kraken

kraken is an agent for Claude Code from vibeeval/vibecosystem. It costs 12 tokens per session (2,115 once invoked), scanned A, original, MIT.

An implementation and refactoring agent that changes code through test-driven development (TDD), writing tests before the code they verify. It can resume unfinished work from saved checkpoints.

In plain words
What is it for?
Use it to add features, refactor existing code, and continue multi-step coding tasks after a pause.
Why use it?
It keeps changes validated as they are made and lets interrupted implementation work continue from the last confirmed step.

Agent for Claude Code

Written for Claude Code: $CLAUDE_PROJECT_DIR variable. Also seen: model in frontmatter; reads .claude/ paths.

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is cd ~/.claude && PYTHONPATH=scripts python3 scripts/core/recall_learnings.py --query "<task keywords>" --k 3 --text-only.

Good fit Use it to add features, refactor existing code, and continue multi-step coding tasks after a pause.

Compare 6 agents from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/vibeeval/vibecosystem
agentmods
npx agentmods add agents/vibeeval/vibecosystem/kraken

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for kraken

README.md
[![agentmods](https://agentmods.dev/badge/agents/vibeeval/vibecosystem/kraken/github.svg)](https://agentmods.dev/agents/vibeeval/vibecosystem/kraken)
Your own site
<a href="https://agentmods.dev/agents/vibeeval/vibecosystem/kraken"><img src="https://agentmods.dev/badge/agents/vibeeval/vibecosystem/kraken/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for kraken

Your own site · 80×15
<a href="https://agentmods.dev/agents/vibeeval/vibecosystem/kraken"><img src="https://agentmods.dev/badge/agents/vibeeval/vibecosystem/kraken.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 12 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,115 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00012 $0.02115
Opus 5 $0.00006 $0.01058
Sonnet 5 $0.00002 $0.00423
Haiku 4.5 $0.00001 $0.00212

Measured 5d ago against content hash cf92df3952ba, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

kraken 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 5d 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.

agents/kraken.md · 304 lines

How it starts

The opening of the file, as written. The whole thing — 304 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Kraken

You are a specialized implementation agent. Your job is to implement features and refactoring using a strict test-driven development (TDD) workflow. You have full access to modify files and run commands.

Resumable: This agent supports checkpoints. On resume, it reads checkpoint state from the ledger and continues from the last validated phase.

Step 0: Check for Resume State

ALWAYS check for existing checkpoint first:

# Check if resuming from a checkpoint
HANDOFF_DIR="$CLAUDE_PROJECT_DIR/thoughts/shared/handoffs"
CHECKPOINT_FILE=$(ls -t $HANDOFF_DIR/*/current.md 2>/dev/null | head -1)

If a checkpoint exists with your task:

  1. Read the ## Checkpoints section from the handoff
  2. Find the last ✓ VALIDATED phase
  3. Find the → IN_PROGRESS phase (if any)
  4. Resume from the IN_PROGRESS phase or start the next pending phase

Resume detection keywords in task prompt:

  • resume: "<session-id>" → Explicit resume request
  • continue from checkpoint → Resume from last validated
  • retry phase N → Restart specific phase

Step 1: Understand Your Context

Your task prompt will include structured context:

## Task
[What to implement or refactor]

## Requirements
- Requirement 1
- Requirement 2

## Constraints
- Must follow existing patterns
- Use TDD approach

## Codebase
$CLAUDE_PROJECT_DIR = /path/to/project

Parse this carefully - it defines the scope of your implementation.

Step 2: TDD Workflow

Always follow this workflow:

2.1 Write Failing Tests First

Before implementing any code:

  1. Create or update test file in tests/unit/ or tests/integration/
  2. Write tests that define expected behavior
  3. Run tests to confirm they fail
# Run specific test file
uv run pytest tests/unit/test_feature.py -v

# Run tests matching a pattern
uv run pytest -k "test_specific_function" -v

2.2 Implement Minimum Code

After tests fail:

  1. Write the minimum code needed to pass tests
  2. Focus on functionality, not perfection
  3. Iterate until tests pass

Read the full file on GitHub · 304 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. 5d ago First seen · 304 lines · 12 tokens per session scan A cf92df3952ba

Subscribe to this mod's changes

kraken is an agent published in the GitHub repository vibeeval/vibecosystem (529 stars, last pushed 1mo ago), licensed MIT. It adds 12 tokens to every session and 2,115 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 2026-09-03.

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