feat: add Arcee AI provider plugin

Add a bundled Arcee AI provider plugin with ARCEEAI_API_KEY onboarding,
Trinity model catalog (mini, large-preview, large-thinking), and
OpenAI-compatible API support.

- Trinity Large Thinking: 256K context, reasoning enabled
- Trinity Large Preview: 128K context, general-purpose
- Trinity Mini 26B: 128K context, fast and cost-efficient

docs/providers/arcee.md

@@ -0,0 +1,74 @@
+---
+title: "Arcee AI"
+summary: "Arcee AI setup (auth + model selection)"
+read_when:
+  - You want to use Arcee AI with OpenClaw
+  - You need the API key env var or CLI auth choice
+---
+
+# Arcee AI
+
+[Arcee AI](https://arcee.ai) provides access to the Trinity family of mixture-of-experts models through an OpenAI-compatible API. All Trinity models are Apache 2.0 licensed.
+
+- Provider: `arcee`
+- Auth: `ARCEEAI_API_KEY`
+- API: OpenAI-compatible
+- Base URL: `https://api.arcee.ai/api/v1`
+
+## Quick start
+
+1. Get an API key from the [Arcee platform dashboard](https://app.arcee.ai).
+
+2. Set the API key (recommended: store it for the Gateway):
+
+```bash
+openclaw onboard --auth-choice arceeai-api-key
+```
+
+3. Set a default model:
+
+```json5
+{
+  agents: {
+    defaults: {
+      model: { primary: "arcee/trinity-large-thinking" },
+    },
+  },
+}
+```
+
+## Non-interactive example
+
+```bash
+openclaw onboard --non-interactive \
+  --mode local \
+  --auth-choice arceeai-api-key \
+  --arceeai-api-key "$ARCEEAI_API_KEY"
+```
+
+This will set `arcee/trinity-large-thinking` as the default model.
+
+## Environment note
+
+If the Gateway runs as a daemon (launchd/systemd), make sure `ARCEEAI_API_KEY`
+is available to that process (for example, in `~/.openclaw/.env` or via
+`env.shellEnv`).
+
+## Built-in catalog
+
+OpenClaw currently ships this bundled Arcee catalog:
+
+| Model ref                      | Name                   | Input | Context | Cost (in/out per 1M) | Notes                                     |
+| ------------------------------ | ---------------------- | ----- | ------- | -------------------- | ----------------------------------------- |
+| `arcee/trinity-large-thinking` | Trinity Large Thinking | text  | 256K    | $0.25 / $0.90        | Default model; reasoning enabled          |
+| `arcee/trinity-large-preview`  | Trinity Large Preview  | text  | 128K    | $0.25 / $1.00        | General-purpose; 400B params, 13B active  |
+| `arcee/trinity-mini`           | Trinity Mini 26B       | text  | 128K    | $0.045 / $0.15       | Fast and cost-efficient; function calling |
+
+The onboarding preset sets `arcee/trinity-large-thinking` as the default model.
+
+## Supported features
+
+- Streaming
+- Tool use / function calling
+- Structured output (JSON mode and JSON schema)
+- Extended thinking (Trinity Large Thinking)

docs/providers/index.md

@@ -29,6 +29,7 @@ Looking for chat channel docs (WhatsApp/Telegram/Discord/Slack/Mattermost (plugi
 - [Alibaba Model Studio](/providers/alibaba)
 - [Amazon Bedrock](/providers/bedrock)
 - [Anthropic (API + Claude CLI)](/providers/anthropic)
+- [Arcee AI (Trinity models)](/providers/arcee)
 - [BytePlus (International)](/concepts/model-providers#byteplus-international)
 - [Chutes](/providers/chutes)
 - [ComfyUI](/providers/comfy)