diff --git a/scripts/backfill.ts b/scripts/backfill.ts
index d7f92d3..1d7f6b7 100644
--- a/scripts/backfill.ts
+++ b/scripts/backfill.ts
@@ -69,14 +69,14 @@ async function main() {
     const result = await fetchCommitPage(project.repo_owner, project.repo_name, page);
     if (result.commits.length === 0) break;
 
-    const shas = result.commits.map((c) => `sha = "${c.sha}"`).join(" || ");
+    const shas = result.commits.map((c: { sha: string }) => `sha = "${c.sha}"`).join(" || ");
     const existing = await pb.collection("commits").getFullList({
       filter: `project = "${projectId}" && (${shas})`,
       fields: "sha",
     });
     const known = new Set(existing.map((r) => r.sha as string));
 
-    for (const commit of result.commits) {
+    for (const commit of result.commits as Array<{ sha: string; commit: { message: string; author: { name: string; email: string; date: string } }; parents?: Array<{ sha: string }>; stats?: { additions: number; deletions: number }; html_url: string }>) {
       if (known.has(commit.sha)) {
         skipped += 1;
         continue;
diff --git a/scripts/seed-demo.ts b/scripts/seed-demo.ts
index eeaf298..5625041 100644
--- a/scripts/seed-demo.ts
+++ b/scripts/seed-demo.ts
@@ -155,21 +155,6 @@ async function main() {
     );
     position += SPACING;
   }
-      `project = "${project.id}" && title = "${card.title}"`,
-      {
-        project: project.id,
-        column: columns[card.column],
-        title: card.title,
-        description: "",
-        position,
-        priority: card.priority,
-        created_by_role: "owner",
-        accepted: true,
-        archived: false,
-      }
-    );
-    position += SPACING;
-  }
 
   console.log("Seeded:");
   console.log(`  client   ${client.id} (${DEMO.clientSlug})`);
diff --git a/src/app/api/client/cards/route.ts b/src/app/api/client/cards/route.ts
index f04e64b..3f90877 100644
--- a/src/app/api/client/cards/route.ts
+++ b/src/app/api/client/cards/route.ts
@@ -6,6 +6,7 @@ import {
   canWriteClientFields,
 } from "@/lib/auth/access";
 import { pickClientCardCreate } from "@/lib/cards/client-patch";
+import { nextCardNumber } from "@/lib/cards/number";
 import { positionBetween } from "@/lib/ordering/fractional";
 import { jsonError, jsonOk } from "@/lib/http/json";
 import type { CardRecord, ColumnRecord, ProjectRecord } from "@/lib/pb/types";
diff --git a/src/lib/linking/engine.ts b/src/lib/linking/engine.ts
new file mode 100644
index 0000000..9fe2a6a
--- /dev/null
+++ b/src/lib/linking/engine.ts
@@ -0,0 +1,113 @@
+import "server-only";
+
+import { getAdminPb } from "@/lib/pb/admin";
+import { resolveCommitCard, type LinkCandidate } from "@/lib/linking/resolve";
+import type { CardRecord, CommitRecord } from "@/lib/pb/types";
+
+export interface RelinkResult {
+  examined: number;
+  linked: number;
+  unlinked: number;
+  preserved: number;
+}
+
+/**
+ * Recompute every derived link on a project.
+ *
+ * Idempotent and safe to run repeatedly: it reads the current state, decides
+ * again from the rules, and writes only where the answer changed.
+ *
+ * `manual` links are PRESERVED, never recomputed. A link the owner made by hand
+ * from the Unassigned tray is a human decision that outranks every rule in
+ * resolve.ts — overwriting it on the next push would make the tray pointless
+ * and would look, from the owner's side, like the app undoing their work.
+ */
+export async function relinkProject(projectId: string): Promise<RelinkResult> {
+  const pb = await getAdminPb();
+
+  const cards = await pb.collection("cards").getFullList<CardRecord>({
+    filter: `project = "${projectId}"`,
+    fields: "id,number,scope_rule,start_date,created,archived",
+  });
+
+  const candidates: LinkCandidate[] = cards.map((card) => ({
+    id: card.id,
+    number: card.number,
+    scopeRule: card.scope_rule ?? "",
+    startDate: card.start_date ?? "",
+    created: card.created,
+    archived: Boolean(card.archived),
+  }));
+
+  const commits = await pb.collection("commits").getFullList<CommitRecord>({
+    filter: `project = "${projectId}"`,
+    fields: "id,message,scope,authored_at,is_merge,card,link_source",
+  });
+
+  const result: RelinkResult = {
+    examined: 0,
+    linked: 0,
+    unlinked: 0,
+    preserved: 0,
+  };
+
+  for (const commit of commits) {
+    if (commit.link_source === "manual") {
+      result.preserved += 1;
+      continue;
+    }
+
+    result.examined += 1;
+
+    const resolution = resolveCommitCard(
+      {
+        message: commit.message ?? "",
+        scope: commit.scope ?? "",
+        authoredAt: commit.authored_at,
+        isMerge: Boolean(commit.is_merge),
+      },
+      candidates
+    );
+
+    const nextCard = resolution.cardId ?? "";
+    const nextSource = resolution.source;
+
+    // Write only on change. A no-op update would bump `updated` on every
+    // commit row on every push, which makes the collection useless for
+    // spotting what actually moved.
+    if (commit.card === nextCard && commit.link_source === nextSource) continue;
+
+    await pb.collection("commits").update(commit.id, {
+      card: nextCard,
+      link_source: nextSource,
+    });
+
+    if (nextCard) result.linked += 1;
+    else result.unlinked += 1;
+  }
+
+  return result;
+}
+
+/** Attach a commit to a card by hand. Outranks and survives re-linking. */
+export async function linkCommitManually(
+  commitId: string,
+  cardId: string
+): Promise<void> {
+  const pb = await getAdminPb();
+  await pb
+    .collection("commits")
+    .update(commitId, { card: cardId, link_source: "manual" });
+}
+
+/**
+ * Detach a commit.
+ *
+ * Reset to `none` rather than to `manual`, so the next re-link is free to
+ * reconsider it — "this is not right" should not also mean "never look at this
+ * again".
+ */
+export async function unlinkCommit(commitId: string): Promise<void> {
+  const pb = await getAdminPb();
+  await pb.collection("commits").update(commitId, { card: "", link_source: "none" });
+}
\ No newline at end of file