Symphony

A powerful LLM task harness that drives long horizon tasks with the LLM provider and client of your choice.

Developer tools · CLI

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v0.1.0 Node 20.11+ Windows · macOS · Linux Free

The symphony run view inside VS Code on Windows, showing the live task table, pipeline watch summary and streamed agent output
Symphony TUI running in VS Code on Windows

What's inside

A long horizon task harness

Multiple LLM providers

Claude Code, Cursor, OpenCode (1.x), Codex CLI, Gemini CLI and Antigravity — plus a fake provider for testing the harness itself.

Fresh context per task

Each session gets only its task file, a PROGRESS digest, the design docs it names and a generated repo index. No context rot, no hidden state.

Independent verification

A per-task verify:, a configured verifyCommand or your project’s test script runs after every done. A failed verify demotes the task.

Guardrails you control

Retry and halt policies, per-task and per-run cost caps, max iterations and tasks, a STOP sentinel and lifecycle hooks.

Resumable and inspectable

State files, roadmap markers, and every session’s prompt, rendered log and raw NDJSON saved for review.

MCP selection

Scope each session to the MCP servers its task needs, so unrelated toolchains cost nothing.

Getting started

1

Install into your project

Clone the repository next to your other repos, then run ./install.sh /path/to/project on macOS or Linux, or ./install.ps1 -Target C:\path\to\project on Windows. It builds the harness and copies it to <project>/.symphony/.

2

Init and check the plan

./.symphony/symphony init scaffolds the docs skeleton. doctor checks Node, git, the roadmap, provider auth and your verify command before anything runs.

3

Run the pipeline

./.symphony/symphony run works the roadmap in order, committing after each task. Start with brief if you only have an idea, or start + attach for a detached run.

git clone https://github.com/binbuf/symphony.git
cd symphony
./install.sh /path/to/your/project

cd /path/to/your/project
./.symphony/symphony init
./.symphony/symphony doctor
./.symphony/symphony run
git clone https://github.com/binbuf/symphony.git
Set-Location symphony
./install.ps1 -Target C:\path\to\your\project

Set-Location C:\path\to\your\project
./.symphony/symphony.ps1 init
./.symphony/symphony.ps1 doctor
./.symphony/symphony.ps1 run

Under the hood

Simple doc contract that an LLM can generate in seconds.

The harness owns a small, stack-agnostic planning format: a roadmap of task bullets, a progress notebook, per-task files with acceptance criteria, design docs and ADRs, and per-task run logs. Commands include init, doctor, lint, prepare, run, status, accept, reset, nudge, split, replan and clear-halt.

  • TypeScript on Node — with no runtime dependencies in the installed copy
  • Resumable daemon — detached runs publish a heartbeat; attach opens the live view
  • Automatic breakdowns — a task that is too big can be split into subtasks mid-run
  • Optional extras — Slack notifications, a vision tool and a pipeline-watch summary
  • Free test surface — a fake provider and rules-only decision mode exercise the harness without spending

symphony FAQ

Which AI tools does symphony work with?

Claude Code, Cursor, OpenCode (1.x; 2.x is not supported yet), Codex CLI, Gemini CLI and Google Antigravity. A built-in fake provider replays fixtures so you can test the harness without spending anything.

What do I need to run it?

Node 20.11 or later and git, on Windows, macOS or Linux. The doctor command checks both, along with your roadmap, provider auth and verify command, before a run starts.

What does it cost?

symphony itself is free. You pay your provider for the sessions it runs, and per-task and per-run cost caps can halt a run before it spends more than you allow.

Is it safe to leave running?

It is built to run unattended: provider permission prompts are bypassed by default, work is committed per task, and a STOP sentinel pauses at the next task boundary. Pass --safe to restore prompts for a run.

Where does it put things?

The harness installs to a .symphony/ folder in the project root, which the installer adds to your .gitignore. Plans and logs live in the project’s docs/ folder and are committed with the work.

Is symphony open source?

The source is public on GitHub and the project is built in the open. A formal license has not been published yet, so treat it as source-available for now.

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