diff --git a/runners/agent-runner/src/ipc-mcp-stdio.ts b/runners/agent-runner/src/ipc-mcp-stdio.ts
index fd0624b..5fa5e82 100644
--- a/runners/agent-runner/src/ipc-mcp-stdio.ts
+++ b/runners/agent-runner/src/ipc-mcp-stdio.ts
@@ -10,10 +10,16 @@ import { z } from 'zod';
 import fs from 'fs';
 import path from 'path';
 import { CronExpressionParser } from 'cron-parser';
-import { EJCLAW_ENV, normalizePairedRoomRole } from 'ejclaw-runners-shared';
+import {
+  DEFAULT_SCHEDULE_TASK_CONTEXT_MODE,
+  DEFAULT_TASK_CONTEXT_MODE,
+  DEFAULT_WATCH_CI_CONTEXT_MODE,
+  EJCLAW_ENV,
+  TASK_CONTEXT_MODES,
+  normalizePairedRoomRole,
+} from 'ejclaw-runners-shared';
 import {
   buildCiWatchPrompt,
-  DEFAULT_WATCH_CI_CONTEXT_MODE,
   normalizeWatchCiIntervalSeconds,
 } from './watch-ci.js';
 import { resolveHostEvidenceResponsesDir } from './host-evidence.js';
@@ -142,10 +148,10 @@ SCHEDULE VALUE FORMAT (all times are LOCAL timezone):
           'cron: "*/5 * * * *" | interval: milliseconds like "300000" | once: local timestamp like "2026-02-01T15:30:00" (no Z suffix!)',
         ),
       context_mode: z
-        .enum(['group', 'isolated'])
-        .default('group')
+        .enum(TASK_CONTEXT_MODES)
+        .default(DEFAULT_SCHEDULE_TASK_CONTEXT_MODE)
         .describe(
-          'group=runs with chat history and memory, isolated=fresh session (include context in prompt)',
+          'group=runs with chat history and memory, isolated=fresh session (include context in prompt). Default: group.',
         ),
       target_group_jid: z
         .string()
@@ -226,7 +232,7 @@ SCHEDULE VALUE FORMAT (all times are LOCAL timezone):
         schedule_value: args.schedule_value,
         agent_type: currentAgentType(),
         room_role: currentRoomRole(),
-        context_mode: args.context_mode || 'group',
+        context_mode: args.context_mode || DEFAULT_SCHEDULE_TASK_CONTEXT_MODE,
         targetJid,
         createdBy: groupFolder,
         timestamp: new Date().toISOString(),
@@ -300,7 +306,7 @@ server.tool(
         'How often to poll in seconds. Defaults to 60 for generic watchers and 15 for GitHub host-driven watchers. Generic watchers require 30+, GitHub host-driven watchers allow 10+.',
       ),
     context_mode: z
-      .enum(['group', 'isolated'])
+      .enum(TASK_CONTEXT_MODES)
       .default(DEFAULT_WATCH_CI_CONTEXT_MODE)
       .describe(
         'group=runs with chat history and memory, isolated=fresh session (include all context in check_instructions). Default: isolated.',
diff --git a/runners/agent-runner/src/watch-ci.ts b/runners/agent-runner/src/watch-ci.ts
index f452192..44cca21 100644
--- a/runners/agent-runner/src/watch-ci.ts
+++ b/runners/agent-runner/src/watch-ci.ts
@@ -1,9 +1,13 @@
+import {
+  DEFAULT_WATCH_CI_CONTEXT_MODE,
+  WATCH_CI_PROMPT_PREFIX,
+} from 'ejclaw-runners-shared';
+
 export const DEFAULT_WATCH_CI_INTERVAL_SECONDS = 60;
 export const MIN_WATCH_CI_INTERVAL_SECONDS = 30;
 export const DEFAULT_GITHUB_WATCH_CI_INTERVAL_SECONDS = 15;
 export const MIN_GITHUB_WATCH_CI_INTERVAL_SECONDS = 10;
 export const MAX_WATCH_CI_INTERVAL_SECONDS = 3600;
-export const DEFAULT_WATCH_CI_CONTEXT_MODE = 'isolated';
 
 export interface NormalizeWatchCiIntervalOptions {
   ciProvider?: 'github';
@@ -48,7 +52,7 @@ export function buildCiWatchPrompt({
   checkInstructions,
 }: BuildCiWatchPromptArgs): string {
   return `
-[BACKGROUND CI WATCH]
+${WATCH_CI_PROMPT_PREFIX}
 
