diff --git a/.github/workflows/require_issue_link.yml b/.github/workflows/require_issue_link.yml
new file mode 100644
index 000000000..6ee800f24
--- /dev/null
+++ b/.github/workflows/require_issue_link.yml
@@ -0,0 +1,413 @@
+# Require external PRs to reference an approved issue (e.g. Fixes #NNN) and
+# the PR author to be assigned to that issue. On failure the PR is
+# labeled "missing-issue-link", commented on, and closed.
+#
+# Maintainer override: an org member can reopen the PR or remove
+# "missing-issue-link" — both add "bypass-issue-check" and reopen.
+#
+# Dependency: tag-external-contributions.yml must apply the "external" label
+# first. This workflow does NOT trigger on "opened" (new PRs have no labels
+# yet, so the gate would always skip).
+
+name: Require Issue Link
+
+on:
+  pull_request_target:
+    types: [edited, reopened, labeled, unlabeled]
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Enforcement gate: set to 'true' to activate the issue link requirement.
+# When 'false', the workflow still runs the check logic (useful for dry-run
+# visibility) but will NOT label, comment, close, or fail PRs.
+# ──────────────────────────────────────────────────────────────────────────────
+env:
+  ENFORCE_ISSUE_LINK: "true"
+
+permissions:
+  contents: read
+
+jobs:
+  check-issue-link:
+    # Run when the "external" label is added, on edit/reopen if already labeled,
+    # or when "missing-issue-link" is removed (triggers maintainer override check).
+    # Skip entirely when the PR already carries "trusted-contributor" or
+    # "bypass-issue-check".
+    if: >-
+      !contains(github.event.pull_request.labels.*.name, 'trusted-contributor') &&
+      !contains(github.event.pull_request.labels.*.name, 'bypass-issue-check') &&
+      (
+        (github.event.action == 'labeled' && github.event.label.name == 'external') ||
+        (github.event.action == 'unlabeled' && github.event.label.name == 'missing-issue-link' && contains(github.event.pull_request.labels.*.name, 'external')) ||
+        (github.event.action != 'labeled' && github.event.action != 'unlabeled' && contains(github.event.pull_request.labels.*.name, 'external'))
+      )
+    runs-on: ubuntu-latest
+    permissions:
+      actions: write
+      pull-requests: write
+
+    steps:
+      - name: Check for issue link and assignee
+        id: check-link
+        uses: actions/github-script@v8
+        with:
+          script: |
+            const { owner, repo } = context.repo;
+            const prNumber = context.payload.pull_request.number;
+            const action = context.payload.action;
+
+            // ── Helper: ensure a label exists, then add it to the PR ────────
+            async function ensureAndAddLabel(labelName, color) {
+              try {
+                await github.rest.issues.getLabel({ owner, repo, name: labelName });
+              } catch (e) {
+                if (e.status !== 404) throw e;
+                try {
+                  await github.rest.issues.createLabel({ owner, repo, name: labelName, color });
+                } catch (createErr) {
+                  // 422 = label was created by a concurrent run between our
+                  // GET and POST — safe to ignore.
+                  if (createErr.status !== 422) throw createErr;
+                }
+              }
+              await github.rest.issues.addLabels({
+                owner, repo, issue_number: prNumber, labels: [labelName],
+              });
+            }
+
+            // ── Helper: check if sender is an active org member ─────────────
+            async function senderIsOrgMember() {
+              const sender = context.payload.sender?.login;
+              if (!sender) {
+                throw new Error('Event has no sender — cannot check org membership');
+              }
+              try {
+                const { data: membership } = await github.rest.orgs.getMembershipForUser({
+                  org: owner,
+                  username: sender,
+                });
+                if (membership.state === 'active') {
+                  return { isMember: true, login: sender };
+                }
+                console.log(`${sender} is an org member but state is "${membership.state}"`);
+                return { isMember: false, login: sender };
+              } catch (e) {
+                if (e.status === 404) {
+                  console.log(`${sender} is not an org member`);
+                  return { isMember: false, login: sender };
+                }
+                const status = e.status ?? 'unknown';
+                throw new Error(
+                  `Membership check failed for ${sender} (HTTP ${status}): ${e.message}`,
+                );
+              }
+            }
+
+            // ── Helper: apply maintainer bypass (shared by both override paths) ──
+            async function applyMaintainerBypass(reason) {
+              console.log(reason);
+
+              // Remove missing-issue-link if present
+              try {
+                await github.rest.issues.removeLabel({
+                  owner, repo, issue_number: prNumber, name: 'missing-issue-link',
+                });
+              } catch (e) {
+                if (e.status !== 404) throw e;
+              }
+
+              // Reopen before adding bypass label — a failed reopen is more
+              // actionable than a closed PR with a bypass label stuck on it.
