fix(agent-runtime): chain XML tool calls properly to fix missing messages

The bug was that previousPromise was captured at callback creation time
instead of execution time, causing each XML tool call to start fresh
rather than waiting for the previous one. This fix reads
previousToolCallFinished at execution time inside onTagEnd.

Author: jahooma

packages/agent-runtime/src/tools/stream-parser.ts

@@ -136,7 +136,6 @@ export async function processStream(
   ) {
     const responseHandler = createResponseHandler(isXmlMode)
     const resultsArray = isXmlMode ? [] : toolResultsToAddAfterStream
-    const previousPromise = isXmlMode ? Promise.resolve() : previousToolCallFinished
 
     return {
       onTagStart: () => {},
@@ -156,6 +155,13 @@ export async function processStream(
             })
           : null
 
+        // Read previousToolCallFinished at execution time to ensure proper sequential chaining.
+        // For XML mode, if this is the first tool call (still pointing to streamDonePromise),
+        // start with a resolved promise so we don't wait for the stream to complete.
+        const previousPromise = isXmlMode && previousToolCallFinished === streamDonePromise
+          ? Promise.resolve()
+          : previousToolCallFinished
+
         // Determine which executor to use and with what parameters
         let toolPromise: Promise<void>
         if (isNativeTool || transformed) {