diff --git a/.github/scripts/authorize-claude-workflow.sh b/.github/scripts/authorize-claude-workflow.sh
new file mode 100644
index 000000000..5498182fd
--- /dev/null
+++ b/.github/scripts/authorize-claude-workflow.sh
@@ -0,0 +1,97 @@
+#!/usr/bin/env bash
+# Decide whether the trigger (PR author, comment author, labeler) is
+# authorized to spawn a Claude workflow on this repo. Driven by the
+# `authorize` job in claude-review.yml / claude-mention.yml /
+# claude-issue-to-pr.yml.
+#
+# Trust set: every `@HarperFast/<team>` handle in this repo's
+# `.github/CODEOWNERS`. Same set as the people we trust to review code,
+# aligned by construction. Falls back to `@HarperFast/developers` if
+# CODEOWNERS is missing, empty, unparseable, or contains no HarperFast
+# handles. External-org handles in CODEOWNERS are deliberately ignored
+# — only HarperFast members are admitted.
+#
+# Inputs:
+#   USERS_TO_CHECK     — newline-separated logins; ALL must pass.
+#                        Empty / whitespace-only entries are skipped.
+#   ADMIT_CLAUDE_BOT   — "true" admits `claude[bot]` without a team
+#                        check (used by claude-review for AI-authored
+#                        PRs from the issue-to-PR pipeline). Anything
+#                        else requires team membership for every user.
+#   DEFAULT_TOKEN      — token for the CODEOWNERS read (typically
+#                        $GITHUB_TOKEN; needs `contents: read`).
+#   ORG_TOKEN          — token for `orgs/.../teams/.../memberships/...`
+#                        (App-installation token with `Members: Read`,
+#                        scoped to this `authorize` job only).
+#   GITHUB_REPOSITORY  — owner/repo (auto-set by GitHub Actions).
+#   GITHUB_OUTPUT      — output file path.
+#
+# Outputs (to $GITHUB_OUTPUT):
+#   authorized=true|false
+set -uo pipefail
+
+# Resolve the trust set from CODEOWNERS. The default token reads the
+# workflow repo's own .github/CODEOWNERS via the contents API.
+# Anything missing / empty / unparseable / containing no HarperFast
+# handles falls back to the default team.
+CODEOWNERS=$(GH_TOKEN="$DEFAULT_TOKEN" gh api \
+  "repos/${GITHUB_REPOSITORY}/contents/.github/CODEOWNERS" \
+  --jq '.content' 2>/dev/null | base64 -d 2>/dev/null || true)
+TEAMS=$(printf '%s' "$CODEOWNERS" | grep -oE '@HarperFast/[a-zA-Z0-9_-]+' | sort -u | sed 's|@HarperFast/||' || true)
+
+if [ -z "$TEAMS" ]; then
+  echo "::notice::No @HarperFast/<team> handles found in .github/CODEOWNERS (missing, empty, or only external orgs). Defaulting to developers."
+  TEAMS="developers"
+fi
+
+# Fail closed if USERS_TO_CHECK is empty or whitespace-only. The
+# main loop below skips empty entries with `[ -z "$user" ] && continue`
+# and would otherwise fall through to `authorized=true` if there was
+# nothing to check. An authorize job that forgot to set USERS_TO_CHECK
+# (or a malicious change that removed it) must NOT silently admit
+# every event — refuse here.
+if [ -z "${USERS_TO_CHECK//[[:space:]]/}" ]; then
+  echo "::error::USERS_TO_CHECK is empty or whitespace-only — denying by default. The authorize job must explicitly pass at least one login (PR author, commenter, labeler, etc.)."
+  echo "authorized=false" >> "$GITHUB_OUTPUT"
+  exit 0
+fi
+
+echo "Trust set (HarperFast teams from CODEOWNERS):"
+for t in $TEAMS; do echo "  - @HarperFast/$t"; done
+
+# is_authorized <login>
+# Admits claude[bot] iff ADMIT_CLAUDE_BOT=true; otherwise tries each
+# team in the trust set in order. Returns 0 on the first hit.
