fix(bridge): stop root logger gating INFO out of bot.log

[jinon86]

Summary

bot.log on quiet nodes sits at 0 bytes and INFO-level operational markers never appear — which made a memory-loss investigation impossible to diagnose from logs. Root cause: setup_logging() gates the root logger at WARNING in non-debug mode, so every INFO record is dropped before it can reach the INFO-level file handler.

The bug

console_level = log_level if is_debug else logging.WARNING
logging.basicConfig(level=console_level, ...)   # sets ROOT level to WARNING
fh = logging.FileHandler(logs_dir / "bot.log", ...)
fh.setLevel(log_level)                           # file handler wants INFO
logging.getLogger().addHandler(fh)

The root logger's level is a hard gate applied before any handler's own level — a record below it is discarded and never dispatched. Setting the root to WARNING therefore defeats fh.setLevel(INFO): the file handler can only filter records the logger already passed, and it never receives INFO. Net effect: bot.log captures WARNING+ only. A quiet node produces no WARNING+, so the file stays empty, and INFO diagnostics (boot banners, the Ignoring persisted session_id session-resume trace, etc.) are invisible.

Reproduced directly: with the root at WARNING, logger.info("Ignoring persisted session_id …") is absent from the file while a logger.warning(...) on the same run is present.

The fix

Set the root to log_level (INFO) so the file handler receives INFO, and gate the console StreamHandler per-handler at console_level (WARNING in non-debug) so stdout stays quiet:

logging.basicConfig(level=log_level, ...)
for _h in logging.getLogger().handlers:
    _h.setLevel(console_level)   # console quiet; root passes INFO to the file handler

Verified after the change: INFO markers reach bot.log while the console still suppresses them (only WARNING+ on stdout).

Test plan

• Standalone repro confirms before/after behavior (INFO dropped → INFO written; console stays WARNING).
• bridge/tests/test_logging_levels.py pins the invariant (root ≤ INFO, a file handler at ≤ INFO, console handlers ≥ WARNING). Skips cleanly where pydantic isn't installed; runs on CI.

Context

This unblocks the follow-up investigation into within-conversation memory loss on Termux nodes: the smoking-gun marker for the suspected cause (Ignoring persisted session_id, logged at INFO) was being silently discarded, so the log-based diagnostic could not see it. With INFO restored to bot.log, re-running the diagnostic after a repro will show whether the bridge is restarting between messages and refusing to resume the persisted session.

🤖 Generated with Claude Code

https://claude.ai/code/session_017rAPKfsLfaYqNY8iPXWX34

---

Generated by Claude Code

[seoseo-ai]

검증 완료: CI pass, local targeted logging test pass, harness pass, diff/secret scan clean. Reviewer fix added to force root logger level under existing handlers.

[seoseo-ai]

Approved after diff review and green CI. Local verification: ruff on changed files passed; bridge regression test passed; full bridge pytest passed.