+              if (context.payload.pull_request.state === 'closed') {
+                try {
+                  await github.rest.pulls.update({
+                    owner, repo, pull_number: prNumber, state: 'open',
+                  });
+                  console.log(`Reopened PR #${prNumber}`);
+                } catch (e) {
+                  // 422 if head branch deleted; 403 if permissions insufficient.
+                  // Bypass labels still apply — maintainer can reopen manually.
+                  core.warning(
+                    `Could not reopen PR #${prNumber} (HTTP ${e.status ?? 'unknown'}): ${e.message}. ` +
+                    `Bypass labels were applied — a maintainer may need to reopen manually.`,
+                  );
+                }
+              }
+
+              // Add bypass-issue-check so future triggers skip enforcement
+              await ensureAndAddLabel('bypass-issue-check', '0e8a16');
+
+              core.setOutput('has-link', 'true');
+              core.setOutput('is-assigned', 'true');
+            }
+
+            // ── Maintainer override: removed "missing-issue-link" label ─────
+            if (action === 'unlabeled') {
+              const { isMember, login } = await senderIsOrgMember();
+              if (isMember) {
+                await applyMaintainerBypass(
+                  `Maintainer ${login} removed missing-issue-link from PR #${prNumber} — bypassing enforcement`,
+                );
+                return;
+              }
+              // Non-member removed the label — re-add it defensively and
+              // set failure outputs so downstream steps (comment, close) fire.
+              // NOTE: addLabels fires a "labeled" event, but the job-level gate
+              // only matches labeled events for "external", so no re-trigger.
+              console.log(`Non-member ${login} removed missing-issue-link — re-adding`);
+              try {
+                await ensureAndAddLabel('missing-issue-link', 'b76e79');
+              } catch (e) {
+                core.warning(
+                  `Failed to re-add missing-issue-link (HTTP ${e.status ?? 'unknown'}): ${e.message}. ` +
+                  `Downstream step will retry.`,
+                );
+              }
+              core.setOutput('has-link', 'false');
+              core.setOutput('is-assigned', 'false');
+              return;
+            }
+
+            // ── Maintainer override: reopened PR with "missing-issue-link" ──
+            const prLabels = context.payload.pull_request.labels.map(l => l.name);
+            if (action === 'reopened' && prLabels.includes('missing-issue-link')) {
+              const { isMember, login } = await senderIsOrgMember();
+              if (isMember) {
+                await applyMaintainerBypass(
+                  `Maintainer ${login} reopened PR #${prNumber} — bypassing enforcement`,
+                );
+                return;
+              }
+              console.log(`Non-member ${login} reopened PR — proceeding with check`);
+            }
+
+            // ── Fetch live labels (race guard) ──────────────────────────────
+            const { data: liveLabels } = await github.rest.issues.listLabelsOnIssue({
+              owner, repo, issue_number: prNumber,
+            });
+            const liveNames = liveLabels.map(l => l.name);
+            if (liveNames.includes('trusted-contributor') || liveNames.includes('bypass-issue-check')) {
+              console.log('PR has trusted-contributor or bypass-issue-check label — bypassing');
+              core.setOutput('has-link', 'true');
+              core.setOutput('is-assigned', 'true');
+              return;
+            }
+
+            const body = context.payload.pull_request.body || '';
+            const pattern = /(?:close[sd]?|fix(?:e[sd])?|resolve[sd]?)\s*#(\d+)/gi;
+            const matches = [...body.matchAll(pattern)];
+
+            if (matches.length === 0) {
+              console.log('No issue link found in PR body');
+              core.setOutput('has-link', 'false');
+              core.setOutput('is-assigned', 'false');
+              return;
+            }
+
+            const issues = matches.map(m => `#${m[1]}`).join(', ');
