fix(opencode-go): keep users on opencode-go instead of hijacking to native providers (#20802)

OpenCode Go and OpenCode Zen are flat-namespace model resellers — their
/v1/models returns bare IDs (deepseek-v4-flash, minimax-m2.7), and the
inference API rejects vendor-prefixed names with HTTP 401 'Model not
supported'. Two bugs fixed:

1. `switch_model` in hermes_cli/model_switch.py was silently switching the
   user off opencode-go to native deepseek when they typed
   `/model deepseek-v4-flash`. Step d found the model in opencode-go's live
   catalog, but step e (detect_provider_for_model) still ran and matched
   the bare name against deepseek's static catalog. Fix: track whether
   the live catalog resolved it; skip step e when it did.

2. `normalize_model_for_provider` in hermes_cli/model_normalize.py only
   stripped the exact `opencode-zen/` prefix, leaving arbitrary vendor
   prefixes like `minimax/minimax-m2.7` (commonly copied from aggregator
   slugs into fallback_model configs) intact — causing HTTP 401s when
   the fallback chain activated. Fix: opencode-go/opencode-zen strip ANY
   leading vendor prefix because their APIs are flat-namespace.

Tests: 11 new cases in tests/hermes_cli/test_opencode_go_flat_namespace.py
covering both normalization (prefix stripping, regression guards for
opencode-zen Claude hyphenation and openrouter vendor-prepending) and
switch_model (bare-name resolution on opencode-go's live catalog must
not trigger cross-provider hijack).

Reported by @Ufonik via Discord; Kimi K2.6 always worked because moonshotai
has no overlapping entry in a native provider's static catalog. Deepseek
and minimax failed because their v4/v2.7 names existed in the native
deepseek/minimax catalogs.

hermes_cli/model_normalize.py

@@ -393,14 +393,21 @@ def normalize_model_for_provider(model_input: str, target_provider: str) -> str:
     if provider in _AGGREGATOR_PROVIDERS:
         return _prepend_vendor(name)
 
-    # --- OpenCode Zen: Claude stays hyphenated; other models keep dots ---
-    if provider == "opencode-zen":
-        bare = _strip_matching_provider_prefix(name, provider)
-        if "/" in bare:
-            return bare
-        if bare.lower().startswith("claude-"):
-            return _dots_to_hyphens(bare)
-        return bare
+    # --- OpenCode Zen / OpenCode Go: flat-namespace resellers.
+    #     Their /v1/models API returns bare IDs only (no vendor prefix), and
+    #     the inference endpoint rejects vendor-prefixed names with HTTP 401
+    #     "Model not supported".  Strip ANY leading ``vendor/`` so config
+    #     entries like ``minimax/minimax-m2.7`` or ``deepseek/deepseek-v4-flash``
+    #     — commonly copied from aggregator slugs into fallback_model lists —
+    #     resolve to bare ``minimax-m2.7`` / ``deepseek-v4-flash`` the API
+    #     actually serves.  See PR reviewing opencode-go fallback 401s. ---
+    if provider in {"opencode-zen", "opencode-go"}:
+        if "/" in name:
+            _, bare_after_slash = name.split("/", 1)
+            name = bare_after_slash.strip() or name
+        if provider == "opencode-zen" and name.lower().startswith("claude-"):
+            return _dots_to_hyphens(name)
+        return name
 
     # --- Anthropic: strip matching provider prefix, dots -> hyphens ---
     if provider in _DOT_TO_HYPHEN_PROVIDERS:

hermes_cli/model_switch.py

@@ -799,6 +799,12 @@ def switch_model(
                         )
 
