opencode-aside

A port of Claude Code's /btw for opencode: ask a question about the session you are in, get the answer in an overlay, and have none of it enter the transcript.

The command is /btw, with /aside as an alias. The package is named opencode-aside because opencode-btw is taken by an unrelated package.

How this differs from the alternatives

Several plugins cover nearby ground. The distinction that matters is whether your side question forks a session and whether anything persists:

	Forks?	Persists?	Tools?
opencode-aside (this)	no	no — the child session is deleted	no
opencode-bytheway	yes, forks and switches you into it	until you /btw-end or /btw-merge	yes
opencode-sidechat	no	yes — a panel with history	yes

Claude Code's own /btw is a side chain: no tools, nothing persisted, gone when you close it, main transcript untouched. This plugin matches that. Pick bytheway if you actually want to branch and merge text back; pick sidechat if you want a persistent panel.

Install

// ~/.config/opencode/tui.json
{ "plugin": ["opencode-aside"] }

Restart opencode afterwards.

What it does

/btw opens a dialog, then:

1. snapshots recent text and tool activity from the current session
2. opens a hidden child session (parentID = current) with tools denied
3. asks once and renders the answer in an overlay
4. deletes the child session

The parent transcript is never written to.

It deliberately does not fork. Forking is the heavyweight case — use a real fork when you want to branch, use /btw when you just want to ask.

Options

{ "plugin": [["opencode-aside", { "context_chars": 12000 }]] }

Option	Default	Meaning
context_chars	6000	How much recent transcript text to include. Trimmed from the front, so the tail always survives.
tool_chars	600	Per-tool-call cap on command + output text.
system	see source	Override the side-question system prompt.
model	session's model	{providerID, modelID} to answer with.

Notes for anyone extending it

• opencode's slash mechanism dispatches commands with no arguments (dispatchCommand(name)), so /btw your question is impossible. Hence the dialog.
• Most of a session lives in tool parts, not text parts. A shell-mode (!cmd) session's only text part is synthetic: true boilerplate; the real content is part.state.input / part.state.output. Reading only text parts yields empty context.
• api.ui.DialogPrompt / DialogAlert can be called as plain functions inside dialog.replace(() => …), which avoids needing a JSX build step.
• Tools are disabled with tools: { "*": false }, which opencode turns into deny-all permission rules for the child session.
• The model is inherited from the session's most recent assistant message, which matters on a swap-based backend where naming a different model forces a reload.

Running against a local single-slot model

Irrelevant on a hosted API. On a local llama.cpp-style server with --parallel 1, requests serialise, so a /btw is served as soon as the current in-flight call finishes — usually in the gap while the agent runs tools — rather than waiting for the whole run. It delays the agent's next call by its own duration and will not preempt a generation already in flight.

Measured on one such setup, an interleaved /btw did not cost the agent its prompt cache (a long prompt still hit cache afterwards: 1.1s, versus 9.5s cold). That depends on server version and cache settings, so re-check it on your own hardware if it matters.

Requirements

OpenCode 1.18.18 or newer (the TUI plugin API with dialogs and session client access).