feat(providers): add tencent-tokenhub provider support

Registers tencent-tokenhub (https://tokenhub.tencentmaas.com/v1) as a
new API-key provider with model tencent/hy3-preview (256K context).

- PROVIDER_REGISTRY entry + TOKENHUB_API_KEY / TOKENHUB_BASE_URL env vars
- Aliases: tencent, tokenhub, tencent-cloud, tencentmaas
- openai_chat transport with is_tokenhub branch for top-level
  reasoning_effort (Hy3 is a reasoning model)
- tencent/hy3-preview:free added to OpenRouter curated list
- 60+ tests (provider registry, aliases, runtime resolution,
  credentials, model catalog, URL mapping, context length)
- Docs: integrations/providers.md, environment-variables.md,
  model-catalog.json

Author: simonweng <simonweng@tencent.com>
Salvaged from PR #16860 onto current main (resolved conflicts with
#16935 Azure Anthropic env-var hint tests and the --provider choices=
list removal in chat_parser).

agent/auxiliary_client.py

@@ -94,6 +94,10 @@ _PROVIDER_ALIASES = {
     "github-models": "copilot",
     "github-copilot-acp": "copilot-acp",
     "copilot-acp-agent": "copilot-acp",
+    "tencent": "tencent-tokenhub",
+    "tokenhub": "tencent-tokenhub",
+    "tencent-cloud": "tencent-tokenhub",
+    "tencentmaas": "tencent-tokenhub",
 }
 
 
@@ -166,6 +170,7 @@ _API_KEY_PROVIDER_AUX_MODELS: Dict[str, str] = {
     "opencode-go": "glm-5",
     "kilocode": "google/gemini-3-flash-preview",
     "ollama-cloud": "nemotron-3-nano:30b",
+    "tencent-tokenhub": "hy3-preview",
 }
 
 # Vision-specific model overrides for direct providers.

agent/model_metadata.py

@@ -52,6 +52,7 @@ _PROVIDER_PREFIXES: frozenset[str] = frozenset({
     "xiaomi",
     "arcee",
     "gmi",
+    "tencent-tokenhub",
     "custom", "local",
     # Common aliases
     "google", "google-gemini", "google-ai-studio",
@@ -60,6 +61,7 @@ _PROVIDER_PREFIXES: frozenset[str] = frozenset({
     "ollama",
     "stepfun", "opencode", "zen", "go", "vercel", "kilo", "dashscope", "aliyun", "qwen",
     "mimo", "xiaomi-mimo",
+    "tencent", "tokenhub", "tencent-cloud", "tencentmaas",
     "arcee-ai", "arceeai",
     "gmi-cloud", "gmicloud",
     "xai", "x-ai", "x.ai", "grok",
@@ -208,6 +210,8 @@ DEFAULT_CONTEXT_LENGTHS = {
     "grok": 131072,             # catch-all (grok-beta, unknown grok-*)
     # Kimi
     "kimi": 262144,
+    # Tencent — Hy3 Preview (Hunyuan) with 256K context window
+    "hy3-preview": 256000,
     # Nemotron — NVIDIA's open-weights series (128K context across all sizes)
     "nemotron": 131072,
     # Arcee
@@ -310,6 +314,7 @@ _URL_TO_PROVIDER: Dict[str, str] = {
     "api.xiaomimimo.com": "xiaomi",
     "xiaomimimo.com": "xiaomi",
     "api.gmi-serving.com": "gmi",
+    "tokenhub.tencentmaas.com": "tencent-tokenhub",
     "ollama.com": "ollama-cloud",
 }
 

agent/transports/chat_completions.py

@@ -188,6 +188,7 @@ class ChatCompletionsTransport(ProviderTransport):
         anthropic_max_out = params.get("anthropic_max_output")
         is_nvidia_nim = params.get("is_nvidia_nim", False)
         is_kimi = params.get("is_kimi", False)
+        is_tokenhub = params.get("is_tokenhub", False)
         reasoning_config = params.get("reasoning_config")
 
         if ephemeral is not None and max_tokens_fn:
@@ -219,6 +220,21 @@ class ChatCompletionsTransport(ProviderTransport):
                         _kimi_effort = _e
                 api_kwargs["reasoning_effort"] = _kimi_effort
 
+        # Tencent TokenHub: top-level reasoning_effort (unless thinking disabled)
+        if is_tokenhub:
+            _tokenhub_thinking_off = bool(
+                reasoning_config
+                and isinstance(reasoning_config, dict)
+                and reasoning_config.get("enabled") is False
+            )
+            if not _tokenhub_thinking_off:
+                _tokenhub_effort = "high"
+                if reasoning_config and isinstance(reasoning_config, dict):
+                    _e = (reasoning_config.get("effort") or "").strip().lower()
+                    if _e in ("low", "medium", "high"):
+                        _tokenhub_effort = _e
+                api_kwargs["reasoning_effort"] = _tokenhub_effort
+
         # extra_body assembly
         extra_body: Dict[str, Any] = {}