fix(kiro): intercept chat via x-amz-target and prepend initial-response frame

Kiro IDE 1.0.228+ moved GenerateAssistantResponse from path
/generateAssistantResponse to POST / + x-amz-target header, so chat turns
bypassed MITM. The SmithyMessageDecoderStream also now requires an
initial-response frame at stream start, and agent/vibe mode sends
modelId "auto" which had no mappable slot.

- Add isChatRequest() header-based match for kiro in mitm/config.js
- Add buildInitialResponseFrame/withInitialFrame to emit the mandatory
  initial-response once per stream (kiro.js)
- Add "auto" model slot and update mitmDomain to runtime.us-east-1.kiro.dev

src/mitm/config.js

@@ -26,10 +26,28 @@ const TARGET_HOSTS = [
 const URL_PATTERNS = {
   antigravity: [":generateContent", ":streamGenerateContent"],
   copilot: ["/chat/completions", "/v1/messages", "/responses"],
+  // Legacy path form. Kiro IDE 1.0.228+ posts to `/` with x-amz-target instead —
+  // see isChatRequest() for the header-based match.
   kiro: ["/generateAssistantResponse"],
   cursor: ["/BidiAppend", "/RunSSE", "/RunPoll", "/Run"],
 };
 
+/**
+ * Whether this request is a chat turn we should intercept (vs passthrough).
+ * Kiro Runtime moved GenerateAssistantResponse from path `/generateAssistantResponse`
+ * to `POST /` + `x-amz-target: KiroRuntimeService.GenerateAssistantResponse`
+ * (verified via live mitmproxy capture of Kiro IDE 1.0.228).
+ */
+function isChatRequest(tool, req) {
+  const patterns = URL_PATTERNS[tool] || [];
+  if (patterns.some((p) => (req.url || "").includes(p))) return true;
+  if (tool === "kiro") {
+    const target = String(req.headers?.["x-amz-target"] || "");
+    return target.includes("GenerateAssistantResponse");
+  }
+  return false;
+}
+
 // Synonym map: rawModel from request → canonical alias key in mitmAlias DB
 const MODEL_SYNONYMS = {
   antigravity: {
@@ -127,4 +145,4 @@ function extractModel(url, body) {
   }
 }
 
-module.exports = { IS_DEV, LSOF_BIN, TARGET_HOSTS, URL_PATTERNS, MODEL_SYNONYMS, MODEL_PATTERNS, MODEL_NO_MAP, LOG_BLACKLIST_URL_PARTS, getToolForHost, extractModel };
+module.exports = { IS_DEV, LSOF_BIN, TARGET_HOSTS, URL_PATTERNS, MODEL_SYNONYMS, MODEL_PATTERNS, MODEL_NO_MAP, LOG_BLACKLIST_URL_PARTS, getToolForHost, isChatRequest, extractModel };

src/mitm/handlers/kiro.js

@@ -43,7 +43,8 @@ function initKiroState(modelId) {
     finishSent: false,             // Whether termination has been emitted
     usage: null,                   // Accumulated usage from usage-only chunks
     inThink: false,                // Whether inside a <thinking> block
-    thinkBuf: ""                   // Buffer for partial thinking content
+    thinkBuf: "",                  // Buffer for partial thinking content
+    initialSent: false,            // Whether initial-response frame was emitted
   };
 }
 
@@ -130,9 +131,9 @@ function encodeHeader(name, value) {
  * The SmithyMessageDecoderStream layer requires three system headers on every frame:
  *   :message-type  = "event"             (or "exception" / "error")
  *   :event-type    = e.g. "assistantResponseEvent"
- *   :content-type  = "application/json"
+ *   :content-type  = "application/json"  (initial-response uses x-amz-json-1.0)
  */
-function buildEventStreamFrame(eventType, payload) {
+function buildEventStreamFrame(eventType, payload, contentType = "application/json") {
   const payloadBuf = Buffer.from(
     typeof payload === "string" ? payload : JSON.stringify(payload),
     "utf8"
@@ -142,7 +143,7 @@ function buildEventStreamFrame(eventType, payload) {
   const headersBuf = Buffer.concat([
     encodeHeader(":message-type", "event"),
     encodeHeader(":event-type", eventType),
-    encodeHeader(":content-type", "application/json"),
+    encodeHeader(":content-type", contentType),
   ]);
   const headersLen = headersBuf.length;
 
@@ -159,6 +160,24 @@ function buildEventStreamFrame(eventType, payload) {
   return frame;
 }
 