+is_authorized() {
+  local user="$1"
+
+  if [ "${ADMIT_CLAUDE_BOT:-false}" = "true" ] && [ "$user" = "claude[bot]" ]; then
+    echo "  → admitted: claude[bot]"
+    return 0
+  fi
+
+  for team in $TEAMS; do
+    # /orgs/{org}/teams/{team_slug}/memberships/{username}
+    # returns 200 for active members, 404 otherwise.
+    if GH_TOKEN="$ORG_TOKEN" gh api "orgs/HarperFast/teams/${team}/memberships/${user}" --silent >/dev/null 2>&1; then
+      echo "  → admitted via @HarperFast/${team} membership"
+      return 0
+    fi
+  done
+
+  echo "  → not a member of any HarperFast team in the trust set"
+  return 1
+}
+
+while IFS= read -r raw_user; do
+  user="$(printf '%s' "$raw_user" | awk '{$1=$1;print}')"
+  [ -z "$user" ] && continue
+  echo "Checking: $user"
+  if ! is_authorized "$user"; then
+    echo "User '$user' not authorized. Skipping the gated job."
+    echo "authorized=false" >> "$GITHUB_OUTPUT"
+    exit 0
+  fi
+done <<< "${USERS_TO_CHECK:-}"
+
+echo "authorized=true" >> "$GITHUB_OUTPUT"
diff --git a/.github/scripts/validate-auth-gate-invariants.sh b/.github/scripts/validate-auth-gate-invariants.sh
new file mode 100644
index 000000000..cac591a7f
--- /dev/null
+++ b/.github/scripts/validate-auth-gate-invariants.sh
@@ -0,0 +1,106 @@
+#!/usr/bin/env bash
+# Validate that the AI workflow auth gate structure is preserved
+# across all `claude-*.yml` workflows. STRUCTURAL lint, not a semantic
+# test — catches the obvious attacks (delete the authorize job, drop
+# the `needs:` dependency, broaden permissions, change the
+# if-expression to a tautology). Subtle attacks (e.g., modifying the
+# bash logic inside the auth check to admit everyone) are out of
+# scope for this validator and are caught by CODEOWNERS review on
+# `.github/` changes.
+#
+# Defense in depth: branch-protection on `main` should make this
+# workflow's job a REQUIRED status check.
+#
+# Inputs (none — runs in the workflow checkout). Validates:
+#   .github/workflows/claude-*.yml
+#
+# Exit code:
+#   0  all workflows pass
+#   1  any check failed (errors emitted as ::error::)
+set -uo pipefail
+
+fail() {
+  echo "::error::$1"
+  exit 1
+}
+
+# yq is pre-installed on ubuntu-latest runners.
+command -v yq >/dev/null || fail "yq not available on runner"
+
+shopt -s nullglob
+files=(.github/workflows/claude-*.yml)
+if [ "${#files[@]}" -eq 0 ]; then
+  echo "No claude-*.yml workflows found; nothing to validate."
+  exit 0
+fi
+
+for f in "${files[@]}"; do
+  echo ""
+  echo "=== Validating $f ==="
+
+  # 1. The authorize job exists.
+  yq -e '.jobs.authorize' "$f" >/dev/null \
+    || fail "$f: missing 'authorize' job"
+
+  # 2. authorize.outputs.authorized is wired to some step output.
+  output_expr=$(yq -r '.jobs.authorize.outputs.authorized // ""' "$f")
+  [ -n "$output_expr" ] \
+    || fail "$f: authorize job has no outputs.authorized"
+  echo "$output_expr" | grep -q 'steps\..*\.outputs\.authorized' \
+    || fail "$f: authorize.outputs.authorized must come from a step output (got: $output_expr)"
+
+  # 3. authorize uses actions/create-github-app-token (pinned to a SHA).
+  app_token_step=$(yq -r '.jobs.authorize.steps[] | select(.uses != null) | .uses' "$f" | grep '^actions/create-github-app-token@' || true)
+  [ -n "$app_token_step" ] \
+    || fail "$f: authorize doesn't use actions/create-github-app-token"
+  echo "$app_token_step" | grep -qE '@[0-9a-f]{40}( |$)' \
+    || fail "$f: actions/create-github-app-token must be pinned to a 40-char SHA (got: $app_token_step)"
+
+  # 4. authorize.permissions doesn't grant any write-level scope.