 You are running as an EJClaw background CI watcher.
 
diff --git a/runners/agent-runner/test/watch-ci.test.ts b/runners/agent-runner/test/watch-ci.test.ts
index 3dcc024..4f5a21e 100644
--- a/runners/agent-runner/test/watch-ci.test.ts
+++ b/runners/agent-runner/test/watch-ci.test.ts
@@ -1,8 +1,11 @@
 import { describe, expect, it } from 'vitest';
+import {
+  DEFAULT_WATCH_CI_CONTEXT_MODE,
+  WATCH_CI_PROMPT_PREFIX,
+} from 'ejclaw-runners-shared';
 
 import {
   buildCiWatchPrompt,
-  DEFAULT_WATCH_CI_CONTEXT_MODE,
   DEFAULT_GITHUB_WATCH_CI_INTERVAL_SECONDS,
   normalizeWatchCiIntervalSeconds,
 } from '../src/watch-ci.js';
@@ -16,6 +19,7 @@ describe('watch-ci helpers', () => {
     });
 
     expect(prompt).toContain('PR #42 checks');
+    expect(prompt.startsWith(WATCH_CI_PROMPT_PREFIX)).toBe(true);
     expect(prompt).not.toContain('Task ID:');
     expect(prompt).toContain('cancel_task');
     expect(prompt).toContain('send_message');
diff --git a/runners/shared/src/index.ts b/runners/shared/src/index.ts
index c8fe8dd..e9a1eef 100644
--- a/runners/shared/src/index.ts
+++ b/runners/shared/src/index.ts
@@ -27,6 +27,16 @@ export {
   type GitHubEvidenceAction,
   type HostEvidenceAction,
 } from './evidence-actions.js';
+export {
+  DEFAULT_SCHEDULE_TASK_CONTEXT_MODE,
+  DEFAULT_TASK_CONTEXT_MODE,
+  DEFAULT_WATCH_CI_CONTEXT_MODE,
+  TASK_CONTEXT_MODES,
+  WATCH_CI_PROMPT_PREFIX,
+  isTaskContextMode,
+  normalizeTaskContextMode,
+  type TaskContextMode,
+} from './task-runtime.js';
 export {
   extractMarkdownImageAttachments,
   extractMediaAttachments,
diff --git a/runners/shared/src/task-runtime.ts b/runners/shared/src/task-runtime.ts
new file mode 100644
index 0000000..cede93f
--- /dev/null
+++ b/runners/shared/src/task-runtime.ts
@@ -0,0 +1,18 @@
+export const TASK_CONTEXT_MODES = ['group', 'isolated'] as const;
+export type TaskContextMode = (typeof TASK_CONTEXT_MODES)[number];
+
+export const DEFAULT_TASK_CONTEXT_MODE: TaskContextMode = 'isolated';
+export const DEFAULT_SCHEDULE_TASK_CONTEXT_MODE: TaskContextMode = 'group';
+export const DEFAULT_WATCH_CI_CONTEXT_MODE: TaskContextMode = 'isolated';
+export const WATCH_CI_PROMPT_PREFIX = '[BACKGROUND CI WATCH]';
+
+export function isTaskContextMode(value: unknown): value is TaskContextMode {
+  return value === 'group' || value === 'isolated';
+}
+
+export function normalizeTaskContextMode(
+  value: unknown,
+  fallback: TaskContextMode = DEFAULT_TASK_CONTEXT_MODE,
+): TaskContextMode {
+  return isTaskContextMode(value) ? value : fallback;
+}
diff --git a/runners/shared/test/task-runtime.test.ts b/runners/shared/test/task-runtime.test.ts
new file mode 100644
index 0000000..1605993
--- /dev/null
+++ b/runners/shared/test/task-runtime.test.ts
@@ -0,0 +1,32 @@
+import { describe, expect, it } from 'vitest';
+
+import {
+  DEFAULT_SCHEDULE_TASK_CONTEXT_MODE,
+  DEFAULT_TASK_CONTEXT_MODE,
+  DEFAULT_WATCH_CI_CONTEXT_MODE,
+  TASK_CONTEXT_MODES,
+  WATCH_CI_PROMPT_PREFIX,
+  isTaskContextMode,
+  normalizeTaskContextMode,
+} from '../src/task-runtime.js';
+
+describe('task runtime constants', () => {
+  it('defines the task context modes and default', () => {
+    expect(TASK_CONTEXT_MODES).toEqual(['group', 'isolated']);
+    expect(DEFAULT_TASK_CONTEXT_MODE).toBe('isolated');
+    expect(DEFAULT_SCHEDULE_TASK_CONTEXT_MODE).toBe('group');
+    expect(DEFAULT_WATCH_CI_CONTEXT_MODE).toBe('isolated');
+  });
+
+  it('normalizes task context modes consistently', () => {
+    expect(isTaskContextMode('group')).toBe(true);
+    expect(isTaskContextMode('isolated')).toBe(true);
+    expect(isTaskContextMode('invalid')).toBe(false);
+    expect(normalizeTaskContextMode('group')).toBe('group');
+    expect(normalizeTaskContextMode('invalid')).toBe('isolated');
+  });
+
+  it('defines the watch CI prompt sentinel', () => {
+    expect(WATCH_CI_PROMPT_PREFIX).toBe('[BACKGROUND CI WATCH]');
+  });
+});
diff --git a/src/db/tasks.ts b/src/db/tasks.ts
index 3129e61..cd513bc 100644
--- a/src/db/tasks.ts
+++ b/src/db/tasks.ts
@@ -1,4 +1,8 @@
 import { Database } from 'bun:sqlite';
+import {
+  DEFAULT_TASK_CONTEXT_MODE,
+  WATCH_CI_PROMPT_PREFIX,
+} from 'ejclaw-runners-shared';
 
