Flip the resolve_persist_behavior() fallback from persist-to-config to
session-only. A plain /model <name> (typed or via any picker — CLI,
TUI/Desktop, gateway) now affects only the current session; --global
persists explicitly, and model.persist_switch_by_default: true restores
the old opt-out behavior for users who want switches to stick.
This is the root cause behind the recurring 'session switch applied
globally' bug class (#61458, #63083, #58290, #61190): every surface
funnels its no-flag default through this one function, so per-surface
patches kept missing paths. Fixing the default fixes all surfaces at
once: CLI typed + picker, TUI/Desktop config.set + slash, gateway typed
+ inline picker.
Builds on liuhao1024's #58371 (--provider session scoping, cherry-picked
as the previous commit) and supersedes the per-surface #61488.
A plain /model <name> switch only lasted for the current session — every
new session reverted to the previously-configured model, so users had to
re-switch every time (e.g. glm-5.1 -> glm-5.2 on every launch).
Persist-by-default is now the behavior across all three /model surfaces
(CLI, gateway, TUI/dashboard), gated by a new config key
model.persist_switch_by_default (default true):
/model <name> switch model (persists to config.yaml)
/model <name> --session switch for this session only
/model <name> --global switch and persist (explicit, unchanged)
The effective persistence is resolved once via resolve_persist_behavior()
in hermes_cli/model_switch.py so --session opts out, --global opts in,
and the config-gated default applies otherwise. --global remains a valid
explicit no-op alias for the new default.
Reported via AskClaw. When config.yaml has `model: <name>` (flat string)
instead of the nested `model: {default: ..., provider: ...}` form, every
gateway `/model X --global` crashed silently with
TypeError: 'str' object does not support item assignment
The persist block did:
model_cfg = cfg.setdefault("model", {})
model_cfg["default"] = result.new_model
`setdefault` returns the existing scalar, and the next assignment blows
up. The 'switch failed' warning was logged at WARNING level and the user
never saw why their persist didn't stick.
Coerce scalar/None `model:` into a dict before mutation, in both the
gateway path (`gateway/run.py`) and the sister site in
`hermes_cli/doctor.py --fix` (same setdefault-on-string flaw). The CLI
`/model` path is unaffected because it goes through `_set_nested` which
already replaces scalar leaves with dicts.
Regression test `tests/gateway/test_model_command_flat_string_config.py`
covers the flat-string, missing, and proper-dict cases. Without the fix,
the flat-string case fails with the exact original TypeError.
