feat: 支持动态创建子agent能力

docs/mkdocs/en/multi_agents.md

@@ -311,6 +311,13 @@ Coordinator Agent (Main Entry Point)
 | `disallow_transfer_to_peers` | `False` | Set to `True` to prevent a child Agent from transferring control to peer Agents |
 | `default_transfer_message` | `None` | Custom transfer instruction that overrides the default transfer prompt |
 
+#### Spawned Sub-Agents
+
+As an alternative to persistent `sub_agents` (transfer-based), you can spawn
+short-lived sub-agents at run time via ``SpawnSubAgentTool`` (pick from a
+pre-registered catalog) or ``DynamicSubAgentTool`` (LLM defines the role on the
+fly). See [Sub-Agent Tools](sub_agent.md).
+
 ## Compose Patterns (Compose Agents)
 
 Different orchestration patterns can be flexibly combined, connecting results of different stages via `output_key` to create more complex workflows:

docs/mkdocs/en/sub_agent.md

@@ -0,0 +1,272 @@
+# Spawned Sub-Agents
+
+Complex tasks often require delegated subtasks — computing results, searching codebases, auditing for security issues. Doing everything in the parent agent's own context causes several problems:
+
+- **Context pollution**: exploratory searches, tool outputs, and intermediate steps fill the context window, crowding out what matters.
+- **Tool sprawl**: the parent carries every tool all the time, even though most subtasks only need a subset.
+- **No role isolation**: the parent has one system prompt; it cannot adopt a different persona or constraints per subtask.
+- **No outside perspective**: an agent reviewing its own work is inherently biased — it's unlikely to spot its own mistakes. A fresh context acts as a second pair of eyes, auditing code, challenging a design, or verifying a claim without the parent's assumptions and reasoning shortcuts.
+
+A **short-lived sub-agent** is a natural fit for these problems: a fresh context per delegation, only the tools it needs, a dedicated system prompt. It runs, returns its result, and is destroyed — keeping the parent conversation clean and focused.
+
+**Spawned Sub-Agents** give the parent agent two tools for creating short-lived sub-agents at run time:
+
+- **`SpawnSubAgentTool`** — choose from a **pre-defined catalog** of standardized specialists. Instruction, tool set, and model are locked by the archetype at construction time.
+
+  Use this when you have a fixed set of expert roles (security auditor, code explorer, planner) and want the LLM to pick the right one per task. The parent LLM selects via `subagent_type` and writes a task-specific `prompt`, but cannot alter the sub-agent's instruction or tools.
+
+- **`DynamicSubAgentTool`** — the LLM **invents the specialist on the fly**, writing the instruction at call time. No pre-registration needed.
+
+  Use this when you cannot predict all the specialist types you'll need ahead of time. Every call can define a different role — the LLM decides what expertise, constraints, and tool subset each task requires.
+
+The difference is *who defines the role*: the developer (Spawn) or the LLM (Dynamic).
+
+## Quick Start
+
+```python
+from trpc_agent_sdk.agents import LlmAgent
+from trpc_agent_sdk.tools import SpawnSubAgentTool, DynamicSubAgentTool
+
+# Spawn: pick from a catalog of pre-defined specialists
+agent_with_spawn = LlmAgent(
+    name="orchestrator",
+    tools=[SpawnSubAgentTool()],  # built-in `default` archetype
+)
+
+# Dynamic: LLM writes the specialist's role at call time
+agent_with_dynamic = LlmAgent(
+    name="orchestrator",
+    tools=[DynamicSubAgentTool()],  # sub-agent inherits all parent tools
+)
+```
+
+## Two Tools
+
+| | `SpawnSubAgentTool` | `DynamicSubAgentTool` |
+| --- | --- | --- |
+| **Pattern** | Pick from a pre-defined catalog | LLM invents role at call time |
+| **Who defines the role** | Developer, two modes:<br>① `SubAgentArchetype` in code<br>② Markdown file (YAML frontmatter + body) | LLM (via `instruction` parameter) |
+| **Best for** | Standardized, repeatable specialists | Roles you can't pre-register |
+| **Role flexibility** | Locked — only `prompt` varies | Full — every call can be different |
+| **Tool surface** | Locked by archetype | Inherits parent tools; LLM can narrow via `tools` |
+
+### `SpawnSubAgentTool`
+
+Dispatches tasks to pre-registered archetypes. The parent LLM picks the right specialist via `subagent_type`; its instruction and tools are fixed.
