diff --git a/docs/config-catalog.md b/docs/config-catalog.md
index 91fe7c6497..e346e0114d 100644
--- a/docs/config-catalog.md
+++ b/docs/config-catalog.md
@@ -1279,6 +1279,7 @@ Imported as libraries by other packages; a `cordis.yml` cannot load them.
 
 - `@deepseek-ai/create-sdk` ([`packages/sdk/create-sdk/src/index.ts`](../packages/sdk/create-sdk/src/index.ts))
 - `@deepseek-ai/dsh-acp-snapshot` ([`packages/support/acp-snapshot/src/index.ts`](../packages/support/acp-snapshot/src/index.ts))
+- `@deepseek-ai/dsh-agent-loop-testkit` ([`packages/support/agent-loop-testkit/src/index.ts`](../packages/support/agent-loop-testkit/src/index.ts))
 - `@deepseek-ai/dsh-app-boot` ([`packages/ui/app-boot/src/index.ts`](../packages/ui/app-boot/src/index.ts))
 - `@deepseek-ai/dsh-brand` ([`packages/util/brand/src/index.ts`](../packages/util/brand/src/index.ts))
 - `@deepseek-ai/dsh-helper` ([`packages/sdk/helper/src/index.ts`](../packages/sdk/helper/src/index.ts))
diff --git a/docs/module-graph.md b/docs/module-graph.md
index 82763bdc55..df4e680ee0 100644
--- a/docs/module-graph.md
+++ b/docs/module-graph.md
@@ -86,6 +86,7 @@ flowchart TD
   end
   subgraph group_support["packages/support"]
     pkg_acp_snapshot["acp-snapshot"]
+    pkg_agent_loop_testkit["agent-loop-testkit"]
     pkg_invariants["invariants"]
     pkg_llm_replay["llm-replay"]
     pkg_loader_smoke["loader-smoke"]
@@ -274,6 +275,11 @@ flowchart TD
   pkg_hooks_codex --> pkg_llm
   pkg_hooks_codex --> pkg_session
   pkg_hooks_codex --> pkg_tools
+  pkg_agent_loop_testkit --> pkg_agent
+  pkg_agent_loop_testkit --> pkg_llm
+  pkg_agent_loop_testkit --> pkg_session
+  pkg_agent_loop_testkit --> pkg_system_prompt
+  pkg_agent_loop_testkit --> pkg_tools
   pkg_acp --> pkg_agent
   pkg_acp --> pkg_bash
   pkg_acp --> pkg_llm
@@ -435,6 +441,7 @@ flowchart TD
 | [`tool-todo`](../packages/todo/tool-todo) | `todo` | [`agent`](../packages/core/agent), [`session`](../packages/core/session), [`tools`](../packages/core/tools) |
 | [`tool-cordis`](../packages/cordis/tool-cordis) | `cordis` | [`scope`](../packages/core/scope), [`tools`](../packages/core/tools) |
 | [`hooks-codex`](../packages/hooks/hooks-codex) | `hooks` | [`agent`](../packages/core/agent), [`hook-protocol`](../packages/hooks/hook-protocol), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`tools`](../packages/core/tools) |
+| [`agent-loop-testkit`](../packages/support/agent-loop-testkit) | `support` | [`agent`](../packages/core/agent), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`system-prompt`](../packages/core/system-prompt), [`tools`](../packages/core/tools) |
 | [`acp`](../packages/ui/acp) | `ui` | [`agent`](../packages/core/agent), [`bash`](../packages/bash/bash), [`llm`](../packages/llm/llm), [`permission`](../packages/ui/permission), [`sandbox`](../packages/sandbox/sandbox), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence), [`tools`](../packages/core/tools), [`user-approval`](../packages/ui/user-approval), [`user-interaction`](../packages/ui/user-interaction) |
 | [`tool-ask-user`](../packages/ui/tool-ask-user) | `ui` | [`agent`](../packages/core/agent), [`tools`](../packages/core/tools), [`user-interaction`](../packages/ui/user-interaction) |
 | [`repeat-tool-guard`](../packages/guard/repeat-tool-guard) | `guard` | [`agent`](../packages/core/agent), [`tools`](../packages/core/tools) |
diff --git a/examples/coding-agent/tests/harness.ts b/examples/coding-agent/tests/harness.ts
index dd0bc42a1b..22c8c3f662 100644
--- a/examples/coding-agent/tests/harness.ts
+++ b/examples/coding-agent/tests/harness.ts
@@ -1,11 +1,7 @@
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
 import type { SessionEvent } from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry from '@deepseek-ai/dsh-agent'
 import AgentLoop, { ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import { LocalBashExecutor } from '@deepseek-ai/dsh-bash-local'
 import * as ToolBash from '@deepseek-ai/dsh-tool-bash'
 import * as ToolTodo from '@deepseek-ai/dsh-tool-todo'
@@ -50,11 +46,9 @@ export interface CodingHarnessOptions {
 
 export async function codingHarness(workdir: string, options: CodingHarnessOptions = {}): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt, { persona: options.persona ?? '' })
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx, {
+    systemPrompt: { persona: options.persona ?? '' },
+  })
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(LlmDeepSeek, { models: ['deepseek-v4-flash'] })
   await ctx.plugin(LocalBashExecutor, { cwd: workdir, timeoutMs: 30_000 })
diff --git a/examples/cordis-agent/tests/harness.ts b/examples/cordis-agent/tests/harness.ts
index 78e5b0bb93..260a68bfbb 100644
--- a/examples/cordis-agent/tests/harness.ts
+++ b/examples/cordis-agent/tests/harness.ts
@@ -1,10 +1,6 @@
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry from '@deepseek-ai/dsh-agent'
 import AgentLoop, { ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as LlmDeepSeek from '@deepseek-ai/dsh-llm-deepseek'
 import * as ToolCordis from '@deepseek-ai/dsh-tool-cordis'
 
@@ -23,11 +19,9 @@ const PERSONA = 'You are cordis-agent, a self-referential harness demo. '
 
 export async function cordisHarness(): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt, { persona: PERSONA })
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx, {
+    systemPrompt: { persona: PERSONA },
+  })
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(LlmDeepSeek, { models: ['deepseek-v4-flash'] })
   await ctx.plugin(ToolCordis)
diff --git a/packages/README.md b/packages/README.md
index 8f1bf3dde2..a3e0b1ac0a 100644
--- a/packages/README.md
+++ b/packages/README.md
@@ -31,7 +31,7 @@ Packages live at `packages/<group>/<pkg>/`; groups are containers, while names r
 | [`sdk/`](sdk/README.md) | Project SDK tooling | Product — stable surface |
 | [`ui/`](ui/README.md) | Editor/client integration surfaces: ACP bridge, JSON-RPC SDK server, user-approval/user-interaction seams, ask-user tool | Product — stable surface |
 | [`examples/`](examples/README.md) | Demo bundles (agent-spine + stdio/ACP/JSON-RPC bins) the leaves load | Support — example infra |
-| [`support/`](support/README.md) | Support infrastructure (invariants, replay, Loader smokes) | Support — lower compatibility expectations |
+| [`support/`](support/README.md) | Support infrastructure (testkits, invariants, replay, Loader smokes) | Support — lower compatibility expectations |
 | [`util/`](util/README.md) | Low-level zero-dependency utilities shared across groups (the `Branded<B>` primitive) | Support — small, stable, harness-dep-free |
 