+  write_perms=$(yq -r '.jobs.authorize.permissions | (.[] // "") | select(. == "write")' "$f" 2>/dev/null || true)
+  [ -z "$write_perms" ] \
+    || fail "$f: authorize.permissions grants 'write' on at least one scope — auth job must be read-only"
+
+  # 5. Required secrets are referenced (the auth check can't work without them).
+  grep -q 'HARPERFAST_AI_CLIENT_ID' "$f" \
+    || fail "$f: HARPERFAST_AI_CLIENT_ID secret not referenced"
+  grep -q 'HARPERFAST_AI_APP_PRIVATE_KEY' "$f" \
+    || fail "$f: HARPERFAST_AI_APP_PRIVATE_KEY secret not referenced"
+
+  # 6. The authorize job sets USERS_TO_CHECK on at least one of its
+  #    steps. The auth script (`authorize-claude-workflow.sh`) fails
+  #    closed if USERS_TO_CHECK is empty, but the workflow still
+  #    shouldn't ship without it — make the omission a structural
+  #    error rather than a silent runtime denial. Defense in depth
+  #    against a PR that drops the env var thinking the script will
+  #    "do the right thing".
+  users_to_check=$(yq -r '[.jobs.authorize.steps[].env.USERS_TO_CHECK // empty] | .[0] // ""' "$f" 2>/dev/null)
+  [ -n "$users_to_check" ] \
+    || fail "$f: authorize job has no step setting USERS_TO_CHECK env var — the auth script needs at least one login to check (PR author, commenter, labeler, etc.)"
+
+  # 7. Every non-authorize job has `needs: authorize` and a strict
+  #    if-expression of exactly: needs.authorize.outputs.authorized == 'true'
+  #    (whitespace normalized). Stricter than substring match —
+  #    rules out tautologies like `... || true`.
+  other_jobs=$(yq -r '.jobs | keys | .[]' "$f" | grep -v '^authorize$' || true)
+  [ -n "$other_jobs" ] \
+    || fail "$f: no non-authorize job found — workflow has nothing gated"
+
+  for j in $other_jobs; do
+    needs=$(yq -r ".jobs.${j}.needs // \"\"" "$f")
+    [ "$needs" = "authorize" ] \
+      || fail "$f: job '$j' must have 'needs: authorize' (got: $needs)"
+
+    if_expr=$(yq -r ".jobs.${j}.if // \"\"" "$f")
+    # Normalize whitespace and quotes for the comparison.
+    normalized=$(echo "$if_expr" | tr -s ' ' | tr -d "\n")
+    expected="needs.authorize.outputs.authorized == 'true'"
+    [ "$normalized" = "$expected" ] \
+      || fail "$f: job '$j' if: must be exactly \"$expected\" — no compound expressions, no tautologies (got: $if_expr)"
+  done
+
+  echo "  ✓ $f passed"
+done
+
+echo ""
+echo "All claude-*.yml workflows pass auth gate invariants."
diff --git a/.github/workflows/auth-gate-invariants.yml b/.github/workflows/auth-gate-invariants.yml
new file mode 100644
index 000000000..77d0b8b71
--- /dev/null
+++ b/.github/workflows/auth-gate-invariants.yml
@@ -0,0 +1,36 @@
+name: Auth gate invariants
+
+# Validates that the AI workflow auth gate structure is preserved.
+# Runs on any PR that touches a `claude-*.yml` workflow file or this
+# validator itself.
+#
+# This is a STRUCTURAL lint, not a semantic test. It catches the
+# obvious attacks (delete the authorize job, drop the `needs:`
+# dependency, broaden permissions, change the if-expression to a
+# tautology). Subtle attacks (e.g., modifying the bash logic inside
+# the auth check to admit everyone) are caught by CODEOWNERS review,
+# which requires both @HarperFast/developers and @HarperFast/devops
+# approval on `.github/` changes.
