diff --git a/.github/workflows/drupal-contrib-integration-test.yml b/.github/workflows/drupal-contrib-integration-test.yml
index 97769f9..af378e7 100644
--- a/.github/workflows/drupal-contrib-integration-test.yml
+++ b/.github/workflows/drupal-contrib-integration-test.yml
@@ -393,8 +393,11 @@ jobs:
     strategy:
       # PRs run a single module (smoke); push-to-main and nightly run the full
       # set. Cuts per-PR workspace load on staging. See ci-reap.yml.
+      # The smoke cell is the D12 one on purpose: it tracks Drupal core HEAD, so
+      # it is where dependency churn (e.g. core's Guzzle 8 bump) breaks first.
+      # The D11 cells are stable and covered on push-to-main and nightly.
       matrix:
-        include: ${{ github.event_name == 'pull_request' && fromJSON('[{"project":"token","drupal_version":"11"}]') || fromJSON('[{"project":"token","drupal_version":"11"},{"project":"pathauto","drupal_version":"11"},{"project":"skipto","drupal_version":"12"}]') }}
+        include: ${{ github.event_name == 'pull_request' && fromJSON('[{"project":"skipto","drupal_version":"12"}]') || fromJSON('[{"project":"token","drupal_version":"11"},{"project":"pathauto","drupal_version":"11"},{"project":"skipto","drupal_version":"12"}]') }}
       fail-fast: false
     defaults:
       run:
diff --git a/drupal-contrib/scripts/test-issue-branches.sh b/drupal-contrib/scripts/test-issue-branches.sh
index 56c56c1..8db504d 100755
--- a/drupal-contrib/scripts/test-issue-branches.sh
+++ b/drupal-contrib/scripts/test-issue-branches.sh
@@ -135,7 +135,25 @@ for SPEC in "${TESTS[@]}"; do
     ddev exec composer require --dev drush/drush --no-update --no-interaction 2>&1 | tail -5
 
     log "Running ddev poser..."
-    if ! ddev poser 2>&1 | tail -10; then
+    POSER_RC=0
+    ddev poser > /tmp/poser-attempt.log 2>&1 || POSER_RC=$?
+    tail -10 /tmp/poser-attempt.log
+    # Mirrors the Guzzle alias fallback in template.tf: Drush still requires
+    # guzzlehttp/guzzle ^7.0 while core main requires ^8.0, which makes a plain
+    # poser run unsolvable on Drupal 12 HEAD. Removal tracked in #179
+    # (upstream: drush-ops/drush#6602).
+    if [ "$POSER_RC" != "0" ] && grep -q "drush/drush.*requires guzzlehttp/guzzle" /tmp/poser-attempt.log; then
+      GUZZLE_VER=$(curl -fsSL --max-time 30 https://repo.packagist.org/p2/guzzlehttp/guzzle.json 2>/dev/null |
+        jq -r '[.packages["guzzlehttp/guzzle"][].version | select(test("^8[.][0-9]+[.][0-9]+$"))] | sort_by(split(".") | map(tonumber)) | last // empty' 2>/dev/null || true)
+      if [ -n "$GUZZLE_VER" ]; then
+        log "Drush/Guzzle conflict — retrying poser with guzzle $GUZZLE_VER aliased as 7.99.0..."
+        jq --arg v "$GUZZLE_VER as 7.99.0" '.["require-dev"]["guzzlehttp/guzzle"] = $v' composer.json > composer.json.tmp && mv composer.json.tmp composer.json
+        POSER_RC=0
+        ddev poser > /tmp/poser-attempt.log 2>&1 || POSER_RC=$?