+            console.log(`Found issue link(s): ${issues}`);
+            core.setOutput('has-link', 'true');
+
+            // Check whether the PR author is assigned to at least one linked issue
+            const prAuthor = context.payload.pull_request.user.login;
+            const MAX_ISSUES = 5;
+            const allIssueNumbers = [...new Set(matches.map(m => parseInt(m[1], 10)))];
+            const issueNumbers = allIssueNumbers.slice(0, MAX_ISSUES);
+            if (allIssueNumbers.length > MAX_ISSUES) {
+              core.warning(
+                `PR references ${allIssueNumbers.length} issues — only checking the first ${MAX_ISSUES}`,
+              );
+            }
+
+            let assignedToAny = false;
+            for (const num of issueNumbers) {
+              try {
+                const { data: issue } = await github.rest.issues.get({
+                  owner, repo, issue_number: num,
+                });
+                const assignees = issue.assignees.map(a => a.login.toLowerCase());
+                if (assignees.includes(prAuthor.toLowerCase())) {
+                  console.log(`PR author "${prAuthor}" is assigned to #${num}`);
+                  assignedToAny = true;
+                  break;
+                } else {
+                  console.log(`PR author "${prAuthor}" is NOT assigned to #${num} (assignees: ${assignees.join(', ') || 'none'})`);
+                }
+              } catch (error) {
+                if (error.status === 404) {
+                  console.log(`Issue #${num} not found — skipping`);
+                } else {
+                  // Non-404 errors (rate limit, server error) must not be
+                  // silently skipped — they could cause false enforcement
+                  // (closing a legitimate PR whose assignment can't be verified).
+                  throw new Error(
+                    `Cannot verify assignee for issue #${num} (${error.status}): ${error.message}`,
+                  );
+                }
+              }
+            }
+
+            core.setOutput('is-assigned', assignedToAny ? 'true' : 'false');
+
+      - name: Add missing-issue-link label
+        if: >-
+          env.ENFORCE_ISSUE_LINK == 'true' &&
+          (steps.check-link.outputs.has-link != 'true' || steps.check-link.outputs.is-assigned != 'true')
+        uses: actions/github-script@v8
+        with:
+          script: |
+            const { owner, repo } = context.repo;
+            const prNumber = context.payload.pull_request.number;
+            const labelName = 'missing-issue-link';
+
+            // Ensure the label exists (no checkout/shared helper available)
+            try {
+              await github.rest.issues.getLabel({ owner, repo, name: labelName });
+            } catch (e) {
+              if (e.status !== 404) throw e;
+              try {
+                await github.rest.issues.createLabel({
+                  owner, repo, name: labelName, color: 'b76e79',
+                });
+              } catch (createErr) {
+                if (createErr.status !== 422) throw createErr;
+              }
+            }
+
+            await github.rest.issues.addLabels({
+              owner, repo, issue_number: prNumber, labels: [labelName],
+            });
+
+      - name: Remove missing-issue-link label and reopen PR
+        if: >-
+          env.ENFORCE_ISSUE_LINK == 'true' &&
+          steps.check-link.outputs.has-link == 'true' && steps.check-link.outputs.is-assigned == 'true'
+        uses: actions/github-script@v8
+        with:
+          script: |
+            const { owner, repo } = context.repo;
+            const prNumber = context.payload.pull_request.number;
+            try {
+              await github.rest.issues.removeLabel({
+                owner, repo, issue_number: prNumber, name: 'missing-issue-link',
+              });
+            } catch (error) {
+              if (error.status !== 404) throw error;
+            }
+
+            // Reopen if this workflow previously closed the PR. We check the
+            // event payload labels (not live labels) because we already removed
+            // missing-issue-link above; the payload still reflects pre-step state.
