Problem

When running in daemonized environments like systemd with journald, log output contains redundant information:

Jan 25 16:27:13 gitlab-mcp.sw.foundation node[39785]: [16:27:13.276] INFO (gitlab-mcp): StreamableHTTP endpoint endpoint=http://0.0.0.0:3333/mcp note=modern, supports SSE + JSON-RPC

The journald already provides:

• Timestamp (Jan 25 16:27:13)
• Hostname (gitlab-mcp.sw.foundation)
• Process name and PID (node[39785])

Our logger then duplicates:

• Timestamp ([16:27:13.276])
• Log level (INFO)
• Daemon name ((gitlab-mcp))

Additionally, session IDs in logs are truncated awkwardly:

session=9fd82b35..

Proposed Solution

1. LOG_FORMAT Environment Variable

Add LOG_FORMAT environment variable (similar to nginx log_format) for flexible log output configuration.

Format Tokens

Presets

minimal (default) - for daemonized environments:

LOG_FORMAT="%msg"

Output:

StreamableHTTP endpoint endpoint=http://0.0.0.0:3333/mcp note=modern, supports SSE + JSON-RPC

full - standalone/development:

LOG_FORMAT="[%time] %level (%name): %msg"

Output:

[16:27:13.276] INFO (gitlab-mcp): StreamableHTTP endpoint endpoint=http://0.0.0.0:3333/mcp note=modern, supports SSE + JSON-RPC

Example .env Configuration

# Log format (nginx-style tokens: %time, %level, %name, %msg)
# Default: minimal format for daemonized environments
LOG_FORMAT="%msg"

# Full format for standalone/development (uncomment to enable):
# LOG_FORMAT="[%time] %level (%name): %msg"

2. Improved Session ID Format

Change session ID truncation from prefix-only to prefix+suffix for better identification:

Format: first 4 chars + .. + last 4 chars

This makes it easier to distinguish sessions while keeping logs compact.

Context

• Related to fix(logging): Apply LOG_JSON pattern to all logger calls (multiline output remains in 144 places) #209 (LOG_JSON pattern application)
• Deployment uses systemd on 192.168.95.53 with journald for log aggregation
• Journald already captures all metadata, making app-level fields redundant

Implementation Notes

• Modify src/utils/logger.ts to parse LOG_FORMAT tokens
• Default to %msg (minimal) when LOG_FORMAT not set
• Update session ID truncation helper to use first4..last4 format
• Should work alongside LOG_JSON=true (JSON mode ignores LOG_FORMAT or uses it for field selection)
• Document both presets in .env.example