diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6c04f5338..ee6803955 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -3,8 +3,11 @@ name: CI
 on:
   push:
     branches: [main]
+  # No base-branch filter. A `branches:` allowlist here gates on the PR's *base*,
+  # so a PR stacked onto another PR's branch ran no CI at all (see #1440, which
+  # targets #1381's branch and has zero CI runs). Every PR gets the gate; the
+  # push trigger above stays scoped to main.
   pull_request:
-    branches: [main]
 
 permissions:
   contents: read
diff --git a/.github/workflows/codeql-analysis.yml b/.github/workflows/codeql-analysis.yml
index 4948f9539..bdad9e215 100644
--- a/.github/workflows/codeql-analysis.yml
+++ b/.github/workflows/codeql-analysis.yml
@@ -3,8 +3,9 @@ name: "CodeQL Analysis"
 on:
   push:
     branches: [ "main" ]
+  # No base-branch filter — see the note in ci.yml. CodeQL is a security gate;
+  # a stacked PR must not be able to skip it by targeting a non-main base.
   pull_request:
-    branches: [ "main" ]
   schedule:
     - cron: '0 6 * * 1'
 
diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index 521c11795..417bb83d7 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -6,8 +6,8 @@ on:
     paths-ignore:
       - "**/*.md"
       - "**/*.txt"
+  # No base-branch filter — see the note in ci.yml.
   pull_request:
-    branches: [main, develop]
     paths-ignore:
       - "**/*.md"
       - "**/*.txt"
diff --git a/.github/workflows/dependency-review.yml b/.github/workflows/dependency-review.yml
index a7efcad8c..1ff5a5eb5 100644
--- a/.github/workflows/dependency-review.yml
+++ b/.github/workflows/dependency-review.yml
@@ -1,8 +1,8 @@
 name: 🔍 Dependency Review
 
 on:
+  # No base-branch filter — see the note in ci.yml.
   pull_request:
-    branches: [ main, develop ]
     types: [opened, synchronize, reopened, ready_for_review]
 
 permissions:
diff --git a/.github/workflows/e2e-tests.yml b/.github/workflows/e2e-tests.yml
index 547c4b356..3bc529fd7 100644
--- a/.github/workflows/e2e-tests.yml
+++ b/.github/workflows/e2e-tests.yml
@@ -3,8 +3,8 @@ name: E2E Tests
 on:
   push:
     branches: [main]
+  # No base-branch filter — see the note in ci.yml.
   pull_request:
-    branches: [main]
 
 permissions:
   contents: read
diff --git a/.github/workflows/security.yml b/.github/workflows/security.yml
index 9f622ad5f..dee5f5ce8 100644
--- a/.github/workflows/security.yml
+++ b/.github/workflows/security.yml
@@ -3,8 +3,9 @@ name: Security Scan
 on:
   push:
     branches: [main]
+  # No base-branch filter — see the note in ci.yml. A stacked PR must not be
+  # able to skip the security scan by targeting a branch other than main.
   pull_request:
-    branches: [main]
   schedule:
     - cron: '0 0 * * 0'  # Weekly on Sunday
 
diff --git a/tests/unit/test_workflow_pr_gate_coverage.py b/tests/unit/test_workflow_pr_gate_coverage.py
new file mode 100644
index 000000000..64ebc39d1
--- /dev/null
+++ b/tests/unit/test_workflow_pr_gate_coverage.py
@@ -0,0 +1,77 @@
+"""Every PR quality gate must run on every PR, whatever its base branch.
+
+A `pull_request.branches:` allowlist filters on the PR's *base*, not its head.
+Six gates carried `branches: [main]`, so a PR stacked onto another PR's branch
+matched none of them and ran with no CI, no CodeQL, no security scan, no
+coverage, no e2e and no dependency review. #1440 -- a security fix targeting
+#1381's branch -- reached "ready for review" with zero CI runs that way.
+
+These tests pin the trigger shape so the allowlist cannot come back.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+import yaml
+
+WORKFLOWS = Path(__file__).resolve().parents[2] / ".github/workflows"
+
+# PR-triggered quality gates. Each must fire regardless of the PR's base branch.
+GATED_WORKFLOWS = [
+    "ci.yml",
+    "security.yml",
+    "coverage.yml",
+    "e2e-tests.yml",
+    "codeql-analysis.yml",
+    "dependency-review.yml",
+]
+
+
+def _triggers(filename: str) -> dict:
+    path = WORKFLOWS / filename
+    assert path.exists(), f"{filename} should exist"
+    workflow = yaml.safe_load(path.read_text())
+    # PyYAML parses the YAML 'on' key as the Python bool True.
+    return workflow[True]
+
+
+@pytest.mark.parametrize("filename", GATED_WORKFLOWS)
+def test_gate_triggers_on_pull_request(filename: str) -> None:
+    assert "pull_request" in _triggers(filename), (
+        f"{filename} must run on pull_request to gate PRs at all"
+    )
+
+
+@pytest.mark.parametrize("filename", GATED_WORKFLOWS)
+def test_gate_has_no_base_branch_allowlist(filename: str) -> None:
+    """The defect itself: a base-branch allowlist lets stacked PRs skip the gate."""
+    config = _triggers(filename)["pull_request"]
+    # A bare `pull_request:` parses to None, which is the shape we want.
+    if config is None:
+        return
+    assert "branches" not in config, (
+        f"{filename} filters pull_request on base branch {config['branches']!r}; "
+        "a PR stacked onto a non-main branch would skip this gate entirely"
+    )
+    assert "branches-ignore" not in config, (
+        f"{filename} uses branches-ignore on pull_request, which has the same "
+        "stacked-PR bypass as a branches allowlist"
+    )
+
+
+@pytest.mark.parametrize("filename", GATED_WORKFLOWS)
+def test_push_trigger_stays_scoped_to_main(filename: str) -> None:
+    """Widening the PR trigger must not widen the push trigger with it.
+
+    Un-scoping `push` would run the full suite twice on every branch push.
+    """
+    triggers = _triggers(filename)
+    if "push" not in triggers:
+        return
+    branches = triggers["push"].get("branches")
+    assert branches, f"{filename} push trigger should stay pinned to a branch list"
+    assert set(branches) <= {"main", "develop"}, (
+        f"{filename} push trigger widened to {branches!r}"
+    )