+            const labels = context.payload.pull_request.labels.map(l => l.name);
+            if (context.payload.pull_request.state === 'closed' && labels.includes('missing-issue-link')) {
+              await github.rest.pulls.update({
+                owner,
+                repo,
+                pull_number: prNumber,
+                state: 'open',
+              });
+              console.log(`Reopened PR #${prNumber}`);
+            }
+
+      - name: Post comment, close PR, and fail
+        if: >-
+          env.ENFORCE_ISSUE_LINK == 'true' &&
+          (steps.check-link.outputs.has-link != 'true' || steps.check-link.outputs.is-assigned != 'true')
+        uses: actions/github-script@v8
+        with:
+          script: |
+            const { owner, repo } = context.repo;
+            const prNumber = context.payload.pull_request.number;
+            const hasLink = '${{ steps.check-link.outputs.has-link }}' === 'true';
+            const isAssigned = '${{ steps.check-link.outputs.is-assigned }}' === 'true';
+            const marker = '<!-- require-issue-link -->';
+
+            let lines;
+            if (!hasLink) {
+              lines = [
+                marker,
+                '**This PR has been automatically closed** because it does not link to an approved issue.',
+                '',
+                'All external contributions must reference an approved issue or discussion. Please:',
+                '1. Find or [open an issue](https://github.com/' + owner + '/' + repo + '/issues/new/choose) describing the change',
+                '2. Wait for a maintainer to approve and assign you',
+                '3. Add `Fixes #<issue_number>`, `Closes #<issue_number>`, or `Resolves #<issue_number>` to your PR description and the PR will be reopened automatically',
+                '',
+                '*Maintainers: reopen this PR or remove the `missing-issue-link` label to bypass this check.*',
+              ];
+            } else {
+              lines = [
+                marker,
+                '**This PR has been automatically closed** because you are not assigned to the linked issue.',
+                '',
+                'External contributors must be assigned to an issue before opening a PR for it. Please:',
+                '1. Comment on the linked issue to request assignment from a maintainer',
+                '2. Once assigned, edit your PR description and the PR will be reopened automatically',
+                '',
+                '*Maintainers: reopen this PR or remove the `missing-issue-link` label to bypass this check.*',
+              ];
+            }
+
+            const body = lines.join('\n');
+
+            // Deduplicate: check for existing comment with the marker
+            const comments = await github.paginate(
+              github.rest.issues.listComments,
+              { owner, repo, issue_number: prNumber, per_page: 100 },
+            );
+            const existing = comments.find(c => c.body && c.body.includes(marker));
+
+            if (!existing) {
+              await github.rest.issues.createComment({
+                owner,
+                repo,
+                issue_number: prNumber,
+                body,
+              });
+              console.log('Posted requirement comment');
+            } else if (existing.body !== body) {
+              await github.rest.issues.updateComment({
+                owner,
+                repo,
+                comment_id: existing.id,
+                body,
+              });
+              console.log('Updated existing comment with new message');
+            } else {
+              console.log('Comment already exists — skipping');
+            }
+
+            // Close the PR
+            if (context.payload.pull_request.state === 'open') {
+              await github.rest.pulls.update({
+                owner,
+                repo,
+                pull_number: prNumber,
+                state: 'closed',
+              });
+              console.log(`Closed PR #${prNumber}`);
+            }
+
+            // Cancel all other in-progress and queued workflow runs for this PR
+            const headSha = context.payload.pull_request.head.sha;
+            for (const status of ['in_progress', 'queued']) {
+              const runs = await github.paginate(
+                github.rest.actions.listWorkflowRunsForRepo,
+                { owner, repo, head_sha: headSha, status, per_page: 100 },
+              );
+              for (const run of runs) {
+                if (run.id === context.runId) continue;
+                try {
+                  await github.rest.actions.cancelWorkflowRun({
+                    owner, repo, run_id: run.id,
+                  });
+                  console.log(`Cancelled ${status} run ${run.id} (${run.name})`);
+                } catch (err) {
+                  console.log(`Could not cancel run ${run.id}: ${err.message}`);
+                }
+              }
+            }
+
+            const reason = !hasLink
+              ? 'PR must reference an issue using auto-close keywords (e.g., "Fixes #123").'
