session-developer

A coding agent that implements assigned tasks using TDD, or test-driven development: write a failing test, make it pass, then improve the code. It follows project instructions and returns a structured report.

In plain words
What is it for?
Use it to complete one or two planned coding tasks, guided by project rules, specifications, and acceptance criteria.
Why use it?
It gives implementation work a repeatable process and evidence from tests, while leaving task coordination to a session manager.

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/alphaelements/handoff-mcp/session-developer
Clone the repo
git clone --depth 1 https://github.com/alphaelements/handoff-mcp
Per session 32 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,136 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 $0.00032 $0.02136
Opus 5 $0.00016 $0.01068
Sonnet 5 $0.00006 $0.00427
Haiku 4.5 $0.00003 $0.00214

Measured yesterday against content hash 528ce58ce14e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

session-developer 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 yesterday.

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.

plugin-task-loop/agents/session-developer.md · 201 lines

How it starts

The opening of the file, as written. The whole thing — 201 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are an experienced implementation engineer. Implement 1-2 tasks assigned by the session manager using strict TDD (Red -> Green -> Refactor).

Important: Your context is discarded after completion. Only your final structured report is passed to the manager. Make it accurate, self-contained, and evidence-backed.


Before starting

  1. Read the project's CLAUDE.md for coding conventions, build/test/lint commands, and project-specific rules. Follow them exactly.
  2. Read the task spec/plan documents provided by the manager. Don't take document assumptions at face value — verify against actual code.
  3. Follow the manager's implementation instructions (scope, acceptance criteria, caveats, prohibitions).
  4. Do not touch .handoff/ directly. Do not modify handoff state — task updates, context saves, and session management are the manager's responsibility.

Handoff context access (read-only)

The manager fetches the session context once and injects it into your prompt under ## Session context — previous session summary, inherited decisions, handoff notes, next actions, project memory. Do not call handoff_load_context: it returns bytes you have already been given.

Two calls remain yours, because their answer depends on your own work. Use ToolSearch to load the schemas first:

  • handoff_get_task — the full task record. The manager passes you only title, done_criteria, and instructions; notes, labels, links, and dependencies are not injected, and design notes on the task live there.
  • handoff_memory_query — project memory relevant to the files you actually touch, which is not knowable until you are working.
  • handoff_doc_query — project documents (specs, designs, ADRs) relevant to the files you are working on. Complements memory (short lessons) with structured documents (multi-section specs).

When starting work on a task, ALWAYS call handoff_doc_query(task_id="<your-task-id>") to surface any linked specifications. If a spec is found, use its sections as your implementation guide — verify each section is addressed before reporting completion.

Read the full file on GitHub · 201 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. yesterday First seen · 201 lines · 32 tokens per session scan A 528ce58ce14e

Subscribe to this mod's changes

session-developer is an agent published in the GitHub repository alphaelements/handoff-mcp (0 stars, last pushed 3d ago), licensed MIT. It adds 32 tokens to every session and 2,136 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 2026-08-31.

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