[BUG]: Plugin tool context.metadata() does not publish live updates after Effect migration #37877

Description

Plugin tools cannot publish metadata while they are running.

A plugin call to context.metadata(...) does not update the running ToolPart. The metadata only becomes visible when the tool completes and returns it as part of its final structured result.

This breaks clients that use live tool metadata. For example, a foreground task plugin publishes a child sessionId before starting the child prompt. OpenChamber cannot subscribe to that child session while the task runs, so it displays Waiting for subagent activity.... Once the task completes, the returned metadata appears and the child activity becomes available.

Related issue #12527 fixed preservation of metadata in the completed result. This report concerns live context.metadata() calls not executing.

Likely cause

The internal tool context defines metadata() as an Effect:

The public plugin context defines it as a synchronous void function:

In fromPlugin(), OpenCode bridges the Effect-based ask() method to a Promise, but spreads the Effect-based metadata() method into the plugin context without executing it:

const bridge = yield* EffectBridge.make()
const pluginCtx: PluginToolContext = {
  ...toolCtx,
  ask: (req) => bridge.promise(toolCtx.ask(req)),
  directory: ctx.directory,
  worktree: ctx.worktree,
}

At runtime, context.metadata(input) returns an Effect that the plugin API caller cannot observe or execute.

A possible bridge is:

const pluginCtx: PluginToolContext = {
  ...toolCtx,
  ask: (req) => bridge.promise(toolCtx.ask(req)),
  metadata: (input) => {
    bridge.fork(toolCtx.metadata(input))
  },
  directory: ctx.directory,
  worktree: ctx.worktree,
}

Steps to reproduce

Create a plugin tool:

import { tool } from "@opencode-ai/plugin"

export default tool({
  description: "Test live plugin metadata",
  args: {},
  async execute(_input, context) {
    context.metadata({
      title: "Running",
      metadata: { phase: "running" },
    })

    await new Promise((resolve) => setTimeout(resolve, 5000))

    return {
      title: "Done",
      metadata: { phase: "done" },
      output: "done",
    }
  },
})

1. Invoke the tool.
2. Inspect the ToolPart during the five-second delay.
3. Observe that the title and metadata are not updated.
4. Wait for completion.
5. Observe that the final returned title and metadata appear.

Expected behavior

context.metadata() updates the running ToolPart immediately, matching the public plugin API contract.

Actual behavior

The running ToolPart remains pending without the supplied metadata. Only metadata returned in the completed structured result appears.

OpenCode version

1.18.3

The same unbridged implementation exists in 1.18.2 and the current dev branch.

Client

OpenChamber 1.16.2, using live state.metadata.sessionId to display foreground subagent activity.

Operating system

Linux

Terminal

N/A