+              : 'PR author must be assigned to the linked issue.';
+            core.setFailed(reason);
diff --git a/.github/workflows/tag-external-contributions.yml b/.github/workflows/tag-external-contributions.yml
new file mode 100644
index 000000000..00ae30d8f
--- /dev/null
+++ b/.github/workflows/tag-external-contributions.yml
@@ -0,0 +1,442 @@
+# Automatically tag issues and pull requests as "external" or "internal"
+# based on whether the author is a member of the langchain-ai GitHub
+# organization, and apply contributor tier labels to external contributors
+# based on their merged PR history.
+#
+# NOTE: This repo does not have a separate pr_labeler.yml — this workflow
+# handles both issues and PRs.
+#
+# Setup Requirements:
+# 1. Create a GitHub App with permissions:
+#    - Repository: Issues (write), Pull requests (write)
+#    - Organization: Members (read)
+# 2. Install the app on your organization and this repository
+# 3. Add these repository secrets:
+#    - ORG_MEMBERSHIP_APP_ID: Your app's ID
+#    - ORG_MEMBERSHIP_APP_PRIVATE_KEY: Your app's private key
+#
+# The GitHub App token is required to check private organization membership.
+# Without it, the workflow will fail.
+
+name: Tag External Contributions
+
+on:
+  issues:
+    types: [opened]
+  pull_request_target:
+    types: [opened]
+  workflow_dispatch:
+    inputs:
+      backfill_type:
+        description: "Backfill type (for initial run)"
+        default: "both"
+        type: choice
+        options:
+          - prs
+          - issues
+          - both
+      max_items:
+        description: "Maximum number of items to process"
+        default: "100"
+        type: string
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.issue.number || github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  tag-external:
+    if: github.event_name != 'workflow_dispatch'
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+
+    steps:
+      - name: Generate GitHub App token
+        id: app-token
+        uses: actions/create-github-app-token@v3
+        with:
+          app-id: ${{ secrets.ORG_MEMBERSHIP_APP_ID }}
+          private-key: ${{ secrets.ORG_MEMBERSHIP_APP_PRIVATE_KEY }}
+
+      - name: Check if contributor is external
+        if: steps.app-token.outcome == 'success'
+        id: check-membership
+        uses: actions/github-script@v8
+        with:
+          github-token: ${{ steps.app-token.outputs.token }}
+          script: |
+            const { owner, repo } = context.repo;
+            const author = context.payload.sender.login;
+            const senderType = context.payload.sender.type;
+
+            if (senderType === 'Bot') {
+              console.log(`${author} is a Bot — treating as internal`);
+              core.setOutput('is-external', 'false');
+              return;
+            }
+
+            try {
+              const membership = await github.rest.orgs.getMembershipForUser({
+                org: 'langchain-ai',
+                username: author,
+              });
+              const isExternal = membership.data.state !== 'active';
+              console.log(
+                isExternal
+                  ? `${author} has pending membership — treating as external`
+                  : `${author} is an active member of langchain-ai`,
+              );
+              core.setOutput('is-external', isExternal ? 'true' : 'false');
+            } catch (e) {
+              if (e.status === 404) {
+                console.log(`${author} is not a member of langchain-ai`);
+                core.setOutput('is-external', 'true');
+              } else {
+                throw new Error(
+                  `Membership check failed for ${author} (${e.status}): ${e.message}`,
+                );
+              }
+            }
+
+      # Apply tier label BEFORE the external/internal labels so that
+      # "trusted-contributor" is already present when the "external" labeled
+      # event fires and triggers require_issue_link.yml.