 import {
   AgentType,
@@ -70,7 +74,7 @@ export function createTaskInDatabase(
       task.prompt,
       task.schedule_type,
       task.schedule_value,
-      task.context_mode || 'isolated',
+      task.context_mode || DEFAULT_TASK_CONTEXT_MODE,
       task.next_run,
       task.status,
       task.created_at,
@@ -217,10 +221,10 @@ export function hasActiveCiWatcherForChatInDatabase(
   const row = database
     .prepare(
       `SELECT 1 FROM scheduled_tasks
-       WHERE chat_jid = ? AND status = 'active' AND prompt LIKE '[BACKGROUND CI WATCH]%'
+       WHERE chat_jid = ? AND status = 'active' AND prompt LIKE ?
        LIMIT 1`,
     )
-    .get(chatJid);
+    .get(chatJid, `${WATCH_CI_PROMPT_PREFIX}%`);
   return !!row;
 }
 
diff --git a/src/ipc-task-processor/schedule.ts b/src/ipc-task-processor/schedule.ts
index d8074ee..9f649ab 100644
--- a/src/ipc-task-processor/schedule.ts
+++ b/src/ipc-task-processor/schedule.ts
@@ -1,4 +1,5 @@
 import { CronExpressionParser } from 'cron-parser';
+import { normalizeTaskContextMode } from 'ejclaw-runners-shared';
 
 import { createTask, findDuplicateCiWatcher } from '../db.js';
 import { normalizeStoredAgentType } from '../db/room-registration.js';
@@ -49,10 +50,7 @@ export function handleScheduleTask(
   const taskId =
     data.taskId ||
     `task-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
-  const contextMode =
-    data.context_mode === 'group' || data.context_mode === 'isolated'
-      ? data.context_mode
-      : 'isolated';
+  const contextMode = normalizeTaskContextMode(data.context_mode);
   const scheduledAgentType =
     normalizeStoredAgentType(data.agent_type) ??
     target.room.agentType ??
diff --git a/src/message-source.test.ts b/src/message-source.test.ts
index d0aa110..e66504f 100644
--- a/src/message-source.test.ts
+++ b/src/message-source.test.ts
@@ -1,43 +1,39 @@
 import { describe, expect, it } from 'vitest';
 
 import {
-  isBotMessageSourceKind,
+  inferMessageSourceKindFromBotFlag,
   normalizeMessageSourceKind,
   resolveInjectedMessageSourceKind,
 } from './message-source.js';
+import { DEFAULT_MESSAGE_SOURCE_KIND, MESSAGE_SOURCE_KINDS } from './types.js';
 
