diff --git a/.github/workflows/sso-audit.yml b/.github/workflows/sso-audit.yml
new file mode 100644
index 00000000000..c1ea68127de
--- /dev/null
+++ b/.github/workflows/sso-audit.yml
@@ -0,0 +1,96 @@
+name: SSO fork audit
+
+# Runs scripts/sso-audit.sh against this fork's auth code to verify
+# satisfaction of the cross-app SSO contract at
+# awais786/sso-rules-moneta:openspec/specs/proxy-auth-middleware/spec.md.
+#
+# Covers the fork-side rows that foss-server-bundle-devstack's CI can't
+# check (no fork code on disk in the bundle): today rows 14, 20, 21 from
+# SKILL.md §5. Exits 1 on security-critical violations (row 20 — session-
+# identity reconciliation) so the merge gate blocks the stale-session
+# leak class of bug.
+#
+# When upstream sso-rules-moneta adds a new fork-side row, vendor the
+# updated check into scripts/sso-audit.sh and re-run this workflow.
+
+on:
+  pull_request:
+    paths:
+      - 'apps/api/plane/authentication/**'
+      - 'apps/web/core/store/user/**'
+      - 'apps/web/core/services/auth.service.ts'
+      - 'apps/web/core/lib/wrappers/authentication-wrapper.tsx'
+      - 'scripts/sso-audit.sh'
+      - '.github/workflows/sso-audit.yml'
+  push:
+    branches: [foss-main]
+  schedule:
+    # 09:00 UTC every Monday — pre-week sanity check
+    - cron: '0 9 * * 1'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  sso-fork-audit:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+
+      - name: Run fork audit
+        id: audit
+        run: |
+          set -o pipefail
+          if bash scripts/sso-audit.sh | tee audit-output.md; then
+            echo "audit_exit=0" >> "$GITHUB_OUTPUT"
+          else
+            echo "audit_exit=$?" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Publish to job summary
+        if: always()
+        run: cat audit-output.md >> "$GITHUB_STEP_SUMMARY"
+
+      - name: Upload audit report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: sso-fork-audit-report
+          path: audit-output.md
+
+      - name: Fail on security-critical violations
+        if: steps.audit.outputs.audit_exit != '0'
+        run: |
+          echo "::error::Security-critical SSO contract violation in fork audit. See table for the failing row and fix."
+          exit 1
+
+  sso-fork-audit-comment:
+    needs: sso-fork-audit
+    if: |
+      always() &&
+      needs.sso-fork-audit.result != 'cancelled' &&
+      github.event_name == 'pull_request' &&
+      github.event.pull_request.head.repo.full_name == github.repository
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+    steps:
+      - name: Download audit report
+        uses: actions/download-artifact@v4
+        with:
+          name: sso-fork-audit-report
+
+      - name: Post sticky PR comment
+        continue-on-error: true
+        uses: marocchino/sticky-pull-request-comment@v2
+        with:
+          header: sso-fork-audit
+          path: audit-output.md
diff --git a/.gitignore b/.gitignore
index 541cc29f087..96245b105a9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -109,7 +109,9 @@ build/
 build/
 .react-router/
 temp/
-scripts/
+scripts/*
+# Tracked exceptions inside scripts/ — vendored or fork-specific CI tooling.
+!scripts/sso-audit.sh
 
 # SSO design specs (implemented, code is source of truth)
 docs/cognito_*.md
diff --git a/scripts/sso-audit.sh b/scripts/sso-audit.sh
new file mode 100755
index 00000000000..7914f08db66
--- /dev/null
+++ b/scripts/sso-audit.sh
@@ -0,0 +1,269 @@
+#!/usr/bin/env bash
+#
+# sso-audit.sh — Plane-side fork audit against the cross-app SSO contract.
+#
+# ============================================================================
+# Covers the fork-side rows of awais786/sso-rules-moneta:openspec/specs/
+# proxy-auth-middleware/spec.md that a deterministic bash check can verify
+# against Plane's source tree. Catches regressions BEFORE they reach
+# foss-server-bundle-devstack, where the same rows currently emit `?` (no
+# fork code on disk in the bundle CI).
