diff --git a/packages/core/src/__tests__/postgres/sqlite-production-reader-inventory.test.ts b/packages/core/src/__tests__/postgres/sqlite-production-reader-inventory.test.ts
new file mode 100644
index 0000000000..59598d89e3
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+++ b/packages/core/src/__tests__/postgres/sqlite-production-reader-inventory.test.ts
@@ -0,0 +1,173 @@
+/*
+FNXC:SqliteInventoryRatchet 2026-07-26-19:45:
+PostgreSQL is the only supported runtime metadata authority. Production code may
+open legacy SQLite only at the six cutover-approved read-only migration seams
+documented in docs/postgres-migration-review-2026-07-14.md. This structural
+ratchet scans the real source tree for `new DatabaseSync(` outside tests and
+fails when a new production constructor appears. A second suite drives the real
+archive-guard helpers to prove the known incomplete-PG-port behavior (backend
+mode returns false rather than consulting a removed SQLite archive handle).
+*/
+import { describe, expect, it } from "vitest";
+import { readFileSync, readdirSync } from "node:fs";
+import { join, relative } from "node:path";
+import {
+  isTaskArchivedImpl,
+  isTaskIdPresentInArchivedTasksTableImpl,
+} from "../../task-store/task-id-integrity.js";
+import type { TaskStore } from "../../store.js";
+
+const workspaceRoot = join(__dirname, "..", "..", "..", "..", "..");
+
+/**
+ * Production (non-test) call sites allowed to construct DatabaseSync.
+ * Paths are repo-relative. Keep in sync with docs/postgres-migration-review-2026-07-14.md
+ * "Intentional remaining SQLite readers" and the SQLite migration inventory.
+ */
+export const AUTHORIZED_PRODUCTION_DATABASE_SYNC_CONSTRUCTORS = [
+  "packages/core/src/postgres/sqlite-migrator.ts",
+  "packages/core/src/project-identity.ts",
+  "packages/core/src/sqlite-validation.ts",
+  "packages/core/src/postgres/startup-factory.ts",
+  "packages/cli/src/commands/db.ts",
+  "scripts/lib/start-local-project.mjs",
+] as const;
+
+const SCAN_ROOTS = [
+  "packages/core/src",
+  "packages/cli/src",
+  "packages/dashboard/src",
+  "packages/dashboard/app",
+  "packages/engine/src",
+  "packages/desktop/src",
+  "plugins",
+  "scripts",
+] as const;
+
+const NEW_DATABASE_SYNC = /new\s+DatabaseSync\s*\(/g;
+
+function isTestOrNonSourcePath(relPath: string): boolean {
+  const normalized = relPath.replace(/\\/g, "/");
+  if (normalized.includes("/__tests__/") || normalized.includes("/__mocks__/")) return true;
+  if (/\.(test|spec)\.(ts|tsx|js|mjs|cjs)$/.test(normalized)) return true;
+  if (normalized.includes("/node_modules/") || normalized.includes("/dist/")) return true;
+  // Vitest configs and package scripts that only quarantine SQLite tests are not openers.
+  if (/vitest\.config\.(ts|js|mjs)$/.test(normalized)) return true;
+  return false;
+}
+
+function listSourceFiles(dir: string): string[] {
+  let entries;
+  try {
+    entries = readdirSync(dir, { withFileTypes: true });
+  } catch (error) {
+    const code = error && typeof error === "object" && "code" in error ? (error as NodeJS.ErrnoException).code : undefined;
+    if (code === "ENOENT") return [];
+    throw error;
+  }
+  const files: string[] = [];
+  for (const entry of entries) {
+    const path = join(dir, entry.name);
+    if (entry.isDirectory()) {
+      if (
+        entry.name === "node_modules" ||
+        entry.name === "dist" ||
+        entry.name === "coverage" ||
+        entry.name.startsWith(".")