-describe('message source helpers', () => {
-  it('defaults IPC injected messages to trusted human-equivalent provenance', () => {
+describe('message source kind helpers', () => {
+  it('uses the canonical source kind list', () => {
+    expect(MESSAGE_SOURCE_KINDS).toEqual([
+      'human',
+      'bot',
+      'trusted_external_bot',
+      'ipc_injected_human',
+      'ipc_injected_bot',
+    ]);
+    expect(DEFAULT_MESSAGE_SOURCE_KIND).toBe('human');
+  });
+
+  it('normalizes unknown source kinds to the default', () => {
+    expect(normalizeMessageSourceKind('trusted_external_bot')).toBe(
+      'trusted_external_bot',
+    );
+    expect(normalizeMessageSourceKind('unknown')).toBe('human');
+  });
+
+  it('derives source kinds from legacy and injected inputs', () => {
+    expect(inferMessageSourceKindFromBotFlag(true)).toBe('bot');
+    expect(inferMessageSourceKindFromBotFlag(false)).toBe('human');
     expect(resolveInjectedMessageSourceKind({ treatAsHuman: true })).toBe(
       'trusted_external_bot',
     );
-    expect(
-      isBotMessageSourceKind(
-        resolveInjectedMessageSourceKind({ treatAsHuman: true }),
-      ),
-    ).toBe(false);
-  });
-
-  it('defaults non-human IPC injected messages to bot-equivalent provenance', () => {
     expect(resolveInjectedMessageSourceKind({ treatAsHuman: false })).toBe(
       'ipc_injected_bot',
     );
-    expect(
-      isBotMessageSourceKind(
-        resolveInjectedMessageSourceKind({ treatAsHuman: false }),
-      ),
-    ).toBe(true);
-  });
-
-  it('honors valid explicit source kinds and normalizes invalid values', () => {
-    expect(
-      resolveInjectedMessageSourceKind({
-        treatAsHuman: true,
-        sourceKind: 'ipc_injected_human',
-      }),
-    ).toBe('ipc_injected_human');
-
-    expect(normalizeMessageSourceKind('bot', 'human')).toBe('bot');
-    expect(normalizeMessageSourceKind('not-real', 'human')).toBe('human');
   });
 });
diff --git a/src/message-source.ts b/src/message-source.ts
index 2e36acb..5234434 100644
--- a/src/message-source.ts
+++ b/src/message-source.ts
@@ -1,19 +1,19 @@
-import type { MessageSourceKind } from './types.js';
+import {
+  DEFAULT_MESSAGE_SOURCE_KIND,
+  MESSAGE_SOURCE_KINDS,
+  type MessageSourceKind,
+} from './types.js';
 
-const MESSAGE_SOURCE_KINDS = new Set<MessageSourceKind>([
-  'human',
-  'bot',
-  'trusted_external_bot',
-  'ipc_injected_human',
-  'ipc_injected_bot',
-]);
+const MESSAGE_SOURCE_KIND_SET = new Set<MessageSourceKind>(
+  MESSAGE_SOURCE_KINDS,
+);
 
 export function normalizeMessageSourceKind(
   value: unknown,
-  fallback: MessageSourceKind = 'human',
+  fallback: MessageSourceKind = DEFAULT_MESSAGE_SOURCE_KIND,
 ): MessageSourceKind {
   return typeof value === 'string' &&
-    MESSAGE_SOURCE_KINDS.has(value as MessageSourceKind)
+    MESSAGE_SOURCE_KIND_SET.has(value as MessageSourceKind)
     ? (value as MessageSourceKind)
     : fallback;
 }
@@ -25,7 +25,7 @@ export function isBotMessageSourceKind(kind: MessageSourceKind): boolean {
 export function inferMessageSourceKindFromBotFlag(
   isBotMessage: boolean | number | null | undefined,
 ): MessageSourceKind {
-  return isBotMessage ? 'bot' : 'human';
+  return isBotMessage ? 'bot' : DEFAULT_MESSAGE_SOURCE_KIND;
 }
 
 export function resolveInjectedMessageSourceKind(args: {
diff --git a/src/paired-verdict.ts b/src/paired-verdict.ts
index 0b247f0..c6c71e9 100644
--- a/src/paired-verdict.ts
+++ b/src/paired-verdict.ts
@@ -1,3 +1,5 @@
+import type { ArbiterVerdict } from './types.js';
+
 export type VisibleVerdict =
   | 'step_done'
   | 'task_done'
@@ -7,12 +9,7 @@ export type VisibleVerdict =
   | 'needs_context'
   | 'continue';
 
-export type ArbiterVerdictResult =
-  | 'proceed'
-  | 'revise'
-  | 'reset'
-  | 'escalate'
-  | 'unknown';
+export type ArbiterVerdictResult = ArbiterVerdict | 'unknown';
 
 const VISIBLE_VERDICT_SCAN_LINE_LIMIT = 5;
 