 Groups distinguish product API from support infrastructure. New packages join an existing group; a new group updates its README and this table.
diff --git a/packages/bash/tool-bash/package.json b/packages/bash/tool-bash/package.json
index 035b16aeec..c8d082f46a 100644
--- a/packages/bash/tool-bash/package.json
+++ b/packages/bash/tool-bash/package.json
@@ -38,6 +38,7 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-user-approval": "workspace:^",
     "@deepseek-ai/dsh-bash": "workspace:^",
     "@deepseek-ai/dsh-bash-local": "workspace:^",
diff --git a/packages/bash/tool-bash/tests/integration.spec.ts b/packages/bash/tool-bash/tests/integration.spec.ts
index 238176b8a6..0a2a1ba883 100644
--- a/packages/bash/tool-bash/tests/integration.spec.ts
+++ b/packages/bash/tool-bash/tests/integration.spec.ts
@@ -1,12 +1,9 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
 import type { SessionEvent } from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop, { ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import TaskService from '@deepseek-ai/dsh-tasks'
 import * as ToolTasks from '@deepseek-ai/dsh-tool-tasks'
 import { LocalBashExecutor } from '@deepseek-ai/dsh-bash-local'
@@ -21,11 +18,7 @@ import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent
  */
 async function harness(adapter: MockAdapter) {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(TaskService)
   await ctx.plugin(ToolTasks)
diff --git a/packages/compact/compact-basic/package.json b/packages/compact/compact-basic/package.json
index 32852a060f..fae0af5c62 100644
--- a/packages/compact/compact-basic/package.json
+++ b/packages/compact/compact-basic/package.json
@@ -31,11 +31,11 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-compact": "workspace:^",
     "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
-    "@deepseek-ai/dsh-system-prompt": "workspace:^",
     "@deepseek-ai/dsh-tools": "workspace:^",
     "cordis": "^4.0.0-rc.7"
   }
diff --git a/packages/compact/compact-basic/tests/compact-loop-repro.spec.ts b/packages/compact/compact-basic/tests/compact-loop-repro.spec.ts
index dbf8a3b737..f2d1a60ad8 100644
--- a/packages/compact/compact-basic/tests/compact-loop-repro.spec.ts
+++ b/packages/compact/compact-basic/tests/compact-loop-repro.spec.ts
@@ -1,14 +1,12 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
 import type { ContentBlock, GenerateOptions, StreamChunk } from '@deepseek-ai/dsh-llm'
 import { CallId, LlmAdapter } from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
 import { isToolPairingBalanced } from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry, { defineTool } from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import { defineTool } from '@deepseek-ai/dsh-tools'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop, { ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as Invariants from '@deepseek-ai/dsh-invariants'
 import { BasicCompactService } from '@deepseek-ai/dsh-compact-basic'
 import type { SurfaceEvent } from '@deepseek-ai/dsh-session'
@@ -60,12 +58,8 @@ class StepwiseToolAdapter extends LlmAdapter {
 
 async function harness(toolSteps: number): Promise<{ ctx: Context; compact: ReproCompactService }> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(Invariants)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
   await ctx.plugin(AgentLoop, { agents: [] })
   ctx.llm.registerAdapter(['mock'], new StepwiseToolAdapter(toolSteps))
   ctx.tools.register(defineTool({
diff --git a/packages/context/time-context/package.json b/packages/context/time-context/package.json
index f319c7a5b1..906adf854e 100644
--- a/packages/context/time-context/package.json
+++ b/packages/context/time-context/package.json
@@ -32,6 +32,7 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
     "@deepseek-ai/dsh-system-prompt": "workspace:^",
diff --git a/packages/context/time-context/tests/time-context.spec.ts b/packages/context/time-context/tests/time-context.spec.ts
index 562b002b68..92637e8277 100644
--- a/packages/context/time-context/tests/time-context.spec.ts
+++ b/packages/context/time-context/tests/time-context.spec.ts
@@ -1,14 +1,15 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { Context } from 'cordis'
 import Loader from '@cordisjs/plugin-loader'
-import LlmService, { CallId, LlmAdapter } from '@deepseek-ai/dsh-llm'
+import { CallId, LlmAdapter } from '@deepseek-ai/dsh-llm'
 import type { GenerateOptions, StreamChunk } from '@deepseek-ai/dsh-llm'
-import SessionStore, { Session, SessionId, foldRequestHeader } from '@deepseek-ai/dsh-session'
+import { Session, SessionId, foldRequestHeader } from '@deepseek-ai/dsh-session'
 import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import type { Agent } from '@deepseek-ai/dsh-agent'
-import ToolRegistry, { defineTool } from '@deepseek-ai/dsh-tools'
+import { defineTool } from '@deepseek-ai/dsh-tools'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as timeContext from '@deepseek-ai/dsh-time-context'
 import type { Config } from '@deepseek-ai/dsh-time-context'
 
@@ -89,11 +90,7 @@ class ScriptedAdapter extends LlmAdapter {
 
 async function loopHarness(adapter: ScriptedAdapter, config: Config = {}): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(timeContext, config)
   ctx.llm.registerAdapter(['mock'], adapter)
diff --git a/packages/cordis/tool-cordis/package.json b/packages/cordis/tool-cordis/package.json
index fd9c35e48e..e13de3e58b 100644
--- a/packages/cordis/tool-cordis/package.json
+++ b/packages/cordis/tool-cordis/package.json
@@ -33,6 +33,7 @@
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-scope": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
     "@deepseek-ai/dsh-system-prompt": "workspace:^",
diff --git a/packages/cordis/tool-cordis/tests/integration.spec.ts b/packages/cordis/tool-cordis/tests/integration.spec.ts
index 94331df7c0..8892dd47e5 100644
--- a/packages/cordis/tool-cordis/tests/integration.spec.ts
+++ b/packages/cordis/tool-cordis/tests/integration.spec.ts
@@ -1,11 +1,8 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop, { ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as ToolCordis from '../src/index.ts'
 import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
 import { REVERSE_TOOL_CODE } from './helpers.ts'
@@ -20,11 +17,7 @@ import { REVERSE_TOOL_CODE } from './helpers.ts'
 
