diff --git a/packages/web/src/stores/composerStore.test.ts b/packages/web/src/stores/composerStore.test.ts
new file mode 100644
index 00000000..694a8684
--- /dev/null
+++ b/packages/web/src/stores/composerStore.test.ts
@@ -0,0 +1,36 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { useComposerStore } from './composerStore';
+
+describe('composerStore', () => {
+  beforeEach(() => useComposerStore.setState({ states: new Map() }));
+
+  it('starts empty for unseen channels', () => {
+    expect(useComposerStore.getState().get('ch-1')).toEqual({ draftText: '', replyTo: null, stagedTransferIds: [] });
+  });
+
+  it('attaches a transferId to the per-channel staged list', () => {
+    useComposerStore.getState().attach('ch-1', 't-1');
+    expect(useComposerStore.getState().get('ch-1').stagedTransferIds).toEqual(['t-1']);
+  });
+
+  it('removes a staged transferId', () => {
+    useComposerStore.getState().attach('ch-1', 't-1');
+    useComposerStore.getState().attach('ch-1', 't-2');
+    useComposerStore.getState().removeStaged('ch-1', 't-1');
+    expect(useComposerStore.getState().get('ch-1').stagedTransferIds).toEqual(['t-2']);
+  });
+
+  it('clear empties draft + replyTo + staged', () => {
+    useComposerStore.getState().attach('ch-1', 't-1');
+    useComposerStore.getState().setDraft('ch-1', 'hi');
+    useComposerStore.getState().setReplyTo('ch-1', { id: 'm', userId: 'u', content: 'x' });
+    useComposerStore.getState().clear('ch-1');
+    expect(useComposerStore.getState().get('ch-1')).toEqual({ draftText: '', replyTo: null, stagedTransferIds: [] });
+  });
+
+  it('attach is idempotent for the same transferId', () => {
+    useComposerStore.getState().attach('ch-1', 't-1');
+    useComposerStore.getState().attach('ch-1', 't-1');
+    expect(useComposerStore.getState().get('ch-1').stagedTransferIds).toEqual(['t-1']);
+  });
+});
diff --git a/packages/web/src/stores/composerStore.ts b/packages/web/src/stores/composerStore.ts
new file mode 100644
index 00000000..16fcebe8
--- /dev/null
+++ b/packages/web/src/stores/composerStore.ts
@@ -0,0 +1,115 @@
+import { create } from 'zustand';
+import { persist, type PersistStorage, type StorageValue } from 'zustand/middleware';
+
+export interface ComposerState {
+  draftText: string;
+  replyTo: { id: string; userId: string; content: string | null } | null;
+  stagedTransferIds: string[];
+}
+
+interface ComposerStoreState {
+  states: Map<string, ComposerState>;
+}
+
+interface ComposerStoreActions {
+  get: (channelId: string) => ComposerState;
+  attach: (channelId: string, transferId: string) => void;
+  removeStaged: (channelId: string, transferId: string) => void;
+  setDraft: (channelId: string, draft: string) => void;
+  setReplyTo: (channelId: string, replyTo: ComposerState['replyTo']) => void;
+  clear: (channelId: string) => void;
+}
+
+type ComposerStore = ComposerStoreState & ComposerStoreActions;
+
+const EMPTY: ComposerState = { draftText: '', replyTo: null, stagedTransferIds: [] };
+
+// Custom storage that serializes Map<string, ComposerState> as an array of entries.
+// Mirrors transferStore's mapAwareStorage pattern; only the `states` slice is persisted.
+const mapAwareStorage: PersistStorage<Pick<ComposerStoreState, 'states'>> = {
+  getItem: (name) => {
+    const raw = typeof localStorage !== 'undefined' ? localStorage.getItem(name) : null;
+    if (!raw) return null;
+    try {
+      const parsed = JSON.parse(raw) as { state: { states: [string, ComposerState][] }; version?: number };
+      const stateOut: Pick<ComposerStoreState, 'states'> = {
+        states: new Map<string, ComposerState>(parsed.state.states ?? []),
+      };
+      return { state: stateOut, version: parsed.version } as StorageValue<Pick<ComposerStoreState, 'states'>>;
+    } catch {
+      return null;
+    }
+  },
+  setItem: (name, value) => {
+    if (typeof localStorage === 'undefined') return;
+    const entries = Array.from(value.state.states.entries());
+    const payload = JSON.stringify({ state: { states: entries }, version: value.version });
+    try {
+      localStorage.setItem(name, payload);
+    } catch (err) {
+      console.warn(`[composerStore] persist failed:`, err);
+    }
+  },
+  removeItem: (name) => {
+    if (typeof localStorage !== 'undefined') localStorage.removeItem(name);
+  },
+};
+
+export const useComposerStore = create<ComposerStore>()(
+  persist(
+    (set, get) => ({
+      states: new Map<string, ComposerState>(),
+
+      get: (channelId) => get().states.get(channelId) ?? EMPTY,
+
+      attach: (channelId, transferId) =>
+        set((s) => {
+          const cur = s.states.get(channelId) ?? EMPTY;
+          if (cur.stagedTransferIds.includes(transferId)) return s;
+          const next = new Map(s.states);
+          next.set(channelId, { ...cur, stagedTransferIds: [...cur.stagedTransferIds, transferId] });
+          return { states: next };
+        }),
+
+      removeStaged: (channelId, transferId) =>
+        set((s) => {
+          const cur = s.states.get(channelId) ?? EMPTY;
+          const next = new Map(s.states);
+          next.set(channelId, {
+            ...cur,
+            stagedTransferIds: cur.stagedTransferIds.filter((t) => t !== transferId),
+          });
+          return { states: next };
+        }),
+
+      setDraft: (channelId, draftText) =>
+        set((s) => {
+          const cur = s.states.get(channelId) ?? EMPTY;
+          const next = new Map(s.states);
+          next.set(channelId, { ...cur, draftText });
+          return { states: next };
+        }),
+
+      setReplyTo: (channelId, replyTo) =>
+        set((s) => {
+          const cur = s.states.get(channelId) ?? EMPTY;
+          const next = new Map(s.states);
+          next.set(channelId, { ...cur, replyTo });
+          return { states: next };
+        }),
+
+      clear: (channelId) =>
+        set((s) => {
+          const next = new Map(s.states);
+          next.set(channelId, EMPTY);
+          return { states: next };
+        }),
+    }),
+    {
+      name: 'composerStore@v1',
+      version: 1,
+      storage: mapAwareStorage,
+      partialize: (s) => ({ states: s.states }),
+    },
+  ),
+);
diff --git a/packages/web/src/stores/transferStore.ts b/packages/web/src/stores/transferStore.ts
index 548ee1d2..b6c638a1 100644
--- a/packages/web/src/stores/transferStore.ts
+++ b/packages/web/src/stores/transferStore.ts
@@ -109,7 +109,11 @@ const mapAwareStorage: PersistStorage<Pick<TransferStoreState, 'transfers'>> = {
     if (typeof localStorage === 'undefined') return;
     const entries = Array.from(value.state.transfers.entries());
     const payload = JSON.stringify({ state: { transfers: entries }, version: value.version });
-    localStorage.setItem(name, payload);
+    try {
+      localStorage.setItem(name, payload);
+    } catch (err) {
+      console.warn(`[transferStore] persist failed:`, err);
+    }
   },
   removeItem: (name) => {
     if (typeof localStorage !== 'undefined') localStorage.removeItem(name);