fix(KB-186): add ID-based tiebreaker to sort comparators for stable ordering

- Add numeric ID tiebreaker to TaskStore.listTasks() when createdAt timestamps match
- Add same tiebreaker to InlineCreateCard and TaskDetailModal dependency dropdown sorts
- Add store-sort integration test verifying ascending ID order with identical timestamps
- Add InlineCreateCard tests for identical-timestamp dropdown ordering and search filtering
- Add TaskDetailModal test for identical-timestamp dependency dropdown ordering

packages/core/src/__tests__/store-sort.test.ts

@@ -0,0 +1,55 @@
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+import { TaskStore } from "../store.js";
+import { rm } from "node:fs/promises";
+import { join } from "node:path";
+import { mkdtempSync } from "node:fs";
+import { tmpdir } from "node:os";
+
+function makeTmpDir(): string {
+  return mkdtempSync(join(tmpdir(), "kb-store-sort-test-"));
+}
+
+describe("TaskStore.listTasks() sort order", () => {
+  let rootDir: string;
+  let store: TaskStore;
+
+  beforeEach(async () => {
+    rootDir = makeTmpDir();
+    store = new TaskStore(rootDir);
+    await store.init();
+  });
+
+  afterEach(async () => {
+    store.stopWatching();
+    await rm(rootDir, { recursive: true, force: true });
+  });
+
+  it("returns tasks with identical createdAt in ascending ID order", async () => {
+    // Create three tasks — they may get the same createdAt if created fast enough
+    const t1 = await store.createTask({ description: "Task one" });
+    const t2 = await store.createTask({ description: "Task two" });
+    const t3 = await store.createTask({ description: "Task three" });
+
+    // Force identical createdAt by rewriting the task.json files
+    const { readFile, writeFile } = await import("node:fs/promises");
+    const tasksDir = join(rootDir, ".kb", "tasks");
+    const sameTimestamp = "2026-06-01T00:00:00Z";
+
+    for (const t of [t1, t2, t3]) {
+      const jsonPath = join(tasksDir, t.id, "task.json");
+      const data = JSON.parse(await readFile(jsonPath, "utf-8"));
+      data.createdAt = sameTimestamp;
+      data.updatedAt = sameTimestamp;
+      await writeFile(jsonPath, JSON.stringify(data, null, 2));
+    }
+
+    const tasks = await store.listTasks();
+    const ids = tasks.map((t) => t.id);
+
+    // Should be ascending by numeric ID portion
+    const nums = ids.map((id) => parseInt(id.slice(id.lastIndexOf("-") + 1), 10));
+    for (let i = 1; i < nums.length; i++) {
+      expect(nums[i]).toBeGreaterThan(nums[i - 1]);
+    }
+  });
+});

packages/core/src/store.ts

@@ -249,7 +249,13 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       }
     }
 
-    return tasks.sort((a, b) => a.createdAt.localeCompare(b.createdAt));
+    return tasks.sort((a, b) => {
+      const cmp = a.createdAt.localeCompare(b.createdAt);
+      if (cmp !== 0) return cmp;
+      const aNum = parseInt(a.id.slice(a.id.lastIndexOf("-") + 1), 10) || 0;
+      const bNum = parseInt(b.id.slice(b.id.lastIndexOf("-") + 1), 10) || 0;
+      return aNum - bNum;
+    });
   }
 
   async moveTask(id: string, toColumn: Column): Promise<Task> {

packages/dashboard/app/components/InlineCreateCard.tsx

@@ -204,7 +204,13 @@ export function InlineCreateCard({ tasks, onSubmit, onCancel, addToast }: Inline
                   (t.description && t.description.toLowerCase().includes(term))
                 )
               : [...tasks]
-            ).sort((a, b) => b.createdAt.localeCompare(a.createdAt));
+            ).sort((a, b) => {
+              const cmp = b.createdAt.localeCompare(a.createdAt);
+              if (cmp !== 0) return cmp;
+              const aNum = parseInt(a.id.slice(a.id.lastIndexOf("-") + 1), 10) || 0;
+              const bNum = parseInt(b.id.slice(b.id.lastIndexOf("-") + 1), 10) || 0;
+              return bNum - aNum;
+            });
             return (
               <div className="dep-dropdown" onMouseDown={(e) => e.preventDefault()}>
                 <input

packages/dashboard/app/components/TaskDetailModal.tsx

@@ -239,7 +239,13 @@ export function TaskDetailModal({
 
   const availableTasks = tasks
     .filter((t) => t.id !== task.id && !dependencies.includes(t.id))
-    .sort((a, b) => b.createdAt.localeCompare(a.createdAt));
+    .sort((a, b) => {
+      const cmp = b.createdAt.localeCompare(a.createdAt);
+      if (cmp !== 0) return cmp;
+      const aNum = parseInt(a.id.slice(a.id.lastIndexOf("-") + 1), 10) || 0;
+      const bNum = parseInt(b.id.slice(b.id.lastIndexOf("-") + 1), 10) || 0;
+      return bNum - aNum;
+    });
 
   const transitions = VALID_TRANSITIONS[task.column] || [];
 

packages/dashboard/app/components/__tests__/InlineCreateCard.test.tsx

@@ -133,6 +133,34 @@ describe("InlineCreateCard dependency dropdown sort order", () => {
   });
 });
 
