Adding a Fallback Model to Hermes with Microsoft Foundry
So the plan was simple. Leave the Bedrock configuration untouched, then wire Microsoft Foundry in behind it as a fallback, so Hermes always has somewhere else to go when the primary provider is not responding. A few other reasons pushed me towards Foundry in particular: Redundancy that does not need me. If Bedrock is throttled or out of quota, I want Hermes to fail over on its own rather than waiting for me to notice. A catalogue I already pay for. Foundry puts the latest GPT models next to open-weight and partner models in one place, so I can pick a model that suits the task instead of settling for whatever a single provider happens to offer. Enterprise controls out of the box. Region pinning, private networking, content filters and per-deployment quota all sit in the same portal, which makes the setup far easier to defend to a security reviewer. Learning the mechanics before I need them. Working out how Hermes handles a provider chain is much nicer on a quiet Tuesday than during a live outage. Here is the short version, if you are deciding whether to read on. Time: about thirty minutes if nothing goes wrong. Cost: pay-as-you-go tokens only, and none at all while the fallback sits idle. Result: an assistant that keeps answering when your primary provider stops. Before you start, you will need three things: a machine with Hermes already installed and a working primary provider configured, an Azure subscription with access to Microsoft Foundry in a region you can actually deploy into, and enough quota in that region to create a deployment. One thing that made this easy to justify: Foundry deployments bill per token on the standard pay-as-you-go tier. A fallback provider that never gets invoked costs nothing beyond the requests it actually serves, so the insurance is close to free until the day you need it. Chat surface (CLI, messaging) → Hermes Gateway → Primary Amazon Bedrock → Fallback Microsoft Foundry Figure 1: Where the fallback sits. Every request goes through the Hermes gateway to the primary provider; only when that provider is unavailable does the chain continue to Microsoft Foundry. Part 1: Deploying a Model on Microsoft Foundry The first half of this job happens entirely inside the Microsoft Foundry portal and has nothing to do with Hermes yet. All you are really doing here is making sure your Azure subscription can serve a model, and that you hold an endpoint and key Hermes can authenticate with later. 1. Deploy model in Foundry → 2. Copy endpoint + key → 3. hermes fallback add → 4. Authenticate → 5. Select models, test Figure 2: The whole setup in five moves. The first two happen in the Microsoft Foundry portal (orange); the rest happen on the Hermes machine (blue). Go to Microsoft Foundry > Build > Models > Deploy > Deploy a base model. You can deploy a fine-tuned model instead if you already have one, which works just as well with Hermes. Check the region shown at the top of the portal before you commit, because both model availability and deployment quota differ from one region to the next. Then deploy the model you have selected: In this case I deployed gpt-5.6-sol, which is the model Hermes will fall back to. The choice was deliberate rather than exciting. My primary model on Bedrock is a general-purpose chat model, and a fallback is only useful if the answers it gives feel like a continuation of the same conversation rather than a different assistant wearing the same name. The gpt-5.6-sol deployment matches that behaviour closely, it was available in the region I wanted to pin, and the quota I was granted comfortably covers a day of normal use. If a fallback surprises you the first time it fires, it is the wrong fallback. Once the deployment finishes, open it and take note of two values: the target endpoint URI and the API key. Copy both somewhere safe now, because you will be pasting them into Hermes in the next part. If your organisation rotates keys on a schedule, use a key with the longest life you are allowed, since a fallback secured with a credential that expires quietly stops being a fallback. What to copy Where it lives in the portal Where Hermes asks for it Target endpoint URI Deployment > Endpoint > Target URI "Endpoint" prompt in hermes fallback add API key Deployment > Endpoint > Key "API key" prompt, or choose Entra ID instead Deployment name Deployment > Details > Name Shown in the model list Hermes returns Region Top of the portal, next to the resource Must match the region you deployed into Figure 3: Everything Hermes will ask for, and where to find each value before you leave the portal. Part 2: Adding Foundry to Hermes as a Fallback With the Foundry side sorted, everything from here happens in the Hermes CLI. One thing worth knowing before you start: this is the fallback command, not the primary model command, so your existing Bedrock configuration is left completely alone. Nothing in this section can break what is already working, which makes it a good one to try on a live setup. Run the Hermes fallback command: When Hermes asks which provider to add, choose Azure Foundry. The picker still carries the old name; it is the same service that the portal now calls Microsoft Foundry. Paste the target endpoint URI from your deployment, then authenticate with the API key you copied earlier. Hermes also offers Microsoft Entra ID at this prompt, which is the better option if your organisation would rather not have a static key sitting on the machine. If authentication fails here, check the endpoint before you start suspecting the key. In my experience the endpoint is wrong far more often than the credential is, usually because the deployment name at the end of the URI does not match the deployment you actually created. Once authentication succeeds, Hermes lists the deployments your Foundry resource exposes and asks which ones you want to use. You can select more than one, and the order is not cosmetic: Hermes walks down the chain from top to bottom whenever the provider above is unavailable. Treat that list as a priority order, not a shopping basket. What happens to the primary What Hermes does What you see in the chat Responds normally Routes every request to the primary and never touches the chain Nothing. The fallback stays idle Throttled or out of quota Retries the next provider down the chain on the same request A reply, served by the fallback model Endpoint unreachable Keeps failing over on each new request until the primary recovers Slightly different tone and latency, but a working assistant Every provider fails Returns the error rather than hanging An error worth chasing with hermes status Figure 4: The chain in practice. The fallback only earns its keep in the middle two rows, which is exactly why it is easy to forget you configured it. Part 3: Promoting Foundry to the Primary