+      - name: Apply contributor tier label
+        if: steps.check-membership.outputs.is-external == 'true'
+        uses: actions/github-script@v8
+        with:
+          # Use App token so the "labeled" event propagates to downstream
+          # workflows (e.g. require_issue_link.yml).
+          github-token: ${{ steps.app-token.outputs.token }}
+          script: |
+            const { owner, repo } = context.repo;
+            const isPR = context.eventName === 'pull_request_target';
+            const item = isPR
+              ? context.payload.pull_request
+              : context.payload.issue;
+            const author = item.user.login;
+            const issueNumber = item.number;
+
+            const TRUSTED_THRESHOLD = 5;
+            const LABEL_COLOR = 'b76e79';
+
+            let mergedCount;
+            try {
+              const result = await github.rest.search.issuesAndPullRequests({
+                q: `repo:${owner}/${repo} is:pr is:merged author:"${author}"`,
+                per_page: 1,
+              });
+              mergedCount = result?.data?.total_count;
+            } catch (error) {
+              if (error?.status !== 422) throw error;
+              core.warning(`Search failed for ${author}; skipping tier label.`);
+              return;
+            }
+
+            if (mergedCount == null) {
+              core.warning(`Search response missing total_count for ${author}; skipping tier label.`);
+              return;
+            }
+
+            const tierLabel = mergedCount >= TRUSTED_THRESHOLD ? 'trusted-contributor' : null;
+
+            if (tierLabel) {
+              try {
+                await github.rest.issues.getLabel({ owner, repo, name: tierLabel });
+              } catch (e) {
+                if (e.status !== 404) throw e;
+                try {
+                  await github.rest.issues.createLabel({ owner, repo, name: tierLabel, color: LABEL_COLOR });
+                } catch (createErr) {
+                  if (createErr.status !== 422) throw createErr;
+                }
+              }
+              await github.rest.issues.addLabels({
+                owner, repo, issue_number: issueNumber, labels: [tierLabel],
+              });
+              console.log(`Applied '${tierLabel}' to #${issueNumber} (${mergedCount} merged PRs)`);
+            } else {
+              console.log(`No tier label for ${author} (${mergedCount} merged PRs)`);
+            }
+
+      - name: Add external label to issue
+        if: steps.check-membership.outputs.is-external == 'true' && github.event_name == 'issues'
+        uses: actions/github-script@v8
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const { owner, repo } = context.repo;
+            const issue_number = context.payload.issue.number;
+            await github.rest.issues.addLabels({
+              owner, repo, issue_number, labels: ['external'],
+            });
+            console.log(`Added 'external' label to issue #${issue_number}`);
+
+      - name: Add external label to pull request
+        if: steps.check-membership.outputs.is-external == 'true' && github.event_name == 'pull_request_target'
+        uses: actions/github-script@v8
+        with:
+          # Use App token so the "labeled" event propagates to downstream
+          # workflows (e.g. require_issue_link.yml). Events created by the
+          # default GITHUB_TOKEN do not trigger additional workflow runs.
