docs: document named custom providers

maintainer edit: explain how to configure arbitrary OpenAI-compatible provider names, including multiple endpoints, model presets, and troubleshooting guidance.

docs/configuration.md

@@ -205,6 +205,7 @@ Tracing covers the providers that go through nanobot's OpenAI-compatible client
 > - **Step Fun (Mainland China)**: If your API key is from Step Fun's mainland China platform (stepfun.com), set `"apiBase": "https://api.stepfun.com/v1"` in your stepfun provider config.
 > - **Xiaomi MiMo thinking mode**: MiMo models (e.g. `mimo-v2.5-pro`) default to enabled thinking. Use `agents.defaults.reasoningEffort: "none"` to disable it, or `"low"` / `"medium"` / `"high"` to keep it on. Omitting the field preserves the provider's per-model default.
 > - **Xiaomi MiMo Token Plan**: If you're on MiMo's token plan, set `"apiBase": "https://token-plan-sgp.xiaomimimo.com/v1"` in your xiaomi_mimo provider config.
+> - **Custom OpenAI-compatible providers**: Besides the built-in `custom` provider, any extra key under `providers` can define its own OpenAI-compatible endpoint. For example, `providers.companyProxy.apiBase` plus `modelPresets.primary.provider: "companyProxy"` creates a separate custom provider. Set `apiBase`; set `apiKey` only when the endpoint requires it.
 
 | Provider | Purpose | Get API Key |
 |----------|---------|-------------|

docs/provider-cookbook.md

@@ -207,6 +207,47 @@ nanobot agent -m "Hello!"
 
 `apiBase` is the HTTP base URL, not the model name. Include the version path when the service expects it, such as `/v1`. If the service requires a non-empty key but does not validate it, use a placeholder such as `"apiKey": "EMPTY"`.
 
+For multiple custom endpoints, do not overload the single `custom` block. Name each endpoint under `providers` and reference that same name from the preset:
+
+```json
+{
+  "providers": {
+    "workProxy": {
+      "apiKey": "${WORK_PROXY_API_KEY}",
+      "apiBase": "https://proxy.example.com/v1"
+    },
+    "lab-local": {
+      "apiBase": "http://127.0.0.1:8000/v1"
+    }
+  },
+  "modelPresets": {
+    "work": {
+      "label": "Work proxy",
+      "provider": "workProxy",
+      "model": "gpt-4o-mini",
+      "maxTokens": 4096,
+      "contextWindowTokens": 65536,
+      "temperature": 0.1
+    },
+    "lab": {
+      "label": "Lab local",
+      "provider": "lab-local",
+      "model": "served-model-name",
+      "maxTokens": 4096,
+      "contextWindowTokens": 65536,
+      "temperature": 0.1
+    }
+  },
+  "agents": {
+    "defaults": {
+      "modelPreset": "work"
+    }
+  }
+}
+```
+
+These custom names behave like direct OpenAI-compatible providers: `apiBase` is required, `apiKey` is optional when the endpoint allows anonymous or placeholder credentials, and `apiType` should be left unset.
+
 ## Recipe: Ollama Local Model
 
 This recipe applies when Ollama is already installed and the model has been pulled locally.

docs/providers.md

@@ -150,7 +150,7 @@ Anthropic direct uses the native Anthropic provider. Do not use an OpenRouter mo
 
 ### Custom OpenAI-Compatible Endpoint
 
-The `custom` provider fits OpenAI-compatible endpoints that are not represented by a named provider.
+The `custom` provider fits one OpenAI-compatible endpoint that is not represented by a named provider.
 
 ```json
 {
@@ -178,6 +178,43 @@ The `custom` provider fits OpenAI-compatible endpoints that are not represented
 
 `custom` does not infer a default base URL. Set `apiBase`.
 
+If you have more than one custom OpenAI-compatible endpoint, give each endpoint its own provider key under `providers` and use that same key in the model preset. The key can be a name that makes sense in your environment, such as `companyProxy`, `tenant-a`, or `dev-local`.
+
+```json
+{
+  "providers": {
+    "companyProxy": {
+      "apiKey": "${COMPANY_PROXY_API_KEY}",
+      "apiBase": "https://llm-proxy.example.com/v1"
+    },
+    "tenant-a": {
+      "apiBase": "https://tenant-a.example.com/v1"
+    }
+  },
+  "modelPresets": {
+    "company": {
+      "provider": "companyProxy",
+      "model": "gpt-4o-mini",
+      "maxTokens": 8192,
+      "contextWindowTokens": 65536
+    },
+    "tenantA": {
+      "provider": "tenant-a",
+      "model": "served-model-name",
+      "maxTokens": 8192,
+      "contextWindowTokens": 65536
+    }
+  },
+  "agents": {
+    "defaults": {
+      "modelPreset": "company"
+    }
+  }
+}
+```
+
+Custom provider keys are treated as direct OpenAI-compatible providers. `apiBase` is required because nanobot cannot know the endpoint URL. `apiKey` is optional for local servers or private proxies that do not require one. Do not set `apiType` on custom provider keys; `apiType` is only for `providers.openai`.
+
 ### Ollama
 
 Start Ollama separately, then point nanobot at the OpenAI-compatible endpoint.

docs/troubleshooting.md

@@ -102,7 +102,7 @@ Common config mistakes:
 | Symptom | Check |
 |---|---|
 | JSON parse error | Validate commas, braces, and quotes. Most docs examples are partial snippets to merge. |
-| Unknown or missing provider | Use provider registry names such as `openrouter`, `anthropic`, `openai`, `ollama`, `vllm`, `lm_studio`. |
+| Unknown or missing provider | Use provider registry names such as `openrouter`, `anthropic`, `openai`, `ollama`, `vllm`, `lm_studio`, or define a custom OpenAI-compatible provider key under `providers` and reference that exact key from the active preset. |
 | snake_case vs camelCase confusion | Both are accepted, but docs use camelCase because nanobot writes config with aliases such as `apiKey`, `modelPresets`, `intervalS`. |
 | Environment variable error | `${VAR_NAME}` references are resolved at startup. Set the variable before running nanobot. |
 | Edited config but behavior did not change | Restart `nanobot gateway`; long-running processes read config at startup. |