapharc` hit it. Issue #103 is the standing
+    # form of that complaint: the extras are unbounded and the lockfile hides
+    # what the next major would do. This job re-resolves every range from
+    # scratch and runs the suite against the newest versions the constraints in
+    # pyproject.toml actually allow.
+    #
+    # Scheduled and manual only, deliberately. A pull request has to be judged
+    # against the lockfile it ships; if this ran on PRs, an upstream release on
+    # the morning of a review would turn someone else's branch red for a reason
+    # that branch did not cause.
+    name: upstream drift (unlocked deps)
+    if: github.event_name == 'schedule' || github.event_name == 'workflow_dispatch'
+    runs-on: ubuntu-latest
+    # `issues: write` is for the reporting step below; a job's permissions
+    # replace the workflow's rather than adding to them, so `contents: read`
+    # is repeated here.
+    permissions:
+      contents: read
+      issues: write
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/setup-uv@v5
+        with:
+          python-version: "3.12"
+          enable-cache: true
+      - name: Re-resolve every dependency to the newest allowed version
+        run: uv lock --upgrade
+      - name: Report what moved
+        # Printed whether or not the suite then passes: a green run against
+        # moved dependencies is the useful half of this job, because it is the
+        # evidence that a range can be widened or a pin dropped.
+        run: git --no-pager diff --stat -- uv.lock
+      - name: Sync and test against the re-resolved versions
+        run: |
+          uv sync --all-extras --group dev
+          uv run pytest
+      - name: Say so where someone will see it
+        # A scheduled run reports to nobody. This repository has already paid
+        # for that: `pages.yml` failed on two consecutive pushes and the
+        # failures sat unnoticed for the better part of two months, while the
+        # published site served a version six releases behind. A weekly job in
+        # a repository that goes quiet for weeks at a time is the same shape,
+        # so the failure comes to the issue tracker instead of the Actions tab.
+        #
+        # One issue, reused: an unattended weekly job that opens a fresh issue
+        # every Monday is a second way of being ignored. Matched on title
+        # rather than a label, so this needs no label to exist first.
+        if: failure()
+        env:
+          GH_TOKEN: ${{ github.token }}
+          TITLE: "upstream drift: the suite fails against re-resolved dependencies"
+          RUN_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
+        run: |
+          body=$(cat <<EOF
+          The weekly \`upstream-drift\` job failed: the suite does not pass against the
+          newest dependency versions \`pyproject.toml\` allows.
+
+          Run: $RUN_URL
+
+          **This is not a failure of any branch.** Every other job resolves against
+          \`uv.lock\`; this one re-resolves from scratch. So either an upstream release
+          broke something, or a range in \`pyproject.toml\` needs narrowing — which is
+          what #103 asks for. The job prints the re-resolved lockfile diff, so the run
+          log says which dependencies moved.
+          EOF
+          )
+          existing=$(gh issue list --state open --search "$TITLE in:title" \
+            --json number --jq '.[0].number // empty')
+          if [ -n "$existing" ]; then
+            echo "commenting on existing issue #$existing"
+            gh issue comment "$existing" --body "$body"
+          else
+            echo "opening a new issue"
+            gh issue create --title "$TITLE" --body "$body"
+          fi
+
   build:
     name: build and check the distribution
     runs-on: ubuntu-latest