+#
+# Defense in depth — make this workflow a REQUIRED status check on
+# `main` via branch protection so PRs can't merge without it passing.
+
+on:
+  pull_request:
+    paths:
+      - '.github/workflows/claude-*.yml'
+      - '.github/workflows/auth-gate-invariants.yml'
+      - '.github/scripts/validate-auth-gate-invariants.sh'
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    timeout-minutes: 2
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+
+      - name: Validate auth gate structure
+        run: bash .github/scripts/validate-auth-gate-invariants.sh
diff --git a/.github/workflows/claude-issue-to-pr.yml b/.github/workflows/claude-issue-to-pr.yml
index d41cfd2a3..b751ad2ed 100644
--- a/.github/workflows/claude-issue-to-pr.yml
+++ b/.github/workflows/claude-issue-to-pr.yml
@@ -20,18 +20,65 @@ concurrency:
   cancel-in-progress: false
 
 jobs:
+  authorize:
+    # Single source of truth for "is this label trigger allowed to
+    # spawn Claude on this repo?". The `work` job below has ONE `if:`
+    # that depends on this — no step-level guards, no individual user
+    # list.
+    #
+    # Cheap pre-filter at job level: explicit whitelist of allowed
+    # labels (NOT `startsWith('claude-fix:')`, which would match typoed
+    # variants like `claude-fix:typos`).
+    #
+    # We check the LABELER (`github.actor`), not the issue author. The
+    # labeler must already have at least triage permission to apply a
+    # label; a maintainer labeling an external-author issue is a
+    # legitimate way to invoke the agent on community reports.
+    #
+    # Trust set: the @HarperFast teams listed in this repo's
+    # `.github/CODEOWNERS`. Defaults to `@HarperFast/developers` if the
+    # file is missing, empty, or has no HarperFast handles. External-
+    # org handles are deliberately ignored.
+    #
+    # Required (organization-level) secrets:
+    #   - HARPERFAST_AI_CLIENT_ID       (the App's Client ID, like Iv23li…)
+    #   - HARPERFAST_AI_APP_PRIVATE_KEY (.pem file contents)
+    if: contains(fromJSON('["claude-fix:typo","claude-fix:docs","claude-fix:deps","claude-fix:bug"]'), github.event.label.name)
+    runs-on: ubuntu-latest
+    timeout-minutes: 1
+    permissions:
+      contents: read # for the .github/CODEOWNERS fetch
+    outputs:
+      authorized: ${{ steps.check.outputs.authorized }}
+    steps:
+      - name: Mint org-read token
+        id: app-token
+        uses: actions/create-github-app-token@1b10c78c7865c340bc4f6099eb2f838309f1e8c3 # v3.1.1
+        with:
+          client-id: ${{ secrets.HARPERFAST_AI_CLIENT_ID }}
+          private-key: ${{ secrets.HARPERFAST_AI_APP_PRIVATE_KEY }}
+          owner: HarperFast
+
+      - name: Checkout (for CODEOWNERS read)
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+        with:
+          sparse-checkout: |
+            .github/CODEOWNERS
+            .github/scripts/authorize-claude-workflow.sh
+          sparse-checkout-cone-mode: false
+
+      - name: Check labeler authorization
+        id: check
+        env:
+          DEFAULT_TOKEN: ${{ github.token }}
+          ORG_TOKEN: ${{ steps.app-token.outputs.token }}
+          ADMIT_CLAUDE_BOT: 'false'
+          USERS_TO_CHECK: ${{ github.actor }}
+        run: bash .github/scripts/authorize-claude-workflow.sh
+
   work:
-    # Only trigger for `claude-fix:*` labels AND when the issue was
-    # opened by a HarperFast org member or collaborator. Labels added
-    # to issues opened by outside contributors are ignored to keep
-    # the trigger surface tight during calibration.
-    # Explicit whitelist of allowed labels — `startsWith('claude-fix:')`
-    # would match typoed variants (`claude-fix:typos`, `claude-fix:foo`)
-    # and the agent would waste turns trying to interpret them.
