[Bug] Subagent spawned via Task tool uses global config model instead of inheriting parent session's active model #17870

Description

When a primary agent running a non-default model (e.g. selected interactively or different from opencode.json) spawns a subagent via the Task tool, the subagent ignores the parent's active session model and falls back to the global "model" defined in opencode.json.

The docs state:

"If you don't specify a model, subagents will use the model of the primary agent that invoked the subagent."

This does not happen in practice when the session model differs from the global config.

Expected behavior: Subagent inherits the active model of the parent session that invoked it.

Actual behavior: Subagent uses the global config default (opencode.json "model" field), ignoring the parent's active session model.

Related issues:

• [FEATURE]: Dynamic model selection for subagents via Task tool #6651 — feature request for dynamic model selection via Task tool
• • feat: add model parameter to Task tool for dynamic subagent model selection #14961 — PR adding explicit model param to Task tool (workaround, not a fix for auto-inheritance)

Plugins

No response

OpenCode version

v1.2.27

Steps to reproduce

1. Set "model": "azure/gpt-4o" in opencode.json (global default)
2. 2. Start an opencode session and switch to anthropic/claude-sonnet-4-6 interactively via the model picker
3. 3. Primary agent (running claude-sonnet-4-6) invokes a subagent via the Task tool — no explicit model param passed
4. 4. Observe: subagent runs on azure/gpt-4o (global default) instead of anthropic/claude-sonnet-4-6 (parent's active model)

Screenshot and/or share link

No response

Operating System

Linux (Ubuntu 24.04)

Terminal

opencode TUI