Thinking Path

• Hermes WebUI keeps sessions usable across provider/model configuration changes.
• bug(sessions): stale session model not normalized for non-standard providers (ollama, deepseek, xai) — sessions stay broken after fixing default model #1023 / fix(onboarding): non-standard provider/path cluster — wizard fires & overwrites config (#1019 #1020 #1021 #1023) #1029 already recover stale bare and slash-prefixed session models.
• A remaining legacy path is persisted @provider:model values from the model dropdown, such as @copilot:gpt-5.5.
• That format is valid for currently-routable cross-provider selections, so the fix cannot blindly strip every @provider: prefix.
• This PR extends the existing compatibility layer so stale/unroutable provider hints recover while still-routable explicit hints remain intact.

What Changed

• Added @provider:model handling to _resolve_compatible_session_model().
• Normalizes redundant active-provider hints to the bare model, for example @openai-codex:gpt-5.4-mini -> gpt-5.4-mini.
• Preserves still-routable non-active provider hints, for example visible Copilot dropdown selections.
• Recovers stale/unroutable hints to the current active provider family or default model.
• Added regression coverage for stale Copilot hints, active-provider hints, valid cross-provider hints, and family mismatch fallback.
• Added a changelog entry.

Why It Matters

Older sessions can otherwise stay pinned to a provider that is no longer routable. In that state, a session can appear to send but never show an assistant reply until the stored model is manually edited. This keeps old sessions usable without a bulk migration or UI change.

Fixes #1128.
Refs #1023.
Refs #1029.

Verification

• python -m py_compile api/routes.py
• python -m pytest tests/test_provider_mismatch.py -k "session_model or provider_model or stale_at_provider or legacy_at_provider or active_at_provider or routable_non_active" -v
• python -m pytest tests/test_provider_mismatch.py tests/test_model_resolver.py tests/test_credential_pool_providers.py tests/test_issue895_894_nous_prefix.py -v

Risks / Follow-ups

• The fix is intentionally conservative: if a non-active provider hint is still visible/routable in the current catalog, it is preserved.
• This does not bulk-migrate historical session files. Existing write-path normalization persists only when a stale explicit model is encountered.
• No UI behavior changes, so no screenshots are included.

Model Used

• Provider: OpenAI Codex
• Model: GPT-5.5
• Mode/tooling: local code inspection, shell tests, GitHub CLI