+#
+# Together with the bundle-side audit (foss-server-bundle-devstack/scripts/
+# audit-sso.sh), the contract is now ~14 of 21 rows deterministic without
+# any LLM invocation. The remaining rows (identity-managed UI gating,
+# display-name UUID check) need either runtime SSO state or AST-level
+# semantic analysis — those defer to the LLM-backed
+# /sso-rules:audit-all-apps slash command.
+#
+# Exit codes:
+#   0 — no SECURITY-CRITICAL rows failed. Non-security rows may still be
+#       reported as ❌; those findings are informational/non-gating.
+#   1 — at least one SECURITY-CRITICAL row failed (today: row 20 session-
+#       identity reconciliation). These violations re-open the cross-user
+#       identity-leak class of bug.
+#
+# Rows covered:
+#   Row 14 — logout shape: SPA logout file MUST NOT call /oauth2/sign_out.
+#            (The portal-host redirect target and the no-POST-/auth/sign-out/
+#            properties from logout-flow spec are NOT checked here — they
+#            need either runtime context or AST-level analysis. The bash
+#            audit covers only the literal /oauth2/sign_out grep, which is
+#            the most common regression vector.)
+#   Row 20 — session-identity reconciliation (Rule 2 mismatch flush):
+#            proxy_auth.py MUST call django.contrib.auth.logout(request)
+#            on identity mismatch. Without this, the stale-session-on-user-
+#            switch leak returns.  SECURITY-CRITICAL.
+#   Row 21 — email-shape detection MUST NOT use polynomial-backtracking
+#            regex. Plane uses substring check today, so this row is
+#            informational — the audit fires only if a regex is reintroduced.
+#
+# Source of truth: awais786/sso-rules-moneta:openspec/specs/proxy-auth-
+# middleware/spec.md. When upstream adds a new fork-side row, vendor the
+# updated check here.
+# ============================================================================
+
+set -euo pipefail
+
+PROXY_AUTH="apps/api/plane/authentication/middleware/proxy_auth.py"
+PROXY_AUTH_UTILS="apps/api/plane/authentication/middleware/proxy_auth_utils.py"
+LOGOUT_SPA="apps/web/core/store/user/index.ts"
+
+# Output state — populated by each check_row_N function, printed at the end.
+declare -a ROW_STATUS=()
+declare -a ROW_TITLES=(
+  "logout shape: SPA logout does not call /oauth2/sign_out"
+  "session-identity reconciliation present (Rule 2 mismatch flush)"
+  "email-shape detection uses substring/indexOf, not polynomial regex"
+)
+declare -a ROW_NOTES=()
+
+# Row numbers per the cross-app SKILL.md §5 table. We only emit a subset
+# here; bundle CI emits 1-21.
+declare -a ROW_NUMBERS=(14 20 21)
+
+# Security-critical row indices (0-indexed into ROW_NUMBERS above).
+SECURITY_CRITICAL=(1)   # index 1 → row 20
+
+SECURITY_CRITICAL_FAILS=0
+
+record() {
+  local idx=$1 status=$2 note=$3
+  ROW_STATUS[$idx]="$status"
+  ROW_NOTES[$idx]="$note"
+  if [[ "$status" == "❌" ]]; then
+    for c in "${SECURITY_CRITICAL[@]}"; do
+      if [[ "$c" -eq "$idx" ]]; then
+        SECURITY_CRITICAL_FAILS=$((SECURITY_CRITICAL_FAILS + 1))
+        return
+      fi
+    done
+  fi
+}
+
+escape_markdown_cell() {
+  # Escape table-sensitive characters so notes render as a single markdown cell.
+  # Input: arbitrary note text. Output: `|` as HTML entity + newlines as <br>.
+  local cell="$1"
+  cell=${cell//|/&#124;}
+  cell=${cell//$'\n'/'<br>'}
+  printf '%s' "$cell"
+}
+
+# ============================================================================
+# Row 14 (idx 0): logout shape — narrow check
+#
+# SPA logout MUST NOT contain `/oauth2/sign_out` literal — the bundle's
+# logout model is navigation-only at the per-app layer. The portal handles
+# oauth2-proxy clearing. This check enforces only that property; the other
+# properties from logout-flow spec (portal-host redirect target, no POST
+# /auth/sign-out/) are not verified here.
