From dac7474da2379bf1027f5fbddc06108399bed4e5 Mon Sep 17 00:00:00 2001
From: jake <void@synchropoiesis.ink>
Date: Mon, 19 Jan 2026 20:39:04 +0200
Subject: [PATCH] feat(ai): add OpenRouter provider routing support

Allows custom models to specify which upstream providers OpenRouter
should route requests to via the `openRouterRouting` field in model
definitions.

Supported fields:
- `only`: list of provider slugs to exclusively use
- `order`: list of provider slugs to try in order
---
 packages/ai/CHANGELOG.md                           |  1 +
 packages/ai/src/providers/openai-completions.ts    |  7 +++++++
 packages/ai/src/types.ts                           | 14 ++++++++++++++
 .../openai-completions-tool-result-images.test.ts  |  1 +
 packages/coding-agent/src/core/model-registry.ts   |  7 +++++++
 5 files changed, 30 insertions(+)

diff --git a/packages/ai/CHANGELOG.md b/packages/ai/CHANGELOG.md
index 17c1768c..392b4b18 100644
--- a/packages/ai/CHANGELOG.md
+++ b/packages/ai/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### Added
 
+- Added OpenRouter provider routing support for custom models via `openRouterRouting` compat field ([#859](https://github.com/badlogic/pi-mono/pull/859) by [@v01dpr1mr0s3](https://github.com/v01dpr1mr0s3))
 - Added `azure-openai-responses` provider support for Azure OpenAI Responses API. ([#890](https://github.com/badlogic/pi-mono/pull/890) by [@markusylisiurunen](https://github.com/markusylisiurunen))
 - Added `createAssistantMessageEventStream()` factory function for use in extensions.
 - Added `resetApiProviders()` to clear and re-register built-in API providers.
diff --git a/packages/ai/src/providers/openai-completions.ts b/packages/ai/src/providers/openai-completions.ts
index 46c62e9c..8c64cd28 100644
--- a/packages/ai/src/providers/openai-completions.ts
+++ b/packages/ai/src/providers/openai-completions.ts
@@ -445,6 +445,11 @@ function buildParams(model: Model<"openai-completions">, context: Context, optio
 		params.reasoning_effort = options.reasoningEffort;
 	}
 
+	// OpenRouter provider routing preferences
+	if (model.baseUrl.includes("openrouter.ai") && model.compat?.openRouterRouting) {
+		(params as any).provider = model.compat.openRouterRouting;
+	}
+
 	return params;
 }
 
@@ -777,6 +782,7 @@ function detectCompat(model: Model<"openai-completions">): Required<OpenAIComple
 		requiresThinkingAsText: isMistral,
 		requiresMistralToolIds: isMistral,
 		thinkingFormat: isZai ? "zai" : "openai",
+		openRouterRouting: {},
 	};
 }
 
@@ -800,5 +806,6 @@ function getCompat(model: Model<"openai-completions">): Required<OpenAICompletio
 		requiresThinkingAsText: model.compat.requiresThinkingAsText ?? detected.requiresThinkingAsText,
 		requiresMistralToolIds: model.compat.requiresMistralToolIds ?? detected.requiresMistralToolIds,
 		thinkingFormat: model.compat.thinkingFormat ?? detected.thinkingFormat,
+		openRouterRouting: model.compat.openRouterRouting ?? {},
 	};
 }
diff --git a/packages/ai/src/types.ts b/packages/ai/src/types.ts
index 75c36c3c..5308f142 100644
--- a/packages/ai/src/types.ts
+++ b/packages/ai/src/types.ts
@@ -214,6 +214,8 @@ export interface OpenAICompletionsCompat {
 	requiresMistralToolIds?: boolean;
 	/** Format for reasoning/thinking parameter. "openai" uses reasoning_effort, "zai" uses thinking: { type: "enabled" }. Default: "openai". */
 	thinkingFormat?: "openai" | "zai";
+	/** OpenRouter-specific routing preferences. Only used when baseUrl points to OpenRouter. */
+	openRouterRouting?: OpenRouterRouting;
 }
 
 /** Compatibility settings for OpenAI Responses APIs. */
@@ -221,6 +223,18 @@ export interface OpenAIResponsesCompat {
 	// Reserved for future use
 }
 
+/**
+ * OpenRouter provider routing preferences.
+ * Controls which upstream providers OpenRouter routes requests to.
+ * @see https://openrouter.ai/docs/provider-routing
+ */
+export interface OpenRouterRouting {
+	/** List of provider slugs to exclusively use for this request (e.g., ["amazon-bedrock", "anthropic"]). */
+	only?: string[];
+	/** List of provider slugs to try in order (e.g., ["anthropic", "openai"]). */
+	order?: string[];
+}
+
 // Model interface for the unified model system
 export interface Model<TApi extends Api> {
 	id: string;
diff --git a/packages/ai/test/openai-completions-tool-result-images.test.ts b/packages/ai/test/openai-completions-tool-result-images.test.ts
index 3a909022..36398f26 100644
--- a/packages/ai/test/openai-completions-tool-result-images.test.ts
+++ b/packages/ai/test/openai-completions-tool-result-images.test.ts
@@ -30,6 +30,7 @@ const compat: Required<OpenAICompletionsCompat> = {
 	requiresThinkingAsText: false,
 	requiresMistralToolIds: false,
 	thinkingFormat: "openai",
+	openRouterRouting: {},
 };
 
 function buildToolResult(toolCallId: string, timestamp: number): ToolResultMessage {
diff --git a/packages/coding-agent/src/core/model-registry.ts b/packages/coding-agent/src/core/model-registry.ts
index 61c67c6e..2cd2171a 100644
--- a/packages/coding-agent/src/core/model-registry.ts
+++ b/packages/coding-agent/src/core/model-registry.ts
@@ -25,6 +25,12 @@ import type { AuthStorage } from "./auth-storage.js";
 
 const Ajv = (AjvModule as any).default || AjvModule;
 
+// Schema for OpenRouter routing preferences
+const OpenRouterRoutingSchema = Type.Object({
+	only: Type.Optional(Type.Array(Type.String())),
+	order: Type.Optional(Type.Array(Type.String())),
+});
+
 // Schema for OpenAI compatibility settings
 const OpenAICompletionsCompatSchema = Type.Object({
 	supportsStore: Type.Optional(Type.Boolean()),
@@ -37,6 +43,7 @@ const OpenAICompletionsCompatSchema = Type.Object({
 	requiresThinkingAsText: Type.Optional(Type.Boolean()),
 	requiresMistralToolIds: Type.Optional(Type.Boolean()),
 	thinkingFormat: Type.Optional(Type.Union([Type.Literal("openai"), Type.Literal("zai")])),
+	openRouterRouting: Type.Optional(OpenRouterRoutingSchema),
 });
 
 const OpenAIResponsesCompatSchema = Type.Object({