From f42b54873f2b083af57ad356273968d759b02720 Mon Sep 17 00:00:00 2001
From: "vs-code-engineering[bot]"
 <122617954+vs-code-engineering[bot]@users.noreply.github.com>
Date: Fri, 19 Jun 2026 16:17:50 +0000
Subject: [PATCH] fix: tolerate invalid tool-call JSON in language model
 wrapper (fixes #322123)

The model can stream malformed JSON for tool-call arguments. The language model wrapper threw a bare Error from a fire-and-forget finished callback, producing an unhandled rejection in error telemetry without cleanly aborting the response. Align with the other tool-call consumers (langModelServer, messagesApi) by logging the diagnostic and falling back to empty parameters so the tool call is still surfaced to the consuming extension.
---
 .../conversation/vscode-node/languageModelAccess.ts | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/extensions/copilot/src/extension/conversation/vscode-node/languageModelAccess.ts b/extensions/copilot/src/extension/conversation/vscode-node/languageModelAccess.ts
index 4017dc52bc67b0..ea6cf633086222 100644
--- a/extensions/copilot/src/extension/conversation/vscode-node/languageModelAccess.ts
+++ b/extensions/copilot/src/extension/conversation/vscode-node/languageModelAccess.ts
@@ -834,14 +834,19 @@ export class CopilotLanguageModelWrapper extends Disposable {
 			}
 			if (delta.copilotToolCalls) {
 				for (const call of delta.copilotToolCalls) {
+					// Anthropic models send "" (empty string) for tools with no parameters.
+					let parameters: object;
 					try {
-						// Anthropic models send "" (empty string) for tools with no parameters.
-						const parameters = JSON.parse(call.arguments || '{}');
-						progress.report(new vscode.LanguageModelToolCallPart(call.id, call.name, parameters));
+						parameters = JSON.parse(call.arguments || '{}');
 					} catch (err) {
+						// The model can stream malformed JSON for tool arguments. Log it for
+						// diagnostics and fall back to empty parameters so the tool call is still
+						// surfaced to the extension (matching other tool-call consumers) instead of
+						// leaking an unhandled rejection out of this fire-and-forget callback.
 						this._logService.error(err, `Got invalid JSON for tool call: ${call.arguments}`);
-						throw new Error('Invalid JSON for tool call');
+						parameters = {};
 					}
+					progress.report(new vscode.LanguageModelToolCallPart(call.id, call.name, parameters));
 				}
 			}