 async function harness(adapter: MockAdapter): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(ToolCordis)
   ctx.llm.registerAdapter(['mock'], adapter)
diff --git a/packages/fs/tool-fs/package.json b/packages/fs/tool-fs/package.json
index c21c806e98..f9ef3136bf 100644
--- a/packages/fs/tool-fs/package.json
+++ b/packages/fs/tool-fs/package.json
@@ -36,6 +36,7 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-fs-policy": "workspace:^",
     "@deepseek-ai/dsh-fs": "workspace:^",
     "@deepseek-ai/dsh-fs-local": "workspace:^",
diff --git a/packages/fs/tool-fs/tests/harness.ts b/packages/fs/tool-fs/tests/harness.ts
index 0487962922..3666447ad9 100644
--- a/packages/fs/tool-fs/tests/harness.ts
+++ b/packages/fs/tool-fs/tests/harness.ts
@@ -1,10 +1,7 @@
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { type Agent } from '@deepseek-ai/dsh-agent'
+import type { Agent } from '@deepseek-ai/dsh-agent'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import LocalFileSystem from '@deepseek-ai/dsh-fs-local'
 import * as FsPolicy from '@deepseek-ai/dsh-fs-policy'
 import * as ToolFs from '@deepseek-ai/dsh-tool-fs'
@@ -17,11 +14,7 @@ import * as LlmDeepSeek from '@deepseek-ai/dsh-llm-deepseek'
  */
 export async function fsHarness(fsCwd: string, persona = ''): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt, { persona })
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx, { systemPrompt: { persona } })
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(LlmDeepSeek, { models: ['deepseek-v4-flash'] })
   await ctx.plugin(LocalFileSystem, { cwd: fsCwd })
diff --git a/packages/guard/repeat-tool-guard/package.json b/packages/guard/repeat-tool-guard/package.json
index 0cc99b6976..92d49c548f 100644
--- a/packages/guard/repeat-tool-guard/package.json
+++ b/packages/guard/repeat-tool-guard/package.json
@@ -32,9 +32,9 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
-    "@deepseek-ai/dsh-system-prompt": "workspace:^",
     "@deepseek-ai/dsh-tools": "workspace:^",
     "cordis": "^4.0.0-rc.7"
   }
diff --git a/packages/guard/repeat-tool-guard/tests/repeat-tool-guard.spec.ts b/packages/guard/repeat-tool-guard/tests/repeat-tool-guard.spec.ts
index 565f1076b5..81fe63aaca 100644
--- a/packages/guard/repeat-tool-guard/tests/repeat-tool-guard.spec.ts
+++ b/packages/guard/repeat-tool-guard/tests/repeat-tool-guard.spec.ts
@@ -1,11 +1,11 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService, { CallId } from '@deepseek-ai/dsh-llm'
-import SessionStore, { type SessionEvent } from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry, { defineTool } from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import { CallId } from '@deepseek-ai/dsh-llm'
+import type { SessionEvent } from '@deepseek-ai/dsh-session'
+import { defineTool } from '@deepseek-ai/dsh-tools'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop, { type ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as RepeatToolGuard from '@deepseek-ai/dsh-repeat-tool-guard'
 import type { Config } from '@deepseek-ai/dsh-repeat-tool-guard'
 import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
@@ -21,11 +21,7 @@ import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent
 /** Boot the core spine + the guard; the caller registers adapters and extra listeners. */
 async function harness(config: Config = {}): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(RepeatToolGuard, config)
   ctx.tools.register(defineTool({ name: 'probe', description: 'p', parameters: {}, async execute() { return [{ type: 'text', text: 'ok' }] } }))
@@ -363,11 +359,7 @@ describe('fold onto the downstream decision', () => {
 describe('config validation fails loud', () => {
   async function spine(): Promise<Context> {
     const ctx = new Context()
-    await ctx.plugin(LlmService)
-    await ctx.plugin(SessionStore)
-    await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry)
-    await ctx.plugin(AgentRegistry)
+    await mountAgentLoopTestDependencies(ctx)
     await ctx.plugin(AgentLoop, { agents: [] })
     return ctx
   }
diff --git a/packages/hooks/hooks-claude/package.json b/packages/hooks/hooks-claude/package.json
index 21f08965d8..abb68a061e 100644
--- a/packages/hooks/hooks-claude/package.json
+++ b/packages/hooks/hooks-claude/package.json
@@ -36,13 +36,13 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-bash": "workspace:^",
     "@deepseek-ai/dsh-bash-local": "workspace:^",
     "@deepseek-ai/dsh-hook-protocol": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
     "@deepseek-ai/dsh-subagent": "workspace:^",
-    "@deepseek-ai/dsh-system-prompt": "workspace:^",
     "@deepseek-ai/dsh-tools": "workspace:^",
     "cordis": "^4.0.0-rc.7"
   }
diff --git a/packages/hooks/hooks-claude/tests/bridge.spec.ts b/packages/hooks/hooks-claude/tests/bridge.spec.ts
index 506d613c73..6d9e89d5ed 100644
--- a/packages/hooks/hooks-claude/tests/bridge.spec.ts
+++ b/packages/hooks/hooks-claude/tests/bridge.spec.ts
@@ -4,12 +4,11 @@ import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { Context, type Fiber } from 'cordis'
 import Loader from '@cordisjs/plugin-loader'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore, { type SessionEvent } from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry, { defineTool } from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import type { SessionEvent } from '@deepseek-ai/dsh-session'
+import { defineTool } from '@deepseek-ai/dsh-tools'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop, { type ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import { LocalBashExecutor } from '@deepseek-ai/dsh-bash-local'
 import * as HooksClaude from '@deepseek-ai/dsh-hooks-claude'
 import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
@@ -42,11 +41,7 @@ async function harness(configDir: string, adapter: MockAdapter): Promise<Context
 /** {@link harness}, also exposing the bridge's fiber for tests that dispose it. */
 async function harnessWithFiber(configDir: string, adapter: MockAdapter): Promise<{ ctx: Context; hooks: Fiber }> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
   const hooks = await ctx.plugin(HooksClaude, { configPath: join(configDir, 'hooks.json') })
@@ -337,11 +332,7 @@ describe('hooks-claude bridge — load resilience', () => {
   it('a missing config file registers no hooks and does not crash the loop', async () => {
     const adapter = new MockAdapter([textResponse('fine')])
     const ctx = new Context()
-    await ctx.plugin(LlmService)
-    await ctx.plugin(SessionStore)
-    await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry)
-    await ctx.plugin(AgentRegistry)
+    await mountAgentLoopTestDependencies(ctx)
     await ctx.plugin(AgentLoop, { agents: [] })
     await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
     await ctx.plugin(HooksClaude, { configPath: '/nonexistent/hooks.json' })
@@ -359,11 +350,7 @@ describe('hooks-claude bridge — load resilience', () => {
     const dir = writeConfig({ UserPromptSubmit: [{ hooks: [{ type: 'command', command: 'exit 2' }] }] })
     const adapter = new MockAdapter([textResponse('ok')])
     const ctx = new Context()
-    await ctx.plugin(LlmService)
-    await ctx.plugin(SessionStore)
-    await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry)
-    await ctx.plugin(AgentRegistry)
+    await mountAgentLoopTestDependencies(ctx)
     await ctx.plugin(AgentLoop, { agents: [] })
     await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
     const fiber = await ctx.plugin(HooksClaude, { configPath: join(dir, 'hooks.json') })
diff --git a/packages/hooks/hooks-claude/tests/coverage.spec.ts b/packages/hooks/hooks-claude/tests/coverage.spec.ts
index f376708688..5fb975b3dd 100644
--- a/packages/hooks/hooks-claude/tests/coverage.spec.ts
+++ b/packages/hooks/hooks-claude/tests/coverage.spec.ts
@@ -3,12 +3,11 @@ import { mkdtempSync, rmSync, writeFileSync, chmodSync, existsSync } from 'node:
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore, { type SessionEvent } from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry, { defineTool } from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import type { SessionEvent } from '@deepseek-ai/dsh-session'
+import { defineTool } from '@deepseek-ai/dsh-tools'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop, { type ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import { LocalBashExecutor } from '@deepseek-ai/dsh-bash-local'
 import * as HooksClaude from '@deepseek-ai/dsh-hooks-claude'
 import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
@@ -30,11 +29,7 @@ function hooks(d: string, h: unknown): string {
 type HarnessOpts = { pluginRoot?: string; projectDir?: string; stderrSummaryMaxChars?: number }
 async function harness(configPath: string, adapter: MockAdapter, opts: HarnessOpts = {}): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
   await ctx.plugin(HooksClaude, { configPath, ...opts })
@@ -329,11 +324,7 @@ describe('hooks-claude coverage — schema-bypass apply + unspawnable hook', ()
     hooks(d, { UserPromptSubmit: [{ hooks: [{ type: 'command', command: s }] }] })
     const adapter = new MockAdapter([textResponse('ok')])
     const ctx = new Context()
-    await ctx.plugin(LlmService)
-    await ctx.plugin(SessionStore)
-    await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry)
-    await ctx.plugin(AgentRegistry)
+    await mountAgentLoopTestDependencies(ctx)
     await ctx.plugin(AgentLoop, { agents: [] })
     await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
     // Direct apply with only configPath — bypasses schemastery's defaults, so
@@ -594,11 +585,7 @@ describe('hooks-claude coverage — hook runs in the session cwd, not the server
     hooks(serverDir, { PreToolUse: [{ hooks: [{ type: 'command', command: 'pwd > where' }] }] })
     const adapter = new MockAdapter([toolCallResponse('c1', 'echo', {}), textResponse('done')])
     const ctx = new Context()
-    await ctx.plugin(LlmService)
-    await ctx.plugin(SessionStore)
-    await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry)
-    await ctx.plugin(AgentRegistry)
+    await mountAgentLoopTestDependencies(ctx)
     await ctx.plugin(AgentLoop, { agents: [] })
     // Executor default cwd = serverDir (deliberately NOT the session cwd).
     await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000, cwd: serverDir })
@@ -627,11 +614,7 @@ describe('hooks-claude coverage — hook runs in the session cwd, not the server
     const marker = join(childDir, 'stopwhere')
     hooks(serverDir, { SubagentStop: [{ hooks: [{ type: 'command', command: 'pwd > stopwhere' }] }] })
     const ctx = new Context()
-    await ctx.plugin(LlmService)
-    await ctx.plugin(SessionStore)
-    await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry)
-    await ctx.plugin(AgentRegistry)
+    await mountAgentLoopTestDependencies(ctx)
     await ctx.plugin(AgentLoop, { agents: [] })
     // Executor default cwd = serverDir (deliberately NOT the child session cwd).
     await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000, cwd: serverDir })
diff --git a/packages/hooks/hooks-codex/package.json b/packages/hooks/hooks-codex/package.json
index fe667b0302..a481162a11 100644
--- a/packages/hooks/hooks-codex/package.json
+++ b/packages/hooks/hooks-codex/package.json
@@ -35,12 +35,12 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-bash": "workspace:^",
     "@deepseek-ai/dsh-bash-local": "workspace:^",
     "@deepseek-ai/dsh-hook-protocol": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
-    "@deepseek-ai/dsh-system-prompt": "workspace:^",
     "@deepseek-ai/dsh-tools": "workspace:^",
     "cordis": "^4.0.0-rc.7"
   }
diff --git a/packages/hooks/hooks-codex/tests/bridge.spec.ts b/packages/hooks/hooks-codex/tests/bridge.spec.ts
index d4a5797b96..72e3f45184 100644
--- a/packages/hooks/hooks-codex/tests/bridge.spec.ts
+++ b/packages/hooks/hooks-codex/tests/bridge.spec.ts
@@ -4,12 +4,11 @@ import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { Context } from 'cordis'
 import Loader from '@cordisjs/plugin-loader'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore, { type SessionEvent } from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry, { defineTool } from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import type { SessionEvent } from '@deepseek-ai/dsh-session'
+import { defineTool } from '@deepseek-ai/dsh-tools'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop, { type ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import { LocalBashExecutor } from '@deepseek-ai/dsh-bash-local'
 import * as HooksCodex from '@deepseek-ai/dsh-hooks-codex'
 import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
@@ -40,11 +39,7 @@ function writeHooks(dir: string, hooks: unknown): void {
 
