Fallback Providers

Hermes Agent has three layers of resilience that keep your sessions running when providers hit issues:

Credential pools — rotate across multiple API keys for the same provider (tried first)
Primary model fallback — automatically switches to a different provider:model when your main model fails
Auxiliary task fallback — independent provider resolution for side tasks like vision, compression, and web extraction

Credential pools handle same-provider rotation (e.g., multiple OpenRouter keys). This page covers cross-provider fallback. 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:

fallback_model:
  provider: openrouter
  model: anthropic/claude-sonnet-4

Both provider and model are required. If either is missing, the fallback is disabled.

Supported Providers

Provider	Value	Requirements
AI Gateway	`ai-gateway`	`AI_GATEWAY_API_KEY`
OpenRouter	`openrouter`	`OPENROUTER_API_KEY`
Nous Portal	`nous`	`hermes auth` (OAuth)
OpenAI Codex	`openai-codex`	`hermes model` (ChatGPT OAuth)
GitHub Copilot	`copilot`	`COPILOT_GITHUB_TOKEN`, `GH_TOKEN`, or `GITHUB_TOKEN`
GitHub Copilot ACP	`copilot-acp`	External process (editor integration)
Anthropic	`anthropic`	`ANTHROPIC_API_KEY` or Claude Code credentials
z.ai / GLM	`zai`	`GLM_API_KEY`
Kimi / Moonshot	`kimi-coding`	`KIMI_API_KEY`
MiniMax	`minimax`	`MINIMAX_API_KEY`
MiniMax (China)	`minimax-cn`	`MINIMAX_CN_API_KEY`
DeepSeek	`deepseek`	`DEEPSEEK_API_KEY`
NVIDIA NIM	`nvidia`	`NVIDIA_API_KEY` (optional: `NVIDIA_BASE_URL`)
Ollama Cloud	`ollama-cloud`	`OLLAMA_API_KEY`
Google Gemini (OAuth)	`google-gemini-cli`	`hermes model` (Google OAuth; optional: `HERMES_GEMINI_PROJECT_ID`)
Google AI Studio	`gemini`	`GOOGLE_API_KEY` (alias: `GEMINI_API_KEY`)
xAI (Grok)	`xai` (alias `grok`)	`XAI_API_KEY` (optional: `XAI_BASE_URL`)
AWS Bedrock	`bedrock`	Standard boto3 auth (`AWS_REGION` + `AWS_PROFILE` or `AWS_ACCESS_KEY_ID`)
Qwen Portal (OAuth)	`qwen-oauth`	`hermes model` (Qwen Portal OAuth; optional: `HERMES_QWEN_BASE_URL`)
OpenCode Zen	`opencode-zen`	`OPENCODE_ZEN_API_KEY`
OpenCode Go	`opencode-go`	`OPENCODE_GO_API_KEY`
Kilo Code	`kilocode`	`KILOCODE_API_KEY`
Xiaomi MiMo	`xiaomi`	`XIAOMI_API_KEY`
Arcee AI	`arcee`	`ARCEEAI_API_KEY`
Alibaba / DashScope	`alibaba`	`DASHSCOPE_API_KEY`
Hugging Face	`huggingface`	`HF_TOKEN`
Custom endpoint	`custom`	`base_url` + `key_env` (see below)

Custom Endpoint Fallback

For a custom OpenAI-compatible endpoint, add base_url and optionally key_env:

fallback_model:
  provider: custom
  model: my-local-model
  base_url: http://localhost:8000/v1
  key_env: MY_LOCAL_KEY              # env var name containing the API key

When Fallback Triggers

The fallback activates automatically when the primary model fails with:

Rate limits (HTTP 429) — after exhausting retry attempts
Server errors (HTTP 500, 502, 503) — after exhausting retry attempts
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:

Resolves credentials for the fallback provider
Builds a new API client
Swaps the model, provider, and client in-place
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.

Per-Turn, Not Per-Session

Fallback is turn-scoped: each new user message starts with the primary model restored. If the primary fails mid-turn, fallback activates for that turn only. On the next message, Hermes tries the primary again. Within a single turn, fallback activates at most once — if the fallback also fails, normal error handling takes over (retries, then error message). This prevents cascading failover loops within a turn while giving the primary model a fresh chance every turn.

Examples

OpenRouter as fallback for Anthropic native:

model:
  provider: anthropic
  default: claude-sonnet-4-6

fallback_model:
  provider: openrouter
  model: anthropic/claude-sonnet-4

Nous Portal as fallback for OpenRouter:

model:
  provider: openrouter
  default: anthropic/claude-opus-4

fallback_model:
  provider: nous
  model: nous-hermes-3

Local model as fallback for cloud:

fallback_model:
  provider: custom
  model: llama-3.1-70b
  base_url: http://localhost:8000/v1
  key_env: LOCAL_API_KEY

Codex OAuth as fallback:

fallback_model:
  provider: openai-codex
  model: gpt-5.3-codex

Where Fallback Works

Context	Fallback Supported
CLI sessions	✔
Messaging gateway (Telegram, Discord, etc.)	✔
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.