+describe("InlineCreateCard dependency dropdown sort with identical timestamps", () => {
+  const sameTimeTasks: Task[] = [
+    { id: "KB-001", title: "First", description: "First task", column: "todo" as Column, dependencies: [], steps: [], currentStep: 0, log: [], createdAt: "2026-01-01T00:00:00Z", updatedAt: "2026-01-01T00:00:00Z" },
+    { id: "KB-002", title: "Second", description: "Second task", column: "todo" as Column, dependencies: [], steps: [], currentStep: 0, log: [], createdAt: "2026-01-01T00:00:00Z", updatedAt: "2026-01-01T00:00:00Z" },
+    { id: "KB-003", title: "Third", description: "Third task", column: "todo" as Column, dependencies: [], steps: [], currentStep: 0, log: [], createdAt: "2026-01-01T00:00:00Z", updatedAt: "2026-01-01T00:00:00Z" },
+  ];
+
+  it("renders tasks with identical createdAt sorted newest-ID-first (descending numeric ID)", () => {
+    renderCard(sameTimeTasks);
+    fireEvent.click(screen.getByText(/Deps/));
+    const items = document.querySelectorAll(".dep-dropdown-item");
+    expect(items).toHaveLength(3);
+    const ids = Array.from(items).map((el) => el.querySelector(".dep-dropdown-id")?.textContent);
+    expect(ids).toEqual(["KB-003", "KB-002", "KB-001"]);
+  });
+
+  it("preserves newest-ID-first order when search filter is applied with identical timestamps", () => {
+    renderCard(sameTimeTasks);
+    fireEvent.click(screen.getByText(/Deps/));
+    const input = document.querySelector(".dep-dropdown-search") as HTMLInputElement;
+    fireEvent.change(input, { target: { value: "KB-00" } });
+    const items = document.querySelectorAll(".dep-dropdown-item");
+    expect(items).toHaveLength(3);
+    const ids = Array.from(items).map((el) => el.querySelector(".dep-dropdown-id")?.textContent);
+    expect(ids).toEqual(["KB-003", "KB-002", "KB-001"]);
+  });
+});
+
 describe("InlineCreateCard dependency dropdown search", () => {
   const testTasks: Task[] = [
     { id: "KB-001", title: "Fix login", description: "Login page broken", column: "todo" as Column, dependencies: [], steps: [], currentStep: 0, log: [], createdAt: "2026-01-01T00:00:00Z", updatedAt: "2026-01-01T00:00:00Z" },

packages/dashboard/app/components/__tests__/TaskDetailModal.test.tsx

@@ -540,6 +540,34 @@ describe("TaskDetailModal", () => {
     expect(ids).toEqual(["KB-003", "KB-002", "KB-001"]);
   });
 
+  it("renders tasks with identical createdAt sorted newest-ID-first in dependency dropdown", () => {
+    const allTasks: Task[] = [
+      { id: "KB-001", description: "First", column: "todo" as Column, dependencies: [], steps: [], currentStep: 0, log: [], createdAt: "2026-01-01T00:00:00Z", updatedAt: "2026-01-01T00:00:00Z" },
+      { id: "KB-002", description: "Second", column: "todo" as Column, dependencies: [], steps: [], currentStep: 0, log: [], createdAt: "2026-01-01T00:00:00Z", updatedAt: "2026-01-01T00:00:00Z" },
+      { id: "KB-003", description: "Third", column: "todo" as Column, dependencies: [], steps: [], currentStep: 0, log: [], createdAt: "2026-01-01T00:00:00Z", updatedAt: "2026-01-01T00:00:00Z" },
+      { id: "KB-099", description: "Self", column: "in-progress" as Column, dependencies: [], steps: [], currentStep: 0, log: [], createdAt: "2026-01-01T00:00:00Z", updatedAt: "2026-01-01T00:00:00Z" },
+    ];
+
+    render(
+      <TaskDetailModal
+        task={makeTask({ dependencies: [] })}
+        tasks={allTasks}
+        onClose={noop}
+        onMoveTask={noopMove}
+        onDeleteTask={noopDelete}
+        onMergeTask={noopMerge}
+        addToast={noop}
+      />,
+    );
+
+    fireEvent.click(screen.getByText("Add Dependency"));
+    const items = document.querySelectorAll(".dep-dropdown-item");
+    expect(items).toHaveLength(3);
+
+    const ids = Array.from(items).map((el) => el.querySelector(".dep-dropdown-id")?.textContent);
+    expect(ids).toEqual(["KB-003", "KB-002", "KB-001"]);
+  });
+
   describe("tab toggle", () => {
     it("defaults to the Definition tab", () => {
       const { container } = render(