Mymir

Context management for the agent-native engineering era.

        

Most of us aren't really writing code anymore, we're directing agents that do. But those agents have no memory. Every session starts from zero, and engineers end up spending their time re-explaining what was built, why decisions were made, and what still needs to happen. That's not engineering, that's babysitting.

Mymir replaces that cycle. It's not just a context layer your agents read from, it's an end-to-end project management tool that agents operate natively. Mymir creates tasks, refines them, plans implementations, provides the right context at the right stage, and tracks everything that happens. Your agent harness doesn't need a briefing. It walks into every session knowing exactly what to do next and why.

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How to set it up

You need Bun (v1.0+) and Docker for PostgreSQL.

Clone the repo and install dependencies:

git clone git@github.com:FrkAk/mymir.git
cd mymir
bun install
cp .env.local.example .env.local

Bring your own coding agent. Mymir works directly inside the coding agent you already use: Claude Code, Codex, Cursor, or Gemini CLI. Brainstorm, decompose, and project activation happen there. The web app is for refining specs, planning, and tracking progress on active projects from the browser.

Add your credentials to .env.local (see .env.local.example for the full list):

# Postgres: local Docker default; works with any connection string (Neon, Supabase, RDS)
DATABASE_URL=postgresql://mymir:mymir@localhost:5432/mymir

# Better Auth: session secret (openssl rand -base64 32) and callback origin
BETTER_AUTH_SECRET=generate-a-random-secret-at-least-32-chars
BETTER_AUTH_URL=http://localhost:3000

Spin up Postgres and push the schema:

bun run db:setup

Build and start the server and open localhost:3000:

bun run build
bun run start

Mymir ships as four standalone plugin/extension dirs, one per supported CLI under plugins/<cli>/. With the dev server running, install the one that matches your tool.

Claude Code

claude plugin marketplace add ./plugins/claude-code
claude plugin install mymir@mymir-local

Authenticate with /mcp, select mymir, and complete the browser sign-in (once per machine).

Update with claude plugin update mymir@mymir-local and restart Claude Code. MCP server changes (lib/mcp/) apply immediately without an update.

Codex

codex plugin marketplace add ./plugins

Open Codex, run /plugin, search for Mymir, install, then restart. Invoke the main skill explicitly with $mymir when needed.

Gemini

gemini extensions install ./plugins/gemini

Authenticate with /mcp auth mymir and complete the browser sign-in.

Update with gemini extensions update mymir; remove with gemini extensions uninstall mymir.

Cursor

ln -s "$(pwd)/plugins/cursor" ~/.cursor/plugins/local/mymir

Restart Cursor (or run Developer: Reload Window). The MCP server and five skills (mymir, brainstorm, decompose, manage, onboarding) load automatically. First MCP tool call triggers OAuth in your browser. Trigger a skill with /mymir, /brainstorm, etc., or let the agent auto-invoke based on your prompt.

Self-hosted: edit plugins/cursor/mcp.json to point at your deployment URL before symlinking.

What gets installed

All four plugins bundle the same components:

Component	What it does
6 MCP tools	mymir_project, mymir_task, mymir_edge, mymir_query, mymir_context, mymir_analyze
Brainstorm agent	Explore and shape a project idea through structured conversation
Onboarding agent	Reverse-engineer an existing codebase into a task graph with shipped work recorded as done
Decompose agent	Break a project into tasks with dependency edges
Manage agent	Navigate, refine, track progress, restructure
Mymir skill	Auto-invokes when conversation matches project planning

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How it runs

Mymir ships as a Next.js web app plus vendor-native plugins for Claude Code, Codex, and Gemini. Each plugin bundles 6 MCP tools, four agents (brainstorm, onboarding, decompose, manage), and a /mymir skill that auto-invokes when you talk about projects, tasks, or planning. You don't call tools manually, you just talk.

Three entry paths, one graph.

No project yet. The brainstorm agent shapes the idea with you, then decompose breaks it into a task graph:

❯ I want to build a real-time dashboard for server metrics

Existing codebase, no tracking yet. Onboarding reverse-engineers a graph from the code and git history, gated on your approval before anything is written:

❯ Onboard this existing codebase

Ongoing project. The /mymir skill detects the repo and picks up where you left off:

❯ What's the status of the project?

Skip the context briefing. Name a task or ask what's next. Mymir delivers the right bundle for that task's state, so you don't write "here's what you need to know" prompts yourself:

❯ What should I work on next?
❯ Plan and implement MYMR-101

Add and refine mid-flow. Spot something missing, describe it, and push back until it's right:

❯ Add a task for an onboarding agent that records shipped work as done tasks. Relate it to the codex/gemini support task.

❯ Priority is release-blocker, draft ACs are enough, and monorepo detection should ask the user.

Tune in the UI. Inspect edges, read execution records, and edit descriptions, ACs, tags, or dependencies directly. The agent loop and the UI write to the same store, so edits land by the next tool call.

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How it works

Instead of docs, wikis, or messy markdown files, Mymir treats project context as a live knowledge base agents can reason from.

We built Mymir around two core concepts:

Context network. A living map of your project that captures not just what was built, but why decisions were made, what was tried and abandoned, and how different parts of the codebase relate to each other.

Context retrieval interface. Four context shapes, one per job. Each is arranged by U-shaped attention (highest-recall content at the start and end) so what matters most lands where LLMs read best:

Shape	For	What's in it
summary	Quick lookup	Title, status, edge counts
working	Refining or reviewing a task	Criteria, decisions, 1-hop neighbors
planning	Writing an implementation plan	Project brief, prerequisites, upstream execution records, downstream specs
agent	Coding the task	Implementation plan, multi-hop upstream execution records, file paths, acceptance criteria

Together, they don't just inform your agent, they drive it. Mymir manages the full lifecycle: Brainstorm > Decompose > Refine > Plan > Execute > Track.

Describe your idea and Mymir decomposes it into tasks with dependency edges, determines what's ready to plan or implement, and hands your agent the exact context it needs for that stage. When a task is plannable, your agent gets the spec, prerequisites, and related work. When it's ready to implement, your agent gets the full execution context: upstream decisions, file paths, and acceptance criteria.

The agent moves from task to task with the right context at every step, no manual handoff required.

We're building Mymir using Mymir, so everything described here is something we're living in real time.

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How it looks

The web UI has two modes: Structure and Graph.

Structure mode puts your task list on the left and a detail panel on the right. You refine specs, track progress, and review execution records without switching views.

Graph mode overlays the context network so you can see how tasks, decisions, and dependencies connect while still working in the detail panel.

Zoom out and the full graph renders your entire context network. Clusters, bottlenecks, and orphaned work become obvious at a glance.

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What's coming

We're working on a hosted version for those who want the full experience without the setup. Run from anywhere, access your team's projects, collaborate across sessions. Privacy is a core value, which is why it's taking longer than usual to get right.

The hosted version will be a paid service. We can't bear the infrastructure costs on our own, and we'd rather be upfront about that than pretend otherwise. Self-hosted remains free and always will.

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Why open source

We believe everyone should have access to tools that help them build better things. Open source is how we make that real.

It also means we ship faster. Community contributions, bug reports, and ideas make Mymir better for everyone. If you care about better infrastructure for agent-driven development, come build with us.

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Stack

Next.js 16, TypeScript 6, React 19, PostgreSQL, Drizzle ORM, Tailwind CSS v4, Motion

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Stargazers

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Contributing

See CONTRIBUTING.md for setup instructions and PR guidelines.

License

Mymir is licensed under AGPL-3.0. A commercial license is also available, see LICENSING.md for details.