diff --git a/desktop/src-tauri/src/persona_catalog_tests.rs b/desktop/src-tauri/src/persona_catalog_tests.rs
index 0532660b4..d3175ef98 100644
--- a/desktop/src-tauri/src/persona_catalog_tests.rs
+++ b/desktop/src-tauri/src/persona_catalog_tests.rs
@@ -190,3 +190,46 @@ fn exact_tags_reject_duplicates_and_extra_fields() {
     assert_eq!(coordinate_tag(&extended, "d").as_deref(), Some("reviewer"));
     assert_eq!(exact_tag(&extended, "shared"), None);
 }
+
+/// Pins the serialized DTO output against the renderer's catalog contract.
+/// The Tauri generic is only a TypeScript assertion; serde's bytes are the
+/// actual boundary, so populate every optional field and compare the value.
+#[test]
+fn serialized_catalog_matches_the_typescript_contract() {
+    let publication = PersonaCatalogPublication {
+        event_id: "ev1".into(),
+        owner_pubkey: "owner".into(),
+        source_persona_id: "persona-1".into(),
+        created_at: 42,
+        agent: CatalogAgentProjection {
+            display_name: "Ada".into(),
+            avatar_url: Some("https://example.com/a.png".into()),
+            system_prompt: "be kind".into(),
+            runtime: Some("acp".into()),
+            model: Some("m1".into()),
+            provider: Some("p1".into()),
+            name_pool: vec!["Ada".into(), "Lin".into()],
+            respond_to: Some("mentions".into()),
+            parallelism: Some(2),
+        },
+    };
+    let actual = serde_json::to_value(vec![publication]).unwrap();
+    let expected = serde_json::json!([{
+        "eventId": "ev1",
+        "ownerPubkey": "owner",
+        "sourcePersonaId": "persona-1",
+        "createdAt": 42,
+        "agent": {
+            "displayName": "Ada",
+            "avatarUrl": "https://example.com/a.png",
+            "systemPrompt": "be kind",
+            "runtime": "acp",
+            "model": "m1",
+            "provider": "p1",
+            "namePool": ["Ada", "Lin"],
+            "respondTo": "mentions",
+            "parallelism": 2,
+        },
+    }]);
+    assert_eq!(actual, expected);
+}
diff --git a/desktop/src-tauri/src/unread_catch_up.rs b/desktop/src-tauri/src/unread_catch_up.rs
index e08342c06..c7de5dae8 100644
--- a/desktop/src-tauri/src/unread_catch_up.rs
+++ b/desktop/src-tauri/src/unread_catch_up.rs
@@ -53,7 +53,11 @@ pub(crate) struct UnreadCatchUpResponse {
 }
 
 #[derive(Serialize)]
-#[serde(tag = "status", rename_all = "camelCase")]
+#[serde(
+    tag = "status",
+    rename_all = "camelCase",
+    rename_all_fields = "camelCase"
+)]
 enum ChannelResult {
     Success {
         channel_id: String,
@@ -271,14 +275,7 @@ fn classify_batch(
                     .channel
                     .read_at
                     .is_some_and(|read_at| event.created_at <= read_at)
-                || !should_notify(
-                    &event,
-                    &item.channel.id,
-                    &self_pubkey,
-                    request,
-                    &participated,
-                    &authored,
-                )
+                || !should_notify(&event, &self_pubkey, request, &participated, &authored)
             {
                 continue;
             }
@@ -384,7 +381,6 @@ fn thread_reference(tags: &[Vec<String>]) -> ThreadReference {
 
