[Feature] 子代理可继承派活主会话的工具/Skill（Task/改模式除外） / Let subagents inherit the parent turn's tools and skills

[xingleiwu]

Problem / 问题

Subagents already inherit permission mode (permission: inherit) and can inherit the session model (empty model pin). They do not inherit the parent turn's tools / skills / plugin tools.

A built-in explorer is:

tools: [Read, Glob, Grep, Bash]

The assignable whitelist is hard-coded:

SUBAGENT_ASSIGNABLE_TOOLS = [Read, Glob, Grep, BrowserPreview, Bash, Edit, Write]
DEFAULT_SUBAGENT_TOOLS    = [Read, Glob, Grep]

Settings copy is explicit: “Read-only by default. A delegate never inherits anything you don't grant here.”

So a parent Agent with Skill, MCP, plugin tools, ToolSearch, and the same workspace cannot give any of that to the worker it just spawned. Typical fallout on 0.14.6:

• Parent is tracing PI-Desktop internals. Explorer has no Skill, no asar-aware tools, and guesses Composer.tsx / truncated scratch paths → Read directory (INVALID_ARGUMENT) and os error 3.
• Parent loaded delivery-contract via Skill. Explorer cannot load it even if the task matches.
• Parent can ToolSearch on-demand tools. Explorer cannot.

模型 pin 和权限已经能跟会话走；工具能力不能。主会话刚派出去的活，子代理却是另一套残缺工具箱。

Proposed change / 期望改动

Add an inherit path for tools, same idea as permission/model, without turning every explorer into a nested Agent.

Suggested frontmatter:

tools: inherit          # parent's currently enabled tool names, minus a deny list
# or
tools: [inherit, Bash]  # inherit + extras still on the assignable list

Default for builtins can stay today's whitelist (explorer stays read-mostly). Default for user-defined subagents, or a Settings toggle:

Subagents inherit the parent turn's tools (except Task / mode-switch / Ask)

Deny list (never inherit, even with inherit):

Keep off delegates	Why
Task / TaskWait / TaskList / TaskStop	no nested fan-out
EnterPlanMode / EnterGoalMode	mode is the parent's
asktool	subagent cannot see the user

Allow inherit (parent has them ⇒ delegate gets them):

• Skill (and the same pluginSkills catalog the parent already received)
• ToolSearch if the parent is using on-demand tools
• plugin / MCP tools the parent was allowed to call
• Read / Glob / Grep / Bash / Edit / Write / BrowserPreview as today

Runtime shape:

1. When spawning SubagentRun, build tools from definition.tools. If the list contains inherit (or a new inheritTools: true), union with parent.availableToolNames minus the deny list.
2. Pass the parent's pluginSkills into the delegate Agent so Skill { id } resolves. Do not require the child to ToolSearch for Skill if the parent already had it as a core/on-demand tool.
3. Keep workspace + scratch roots the same as the parent (they already share projectPath / scratchDir — the missing piece is tools, not cwd).
4. Settings: checkbox 「子代理继承当前会话工具」 / Inherit parent tools, default off for builtins, on for user agents — or honor tools: inherit in the markdown.

UI toolsHint today says the opposite; update it to: inherit is opt-in, mutating tools still need an explicit grant or inherit.

Alternatives / 其他方案

• Put Skill on SUBAGENT_ASSIGNABLE_TOOLS only: helps skill routing, still no MCP/plugin tools, still a second catalog.
• Always give explorer *: too wide (fixer-level writes on a search agent).
• Prompt the parent “pass every path in the Task text”: works around missing Skill/ToolSearch, still a tax on every delegation.

Additional context / 补充信息

PI-Desktop 0.14.6 · Windows.

Already inherited today:

• permission default inherit
• empty model → session model
• thinking “Same as the session”

Not inherited: tool names, Skill catalog, plugin/MCP tools.

Code:

• packages/shared SUBAGENT_ASSIGNABLE_TOOLS / DEFAULT_SUBAGENT_TOOLS / parseSubagentDefinition
• packages/agent-runtime/src/subagent-definitions.ts builtin explorer/fixer docs
• packages/agent-runtime SubagentRun (tools: opts.tools) vs parent Runtime.buildTools() (skillTools only if mode === "agent")
• Settings i18n toolsHint

Related: #204 (Skill as Agent core tool) — even if Skill is core on the parent, delegates still cannot call it until it is assignable or inherited.

[ZxlDragonDoctor]

I'd like to take this. I'll implement opt-in tool inheritance for subagents: ools: inherit (or union with assignable list), deny-list Task/mode-switch/asktool, pass parent pluginSkills so Skill resolves, keep builtins defaulting to today's whitelist. Will add unit tests around parse + spawn tool assembly.

[vastsa]

Implemented. Subagents can opt in with tools: inherit / tools: [inherit, Bash].

已实现。子代理可通过 tools: inherit（或与可分配工具并列）继承主会话的 Skill / MCP / 插件工具。

• Builtins stay on today's whitelist (explorer is still read-mostly).
• Never inherited: Task* / mode switches / asktool / new_context / ToolSearch.
• host-core and Settings round-trip the inherit token.
• ADR 0246, D415, E2E-SUBAGENT-inherit-parent-tools.

Landed from PR #319 (contributor commit preserved) plus follow-up on local main.