feat(opencode): add model parameter to task tool for subagent model override by funkybooboo · Pull Request #26535 · anomalyco/opencode · GitHub

Issue for this PR

Type of change

Bug fix
New feature
Refactor / code improvement
Documentation

What does this PR do?

Adds an optional model parameter to the task tool, allowing callers to override which model a subagent uses at runtime. Accepts provider/model format (e.g. anthropic/claude-sonnet-4, openai/gpt-4o).

Model priority: params.model (task tool call) -> agent.model (agent config) -> parent session model (inherit)

Security: Model overrides are gated by model_override permission -- denied by default. Users must explicitly opt in via config. This prevents prompt injection from escalating to expensive models.

Example config:

{
  "permission": {
    "model_override": {
      "anthropic/*": "allow",
      "openai/gpt-4o": "allow"
    }
  }
}

Relationship to prior PRs

This PR addresses the same issue (#17595) as several other open PRs, with different tradeoffs:

PR	Approach	Status	Key difference
#18528	model param + model_override permission	Open, stalled	Nearly identical approach. Uses zod schema and iife() helper; this PR uses Effect Schema and inline parsing. Both have the same permission gate.
#11217	@agent:provider/model syntax in prompt + TUI autocomplete + permission.model	Open	UI-driven approach with @ mention syntax. Much larger scope -- includes TUI and web UI changes.
#11377	model_tier param (quick/standard/advanced) + configurable tier-to-model mapping	Open	Tier abstraction layer rather than direct model selection. Adds a tier config system.
#17570	Config/UI-based agent-to-model assignment (assign-model command)	Open	Static config-only approach. No runtime model selection.

This PR takes the minimal, permission-gated approach from #18528 (which appears stalled since early May) with an Effect Schema implementation matching current codebase patterns.

Changes

packages/opencode/src/tool/task.ts -- Added model optional string param to Parameters schema. When provided:

Validates the provider/model format (rejects missing / or empty parts with a clear error message)
Asks model_override permission with the model and provider wildcard as patterns
Parses into ProviderID/ModelID branded types using lightweight imports from provider/schema.ts
Falls through to agent.model or parent session model when not provided

packages/opencode/src/tool/task.txt -- Added "Model selection" section documenting the new parameter and permission requirement.

packages/opencode/src/agent/agent.ts -- Added model_override: "deny" to default permission set for all agents.

packages/opencode/src/config/permission.ts -- Added model_override to the config permission schema so users can configure it in opencode.json.

packages/opencode/test/tool/task.test.ts -- Added 1 test verifying model param correctly overrides the model passed to the child session and prompt payload.

How did you verify your code works?

cd packages/opencode
bun test test/tool/task.test.ts   # 8 pass, 0 fail, 28 expect() calls
bun test test/permission/          # 85 pass, 0 fail, 130 expect() calls
bun typecheck                      # clean
bun run build                      # succeeds

Behavior change for users

Purely additive. The model parameter is optional and requires explicit permission. When omitted or denied, behavior is identical to before -- subagents inherit their model from agent config or the parent session.

Checklist

I have tested my changes locally
I have not included unrelated changes in this PR

Hey! Your PR title feat(tool/task): add model parameter to override subagent model doesn't follow conventional commit format.

Please update it to start with one of:

feat: or feat(scope): new feature
fix: or fix(scope): bug fix
docs: or docs(scope): documentation changes
chore: or chore(scope): maintenance tasks
refactor: or refactor(scope): code refactoring
test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found several related but older PRs that addressed similar features:

Potentially Related (Historical):

PR feat(task): add model override for subagents #18528 - feat(task): add model override for subagents - This appears to be a prior implementation of the same feature
PR feat: add assign-model feature for subagent model selection #17570 - feat: add assign-model feature for subagent model selection - Earlier model selection approach
PR feat(agent): implement model tier selection with variant support for subagents #11377 - feat(agent): implement model tier selection with variant support for subagents - Related model routing functionality
PR feat(task): allow @agent:provider/model model overrides #11217 - feat(task): allow @agent:provider/model model overrides - Similar override syntax

These are merged/closed PRs from the repository's history, so the current PR (26535) is not a duplicate of open PRs. However, you may want to verify:

Whether the new implementation in PR feat(opencode): add model parameter to task tool for subagent model override #26535 builds on or supersedes the approach in PR feat(task): add model override for subagents #18528
If there's a reason these prior implementations existed but the feature is being re-added now

No open duplicate PRs found - The current PR is not duplicating any actively open pull requests.

Thanks for updating your PR! It now meets our contributing guidelines. 👍

Pull request overview

Adds an optional model parameter to the task tool so callers can override which model a spawned subagent uses (taking priority over the agent’s configured model and the parent message/session model), and documents + tests the new behavior.

