diff --git a/.github/workflows/_selftest.yml b/.github/workflows/_selftest.yml
index e9c9bd8..c10c6df 100644
--- a/.github/workflows/_selftest.yml
+++ b/.github/workflows/_selftest.yml
@@ -1487,6 +1487,34 @@ jobs:
           fi
           echo "claude.yml's SENSITIVE_PATHS mirror matches claude-code-action@${sha}."
 
+  # gha#442: SUBMODULES_TOKEN authenticates a cross-owner SUBMODULE fetch
+  # (via the checkout-submodules composite's `submodules-token:` input) and
+  # must never gate the caller's own repo checkout --- a consumer that sets
+  # it correctly for its own submodule is exactly the consumer whose main
+  # checkout then fails, since the token has no reason to be able to read the
+  # caller's repo. The anchor is `^\s*token:`, not a bare `token:` substring
+  # match, so this does not also flag `submodules-token:` (which legitimately
+  # carries the secret) --- a trimmed line starting with "submodules-token:"
+  # never matches a pattern requiring "token:" immediately after the leading
+  # whitespace.
+  lint-checkout-tokens:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      contents: read
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Assert no workflow passes SUBMODULES_TOKEN to a top-level checkout's token input
+        shell: bash
+        run: |
+          set -euo pipefail
+          if grep -rnE '^\s*token:\s*\$\{\{[^}]*SUBMODULES_TOKEN' .github/workflows/*.yml; then
+            echo "::error::A workflow above passes SUBMODULES_TOKEN to a top-level actions/checkout 'token:' input (see gha#442) --- it authenticates a cross-owner submodule fetch, not the caller's own repo. Use the checkout-submodules composite's 'submodules-token:' input instead."
+            exit 1
+          fi
+          echo "No workflow passes SUBMODULES_TOKEN to a top-level checkout token: input."
+
   # Covers the open-failure-issue action. report-failure.yml is its only
   # caller so far; check-links.yml's migration onto it is deferred to gha#327,
   # since a @v2 reference to a not-yet-released action fails at job-prepare
diff --git a/.github/workflows/antigravity-code-review.yml b/.github/workflows/antigravity-code-review.yml
index 605034b..561996c 100644
--- a/.github/workflows/antigravity-code-review.yml
+++ b/.github/workflows/antigravity-code-review.yml
@@ -102,13 +102,24 @@ jobs:
             echo "blocked=false" >> "$GITHUB_OUTPUT"
           fi
 
+      # The caller's own repo is checked out with the runner's default
+      # github.token, never SUBMODULES_TOKEN --- that secret authenticates a
+      # CROSS-OWNER submodule fetch and has no reason to (and, when a
+      # consumer sets it correctly for its own submodule, frequently cannot)
+      # read the caller's own repo (gha#442). Submodule auth is handled below
+      # by the shared checkout-submodules composite, the same one
+      # claude-code-review.yml already uses.
       - name: Checkout repository
         if: success() && steps.dispatch-guard.outputs.blocked != 'true'
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
         with:
           persist-credentials: false
-          submodules: ${{ inputs.checkout-submodules }}
-          token: ${{ secrets.SUBMODULES_TOKEN || github.token }}
+
+      - name: Checkout submodules
+        if: success() && steps.dispatch-guard.outputs.blocked != 'true' && inputs.checkout-submodules
+        uses: Morrison-Lab/gha/.github/actions/checkout-submodules@v2
+        with:
+          submodules-token: ${{ secrets.SUBMODULES_TOKEN }}
 
