diff --git a/packages/ai/README.md b/packages/ai/README.md
index 7af343eab..73f831905 100644
--- a/packages/ai/README.md
+++ b/packages/ai/README.md
@@ -891,7 +891,7 @@ console.log(model.output); // ['image'] or ['image', 'text']
 
 ## Classification
 
-Classifier models consume structured JSON state, and optionally images, and answer one or more typed questions. They do not use chat or image-generation APIs. TypeSafe's Jev model, Cloudflare's Clef models, and OpenAI's GPT-6 Luna are available from these built-in providers:
+Classifier models consume structured JSON state, and optionally images, and answer one or more typed questions. They do not use chat or image-generation APIs. TypeSafe's Jev model, Cloudflare's Clef models, OpenAI's GPT-6 Luna, and Microsoft-Decision-1 are available from these built-in providers:
 
 | Provider | Model IDs | Auth |
 | --- | --- | --- |
@@ -901,6 +901,7 @@ Classifier models consume structured JSON state, and optionally images, and answ
 | `vercel-ai-gateway` | `typesafe-ai/jev` | `AI_GATEWAY_API_KEY` |
 | `opencode` | `jev-1.13`, `jev-1.13-free` | `OPENCODE_API_KEY` |
 | `openai` | `gpt-6-luna` | `OPENAI_API_KEY` |
+| `github-copilot` | `microsoft-decision-1` | `COPILOT_GITHUB_TOKEN` or GitHub Copilot OAuth |
 
 ```typescript
 import { builtinModels } from '@earendil-works/pi-ai/providers/all';
diff --git a/packages/ai/catalog/providers/github-copilot.ts b/packages/ai/catalog/providers/github-copilot.ts
index 2bea3586b..b91a03213 100644
--- a/packages/ai/catalog/providers/github-copilot.ts
+++ b/packages/ai/catalog/providers/github-copilot.ts
@@ -1,4 +1,4 @@
-import type { Api, Model, ThinkingLevelMap } from "../../src/types.ts";
+import type { Api, ClassifierModel, Model, ThinkingLevelMap } from "../../src/types.ts";
 import { addMissing, type ChatModel, defineProvider, mergeCompat, mergeThinking, modelsDevModels } from "../define.ts";
 import { claude55ThinkingLevels, supportsClaudeMidConvoSystemMessages } from "../families/anthropic.ts";
 import {
@@ -67,6 +67,22 @@ const GPT_6_LUNA: Model<"openai-responses"> = {
 	headers: { ...STATIC_HEADERS },
 };
 
+// The authenticated Copilot catalog lists this decision model on /v1/systemone (checked 2026-11-02) without
+// a context window or price, and GitHub's Copilot pricing page does not list it. These are Azure's values,
+// which OpenRouter and Vercel AI Gateway also list.
+const MICROSOFT_DECISION_1: ClassifierModel<"typesafe-system-one"> = {
+	type: "classifier",
+	id: "microsoft-decision-1",
+	name: "Microsoft-Decision-1",
+	api: "typesafe-system-one",
+	provider: "github-copilot",
+	baseUrl: BASE_URL,
+	input: ["text"],
+	cost: { input: 0.042, output: 0, cacheRead: 0, cacheWrite: 0 },
+	contextWindow: 32768,
+	headers: { ...STATIC_HEADERS },
+};
+
 export default defineProvider({
 	id: "github-copilot",
 	models: (ctx) =>
@@ -94,6 +110,7 @@ export default defineProvider({
 			}),
 			[GPT_6_LUNA],
 		).map((model) => (EXTENDED_CONTEXT_MODEL_IDS.has(model.id) ? { ...model, contextWindow: 1000000 } : model)),
+	classifiers: () => [MICROSOFT_DECISION_1],
 	compat: { "openai-completions": { supportsStrictMode: true } },
 	finalize: (model) => {
 		if (model.id.startsWith("gpt-5")) mergeThinking(model, { minimal: "low" });
diff --git a/packages/ai/src/providers/github-copilot.ts b/packages/ai/src/providers/github-copilot.ts
index eab784d88..282bc1da1 100644
--- a/packages/ai/src/providers/github-copilot.ts
+++ b/packages/ai/src/providers/github-copilot.ts
@@ -1,13 +1,28 @@
 import { anthropicMessagesApi } from "../api/anthropic-messages.lazy.ts";
 import { openAICompletionsApi } from "../api/openai-completions.lazy.ts";
 import { openAIResponsesApi } from "../api/openai-responses.lazy.ts";
+import { typesafeSystemOneApi } from "../api/typesafe-system-one.lazy.ts";
 import { envApiKeyAuth, lazyOAuth } from "../auth/helpers.ts";
 import { loadGitHubCopilotOAuth } from "../auth/oauth/load.ts";
 import { createProvider, type Provider } from "../models.ts";
-import { GITHUB_COPILOT_MODELS } from "./github-copilot.models.ts";
+import type { ProviderClassifier } from "../types.ts";
+import { GITHUB_COPILOT_CLASSIFIER_MODELS, GITHUB_COPILOT_MODELS } from "./github-copilot.models.ts";
 
-export function githubCopilotProvider(): Provider<"anthropic-messages" | "openai-completions" | "openai-responses"> {
-	return createProvider({
+type GitHubCopilotApi = "anthropic-messages" | "openai-completions" | "openai-responses";
+
+/**
+ * Copilot serves System One at `/v1/systemone`, while its chat APIs have no version prefix.
