opencode attach --mini ignores --agent/--model flags

[Ron-RONZZ-org]

Description

opencode attach --mini silently ignores the --agent (and --model) flags. Mini-mode sessions started against a shared server always use the server's default agent (typically "build"), with no way to select a different agent.

Root Cause

Two-part bug in packages/opencode/src/cli/cmd/attach.ts:

1. Missing yargs options

The attach subcommand's builder does not define --agent or --model, so with strict mode they're rejected as unknown options:

// Current builder — no --agent, no --model
.option("dir", { ... })
.option("continue", { ... })
.option("mini", { ... })
// ...

2. Missing parameter pass-through to runMini()

Even if args.agent / args.model were available, attach.ts does not forward them:

// Current — agent, model, prompt NOT forwarded
await runMini({
    attach: args.url,
    directory,
    password: args.password,
    username: args.username,
    continue: args.continue,
    session: args.session,
    fork: args.fork,
    replay: noReplay ? false : undefined,
    replayLimit: args.replayLimit,
})

Compare with tui.ts (the $0 default command, which handles opencode --mini) which forwards all three correctly:

// tui.ts — correct, forwards agent/model/prompt
await runMini({
    directory: ...,
    model: args.model,
    agent: args.agent,
    prompt: args.prompt,
    ...
})

Downstream consequence

• runMini() → RunCommand.handler() → pickAgent(client) returns undefined (because args.agent is never set)
• runInteractiveMode() is called with agent: undefined
• The session runs with whatever agent the server assigned at creation time (the server's own default_agent)
• Users cannot override it via OPENCODE_CONFIG_CONTENT either — that env var is client-side only and does not affect the server's session creation API

Related: also missing --model and --prompt

The same omission affects --model and --prompt — they are defined globally and used by tui.ts, but not forwarded from attach.ts.

Fix

File: packages/opencode/src/cli/cmd/attach.ts

1. Add options to builder (after the existing .option("replay-limit", ...) line):

.option("model", {
  type: "string",
  describe: "model to use in the format of provider/model",
})
.option("agent", {
  type: "string",
  describe: "agent to use",
})

2. Forward to runMini() (add three fields to the existing object literal):

await runMini({
    attach: args.url,
    directory,
    password: args.password,
    username: args.username,
    continue: args.continue,
    session: args.session,
    fork: args.fork,
    model: args.model,
    agent: args.agent,
    prompt: args.prompt,
    replay: noReplay ? false : undefined,
    replayLimit: args.replayLimit,
})

That's it. The downstream types (MiniCommandInput in run.ts and all handler code) already accept these fields — they just never received them from the attach path.

Impact

• opencode attach http://localhost:4096 --mini --agent gitmaster now works
• opencode attach http://localhost:4096 --mini --model openai/gpt-4 now works
• No regressions: passing undefined for these fields (when omitted) is identical to current behavior