Summary

When a user sets provider: custom in config.yaml, resolve_provider() silently converts it to "openrouter" (line 666 in auth.py). This causes:

• /model shows "via openrouter" instead of "via custom"
• The provider name gets overwritten in the user's mental model and potentially in config
• No notice is given to the user about the remapping

Root cause: resolve_provider() treated "custom" and "openrouter" identically:

if normalized in {"openrouter", "custom"}:
    return "openrouter"

Fix:

• Return "custom" from resolve_provider() when explicitly requested
• Preserve "custom" in the runtime provider dict returned by resolve_runtime_provider()
• The OpenRouter runtime code path still handles the actual HTTP calls — it already had full custom base_url support (line 235 in runtime_provider.py)

Closes #2562

Changes

 hermes_cli/auth.py                        |  4 +-   (split the set check)
 hermes_cli/runtime_provider.py            |  6 +++  (preserve provider name)
 tests/test_runtime_provider_resolution.py | 82 +++ (5 new tests)

Test plan

• Verified bug exists on current main: resolve_provider("custom") returns "openrouter"
• Verified no existing PRs address [Bug]: 'custom' provider gets switched to 'openrouter' #2562
• After fix: resolve_provider("custom") returns "custom"
• After fix: resolve_runtime_provider(requested="custom") returns provider: "custom" with correct base_url
• resolve_provider("openrouter") still returns "openrouter" (no regression)
• 5 new tests: 2 for resolve_provider(), 3 for resolve_runtime_provider() custom flow
• All 34 tests in test_runtime_provider_resolution.py pass
• Run full test suite: pytest tests/ -x -q