house / Midjourney Iteration

---
name: midjourney-iteration
description: Iterate on Midjourney prompts in a closed loop — generate, vision-evaluate the result grid against a structured brief, refine the prompt, re-roll — when a user wants album art, music video stills, social-post imagery, or any other MJ output that benefits from autonomous taste-driven iteration rather than one-shot prompting.
license: MIT
tags: [midjourney, image-generation, social-assets, browser-hand, design, iteration, social]
agents: [claude-code, codex, autojack]
category: design
metadata:
  version: "0.1.0"
capabilities:
  network: true
  filesystem: readwrite
  tools: [Bash, Read, Write, Edit]
requires-secrets: []
resources:
  - path: story.md
    type: file
  - path: workflow.md
    type: file
  - path: brief-schema.md
    type: file
  - path: eval-rubric.md
    type: file
  - path: refine-patterns.md
    type: file
  - path: examples/product-hero.brief.json
    type: file
  - path: bin/preflight
    type: file
  - path: bin/relaunch-chrome
    type: file
bin:
  preflight:
    command: bin/preflight
    description: Verify Browser Hand's remote-debug fallback, Chrome CDP on port 9222, and a logged-in midjourney.com tab.
    requires-tty: true
---

Midjourney Iteration

Drive Midjourney through a closed-loop generate → vision-evaluate → refine → re-roll cycle, attached to the user's existing logged-in Chrome session. Returns the top picks with the prompts that produced them, plus a session log.

When to use

• The user is working on cover art, music-video stills, IG posts, mood-board pieces, or any MJ output where one-shot prompting won't get them to the brief.
• The user describes a brief that has taste constraints worth iterating on (composition, palette, negatives) — not just "make me a picture of X."
• The user asks to "iterate on a Midjourney prompt", "find a generation that hits the brief", or "run an MJ loop until it lands."
• A written creative brief is available, including the intended subject, composition, style, and constraints.

When NOT to use

• One-shot generations the user can do faster manually.
• Tasks that need the user's subjective taste in real time — this skill is for unattended iteration with a clear written brief.
• Anything that requires scraping other artists' work or downloading from /explore.
• Continuous farms / 24-7 generation loops. This skill is for bursty creative sessions only.
• Divergent / discovery phases. This skill converges on ONE composition described by a structured brief. If the user is still trying to figure out the broad creative direction (e.g., "explore 5 different concepts for this character"), they need a different shape: 1 round per prompt across N varied prompts, then the agent reports which directions hit. That mode is on the roadmap (see roadmap section in refine-patterns.md), not yet implemented as a separate orchestration path. For now, run multiple briefs serially or work outside the skill until divergent-mode lands.

Prerequisites

• Load browser-hand and use its documented remote-debug fallback. That implementation currently requires the upstream dev-browser CLI (npm install -g dev-browser and dev-browser install).
• Google Chrome launched with --remote-debugging-port=9222 AND --user-data-dir=<non-default path> and a logged-in midjourney.com tab. The skill attaches to that tab via Chrome DevTools Protocol — no Chrome extension is involved despite older docs that mention one.
  • The --user-data-dir is REQUIRED on Chrome 136+ (May 2025): Chrome silently ignores --remote-debugging-port on the default profile as a security hardening. bin/relaunch-chrome provisions a dedicated profile under the user state directory; the user signs in there once and the profile persists across sessions.
• bin/preflight verifies all three. If Chrome isn't on the debug port, it prints the relaunch command and follows MJ_ITER_BROWSER_MODE=prompt|never|always.

Why Browser Hand's remote-debug fallback specifically

Cloudflare bot-detection on Midjourney passes a real Chrome with the user's real session/fingerprint and rejects fresh Playwright/Chromium. CDP-attaching to user-Chrome is load-bearing — do not "simplify" by switching to plain Playwright.

Workflow

1. Run preflight

bin/preflight

Exit non-zero means stop and surface the remediation message. Do not try to work around a missing Chrome debug port by spawning a fresh browser — see "Why Browser Hand's remote-debug fallback specifically".

2. Load the brief

Briefs are structured JSON — see brief-schema.md for the full shape. At minimum: subject, composition, style, negative. Optional: palette, references, max_rounds (default 8), starting_prompt, and output_dir.

If the user passed a prose brief, convert it to the structured shape first and confirm with them before running the loop.

