# Logging

> DXOS logging with @dxos/log (log, levels, dbg), LOG_FILTER for test stdout, and querying Composer NDJSON logs via scripts/query-logs.mjs. Use when adding or reviewing logs, debugging from app.log or tests, or explaining log levels and vite-plugin-log output.

- Skill: `dxos/logging` (Agent Skill)
- Install (CLI): `npx skillmds@latest add dxos/logging`
- Raw SKILL.md: https://api.skillmd.com/api/skills/dxos/logging/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: dxos (https://skillmd.com/u/dxos)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/dxos/logging

---


# DXOS logging (`@dxos/log`)

All application logging goes through **`@dxos/log`** (“dxlog”). Import: `import { log, dbg } from '@dxos/log';`

## Message shape

- **Static message first** (lowercase phrase, no template literals in the message string).
- **Structured context second** (object). Do not stuff dynamic data only into the message; put it in context.

```ts
log('received queue batch', { count: items.length, spaceKey });
log.warn('plugin failed to activate', { pluginId, cause: err.message });
```

## Levels

Use **`log('…', ctx)`** for DEBUG-level diagnostics. The callable `log` **is** `log.debug` (same level); prefer **`log(...)`** in new code and avoid writing **`log.debug`** so style stays consistent.

| API                           | Role                                                                                                                                                                         |
| ----------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `log('…', ctx)`               | **DEBUG** — default verbose diagnostics; often **not** shown on the default browser console but still captured when a log sink (e.g. vite-plugin-log `app.log`) is attached. |
| `log.trace('…', ctx)`         | **TRACE** — finest granularity; usually filtered out everywhere except explicit trace filters.                                                                               |
| `log.verbose('…', ctx)`       | **VERBOSE** — between debug and info.                                                                                                                                        |
| `log.info('…', ctx)`          | **INFO** — user-visible / product-level events; **shown on console** with typical filters.                                                                                   |
| `log.warn('…', ctx)`          | **WARN** — non-fatal issues.                                                                                                                                                 |
| `log.error('…', ctx)`         | **ERROR** — hard failures.                                                                                                                                                   |
| `log.catch(err, ctx?, meta?)` | Log an **Error** at ERROR level (stack in processors).                                                                                                                       |

Rule of thumb: **`log.info` and above** are what operators and users normally see in the **console**; **`log(...)`** is for deep diagnosis and file buffers.

## `dbg`

- `dbg(value)` (and related helpers from `@dxos/log`) are for **local debugging only**.
- **Remove or replace before committing** (or gate behind dev-only code paths).

## Composer dev: `app.log`

With **`@dxos/vite-plugin-log`** enabled in Composer, browser **`@dxos/log`** output is serialized to **NDJSON** and appended to:

`packages/apps/composer-app/app.log`

(from the repo root; path is relative to **process cwd** when the dev server runs, usually repo root → that file).

Truncate/restart behavior is owned by the plugin (file cleared on dev server start).

## Tests: `LOG_FILTER` (stdout)

In **Node / vitest** runs, `@dxos/log` reads **`process.env.LOG_FILTER`** when building the default config (`packages/common/log/src/options.ts`). Set it to control **which levels and paths are printed to the test process stdout** (same filter string shape as **`query-logs -q`**: level name, `pathFragment:level`, comma-separated list, etc.).

```bash
LOG_FILTER=debug moon run functions-runtime:test -- AgentService.test.ts
```

Use **`trace`** for maximum noise, **`info`** for quieter runs, or a path-scoped value (e.g. `AgentService:debug`, `functions-runtime:debug`) to narrow output. This does **not** write `app.log`; it only affects the **console processor** during that command.

## Tests: NDJSON file sink (`@dxos/vite-plugin-log/vitest`)

Node Vitest projects wire **`@dxos/vite-plugin-log/vitest`** via `vitest.base.config.ts` (`global-setup` truncates once; per-worker `setup` installs a file processor). Logs flow: **`@dxos/log` → `serializeToJsonl` → `JsonlFileLogStore` → `<package>/test.log`** (NDJSON, compatible with `scripts/query-logs.mjs`).

| Env                                 | Role                                                      |
| ----------------------------------- | --------------------------------------------------------- |
| `DX_TEST_LOG=0`                     | Disable file sink                                         |
| `DX_TEST_LOG_FILE`                  | Override path (edge: same as legacy `EDGE_TEST_LOG_FILE`) |
| `DX_TEST_LOG_FILTER` / `LOG_FILTER` | File sink filter (default `debug`)                        |

```bash
LOG_FILTER=lifecycle:debug moon run functions-runtime:test -- AgentService.test.ts
node scripts/query-logs.mjs packages/core/compute/functions-runtime/test.log -q lifecycle:debug
```

Exported for reuse (e.g. edge Miniflare tail → `JsonlFileLogStore.pushLines`): `JsonlFileLogStore`, `installNodeLogProcessor`, `resolveTestLogFilePath`, `truncateTestLogFile` from **`@dxos/vite-plugin-log/vitest`**.