-    if: >-
-      contains(fromJSON('["claude-fix:typo","claude-fix:docs","claude-fix:deps","claude-fix:bug"]'), github.event.label.name) &&
-      contains(fromJSON('["OWNER", "MEMBER", "COLLABORATOR"]'),
-      github.event.issue.author_association)
+    needs: authorize
+    if: needs.authorize.outputs.authorized == 'true'
     runs-on: ubuntu-latest
     timeout-minutes: 25
     permissions:
diff --git a/.github/workflows/claude-mention.yml b/.github/workflows/claude-mention.yml
index afccd30be..b847aaf8e 100644
--- a/.github/workflows/claude-mention.yml
+++ b/.github/workflows/claude-mention.yml
@@ -17,16 +17,61 @@ concurrency:
   cancel-in-progress: false
 
 jobs:
+  authorize:
+    # Single source of truth for "is this commenter allowed to trigger
+    # Claude on this repo?". The `work` job below has ONE `if:` that
+    # depends on this — no step-level guards, no individual user list.
+    #
+    # Cheap pre-filter at job level: comment must mention `@claude`.
+    # The first-non-whitespace-token precision check is in the work
+    # job's `Parse mention` step.
+    #
+    # Trust set: the @HarperFast teams listed in this repo's
+    # `.github/CODEOWNERS`. Defaults to `@HarperFast/developers` if the
+    # file is missing, empty, or has no HarperFast handles. External-
+    # org handles are deliberately ignored — we only admit HarperFast
+    # members.
+    #
+    # Required (organization-level) secrets:
+    #   - HARPERFAST_AI_CLIENT_ID       (the App's Client ID, like Iv23li…)
+    #   - HARPERFAST_AI_APP_PRIVATE_KEY (.pem file contents)
+    if: contains(github.event.comment.body, '@claude')
+    runs-on: ubuntu-latest
+    timeout-minutes: 1
+    permissions:
+      # contents: read for the .github/CODEOWNERS fetch via default token.
+      contents: read
+    outputs:
+      authorized: ${{ steps.check.outputs.authorized }}
+    steps:
+      - name: Mint org-read token
+        id: app-token
+        uses: actions/create-github-app-token@1b10c78c7865c340bc4f6099eb2f838309f1e8c3 # v3.1.1
+        with:
+          client-id: ${{ secrets.HARPERFAST_AI_CLIENT_ID }}
+          private-key: ${{ secrets.HARPERFAST_AI_APP_PRIVATE_KEY }}
+          owner: HarperFast
+
+      - name: Checkout (for CODEOWNERS read)
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+        with:
+          sparse-checkout: |
+            .github/CODEOWNERS
+            .github/scripts/authorize-claude-workflow.sh
+          sparse-checkout-cone-mode: false
+
+      - name: Check commenter authorization
+        id: check
+        env:
+          DEFAULT_TOKEN: ${{ github.token }}
+          ORG_TOKEN: ${{ steps.app-token.outputs.token }}
+          ADMIT_CLAUDE_BOT: 'false'
+          USERS_TO_CHECK: ${{ github.event.comment.user.login }}
+        run: bash .github/scripts/authorize-claude-workflow.sh
+
   work:
-    # Belt-and-suspenders gate:
-    # 1. Comment must contain the trigger phrase.
-    # 2. Commenter must be HarperFast org OWNER / MEMBER or a repo
-    #    COLLABORATOR (the action also performs its own write-access
-    #    check on the actor as a fallback).
-    if: >-
-      contains(github.event.comment.body, '@claude') &&
-      contains(fromJSON('["OWNER", "MEMBER", "COLLABORATOR"]'),
-      github.event.comment.author_association)
+    needs: authorize
+    if: needs.authorize.outputs.authorized == 'true'
     runs-on: ubuntu-latest
     timeout-minutes: 20
     permissions:
diff --git a/.github/workflows/claude-review.yml b/.github/workflows/claude-review.yml
index 14d26a178..f736e1d60 100644
--- a/.github/workflows/claude-review.yml
+++ b/.github/workflows/claude-review.yml
@@ -9,15 +9,79 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  authorize:
+    # Single source of truth for "is this PR allowed to trigger Claude
+    # on this repo?". The `review` job below has ONE `if:` that depends
+    # on this — no step-level guards, no individual user list to
+    # maintain.
