fix(tui_gateway): restore openrouter provider on session resume

[liuhao1024]

What does this PR do?

When a user switches from OpenRouter to a custom endpoint, resuming any previous OpenRouter session fails with a misleading context-window error. The root cause is _BARE_BILLING_PROVIDERS in tui_gateway/server.py treating "openrouter" as a non-routable billing bucket (alongside "auto" and "custom"), which causes _stored_session_runtime_overrides to drop the provider override on resume. The session then falls back to the current global model (the custom endpoint), which serves a completely different model catalog and returns a tiny context window for the stored model name.

OpenRouter is a fully routable provider with its own API key, base URL, and model catalog. Removing it from _BARE_BILLING_PROVIDERS lets OpenRouter sessions correctly restore their provider identity on resume.

Related Issue

Fixes #57588

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• tui_gateway/server.py — Remove "openrouter" from _BARE_BILLING_PROVIDERS set. "auto" and "custom" remain as non-routable billing classes. Added comment explaining why "openrouter" is excluded ([Bug]: Adding new custom provider breaks all previous sessions. Provider changes, but not the model. #57588).
• tests/test_tui_gateway_server.py — Updated test_stored_session_runtime_overrides_skips_bare_billing_provider to remove "openrouter" from the bare-bucket loop. Added test_openrouter_session_resume_restores_provider regression test verifying that OpenRouter sessions restore the "openrouter" provider override on resume.

How to Test

1. Configure Hermes with a custom endpoint (e.g. Featherless) as the default model.
2. Create a session using OpenRouter (e.g. anthropic/claude-opus-4.8).
3. Exit and restart Hermes.
4. Resume the OpenRouter session via /sessions.
   • Before: fails with "context window of 2,048 tokens, which is below the minimum 64,000" because the resume hits the custom endpoint with the OpenRouter model name.
   • After: session resumes correctly using OpenRouter as the provider.
5. Automated: python -m pytest tests/test_tui_gateway_server.py::test_stored_session_runtime_overrides_skips_bare_billing_provider tests/test_tui_gateway_server.py::test_openrouter_session_resume_restores_provider tests/tui_gateway/test_custom_provider_session_persistence.py -v → should pass.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes
• I've tested on my platform: macOS

Documentation & Housekeeping

• I've updated relevant documentation — N/A (no doc/docstring impact)
• I've updated cli-config.yaml.example if I added/changed config keys — N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — N/A
• I've considered cross-platform impact (Windows, macOS) — N/A (pure Python logic, no platform-specific code)
• I've updated tool descriptions/schemas if I changed tool behavior — N/A

[teknium1]

Thanks for the focused regression fix. Current main still has "openrouter" in _BARE_BILLING_PROVIDERS at tui_gateway/server.py:2243; _stored_session_runtime_overrides() consequently drops it at tui_gateway/server.py:2282. Both deferred and eager session.resume paths consume that helper at tui_gateway/server.py:5778 and tui_gateway/server.py:5861.

The proposed change restores the provider exactly at the shared helper, while preserving the existing auto and custom filtering. The added regression test is a behavioral contract for the affected stored-session shape. The current tree's OpenRouter profile is registered as a concrete provider at plugins/model-providers/openrouter/__init__.py:170-188.

This is an automated hermes-sweeper review.

[kshitijk4poor]

Merged via #85558 — your commit was cherry-picked onto current main with your authorship preserved (1c87772186 on main). The branch here was ~7,900 commits behind, so we salvaged rather than rebased; the only addition was a follow-up comment fix.

Thanks for the focused fix and the regression test — this closes #57588. (@Ahmett101's #57597 implemented the same fix and is credited in the salvage PR as well.)