Changes:

Extend TaskTool parameters with optional model in provider/model format and apply it during subagent session/prompt creation.
Document “Model selection” for the task tool.
Add a test asserting the override propagates into the child session metadata and the prompt payload.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/opencode/src/tool/task.ts	Adds model param and uses it to resolve the subagent model via Provider.parseModel() before falling back to agent/parent model.
packages/opencode/src/tool/task.txt	Documents the new model parameter and intended usage.
packages/opencode/test/tool/task.test.ts	Adds a test verifying model overrides the model used for the child prompt + returned metadata.

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…verride Adds an optional model parameter to the task tool that overrides which model a subagent uses. Format: provider/model (e.g. anthropic/claude-sonnet-4). Model priority: params.model > agent config > parent session model. The model_override permission is denied by default, requiring users to opt in via config (e.g. model_override: { anthropic/*: allow }). This prevents prompt injection from escalating to expensive models. Closes anomalyco#17595

Thanks for putting this together — this is exactly the behavior I was looking for as an opencode user. I tested a small local version of the same idea and confirmed the Task tool model parameter works well for orchestrator-driven subagent routing.

I took a look at why this seems stuck. GitHub currently reports the PR as conflicted/dirty against dev — the branch is far behind current dev, and the conflicts are mostly around the newer Task implementation/background-subagent code.

A few concrete notes from porting this locally onto current dev:

Keep the lightweight ModelID / ProviderID parsing approach from this PR rather than importing the full provider module.
Keep early provider/model validation before any permission prompt.
Ask model_override before the normal task permission prompt. Otherwise a user can approve/persist a task permission before the default-denied model override fails.
I suggest exact-model always scope, e.g. always: [modelOverride], rather than provider-wide anthropic/*, for least privilege. Provider-wide allow can still be configured explicitly by the user in config.
Additional useful tests: explicit override precedence, subagent-model fallback, parent-model fallback, invalid model rejected before asks, and model_override ask ordering before task.

I have a clean local port of this onto current dev with those tweaks if that would help. Validation I could run locally: git diff --check and lightweight Bun build checks for the touched files passed; full bun test/typecheck were blocked in my local checkout by missing @opentui/solid/preload and tsgo.

I opened a refreshed forward-port at #29447 to help unblock maintainers since this branch is conflicted/far behind dev.

I credited this PR and @funkybooboo in the new PR body and kept the same core design: optional Task model, model_override permission, early provider/model validation, and explicit model > subagent model > parent model precedence. I also included the permission-ordering/test coverage notes from my local port.

Happy to close mine if this branch gets refreshed first — mostly trying to move the existing work over the line.

@kobicovaldev thank you for keeping the work moving! I love what you have done and am happy to close this PR!

Copilot AI review requested due to automatic review settings May 9, 2026 15:46

github-actions Bot added the needs:title label May 9, 2026

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Copilot started reviewing on behalf of funkybooboo May 9, 2026 15:47 View session

funkybooboo changed the title feat(tool/task): add model parameter to override subagent model feat(opencode): add model parameter to task tool for subagent model override May 9, 2026

funkybooboo mentioned this pull request May 9, 2026

feat(opencode): add model parameter to task tool for subagent model override #26536

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github-actions Bot removed needs:compliance This means the issue will auto-close after 2 hours. needs:title labels May 9, 2026

Copilot AI reviewed May 9, 2026

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Comment thread packages/opencode/src/tool/task.ts Outdated

Comment thread packages/opencode/src/tool/task.ts Outdated

funkybooboo force-pushed the feat/task-model-override branch from cae2d8d to bf6215a Compare May 9, 2026 16:28

funkybooboo mentioned this pull request May 9, 2026

[FEATURE]: Runtime model override for task tool subagents #17595

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kobicovaldev mentioned this pull request May 26, 2026

feat(opencode): add task model override #29447

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funkybooboo closed this May 28, 2026

github-actions Bot mentioned this pull request May 28, 2026

📊 AI CLI 工具社区动态日报 2026-05-28 ivanweng2077/big_model_radar#101

Open

leoncheng57 mentioned this pull request Aug 26, 2026

feat(task): allow selecting a model per task invocation (1.18.23 lineage) leoncheng57/opencode#4

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feat(opencode): add model parameter to task tool for subagent model override by funkybooboo · Pull Request #26535 · anomalyco/opencode · GitHub

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feat(opencode): add model parameter to task tool for subagent model override by funkybooboo · Pull Request #26535 · anomalyco/opencode · GitHub

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feat(opencode): add model parameter to task tool for subagent model override - #26535

feat(opencode): add model parameter to task tool for subagent model override#26535funkybooboo wants to merge 1 commit intoanomalyco:devanomalyco/opencode:devfrom funkybooboo:feat/task-model-overridefunkybooboo/opencode:feat/task-model-overrideCopy head branch name to clipboard

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How did you verify your code works?

Behavior change for users

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