Session output location. Resolve the session-log dir from brief.output_dir once at the start of the run:

• If output_dir is set: <output_dir>/<timestamp>-<slug>/
• Otherwise: ${XDG_STATE_HOME:-$HOME/.local/state}/midjourney-iteration/<timestamp>-<slug>/

Use that path for every subsequent round's prompt file, screenshot copy, eval-notes.jsonl, and picks.json. The Chrome user-data-dir is independent and set by MJ_ITER_CHROME_PROFILE_DIR.

3. Attach to the Midjourney tab

dev-browser --connect <<'EOF'
const tabs = await browser.listPages();
const mj = tabs.find(t => t.url && t.url.includes('midjourney.com'));
if (!mj) { console.error('NO_MJ_TAB'); throw new Error('Open midjourney.com in Chrome and sign in.'); }
const page = await browser.getPage(mj.id);
console.log(JSON.stringify({ id: mj.id, origin: new URL(mj.url).origin }));
EOF

The page is now attached through Browser Hand's low-level fallback; subsequent invocations re-attach the same mj.id.

4. Run rounds

Each round is three separate low-level dev-browser --connect invocations because a single MJ generation takes 45–90s and the fallback's per-script timeout caps at 120s. See workflow.md for the verbatim three-script contract.

For each round:

a. Submit prompt. Use page.snapshotForAI() to find the prompt textarea and Generate button (cheap accessible-tree read). Paste the prompt, click Generate.

b. Wait for grid. Loop page.waitForSelector(<grid-selector>, { timeout: 80000 }) until the 4-image grid renders.

c. Screenshot the grid. await saveScreenshot(buf, 'round-N.png') — returns a path inside ~/.dev-browser/tmp/. Copy that file into the session log directory (see step 6).

5. Vision-evaluate the grid

Load the screenshot. Score each of the 4 images against eval-rubric.md. Record per-image hit/miss plus the dominant failure mode.

A round wins if ≥2 of the 4 images pass the rubric.

6. Decide: continue, refine, or stop

• Stop early if this round won AND total accumulated hits ≥3.
• Stop hard if round_index >= brief.max_rounds.
• Otherwise refine. Match the dominant failure mode against refine-patterns.md, apply the prompt-edit recipe, and loop back to step 4.

After every round, append the round's prompt + screenshot path + per-image scores to <session-log-dir>/log.jsonl (or eval-notes.jsonl), where <session-log-dir> was resolved in §2 from brief.output_dir.

7. Return the top 3 picks

Sort all hit images across all rounds by rubric score; return the top 3 with:

• The prompt that produced each
• The screenshot path
• A one-line note on what made it a hit

Save the final ranking to picks.json in the session-log directory.

Output

Return a concise summary to the user:

• Rounds run, total hits, early-stop reason if any
• Top 3 picks with prompts and image paths
• Pointer to the session-log directory for full history
• Any new refine-patterns observed (so they can be appended to refine-patterns.md)

Anti-patterns

• Do not scrape other artists' work or download from /explore. This skill is for the user's own generations only.
• Do not run continuous generation farms — bursty iteration sessions only. ToS-safe is what humans do during creative work.
• Do not open Chrome without printing the relaunch command first. bin/preflight and bin/relaunch-chrome honor MJ_ITER_BROWSER_MODE; the agent should not bypass that.
• Do not skip the vision evaluation step. If you can't load the screenshot for any reason, stop the loop and report — never keep firing prompts blind.
• Do not add a project, artist, or client aesthetic to the base rubric. Keep those constraints in the user-provided brief.
• Do not swap Browser Hand's CDP fallback for fresh Playwright/Chromium. Cloudflare blocks it and MJ won't be logged in. The CDP attach is load-bearing.
• Do not try to fold the three per-round invocations into one script. The fallback's 120s timeout cap is real; one MJ generation often exceeds it.
• Do not auto-quit the user's running Chrome to relaunch with --remote-debugging-port=9222 — it will lose their other tabs. Print the command and ask.

Why

One prompt is a lottery ticket. A short loop with a rubric gives the taste call somewhere to stand.

How

Write the brief, attach to an already signed-in browser, score the grid, and change one thing at a time. It stops with the useful candidates and the record of how they got there.

Related

Pair it with Browser Hand for the signed-in browser and Brand Bible Author when the brief needs a backbone first.