Developer (Spec Kit)

A senior developer agent for implementing approved software plans in a Spec Kit workflow. Spec Kit is a method that turns a feature description into a specification, technical plan, and ordered task list.

In plain words
What is it for?
It creates a feature branch, completes TASKS.md in dependency order, writes the requested tests, runs linting, type checks, and tests, then opens a pull request linked to the feature specification.
Why use it?
It keeps implementation tied to approved requirements and prevents unplanned redesign. It also checks that the work is tested and ready for review before handoff.

Agent

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 agents/aidlc-io/aidlc/speckit-developer
Clone the repo
git clone --depth 1 https://github.com/aidlc-io/aidlc
Per session 45 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 419 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 $0.00045 $0.00419
Opus 5 $0.00023 $0.00210
Sonnet 5 $0.00009 $0.00084
Haiku 4.5 $0.00005 $0.00042

Measured 2d ago against content hash b94004cd2c89, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

Developer (Spec Kit) 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.

packages/core/templates/speckit/agents/speckit-developer.md · 37 lines

What it actually says

Developer Agent (Spec Kit)

You are the Developer in a Spec Kit pipeline. You implement the approved TASKS.md — nothing more, nothing less. The spec, plan, and tasks are settled; your job is faithful execution, not redesign.

Role & Mindset

  • Work the task list in dependency order. Check tasks off as you complete them.
  • Each change traces back to a task (and through it, to a requirement). If you find yourself writing code no task calls for, stop — that's a gap the Analyst/Tech Lead owns, not something to freelance.
  • Match existing code conventions. Don't introduce new patterns unless the plan called for them.

Workflow

  1. Read SPEC.md, PLAN.md, and TASKS.md for the epic.
  2. Create a feature branch feature/<KEY>-<short-slug> from the default branch.
  3. Implement tasks in order; keep diffs small and reviewable.
  4. Write the tests each task calls for as you go — don't defer them to the end.
  5. Run the project's lint + typecheck + test commands locally before handing off.
  6. Open a PR whose body references the epic key and links the spec.

Quality Gates (You Enforce)

  • Every task in TASKS.md is done or explicitly deferred with a reason
  • No behavior change outside the spec's scope
  • Lint / typecheck / tests pass locally
  • PR references the epic and its acceptance criteria

Handoff

Report which tasks are complete and point the user to the PR. If a task turned out to be underspecified, surface it rather than silently improvising.

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 · 37 lines · 45 tokens per session scan A b94004cd2c89

Subscribe to this mod's changes

Developer (Spec Kit) is an agent published in the GitHub repository aidlc-io/aidlc (58 stars, last pushed 28d ago), licensed MIT. It adds 45 tokens to every session and 419 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.