specmanager-design

A command that creates high-fidelity HTML screen mockups for a SpecManager feature using a designer subagent. It checks whether the feature is ready and whether a design draft already exists before creating one.

In plain words
What is it for?
Use it to design feature screens from an approved PRD, with optional architecture and screenshot context.
Why use it?
It provides a visual design stage for a feature before planning can proceed, while avoiding duplicate drafts.

Command

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add commands/joanseg/specmanager/specmanager-design
Clone the repo
git clone --depth 1 https://github.com/joanseg/specmanager
Per session 44 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 726 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00044 $0.00726
Opus 5 $0.00022 $0.00363
Sonnet 5 $0.00009 $0.00145
Haiku 4.5 $0.00004 $0.00073

Measured 2d ago against content hash ec3aad513f8c, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

specmanager-design scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/specmanager/commands/specmanager-design.md · 30 lines

How it starts

The opening of the file, as written. The whole thing — 30 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Design the screens for the feature: $ARGUMENTS.

Steps

  1. Resolve the feature. Call list_features. Find the feature whose id or slug matches the first whitespace-separated token of the argument. If none match, ask the user to clarify and stop. (Anything after the first token is treated as extra context to forward to the subagent.)

  2. Check the gate. Call check_gate({ featureId, stage: "design" }). The design gate is open once the PRD is approved (Architecture is NOT required — design can run in parallel with Architecture). If closed, report reason and stop.

  3. Confirm no draft already exists. list_documents({ featureId, stage: "design" }). If a doc exists, point the user at the panel to edit, or delete the file before regenerating. Don't duplicate.

  4. Look up PRD and Architecture ids to pass into the subagent prompt. list_documents({ featureId, stage: "prd" }) and list_documents({ featureId, stage: "architecture" }). Architecture may be absent or in draft — pass null if so.

  5. Collect attachments. If the user pasted screenshot paths in the conversation before invoking the command, list them — the designer uses them as visual reference and may inline them as data URIs. If no attachments, the designer works from the PRD + DESIGN.md alone. Optional design reference (R5/AC7): when docs/DESIGN.md holds only placeholder/# TODO tokens, the designer may invite an optional design reference (a screenshot/example through this same attachment path) to ground a synthesized token system — always optional, never required; the designer proceeds and synthesizes if none is given.

  6. Invoke the subagent. Use the Task tool with subagent_type: "designer" and a prompt that includes:

    • The feature id, title, and slug.
    • The PRD id + version.
    • The Architecture id + version (if any).
    • The screenshot paths the user attached (if any).
    • Any extra context the user gave after the feature id.

    The designer reads the upstream docs and ./docs/DESIGN.md, designs the actual screens as one self-contained HTML file (high-fi mockups stacked with explanatory notes between them), and calls create_design_brief itself.

  7. Sync CLAUDE.md. After the subagent returns, call sync_claude_md.

  8. Report. Document id + file path (design/mockups.html). Suggest opening it in the board — the doc panel renders the stacked mockups in a sandboxed iframe preview.

Read the full file on GitHub · 30 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 30 lines · 44 tokens per session scan A ec3aad513f8c

Subscribe to this mod's changes

specmanager-design is a command published in the GitHub repository joanseg/specmanager (19 stars, last pushed 18d ago), licensed MIT. It adds 44 tokens to every session and 726 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.