SubMiner/backlog/tasks/task-36 - Add-structured-logging-with-configurable-verbosity-levels.md

id, title, status, assignee, created_date, labels, dependencies, priority

id	title	status	assignee	created_date	labels	dependencies	priority
TASK-36	Add structured logging with configurable verbosity levels	To Do		2026-02-14 00:59	infrastructure developer-experience observability		medium

Description

Replace ad-hoc console.log/console.error calls throughout the codebase with a lightweight structured logger that supports configurable verbosity levels (debug, info, warn, error).

Motivation

• TASK-33 (restrict mpv socket logs) is a symptom of a broader problem: no log-level filtering
• Debugging production issues requires grepping through noisy output
• Users report log spam in normal operation
• No way to enable verbose logging for bug reports without code changes

Scope

1. Create a minimal logger module (no external dependencies needed) with debug, info, warn, error levels
2. Add a config option for log verbosity (default: info)
3. Add a CLI flag --verbose / --debug to override
4. Migrate existing console.log/error calls to use the logger
5. Include context tags (service name, operation) in log output for filterability

Design constraints

• Zero external dependencies — use a simple wrapper over console methods
• Must not impact hot-path performance (subtitle rendering, tokenization)
• Log level should be changeable at runtime via config hot-reload if that feature exists
• TASK-33 becomes trivial once this lands (mpv socket logs become debug level)

Acceptance Criteria

• #1 A logger module exists with debug/info/warn/error levels.
• #2 Config option controls default verbosity level.
• #3 CLI --verbose/--debug flag overrides config.
• #4 Existing console.log/error calls in core services are migrated to structured logger.
• #5 MPV socket connection logs use debug level (resolves TASK-33 implicitly).
• #6 Log output includes source context (service/module name).
• #7 No performance regression on hot paths (rendering, tokenization).