+          github-token: ${{ steps.app-token.outputs.token }}
+          script: |
+            const { owner, repo } = context.repo;
+            const issue_number = context.payload.pull_request.number;
+            await github.rest.issues.addLabels({
+              owner, repo, issue_number, labels: ['external'],
+            });
+            console.log(`Added 'external' label to PR #${issue_number}`);
+
+      - name: Add internal label to issue
+        if: steps.check-membership.outputs.is-external == 'false' && github.event_name == 'issues'
+        uses: actions/github-script@v8
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const { owner, repo } = context.repo;
+            const issue_number = context.payload.issue.number;
+            await github.rest.issues.addLabels({
+              owner, repo, issue_number, labels: ['internal'],
+            });
+            console.log(`Added 'internal' label to issue #${issue_number}`);
+
+      - name: Add internal label to pull request
+        if: steps.check-membership.outputs.is-external == 'false' && github.event_name == 'pull_request_target'
+        uses: actions/github-script@v8
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const { owner, repo } = context.repo;
+            const issue_number = context.payload.pull_request.number;
+            await github.rest.issues.addLabels({
+              owner, repo, issue_number, labels: ['internal'],
+            });
+            console.log(`Added 'internal' label to PR #${issue_number}`);
+
+  backfill:
+    if: github.event_name == 'workflow_dispatch'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      issues: write
+      pull-requests: write
+
+    steps:
+      - name: Generate GitHub App token
+        id: app-token
+        uses: actions/create-github-app-token@v3
+        with:
+          app-id: ${{ secrets.ORG_MEMBERSHIP_APP_ID }}
+          private-key: ${{ secrets.ORG_MEMBERSHIP_APP_PRIVATE_KEY }}
+
+      - name: Backfill labels
+        uses: actions/github-script@v8
+        with:
+          github-token: ${{ steps.app-token.outputs.token }}
+          script: |
+            const { owner, repo } = context.repo;
+            const rawMax = '${{ inputs.max_items }}';
+            const maxItems = parseInt(rawMax, 10);
+            if (isNaN(maxItems) || maxItems <= 0) {
+              core.setFailed(`Invalid max_items: "${rawMax}" — must be a positive integer`);
+              return;
+            }
+            const backfillType = '${{ inputs.backfill_type }}';
+
+            const TRUSTED_THRESHOLD = 5;
+            const LABEL_COLOR = 'b76e79';
+
+            const tierLabels = ['trusted-contributor'];
+
+            // ── Helpers (inlined from pr-labeler.js) ─────────────────────────
+
+            async function ensureLabel(name) {
+              try {
+                await github.rest.issues.getLabel({ owner, repo, name });
+              } catch (e) {
+                if (e.status !== 404) throw e;
+                try {
+                  await github.rest.issues.createLabel({ owner, repo, name, color: LABEL_COLOR });
+                } catch (createErr) {
+                  if (createErr.status !== 422) throw createErr;
+                }
+              }
+            }
+
+            async function checkMembership(author, userType) {
+              if (userType === 'Bot') {
+                console.log(`${author} is a Bot — treating as internal`);
+                return { isExternal: false };
+              }
+              try {
+                const membership = await github.rest.orgs.getMembershipForUser({
+                  org: 'langchain-ai',
+                  username: author,
+                });
+                const isExternal = membership.data.state !== 'active';
+                console.log(
+                  isExternal
+                    ? `${author} has pending membership — treating as external`
+                    : `${author} is an active member of langchain-ai`,
+                );
+                return { isExternal };
+              } catch (e) {
+                if (e.status === 404) {
+                  console.log(`${author} is not a member of langchain-ai`);
+                  return { isExternal: true };
+                }
+                throw new Error(
+                  `Membership check failed for ${author} (${e.status}): ${e.message}`,
+                );
+              }
+            }
+
+            async function getContributorInfo(contributorCache, author, userType) {
+              if (contributorCache.has(author)) return contributorCache.get(author);
+
+              const { isExternal } = await checkMembership(author, userType);
+
+              let mergedCount = null;
+              if (isExternal) {
+                try {
+                  const result = await github.rest.search.issuesAndPullRequests({
+                    q: `repo:${owner}/${repo} is:pr is:merged author:"${author}"`,
+                    per_page: 1,
+                  });
+                  mergedCount = result?.data?.total_count ?? null;
+                } catch (e) {
+                  if (e?.status !== 422) throw e;
+                  core.warning(`Search failed for ${author}; skipping tier.`);
+                }