+    #
+    # Trust set: the @HarperFast teams listed in this repo's
+    # `.github/CODEOWNERS`. Same set as the people we trust to review
+    # code; alignment by construction. If CODEOWNERS is missing,
+    # empty, or has no `@HarperFast/<team>` handles, we fall back to
+    # `@HarperFast/developers` as the default. External-org handles in
+    # CODEOWNERS (e.g. `@SomeOtherOrg/x`) are deliberately ignored —
+    # we only admit HarperFast members. `claude[bot]` is admitted
+    # explicitly so AI-authored PRs from the issue-to-PR pipeline get
+    # reviewed.
+    #
+    # We check TWO identities; both must be authorized:
+    #   * `pull_request.user.login` — the PR's original author.
+    #   * `github.actor` — whoever triggered THIS specific event (the
+    #     pusher on `synchronize`, etc.). A non-trusted user pushing
+    #     to a trusted user's PR branch changes the actor without
+    #     changing the PR author; we want to refuse those events.
+    #
+    # Team-membership reads need an `Organization: Members: Read`
+    # token, which the default `GITHUB_TOKEN` lacks. We mint an
+    # installation token from an org-wide HarperFast GitHub App
+    # (Members: Read scope only) and use it ONLY in this job — the
+    # work job uses the default `GITHUB_TOKEN`, so the org-read
+    # capability never reaches the agent step.
+    #
+    # Required (organization-level) secrets:
+    #   - HARPERFAST_AI_CLIENT_ID       (the App's Client ID, like Iv23li…)
+    #   - HARPERFAST_AI_APP_PRIVATE_KEY (.pem file contents)
+    runs-on: ubuntu-latest
+    timeout-minutes: 1
+    permissions:
+      # `contents: read` so we can fetch this repo's .github/CODEOWNERS
+      # via the default token. Team-membership reads use the App token
+      # below, which is contained to this job.
+      contents: read
+    outputs:
+      authorized: ${{ steps.check.outputs.authorized }}
+    steps:
+      - name: Mint org-read token
+        id: app-token
+        uses: actions/create-github-app-token@1b10c78c7865c340bc4f6099eb2f838309f1e8c3 # v3.1.1
+        with:
+          client-id: ${{ secrets.HARPERFAST_AI_CLIENT_ID }}
+          private-key: ${{ secrets.HARPERFAST_AI_APP_PRIVATE_KEY }}
+          owner: HarperFast
+
+      - name: Checkout (for CODEOWNERS read)
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+        with:
+          sparse-checkout: |
+            .github/CODEOWNERS
+            .github/scripts/authorize-claude-workflow.sh
+          sparse-checkout-cone-mode: false
+
+      - name: Check authorization (PR author + event actor)
+        id: check
+        env:
+          DEFAULT_TOKEN: ${{ github.token }}
+          ORG_TOKEN: ${{ steps.app-token.outputs.token }}
+          ADMIT_CLAUDE_BOT: 'true'
+          USERS_TO_CHECK: |
+            ${{ github.event.pull_request.user.login }}
+            ${{ github.actor }}
+        run: bash .github/scripts/authorize-claude-workflow.sh
+
   review:
-    # Review PRs authored by HarperFast org members / collaborators. External
-    # PRs are not auto-reviewed — a maintainer can opt one in via an
-    # `@claude` mention (handled by a separate workflow). Also admits
-    # claude[bot] so AI-authored PRs (from issue-to-pr) get reviewed.
-    if: >-
-      contains(fromJSON('["OWNER", "MEMBER", "COLLABORATOR"]'),
-      github.event.pull_request.author_association)
-      || github.event.pull_request.user.login == 'claude[bot]'
+    needs: authorize
+    if: needs.authorize.outputs.authorized == 'true'
     runs-on: ubuntu-latest
     # 15 gives headroom for substantial diffs without letting a runaway loop
     # burn forever (claude-code-action's --max-turns is the real cost ceiling).