diff --git a/apps/web/src/components/ChatView.tsx b/apps/web/src/components/ChatView.tsx
index f3145df4500..d0f6bababe9 100644
--- a/apps/web/src/components/ChatView.tsx
+++ b/apps/web/src/components/ChatView.tsx
@@ -188,6 +188,7 @@ import { useEnvironmentQuery } from "../state/query";
 import {
   primaryServerAvailableEditorsAtom,
   primaryServerKeybindingsAtom,
+  primaryServerSettingsAtom,
   serverEnvironment,
 } from "../state/server";
 import { terminalEnvironment } from "../state/terminal";
@@ -1139,6 +1140,10 @@ function ChatViewContent(props: ChatViewProps) {
     (store) => store.threadLastVisitedAtById[routeThreadKey],
   );
   const settings = useEnvironmentSettings(environmentId);
+  // New-thread defaults live in the primary environment's settings.json (the
+  // settings UI never writes to remote environments), so read them from the
+  // primary server rather than the thread's environment.
+  const primaryServerSettings = useAtomValue(primaryServerSettingsAtom);
   const setStickyComposerModelSelection = useComposerDraftStore(
     (store) => store.setStickyModelSelection,
   );
@@ -3734,7 +3739,7 @@ function ChatViewContent(props: ChatViewProps) {
     ? (draftThread?.startFromOrigin ?? false)
     : canOverrideServerThreadEnvMode
       ? (pendingServerThreadStartFromOriginByThreadId[activeThread?.id ?? ""] ??
-        settings.newWorktreesStartFromOrigin)
+        primaryServerSettings.newWorktreesStartFromOrigin)
       : false;
   const sendEnvMode = resolveSendEnvMode({
     requestedEnvMode: envMode,
@@ -5023,7 +5028,7 @@ function ChatViewContent(props: ChatViewProps) {
           envMode: mode,
           startFromOrigin: resolveNewDraftStartFromOrigin({
             envMode: mode,
-            newWorktreesStartFromOrigin: settings.newWorktreesStartFromOrigin,
+            newWorktreesStartFromOrigin: primaryServerSettings.newWorktreesStartFromOrigin,
           }),
           ...(mode === "worktree" && draftThread?.worktreePath ? { worktreePath: null } : {}),
         });
@@ -5035,7 +5040,7 @@ function ChatViewContent(props: ChatViewProps) {
       composerDraftTarget,
       draftThread?.worktreePath,
       isLocalDraftThread,
-      settings.newWorktreesStartFromOrigin,
+      primaryServerSettings.newWorktreesStartFromOrigin,
       setPendingServerThreadEnvMode,
       scheduleComposerFocus,
       setDraftThreadContext,
diff --git a/apps/web/src/components/Sidebar.tsx b/apps/web/src/components/Sidebar.tsx
index cf3fa30cf8d..217bdbd5af1 100644
--- a/apps/web/src/components/Sidebar.tsx
+++ b/apps/web/src/components/Sidebar.tsx
@@ -42,7 +42,6 @@ import { restrictToFirstScrollableAncestor, restrictToVerticalAxis } from "@dnd-
 import { CSS } from "@dnd-kit/utilities";
 import {
   type ContextMenuItem,
-  DEFAULT_SERVER_SETTINGS,
   ProjectId,
   type ScopedThreadRef,
   type ResolvedKeybindingsConfig,
@@ -80,7 +79,6 @@ import {
   readThreadShell,
   useProject,
   useProjects,
-  useServerConfigs,
   useThreadShells,
   useThreadShellsForProjectRefs,
 } from "../state/entities";
@@ -202,7 +200,7 @@ import { useCopyToClipboard } from "~/hooks/useCopyToClipboard";
 import { useIsMobile } from "~/hooks/useMediaQuery";
 import { CommandDialogTrigger } from "./ui/command";
 import { useClientSettings, useUpdateClientSettings } from "~/hooks/useSettings";
-import { primaryServerKeybindingsAtom } from "../state/server";
+import { primaryServerKeybindingsAtom, primaryServerSettingsAtom } from "../state/server";
 import {
   derivePhysicalProjectKey,
   deriveProjectGroupingOverrideKey,
@@ -1106,7 +1104,7 @@ const SidebarProjectItem = memo(function SidebarProjectItem(props: SidebarProjec
     (settings) => settings.confirmThreadArchive,
   );
   const projectGroupingSettings = useClientSettings(selectProjectGroupingSettings);
-  const serverConfigs = useServerConfigs();
+  const primaryServerSettings = useAtomValue(primaryServerSettingsAtom);
   const deleteProject = useAtomCommand(projectEnvironment.delete, {
     reportFailure: false,
   });
@@ -1894,10 +1892,10 @@ const SidebarProjectItem = memo(function SidebarProjectItem(props: SidebarProjec
             : null;
       const seedContext = resolveSidebarNewThreadSeedContext({
         projectId: member.id,
+        // The default env mode is a user preference stored on the primary
+        // environment's settings.json; remote environments never carry it.
         defaultEnvMode: resolveSidebarNewThreadEnvMode({
-          defaultEnvMode:
-            serverConfigs.get(member.environmentId)?.settings.defaultThreadEnvMode ??
