fix(coach): deep-link the proactive nudge to its conversation

The bottom-right launcher opened a blank new chat on an unread proactive
message instead of the thread the Coach wrote. Return the owning
conversation id from the nudge-status endpoint, have the launcher open
/coach?c=<id> on the unread path, and stamp the same deep link on the push
metadata so the notification lands in the exact conversation rather than
relying on a most-recent heuristic.

docs/api/openapi.yaml

@@ -16654,9 +16654,16 @@ components:
             unread:
               type: boolean
               description: True when that message is newer than the last time the caller opened the Coach.
+            conversationId:
+              anyOf:
+                - type: string
+                - type: "null"
+              description: Conversation holding the newest assistant message; null when none exists. The client deep-links into it
+                (`/coach?c=<id>`) on the unread path.
           required:
             - nudgedAt
             - unread
+            - conversationId
           additionalProperties: false
         error:
           type: "null"

src/app/api/insights/coach/nudge-status/route.ts

@@ -39,7 +39,11 @@ export const GET = apiHandler(async () => {
     prisma.coachMessage.findFirst({
       where: { role: "assistant", conversation: { userId: user.id } },
       orderBy: { createdAt: "desc" },
-      select: { createdAt: true },
+      // v1.22 (W5) — also return the owning conversation id so the FAB can
+      // deep-link straight into the proactive thread (`/coach?c=<id>`)
+      // instead of opening a blank new chat and relying on a most-recent
+      // heuristic to find it.
+      select: { createdAt: true, conversationId: true },
     }),
     prisma.user.findUnique({
       where: { id: user.id },
@@ -55,6 +59,10 @@ export const GET = apiHandler(async () => {
   return apiSuccess({
     nudgedAt: nudgedAt ? nudgedAt.toISOString() : null,
     unread,
+    // The conversation holding the newest assistant message. Present
+    // whenever a Coach reply exists; the FAB only consumes it on the
+    // unread path.
+    conversationId: lastAssistant?.conversationId ?? null,
   });
 });
 

src/components/insights/__tests__/layout-coach-fab.test.tsx

@@ -171,20 +171,42 @@ describe("isNudgeUnread", () => {
 
   it("is false without status or without a nudge", () => {
     expect(isNudgeUnread(undefined, null)).toBe(false);
-    expect(isNudgeUnread({ nudgedAt: null, unread: false }, null)).toBe(false);
+    expect(
+      isNudgeUnread(
+        { nudgedAt: null, unread: false, conversationId: null },
+        null,
+      ),
+    ).toBe(false);
   });
 
   it("is true for a server-unread nudge the device has not seen", () => {
-    expect(isNudgeUnread({ nudgedAt, unread: true }, null)).toBe(true);
-    expect(isNudgeUnread({ nudgedAt, unread: true }, "2026-01-01")).toBe(true);
+    expect(
+      isNudgeUnread({ nudgedAt, unread: true, conversationId: "conv-1" }, null),
+    ).toBe(true);
+    expect(
+      isNudgeUnread(
+        { nudgedAt, unread: true, conversationId: "conv-1" },
+        "2026-01-01",
+      ),
+    ).toBe(true);
   });
 
   it("is false once the server counts the nudge as read", () => {
     // The user sent a Coach message after the nudge.
-    expect(isNudgeUnread({ nudgedAt, unread: false }, null)).toBe(false);
+    expect(
+      isNudgeUnread(
+        { nudgedAt, unread: false, conversationId: "conv-1" },
+        null,
+      ),
+    ).toBe(false);
   });
 
   it("is false once this device stored the matching seen stamp", () => {
-    expect(isNudgeUnread({ nudgedAt, unread: true }, nudgedAt)).toBe(false);
+    expect(
+      isNudgeUnread(
+        { nudgedAt, unread: true, conversationId: "conv-1" },
+        nudgedAt,
+      ),
+    ).toBe(false);
   });
 });

src/components/insights/layout-coach-fab.tsx

@@ -1,7 +1,7 @@
 "use client";
 
 import { useEffect, useRef, useState } from "react";
-import { usePathname } from "next/navigation";
+import { usePathname, useRouter } from "next/navigation";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { Sparkles } from "lucide-react";
 
