Stale base_url retained when switching model provider

Fixes on record

Merged to main. A stamp counts the issues a fix is linked to.

• #60985 fix(agent): switch_model refuses stale base_url on provider change (#47828)

  merged to main

  files: agent/agent_runtime_helpers.py, tests/run_agent/test_switch_model_stale_base_url.py

  Show the diff

  • agent/agent_runtime_helpers.py

    @@ -1805,13 +1805,30 @@ def switch_model(agent, new_model, new_provider, api_key='', base_url='', api_mo
             # ── Swap core runtime fields ──
             agent.model = new_model
             agent.provider = new_provider
    -        # Use new base_url when provided; only fall back to current when the
    -        # new provider genuinely has no endpoint (e.g. native SDK providers).
    -        # Without this guard the old provider's URL (e.g. Ollama's localhost
    -        # address) would persist silently after switching to a cloud provider
    -        # that returns an empty base_url string.
    +        # Use the new base_url when provided. When it's empty AND the
    +        # provider is actually changing, do NOT fall back to the current
    +        # (old provider's) URL — that silently pairs the new provider label
    +        # with the previous provider's endpoint (e.g. new_provider=minimax
    +        # paired with the leftover api.githubcopilot.com URL), and every
    +        # request after the switch 400s at the wrong host. This mismatched
    +        # pair also gets snapshotted into _primary_runtime below, so it
    +        # keeps re-applying on every subsequent turn until a full restart.
    +        # Fail loud instead: the caller (model_switch.switch_model())
    +        # already resolves base_url for every real provider, so an empty
    +        # value here means resolution failed upstream, not that the
    +        # provider genuinely has none. Re-selecting the SAME provider with
    +        # an empty base_url (e.g. a credential-only refresh) is still fine
    +        # to keep the current URL. See #47828.
    +        old_norm_provider = (old_provider or "").strip().lower()
    +        new_norm_provider = (new_provider or "").strip().lower()
             if base_url:
                 agent.base_url = base_url
    +        elif old_norm_provider != new_norm_provider:
    +            raise ValueError(
    +                f"switch_model: no base_url resolved for provider "
    +                f"'{new_provider}' (switching from '{old_provider}'); "
    +                "refusing to keep the previous provider's endpoint"
    +            )
             agent.api_mode = api_mode
             # Invalidate transport cache — new api_mode may need a different transport
             if hasattr(agent, "_transport_cache"):

  • tests/run_agent/test_switch_model_stale_base_url.py

    @@ -0,0 +1,87 @@
    +"""Regression tests for #47828: switch_model must not pair a new provider
    +label with the previous provider's base_url when the resolver returns no
    +new base_url for a genuine provider change.
    +"""
    +
    +from unittest.mock import MagicMock, patch
    +
    +import pytest
    +
    +from run_agent import AIAgent
    +from agent.context_compressor import ContextCompressor
    +
    +
    +def _make_agent_with_compressor(provider="copilot", base_url="https://api.githubcopilot.com") -> AIAgent:
    +    """Build a minimal AIAgent with a context_compressor, skipping __init__."""
    +    agent = AIAgent.__new__(AIAgent)
    +
    +    agent.model = "claude-opus-4.8"
    +    agent.provider = provider
    +    agent.base_url = base_url
    +    agent.api_key = "[redacted:secret-assignment]"
    +    agent.api_mode = "chat_completions"
    +    agent.client = MagicMock()
    +    agent.quiet_mode = True
    +    agent._config_context_length = None
    +
    +    compressor = ContextCompressor(
    +        model=agent.model,
    +        threshold_percent=0.50,
    +        base_url=base_url,
    +        api_key="[redacted:secret-assignment]",
    +        provider=provider,
    +        quiet_mode=True,
    +        config_context_length=None,
    +    )
    +    agent.context_compressor = compressor
    +    agent._primary_runtime = {}
    +
    +    return agent
    +
    +
    +@patch("agent.model_metadata.get_model_context_length", return_value=131_072)
    +def test_switch_model_rejects_stale_base_url_on_provider_change(mock_ctx_len):
    +    """A provider change with no resolved base_url must fail loud instead of
    +    silently keeping the previous provider's endpoint (#47828)."""
    +    agent = _make_agent_with_compressor(provider="copilot", base_url="https://api.githubcopilot.com")
    +
    +    with pytest.raises(ValueError, match="no base_url resolved"):
    +        agent.switch_model("MiniMax-M3", "custom:minimax", api_key="[redacted:secret-assignment]", base_url="")
    +
    +    # Rollback must leave the agent fully on the old (provider, base_url) pair —
    +    # not a mismatched new-model/old-endpoint hybrid.
    +    assert agent.provider == "copilot"
    +    assert agent.base_url == "https://api.githubcopilot.com"
    +    assert agent.model == "claude-opus-4.8"
    +
    +
    +@patch("agent.model_metadata.get_model_context_length", return_value=131_072)
    +def test_switch_model_allows_empty_base_url_for_same_provider(mock_ctx_len):
    +    """Re-selecting the SAME provider (e.g. a credential-only refresh) with no
    +    new base_url must keep the current URL — this is not a provider change."""
    +    agent = _make_agent_with_compressor(provider="openrouter", base_url="https://openrouter.ai/api/v1")
    +
    +    agent.switch_model("new-model", "openrouter", api_key="[redacted:secret-assignment]", base_url="")
    +
    +    assert agent.provider == "openrouter"
    +    assert agent.base_url == "https://openrouter.ai/api/v1"
    +    assert agent.model == "new-model"
    +
    +
    +@patch("agent.model_metadata.get_model_context_length", return_value=131_072)
    +def test_switch_model_applies_new_base_url_on_provider_change(mock_ctx_len):
    +    """The normal, resolved-correctly path must still work: new provider +
    +    new base_url is applied as-is."""
    +    agent = _make_agent_with_compressor(provider="copilot", base_url="https://api.githubcopilot.com")
    +
    +    agent.switch_model(
    +        "MiniMax-M3", "custom:minimax", api_key="[redacted:secret-assignment]", base_url="https://api.minimax.io/v1"
    +    )
    +
    +    assert agent.provider == "custom:minimax"
    +    assert agent.base_url == "https://api.minimax.io/v1"
    +    assert agent.model == "MiniMax-M3"
    +    # _primary_runtime must snapshot the coherent pair so it survives every
    +    # subsequent restore_primary_runtime() call across turns.
    +    assert agent._primary_runtime["provider"] == "custom:minimax"
    +    assert agent._primary_runtime["base_url"] == "https://api.minimax.io/v1"