Model At this stage Foundry is sitting in the back seat as a backup. I wanted to reverse the arrangement and make Foundry the primary while Bedrock slides down into the fallback slot, partly because I preferred keeping day-to-day traffic inside my Azure subscription, and partly because I wanted proof the chain works in both directions. Before promotion After promotion Primary: Amazon Bedrock → Primary: Microsoft Foundry Fallback: Microsoft Foundry → Fallback: Amazon Bedrock Figure 5: The promotion, in effect. Nothing is added or removed; the two providers simply trade places in the chain. There is no dedicated "promote" command in Hermes, so the manual route is a short sequence of steps rather than a single instruction: Select the fallback provider/model as the new primary: hermes model Remove the now-duplicate model from the fallback chain: hermes fallback remove Optionally add the old primary model as a fallback: hermes fallback add Restart the messaging gateway: hermes gateway restart Verify the result: hermes status / hermes fallback list That sequence works, and it is good to know what is happening underneath. But since I already had a working provider configured, I would rather just ask Hermes to rearrange itself. This is the part I genuinely enjoy about the tool: the configuration is something you can talk to, not only something you type commands at. Prompt: Okay now please make the model I configured on Microsoft Foundry into the main model, and make the Bedrock one the fallback model! Hermes rewrites the provider chain on its own and confirms the swap once it is done, which is a great deal less error-prone than running the five commands by hand. Part 4: Testing the Switch Configuration you have not tested is just an assumption with extra steps, so the next thing is to confirm Hermes really is talking to Foundry. Type /model when running Hermes to bring up the model picker. You will be prompted to select a provider first. Pick the Microsoft Foundry entry, then choose the specific deployment from the list underneath it. The active model should switch straight away. Send it a plain "Hello" to check that the deployment actually responds, rather than just looking correct in the menu. Appearing in a dropdown and serving a request are two very different things. A second test is worth the thirty seconds it costs: run hermes status to confirm which provider is live, then hermes fallback list to confirm the chain is ordered the way you intended. The picker tells you what you selected; those two commands tell you what Hermes will actually do at three in the morning. Part 5: The Obstacle, and What It Actually Taught Me Every walkthrough has the part the author quietly leaves out. Here is mine: the wrinkle was not the model, it was capacity. My first attempt deployed into the region closest to me out of habit, and the portal turned it down because there was no capacity left for that model at the tier I asked for. The model was clearly listed in the catalogue; being listed and being deployable in your region, on your subscription, at your quota, are three separate questions. Redeploying in a different region fixed it in a couple of minutes, but it meant the endpoint URI changed, which in turn meant the value I had already pasted into Hermes was stale. Re-running hermes fallback add against the new endpoint sorted it out. The lesson is cheap enough to hand over for free: check quota and regional capacity for your specific subscription before you design a walkthrough, a demo or a production fallback around one deployment. In the Foundry portal, Management then Quota shows exactly what you have been granted per region and per model family, which is the only list that matters. Symptom Likely cause Fix Deployment rejected in the portal No capacity for that model at the tier you asked for, in that region Deploy in another region, or drop to a smaller tier Hermes rejects the credential Endpoint URI does not match the deployment you created Re-copy the target URI from the deployment, not the resource Provider authenticates but lists nothing Key belongs to a different Foundry resource Check you are in the right resource, then re-run hermes fallback add Fallback never fires Chain ordered the wrong way round hermes fallback list, then reorder Figure 6: The four things that went wrong, or nearly did, and what fixed each one. There is a silver lining worth stating plainly. Because the fallback chain was already in place, a deployment that refused to come up did not take the assistant down with it. That is precisely the scenario this whole exercise was meant to cover, and it turned up on day one without me having to simulate it. Command Cheat Sheet Everything used in this walkthrough, collected in one place: hermes fallback add: attach a provider to the fallback chain hermes fallback remove: drop a provider from the chain hermes fallback list: show the chain in priority order hermes model: set the primary model hermes gateway restart: restart the messaging gateway after a change hermes status: confirm which provider is currently live /model: switch models from inside a running session Conclusion Adding Microsoft Foundry as a fallback behind my existing Bedrock setup took an afternoon, and most of that was spent recovering from a regional capacity limit I should have checked first. The work itself is small: deploy a model, copy the endpoint and key, run hermes fallback add, authenticate, pick your deployments. The payoff is that Hermes no longer depends on one provider staying healthy. Three things are worth carrying away from this: Check quota, not just the catalogue. The Foundry catalogue shows what Microsoft offers. It does not show what your subscription and region can actually deploy today. Confirm that first, before you build anything on top of a specific deployment. Order your fallback chain deliberately. Hermes works down the list from top to bottom, so the sequence you choose during setup is the failover policy you are going to live with. Put the model you actually trust at the top. Treat the endpoint as part of the credential. Redeploying in a new region changes the endpoint URI, and a fallback pointed at an endpoint that no longer exists is not a fallback. Re-run the setup whenever the deployment moves. The switch from Bedrock primary to Foundry primary also proved the chain runs in both directions, which is the real point. Provider redundancy is only useful if you have watched it work. Next on my list is deliberately breaking the primary provider to confirm the failover triggers on its own, without me typing a single command. If you run this against a different model, region or provider pairing, I would genuinely like to know how it went, particularly if your quota experience was better than mine. Drop it in the comments.
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