+              }
+
+              const info = { isExternal, mergedCount };
+              contributorCache.set(author, info);
+              return info;
+            }
+
+            // ── Setup ────────────────────────────────────────────────────────
+
+            for (const name of tierLabels) {
+              await ensureLabel(name);
+            }
+
+            const contributorCache = new Map();
+
+            let processed = 0;
+            let failures = 0;
+
+            // ── Backfill PRs ─────────────────────────────────────────────────
+
+            if (backfillType === 'prs' || backfillType === 'both') {
+              const prs = await github.paginate(github.rest.pulls.list, {
+                owner, repo, state: 'open', per_page: 100,
+              });
+
+              for (const pr of prs) {
+                if (processed >= maxItems) break;
+
+                try {
+                  const author = pr.user.login;
+                  const info = await getContributorInfo(contributorCache, author, pr.user.type);
+
+                  const labels = [info.isExternal ? 'external' : 'internal'];
+                  if (info.isExternal && info.mergedCount != null && info.mergedCount >= TRUSTED_THRESHOLD) {
+                    labels.push('trusted-contributor');
+                  }
+
+                  // Ensure all labels exist before batch add
+                  for (const name of labels) {
+                    await ensureLabel(name);
+                  }
+
+                  // Remove stale tier labels
+                  const currentLabels = (await github.paginate(
+                    github.rest.issues.listLabelsOnIssue,
+                    { owner, repo, issue_number: pr.number, per_page: 100 },
+                  )).map(l => l.name ?? '');
+                  for (const name of currentLabels) {
+                    if (tierLabels.includes(name) && !labels.includes(name)) {
+                      try {
+                        await github.rest.issues.removeLabel({
+                          owner, repo, issue_number: pr.number, name,
+                        });
+                      } catch (e) {
+                        if (e.status !== 404) throw e;
+                      }
+                    }
+                  }
+
+                  await github.rest.issues.addLabels({
+                    owner, repo, issue_number: pr.number, labels,
+                  });
+                  console.log(`PR #${pr.number} (${author}): ${labels.join(', ')}`);
+                  processed++;
+                } catch (e) {
+                  failures++;
+                  core.warning(`Failed to process PR #${pr.number}: ${e.message}`);
+                }
+              }
+            }
+
+            // ── Backfill issues ──────────────────────────────────────────────
+
+            if (backfillType === 'issues' || backfillType === 'both') {
+              const issues = await github.paginate(github.rest.issues.listForRepo, {
+                owner, repo, state: 'open', per_page: 100,
+              });
+
+              for (const issue of issues) {
+                if (processed >= maxItems) break;
+                if (issue.pull_request) continue;
+
+                try {
+                  const author = issue.user.login;
+                  const info = await getContributorInfo(contributorCache, author, issue.user.type);
+
+                  const labels = [info.isExternal ? 'external' : 'internal'];
+                  if (info.isExternal && info.mergedCount != null && info.mergedCount >= TRUSTED_THRESHOLD) {
+                    labels.push('trusted-contributor');
+                  }
+
+                  // Ensure all labels exist before batch add
+                  for (const name of labels) {
+                    await ensureLabel(name);
+                  }
+
+                  // Remove stale tier labels
+                  const currentLabels = (await github.paginate(
+                    github.rest.issues.listLabelsOnIssue,
+                    { owner, repo, issue_number: issue.number, per_page: 100 },
+                  )).map(l => l.name ?? '');
+                  for (const name of currentLabels) {
+                    if (tierLabels.includes(name) && !labels.includes(name)) {
+                      try {
+                        await github.rest.issues.removeLabel({
+                          owner, repo, issue_number: issue.number, name,
+                        });
+                      } catch (e) {
+                        if (e.status !== 404) throw e;
+                      }
+                    }
+                  }
+
+                  await github.rest.issues.addLabels({
+                    owner, repo, issue_number: issue.number, labels,
+                  });
+                  console.log(`Issue #${issue.number} (${author}): ${labels.join(', ')}`);
+                  processed++;
+                } catch (e) {
+                  failures++;
+                  core.warning(`Failed to process issue #${issue.number}: ${e.message}`);
+                }
+              }
+            }
+
+            console.log(`\nBackfill complete. Processed ${processed} items, ${failures} failures. ${contributorCache.size} unique authors.`);