## Querying logs: `scripts/query-logs.mjs`

From repo root:

```bash
node scripts/query-logs.mjs <file> [-q <filter>]... [-g <regexp>]...
pnpm query-logs -- <file> ...
```

- **`-q`**: comma-separated filters in **`LOG_FILTER` style** (see `packages/common/log` `parseFilter` + `shouldLog`).
  - **Level only**: `debug`, `info`, `warn`, `error`, `trace`, `verbose`.
  - **Path substring + level**: `echo-db:debug` — file path in the log line must contain `echo-db`, level must be ≥ `debug`.
  - **Exclude**: `!substring` — drop lines whose file path contains `substring` (after `!`). Use `!rpc.ts` to drop noisy RPC files. Bare `!foo` is treated as exclude at trace threshold internally.
  - **Repeat `-q`**: **OR** between groups; inside one `-q`, filters work like runtime `shouldLog` (includes + excludes).
- **`-g`**: **RegExp** (JavaScript) run on the **raw JSON line**. Repeat **`-g`** for **AND**.

Output columns: `timestamp`, level letter, `file:line`, scope (`o`), message (`m`), context (`c`), error (`e`).

### Workflow

Run **narrow queries** and pipe to Unix tools:

```bash
# How many debug lines mention ProcessManager?
node scripts/query-logs.mjs packages/apps/composer-app/app.log -q debug -g ProcessManager | wc -l

# Echo DB query pipeline only, exclude rpc.ts noise, first 20 lines
node scripts/query-logs.mjs packages/apps/composer-app/app.log -q 'echo-db:debug,!rpc.ts' | head -20

# Automerge-related paths at debug
node scripts/query-logs.mjs packages/apps/composer-app/app.log -q automerge:debug | less

# Invalid RPC response ids (example message grep)
node scripts/query-logs.mjs packages/apps/composer-app/app.log -q debug -g 'invalid id' | head

# OR two path groups: client package OR space proxy, debug and above
node scripts/query-logs.mjs packages/apps/composer-app/app.log -q 'sdk/client/src:debug' -q 'space-proxy:debug' | wc -l
```

**Requires** `@dxos/log` built: `moon run log:build` (script imports `packages/common/log/dist/...`).

## Path fragments to try (Composer `f` field)

These substrings match **typical** `packages/...` paths in NDJSON. Counts vary per session.

| Area                      | Example `-q` fragment                                    | Notes                                              |
| ------------------------- | -------------------------------------------------------- | -------------------------------------------------- |
| Process / agent runtime   | `ProcessManager` (use `-g`) or `functions-runtime:debug` | `functions-runtime/src/process/ProcessManager.ts`  |
| ECHO queries              | `echo-db:debug` or `echo/echo-db:debug`                  | `query-result`, graph, index                       |
| Automerge                 | `automerge:debug`                                        | Lower volume than full echo-db                     |
| Client (DXOS Client)      | `sdk/client/src:debug` or `client.ts:debug`              | `packages/sdk/client/src/client/client.ts`         |
| Space / ECHO proxy        | `space-proxy:debug`                                      | `packages/sdk/client/src/echo/space-proxy.ts`      |
| Dedicated worker services | `dedicated-worker:debug`                                 | `packages/sdk/client/src/services/dedicated/`      |
| Mesh RPC (noisy)          | `mesh/rpc:debug`                                         | Very high volume; pair with `!rpc.ts` or `-g`      |
| RPC tunnel / worker port  | `rpc-tunnel:debug`                                       | Worker transport                                   |
| Plugins                   | `plugin-manager:debug`                                   | `packages/sdk/app-framework/.../plugin-manager.ts` |
| Edge / status RPC         | `edge` with `-g` or path under `client-services`         | Responses often `QueryEdgeStatusResponse`          |

Add more fragments by copying a path prefix from an **`app.log`** line (`f` field) and using it in `-q your-fragment:debug`.

## Related

- Log processors and filters: `packages/common/log/src/context.ts`, `packages/common/log/src/options.ts` (`parseFilter`).
- NDJSON capture shape: `packages/common/log/src/log-buffer.ts`.
- Composer wiring: `tools/vite-plugin-log`, `packages/apps/composer-app/vite.config.ts` (`vitePluginLog` in `sharedPlugins`).