         # --- Step d: Aggregator catalog search ---
+        # Track whether the live catalog of the CURRENT provider resolved the
+        # model — if so, step e must not second-guess and switch providers.
+        # Critical for flat-namespace resellers like opencode-go / opencode-zen
+        # whose live /v1/models returns bare IDs (e.g. "deepseek-v4-flash") that
+        # coincidentally match entries in native providers' static catalogs.
+        resolved_in_current_catalog = False
         if is_aggregator(target_provider) and not resolved_alias:
             catalog = list_provider_models(target_provider)
             if catalog:
@@ -806,6 +812,7 @@ def switch_model(
                 for mid in catalog:
                     if mid.lower() == new_model_lower:
                         new_model = mid
+                        resolved_in_current_catalog = True
                         break
                 else:
                     for mid in catalog:
@@ -813,6 +820,7 @@ def switch_model(
                             _, bare = mid.split("/", 1)
                             if bare.lower() == new_model_lower:
                                 new_model = mid
+                                resolved_in_current_catalog = True
                                 break
 
         # --- Step e: detect_provider_for_model() as last resort ---
@@ -825,6 +833,7 @@ def switch_model(
             target_provider == current_provider
             and not is_custom
             and not resolved_alias
+            and not resolved_in_current_catalog
         ):
             detected = detect_provider_for_model(new_model, current_provider)
             if detected:

tests/hermes_cli/test_opencode_go_flat_namespace.py

@@ -0,0 +1,159 @@
+"""Tests for opencode-go / opencode-zen flat-namespace model handling.
+
+OpenCode Go is NOT a vendor/model aggregator like OpenRouter — its
+``/v1/models`` endpoint returns bare IDs (``minimax-m2.7``, ``deepseek-v4-flash``)
+and the inference API rejects vendor-prefixed names with HTTP 401
+"Model not supported".
+
+Two bugs this exercises:
+
+1. ``switch_model('deepseek-v4-flash', current_provider='opencode-go')`` used
+   to silently switch the user off opencode-go to native ``deepseek`` because
+   ``detect_provider_for_model`` matched the bare name against the static
+   deepseek catalog.  Fix: once step d matches the model in the current
+   aggregator's live catalog, skip ``detect_provider_for_model``.
+
+2. ``normalize_model_for_provider('minimax/minimax-m2.7', 'opencode-go')``
+   used to pass the ``minimax/`` prefix through unchanged.  When user configs
+   contained prefixed fallback entries (commonly copied from aggregator slugs),
+   the fallback activation path sent ``minimax/minimax-m2.7`` to opencode-go
+   which returned HTTP 401.  Fix: opencode-go/opencode-zen strip ANY leading
+   ``vendor/`` prefix because their APIs are flat-namespace.
+"""
+
+from unittest.mock import patch
+
+from hermes_cli.model_normalize import normalize_model_for_provider
+from hermes_cli.model_switch import switch_model
+
+
+# Live catalog opencode-go currently returns from /v1/models (snapshot).
+_OPENCODE_GO_LIVE = [
+    "minimax-m2.7", "minimax-m2.5",
+    "kimi-k2.6", "kimi-k2.5",
+    "glm-5.1", "glm-5",
+    "deepseek-v4-pro", "deepseek-v4-flash",
+    "qwen3.6-plus", "qwen3.5-plus",
+    "mimo-v2-pro", "mimo-v2-omni", "mimo-v2.5-pro", "mimo-v2.5",
+]
+
+
+# ---------------------------------------------------------------------------
+# normalize_model_for_provider: strip vendor prefix for flat-namespace providers
+# ---------------------------------------------------------------------------
+
+
+def test_opencode_go_strips_deepseek_prefix():
+    assert normalize_model_for_provider(
+        "deepseek/deepseek-v4-flash", "opencode-go"
+    ) == "deepseek-v4-flash"
+
+
+def test_opencode_go_strips_minimax_prefix():
+    assert normalize_model_for_provider(
+        "minimax/minimax-m2.7", "opencode-go"
+    ) == "minimax-m2.7"
+
+
+def test_opencode_go_strips_moonshotai_prefix():
+    # Moonshot's aggregator vendor is `moonshotai/...` — a common copy-paste
+    # from OpenRouter slugs.  opencode-go serves it bare as `kimi-k2.6`.
+    assert normalize_model_for_provider(
+        "moonshotai/kimi-k2.6", "opencode-go"
+    ) == "kimi-k2.6"
+
+
+def test_opencode_go_bare_name_unchanged():
+    assert normalize_model_for_provider(
+        "kimi-k2.6", "opencode-go"
+    ) == "kimi-k2.6"
+
+
+def test_opencode_go_preserves_dot_versioning():
+    # opencode-go uses dot-versioned IDs (`mimo-v2.5-pro`, not hyphen).
+    assert normalize_model_for_provider(
+        "xiaomi/mimo-v2.5-pro", "opencode-go"
+    ) == "mimo-v2.5-pro"
+
+
+def test_opencode_zen_still_hyphenates_claude():
+    # Regression: opencode-zen's Claude hyphen conversion must still work.
+    assert normalize_model_for_provider(
+        "anthropic/claude-sonnet-4.6", "opencode-zen"
+    ) == "claude-sonnet-4-6"
+
+
+def test_opencode_zen_bare_claude_hyphenated():
+    assert normalize_model_for_provider(
+        "claude-sonnet-4.6", "opencode-zen"
+    ) == "claude-sonnet-4-6"
+
+
+def test_opencode_zen_strips_arbitrary_vendor_prefix():
+    assert normalize_model_for_provider(
+        "minimax/minimax-m2.5-free", "opencode-zen"
+    ) == "minimax-m2.5-free"
+
+
+def test_openrouter_still_prepends_vendor():
+    # Regression: real aggregators must still get vendor/model format.
+    assert normalize_model_for_provider(
+        "claude-sonnet-4.6", "openrouter"
+    ) == "anthropic/claude-sonnet-4.6"
+
+
+# ---------------------------------------------------------------------------
+# switch_model: live-catalog match on opencode-go must not trigger
+# cross-provider auto-switch via detect_provider_for_model
+# ---------------------------------------------------------------------------
+
+
+def _run_switch(raw_input: str, **extra):
+    """Call switch_model with opencode-go as current provider, mocking the
+    live catalog so the test doesn't hit the network."""
+    defaults = dict(
+        current_provider="opencode-go",
+        current_model="kimi-k2.6",
+        current_base_url="https://opencode.ai/zen/go/v1",
+        current_api_key="sk-test-opencode-go",
+        is_global=False,
+    )
+    defaults.update(extra)
+
+    def fake_list_provider_models(provider: str):
+        if provider == "opencode-go":
+            return list(_OPENCODE_GO_LIVE)
+        # For other providers, return empty so tests don't depend on them.
+        return []
+
+    with patch(
+        "hermes_cli.model_switch.list_provider_models",
+        side_effect=fake_list_provider_models,
+    ):
+        return switch_model(raw_input=raw_input, **defaults)
+
+
+def test_deepseek_v4_flash_stays_on_opencode_go():
+    """Regression: ``/model deepseek-v4-flash`` while on opencode-go must
+    NOT switch to native deepseek just because deepseek's static catalog
+    also contains that name."""
+    result = _run_switch("deepseek-v4-flash")
+    assert result.target_provider == "opencode-go", (
+        f"Expected to stay on opencode-go, got {result.target_provider}. "
+        f"detect_provider_for_model hijacked the bare name."
+    )
+    assert result.new_model == "deepseek-v4-flash"
+
+
+def test_deepseek_v4_pro_stays_on_opencode_go():
+    """Same bug class as the flash variant."""
+    result = _run_switch("deepseek-v4-pro")
+    assert result.target_provider == "opencode-go"
+    assert result.new_model == "deepseek-v4-pro"
+
+
+def test_kimi_k2_6_stays_on_opencode_go():
+    """Regression guard: this path was always working, keep it working."""
+    result = _run_switch("kimi-k2.6", current_model="deepseek-v4-pro")
+    assert result.target_provider == "opencode-go"
+    assert result.new_model == "kimi-k2.6"