 async function harness(dir: string, adapter: MockAdapter): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
   await ctx.plugin(HooksCodex, { configPath: join(dir, 'hooks.json'), model: 'test-model' })
@@ -141,11 +136,7 @@ describe('hooks-codex bridge', () => {
     writeHooks(dir, { UserPromptSubmit: [{ hooks: [{ type: 'command', command: deny }] }] })
     const adapter = new MockAdapter([textResponse('ok')])
     const ctx = new Context()
-    await ctx.plugin(LlmService)
-    await ctx.plugin(SessionStore)
-    await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry)
-    await ctx.plugin(AgentRegistry)
+    await mountAgentLoopTestDependencies(ctx)
     await ctx.plugin(AgentLoop, { agents: [] })
     await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
     const fiber = await ctx.plugin(HooksCodex, { configPath: join(dir, 'hooks.json'), model: 'm' })
@@ -167,11 +158,7 @@ describe('hooks-codex bridge', () => {
     const slow = script(dir, 'slow.sh', `#!/usr/bin/env bash\necho $$ > "${pidFile}"\ntouch "${marker}"\nsleep 30\n`)
     writeHooks(dir, { SessionStart: [{ hooks: [{ type: 'command', command: slow }] }] })
     const ctx = new Context()
-    await ctx.plugin(LlmService)
-    await ctx.plugin(SessionStore)
-    await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry)
-    await ctx.plugin(AgentRegistry)
+    await mountAgentLoopTestDependencies(ctx)
     await ctx.plugin(AgentLoop, { agents: [] })
     await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
     const fiber = await ctx.plugin(HooksCodex, { configPath: join(dir, 'hooks.json'), model: 'm' })
diff --git a/packages/hooks/hooks-codex/tests/coverage.spec.ts b/packages/hooks/hooks-codex/tests/coverage.spec.ts
index c287d86b23..6d2ac699eb 100644
--- a/packages/hooks/hooks-codex/tests/coverage.spec.ts
+++ b/packages/hooks/hooks-codex/tests/coverage.spec.ts
@@ -3,12 +3,11 @@ import { mkdtempSync, rmSync, writeFileSync, chmodSync, existsSync, readFileSync
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore, { type SessionEvent } from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry, { defineTool } from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import type { SessionEvent } from '@deepseek-ai/dsh-session'
+import { defineTool } from '@deepseek-ai/dsh-tools'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop, { type ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import { LocalBashExecutor } from '@deepseek-ai/dsh-bash-local'
 import * as HooksCodex from '@deepseek-ai/dsh-hooks-codex'
 import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
@@ -25,8 +24,8 @@ function hooks(d: string, h: unknown): string {
 
