diff --git a/lib/archeflow-rollback.sh b/lib/archeflow-rollback.sh
new file mode 100755
index 0000000..6d3aace
--- /dev/null
+++ b/lib/archeflow-rollback.sh
@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+# archeflow-rollback.sh — Auto-revert a merge that fails post-merge tests.
+#
+# Usage: archeflow-rollback.sh <run_id> [--test-cmd <cmd>]
+#
+# If --test-cmd not provided, reads test_command from .archeflow/config.yaml.
+# Returns 0 if tests pass, 1 if tests fail (merge reverted).
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+RUN_ID="${1:?Usage: archeflow-rollback.sh <run_id> [--test-cmd <cmd>]}"
+shift
+
+# Parse optional --test-cmd
+TEST_CMD=""
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    --test-cmd) TEST_CMD="$2"; shift 2 ;;
+    *) echo "Unknown option: $1" >&2; exit 2 ;;
+  esac
+done
+
+# Read test_command from config if not provided
+if [[ -z "$TEST_CMD" ]]; then
+  if [[ -f ".archeflow/config.yaml" ]]; then
+    TEST_CMD=$(grep -E "^test_command:" .archeflow/config.yaml | sed 's/^test_command:\s*//' | tr -d '"' || true)
+  fi
+fi
+
+if [[ -z "$TEST_CMD" ]]; then
+  echo "ERROR: No test command specified (use --test-cmd or set test_command in .archeflow/config.yaml)" >&2
+  exit 2
+fi
+
+# Verify HEAD is an ArcheFlow merge
+HEAD_MSG=$(git log -1 --format=%s HEAD)
+if [[ "$HEAD_MSG" != *"$RUN_ID"* ]] && [[ "$HEAD_MSG" != *"archeflow"* ]]; then
+  echo "WARNING: HEAD commit does not appear to be an ArcheFlow merge: $HEAD_MSG" >&2
+  echo "Proceeding anyway..." >&2
+fi
+
+echo "Running post-merge tests: $TEST_CMD"
+
+if timeout 300 bash -c "$TEST_CMD"; then
+  echo "Tests passed — merge is good."
+  exit 0
+fi
+
+echo "Tests FAILED — reverting merge..."
+git revert --no-edit HEAD
+
+# Emit event if event script exists
+if [[ -x "$SCRIPT_DIR/archeflow-event.sh" ]]; then
+  "$SCRIPT_DIR/archeflow-event.sh" "$RUN_ID" decision act "" \
+    "{\"what\":\"post_merge_test\",\"chosen\":\"revert\",\"rationale\":\"test suite failed after merge\"}" ""
+fi
+
+REVERT_HASH=$(git rev-parse --short HEAD)
+echo "Merge reverted (commit: $REVERT_HASH). Tests must pass before re-merging."
+exit 1
diff --git a/skills/git-integration/SKILL.md b/skills/git-integration/SKILL.md
index cd415e1..d0499a1 100644
--- a/skills/git-integration/SKILL.md
+++ b/skills/git-integration/SKILL.md
@@ -219,6 +219,32 @@ The helper script reads this config if it exists. All values have sensible defau
 
 ---
 
+## Post-Merge Rollback
+
+After merging, the run skill validates the merge by running the project's test suite. If tests fail, the merge is automatically reverted.
+
+### Script
+
+```bash
+./lib/archeflow-rollback.sh <run_id> [--test-cmd <cmd>]
+```
+
+**Behavior:**
+1. Reads `test_command` from `.archeflow/config.yaml` (or uses `--test-cmd` override)
+2. Runs the test suite with a 5-minute timeout
+3. If tests pass: exits 0 (merge is good)
+4. If tests fail: runs `git revert --no-edit HEAD`, emits a `decision` event, exits 1
+5. Verifies HEAD is an ArcheFlow merge commit before reverting (warning if not, proceeds anyway)
+
+**Integration with run skill:** Called in section 4c (All Approved) after `archeflow-git.sh merge`. If it returns non-zero, the orchestrator cycles back with "integration test failure" feedback or reports to the user if max cycles are reached.
+
+**Configuration:** Set `test_command` in `.archeflow/config.yaml`:
+```yaml
+test_command: "npm test"       # or "pytest", "cargo test", etc.
+```
+
+---
+
 ## Safety Rules
 
 These rules are inherited from `archeflow:orchestration` and reinforced here:
diff --git a/skills/run/SKILL.md b/skills/run/SKILL.md
index 44fdce0..9eb6b2c 100644
--- a/skills/run/SKILL.md
+++ b/skills/run/SKILL.md
@@ -380,30 +380,19 @@ If all reviewers approved (and completion criteria met, if defined):
    ./lib/archeflow-git.sh merge "$RUN_ID" --no-ff
    ```
 
-4. **Post-merge test validation:**
+4. **Post-merge test validation** (using the auto-rollback script):
    ```bash
-   # Read test_command from config
-   TEST_CMD=$(grep -E "^test_command:" .archeflow/config.yaml | sed 's/^test_command:\s*//' | tr -d '"' || true)
-
-   if [[ -n "$TEST_CMD" ]]; then
-     echo "Running post-merge tests: $TEST_CMD"
-     if ! bash -c "$TEST_CMD"; then
-       echo "Post-merge tests FAILED — reverting merge..."
-       git revert --no-edit HEAD
-
-       # Emit decision event for the revert
-       ./lib/archeflow-event.sh "$RUN_ID" decision act "" \
-         '{"what":"post_merge_test","chosen":"revert","rationale":"test suite failed after merge"}' "$SEQ_CHECK_TO_ACT"
-
-       # If cycles remain, cycle back with integration test failure feedback
-       if [[ "$CYCLE" -lt "$MAX_CYCLES" ]]; then
-         echo "Cycling back with integration test failure feedback..."
-         # Build act-feedback.md with "integration test failure on main" as top finding
-         # Continue to step 4d (Issues Found)
-       else
-         echo "Max cycles reached. Reporting failure to user."
-         # Continue to step 4e (Max Cycles Reached)
-       fi
+   # Run tests and auto-revert if they fail
+   if ! ./lib/archeflow-rollback.sh "$RUN_ID"; then
+     # Rollback script already reverted HEAD and emitted decision event
+     # If cycles remain, cycle back with integration test failure feedback
+     if [[ "$CYCLE" -lt "$MAX_CYCLES" ]]; then
+       echo "Cycling back with integration test failure feedback..."
+       # Build act-feedback.md with "integration test failure on main" as top finding
+       # Continue to step 4d (Issues Found)
+     else
+       echo "Max cycles reached. Reporting failure to user."
+       # Continue to step 4e (Max Cycles Reached)
      fi
    fi
    ```