+ * The login replaces the catalog base URL with the account's endpoint, so the prefix is added per request.
+ */
+function copilotSystemOne(classifier: ProviderClassifier): ProviderClassifier {
+	return {
+		classify: (model, context, options) =>
+			classifier.classify({ ...model, baseUrl: `${model.baseUrl.replace(/\/+$/u, "")}/v1` }, context, options),
+	};
+}
+
+export function githubCopilotProvider(): Provider<GitHubCopilotApi> {
+	return createProvider<GitHubCopilotApi>({
 		id: "github-copilot",
 		name: "GitHub Copilot",
 		baseUrl: "https://api.individual.githubcopilot.com",
@@ -15,7 +30,7 @@ export function githubCopilotProvider(): Provider<"anthropic-messages" | "openai
 			apiKey: envApiKeyAuth("GitHub Copilot token", ["COPILOT_GITHUB_TOKEN"]),
 			oauth: lazyOAuth({ name: "GitHub Copilot", isSubscription: true, load: loadGitHubCopilotOAuth }),
 		},
-		models: Object.values(GITHUB_COPILOT_MODELS),
+		models: [...Object.values(GITHUB_COPILOT_MODELS), ...Object.values(GITHUB_COPILOT_CLASSIFIER_MODELS)],
 		filterModels: (models, credential) => {
 			if (credential?.type !== "oauth") return models;
 			const availableModelIds = credential.availableModelIds;
@@ -30,5 +45,6 @@ export function githubCopilotProvider(): Provider<"anthropic-messages" | "openai
 			"openai-completions": openAICompletionsApi(),
 			"openai-responses": openAIResponsesApi(),
 		},
+		classifiers: { "typesafe-system-one": copilotSystemOne(typesafeSystemOneApi()) },
 	});
 }
diff --git a/packages/ai/test/classifier-models.test.ts b/packages/ai/test/classifier-models.test.ts
index cae1df4a5..9f26b199c 100644
--- a/packages/ai/test/classifier-models.test.ts
+++ b/packages/ai/test/classifier-models.test.ts
@@ -245,6 +245,62 @@ describe("Models with classifier models", () => {
 		expect((await withOAuth.getAvailable("openai")).some((model) => model.id === "gpt-6-luna")).toBe(true);
 	});
 
+	it("routes GitHub Copilot Microsoft-Decision-1 to the account's /v1/systemone endpoint", async () => {
+		const credentials = new InMemoryCredentialStore();
+		await credentials.modify("github-copilot", async () => ({
+			type: "oauth",
+			access: "tid=test;exp=9999999999;proxy-ep=proxy.enterprise.githubcopilot.com;",
+			refresh: "refresh",
+			expires: Date.now() + 3_600_000,
+			// The login records only picker models; classifiers stay listed.
