config.json

Fabric Agents' global configuration lives in a single file:

~/.fabric-agent/config.json

It holds your workspace list, LLM connections, default model and thinking level, UI preferences like theme and keyboard shortcuts, and a handful of feature flags.

Most fields are set through the Settings UI, but the file is plain JSON — edit it directly if you prefer, or commit a copy for version control / backup.

Automatic backups

On every startup, Fabric Agents snapshots your current config.json to a dated file alongside it before anything can modify the workspace registry:

~/.fabric-agent/config.json.bak-YYYY-MM-DD

The three newest snapshots are kept and older ones are pruned automatically. Only the first snapshot of each day is written — a later launch the same day never overwrites it, so the earliest good copy from each day is preserved. If a bad write or reset ever corrupts your config, rename the most recent backup back to config.json to recover your workspaces and connections.

Where fields come from

• User-editable (settings, theme, defaults, shortcuts) — set via Settings UI or by editing JSON.
• Auto-written by the app — activeWorkspaceId, activeSessionId, timestamps.
• Migrated automatically — legacy fields from older versions get upgraded on first launch and then removed.

Full schema

Workspaces and active selection

LLM connections

Defaults

Per-workspace defaults live in {workspace}/config.json under defaults and override the global values.

UI and input

System behaviour

Updates

Network and OS integration

Server mode (embedded server)

Onboarding state

A realistic example

{
  "workspaces": [
    {
      "id": "personal",
      "name": "Personal",
      "rootPath": "~/.fabric-agent/workspaces/personal",
      "createdAt": 1704067200000
    },
    {
      "id": "my-app",
      "name": "My App",
      "rootPath": "~/code/my-app",
      "createdAt": 1710000000000
    }
  ],
  "activeWorkspaceId": "my-app",
  "activeSessionId": "260420-swift-river",

  "llmConnections": [
    {
      "slug": "anthropic-api",
      "name": "Anthropic (API Key)",
      "providerType": "anthropic",
      "authType": "api_key",
      "defaultModel": "claude-opus-4-8",
      "createdAt": 1704067200000
    }
  ],
  "defaultLlmConnection": "anthropic-api",

  "defaultThinkingLevel": "medium",
  "colorTheme": "default",
  "sendMessageKey": "enter",
  "notificationsEnabled": true,
  "keepAwakeWhileRunning": false,
  "browserToolEnabled": true,
  "richToolDescriptions": true,
  "extendedPromptCache": false,
  "enable1MContext": true,
  "updateChannel": "stable"
}

Migration

On startup, Fabric Agents converts older config shapes to the current one, then removes the legacy fields:

Migrations are non-blocking — failures are logged and the old config continues to work.

Editing safely

A few tips if you edit this file directly:

• Back up before big changes. cp ~/.fabric-agent/config.json ~/.fabric-agent/config.json.bak.
• Close the app first. The running app holds the config in memory and may overwrite your edits on next auto-save.
• Never paste credentials here. API keys, OAuth tokens, and refresh tokens live in the OS keychain (macOS / Windows) or encrypted credential store (~/.fabric-agent/credentials/ on Linux). config.json only references connections by slug.

Related

• Preferences — ~/.fabric-agent/preferences.json (name, timezone, bio).
• LLM connections — the llmConnections[] schema in detail.
• Environment variables — env vars that override config values at runtime.