+# ============================================================================
+check_row_14() {
+  if [[ ! -f "$LOGOUT_SPA" ]]; then
+    record 0 "?" "$LOGOUT_SPA not found — skipping"
+    return
+  fi
+
+  if grep -qE '/oauth2/sign_?out' "$LOGOUT_SPA"; then
+    local line
+    line=$(grep -nE '/oauth2/sign_?out' "$LOGOUT_SPA" | head -1)
+    record 0 "❌" "Logout calls \`/oauth2/sign_out\` at $LOGOUT_SPA:$line — per logout-flow spec, per-app Logout is navigation-only. Drop the call; portal 'Logout all' handles oauth2-proxy clearing."
+    return
+  fi
+
+  record 0 "✅" "$LOGOUT_SPA does not invoke \`/oauth2/sign_out\` (this row verifies only that the SPA doesn't try to clear the upstream proxy cookie itself; that's the portal's job. The SPA MAY still POST \`/auth/sign-out/\` — tolerated drift, see logout-flow spec)"
+}
+
+# ============================================================================
+# Row 20 (idx 1): session-identity reconciliation
+#
+# proxy_auth.py MUST call django.contrib.auth.logout (imported as `logout` or
+# under any local alias) on identity mismatch. The presence of the import +
+# call is the deterministic signal; the bash audit can't verify the call
+# site's *position* relative to the mismatch detection, only that it exists.
+# That's a spec-conformance approximation; the test suite at
+# apps/api/plane/authentication/tests/test_proxy_auth.py pins the exact
+# behaviour.
+#
+# The detection is resilient to:
+#   - whitespace around the argument: `logout(request)`, `logout( request )`,
+#     `logout(\nrequest\n)`
+#   - keyword form: `logout(request=request)`
+#   - parenthesized multiline imports:
+#       from django.contrib.auth import (
+#           login,
+#           logout,
+#       )
+#   - aliased imports: `from django.contrib.auth import logout as django_logout`
+#   - mixed imports on one line: `from django.contrib.auth import login, logout`
+#
+# SECURITY-CRITICAL: without this call, the stale-session leak returns.
+# ============================================================================
+check_row_20() {
+  if [[ ! -f "$PROXY_AUTH" ]]; then
+    record 1 "?" "$PROXY_AUTH not found — skipping"
+    return
+  fi
+
+  # Resolve the in-scope name for django.contrib.auth.logout.
+  # If the file imports it under an alias, use that. Otherwise default to
+  # `logout`. Use python -c so we correctly handle multiline parenthesized
+  # imports without trying to write a multi-line regex in bash.
+  local logout_name
+  logout_name=$(python3 - "$PROXY_AUTH" <<'PY' 2>/dev/null || true
+import ast, sys
+src = open(sys.argv[1]).read()
+try:
+    tree = ast.parse(src)
+except SyntaxError:
+    sys.exit(0)
+for node in ast.walk(tree):
+    if isinstance(node, ast.ImportFrom) and node.module == "django.contrib.auth":
+        for alias in node.names:
+            if alias.name == "logout":
+                print(alias.asname or "logout")
+                sys.exit(0)
+PY
+)
+
+  if [[ -z "$logout_name" ]]; then
+    record 1 "❌" "$PROXY_AUTH does NOT import django.contrib.auth.logout. The cross-app spec (proxy-auth-middleware Rule 2) requires the middleware to call logout(request) when the proxy header asserts a different identity than the existing Django session. Without it, the stale-session-on-user-switch leak returns. Fix: add \`from django.contrib.auth import logout\` AND invoke \`logout(request)\` immediately on mismatch, before any bail-out path."
+    return
+  fi
+
+  # Look for a call to <logout_name>(...) anywhere in the file. The argument
+  # can include whitespace, line breaks, or `request=request` keyword form;
+  # the audit only cares that the call exists, not its exact shape.
+  #
+  # Portable word boundary at the start: `(^|[^[:alnum:]_])` matches either
+  # start-of-line or any non-word character before the alias name. Using
+  # POSIX character classes rather than `\b` because `\b` is a GNU extension
+  # to `grep -E` and is undefined on BSD/POSIX strict implementations
+  # (`grep` on macOS, busybox, Alpine, etc. may interpret it as literal
+  # backspace or just `b`). The right side doesn't need a boundary because
+  # `[[:space:]]*\(` already requires the next non-space char to be `(`.