+
+```python
+class SpawnSubAgentTool(BaseTool):
+    def __init__(
+        self,
+        agents: list[SubAgentArchetype] | None = None,
+        agent_paths: list[str | os.PathLike] | None = None,
+        tool_mapping: dict[str, Any] | None = None,
+        with_default: bool = True,
+        agent_config: SubAgentConfig | None = None,
+        skip_summarization: bool = False,
+        filters_name: list[str] | None = None,
+        filters: list[BaseFilter] | None = None,
+    ) -> None: ...
+```
+
+| parameter | meaning |
+| --- | --- |
+| `agents` | Additional archetypes to register. |
+| `agent_paths` | Directories of `*.md` files to load archetypes from disk. |
+| `tool_mapping` | Custom tool name → tool class mapping for resolving MD frontmatter. |
+| `with_default` | Whether to register the built-in `default` archetype. Default `True`. |
+| `agent_config` | `SubAgentConfig` applied to every spawned sub-agent. |
+| `skip_summarization` | When `True`, skip the parent's summarization turn after the sub-agent returns. |
+
+**Three ways to configure:**
+
+```python
+# Zero config — only the built-in `default` archetype
+SpawnSubAgentTool()
+
+# Code-defined archetypes
+SpawnSubAgentTool(agents=[security_auditor, EXPLORE_AGENT, PLAN_AGENT])
+
+# Load from Markdown files
+SpawnSubAgentTool(agent_paths=[".trpc_agents/"])
+```
+
+#### `SubAgentArchetype`
+
+A frozen template that describes *one kind of sub-agent the parent is allowed to spawn*. It locks down the dangerous knobs (instruction, tools, model) so prompt-injected calls cannot reshape the sub-agent.
+
+```python
+@dataclass(frozen=True)
+class SubAgentArchetype:
+    name: str                      # registry key + the value LLM passes as `subagent_type`
+    description: str               # what the LLM reads to pick this archetype
+    instruction: str | InstructionProvider
+    tools: tuple | None = None     # None = inherit all parent tools
+    model: Any = None              # None = inherit via SubAgentConfig or parent's model
+```
+
+- **`description`** — read by the **parent LLM** when selecting which archetype to spawn. Third-person, selection-focused.
+- **`instruction`** — the **sub-agent's** system prompt. Second-person, execution-focused. Supports both strings and `InstructionProvider` callables.
+
+#### Built-in Archetypes
+
+| name | tools | typical use |
+| --- | --- | --- |
+| `default` | `None` (inherits all parent tools) | **Neutral task executor.** Does not impose a specific role. **Auto-registered.** |
+| `general-purpose` | `None` (inherits all parent tools) | **Researcher / explorer** with soft "NEVER create files" constraints. Opt-in only. |
+| `Explore` | `Read` / `Glob` / `Grep` / `WebFetch` | Read-only search: locate files, grep symbols. |
+| `Plan` | `Read` / `Glob` / `Grep` | Design implementation plans without modifying code. |
+
+Only `default` is auto-registered. `general-purpose`, `Explore`, and `Plan` must be explicitly added via the `agents` parameter.
+
+### `DynamicSubAgentTool`
+
+The LLM writes the sub-agent's `instruction` at call time, creating any specialist on the fly. By default the sub-agent inherits all parent tools.
+
+```python
+class DynamicSubAgentTool(BaseTool):
+    def __init__(
+        self,
+        name: str = "dynamic_subagent",
+        description: str | None = None,
+        tools: tuple | None = None,
+        expose_tool_selection: bool = True,
+        agent_config: SubAgentConfig | None = None,
+        skip_summarization: bool = False,
+        filters_name: list[str] | None = None,
+        filters: list[BaseFilter] | None = None,
+    ) -> None: ...
+```
+
+| parameter | meaning |
+| --- | --- |
+| `name` | Tool name. Default `"dynamic_subagent"`. |
+| `description` | Tool description. |
+| `tools` | Fixed tool set for the sub-agent. `None` (default) = inherit all parent tools. |
+| `expose_tool_selection` | When `True` (default), the `tools` field is exposed so the LLM can narrow the tool surface per call. |
+| `agent_config` | `SubAgentConfig` applied to every spawned sub-agent. |
+| `skip_summarization` | When `True`, skip the parent's summarization turn after the sub-agent returns. |
+
+## Shared Configuration
+
+### `SubAgentConfig`
+
+Unified construction-time defaults for every spawned sub-agent. `None` means "inherit from the parent agent".