@@ -49,6 +49,12 @@ const NUDGE_SEEN_STORAGE_KEY = "healthlog-coach-nudge-seen";
 export interface CoachNudgeStatus {
   nudgedAt: string | null;
   unread: boolean;
+  /**
+   * v1.22 (W5) — the conversation holding the newest assistant message, so
+   * the FAB can deep-link into the proactive thread on the unread path
+   * instead of opening a blank new chat. Null when no Coach reply exists.
+   */
+  conversationId: string | null;
 }
 
 /**
@@ -70,6 +76,7 @@ export function isNudgeUnread(
 export function LayoutCoachFab() {
   const { t } = useTranslations();
   const pathname = usePathname();
+  const router = useRouter();
   const launch = useCoachLaunch();
   const flags = useFeatureFlags();
   const disableCoach = useDisableCoach();
@@ -182,6 +189,17 @@ export function LayoutCoachFab() {
     // device, not just this one. The local stamp above already hid the
     // dot for an instant paint; the mutation makes it durable.
     if (unread) markSeen.mutate();
+    // v1.22 (W5) — when the Coach has written an UNREAD proactive message,
+    // deep-link straight into that conversation (`/coach?c=<id>`) so the
+    // user lands on what the Coach said, rather than opening a blank new
+    // chat in the drawer. The full page honours `?c=` →
+    // `initialConversationId`. Fall back to the in-place drawer for the
+    // ordinary launcher case (no unread, or no conversation id yet).
+    const conversationId = status?.conversationId ?? null;
+    if (unread && conversationId) {
+      router.push(`/coach?c=${conversationId}`);
+      return;
+    }
     // v1.16.11 — open the side drawer in place (the launch context the
     // layout mount consumes) instead of navigating to the chat page;
     // the conversation arrives without losing the page underneath.

src/lib/jobs/coach-nudge.ts

@@ -877,12 +877,17 @@ export async function runCoachNudgeTick(
       // dot once the user opens the Coach). A persistence failure must
       // not swallow the notification, so it is caught locally and the
       // dispatch still fires.
+      let nudgeConversationId: string | null = null;
       try {
-        await recordNudgeImpl({
+        const recorded = await recordNudgeImpl({
           userId: user.id,
           title,
           body,
         });
+        // v1.22 (W5) — keep the conversation id so the push deep-links
+        // precisely into the proactive thread instead of the generic
+        // `/coach`, closing the most-recent-heuristic gap on the web side.
+        nudgeConversationId = recorded.conversationId;
         summary.persisted += 1;
       } catch (persistErr: unknown) {
         const message =
@@ -901,8 +906,12 @@ export async function runCoachNudgeTick(
           scheduledAt: now.toISOString(),
           trigger,
           // Deep link — the web-push sender threads this into the
-          // service-worker payload's click target.
-          url: "/coach",
+          // service-worker payload's click target. Point at the exact
+          // proactive conversation when it persisted; fall back to the
+          // generic Coach surface if persistence failed.
+          url: nudgeConversationId
+            ? `/coach?c=${nudgeConversationId}`
+            : "/coach",
         },
       });
 

src/lib/openapi/routes/coach.ts

@@ -779,6 +779,12 @@ export const coachPaths: NonNullable<ZodOpenApiObject["paths"]> = {
                     .describe(
                       "True when that message is newer than the last time the caller opened the Coach.",
                     ),
+                  conversationId: z
+                    .string()
+                    .nullable()
+                    .describe(
+                      "Conversation holding the newest assistant message; null when none exists. The client deep-links into it (`/coach?c=<id>`) on the unread path.",
+                    ),
                 }),
                 "CoachNudgeStatus",
               ),