+      ) {
+        continue;
+      }
+      files.push(...listSourceFiles(path));
+      continue;
+    }
+    if (!/\.(ts|tsx|js|mjs|cjs)$/.test(entry.name)) continue;
+    files.push(path);
+  }
+  return files;
+}
+
+function collectProductionDatabaseSyncConstructors(): Array<{ file: string; line: number; text: string }> {
+  const hits: Array<{ file: string; line: number; text: string }> = [];
+  for (const root of SCAN_ROOTS) {
+    for (const abs of listSourceFiles(join(workspaceRoot, root))) {
+      const rel = relative(workspaceRoot, abs).replace(/\\/g, "/");
+      if (isTestOrNonSourcePath(rel)) continue;
+      const content = readFileSync(abs, "utf8");
+      // Strip block and line comments so docstrings mentioning the constructor do not count.
+      const codeOnly = content
+        .replace(/\/\*[\s\S]*?\*\//g, (block) => block.replace(/[^\n]/g, " "))
+        .replace(/(^|[^:])\/\/.*$/gm, "$1");
+      const lines = codeOnly.split("\n");
+      lines.forEach((line, index) => {
+        NEW_DATABASE_SYNC.lastIndex = 0;
+        if (NEW_DATABASE_SYNC.test(line)) {
+          hits.push({ file: rel, line: index + 1, text: line.trim() });
+        }
+      });
+    }
+  }
+  return hits;
+}
+
+describe("SQLite production reader inventory (cutover ratchet)", () => {
+  it("allows only the six authorized production new DatabaseSync call sites", () => {
+    const hits = collectProductionDatabaseSyncConstructors();
+    const files = [...new Set(hits.map((h) => h.file))].sort();
+    const authorized = [...AUTHORIZED_PRODUCTION_DATABASE_SYNC_CONSTRUCTORS].sort();
+
+    expect(files, `Unexpected production DatabaseSync constructors:\n${hits.map((h) => `${h.file}:${h.line}: ${h.text}`).join("\n")}`).toEqual(
+      authorized,
+    );
+
+    // Every authorized path must still exist and still construct (no silent delete of a seam).
+    for (const path of AUTHORIZED_PRODUCTION_DATABASE_SYNC_CONSTRUCTORS) {
+      expect(files).toContain(path);
+    }
+  });
+
+  it("constructs DatabaseSync only with readOnly: true on authorized production sites", () => {
+    const hits = collectProductionDatabaseSyncConstructors();
+    for (const hit of hits) {
+      // Read original source around the hit — require readOnly in the same statement region.
+      const abs = join(workspaceRoot, hit.file);
+      const content = readFileSync(abs, "utf8");
+      const lines = content.split("\n");
+      // Window: constructor line plus next 2 lines (options may wrap).
+      const window = lines.slice(Math.max(0, hit.line - 1), hit.line + 2).join(" ");
+      expect(
+        window,
+        `${hit.file}:${hit.line} must open DatabaseSync read-only`,
+      ).toMatch(/readOnly\s*:\s*true/);
+    }
+  });
+});
+
+describe("incomplete PG archive guards (shipped helpers)", () => {
+  function backendModeStore(): TaskStore {
+    // Minimal TaskStore shape: backendMode true must never touch store.db.
+    return {
+      backendMode: true,
+      asyncLayer: { projectId: "proj_test" },
+      db: {
+        prepare() {
+          throw new Error("SQLite Database must not be consulted in backend mode");
+        },
+      },
+      archiveDb: {
+        get() {
+          throw new Error("SQLite ArchiveDatabase must not be consulted in backend mode");
+        },
+      },
+    } as unknown as TaskStore;
+  }
+
+  it("isTaskIdPresentInArchivedTasksTableImpl returns false under backend mode without opening SQLite", () => {
+    const store = backendModeStore();
+    expect(isTaskIdPresentInArchivedTasksTableImpl(store, "FN-9999")).toBe(false);
+  });
+
+  it("isTaskArchivedImpl returns false under backend mode without opening SQLite", () => {
+    const store = backendModeStore();
+    expect(isTaskArchivedImpl(store, "FN-9999")).toBe(false);
+  });
+});