+
+```python
+@dataclass(frozen=True)
+class SubAgentConfig:
+    model: LLMModel | None = None
+    """Model for the sub-agent. None inherits the parent's model."""
+
+    generate_content_config: GenerateContentConfig | None = None
+    """Generation config (temperature, top_p, etc.). None inherits from parent."""
+
+    parallel_tool_calls: bool | None = None
+    """Whether the sub-agent may issue parallel tool calls. None inherits from parent."""
+
+    include_parent_history: bool = False
+    """Whether to inject parent conversation history into the sub-agent's session."""
+
+    max_parent_history_turns: int | None = None
+    """Max parent turns to inject. None = unlimited. Only used when include_parent_history=True."""
+
+    max_turns: int | None = None
+    """Max LLM calls the sub-agent may make. None = unlimited."""
+```
+
+## Usage
+
+### SpawnSubAgentTool
+
+**Zero config** — only the built-in `default` archetype:
+
+```python
+from trpc_agent_sdk.agents import LlmAgent
+from trpc_agent_sdk.tools import SpawnSubAgentTool
+
+orchestrator = LlmAgent(
+    name="main",
+    model=opus_model,
+    instruction="When a task benefits from isolated context, spawn a sub-agent via spawn_subagent.",
+    tools=[SpawnSubAgentTool()],
+)
+```
+
+**Code-defined archetypes**:
+
+```python
+from trpc_agent_sdk.agents.sub_agent import SubAgentArchetype
+from trpc_agent_sdk.tools import SpawnSubAgentTool
+
+security_auditor = SubAgentArchetype(
+    name="security-auditor",
+    description="Use for security code audit. **IMPORTANT:** This agent is read-only.",
+    instruction="You are a security auditor...",
+    tools=(ReadTool, GrepTool, GlobTool),
+)
+
+orchestrator = LlmAgent(
+    tools=[SpawnSubAgentTool(agents=[security_auditor])],
+)
+```
+
+**Loading archetypes from Markdown files**:
+
+Place `.md` files in a directory with YAML frontmatter:
+
+```markdown
+---
+name: security-auditor
+description: Use for security code audit.
+tools:
+  - Read
+  - Glob
+  - Grep
+---
+
+You are a security auditor...
+```
+
+```python
+tools=[SpawnSubAgentTool(agent_paths=[".trpc_agents/"])]
+```
+
+### DynamicSubAgentTool
+
+**Unbounded (default)** — the sub-agent inherits all parent tools. The LLM narrows the tool set per call via `tools`:
+
+```python
+from trpc_agent_sdk.agents import LlmAgent
+from trpc_agent_sdk.tools import DynamicSubAgentTool
+
+orchestrator = LlmAgent(
+    name="main",
+    model=opus_model,
+    instruction="When you need a specialist, create one via dynamic_subagent. Narrow tools as needed.",
+    tools=[DynamicSubAgentTool()],
+)
+```
+
+**Bounded** — the sub-agent uses a fixed tool set. The parent agent has no direct access to those tools; every task must be delegated. This is useful for keeping dangerous tools behind the sub-agent boundary:
+
+```python
+orchestrator = LlmAgent(
+    name="main",
+    model=opus_model,
+    instruction="You can only use tools by delegating via dynamic_subagent. Do not attempt direct calls.",
+    tools=[
+        DynamicSubAgentTool(
+            tools=(calculator, word_count),
+            expose_tool_selection=False,
+        ),
+    ],
+)
+```
+
+## Additional Notes
+
+- **Tool inheritance**: `DynamicSubAgentTool()` inherits all parent tools by default; pass `tools=(...)` to give the sub-agent a fixed set instead. For `SpawnSubAgentTool`, the archetype's `tools` field decides — `None` means inherit, `(ReadTool, ...)` means that exact set. In all cases, spawn tools are stripped from the sub-agent to prevent recursion.
+- **Session isolation**: sub-agents run in a fresh ephemeral session. Parent history is not shared by default; opt in via `include_parent_history=True`.
+- **Nesting**: 1-level hard cap. Sub-agents cannot spawn further sub-agents.
+- **Result shape**: the sub-agent's final text is returned as the tool result string.

docs/mkdocs/zh/multi_agents.md

@@ -311,6 +311,10 @@ Route customer inquiries:
 | `disallow_transfer_to_peers` | `False` | 设为 `True` 禁止子 Agent 将控制权转给同级 Agent |
 | `default_transfer_message` | `None` | 自定义转移指令，覆盖默认的转移提示语 |
 
+#### Spawned Sub-Agents
+
+除持久化的 `sub_agents`（基于 transfer）之外，还可以在运行时通过 ``SpawnSubAgentTool``（从预注册目录中选择）或 ``DynamicSubAgentTool``（LLM 现场定义角色）创建短期子 agent。详见 [子 Agent 工具](sub_agent.md)。
+
 ## 组合模式（Compose Agents）
 
 不同的编排模式可以灵活组合，通过 `output_key` 连接不同阶段的结果，创建更复杂的工作流：