spec-exec

A command that runs one task from a written software specification by asking Claude to implement it autonomously. The specification contains requirements, design, and a task list.

In plain words
What is it for?
Use it when a project has a completed specification in .claude/specs and you want Claude to implement the next pending task.
Why use it?
It connects a documented plan to one implementation cycle, including testing, updating the specification, and committing the result.

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/habib0x0/spec-driven-plugin/spec-exec
Clone the repo
git clone --depth 1 https://github.com/Habib0x0/spec-driven-plugin
Per session 14 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 476 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 $0.00014 $0.00476
Opus 5 $0.00007 $0.00238
Sonnet 5 $0.00003 $0.00095
Haiku 4.5 $0.00001 $0.00048

Measured 2d ago against content hash 7da2346b112b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

spec-exec 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.

commands/spec-exec.md · 65 lines

What it actually says

/spec-exec Command

Run a single iteration of spec-driven implementation. Claude picks the highest-priority pending task, implements it, tests it, updates the spec, and commits.

Usage

Run the script directly from your project root:

${CLAUDE_PLUGIN_ROOT}/scripts/spec-exec.sh [--spec-name <name>]

Or via Bash tool if invoked within Claude Code:

bash ${CLAUDE_PLUGIN_ROOT}/scripts/spec-exec.sh --spec-name <name>

Arguments

  • --spec-name <name> - Which spec to execute against. Auto-detected if only one spec exists in .claude/specs/.

What It Does

  1. Reads your spec files (requirements.md, design.md, tasks.md)
  2. Builds a prompt with the full spec context
  3. Runs claude --dangerously-skip-permissions -p with that prompt
  4. Claude implements one feature, tests it, updates the spec, and commits

Prerequisites

  • A completed spec in .claude/specs/<name>/ with all three files
  • Run /spec <name> first if you haven't created a spec yet

Quick Preflight

Before running a single iteration:

# 1. Verify git is configured
git remote -v | head -1

# 2. Check the build is clean
npm run build 2>&1 | tail -3

# 3. Confirm spec exists
[ -d ".claude/specs/<spec-name>" ] && echo "✓ Spec ready"

Tips

  • Run one at a time: Each exec picks ONE task. Run multiple execs to implement multiple tasks.
  • Check progress.md after each: Tells you what was completed and what's next
  • Use /spec-loop for batches: If you want to run many iterations automatically, use /spec-loop instead
  • Integration sweep runs at end: When all tasks complete, /spec-loop triggers mandatory final validation. Single /spec-exec iterations don't do this.
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 · 65 lines · 14 tokens per session scan A 7da2346b112b

Subscribe to this mod's changes

spec-exec is a command published in the GitHub repository Habib0x0/spec-driven-plugin (10 stars, last pushed 3mo ago), licensed MIT. It adds 14 tokens to every session and 476 once invoked, about $0.0001 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 2026-08-31.