diff --git a/src/components/chat/hooks/useChatProviderState.ts b/src/components/chat/hooks/useChatProviderState.ts
index 0657c75..3b4e633 100644
--- a/src/components/chat/hooks/useChatProviderState.ts
+++ b/src/components/chat/hooks/useChatProviderState.ts
@@ -16,6 +16,12 @@ const getPermissionModesForProvider = (provider: LLMProvider): PermissionMode[]
   return ['default', 'acceptEdits', 'bypassPermissions', 'plan'];
 };
 
+// Per-session model persistence keys.
+// Global key (`${provider}-model`) holds the "last used" default for NEW sessions.
+// Session key (`${provider}-model-${sessionId}`) pins the model for that session.
+const globalModelKey = (provider: string) => `${provider}-model`;
+const sessionModelKey = (provider: string, sessionId: string) => `${provider}-model-${sessionId}`;
+
 interface UseChatProviderStateArgs {
   selectedSession: ProjectSession | null;
 }
@@ -26,18 +32,21 @@ export function useChatProviderState({ selectedSession }: UseChatProviderStateAr
   const [provider, setProvider] = useState<LLMProvider>(() => {
     return (localStorage.getItem('selected-provider') as LLMProvider) || 'claude';
   });
-  const [cursorModel, setCursorModel] = useState<string>(() => {
-    return localStorage.getItem('cursor-model') || CURSOR_MODELS.DEFAULT;
-  });
-  const [claudeModel, setClaudeModel] = useState<string>(() => {
-    return localStorage.getItem('claude-model') || CLAUDE_MODELS.DEFAULT;
-  });
-  const [codexModel, setCodexModel] = useState<string>(() => {
-    return localStorage.getItem('codex-model') || CODEX_MODELS.DEFAULT;
-  });
-  const [geminiModel, setGeminiModel] = useState<string>(() => {
-    return localStorage.getItem('gemini-model') || GEMINI_MODELS.DEFAULT;
-  });
+
+  // Initial model values: prefer the per-session pin if a session is already
+  // selected on mount, otherwise the global last-used default.
+  const initialModel = (p: string, fallback: string) => {
+    if (selectedSession?.id) {
+      const pinned = localStorage.getItem(sessionModelKey(p, selectedSession.id));
+      if (pinned) return pinned;
+    }
+    return localStorage.getItem(globalModelKey(p)) || fallback;
+  };
+
+  const [cursorModel, setCursorModelState] = useState<string>(() => initialModel('cursor', CURSOR_MODELS.DEFAULT));
+  const [claudeModel, setClaudeModelState] = useState<string>(() => initialModel('claude', CLAUDE_MODELS.DEFAULT));
+  const [codexModel, setCodexModelState] = useState<string>(() => initialModel('codex', CODEX_MODELS.DEFAULT));
+  const [geminiModel, setGeminiModelState] = useState<string>(() => initialModel('gemini', GEMINI_MODELS.DEFAULT));
 
   // Live model lists — fall back to static constants until API responds
   const [claudeModelOptions, setClaudeModelOptions] = useState<ModelOption[]>(CLAUDE_MODELS.OPTIONS);
@@ -45,7 +54,43 @@ export function useChatProviderState({ selectedSession }: UseChatProviderStateAr
   const [geminiModelOptions] = useState<ModelOption[]>(GEMINI_MODELS.OPTIONS);
   const [cursorModelOptions] = useState<ModelOption[]>(CURSOR_MODELS.OPTIONS);
 
-  // Fetch live model list and validate the saved claude model
+  // Persisted setters: write BOTH the per-session pin (if a session is active)
+  // and the global last-used default, then update state.
+  const makePersistedSetter = useCallback(
+    (p: string, setState: (v: string) => void) => (value: string) => {
+      setState(value);
+      localStorage.setItem(globalModelKey(p), value);
+      if (selectedSession?.id) {
+        localStorage.setItem(sessionModelKey(p, selectedSession.id), value);
+      }
+    },
+    [selectedSession?.id],
+  );
+
+  const setCursorModel = useCallback(makePersistedSetter('cursor', setCursorModelState), [makePersistedSetter]);
+  const setClaudeModel = useCallback(makePersistedSetter('claude', setClaudeModelState), [makePersistedSetter]);
+  const setCodexModel = useCallback(makePersistedSetter('codex', setCodexModelState), [makePersistedSetter]);
+  const setGeminiModel = useCallback(makePersistedSetter('gemini', setGeminiModelState), [makePersistedSetter]);
+
+  // When the selected session changes, load each provider's pinned model for
+  // that session (falling back to the global default). This is what stops a
+  // model picked in session A from leaking into session B.
+  useEffect(() => {
+    if (!selectedSession?.id) {
+      return;
+    }
+    const load = (p: string, setState: (v: string) => void, fallback: string) => {
+      const pinned = localStorage.getItem(sessionModelKey(p, selectedSession.id));
+      const next = pinned || localStorage.getItem(globalModelKey(p)) || fallback;
+      setState(next);
+    };
+    load('cursor', setCursorModelState, CURSOR_MODELS.DEFAULT);
+    load('claude', setClaudeModelState, CLAUDE_MODELS.DEFAULT);
+    load('codex', setCodexModelState, CODEX_MODELS.DEFAULT);
+    load('gemini', setGeminiModelState, GEMINI_MODELS.DEFAULT);
+  }, [selectedSession?.id]);
+
+  // Fetch live Claude model list and validate the current claude model
   useEffect(() => {
     authenticatedFetch('/api/models')
       .then((res) => {
@@ -57,18 +102,21 @@ export function useChatProviderState({ selectedSession }: UseChatProviderStateAr
         const options: ModelOption[] = data.claude;
         setClaudeModelOptions(options);
 
-        // Validate saved model — if it's no longer in the list, reset to default
-        setClaudeModel((current) => {
+        setClaudeModelState((current) => {
           const valid = options.some((o) => o.value === current);
           if (valid) return current;
           const fallback = options[0]?.value ?? CLAUDE_MODELS.DEFAULT;
-          localStorage.setItem('claude-model', fallback);
+          localStorage.setItem(globalModelKey('claude'), fallback);
+          if (selectedSession?.id) {
+            localStorage.setItem(sessionModelKey('claude', selectedSession.id), fallback);
+          }
           return fallback;
         });
       })
       .catch(() => {
-        // Static fallback already in place — nothing to do
+        // Static fallback already in place
       });
+    // eslint-disable-next-line react-hooks/exhaustive-deps
   }, []);
 
   const lastProviderRef = useRef(provider);
@@ -119,8 +167,8 @@ export function useChatProviderState({ selectedSession }: UseChatProviderStateAr
         }
 
         const modelId = data.config.model.modelId as string;
-        if (!localStorage.getItem('cursor-model')) {
-          setCursorModel(modelId);
+        if (!localStorage.getItem(globalModelKey('cursor'))) {
+          setCursorModelState(modelId);
         }
       })
       .catch((error) => {