+  local call_pattern="(^|[^[:alnum:]_])${logout_name}[[:space:]]*\\("
+  if grep -qE "$call_pattern" "$PROXY_AUTH"; then
+    record 1 "✅" "django.contrib.auth.logout imported (as \`$logout_name\`) and invoked at least once in $PROXY_AUTH — Rule 2 mismatch flush in place"
+    return
+  fi
+
+  record 1 "❌" "$PROXY_AUTH imports django.contrib.auth.logout (as \`$logout_name\`) but never calls it. Fix: invoke \`$logout_name(request)\` on identity mismatch before falling through to the unauthenticated path."
+}
+
+# ============================================================================
+# Row 21 (idx 2): polynomial-regex avoidance in email-shape detection
+#
+# Plane uses substring check (`"@" in email`) today, so this is a regression
+# guard. The audit fires only if a Python regex matching the unanchored
+# `[^\s@]+@[^\s@]+\.[^\s@]+` pattern is introduced. CodeQL's
+# `py/polynomial-redos` (or `js/polynomial-redos`) flags this on adversarial
+# input.
+# ============================================================================
+check_row_21() {
+  local files=()
+  [[ -f "$PROXY_AUTH" ]] && files+=("$PROXY_AUTH")
+  [[ -f "$PROXY_AUTH_UTILS" ]] && files+=("$PROXY_AUTH_UTILS")
+
+  if [[ ${#files[@]} -eq 0 ]]; then
+    record 2 "?" "No proxy_auth files found — skipping"
+    return
+  fi
+
+  # Look for the canonical polynomial-backtracking shape:
+  #   [^\s@]+@[^\s@]+\.[^\s@]+
+  # in any of the inspected files. Allow trivial whitespace variations.
+  local hits
+  hits=$(grep -nE '\[\^[\\\\]s@\]\+@\[\^[\\\\]s@\]\+\\\.\[\^[\\\\]s@\]\+' "${files[@]}" 2>/dev/null || true)
+
+  if [[ -n "$hits" ]]; then
+    record 2 "❌" "Polynomial-backtracking email-shape regex detected: $hits. Rewrite to indexOf/substring-based check per openspec proxy-auth-middleware §'email-shape detection SHALL avoid polynomial-backtracking regex'. Reference: Outline's normalizeProxyEmail in Pressingly/outline#19."
+    return
+  fi
+
+  record 2 "✅" "No polynomial-backtracking email-shape regex in ${files[*]}; using substring check or other O(n) detection"
+}
+
+# ============================================================================
+# Run checks
+# ============================================================================
+check_row_14
+check_row_20
+check_row_21
+
+# ============================================================================
+# Print table
+# ============================================================================
+echo "## Plane SSO Fork Audit"
+echo
+echo "Cross-app contract: https://github.com/awais786/sso-rules-moneta/blob/main/openspec/specs/proxy-auth-middleware/spec.md"
+echo "Row numbers match the 21-row table at https://github.com/awais786/sso-rules-moneta/blob/main/skills/app-rules/SKILL.md#5-report"
+echo
+echo "| Row | Invariant | Status | Notes |"
+echo "|-----|-----------|--------|-------|"
+for i in "${!ROW_TITLES[@]}"; do
+  note="$(escape_markdown_cell "${ROW_NOTES[$i]:-}")"
+  printf "| %d | %s | %s | %s |\n" \
+    "${ROW_NUMBERS[$i]}" "${ROW_TITLES[$i]}" "${ROW_STATUS[$i]:-?}" "$note"
+done
+echo
+
+# ============================================================================
+# Summary + exit code
+# ============================================================================
+TOTAL_FAILS=0
+for s in "${ROW_STATUS[@]}"; do
+  [[ "$s" == "❌" ]] && TOTAL_FAILS=$((TOTAL_FAILS + 1))
+done
+
+if [[ "$TOTAL_FAILS" -eq 0 ]]; then
+  echo "**All fork-side invariants hold.**"
+  exit 0
+fi
+
+echo "**$TOTAL_FAILS violations.** Security-critical (row 20): $SECURITY_CRITICAL_FAILS."
+if [[ "$SECURITY_CRITICAL_FAILS" -gt 0 ]]; then
+  exit 1
+fi
+exit 0