load_config() and read_raw_config() now cache their result keyed on
the config file's (mtime_ns, size). On cache hit they return a deepcopy
of the cached value, skipping yaml.safe_load + deep-merge + normalize +
env-var expansion entirely. save_config() + migrate_config() write via
atomic_yaml_write which produces a fresh inode, so stat() sees a new
mtime_ns and the next load repopulates automatically — no explicit
invalidation hook needed.
Measured per-call cost:
load_config() cold: 13.3 ms
load_config() cached: 0.23 ms (57x faster)
read_raw_config() cached: 0.13 ms
A single gateway turn hits the config 5-15 times (session context,
auxiliary client resolution, memory config, plugin hooks, approval
lookups, per-tool settings). That's 65-200 ms/turn of pure YAML
re-parsing on main. After this change: 1-3 ms/turn.
Also migrates gateway/run.py's 6 direct yaml.safe_load(config.yaml)
call sites through _load_gateway_config, which now shares the
read_raw_config cache when _hermes_home agrees with the canonical
config path. The direct-read fallback is retained for tests that
monkeypatch gateway_run._hermes_home without touching HERMES_HOME.
Safety:
- load_config() returns a deepcopy on every call; the 67+ call sites
that mutate the result (cfg["model"]["default"] = ..., etc.) can't
corrupt the cache.
- save_config() / atomic_yaml_write bump mtime, naturally invalidating
the cache for the next reader.
- Cache is keyed on str(config_path), so HERMES_HOME profile switches
don't collide.
Verified:
- 112 config tests pass (test_config, test_config_env_expansion,
test_config_env_refs, test_config_drift, test_config_validation,
test_aux_config).
- 87 gateway tests pass (test_verbose_command, test_session_info,
test_compress_focus, test_runtime_footer, test_resume_command,
test_reasoning_command, test_approve_deny_commands,
test_run_progress_interrupt).
- Live hermes chat smoke — 2 turns + /model switch + tool calls,
zero errors in agent.log.
Co-authored-by: teknium1 <teknium@users.noreply.github.com>
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