 async function harness(configPath: string, adapter: MockAdapter, opts: { stderrSummaryMaxChars?: number } = {}): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService); await ctx.plugin(SessionStore); await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry); await ctx.plugin(AgentRegistry); await ctx.plugin(AgentLoop, { agents: [] })
+  await mountAgentLoopTestDependencies(ctx)
+  await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
   await ctx.plugin(HooksCodex, { configPath, model: 'm', ...opts })
   ctx.llm.registerAdapter(['mock'], adapter)
@@ -238,8 +237,8 @@ describe('hooks-codex coverage — decision mapping paths', () => {
     const warn = vi.fn()
     const adapter = new MockAdapter([textResponse('ok')])
     const ctx = new Context()
-    await ctx.plugin(LlmService); await ctx.plugin(SessionStore); await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry); await ctx.plugin(AgentRegistry); await ctx.plugin(AgentLoop, { agents: [] })
+    await mountAgentLoopTestDependencies(ctx)
+    await ctx.plugin(AgentLoop, { agents: [] })
     await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
     ctx.logger.warn = warn as never
     // Direct apply (schema bypass) → the `model ?? ''` fallback is exercised.
@@ -543,8 +542,8 @@ describe('hooks-codex coverage — decision mapping paths', () => {
     hooks(serverDir, { PreToolUse: [{ hooks: [{ type: 'command', command: 'pwd > where' }] }] })
     const adapter = new MockAdapter([toolCallResponse('c1', 'Bash', { command: 'x' }), textResponse('done')])
     const ctx = new Context()
-    await ctx.plugin(LlmService); await ctx.plugin(SessionStore); await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry); await ctx.plugin(AgentRegistry); await ctx.plugin(AgentLoop, { agents: [] })
+    await mountAgentLoopTestDependencies(ctx)
+    await ctx.plugin(AgentLoop, { agents: [] })
     await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000, cwd: serverDir })
     await ctx.plugin(HooksCodex, { configPath: join(serverDir, 'hooks.json'), model: 'm' })
     ctx.llm.registerAdapter(['mock'], adapter)
diff --git a/packages/subagent/subagent-fork/package.json b/packages/subagent/subagent-fork/package.json
index 8794884518..63f548d217 100644
--- a/packages/subagent/subagent-fork/package.json
+++ b/packages/subagent/subagent-fork/package.json
@@ -34,14 +34,13 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
     "@deepseek-ai/dsh-subagent": "workspace:^",
     "@deepseek-ai/dsh-subagent-inprocess": "workspace:^",
     "@deepseek-ai/dsh-subagent-spawn": "workspace:^",
-    "@deepseek-ai/dsh-system-prompt": "workspace:^",
-    "@deepseek-ai/dsh-tools": "workspace:^",
     "@cordisjs/plugin-loader": "^1.0.0-rc.5",
     "cordis": "^4.0.0-rc.7"
   }
diff --git a/packages/subagent/subagent-fork/tests/multi-subagent.spec.ts b/packages/subagent/subagent-fork/tests/multi-subagent.spec.ts
index 8060a77fd4..110c4f83e4 100644
--- a/packages/subagent/subagent-fork/tests/multi-subagent.spec.ts
+++ b/packages/subagent/subagent-fork/tests/multi-subagent.spec.ts
@@ -1,11 +1,8 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as Invariants from '@deepseek-ai/dsh-invariants'
 import SubagentService, { type SubagentStartRequest } from '@deepseek-ai/dsh-subagent'
 import * as Spawn from '@deepseek-ai/dsh-subagent-spawn'
@@ -26,11 +23,7 @@ function start(ctx: Context, provider: string, request: Omit<SubagentStartReques
  */
 async function setup(script: Script) {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(Invariants)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(SubagentService)
diff --git a/packages/subagent/subagent-fork/tests/subagent-fork.spec.ts b/packages/subagent/subagent-fork/tests/subagent-fork.spec.ts
index b5e129e54f..59a148d779 100644
--- a/packages/subagent/subagent-fork/tests/subagent-fork.spec.ts
+++ b/packages/subagent/subagent-fork/tests/subagent-fork.spec.ts
@@ -1,12 +1,9 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
 import Loader from '@cordisjs/plugin-loader'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
 import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as Invariants from '@deepseek-ai/dsh-invariants'
 import SubagentService, { type SubagentStartRequest } from '@deepseek-ai/dsh-subagent'
 import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
@@ -33,11 +30,7 @@ const emptyStop: StreamChunk[] = [{ type: 'finish', reason: { kind: 'stop' } }]
  */
 async function setup(script: Script) {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(Invariants)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(SubagentService)
diff --git a/packages/subagent/subagent-inprocess/package.json b/packages/subagent/subagent-inprocess/package.json
index aa80dcac3e..b9397e300c 100644
--- a/packages/subagent/subagent-inprocess/package.json
+++ b/packages/subagent/subagent-inprocess/package.json
@@ -33,6 +33,7 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
diff --git a/packages/subagent/subagent-inprocess/tests/structured.spec.ts b/packages/subagent/subagent-inprocess/tests/structured.spec.ts
index a2c55995c2..06d39d5d65 100644
--- a/packages/subagent/subagent-inprocess/tests/structured.spec.ts
+++ b/packages/subagent/subagent-inprocess/tests/structured.spec.ts
@@ -1,12 +1,10 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService, { CallId, type ContentBlock, type GenerateOptions } from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import { CallId, type ContentBlock, type GenerateOptions } from '@deepseek-ai/dsh-llm'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import type { ContinuationDecision } from '@deepseek-ai/dsh-agent'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as Invariants from '@deepseek-ai/dsh-invariants'
 import SubagentService, { type SubagentStartRequest } from '@deepseek-ai/dsh-subagent'
 import type { Config as ToolConfig, StructuredOutputSchema } from '@deepseek-ai/dsh-tools'
@@ -43,10 +41,9 @@ const SCHEMA: StructuredOutputSchema = {
 async function setup(script: Script, options: SetupOptions = {}) {
   const ctx = new Context()
   const adapter = new MockAdapter(script)
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry, { mode: options.toolMode ?? 'native' })
+  await mountAgentLoopTestDependencies(ctx, {
+    tools: { mode: options.toolMode ?? 'native' },
+  })
   if (options.toolMode === 'code' || options.toolMode === 'both') {
     ctx.provide('codeRuntime', {
       language: 'typescript',
@@ -54,7 +51,6 @@ async function setup(script: Script, options: SetupOptions = {}) {
       run: options.codeRun ?? (() => Promise.resolve({ logs: [] })),
     } as never)
   }
-  await ctx.plugin(AgentRegistry)
   await ctx.plugin(Invariants)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(SubagentService)
diff --git a/packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts b/packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts
index 0005246523..e7d856e112 100644
--- a/packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts
+++ b/packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts
@@ -1,11 +1,8 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId, type Agent } from '@deepseek-ai/dsh-agent'
+import { AgentId, type Agent } from '@deepseek-ai/dsh-agent'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as Invariants from '@deepseek-ai/dsh-invariants'
 import SubagentService from '@deepseek-ai/dsh-subagent'
 import { MockAdapter, textResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
@@ -15,11 +12,7 @@ type Script = ConstructorParameters<typeof MockAdapter>[0]
 
 async function setup(script: Script) {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(Invariants)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(SubagentService)
diff --git a/packages/subagent/subagent-spawn/package.json b/packages/subagent/subagent-spawn/package.json
index f2500a4a56..1a986e69aa 100644
--- a/packages/subagent/subagent-spawn/package.json
+++ b/packages/subagent/subagent-spawn/package.json
@@ -32,6 +32,7 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-bash-local": "workspace:^",
     "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
@@ -39,10 +40,8 @@
     "@deepseek-ai/dsh-session": "workspace:^",
     "@deepseek-ai/dsh-subagent": "workspace:^",
     "@deepseek-ai/dsh-subagent-inprocess": "workspace:^",
-    "@deepseek-ai/dsh-system-prompt": "workspace:^",
     "@deepseek-ai/dsh-tool-bash": "workspace:^",
     "@deepseek-ai/dsh-tool-subagent": "workspace:^",
-    "@deepseek-ai/dsh-tools": "workspace:^",
     "@cordisjs/plugin-loader": "^1.0.0-rc.5",
     "cordis": "^4.0.0-rc.7"
   }
diff --git a/packages/subagent/subagent-spawn/tests/harness.ts b/packages/subagent/subagent-spawn/tests/harness.ts
index e4ee2e6ab7..bb0b49fbcb 100644
--- a/packages/subagent/subagent-spawn/tests/harness.ts
+++ b/packages/subagent/subagent-spawn/tests/harness.ts
@@ -1,10 +1,7 @@
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { type Agent } from '@deepseek-ai/dsh-agent'
+import type { Agent } from '@deepseek-ai/dsh-agent'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import { LocalBashExecutor } from '@deepseek-ai/dsh-bash-local'
 import * as ToolBash from '@deepseek-ai/dsh-tool-bash'
 import * as LlmDeepSeek from '@deepseek-ai/dsh-llm-deepseek'
@@ -21,15 +18,13 @@ import * as ToolSubagent from '@deepseek-ai/dsh-tool-subagent'
  */
 export async function spawnHarness(workdir: string): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
   // This harness installs only the global default persona, so both parent and
   // spawned children render it. It stays neutral for both roles; the
   // delegation nudge lives in the e2e's user prompt and the subagent tool's
   // own description.
-  await ctx.plugin(SystemPrompt, { persona: 'You are a coding agent. Report only when the requested work is done.' })
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx, {
+    systemPrompt: { persona: 'You are a coding agent. Report only when the requested work is done.' },
+  })
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(LlmDeepSeek, { models: ['deepseek-v4-flash'] })
   await ctx.plugin(LocalBashExecutor, { cwd: workdir, timeoutMs: 30_000 })
diff --git a/packages/subagent/subagent-spawn/tests/subagent-spawn.spec.ts b/packages/subagent/subagent-spawn/tests/subagent-spawn.spec.ts
index 43ec8ee1ac..3862f110c5 100644
--- a/packages/subagent/subagent-spawn/tests/subagent-spawn.spec.ts
+++ b/packages/subagent/subagent-spawn/tests/subagent-spawn.spec.ts
@@ -1,13 +1,10 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
 import Loader from '@cordisjs/plugin-loader'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
 import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
 import { SessionId } from '@deepseek-ai/dsh-session'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as Invariants from '@deepseek-ai/dsh-invariants'
 import SubagentService, { type SubagentStartRequest } from '@deepseek-ai/dsh-subagent'
 import { MockAdapter, maxTokensResponse, textResponse, toolCallResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
@@ -26,11 +23,7 @@ type Script = ConstructorParameters<typeof MockAdapter>[0]
 async function setup(script: Script) {
   const ctx = new Context()
   const adapter = new MockAdapter(script)
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(Invariants)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(SubagentService)
@@ -303,11 +296,7 @@ describe('dsh-subagent-spawn', () => {
     // Rebuild the stack by hand so we hold the backend's fiber.
     const ctx = new Context()
     const adapter = new MockAdapter(['hang'])
-    await ctx.plugin(LlmService)
-    await ctx.plugin(SessionStore)
-    await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry)
-    await ctx.plugin(AgentRegistry)
+    await mountAgentLoopTestDependencies(ctx)
     await ctx.plugin(Invariants)
     await ctx.plugin(AgentLoop, { agents: [] })
     await ctx.plugin(SubagentService)
@@ -336,11 +325,7 @@ describe('dsh-subagent-spawn', () => {
 