 fn should_notify(
     event: &EventView,
-    _channel_id: &str,
     self_pubkey: &str,
     request: &UnreadCatchUpRequest,
     participated: &HashSet<String>,
@@ -556,4 +552,96 @@ mod tests {
         );
         assert_eq!(*max_trigger, 12);
     }
+
+    /// Pins the SERIALIZED wire contract against `tauriUnreadCatchUp.ts`.
+    ///
+    /// Asserts on serde's OUTPUT, not on `ChannelResult`: the renderer never
+    /// sees the Rust type, it sees bytes, through an `invokeTauri<T>` cast
+    /// that validates nothing. Every other test here inspects the enum before
+    /// serialization and the e2e bridge hand-writes the intended shape, so
+    /// without this nothing compares what Rust emits to what TypeScript
+    /// declares.
+    ///
+    /// Whole-value rather than a key list, deliberately: a key-set assertion
+    /// passes a mutant that drops the variant rename and emits `"Success"`,
+    /// which the renderer's `status === "error"` branch silently misreads.
+    /// Failure here means the merge loop throws on the first success row and
+    /// catch-up yields nothing, silently.
+    #[test]
+    fn serialized_response_matches_the_typescript_contract() {
+        let channels = vec![
+            ChannelResult::Success {
+                channel_id: "ch".into(),
+                observed_events: vec![ObservedUnreadEvent {
+                    id: "evt".into(),
+                    created_at: 11,
+                    root_id: Some("root".into()),
+                    high_priority: true,
+                    counts_toward_badge: true,
+                    counts_toward_app_badge: false,
+                }],
+                max_trigger: 11,
+                activity_rows: vec![ActivityRow {
+                    id: "evt".into(),
+                    kind: 9,
+                    pubkey: "other".into(),
+                    content: "hi".into(),
+                    created_at: 11,
+                    channel_id: "ch".into(),
+                    channel_name: "Ch".into(),
+                    tags: vec![vec!["h".into(), "ch".into()]],
+                }],
+                discovered: DiscoveredRoots {
+                    participated: vec!["root".into()],
+                    authored: Vec::new(),
+                    mentioned: Vec::new(),
+                },
+            },
+            ChannelResult::Error {
+                channel_id: "ch-2".into(),
+                error: "relay request timed out".into(),
+            },
+        ];
+
+        let actual = serde_json::to_value(UnreadCatchUpResponse { channels }).unwrap();
+        let expected = serde_json::json!({
+            "channels": [
+                {
+                    "status": "success",
+                    "channelId": "ch",
+                    "observedEvents": [{
+                        "id": "evt",
+                        "createdAt": 11,
+                        "rootId": "root",
+                        "highPriority": true,
+                        "countsTowardBadge": true,
+                        "countsTowardAppBadge": false,
+                    }],
+                    "maxTrigger": 11,
+                    "activityRows": [{
+                        "id": "evt",
+                        "kind": 9,
+                        "pubkey": "other",
+                        "content": "hi",
+                        "createdAt": 11,
+                        "channelId": "ch",
+                        "channelName": "Ch",
+                        "tags": [["h", "ch"]],
+                    }],
+                    "discovered": {
+                        "participated": ["root"],
+                        "authored": [],
+                        "mentioned": [],
+                    },
+                },
+                {
+                    "status": "error",
+                    "channelId": "ch-2",
+                    "error": "relay request timed out",
+                },
+            ]
+        });
+
+        assert_eq!(actual, expected);
+    }
 }
diff --git a/desktop/src/features/channels/useUnreadChannels.ts b/desktop/src/features/channels/useUnreadChannels.ts
index 888ad7051..34b2d9450 100644
--- a/desktop/src/features/channels/useUnreadChannels.ts
+++ b/desktop/src/features/channels/useUnreadChannels.ts
@@ -590,6 +590,10 @@ export function useUnreadChannels(
     const authoredSizeBefore = authoredRootIdsRef.current.size;
     const mentionedSizeBefore = mentionedRootIdsRef.current.size;
 
+    // Membership remains renderer-owned until E's native observed-unread store,
+    // so unchanged sets cross IPC on every catch-up. The five 1,000-entry
+    // stores bound that interim cost at roughly 332 KiB per request. Command
+    // arguments use a fetch body, so this cost is linear with no size cliff.
     void unreadCatchUp({
       channels: toFetch.map((channelId) => {
         const channel = channels.find(
@@ -621,6 +625,8 @@ export function useUnreadChannels(
         const allThreadReplies: ThreadActivityItem[] = [];
         for (const result of results) {
           if (result.status === "error") {
+            // The error arm carries only this identity; releasing its claim is
+            // what lets a failed channel retry on the next effect run.
             caughtUpChannelsRef.current.delete(result.channelId);
             continue;
           }
diff --git a/desktop/src/testing/e2eBridge.ts b/desktop/src/testing/e2eBridge.ts
index ae3ecbd04..8a31d2ad2 100644
--- a/desktop/src/testing/e2eBridge.ts
+++ b/desktop/src/testing/e2eBridge.ts
@@ -10,6 +10,7 @@ import {
   handleDeleteCustomHarness,
 } from "./e2eBridgeCustomHarnesses.ts";
 
+import type { UnreadCatchUpChannelResult } from "@/shared/api/tauriUnreadCatchUp";
 import { relayClient } from "@/shared/api/relayClient";
 import { activateRateLimit } from "@/shared/api/relayRateLimitGate";
 import { resolveAgentParallelism } from "@/features/agents/lib/agentParallelism";
@@ -13380,16 +13381,18 @@ export function maybeInstallE2eTauriMocks() {
         const request = payload as {
           request: { channels: Array<{ id: string }> };
         };
-        return {
-          channels: request.request.channels.map((channel) => ({
+        const results: UnreadCatchUpChannelResult[] =
+          request.request.channels.map((channel) => ({
             status: "success",
             channelId: channel.id,
             observedEvents: [],
             maxTrigger: 0,
             activityRows: [],
             discovered: { participated: [], authored: [], mentioned: [] },
-          })),
-        };
+          }));
+        // Keep this mock aligned with the complete Rust serde shape pinned by
+        // `serialized_response_matches_the_typescript_contract`.
+        return { channels: results };
       }
       case "agent_metric_archive_default_enabled":
         return activeConfig?.mock?.agentMetricArchiveDefaultEnabled ?? true;