From 28ee287df4fc9419335ca1905cc04d7721f15f96 Mon Sep 17 00:00:00 2001
From: Will Adams-Keane <willadamskeane@gmail.com>
Date: Fri, 30 Oct 2026 12:40:21 -0500
Subject: [PATCH] fix(client): a new thread's content no longer stays blank
 after an early 404

A thread-detail fetch that runs before the thread's create command commits gets a 404.
The client marked the thread deleted and kept that in the resume cache, so ChatView, mounting
after creation, resumed as deleted and never loaded the thread. Only a delete event is now
remembered across mounts; an HTTP miss is not.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
---
 .../src/state/threads-sync.test.ts            | 25 +++++++++++++++++++
 packages/client-runtime/src/state/threads.ts  |  2 ++
 2 files changed, 27 insertions(+)

diff --git a/packages/client-runtime/src/state/threads-sync.test.ts b/packages/client-runtime/src/state/threads-sync.test.ts
index eaf1751a1c2d2..593e29286b66c 100644
--- a/packages/client-runtime/src/state/threads-sync.test.ts
+++ b/packages/client-runtime/src/state/threads-sync.test.ts
@@ -673,6 +673,31 @@ describe("EnvironmentThreads", () => {
     }),
   );
 
+  it.effect("asks the server again after an HTTP miss, since the thread may not exist yet", () =>
+    Effect.gen(function* () {
+      const resumeCache: NonNullable<Parameters<typeof makeEnvironmentThreadState>[1]> = {
+        snapshot: undefined,
+        owner: undefined,
+      };
+      yield* Effect.scoped(
+        Effect.gen(function* () {
+          const first = yield* makeHarness({ httpSnapshot: { _tag: "missing" }, resumeCache });
+          yield* awaitThreadState(first.observed, (value) => value.status === "deleted");
+        }),
+      );
+      const resumed = yield* makeHarness({
+        resumeCache,
+        httpSnapshot: {
+          _tag: "present",
+          snapshot: { snapshotSequence: CACHED_SNAPSHOT_SEQUENCE, projection: BASE_PROJECTION },
+        },
+      });
+      const state = yield* awaitThreadState(resumed.observed, (value) => value.status === "live");
+      expect(Option.getOrThrow(state.data)).toEqual(BASE_PROJECTION);
+      expect(yield* Ref.get(resumed.loaderCalls)).toBe(1);
+    }),
+  );
+
   it.effect("resumes a warm cache via afterSequence without an HTTP fetch", () =>
     Effect.gen(function* () {
       const harness = yield* makeHarness({ cached: BASE_PROJECTION });
diff --git a/packages/client-runtime/src/state/threads.ts b/packages/client-runtime/src/state/threads.ts
index c7b22d9dcdff0..5c6622b5ad9ae 100644
--- a/packages/client-runtime/src/state/threads.ts
+++ b/packages/client-runtime/src/state/threads.ts
@@ -998,6 +998,8 @@ export const makeEnvironmentThreadState = Effect.fn("EnvironmentThreadState.make
             }
             case "missing": {
               yield* setDeleted();
+              // A 404 also means "not created yet". Only a delete event may outlive this mount.
+              if (resumeCache?.owner === owner) resumeCache.snapshot = undefined;
               return yield* Effect.never;
             }
             case "unavailable": {