+			availableModelIds: ["gpt-6-luna"],
+		}));
+		const models = builtinModels({ credentials });
+		const decision = models.getModelOfType("classifier", "github-copilot", "microsoft-decision-1");
+		if (!decision) throw new Error("missing GitHub Copilot decision model");
+		expect(decision).toMatchObject({
+			api: "typesafe-system-one",
+			baseUrl: "https://api.individual.githubcopilot.com",
+			input: ["text"],
+			contextWindow: 32768,
+		});
+		expect(models.getModel("github-copilot", "microsoft-decision-1")).toBeUndefined();
+		expect(await models.getAvailableOfType("classifier", "github-copilot")).toEqual([decision]);
+
+		const requests: Array<{ url: string; headers: Headers }> = [];
+		const result = await models.classify(decision, context, {
+			fetch: async (input, init) => {
+				requests.push({ url: String(input), headers: new Headers(init?.headers) });
+				return Response.json({ answers: { approved: { type: "noul", noul: 0.8 } } });
+			},
+		});
+
+		expect(requests.map((request) => request.url)).toEqual(["https://api.enterprise.githubcopilot.com/v1/systemone"]);
+		expect(requests[0].headers.get("authorization")).toBe(
+			"Bearer tid=test;exp=9999999999;proxy-ep=proxy.enterprise.githubcopilot.com;",
+		);
+		// Copilot rejects requests without an editor version.
+		expect(requests[0].headers.get("editor-version")).toBeTruthy();
+		expect(requests[0].headers.get("copilot-integration-id")).toBe("vscode-chat");
+		expect(result.stopReason).toBe("stop");
+		expect(result.answers.approved).toEqual({ type: "bool", probability: 0.8 });
+	});
+
+	it("adds the System One version prefix to the GitHub Copilot catalog base URL", async () => {
+		const models = builtinModels();
+		const decision = models.getModelOfType("classifier", "github-copilot", "microsoft-decision-1");
+		if (!decision) throw new Error("missing GitHub Copilot decision model");
+		const urls: string[] = [];
+		await models.classify(decision, context, {
+			apiKey: "secret",
+			fetch: async (input) => {
+				urls.push(String(input));
+				return Response.json({ answers: { approved: { type: "noul", noul: 0.8 } } });
+			},
+		});
+		expect(urls).toEqual(["https://api.individual.githubcopilot.com/v1/systemone"]);
+	});
+
 	it("routes OpenRouter classifier models through the System One API", () => {
 		const models = builtinModels();
 		for (const model of getBuiltinClassifierModels("openrouter")) {
diff --git a/packages/coding-agent/docs/models.md b/packages/coding-agent/docs/models.md
index e076ac139..803458a8b 100644
--- a/packages/coding-agent/docs/models.md
+++ b/packages/coding-agent/docs/models.md
@@ -141,7 +141,7 @@ Compatibility settings should describe verified differences in the endpoint's re
 
 ## Use classifier models
 
-Classifier models do not chat. They answer typed questions about JSON state: pick one of several choices, answer yes or no, or give a score, each with probabilities. Pi includes TypeSafe's Jev model from these providers, Cloudflare's Clef, Clef Flash, and Clef Omni models from Workers AI and OpenRouter, and OpenAI's GPT-6 Luna through the [Decisions API](https://developers.openai.com/api/docs/guides/decisions):
+Classifier models do not chat. They answer typed questions about JSON state: pick one of several choices, answer yes or no, or give a score, each with probabilities. Pi includes TypeSafe's Jev model from these providers, Cloudflare's Clef, Clef Flash, and Clef Omni models from Workers AI and OpenRouter, OpenAI's GPT-6 Luna through the [Decisions API](https://developers.openai.com/api/docs/guides/decisions), and Microsoft-Decision-1 through GitHub Copilot:
 
 | Provider | Model IDs | Authentication |
 |---|---|---|
@@ -151,6 +151,7 @@ Classifier models do not chat. They answer typed questions about JSON state: pic
 | `vercel-ai-gateway` | `typesafe-ai/jev` | `AI_GATEWAY_API_KEY` |
 | `opencode` | `jev-1.13`, `jev-1.13-free` | `OPENCODE_API_KEY` |
 | `openai` | `gpt-6-luna` | `OPENAI_API_KEY` |
+| `github-copilot` | `microsoft-decision-1` | `COPILOT_GITHUB_TOKEN` or `/login` |
 
 Chat models on a [llama.cpp router](llama-cpp.md#classification) are also listed as classifier models.