diff --git a/mobile/src/agent-history/agent-history-scope-paths.ts b/mobile/src/agent-history/agent-history-scope-paths.ts
index 5d08ff2e3cf..da3b98457d2 100644
--- a/mobile/src/agent-history/agent-history-scope-paths.ts
+++ b/mobile/src/agent-history/agent-history-scope-paths.ts
@@ -3,13 +3,10 @@ import {
   normalizeRuntimePathForComparison
 } from '../../../src/shared/cross-platform-path'
 import type { Worktree } from '../worktree/workspace-list-types'
-import type { AiVaultScope } from '../../../src/shared/ai-vault-types'
-
-// Why: the aiVault.listSessions RPC rejects (does not truncate) scopePaths past
-// AI_VAULT_SCOPE_PATHS_MAX_COUNT, so a repo with many sibling worktrees must cap
-// here or the whole project-scope load hard-fails. scopePaths only widen
-// discovery, so a truncated list omits some siblings instead of erroring.
-const MOBILE_AI_VAULT_SCOPE_PATHS_MAX = 64
+import {
+  AI_VAULT_SCOPE_PATHS_MAX_COUNT,
+  type AiVaultScope
+} from '../../../src/shared/ai-vault-types'
 
 // Why: the renderer's deriveAiVault* helpers are renderer-located and
 // Metro-unresolvable, so mobile does its own minimal derivation seeded by the
@@ -34,7 +31,9 @@ export function deriveMobileAiVaultScopePaths(
   // covers same-repo sibling worktrees so the project view stays complete.
   if (scope === 'project') {
     for (const worktree of liveWorktrees) {
-      if (paths.length >= MOBILE_AI_VAULT_SCOPE_PATHS_MAX) {
+      // Why: the RPC rejects (does not truncate) oversized scopePaths, and the
+      // list only widens discovery — dropping tail siblings beats hard-failing.
+      if (paths.length >= AI_VAULT_SCOPE_PATHS_MAX_COUNT) {
         break
       }
       if (worktree.repoId === activeWorktree.repoId) {
diff --git a/src/main/runtime/rpc/methods/ai-vault.ts b/src/main/runtime/rpc/methods/ai-vault.ts
index 7c80dcb1b17..37a73a8f93f 100644
--- a/src/main/runtime/rpc/methods/ai-vault.ts
+++ b/src/main/runtime/rpc/methods/ai-vault.ts
@@ -1,12 +1,12 @@
 import { z } from 'zod'
 import { defineMethod, type RpcMethod } from '../core'
 import { OptionalBoolean } from '../schemas'
+import { AI_VAULT_SCOPE_PATHS_MAX_COUNT } from '../../../../shared/ai-vault-types'
 
 // Why: bound limit + scopePaths so a client cannot force an unbounded scan.
 // Each scopePath is a host-local match prefix (validated/capped, never used for
 // traversal); the count/length caps mirror the worktree-schemas bounding style.
 const AI_VAULT_SCOPE_PATH_MAX_LENGTH = 4096
-const AI_VAULT_SCOPE_PATHS_MAX_COUNT = 64
 const AI_VAULT_LIMIT_MAX = 2000
 
 export const AiVaultListSessionsParams = z.object({
diff --git a/src/shared/ai-vault-types.ts b/src/shared/ai-vault-types.ts
index 1dddff36318..4309b68581e 100644
--- a/src/shared/ai-vault-types.ts
+++ b/src/shared/ai-vault-types.ts
@@ -23,6 +23,10 @@ export const AI_VAULT_AGENTS = [
   'kimi'
 ] as const satisfies readonly TuiAgent[]
 
+// Why: the aiVault.listSessions RPC schema REJECTS (not truncates) requests
+// past this bound, so every scopePaths producer must cap against the same value.
+export const AI_VAULT_SCOPE_PATHS_MAX_COUNT = 64
+
 export type AiVaultAgent = (typeof AI_VAULT_AGENTS)[number]
 export type AiVaultScope = 'workspace' | 'project' | 'all'
 export type AiVaultSort = 'updated' | 'created'