   it('a start racing an already-unloading backend cannot begin child creation', async () => {
     const ctx = new Context()
-    await ctx.plugin(LlmService)
-    await ctx.plugin(SessionStore)
-    await ctx.plugin(SystemPrompt)
-    await ctx.plugin(ToolRegistry)
-    await ctx.plugin(AgentRegistry)
+    await mountAgentLoopTestDependencies(ctx)
     await ctx.plugin(AgentLoop, { agents: [] })
     await ctx.plugin(SubagentService)
     const fiber = await ctx.plugin(spawn, { providerName: 'spawn' })
diff --git a/packages/support/README.md b/packages/support/README.md
index d1bb1883ed..a85fffcdac 100644
--- a/packages/support/README.md
+++ b/packages/support/README.md
@@ -5,9 +5,10 @@ Packages that exist to serve development, testing, and the examples rather than
 | Package | Role | ctx key |
 |---|---|---|
 | `acp-snapshot/` | ACP snapshot suite kit: subprocess scenario harness + golden normalizers + the `defineAcpSnapshotSuite` factory | (library — imported by example `*.snapshot.ts` suites) |
+| `agent-loop-testkit/` | Shared prerequisite mounting for tests that exercise the concrete agent loop | (library — imported by AgentLoop integration tests) |
 | `invariants/` | Runtime event-contract assertions for development diagnostics | (listens on `session/*`, `agent/*`) |
 | `loader-smoke/` | Shared real-Loader subprocess harness for keyless example smokes | (library — imported by example e2e suites) |
 | `llm-replay/` | Record/replay adapter: short-circuits `llm/stream` from a recorded session JSONL (keyless snapshot tests) | (listens on `llm/stream`) |
 | `subagent-mock/` | Scripted `SubagentProvider` for deterministic seam/tool tests | (registers on `ctx.subagents`) |
 
-`invariants` is development support but has no environment guard: it runs wherever registered, and the default `dsh-agent-spine-demo` bundle mounts it unconditionally. `llm-replay` backs the demos and the snapshot test tier under the per-file coverage gate. `acp-snapshot` carries the snapshot tier's harness/normalizer/suite machinery, while `loader-smoke` owns the parallel stdio/Loader process boundary used by keyless example e2e suites. `subagent-mock` exercises the real `ctx.subagents` load path without a model or child agent. A package graduates OUT of `support/` into a product group only when it gains documented product consumers.
+`invariants` is development support but has no environment guard: it runs wherever registered, and the default `dsh-agent-spine-demo` bundle mounts it unconditionally. `agent-loop-testkit` centralizes the mandatory service spine for hand-built AgentLoop tests without owning their loop or scenario. `llm-replay` backs the demos and the snapshot test tier under the per-file coverage gate. `acp-snapshot` carries the snapshot tier's harness/normalizer/suite machinery, while `loader-smoke` owns the parallel stdio/Loader process boundary used by keyless example e2e suites. `subagent-mock` exercises the real `ctx.subagents` load path without a model or child agent. A package graduates OUT of `support/` into a product group only when it gains documented product consumers.
diff --git a/packages/support/agent-loop-testkit/README.md b/packages/support/agent-loop-testkit/README.md
new file mode 100644
index 0000000000..350a8643e1
--- /dev/null
+++ b/packages/support/agent-loop-testkit/README.md
@@ -0,0 +1,27 @@
+# `@deepseek-ai/dsh-agent-loop-testkit`
+
+Shared prerequisite mounting for tests that exercise the concrete `AgentLoop`. `mountAgentLoopTestDependencies(ctx, options?)` installs the LLM, session, system-prompt, tool, and agent services in dependency order, then returns before the loop is mounted.
+
+The caller registers adapters and optional plugins, mounts `AgentLoop` with the configuration under test, and disposes its own Context. System-prompt and tool-registry configuration can be forwarded through `options`; the helper does not provide test defaults beyond those owned by the services. A plugin-load failure rejects the helper call, while services activated earlier in the sequence remain owned by the caller's Context.
+
+```ts
+import { Context } from 'cordis'
+import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
+
+const ctx = new Context()
+
+await mountAgentLoopTestDependencies(ctx)
+// Register the test adapter and any optional plugins here.
+await ctx.plugin(AgentLoop, { agents: [] })
+```
+
+Tests of injection failures, partial topology, service load order, or service teardown mount their dependencies directly instead of using this helper.
+
+## Model Experience
+
+None, as this test-only composition helper neither drives nor modifies model requests.
+
+## Known Limitations and Deferred Work
+
+- **Only the mandatory prerequisite spine is shared** — adapters, optional plugins, `AgentLoop`, agents, and Context teardown remain caller-owned so scenario-specific ordering stays visible.
diff --git a/packages/support/agent-loop-testkit/package.json b/packages/support/agent-loop-testkit/package.json
new file mode 100644
index 0000000000..423bd3e80d
--- /dev/null
+++ b/packages/support/agent-loop-testkit/package.json
@@ -0,0 +1,41 @@
+{
+  "name": "@deepseek-ai/dsh-agent-loop-testkit",
+  "description": "Shared prerequisite mounting for tests that exercise the concrete agent loop",
+  "version": "0.0.1",
+  "private": true,
+  "type": "module",
+  "main": "lib/index.js",
+  "types": "lib/types/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./lib/types/index.d.ts",
+      "default": "./lib/index.js"
+    },
+    "./src/*": "./src/*",
+    "./package.json": "./package.json"
+  },
+  "files": [
+    "lib/index.js",
+    "lib/types/**/*.d.ts",
+    "lib/types/**/*.d.ts.map",
+    "src"
+  ],
+  "license": "BSD-3-Clause",
+  "peerDependencies": {
+    "@deepseek-ai/dsh-agent": "^0.0.1",
+    "@deepseek-ai/dsh-llm": "^0.0.1",
+    "@deepseek-ai/dsh-session": "^0.0.1",
+    "@deepseek-ai/dsh-system-prompt": "^0.0.1",
+    "@deepseek-ai/dsh-tools": "^0.0.1",
+    "cordis": "^4.0.0-rc.7"
+  },
+  "devDependencies": {
+    "@deepseek-ai/dsh-agent": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-llm": "workspace:^",
+    "@deepseek-ai/dsh-session": "workspace:^",
+    "@deepseek-ai/dsh-system-prompt": "workspace:^",
+    "@deepseek-ai/dsh-tools": "workspace:^",
+    "cordis": "^4.0.0-rc.7"
+  }
+}
diff --git a/packages/support/agent-loop-testkit/src/index.ts b/packages/support/agent-loop-testkit/src/index.ts
new file mode 100644
index 0000000000..c7b0cb7304
--- /dev/null
+++ b/packages/support/agent-loop-testkit/src/index.ts
@@ -0,0 +1,46 @@
+/**
+ * Shared mounting for the services required before tests load the concrete
+ * agent loop. The caller retains ownership of the context, loop, adapters,
+ * optional plugins, and teardown.
+ * @module @deepseek-ai/dsh-agent-loop-testkit
+ */
+
+import type { Context } from 'cordis'
+import AgentRegistry from '@deepseek-ai/dsh-agent'
+import LlmService from '@deepseek-ai/dsh-llm'
+import SessionStore from '@deepseek-ai/dsh-session'
+import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
+import type { Config as SystemPromptConfig } from '@deepseek-ai/dsh-system-prompt'
+import ToolRegistry from '@deepseek-ai/dsh-tools'
+import type { Config as ToolRegistryConfig } from '@deepseek-ai/dsh-tools'
+
+/** Configuration forwarded to the prerequisite service plugins. */
+export interface AgentLoopTestDependenciesOptions {
+  /** Configuration for the system-prompt registry. */
+  readonly systemPrompt?: SystemPromptConfig
+  /** Configuration for the tool registry. */
+  readonly tools?: ToolRegistryConfig
+}
+
+/**
+ * Mount the standard prerequisite services for an AgentLoop test.
+ *
+ * The function deliberately does not mount AgentLoop or register an adapter,
+ * so tests retain control of load order and the topology under test. The
+ * context owns every mounted service and remains responsible for disposal. A
+ * plugin-load failure rejects the promise; services activated earlier in the
+ * sequence remain context-owned and unwind with that context.
+ * @param ctx - test context that owns the mounted services.
+ * @param options - optional service configuration forwarded without mutation.
+ * @returns after every prerequisite service has activated.
+ */
+export async function mountAgentLoopTestDependencies(
+  ctx: Context,
+  options: AgentLoopTestDependenciesOptions = {},
+): Promise<void> {
+  await ctx.plugin(LlmService)
+  await ctx.plugin(SessionStore)
+  await ctx.plugin(SystemPrompt, options.systemPrompt ?? {})
+  await ctx.plugin(ToolRegistry, options.tools ?? {})
+  await ctx.plugin(AgentRegistry)
+}
diff --git a/packages/support/agent-loop-testkit/tests/agent-loop-testkit.spec.ts b/packages/support/agent-loop-testkit/tests/agent-loop-testkit.spec.ts
new file mode 100644
index 0000000000..aa125b561f
--- /dev/null
+++ b/packages/support/agent-loop-testkit/tests/agent-loop-testkit.spec.ts
@@ -0,0 +1,20 @@
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { renderPrompt } from '@deepseek-ai/dsh-system-prompt'
+import { mountAgentLoopTestDependencies } from '../src/index.ts'
+
+describe('dsh-agent-loop-testkit', () => {
+  it('mounts a configurable prerequisite spine that can activate AgentLoop', async () => {
+    const ctx = new Context()
+    await mountAgentLoopTestDependencies(ctx, {
+      systemPrompt: { persona: 'Test persona.' },
+      tools: { mode: 'native' },
+    })
+
+    expect(renderPrompt(await ctx.systemPrompt.assemble())).toContain('Test persona.')
+    await expect(ctx.plugin(AgentLoop, { agents: [] })).resolves.toBeDefined()
+
+    await ctx.fiber.dispose()
+  })
+})
diff --git a/packages/support/agent-loop-testkit/tsconfig.json b/packages/support/agent-loop-testkit/tsconfig.json
new file mode 100644
index 0000000000..5e5b3c47f2
--- /dev/null
+++ b/packages/support/agent-loop-testkit/tsconfig.json
@@ -0,0 +1,33 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "lib/types"
+  },
+  "include": [
+    "src"
+  ],
+  "references": [
+    {
+      "path": "../../../vendor/cosmokit"
+    },
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../core/agent"
+    },
+    {
+      "path": "../../llm/llm"
+    },
+    {
+      "path": "../../core/session"
+    },
+    {
+      "path": "../../core/system-prompt"
+    },
+    {
+      "path": "../../core/tools"
+    }
+  ]
+}
diff --git a/packages/todo/tool-todo/package.json b/packages/todo/tool-todo/package.json
index 9ff69d7c76..bab0f1230c 100644
--- a/packages/todo/tool-todo/package.json
+++ b/packages/todo/tool-todo/package.json
@@ -30,6 +30,7 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
     "@deepseek-ai/dsh-system-prompt": "workspace:^",
diff --git a/packages/todo/tool-todo/tests/integration.spec.ts b/packages/todo/tool-todo/tests/integration.spec.ts
index 739367a699..c13a0f76f8 100644
--- a/packages/todo/tool-todo/tests/integration.spec.ts
+++ b/packages/todo/tool-todo/tests/integration.spec.ts
@@ -1,12 +1,9 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
 import type { SessionEvent } from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop, { ReactLoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as ToolTodo from '@deepseek-ai/dsh-tool-todo'
 import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
 
