diff --git a/docs/config-catalog.md b/docs/config-catalog.md
index b7d8e9edd6..30c448ba03 100644
--- a/docs/config-catalog.md
+++ b/docs/config-catalog.md
@@ -71,7 +71,7 @@ export interface Config {
 
 Depends on: [`agentCore`](../packages/examples/agent-spine-demo/src/index.ts) · [`ToolsConfig`](#deepseek-aidsh-tools)
 
-Source: [`packages/examples/acp-demo/src/index.ts:32`](../packages/examples/acp-demo/src/index.ts)
+Source: [`packages/examples/acp-demo/src/index.ts:33`](../packages/examples/acp-demo/src/index.ts)
 
 ## `@deepseek-ai/dsh-agent-loop`
 
@@ -827,7 +827,7 @@ export interface Config {
 
 Depends on: [`agentCore`](../packages/examples/agent-spine-demo/src/index.ts) · [`ToolsConfig`](#deepseek-aidsh-tools)
 
-Source: [`packages/examples/stdio-demo/src/index.ts:38`](../packages/examples/stdio-demo/src/index.ts)
+Source: [`packages/examples/stdio-demo/src/index.ts:40`](../packages/examples/stdio-demo/src/index.ts)
 
 ## `@deepseek-ai/dsh-subagent-acp`
 
diff --git a/packages/examples/acp-demo/src/index.ts b/packages/examples/acp-demo/src/index.ts
index caa6ffd582..6785e5f957 100644
--- a/packages/examples/acp-demo/src/index.ts
+++ b/packages/examples/acp-demo/src/index.ts
@@ -19,6 +19,7 @@ import SessionPersistenceJsonl from '@deepseek-ai/dsh-session-persistence-jsonl'
 import UserInteractionService from '@deepseek-ai/dsh-user-interaction'
 
 export const name = 'acp-demo'
+const DEFAULT_PERSISTENCE_ROOT = './.sessions'
 
 /**
  * App config: the swappable per-deployment values. `provider` and `model` configure the
@@ -70,9 +71,7 @@ export const Config: z<Config> = z.object({
   toolOrder: z.array(z.string()).default(undefined as unknown as string[]),
   tools: ToolRegistry.Config,
   dshHome: z.string(),
-  // TODO(single-default-literal): share this schema default and the defensive
-  // apply() fallback through one named constant while retaining both boundaries.
-  persistenceRoot: z.string().default('./.sessions'),
+  persistenceRoot: z.string().default(DEFAULT_PERSISTENCE_ROOT),
   workspaceContext: z.union([z.const(false), workspaceContext.Config]).required(),
   skills: agentCore.SkillConfigSchema,
   toolBash: agentCore.ToolBashConfigSchema,
@@ -90,6 +89,6 @@ export const Config: z<Config> = z.object({
 export function apply(ctx: Context, config: Config): void {
   ctx.plugin(agentCore, agentCore.pickSpineConfig(config))
   ctx.plugin(UserInteractionService)
-  ctx.plugin(SessionPersistenceJsonl, { root: config.persistenceRoot ?? './.sessions' })
+  ctx.plugin(SessionPersistenceJsonl, { root: config.persistenceRoot ?? DEFAULT_PERSISTENCE_ROOT })
   ctx.plugin(acp, { provider: config.provider, model: config.model })
 }
diff --git a/packages/examples/acp-demo/tests/acp-agent.spec.ts b/packages/examples/acp-demo/tests/acp-agent.spec.ts
index c033056f12..10ee749f8c 100644
--- a/packages/examples/acp-demo/tests/acp-agent.spec.ts
+++ b/packages/examples/acp-demo/tests/acp-agent.spec.ts
@@ -83,7 +83,7 @@ describe('dsh-acp-demo composition', () => {
   })
 
   it('defaults the persistence root when omitted', async () => {
-    // Exercises the `?? './.sessions'` fallback for a direct-apply caller that
+    // Exercises the `DEFAULT_PERSISTENCE_ROOT` fallback for a direct-apply caller that
     // bypasses the schema's `.default(...)`: call `apply` directly (not via
     // `ctx.plugin`, which validates+defaults the config first) with no
     // persistenceRoot, so the runtime fallback is the one that fires.
diff --git a/packages/examples/stdio-demo/src/index.ts b/packages/examples/stdio-demo/src/index.ts
index 71196ed647..0fb43cdff1 100644
--- a/packages/examples/stdio-demo/src/index.ts
+++ b/packages/examples/stdio-demo/src/index.ts
@@ -24,6 +24,8 @@ import * as toolAskUser from '@deepseek-ai/dsh-tool-ask-user'
 import * as uiStdio from '@deepseek-ai/dsh-stdio'
 
 export const name = 'stdio-demo'
+const DEFAULT_PERSISTENCE_ROOT = './.sessions'
+const DEFAULT_WELCOME = 'ready.'
 
 /**
  * App config: the swappable per-demo values, each routed to where the app wires
@@ -81,10 +83,8 @@ export const Config: z<Config> = z.object({
   toolOrder: z.array(z.string()).default(undefined as unknown as string[]),
   tools: ToolRegistry.Config,
   dshHome: z.string(),
-  // TODO(single-default-literal): share these schema defaults and defensive
-  // apply() fallbacks through named constants while retaining both boundaries.
-  persistenceRoot: z.string().default('./.sessions'),
-  welcome: z.string().default('ready.'),
+  persistenceRoot: z.string().default(DEFAULT_PERSISTENCE_ROOT),
+  welcome: z.string().default(DEFAULT_WELCOME),
   skills: agentCore.SkillConfigSchema,
   toolBash: agentCore.ToolBashConfigSchema,
   toolTasks: agentCore.ToolTasksConfigSchema,
@@ -104,10 +104,10 @@ export function apply(ctx: Context, config: Config): void {
   const resumeSessionId = config.resumeSessionId === '' ? undefined : config.resumeSessionId
   const sessionId = SessionId(resumeSessionId ?? `main-session-${randomUUID()}`)
   ctx.plugin(ConsoleExporter)
-  ctx.plugin(SessionPersistenceJsonl, { root: config.persistenceRoot ?? './.sessions' })
+  ctx.plugin(SessionPersistenceJsonl, { root: config.persistenceRoot ?? DEFAULT_PERSISTENCE_ROOT })
   ctx.plugin(UserInteractionService)
   ctx.plugin(uiStdio, {
-    welcome: config.welcome ?? 'ready.',
+    welcome: config.welcome ?? DEFAULT_WELCOME,
     sessionId,
   })
   ctx.plugin(agentCore, {
diff --git a/packages/examples/stdio-demo/tests/stdio-agent.spec.ts b/packages/examples/stdio-demo/tests/stdio-agent.spec.ts
index ddfc0ec95d..7ef169ff06 100644
--- a/packages/examples/stdio-demo/tests/stdio-agent.spec.ts
+++ b/packages/examples/stdio-demo/tests/stdio-agent.spec.ts
@@ -103,7 +103,7 @@ describe('dsh-stdio-demo app', () => {
 
   it('defaults persistenceRoot and welcome when omitted', async () => {
     // Direct apply (NOT via ctx.plugin, which validates+defaults the config
-    // first) so the runtime `?? './.sessions'` / `?? 'ready.'` fallbacks on
+    // first) so the runtime `DEFAULT_PERSISTENCE_ROOT` / `DEFAULT_WELCOME` fallbacks on
     // apply()'s last two lines are the ones that fire — covering a
     // schema-bypassing direct-mount caller.
     const ctx = new Context()