getImageOutputDir: Support configurable image output directory via env var or config #16

Problem

getImageOutputDir() in src/plugin/image-saver.ts hardcodes the generated image output directory to ~/.opencode/generated-images/:

function getImageOutputDir(outputDir) {
    const resolved = outputDir ?? join(homedir(), '.opencode', 'generated-images');
    if (!existsSync(resolved)) mkdirSync(resolved, { recursive: true });
    return resolved;
}

There is no way to configure this path — no env var, no config option, no plugin hook on the output side.

Use Case

When using image generation subagents (e.g. task(category="image-generation")), generated images always land in ~/.opencode/generated-images/ regardless of the project context. Users working on specific projects (e.g. e-commerce product shots) need images saved directly to their project directory without manual copying after every generation.

Proposed Solution

Add process.env.OPENCODE_IMAGE_OUTPUT_DIR as a fallback before the hardcoded default:

function getImageOutputDir(outputDir) {
    const resolved = outputDir ?? process.env.OPENCODE_IMAGE_OUTPUT_DIR ?? join(homedir(), '.opencode', 'generated-images');
    if (!existsSync(resolved)) mkdirSync(resolved, { recursive: true });
    return resolved;
}

This is a one-line change that:

• Maintains full backward compatibility (env var unset = same behavior as today)
• Lets users set OPENCODE_IMAGE_OUTPUT_DIR globally or per-session
• Enables plugins to dynamically redirect output by setting process.env.OPENCODE_IMAGE_OUTPUT_DIR in the same Node.js process (since the auth plugin and local plugins share the same runtime)

Current Workaround

We patch dist/src/plugin/image-saver.js and dist/index.js (both in node_modules and the Bun cache at ~/.cache/opencode/packages/@cortexkit/opencode-antigravity-auth@latest/) via a post-install script. The patch gets overwritten on every npm install and must be re-applied manually.

Environment

• OpenCode on Windows (Bun runtime)
• @cortexkit/opencode-antigravity-auth@latest
• Node 26, Bun standalone binary

Note on Bun Cache

Bun loads the plugin from ~/.cache/opencode/packages/@cortexkit/opencode-antigravity-auth@latest/ rather than the project node_modules/, so patches to node_modules/ alone have no effect — the cache copy must also be patched. A native env var support in the source would eliminate this entirely.