@@ -18,11 +15,7 @@ import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent
  */
 async function harness(adapter: MockAdapter): Promise<Context> {
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(ToolTodo)
   ctx.llm.registerAdapter(['mock'], adapter)
diff --git a/packages/ui/acp/package.json b/packages/ui/acp/package.json
index 71efc51a07..0a28c4f6da 100644
--- a/packages/ui/acp/package.json
+++ b/packages/ui/acp/package.json
@@ -42,6 +42,7 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-bash": "workspace:^",
     "@deepseek-ai/dsh-bash-local": "workspace:^",
     "@deepseek-ai/dsh-fs-local": "workspace:^",
diff --git a/packages/ui/acp/tests/harness.ts b/packages/ui/acp/tests/harness.ts
index 440120943f..f8e2e37627 100644
--- a/packages/ui/acp/tests/harness.ts
+++ b/packages/ui/acp/tests/harness.ts
@@ -5,13 +5,10 @@
  */
 
 import { Context } from 'cordis'
-import LlmService, { CallId, type GenerateOptions, type StreamChunk } from '@deepseek-ai/dsh-llm'
+import { CallId, type GenerateOptions, type StreamChunk } from '@deepseek-ai/dsh-llm'
 import { LlmAdapter } from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry from '@deepseek-ai/dsh-agent'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import SessionPersistenceJsonl from '@deepseek-ai/dsh-session-persistence-jsonl'
 import { LocalBashExecutor } from '@deepseek-ai/dsh-bash-local'
 import LocalFileSystem from '@deepseek-ai/dsh-fs-local'
@@ -188,11 +185,9 @@ export async function makeBridgeHarness(options: {
   const adapter = new MockAdapter(options.script ?? [])
 
