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[Feature Request] Allow subagents to override reasoning effort in CustomAgentConfig (parity with Claude Agent SDK) #1131
Description
Activity
+1 — observed adjacent gap on Copilot CLI v1.0.40. While testing per-launch
model:(which the closing comment ongithub/copilot-cli#2939suggests should work for subagents), I found thatmodel:arguments and frontmatter are silently dropped attaskdispatch — sub-agents inherit the parent session's model. The#2939close comment explicitly notes thatCustomAgentConfig"doesn't yet exposemodel," which is the same architectural shape as this issue's missingeffortfield: the YAML/runtime side parses the value, but the SDK dispatch type can't carry it through to inference.If both fixes (model + effort fields on
CustomAgentConfig) land together, the per-agent routing and per-agent reasoning-effort use cases on the customization-repo side both unblock. Reproduction for the model side: https://github.com/spencerbk/copilot-config/blob/dev/docs/incidents/2026-05-02-copilot-cli-subagent-model-ignored.md. Related:github/copilot-cli#2939(closed "partial"),github/copilot-cli#1354(open),github/copilot-cli#2904(open — per-agent effort on the CLI side).Any update in this?
Similar request for VS Code Chat was closed with the comment that GitHub team is moving their effort to support Copilot SDK: microsoft/vscode#327099Reacted by arun-8687, MStrohQAM, scorpyonmike and Julien GThere are multi-agent workflows that would GREATLY benefit from the ability to control the reasoning level of each sub agent call.
This topic needs some attention.Reacted by Julien G, spencerbk and Lucien TheronI'm very interested in seeing subagent reasoning effort support. Surprised it's missing entirely.
Summary
Allow custom subagents defined via
CustomAgentConfigto specify their own reasoning effort independent of the orchestrator session's reasoning. The Claude Agent SDK supports this via aneffortfield onAgentDefinition. copilot-sdk'sCustomAgentConfigdoes not, so reasoning is fixed at session level and applies uniformly to every subagent invocation.Motivation
highormaxreasoning for planning and delegationCurrent state
CustomAgentConfig(copilot-sdktypes.d.ts, lines 802 to 833) has noreasoningEffortoreffortfieldreasoningEffortinproviderOptionsapplies to all subagent dispatches in that sessionProposed
reasoningEffort(oreffort) field toCustomAgentConfiglow | medium | high | xhigh | max, plus numeric for models that support itPrecedent
Claude Agent SDK's
AgentDefinition.effort:https://code.claude.com/docs/en/agent-sdk/subagents
Identical value vocabulary already in use by this SDK.
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