feat(plugin): default the reasoning level to medium

Settings that name no thinking level now run at medium instead of high.
Tests and artifacts that recorded the old default follow.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: sanchitrk

packages/codework/test/__artifacts__/acp.custom-models.json

@@ -1,7 +1,7 @@
 {
 	"project": {
 		"current": "gateway/claude-sonnet",
-		"thinking": "high",
+		"thinking": "medium",
 		"providers": [
 			"gateway",
 			"ollama",
@@ -23,7 +23,7 @@
 	},
 	"userOnly": {
 		"current": "openai/gpt-5.6-luna",
-		"thinking": "high",
+		"thinking": "medium",
 		"providers": [
 			"gateway",
 			"ollama",

packages/codework/test/__artifacts__/acp.models.json

@@ -14,6 +14,6 @@
 			"openai",
 			"openrouter"
 		],
-		"thinking": "high"
+		"thinking": "medium"
 	}
 }

packages/harness/test/__artifacts__/settings.thinking.json

@@ -1,6 +1,6 @@
 [
 	{
-		"requested": "high",
+		"requested": "medium",
 		"model": "openai/gpt-4o-mini",
 		"configuration": "off",
 		"request": {

packages/harness/test/settings.test.ts

@@ -180,7 +180,7 @@ describe("host settings loader", () => {
 					expect(second.model).toMatchObject({ thinkingLevel: "off", options: { timeoutMs: 200 } });
 					expect(first.model.thinkingLevel).toBe("low");
 					yield* Effect.promise(() => unlink(join(custom, "settings.jsonc")));
-					expect((yield* settings.load(root)).model.thinkingLevel).toBe("high");
+					expect((yield* settings.load(root)).model.thinkingLevel).toBe("medium");
 					// An edit that breaks a file reaches the next capture like any other edit. A broken
 					// layer fails the load rather than handing the session to the layers around it,
 					// which would run it on a configuration nobody wrote.

packages/plugin/src/settings.ts

@@ -236,7 +236,7 @@ export const defaults: Info = {
 	model: {
 		provider: "openai",
 		id: "gpt-5.6-luna",
-		thinkingLevel: "high",
+		thinkingLevel: "medium",
 		toolExecution: "sequential",
 		options: { timeoutMs: 3_600_000, idleTimeoutMs: 300_000, maxRetries: 0 },
 	},