       - name: Run Antigravity Action
         if: success() && steps.dispatch-guard.outputs.blocked != 'true'
diff --git a/.github/workflows/gemini-code-review.yml b/.github/workflows/gemini-code-review.yml
index a663dce..b28f949 100644
--- a/.github/workflows/gemini-code-review.yml
+++ b/.github/workflows/gemini-code-review.yml
@@ -162,12 +162,22 @@ jobs:
       # the guard step is skipped entirely, so its output is the empty string;
       # there the job `if:` has already applied the equivalent checks from the
       # event payload.
+      # The caller's own repo is checked out with the runner's default
+      # github.token, never SUBMODULES_TOKEN --- that secret authenticates a
+      # CROSS-OWNER submodule fetch and has no reason to (and, when a
+      # consumer sets it correctly for its own submodule, frequently cannot)
+      # read the caller's own repo (gha#442). Submodule auth is handled below
+      # by the shared checkout-submodules composite, the same one
+      # claude-code-review.yml already uses.
       - name: Checkout repository
         if: success() && steps.dispatch-guard.outputs.blocked != 'true'
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Checkout submodules
+        if: success() && steps.dispatch-guard.outputs.blocked != 'true' && inputs.checkout-submodules
+        uses: Morrison-Lab/gha/.github/actions/checkout-submodules@v2
         with:
-          submodules: ${{ inputs.checkout-submodules }}
-          token: ${{ secrets.SUBMODULES_TOKEN || github.token }}
+          submodules-token: ${{ secrets.SUBMODULES_TOKEN }}
 
       # Pinned to a release SHA per README's "Pinning third-party actions".
       # run-gemini-cli publishes v0 / v0.1.x and has no v1 tag, so a `@v1` ref
diff --git a/.github/workflows/gemini.yml b/.github/workflows/gemini.yml
index 7109c5a..e75eeec 100644
--- a/.github/workflows/gemini.yml
+++ b/.github/workflows/gemini.yml
@@ -278,12 +278,22 @@ jobs:
             echo "thread_line=This is an unattended run in $REPO with no associated issue or pull request, so there is no thread to read or reply to." >> "$GITHUB_OUTPUT"
           fi
 
+      # The caller's own repo is checked out with the runner's default
+      # github.token, never SUBMODULES_TOKEN --- that secret authenticates a
+      # CROSS-OWNER submodule fetch and has no reason to (and, when a
+      # consumer sets it correctly for its own submodule, frequently cannot)
+      # read the caller's own repo (gha#442). Submodule auth is handled below
+      # by the shared checkout-submodules composite, the same one claude.yml
+      # already uses.
       - name: Checkout repository
         if: steps.gate.outputs.skip != 'true'
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Checkout submodules
+        if: steps.gate.outputs.skip != 'true' && inputs.checkout-submodules
+        uses: Morrison-Lab/gha/.github/actions/checkout-submodules@v2
         with:
-          submodules: ${{ inputs.checkout-submodules }}
-          token: ${{ secrets.SUBMODULES_TOKEN || github.token }}
+          submodules-token: ${{ secrets.SUBMODULES_TOKEN }}
 
       # Passed via env rather than inlined into the script, so a caller's value
       # is a shell word list and never interpreted as script.
diff --git a/changelog.d/checkout-token-conflation-cross-owner-submodule.fixed.md b/changelog.d/checkout-token-conflation-cross-owner-submodule.fixed.md
new file mode 100644
index 0000000..552ed5d
--- /dev/null
+++ b/changelog.d/checkout-token-conflation-cross-owner-submodule.fixed.md
@@ -0,0 +1,22 @@
+- **`antigravity-code-review.yml`, `gemini-code-review.yml`, and `gemini.yml`
+  no longer fail to check out the CALLER's own repo when `SUBMODULES_TOKEN`
+  is set for a cross-owner submodule** (#442).
+  All three passed
+  `${{ secrets.SUBMODULES_TOKEN || github.token }}` as the top-level
+  `actions/checkout` `token:` input --- the same input `claude-code-review.yml`
+  leaves at the runner's default `github.token`.
+  `SUBMODULES_TOKEN` exists
+  precisely because a submodule lives under a different owner than the
+  consumer, so a token scoped to read the submodule has no reason to be able
+  to read the caller's own repo, and in `ucdavis/bcs` it could not: the main
+  checkout failed with `fatal: could not read Username for
+  'https://github.com': terminal prompts disabled` on every run, so a repo
+  that configured `SUBMODULES_TOKEN` correctly for its submodule got a red
+  check and zero automated review from two of its three configured agents.
+  All three now check out the caller with the runner's own token and
+  authenticate the submodule fetch (when `checkout-submodules` is set)
+  through the shared `checkout-submodules` composite action, matching
+  `claude-code-review.yml`.
+  A new `lint-checkout-tokens` selftest job asserts
+  no workflow in this repo passes `SUBMODULES_TOKEN` to a top-level
+  `actions/checkout` `token:` input, so the conflation can't recur silently.