@@ -81,7 +78,7 @@ export function classifyArbiterVerdict(
     const normalized = verdictMatch[1].toLowerCase();
     return normalized === 'continue'
       ? 'proceed'
-      : (normalized as ArbiterVerdictResult);
+      : (normalized as ArbiterVerdict);
   }
   return 'unknown';
 }
diff --git a/src/task-watch-status.ts b/src/task-watch-status.ts
index 347c9f7..d3c55bb 100644
--- a/src/task-watch-status.ts
+++ b/src/task-watch-status.ts
@@ -1,3 +1,5 @@
+import { WATCH_CI_PROMPT_PREFIX } from 'ejclaw-runners-shared';
+
 import { TIMEZONE } from './config.js';
 import type { ScheduledTask } from './types.js';
 import { formatElapsedKorean } from './utils.js';
@@ -8,7 +10,7 @@ export type WatcherStatusPhase =
   | 'retrying'
   | 'completed';
 
-export const WATCH_CI_PREFIX = '[BACKGROUND CI WATCH]';
+export const WATCH_CI_PREFIX = WATCH_CI_PROMPT_PREFIX;
 export const TASK_STATUS_MESSAGE_PREFIX = '\u2063\u2063\u2063';
 export const DEFAULT_WATCH_CI_MAX_DURATION_MS = 24 * 60 * 60 * 1000;
 
diff --git a/src/types.ts b/src/types.ts
index 422f1b4..7caa7ac 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -4,6 +4,7 @@ import {
   normalizePairedRoomRole,
   normalizePairedRoomRoleOrNull,
   type PairedRoomRole,
+  type TaskContextMode,
 } from 'ejclaw-runners-shared';
 import type { VisibleVerdict } from './paired-verdict.js';
 
@@ -208,12 +209,15 @@ export interface RegisteredGroup {
   workDir?: string; // Working directory for the agent (defaults to group folder)
 }
 
-export type MessageSourceKind =
-  | 'human'
-  | 'bot'
-  | 'trusted_external_bot'
-  | 'ipc_injected_human'
-  | 'ipc_injected_bot';
+export const MESSAGE_SOURCE_KINDS = [
+  'human',
+  'bot',
+  'trusted_external_bot',
+  'ipc_injected_human',
+  'ipc_injected_bot',
+] as const;
+export type MessageSourceKind = (typeof MESSAGE_SOURCE_KINDS)[number];
+export const DEFAULT_MESSAGE_SOURCE_KIND: MessageSourceKind = 'human';
 
 export interface NewMessage {
   id: string;
@@ -242,7 +246,7 @@ export interface ScheduledTask {
   prompt: string;
   schedule_type: 'cron' | 'interval' | 'once';
   schedule_value: string;
-  context_mode: 'group' | 'isolated';
+  context_mode: TaskContextMode;
   next_run: string | null;
   last_run: string | null;
   last_result: string | null;
diff --git a/src/web-dashboard-task-routes.ts b/src/web-dashboard-task-routes.ts
index b4b43a8..302ed6c 100644
--- a/src/web-dashboard-task-routes.ts
+++ b/src/web-dashboard-task-routes.ts
@@ -1,4 +1,8 @@
 import { CronExpressionParser } from 'cron-parser';
+import {
+  DEFAULT_TASK_CONTEXT_MODE,
+  isTaskContextMode,
+} from 'ejclaw-runners-shared';
 
 import { TIMEZONE } from './config.js';
 import { isWatchCiTask } from './task-watch-status.js';
@@ -100,10 +104,6 @@ function isScheduleType(
   return value === 'cron' || value === 'interval' || value === 'once';
 }
 
-function isContextMode(value: unknown): value is ScheduledTask['context_mode'] {
-  return value === 'group' || value === 'isolated';
-}
-
 function isAgentType(value: unknown): value is AgentType {
   return value === 'claude-code' || value === 'codex';
 }
@@ -294,9 +294,9 @@ async function handleTaskCreateRoute(
     return jsonResponse({ error: next.error }, { status: 400 });
   }
 
-  const contextMode = isContextMode(body.contextMode)
+  const contextMode = isTaskContextMode(body.contextMode)
     ? body.contextMode
-    : 'isolated';
+    : DEFAULT_TASK_CONTEXT_MODE;
   const agentType = isAgentType(body.agentType)
     ? body.agentType
     : (room.group.agentType ?? 'claude-code');