Tasks with Independent Provider Resolution

Task	What It Does	Config Key
Vision	Image analysis, browser screenshots	`auxiliary.vision`
Web Extract	Web page summarization	`auxiliary.web_extract`
Compression	Context compression summaries	`auxiliary.compression`
Session Search	Past session summarization	`auxiliary.session_search`
Skills Hub	Skill search and discovery	`auxiliary.skills_hub`
MCP	MCP helper operations	`auxiliary.mcp`
Memory Flush	Memory consolidation	`auxiliary.flush_memories`
Approval	Smart command-approval classification	`auxiliary.approval`
Title Generation	Session title summaries	`auxiliary.title_generation`

Auto-Detection Chain

When a task's provider is set to "auto" (the default), Hermes tries providers in order until one works:

For text tasks (compression, web extract, etc.):

OpenRouter → Nous Portal → Custom endpoint → Codex OAuth →
API-key providers (z.ai, Kimi, MiniMax, Xiaomi MiMo, Hugging Face, Anthropic) → give up

For vision tasks:

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:

auxiliary:
  vision:
    provider: "auto"              # auto | openrouter | nous | codex | main | anthropic
    model: ""                     # e.g. "openai/gpt-4o"
    base_url: ""                  # direct endpoint (takes precedence over provider)
    api_key: ""                   # API key for base_url

  web_extract:
    provider: "auto"
    model: ""

  compression:
    provider: "auto"
    model: ""

  session_search:
    provider: "auto"
    model: ""
    timeout: 30
    max_concurrency: 3
    extra_body: {}

  skills_hub:
    provider: "auto"
    model: ""

  mcp:
    provider: "auto"
    model: ""

  flush_memories:
    provider: "auto"
    model: ""

Every task above follows the same provider / model / base_url pattern. Context compression is configured under auxiliary.compression:

auxiliary:
  compression:
    provider: main                                    # Same provider options as other auxiliary tasks
    model: google/gemini-3-flash-preview
    base_url: null                                    # Custom OpenAI-compatible endpoint

And the fallback model uses:

fallback_model:
  provider: openrouter
  model: anthropic/claude-sonnet-4
  # base_url: http://localhost:8000/v1               # Optional custom endpoint

For auxiliary.session_search, Hermes also supports:

max_concurrency to limit how many session summaries run at once
extra_body to pass provider-specific OpenAI-compatible request fields through on the summarization calls

Example:

auxiliary:
  session_search:
    provider: main
    model: glm-4.5-air
    max_concurrency: 2
    extra_body:
      enable_thinking: false

If your provider does not support a native OpenAI-compatible reasoning-control field, extra_body will not help for that part; in that case max_concurrency is still useful for reducing request-burst 429s.

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).

Provider Options for Auxiliary Tasks

These options apply to auxiliary:, compression:, and fallback_model: configs only — "main" is not a valid value for your top-level model.provider. For custom endpoints, use provider: custom in your model: section (see AI Providers).

Provider	Description	Requirements
`"auto"`	Try providers in order until one works (default)	At least one provider configured
`"openrouter"`	Force OpenRouter	`OPENROUTER_API_KEY`
`"nous"`	Force Nous Portal	`hermes auth`
`"codex"`	Force Codex OAuth	`hermes model` → Codex
`"main"`	Use whatever provider the main agent uses (auxiliary tasks only)	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:

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 uses the auxiliary.compression config block to control which model and provider handles summarization:

auxiliary:
  compression:
    provider: "auto"                              # auto | openrouter | nous | main
    model: "google/gemini-3-flash-preview"

Legacy migration

Older configs with compression.summary_model / compression.summary_provider / compression.summary_base_url are automatically migrated to auxiliary.compression.* on first load (config version 17).

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:

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 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:

cronjob(
    action="create",
    schedule="every 2h",
    prompt="Check server status",
    provider="openrouter",
    model="google/gemini-3-flash-preview"
)

See Scheduled Tasks (Cron) for full configuration details.

Summary

Feature	Fallback Mechanism	Config Location
Main agent model	`fallback_model` in config.yaml — per-turn failover on errors (primary restored each turn)	`fallback_model:` (top-level)
Vision	Auto-detection chain + internal OpenRouter retry	`auxiliary.vision`
Web extraction	Auto-detection chain + internal OpenRouter retry	`auxiliary.web_extract`
Context compression	Auto-detection chain, degrades to no-summary if unavailable	`auxiliary.compression`
Session search	Auto-detection chain	`auxiliary.session_search`
Skills hub	Auto-detection chain	`auxiliary.skills_hub`
MCP helpers	Auto-detection chain	`auxiliary.mcp`
Memory flush	Auto-detection chain	`auxiliary.flush_memories`
Approval classification	Auto-detection chain	`auxiliary.approval`
Title generation	Auto-detection chain	`auxiliary.title_generation`
Delegation	Provider override only (no automatic fallback)	`delegation.provider` / `delegation.model`
Cron jobs	Per-job provider override only (no automatic fallback)	Per-job `provider` / `model`

Primary Model Fallback​

Configuration​

Supported Providers​

Custom Endpoint Fallback​

When Fallback Triggers​

Examples​

Where Fallback Works​

Auxiliary Task Fallback​

Tasks with Independent Provider Resolution​

Auto-Detection Chain​

Configuring Auxiliary Providers​

Provider Options for Auxiliary Tasks​

Direct Endpoint Override​

Context Compression Fallback​

Delegation Provider Override​

Cron Job Providers​

Summary​