+        tail -10 /tmp/poser-attempt.log
+      fi
+    fi
+    if [ "$POSER_RC" != "0" ]; then
       log "ERROR: ddev poser failed"
       RESULTS["$DIR_KEY"]="FAIL (ddev poser)"
       DURATIONS["$DIR_KEY"]=$((SECONDS - START))
diff --git a/drupal-contrib/template.tf b/drupal-contrib/template.tf
index 847dec5..d099389 100644
--- a/drupal-contrib/template.tf
+++ b/drupal-contrib/template.tf
@@ -750,11 +750,18 @@ COMPOSE_EOF
         # then runs composer install (installs Drupal + drush together), then removes composer.contrib.json
         # Retry up to 3 times to handle transient codeload.github.com 400s.
         _poser_ok=false
+        _guzzle_aliased=false
         for _attempt in 1 2 3; do
           log_setup "Running ddev poser (attempt $_attempt/3)..."
           update_status "⏳ ddev poser: Attempt $_attempt/3..."
           _t=$SECONDS
-          if ddev poser >> "$SETUP_LOG" 2>&1; then
+          # Capture this attempt separately so the conflict check below cannot
+          # match output from an earlier attempt or an earlier workspace start
+          # ($SETUP_LOG is append-only across restarts).
+          _poser_rc=0
+          ddev poser > /tmp/poser-attempt.log 2>&1 || _poser_rc=$?
+          cat /tmp/poser-attempt.log >> "$SETUP_LOG"
+          if [ "$_poser_rc" = "0" ]; then
             log_setup "✓ ddev poser complete ($((SECONDS - _t))s)"
             update_status "✓ ddev poser: Success"
             # Hide the drush require-dev line from git status without touching the
@@ -765,6 +772,37 @@ COMPOSE_EOF
             break
           fi
           log_setup "✗ ddev poser attempt $_attempt failed ($((SECONDS - _t))s)"
+
+          # Drush's Guzzle constraint lags core's: core main moved to
+          # guzzlehttp/guzzle ^8.0 on 2026-07-24 (drupal.org #3612544) while
+          # every Drush version still requires ^7.0, so Composer cannot solve
+          # drush/drush against Drupal 12 HEAD. Guzzle 8 works with Drush at
+          # runtime, so retry with an inline alias presenting a Guzzle 8 release
+          # as a 7.x one — the same workaround #178 added to drupal-core, which
+          # deliberately left this template alone because the version cannot be
+          # read from a lock file here: ddev poser resolves core and Drush in one
+          # solve and deletes composer.contrib.lock afterwards. Composer only
+          # accepts an exact version as an alias source, so ask packagist for the
+          # newest stable 8.x instead. Applied only on this specific failure, so
+          # Drupal 11 builds (core requires Guzzle ^7) keep resolving normally,
+          # and it self-clears once Drush is fixed. Unlike drupal-core, where the
+          # alias lands in gitignored composer.local.json, here it lands in the
+          # module's tracked composer.json — the skip-worktree call above keeps
+          # it out of git status, same as the drush require-dev line. Removal is
+          # tracked in #179 (upstream: drush-ops/drush#6602).
+          if [ "$_guzzle_aliased" = "false" ] && \
+             grep -q "drush/drush.*requires guzzlehttp/guzzle" /tmp/poser-attempt.log; then
+            _guzzle_ver=$(curl -fsSL --max-time 30 https://repo.packagist.org/p2/guzzlehttp/guzzle.json 2>/dev/null |
+              jq -r '[.packages["guzzlehttp/guzzle"][].version | select(test("^8[.][0-9]+[.][0-9]+$"))] | sort_by(split(".") | map(tonumber)) | last // empty' 2>/dev/null || true)
+            if [ -n "$_guzzle_ver" ]; then
+              log_setup "Drush/Guzzle constraint conflict — retrying with guzzle $_guzzle_ver aliased as 7.99.0..."
+              jq --arg v "$_guzzle_ver as 7.99.0" '.["require-dev"]["guzzlehttp/guzzle"] = $v' composer.json > composer.json.tmp && mv composer.json.tmp composer.json
+              _guzzle_aliased=true
+              continue
+            fi
+            log_setup "⚠ Could not determine a stable Guzzle 8 version from packagist"
+          fi
+
           if [ "$_attempt" -lt 3 ]; then
             log_setup "Retrying in 15s..."
             sleep 15