---
llm: google/gemini-3.1-pro-preview
status: draft
---

# Multi-model git worktree support plan

## Goal

Enhance the `multi-model` tool to:
1. Create a unique git worktree for each session + modelName.
2. Store worktree folders inside `~/.local/share/opencode/multi-model/<sessionName>/<windowName>`.
3. Initialize `opencode` with that specific worktree to avoid conflicts.

## Implementation Details

- **Target file:** `.opencode/tools/multi-model.ts`
- **Path Sanitization:**
  - Sanitize `sessionName` (e.g., replace non-alphanumeric with hyphens) to ensure safe paths and branch names. `windowName` is already sanitized by existing code.
- **Worktree Path Construction:**
  - `worktreePath`: `~/.local/share/opencode/multi-model/<sanitizedSessionName>/<windowName>`.
- **Git Repository Check:**
  - Run `git rev-parse --is-inside-work-tree` at the start of `execute`.
  - If false, gracefully fail with an error `multi-model requires a git repository`.
- **Creating Worktrees:**
  - Iterate through `windowPlans` to create tmux windows:
    - Generate `worktreePath`.
    - Generate `branchName` as `opencode/<sanitizedSessionName>/<windowName>`.
    - Handle edge cases (Fail Fast approach):
      - Run `fs.existsSync(worktreePath)` to check if the path exists. If it does, fail fast with an error indicating the path collision.
      - Run `git show-ref --verify --quiet refs/heads/<branchName>` to check if the branch exists. If it does, fail fast with an error indicating the branch collision.
    - Run `git worktree add -b <branchName> <worktreePath>` to create the new branch and worktree.
  - In `tmux new-session` and `tmux new-window`, pass the newly created `worktreePath` to the `-c` argument instead of `context.directory`.
- **Cleanup Strategy:**
  - On launch failure: If `tmux` or `opencode` launch fails *after* worktree creation, run `git worktree remove -f <worktreePath>` and `git branch -D <branchName>`. Keep track of successful and failed cleanups (undos) and report them in the tool output if the undo process fails.
  - On success: Output a command snippet to the user on how to clean up the session's worktrees and branches when done:
    `rm -rf ~/.local/share/opencode/multi-model/<sanitizedSessionName> && git worktree prune && git branch -d $(git branch --format='%(refname:short)' --list 'opencode/<sanitizedSessionName>/*')`

## Non-obvious Code Blocks

**Path Sanitization & Generation (Example):**
```ts
import * as os from "node:os";
import * as path from "node:path";
import * as fs from "node:fs";

function sanitizeName(name: string): string {
  return name.replace(/[^a-zA-Z0-9_-]/g, "-").replace(/-+/g, "-").replace(/^-|-$/g, "");
}

function getWorktreePath(safeSession: string, windowName: string): string {
  return path.join(os.homedir(), ".local/share/opencode/multi-model", safeSession, windowName);
}
```

**Creating Worktree (Example):**
```ts
const safeSession = sanitizeName(sessionName);
const branchName = `opencode/${safeSession}/${plan.windowName}`;

if (fs.existsSync(worktreePath)) {
  return `Error: Worktree path already exists at ${worktreePath}. Clean it up first.`;
}

const branchExists = await runCommand(["git", "show-ref", "--verify", "--quiet", `refs/heads/${branchName}`]);
if (branchExists.ok) {
  return `Error: Branch '${branchName}' already exists.`;
}

const worktreeCmd = ["git", "worktree", "add", "-b", branchName, worktreePath];
const result = await runCommand(worktreeCmd);

if (!result.ok) {
  return `Error: Failed to create worktree for ${plan.model}: ${result.stderr}`;
}
```

**Cleanup on Failure (Example):**
```ts
async function undoWorktree(worktreePath: string, branchName: string): Promise<string[]> {
  const errors: string[] = [];
  const removeRes = await runCommand(["git", "worktree", "remove", "-f", worktreePath]);
  if (!removeRes.ok) errors.push(`Failed to remove worktree ${worktreePath}: ${removeRes.stderr}`);
  
  const branchRes = await runCommand(["git", "branch", "-D", branchName]);
  if (!branchRes.ok) errors.push(`Failed to delete branch ${branchName}: ${branchRes.stderr}`);
  return errors;
}
```