SubAgentMiddleware regression — runtime config not passed to subagent invocations (PR #602 fix lost in #1041 refactor)

[kushmadlani]

Checked other resources

• This is a bug, not a usage question.
• I added a clear and descriptive title.
• I searched existing issues and didn't find this.
• I can reproduce this with the latest released version.
• I included a minimal reproducible example and steps to reproduce.

Area (Required)

• deepagents (SDK)
• cli

Related Issues / PRs

#569, #139, #602, #1041

Reproduction Steps / Example Code (Python)

from dataclasses import dataclass
from langchain.agents import create_agent
from langchain.tools import tool, ToolRuntime
from deepagents import create_deep_agent

@dataclass
class MyContext:
    api_url: str = "https://example.com"

@tool
def check_context(query: str, runtime: ToolRuntime[MyContext]) -> str:
    """Tool that needs runtime.context."""
    return f"Context: {runtime.context.api_url}"

agent = create_deep_agent(
    tools=[check_context],
    context_schema=MyContext,
)

# This works:
agent.invoke({"messages": [...]}, context=MyContext())

# But when the agent delegates to a subagent via the task tool,
# the subagent's tools receive runtime.context = None

Error Message and Stack Trace (if applicable)

Description

• I'm trying to use the deepagents library with context_schema so subagent tools can access runtime.context.
• I expect runtime.context to be available in tools called by subagents (as it was after PR fix(deepagents): Pass through runtime config to subagents #602 fixed this in Dec 2025).
• Instead, runtime.context is None in subagent tools. PR feat(sdk): subagent skills, middleware refactor #1041 (Feb 4, 2026) rewrote subagents.py and dropped the runtime.config pass-through from _build_task_tool(). The fix is to pass runtime.config to subagent.invoke() and subagent.ainvoke() — the exact one-line change from PR fix(deepagents): Pass through runtime config to subagents #602.

Environment / System Info

No response

[sydney-runkle]

Curious, what context do you want to pass through to the subagent?