-            DEFAULT_SERVER_SETTINGS.defaultThreadEnvMode,
+          defaultEnvMode: primaryServerSettings.defaultThreadEnvMode,
         }),
         activeThread:
           currentActiveThread && currentActiveThread.projectId === member.id
@@ -1946,7 +1944,7 @@ const SidebarProjectItem = memo(function SidebarProjectItem(props: SidebarProjec
         }
       })();
     },
-    [handleNewThread, isMobile, router, serverConfigs, setOpenMobile],
+    [handleNewThread, isMobile, primaryServerSettings.defaultThreadEnvMode, router, setOpenMobile],
   );
 
   const handleCreateThreadClick = useCallback(
diff --git a/apps/web/src/hooks/useHandleNewThread.ts b/apps/web/src/hooks/useHandleNewThread.ts
index 232551349db..cd8546893b0 100644
--- a/apps/web/src/hooks/useHandleNewThread.ts
+++ b/apps/web/src/hooks/useHandleNewThread.ts
@@ -1,13 +1,10 @@
+import { useAtomValue } from "@effect/atom-react";
 import {
   scopedProjectKey,
   scopeProjectRef,
   scopeThreadRef,
 } from "@t3tools/client-runtime/environment";
-import {
-  DEFAULT_RUNTIME_MODE,
-  DEFAULT_SERVER_SETTINGS,
-  type ScopedProjectRef,
-} from "@t3tools/contracts";
+import { DEFAULT_RUNTIME_MODE, type ScopedProjectRef } from "@t3tools/contracts";
 import { useParams, useRouter } from "@tanstack/react-router";
 import { useCallback, useMemo } from "react";
 import {
@@ -23,15 +20,21 @@ import {
   getProjectOrderKey,
   selectProjectGroupingSettings,
 } from "../logicalProject";
-import { readThreadShell, useProjects, useServerConfigs, useThread } from "../state/entities";
+import { readThreadShell, useProjects, useThread } from "../state/entities";
 import { resolveNewDraftStartFromOrigin } from "../lib/chatThreadActions";
+import { primaryServerSettingsAtom } from "../state/server";
 import { resolveThreadRouteTarget } from "../threadRoutes";
 import { legacyProjectCwdPreferenceKey, useUiStateStore } from "../uiStateStore";
 import { useClientSettings } from "./useSettings";
 
 export function useNewThreadHandler() {
   const projects = useProjects();
-  const serverConfigs = useServerConfigs();
+  // New-thread defaults are a user preference, and the settings UI only ever
+  // edits the primary environment's settings.json. Reading the target
+  // environment's own settings here would silently reset remote projects to
+  // the decoded defaults ("local" mode, current branch), since nothing can
+  // set those values on a remote server.
+  const primaryServerSettings = useAtomValue(primaryServerSettingsAtom);
   const projectGroupingSettings = useClientSettings(selectProjectGroupingSettings);
   const router = useRouter();
   const getCurrentRouteTarget = useCallback(() => {
@@ -64,8 +67,6 @@ export function useNewThreadHandler() {
           candidate.id === projectRef.projectId &&
           candidate.environmentId === projectRef.environmentId,
       );
-      const environmentSettings =
-        serverConfigs.get(projectRef.environmentId)?.settings ?? DEFAULT_SERVER_SETTINGS;
       const logicalProjectKey = project
         ? deriveLogicalProjectKeyFromSettings(project, projectGroupingSettings)
         : scopedProjectKey(projectRef);
@@ -161,7 +162,7 @@ export function useNewThreadHandler() {
       const draftId = newDraftId();
       const threadId = newThreadId();
       const createdAt = new Date().toISOString();
-      const initialEnvMode = options?.envMode ?? environmentSettings.defaultThreadEnvMode;
+      const initialEnvMode = options?.envMode ?? primaryServerSettings.defaultThreadEnvMode;
       return (async () => {
         setLogicalProjectDraftThreadId(logicalProjectKey, projectRef, draftId, {
           threadId,
@@ -173,7 +174,7 @@ export function useNewThreadHandler() {
             options?.startFromOrigin ??
             resolveNewDraftStartFromOrigin({
               envMode: initialEnvMode,
-              newWorktreesStartFromOrigin: environmentSettings.newWorktreesStartFromOrigin,
+              newWorktreesStartFromOrigin: primaryServerSettings.newWorktreesStartFromOrigin,
             }),
           runtimeMode: DEFAULT_RUNTIME_MODE,
         });
@@ -186,7 +187,7 @@ export function useNewThreadHandler() {
         });
       })();
     },
-    [getCurrentRouteTarget, projectGroupingSettings, projects, router, serverConfigs],
+    [getCurrentRouteTarget, primaryServerSettings, projectGroupingSettings, projects, router],
   );
 }