   const ctx = new Context()
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt, { persona: options.persona ?? '' })
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx, {
+    systemPrompt: { persona: options.persona ?? '' },
+  })
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(SessionPersistenceJsonl, { root: options.storageDir })
   await ctx.plugin(UserInteractionService)
diff --git a/packages/workflow/workflow-workerthread/package.json b/packages/workflow/workflow-workerthread/package.json
index 485e252c97..1cd6e07e17 100644
--- a/packages/workflow/workflow-workerthread/package.json
+++ b/packages/workflow/workflow-workerthread/package.json
@@ -42,6 +42,7 @@
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
+    "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
     "@deepseek-ai/dsh-brand": "workspace:^",
     "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
diff --git a/packages/workflow/workflow-workerthread/tests/integration.spec.ts b/packages/workflow/workflow-workerthread/tests/integration.spec.ts
index 0e1727f877..7b30f13f4f 100644
--- a/packages/workflow/workflow-workerthread/tests/integration.spec.ts
+++ b/packages/workflow/workflow-workerthread/tests/integration.spec.ts
@@ -1,11 +1,8 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService from '@deepseek-ai/dsh-llm'
-import SessionStore from '@deepseek-ai/dsh-session'
-import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
-import ToolRegistry from '@deepseek-ai/dsh-tools'
-import AgentRegistry, { AgentId } from '@deepseek-ai/dsh-agent'
+import { AgentId } from '@deepseek-ai/dsh-agent'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
+import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
 import * as Invariants from '@deepseek-ai/dsh-invariants'
 import SubagentService from '@deepseek-ai/dsh-subagent'
 import * as spawn from '@deepseek-ai/dsh-subagent-spawn'
@@ -26,11 +23,7 @@ type Script = ConstructorParameters<typeof MockAdapter>[0]
 async function setup(script: Script) {
   const ctx = new Context()
   const adapter = new MockAdapter(script)
-  await ctx.plugin(LlmService)
-  await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
-  await ctx.plugin(ToolRegistry)
-  await ctx.plugin(AgentRegistry)
+  await mountAgentLoopTestDependencies(ctx)
   await ctx.plugin(Invariants)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(SubagentService)
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index b1a3a78030..7b12699ad8 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -155,6 +155,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-bash':
         specifier: workspace:^
         version: link:../bash
@@ -228,6 +231,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-compact':
         specifier: workspace:^
         version: link:../compact
@@ -240,9 +246,6 @@ importers:
       '@deepseek-ai/dsh-session':
         specifier: workspace:^
         version: link:../../core/session
-      '@deepseek-ai/dsh-system-prompt':
-        specifier: workspace:^
-        version: link:../../core/system-prompt
       '@deepseek-ai/dsh-tools':
         specifier: workspace:^
         version: link:../../core/tools
@@ -262,6 +265,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-llm':
         specifier: workspace:^
         version: link:../../llm/llm
@@ -296,6 +302,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-llm':
         specifier: workspace:^
         version: link:../../llm/llm
@@ -648,6 +657,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-fs':
         specifier: workspace:^
         version: link:../fs
@@ -688,15 +700,15 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-llm':
         specifier: workspace:^
         version: link:../../llm/llm
       '@deepseek-ai/dsh-session':
         specifier: workspace:^
         version: link:../../core/session
-      '@deepseek-ai/dsh-system-prompt':
-        specifier: workspace:^
-        version: link:../../core/system-prompt
       '@deepseek-ai/dsh-tools':
         specifier: workspace:^
         version: link:../../core/tools
@@ -728,6 +740,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-bash':
         specifier: workspace:^
         version: link:../../bash/bash
@@ -746,9 +761,6 @@ importers:
       '@deepseek-ai/dsh-subagent':
         specifier: workspace:^
         version: link:../../subagent/subagent
-      '@deepseek-ai/dsh-system-prompt':
-        specifier: workspace:^
-        version: link:../../core/system-prompt
       '@deepseek-ai/dsh-tools':
         specifier: workspace:^
         version: link:../../core/tools
@@ -768,6 +780,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-bash':
         specifier: workspace:^
         version: link:../../bash/bash
@@ -783,9 +798,6 @@ importers:
       '@deepseek-ai/dsh-session':
         specifier: workspace:^
         version: link:../../core/session
-      '@deepseek-ai/dsh-system-prompt':
-        specifier: workspace:^
-        version: link:../../core/system-prompt
       '@deepseek-ai/dsh-tools':
         specifier: workspace:^
         version: link:../../core/tools
@@ -1152,6 +1164,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-invariants':
         specifier: workspace:^
         version: link:../../support/invariants
@@ -1170,12 +1185,6 @@ importers:
       '@deepseek-ai/dsh-subagent-spawn':
         specifier: workspace:^
         version: link:../subagent-spawn
-      '@deepseek-ai/dsh-system-prompt':
-        specifier: workspace:^
-        version: link:../../core/system-prompt
-      '@deepseek-ai/dsh-tools':
-        specifier: workspace:^
-        version: link:../../core/tools
       cordis:
         specifier: ^4.0.0-rc.7
         version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
@@ -1188,6 +1197,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-invariants':
         specifier: workspace:^
         version: link:../../support/invariants
@@ -1225,6 +1237,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-bash-local':
         specifier: workspace:^
         version: link:../../bash/bash-local
@@ -1246,18 +1261,12 @@ importers:
       '@deepseek-ai/dsh-subagent-inprocess':
         specifier: workspace:^
         version: link:../subagent-inprocess
-      '@deepseek-ai/dsh-system-prompt':
-        specifier: workspace:^
-        version: link:../../core/system-prompt
       '@deepseek-ai/dsh-tool-bash':
         specifier: workspace:^
         version: link:../../bash/tool-bash
       '@deepseek-ai/dsh-tool-subagent':
         specifier: workspace:^
         version: link:../tool-subagent
-      '@deepseek-ai/dsh-tools':
-        specifier: workspace:^
-        version: link:../../core/tools
       cordis:
         specifier: ^4.0.0-rc.7
         version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
@@ -1321,6 +1330,30 @@ importers:
         specifier: ^4.0.0-rc.7
         version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
 
+  packages/support/agent-loop-testkit:
+    devDependencies:
+      '@deepseek-ai/dsh-agent':
+        specifier: workspace:^
+        version: link:../../core/agent
+      '@deepseek-ai/dsh-agent-loop':
+        specifier: workspace:^
+        version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-llm':
+        specifier: workspace:^
+        version: link:../../llm/llm
+      '@deepseek-ai/dsh-session':
+        specifier: workspace:^
+        version: link:../../core/session
+      '@deepseek-ai/dsh-system-prompt':
+        specifier: workspace:^
+        version: link:../../core/system-prompt
+      '@deepseek-ai/dsh-tools':
+        specifier: workspace:^
+        version: link:../../core/tools
+      cordis:
+        specifier: ^4.0.0-rc.7
+        version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
+
   packages/support/invariants:
     devDependencies:
       '@deepseek-ai/dsh-agent':
@@ -1464,6 +1497,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-llm':
         specifier: workspace:^
         version: link:../../llm/llm
@@ -1498,6 +1534,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-bash':
         specifier: workspace:^
         version: link:../../bash/bash
@@ -1894,6 +1933,9 @@ importers:
       '@deepseek-ai/dsh-agent-loop':
         specifier: workspace:^
         version: link:../../core/agent-loop
+      '@deepseek-ai/dsh-agent-loop-testkit':
+        specifier: workspace:^
+        version: link:../../support/agent-loop-testkit
       '@deepseek-ai/dsh-brand':
         specifier: workspace:^
         version: link:../../util/brand
diff --git a/scripts/verify-package-readme-model-experience.ts b/scripts/verify-package-readme-model-experience.ts
index 8220324210..bfcb6f684e 100644
--- a/scripts/verify-package-readme-model-experience.ts
+++ b/scripts/verify-package-readme-model-experience.ts
@@ -57,6 +57,7 @@ const SENTENCE_MODEL_EXPERIENCE: Readonly<Record<string, SentenceContract>> = {
   'packages/subagent/subagent': { kind: 'indirect', reason: 'The provider registry delegates parent-model rendering to dsh-tool-subagent.' },
   'packages/subagent/subagent-subprocess': { kind: 'indirect', reason: 'Only process-based subagent backends compose a child model request.' },
   'packages/support/acp-snapshot': { kind: 'none', reason: 'The test harness observes and normalizes transcripts without changing live requests.' },
+  'packages/support/agent-loop-testkit': { kind: 'none', reason: 'The test helper mounts services but neither drives nor modifies model requests.' },
   'packages/support/invariants': { kind: 'none', reason: 'The observer validates requests but never rewrites their context.' },
   'packages/support/loader-smoke': { kind: 'none', reason: 'The test harness observes child-process streams without changing live requests.' },
   'packages/support/llm-replay': { kind: 'none', reason: 'The keyless adapter invokes no provider model.' },
diff --git a/tsconfig.build.json b/tsconfig.build.json
index 3a57169005..edb1479088 100644
--- a/tsconfig.build.json
+++ b/tsconfig.build.json
@@ -56,6 +56,7 @@
     { "path": "./packages/web/tool-web" },
     { "path": "./packages/timeout/timeout-policy" },
     { "path": "./packages/support/invariants" },
+    { "path": "./packages/support/agent-loop-testkit" },
     { "path": "./packages/ui/acp" },
     { "path": "./packages/examples/acp-demo" },
     { "path": "./packages/ui/app-boot" },
diff --git a/tsconfig.json b/tsconfig.json
index 6585a987d6..5a09464252 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -67,6 +67,7 @@
     { "path": "./packages/web/tool-web" },
     { "path": "./packages/timeout/timeout-policy" },
     { "path": "./packages/support/invariants" },
+    { "path": "./packages/support/agent-loop-testkit" },
     { "path": "./packages/ui/acp" },
     { "path": "./packages/examples/acp-demo" },
     { "path": "./packages/ui/app-boot" },