diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 138b4e27b..5394de918 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -18,6 +18,7 @@
 
 ### Fixed
 
+- Fixed `models.json` typings omitting the documented OpenAI-compatible `compat.supportsFinishReason` provider and model override ([#8460](https://github.com/earendil-works/pi/issues/8460)).
 - Fixed writes to `auth.json` and `models-store.json` overriding administrator-managed file permissions and ACLs ([#7779](https://github.com/earendil-works/pi/issues/7779)).
 - Fixed UTF-8 BOM markers preventing frontmatter and user configuration files from loading ([#8337](https://github.com/earendil-works/pi/issues/8337)).
 - Fixed invalid settings files being easy to miss during interactive startup by rendering warnings with the file path inside the TUI ([#7829](https://github.com/earendil-works/pi/issues/7829)).
diff --git a/packages/coding-agent/src/core/model-config.ts b/packages/coding-agent/src/core/model-config.ts
index f24a27937..6036d5af9 100644
--- a/packages/coding-agent/src/core/model-config.ts
+++ b/packages/coding-agent/src/core/model-config.ts
@@ -75,6 +75,7 @@ const OpenAICompletionsCompatSchema = Type.Object({
 	supportsDeveloperRole: Type.Optional(Type.Boolean()),
 	supportsReasoningEffort: Type.Optional(Type.Boolean()),
 	supportsUsageInStreaming: Type.Optional(Type.Boolean()),
+	supportsFinishReason: Type.Optional(Type.Boolean()),
 	maxTokensField: Type.Optional(Type.Union([Type.Literal("max_completion_tokens"), Type.Literal("max_tokens")])),
 	requiresToolResultName: Type.Optional(Type.Boolean()),
 	requiresAssistantAfterToolResult: Type.Optional(Type.Boolean()),
diff --git a/packages/coding-agent/test/model-registry.test.ts b/packages/coding-agent/test/model-registry.test.ts
index dae695c33..18bf921b3 100644
--- a/packages/coding-agent/test/model-registry.test.ts
+++ b/packages/coding-agent/test/model-registry.test.ts
@@ -11,6 +11,7 @@ import type {
 import { getApiProvider, getSupportedThinkingLevels } from "@earendil-works/pi-ai/compat";
 import { afterEach, beforeEach, describe, expect, test, vi } from "vitest";
 import { AuthStorage } from "../src/core/auth-storage.ts";
+import type { ModelsJsonProvider } from "../src/core/model-config.ts";
 import { clearApiKeyCache, type ModelRegistry, type ProviderConfigInput } from "../src/core/model-registry.ts";
 
 import { createModelRegistry } from "./model-runtime-test-utils.ts";
@@ -767,6 +768,26 @@ describe("ModelRegistry", () => {
 			expect(compat?.openRouterRouting).toEqual({ only: ["amazon-bedrock"] });
 		});
 
+		test("supportsFinishReason can be configured at provider and model levels", async () => {
+			const provider: ModelsJsonProvider = {
+				compat: { supportsFinishReason: true },
+				modelOverrides: {
+					"anthropic/claude-sonnet-4": {
+						compat: { supportsFinishReason: false },
+					},
+				},
+			};
+			writeRawModelsJson({ openrouter: provider });
+
+			const registry = await createModelRegistry(authStorage, modelsJsonPath);
+			const models = getModelsForProvider(registry, "openrouter");
+			const sonnet = models.find((model) => model.id === "anthropic/claude-sonnet-4");
+			const opus = models.find((model) => model.id === "anthropic/claude-opus-4");
+
+			expect((sonnet?.compat as OpenAICompletionsCompat | undefined)?.supportsFinishReason).toBe(false);
+			expect((opus?.compat as OpenAICompletionsCompat | undefined)?.supportsFinishReason).toBe(true);
+		});
+
 		test("model override deep merges compat settings", async () => {
 			writeRawModelsJson({
 				openrouter: {