fix: always replay the current todo list on session/load

CHANGELOG.md

@@ -7,6 +7,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.11.5] - 2026-08-22
+
+### Fixed
+
+- `session/load` always replays the current todo list: the shared
+  per-session differ only fires PlanUpdate on plan CHANGE, so a re-attaching
+  client (the mobile app always re-attaches) never learned a plan a previous
+  client had already seen. The load path now runs a throwaway differ whose
+  "__none__" sentinel makes diffPlan always emit, while the shared differ's
+  full diff still runs for its mark-seen side effect (turn completion must
+  not re-emit replayed history).
+- Regression test in `tests/load-plan-replay.test.ts` (fails without the
+  fix: a second load emits no PlanUpdate).
+
 ## [0.11.4] - 2026-08-22
 
 ### Fixed

package.json

@@ -1,6 +1,6 @@
 {
   "name": "zcode-acp-server",
-  "version": "0.11.4",
+  "version": "0.11.5",
   "description": "Agent Client Protocol (ACP) server bridging headless ZCode to editors like Zed and JetBrains.",
   "type": "module",
   "license": "Apache-2.0",

src/handlers/session.ts

@@ -508,12 +508,19 @@ export async function loadSession(
   );
 
   // Replay the existing todo list as an initial plan so a loaded session shows
-  // its todos immediately (filter to PlanUpdate only — text/tools were already
-  // replayed above and the differ hasn't mark_seen'd this history).
+  // its todos immediately.
   try {
     const snapshot = await buildSnapshot(server, zcodeSid);
     const loadDiffer = getOrCreateDiffer(server, zcodeSid);
-    const planEvents = loadDiffer.diff(snapshot).filter((e) => e.kind === "PlanUpdate");
+    // Keep the shared differ's full diff for its mark-seen side effect on the
+    // replayed history (next turn-completion diff must not re-emit it).
+    loadDiffer.diff(snapshot);
+    // Emit the CURRENT todos on every load: the shared differ only fires on
+    // CHANGE since its lastPlanSig already matches after any prior client's
+    // diff — a re-attaching client (the mobile app always re-attaches) would
+    // otherwise never learn a plan a previous client already saw. A throwaway
+    // differ starts at the "__none__" sentinel, so diffPlan always emits.
+    const planEvents = new ProjectionDiffer().diffPlan(snapshot.todos ?? []);
     for (const iev of planEvents) {
       await dispatchEvent(server, cx, acpSid, iev, `load_${randomUUID().slice(0, 8)}`);
     }

tests/load-plan-replay.test.ts

@@ -0,0 +1,97 @@
+/**
+ * session/load must emit the CURRENT todo list as a PlanUpdate on every load.
+ *
+ * The shared per-session differ only fires on plan CHANGE: once any client
+ * attached and its diff aligned `lastPlanSig`, a re-attaching client (the
+ * mobile app always re-attaches) would never learn the plan a previous
+ * client already saw. The load path therefore runs a throwaway differ whose
+ * "__none__" sentinel makes diffPlan always emit — while still running the
+ * shared differ's full diff for its mark-seen side effect.
+ */
+
+import type * as acp from "@agentclientprotocol/sdk";
+import { describe, expect, it, vi } from "vitest";
+
+import type { ZcodeBackend } from "../src/backend/client.js";
+import { loadSession } from "../src/handlers/session.js";
+import { ZcodeAcpServer } from "../src/server.js";
+
+vi.mock("../src/tasks-index.js", () => ({
+  upsertSessionTask: async () => true,
+  updateSessionTitle: async () => true,
+}));
+
+const TODOS = [{ content: "wire the fix", status: "in_progress", priority: "high" }];
+
+function fakeBackend(): ZcodeBackend {
+  return {
+    isDead: false,
+    request: async (_id: number, method: string) => {
+      switch (method) {
+        case "workspace/updateProviderRegistry":
+        case "session/resume":
+          return { result: {} };
+        case "session/subscribe":
+          return { result: { eventSeq: 0 } };
+        case "session/read":
+          return { result: { projection: { status: "idle" }, todos: TODOS } };
+        case "session/messages":
+          return {
+            result: {
+              messages: [
+                { info: { id: "m1", role: "user" }, parts: [{ type: "text", text: "hi" }] },
+              ],
+            },
+          };
+        default:
+          return { result: {} };
+      }
+    },
+    send: () => {},
+    pollServerRequests: () => [],
+    registerEventListener: () => {},
+    unregisterEventListener: () => {},
+  } as unknown as ZcodeBackend;
+}
+
+/** cx that records every session/update notification. */
+function collectCx(): { cx: acp.AgentContext; updates: unknown[] } {
+  const updates: unknown[] = [];
+  const cx = {
+    notify: async (_method: string, params: Record<string, unknown>) => {
+      updates.push(params);
+    },
+  } as unknown as acp.AgentContext;
+  return { cx, updates };
+}
+
+const planUpdates = (updates: unknown[]) =>
+  updates.filter(
+    (u) => (u as { update?: { sessionUpdate?: string } }).update?.sessionUpdate === "plan",
+  );
+
+describe("session/load plan replay", () => {
+  it("emits a PlanUpdate on every load, even when the shared differ already saw the plan", async () => {
+    const server = new ZcodeAcpServer();
+    server.backend = fakeBackend();
+    server.registerSession("s-plan", "sess_plan");
+
+    const first = collectCx();
+    await loadSession(server, { sessionId: "s-plan" } as acp.LoadSessionRequest, first.cx);
+    expect(planUpdates(first.updates)).toHaveLength(1);
+
+    // Re-attach: the shared differ's lastPlanSig already matches, but the
+    // re-attaching client must still learn the current todos.
+    const second = collectCx();
+    await loadSession(server, { sessionId: "s-plan" } as acp.LoadSessionRequest, second.cx);
+    const plans = planUpdates(second.updates);
+    expect(plans).toHaveLength(1);
+    expect(
+      (plans[0] as { update: { entries: Array<{ content: string }> } }).update.entries,
+    ).toEqual(
+      [{ content: "wire the fix", status: "in_progress", priority: "high" }].map((e) =>
+        expect.objectContaining(e),
+      ),
+    );
+  });
+});