Thinking Path

• Hermes WebUI now has two model controls with different scopes: the Composer model selector changes the current conversation, while Preferences -> Default Model updates the default for new conversations.
• That distinction was easy to miss because the old Composer toast implied a future/new-conversation effect, and Preferences did not explain what the default model controls.
• This PR keeps the behavior unchanged and clarifies the mental model directly where users make the choice.
• It is a narrow UI-copy slice under the broader provider/model source-of-truth work tracked in Clarify and harden Provider/Model source-of-truth across WebUI, CLI, and Gateway #1240.

What Changed

• Added a sticky note at the top of the Composer model dropdown:
  • Applies to this conversation from your next message.
• Updated the Composer model-selection toast to use the same wording.
• Added helper copy below Preferences -> Default Model:
  • Used for new conversations. Existing conversations keep their selected model.
• Added i18n keys for the new model-scope copy.
• Added regression coverage for the dropdown note, toast wording, and Preferences copy.
• Added a changelog entry.

Why It Matters

This removes the most immediate user-facing ambiguity between:

• changing the model for the current conversation, and
• changing the Hermes default model used for new conversations.

It does not try to solve the larger provider/model source-of-truth problem in one PR. That broader work remains tracked in #1240 and related follow-ups.

Refs #1240.

Screenshots

Screenshot 1 — Preferences now clarifies that Default Model is used for new conversations, while existing conversations keep their selected model.

Screenshot 2 — The Composer dropdown screenshot shows the matching sticky note at the top of the model list, using the same scope language as the toast.

Verification

• pytest tests/test_model_scope_copy.py tests/test_provider_mismatch.py tests/test_issues_907_908_909_model_dropdown.py tests/test_issue895_894_nous_prefix.py
• node --check static/ui.js
• node --check static/boot.js
• node --check static/i18n.js
• git diff --check

Risks / Follow-ups

• This does not change provider/model persistence, validation, fallback, or catalog source-of-truth behavior.
• Preferences -> Default Model still writes to the Hermes Agent config through the existing /api/default-model path.
• Follow-up discussion: Composer-scoped actions currently use the global top-right toast system. We may want a separate issue to ask Aron whether model-picker feedback should be localized near the Composer/model chip instead.

Model Used

• Provider: OpenAI
• Model: GPT-5 via Codex
• Notable tool use: local code inspection, targeted pytest regression tests, Node syntax checks