patch out no finish reason from https://github.com/microsoft/Foundry-Local/issues/423

server/utils/AiProviders/foundry/index.js

@@ -1,11 +1,14 @@
 const { NativeEmbedder } = require("../../EmbeddingEngines/native");
+const { v4: uuidv4 } = require("uuid");
+const {
+  formatChatHistory,
+  writeResponseChunk,
+  clientAbortedHandler,
+} = require("../../helpers/chat/responses");
 const {
   LLMPerformanceMonitor,
 } = require("../../helpers/chat/LLMPerformanceMonitor");
-const {
-  handleDefaultStreamResponseV2,
-  formatChatHistory,
-} = require("../../helpers/chat/responses");
+
 const { OpenAI: OpenAIApi } = require("openai");
 
 class FoundryLLM {
@@ -262,8 +265,176 @@ class FoundryLLM {
     return measuredStreamRequest;
   }
 
+  /**
+   * The timeout for the Foundry stream in milliseconds.
+   * This is because Foundry does not self-close the stream and so we need to timeout the stream after a certain amount of time.
+   * @returns {number}
+   */
+  get timeout() {
+    return 500;
+  }
+
+  /**
+   * Handles the default stream response for a chat.
+   * @param {import("express").Response} response
+   * @param {import('../../helpers/chat/LLMPerformanceMonitor').MonitoredStream} stream
+   * @param {Object} responseProps
+   * @returns {Promise<string>}
+   */
   handleStream(response, stream, responseProps) {
-    return handleDefaultStreamResponseV2(response, stream, responseProps);
+    const timeoutThresholdMs = this.timeout;
+    const { uuid = uuidv4(), sources = [] } = responseProps;
+
+    return new Promise(async (resolve) => {
+      let fullText = "";
+      let reasoningText = "";
+      let lastChunkTime = null; // null when first token is still not received.
+
+      // Establish listener to early-abort a streaming response
+      // in case things go sideways or the user does not like the response.
+      // We preserve the generated text but continue as if chat was completed
+      // to preserve previously generated content.
+      const handleAbort = () => {
+        stream?.endMeasurement({
+          completion_tokens: LLMPerformanceMonitor.countTokens(fullText),
+        });
+        clientAbortedHandler(resolve, fullText);
+      };
+      response.on("close", handleAbort);
+
+      // NOTICE: As of Foundry 0.8.119 the stream will never return a finish_reason
+      // nor will it self-close or send a final chunk. So we need to maintain an interval timer that if we go >=timeoutThresholdMs with
+      // no new chunks then we kill the stream and assume it to be complete.
+      const timeoutCheck = setInterval(() => {
+        if (lastChunkTime === null) return;
+
+        const now = Number(new Date());
+        const diffMs = now - lastChunkTime;
+
+        if (diffMs >= timeoutThresholdMs) {
+          console.log(
+            `Foundry stream did not self-close and has been stale for >${timeoutThresholdMs}ms. Closing response stream.`
+          );
+          writeResponseChunk(response, {
+            uuid,
+            sources,
+            type: "textResponseChunk",
+            textResponse: "",
+            close: true,
+            error: false,
+          });
+          clearInterval(timeoutCheck);
+          response.removeListener("close", handleAbort);
+          stream?.endMeasurement({
+            completion_tokens: LLMPerformanceMonitor.countTokens(fullText),
+          });
+          resolve(fullText);
+        }
+      }, 500);
+
+      try {
+        for await (const chunk of stream) {
+          // console.log(JSON.stringify(chunk, null, 2));
+          const message = chunk?.choices?.[0];
+          const token = message?.delta?.content;
+          const reasoningToken = message?.delta?.reasoning;
+          lastChunkTime = Number(new Date());
+
+          // Reasoning models will always return the reasoning text before the token text.
+          // can be null or ''
+          if (reasoningToken) {
+            // If the reasoning text is empty (''), we need to initialize it
+            // and send the first chunk of reasoning text.
+            if (reasoningText.length === 0) {
+              writeResponseChunk(response, {
+                uuid,
+                sources: [],
+                type: "textResponseChunk",
+                textResponse: `<think>${reasoningToken}`,
+                close: false,
+                error: false,
+              });
+              reasoningText += `<think>${reasoningToken}`;
+              continue;
+            } else {
+              // If the reasoning text is not empty, we need to append the reasoning text
+              // to the existing reasoning text.
+              writeResponseChunk(response, {
+                uuid,
+                sources: [],
+                type: "textResponseChunk",
+                textResponse: reasoningToken,
+                close: false,
+                error: false,
+              });
+              reasoningText += reasoningToken;
+            }
+          }
+
+          // If the reasoning text is not empty, but the reasoning token is empty
+          // and the token text is not empty we need to close the reasoning text and begin sending the token text.
+          if (!!reasoningText && !reasoningToken && token) {
+            writeResponseChunk(response, {
+              uuid,
+              sources: [],
+              type: "textResponseChunk",
+              textResponse: `</think>`,
+              close: false,
+              error: false,
+            });
+            fullText += `${reasoningText}</think>`;
+            reasoningText = "";
+          }
+
+          if (token) {
+            fullText += token;
+            writeResponseChunk(response, {
+              uuid,
+              sources: [],
+              type: "textResponseChunk",
+              textResponse: token,
+              close: false,
+              error: false,
+            });
+          }
+
+          // finish_reason can be "stop", "length", etc. when complete
+          // Must check for truthy value since undefined !== null is true
+          if (message?.finish_reason) {
+            writeResponseChunk(response, {
+              uuid,
+              sources,
+              type: "textResponseChunk",
+              textResponse: "",
+              close: true,
+              error: false,
+            });
+            response.removeListener("close", handleAbort);
+            clearInterval(timeoutCheck);
+            stream?.endMeasurement({
+              completion_tokens: LLMPerformanceMonitor.countTokens(fullText),
+            });
+            resolve(fullText);
+            return; // Exit the loop after resolving
+          }
+        }
+      } catch (e) {
+        writeResponseChunk(response, {
+          uuid,
+          sources,
+          type: "abort",
+          textResponse: null,
+          close: true,
+          error: e.message,
+        });
+        response.removeListener("close", handleAbort);
+        clearInterval(timeoutCheck);
+        stream?.endMeasurement({
+          completion_tokens: LLMPerformanceMonitor.countTokens(fullText),
+        });
+        resolve(fullText);
+      }
+    });
   }
 
   // Simple wrapper for dynamic embedder & normalize interface for all LLM implementations