fix(ai): mark inception/mercury-2 thinkingLevelMap.off as null

Mercury 2 in instant mode (reasoning_effort: "none") disables tool calling.
The openai-completions provider hardcodes {reasoning:{effort:"none"}} when no
explicit reasoning level is passed and thinkingLevelMap.off isn't null
(openai-completions.ts:575), so every caller that doesn't opt in to a level
silently breaks Mercury 2's agentic use cases.

Setting thinkingLevelMap.off = null on the Mercury 2 catalog entry causes the
provider to omit the reasoning param entirely, letting Mercury 2's own default
take over. Low/medium/high pass through verbatim; OpenRouter normalizes them
to Mercury's vocabulary.

Prefix-matched on "inception/mercury-2" so future Mercury 2 variants on
OpenRouter inherit the fix.

packages/ai/CHANGELOG.md

@@ -10,6 +10,7 @@
 
 - Fixed GitHub Copilot Claude test coverage to use the current Claude Sonnet 4.6 model ID.
 - Fixed OpenAI Responses requests for models that support disabling reasoning to send `reasoning.effort: "none"` when thinking is off.
+- Fixed Inception Mercury 2 tool calling on OpenRouter by marking `off` as unsupported in `thinkingLevelMap`, so the openai-completions provider omits the reasoning param instead of defaulting to `{reasoning:{effort:"none"}}` (which puts Mercury 2 in instant mode, disabling tool calls).
 
 ## [0.74.0] - 2026-05-07
 

packages/ai/scripts/generate-models.ts

@@ -240,6 +240,13 @@ function applyThinkingLevelMetadata(model: Model<any>): void {
 	if (model.provider === "openai-codex" && model.id === "gpt-5.1-codex-mini") {
 		mergeThinkingLevelMap(model, { minimal: "medium", low: "medium", medium: "medium", high: "high" });
 	}
+	if (model.provider === "openrouter" && model.id.startsWith("inception/mercury-2")) {
+		// Mercury 2 in instant mode (reasoning_effort: "none") disables tool calling.
+		// Mark "off" unsupported so the openai-completions provider omits the reasoning param
+		// instead of defaulting to {reasoning:{effort:"none"}} (see openai-completions.ts:575).
+		// Pi's low/medium/high pass through verbatim; OpenRouter normalizes to Mercury's vocabulary.
+		mergeThinkingLevelMap(model, { off: null });
+	}
 }
 
 function getAnthropicMessagesCompat(provider: string, modelId: string): AnthropicMessagesCompat | undefined {

packages/ai/src/models.generated.ts

@@ -9731,6 +9731,7 @@ export const MODELS = {
 			provider: "openrouter",
 			baseUrl: "https://openrouter.ai/api/v1",
 			reasoning: true,
+			thinkingLevelMap: {"off":null},
 			input: ["text"],
 			cost: {
 				input: 0.25,