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Case file 04 · Open source

DEVELOPER OS

A local-first control plane for planning, running, validating and reviewing agent-assisted development.

  • Swift
  • SwiftUI
  • Kotlin
  • Jetpack Compose
  • SQLite
  • Git worktrees
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The challenge

Agent-assisted coding can execute quickly, but coordination, isolation, validation and human review are still scattered across terminals and memory. The experiment asks what a trustworthy local operating layer for that work should look like.

Developer OS mission-control interface
Master mission-control mockup that guides the native macOS implementation.

The approach

Developer OS uses a native SwiftUI control plane on macOS and a Kotlin companion on Android. A modular monolith coordinates projects, tasks, worktrees, agent providers, validation, review and cleanup while SQLite, Keychain and explicit permissions keep control on the machine.

Key decisions

  1. Keep metadata in SQLite and code, logs and artifacts in the filesystem so the system remains local-first.
  2. Isolate every execution in a Git worktree and separate agent output from independent validation.
  3. Make approval and merge different actions, with audit history and safe cleanup around both.

Technical architecture

Full-stack architecture designed and built end to end by me.

  1. 01 Native interfaces SwiftUI · Compose

    Mission control on macOS with an Android companion.

  2. 02 Orchestration core Modular monolith

    Projects, tasks, providers, approvals and lifecycle rules.

  3. 03 Local persistence SQLite · Filesystem · Keychain

    Metadata, artifacts and credentials remain on the machine.

  4. 04 Execution and review Agents · Git worktrees

    Isolated runs, independent validation, diff review and cleanup.

Modules

What the product is made of, as its own screens divide it.

  • 01 Projects & tasks

    Local projects, their tasks and the specs behind them.

  • 02 Executions in worktrees

    Every task execution isolated in its own Git worktree.

  • 03 Agent providers

    Agents behind a provider-independent protocol.

  • 04 Validation & review

    Checks that do not trust the agent’s own account of its work.

  • 05 Approval & merge

    Two distinct actions, then cleanup of the worktree.

  • 06 Local-first security

    Keychain, audit trail, explicit permissions and a kill switch.

  • 07 Android companion

    A Kotlin and Jetpack Compose app after the core MVP.

Before → after

  • Before

    Agent work scattered across terminals.

    After

    One visible task and execution lifecycle.

  • Before

    Changes sharing the active checkout.

    After

    Every run isolated in a Git worktree.

  • Before

    Output accepted without a separate gate.

    After

    Validation, review and merge are explicit stages.

Technologies

  • Swift
  • SwiftUI
  • Kotlin
  • Jetpack Compose
  • SQLite
  • Git worktrees

The wider toolkit

  • Xcode
  • macOS
  • Android
  • Android Studio
  • Keychain

Brand marks from Simple Icons; concepts without one are drawn in-house.

Project log

Aug 2026 → Sep 2026 · 2 active months

114 commits
1 repository
2 active months
Aug 2026 Busiest month: Aug 2026 · 104 commits Sep 2026
  • developer-os native · 114 commits Aug 2026 → Sep 2026

In the tree

  • 105 test files
  • 350 native source files
  • 423 tracked files

Read from the local Git history on Oct 6, 2026. Aggregates only.

The outcome

The Core MVP exercises the full path from task creation to a real diff, independent validation, human review, merge and cleanup. The repository snapshot contains 114 commits, two native applications and 105 Swift and Kotlin test files documenting the behavior built so far.

Private codebase — this file shares the thinking, not the source.

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