description: Configure automatic failover to backup LLM providers when your primary model is unavailable.
sidebar_label: Fallback Providers
sidebar_position: 8
---
# Fallback Providers
Hermes Agent has two separate fallback systems that keep your sessions running when providers hit issues:
1.**Primary model fallback** — automatically switches to a backup provider:model when your main model fails
2.**Auxiliary task fallback** — independent provider resolution for side tasks like vision, compression, and web extraction
Both are optional and work independently.
## Primary Model Fallback
When your main LLM provider encounters errors — rate limits, server overload, auth failures, connection drops — Hermes can automatically switch to a backup provider:model pair mid-session without losing your conversation.
### Configuration
Add a `fallback_model` section to `~/.hermes/config.yaml`:
```yaml
fallback_model:
provider: openrouter
model: anthropic/claude-sonnet-4
```
Both `provider` and `model` are **required**. If either is missing, the fallback is disabled.
- **Auth failures** (HTTP 401, 403) — immediately (no point retrying)
- **Not found** (HTTP 404) — immediately
- **Invalid responses** — when the API returns malformed or empty responses repeatedly
When triggered, Hermes:
1. Resolves credentials for the fallback provider
2. Builds a new API client
3. Swaps the model, provider, and client in-place
4. Resets the retry counter and continues the conversation
The switch is seamless — your conversation history, tool calls, and context are preserved. The agent continues from exactly where it left off, just using a different model.
:::info One-Shot
Fallback activates **at most once** per session. If the fallback provider also fails, normal error handling takes over (retries, then error message). This prevents cascading failover loops.
| Subagent delegation | ✘ (subagents do not inherit fallback config) |
| Cron jobs | ✘ (run with a fixed provider) |
| Auxiliary tasks (vision, compression) | ✘ (use their own provider chain — see below) |
:::tip
There are no environment variables for `fallback_model` — it is configured exclusively through `config.yaml`. This is intentional: fallback configuration is a deliberate choice, not something a stale shell export should override.
:::
---
## Auxiliary Task Fallback
Hermes uses separate lightweight models for side tasks. Each task has its own provider resolution chain that acts as a built-in fallback system.
Main provider (if vision-capable) → OpenRouter → Nous Portal →
Codex OAuth → Anthropic → Custom endpoint → give up
```
If the resolved provider fails at call time, Hermes also has an internal retry: if the provider is not OpenRouter and no explicit `base_url` is set, it tries OpenRouter as a last-resort fallback.
### Configuring Auxiliary Providers
Each task can be configured independently in `config.yaml`:
```yaml
auxiliary:
vision:
provider: "auto" # auto | openrouter | nous | codex | main | anthropic
model: "" # e.g. "openai/gpt-4o"
base_url: "" # direct endpoint (takes precedence over provider)
All three — auxiliary, compression, fallback — work the same way: set `provider` to pick who handles the request, `model` to pick which model, and `base_url` to point at a custom endpoint (overrides provider).
| `"main"` | Use whatever provider the main agent uses | Active main provider configured |
| `"anthropic"` | Force Anthropic native | `ANTHROPIC_API_KEY` or Claude Code credentials |
### Direct Endpoint Override
For any auxiliary task, setting `base_url` bypasses provider resolution entirely and sends requests directly to that endpoint:
```yaml
auxiliary:
vision:
base_url: "http://localhost:1234/v1"
api_key: "local-key"
model: "qwen2.5-vl"
```
`base_url` takes precedence over `provider`. Hermes uses the configured `api_key` for authentication, falling back to `OPENAI_API_KEY` if not set. It does **not** reuse `OPENROUTER_API_KEY` for custom endpoints.
---
## Context Compression Fallback
Context compression has a legacy configuration path in addition to the auxiliary system:
```yaml
compression:
summary_provider: "auto" # auto | openrouter | nous | main
summary_model: "google/gemini-3-flash-preview"
```
This is equivalent to configuring `auxiliary.compression.provider` and `auxiliary.compression.model`. If both are set, the `auxiliary.compression` values take precedence.
If no provider is available for compression, Hermes drops middle conversation turns without generating a summary rather than failing the session.
---
## Delegation Provider Override
Subagents spawned by `delegate_task` do **not** use the primary fallback model. However, they can be routed to a different provider:model pair for cost optimization:
```yaml
delegation:
provider: "openrouter" # override provider for all subagents
model: "google/gemini-3-flash-preview" # override model
# base_url: "http://localhost:1234/v1" # or use a direct endpoint
# api_key: "local-key"
```
See [Subagent Delegation](/docs/user-guide/features/delegation) for full configuration details.
---
## Cron Job Providers
Cron jobs run with whatever provider is configured at execution time. They do not support a fallback model. To use a different provider for cron jobs, configure `provider` and `model` overrides on the cron job itself:
```python
cronjob(
action="create",
schedule="every 2h",
prompt="Check server status",
provider="openrouter",
model="google/gemini-3-flash-preview"
)
```
See [Scheduled Tasks (Cron)](/docs/user-guide/features/cron) for full configuration details.
