Measure with RUST_LOG and read the log file
What it is
RUST_LOG makes Loomcoding write its trace events to a log file in your profile. With the variable unset, nothing is written and no file is created.
What it is for
- Measuring how much output compression saves.
- Reading the counters of the ODD workflow.
- Checking what happened in a session without reading the terminal.
How
- Set
RUST_LOGbefore you start Loomcoding. - Use Loomcoding as usual.
- Read
<profile>/.loomcoding/logs/loomcoding-daemon.log.
Example
On a Unix shell, set the variable for one start:
RUST_LOG=output_filter=info loom
In PowerShell, set it for the current window:
$env:RUST_LOG = 'output_filter=info'
loom
A real line from the log looks like this:
2026-11-07T23:47:59.628314Z INFO output_filter: salida filtrada regla="cargo" original_bytes=2258 sent_bytes=653
Choosing what to log
Value of RUST_LOG | What it records |
|---|---|
output_filter=info | Output compression: one line per filtered output. |
odd=info | ODD workflow counters. |
output_filter=info,odd=info | Both. |
info | Everything at level info or higher. |
Log files
| Process | File |
|---|---|
Client (the terminal interface or --print) | <profile>/.loomcoding/logs/loomcoding-cliente.log |
| Daemon (runs the agent) | <profile>/.loomcoding/logs/loomcoding-daemon.log |
<profile> is your home folder, or the folder in LOOMCODING_HOME when that variable is set. Agent events go to the daemon log, because the daemon runs the agent loop.
Settings and defaults
| Name | Default | Requires restart |
|---|---|---|
RUST_LOG | not set. Nothing is written. | Yes |
| Size limit of each log | 5 MiB. Then the file rotates to <name>.log.1, which keeps one old copy. | Not configurable |
The daemon is a separate process that can stay alive between runs and keeps the setting it started with. Close it, or close all loom processes, so that it reads the new value.
Privacy
The events record rule names, counters and byte counts. They never record command text, paths or tool output. A broad setting such as debug can include messages from third-party libraries. Review a log before you share it.
Result
Each line is one event. To get the savings of a rule, add up original_bytes and subtract sent_bytes for the same regla.
If it does not work
| Symptom | Fix |
|---|---|
| The log file does not exist. | RUST_LOG was not set when Loomcoding started, or an older daemon is still running. Close all loom processes and start again. |
| The client log is empty. | This is normal. Agent events are in the daemon log. |
| The file shows size 0 on Windows. | The size can show 0 while the file is open. Read its content. |
| The log is not written at all. | Loomcoding ignores a file it cannot open and keeps running. Check the folder permissions. |