+/** Real Kiro Runtime always starts the stream with this frame (capture of IDE 1.0.228). */
+function buildInitialResponseFrame(conversationId = "") {
+  return buildEventStreamFrame(
+    "initial-response",
+    { conversationId: conversationId || "" },
+    "application/x-amz-json-1.0"
+  );
+}
+
+/** Prepend initial-response once per stream so Smithy decoder is happy. */
+function withInitialFrame(state, frames) {
+  const list = frames == null ? [] : Array.isArray(frames) ? frames : [frames];
+  if (state.initialSent) return list.length === 0 ? null : list.length === 1 ? list[0] : list;
+  state.initialSent = true;
+  const out = [buildInitialResponseFrame(""), ...list];
+  return out.length === 1 ? out[0] : out;
+}
+
 // ─── CodeWhisperer → OpenAI conversion ───────────────────────────────────────
 
 /**
@@ -321,12 +340,12 @@ function convertOpenAIToKiro(chunk, state) {
       state.inThink = false;
       const thinking = state.thinkBuf;
       state.thinkBuf = "";
-      return buildEventStreamFrame("reasoningContentEvent", {
+      return withInitialFrame(state, buildEventStreamFrame("reasoningContentEvent", {
         content: thinking,
         modelId: state.modelId || "kiro-unknown"
-      });
+      }));
     }
-    return buildEventStreamFrame("messageStopEvent", {});
+    return withInitialFrame(state, buildEventStreamFrame("messageStopEvent", {}));
   }
 
   const frames = [];
@@ -408,8 +427,12 @@ function convertOpenAIToKiro(chunk, state) {
     }
   }
 
-  if (frames.length === 0) return null;
-  return frames.length === 1 ? frames[0] : frames;
+  if (frames.length === 0) {
+    // اولین چانک ممکنه فقط role/empty باشه — initial رو همون‌جا بفرست
+    if (!state.initialSent) return withInitialFrame(state, null);
+    return null;
+  }
+  return withInitialFrame(state, frames.length === 1 ? frames[0] : frames);
 }
 
 /**

src/mitm/server.js

@@ -7,7 +7,7 @@ const dns = require("dns");
 const { promisify } = require("util");
 const { execSync } = require("child_process");
 const { log, err, dumpRequest, createResponseDumper, clearDumpDir } = require("./logger");
-const { IS_DEV, LSOF_BIN, TARGET_HOSTS, URL_PATTERNS, MODEL_SYNONYMS, MODEL_PATTERNS, MODEL_NO_MAP, getToolForHost, extractModel } = require("./config");
+const { IS_DEV, LSOF_BIN, TARGET_HOSTS, URL_PATTERNS, MODEL_SYNONYMS, MODEL_PATTERNS, MODEL_NO_MAP, getToolForHost, isChatRequest, extractModel } = require("./config");
 const { DATA_DIR, MITM_DIR } = require("./paths");
 const { generateCert, getCertForDomain } = require("./cert/generate");
 const { getMitmAlias } = require("./dbReader");
@@ -311,9 +311,8 @@ const server = https.createServer(sslOptions, async (req, res) => {
     const tool = getToolForHost(req.headers.host);
     if (!tool) return passthrough(req, res, bodyBuffer);
 
-    const patterns = URL_PATTERNS[tool] || [];
-    const isChat = patterns.some(p => req.url.includes(p));
-    if (!isChat) return passthrough(req, res, bodyBuffer);
+    // Kiro IDE posts chat to `/` with x-amz-target (not path /generateAssistantResponse)
+    if (!isChatRequest(tool, req)) return passthrough(req, res, bodyBuffer);
 
     // Cursor uses binary proto — model extraction not possible at this layer.
     // Delegate directly to handler which decodes proto internally.

src/shared/constants/cliTools.js

@@ -57,8 +57,13 @@ export const MITM_TOOLS = {
     color: "#FF6B00",
     description: "Kiro IDE with MITM",
     configType: "mitm",
-    mitmDomain: "q.us-east-1.amazonaws.com",
+    mitmDomain: "runtime.us-east-1.kiro.dev",
     defaultModels: [
+      // Kiro's agent/"vibe" mode sends modelId "auto" for the main turn and "simple-task"
+      // for background sub-tasks (verified via MITM request dump of generateAssistantResponse).
+      // Both need a mappable slot — otherwise getMappedModel returns null and the chat call
+      // is passed through to AWS instead of being routed to the chosen provider.
+      { id: "auto", name: "Auto (Kiro Agent)", alias: "auto" },
       { id: "claude-sonnet-5", name: "Claude Sonnet 5", alias: "claude-sonnet-5" },
       { id: "claude-sonnet-4.5", name: "Claude Sonnet 4.5", alias: "claude-sonnet-4.5" },
       { id: "claude-sonnet-4", name: "Claude Sonnet 4", alias: "claude-sonnet-4" },

tests/unit/kiro-model-slots.test.js

@@ -14,6 +14,13 @@ describe("Kiro MITM model slots", () => {
     expect(Array.isArray(kiro.defaultModels)).toBe(true);
   });
 
+  it("offers a mappable slot for the agent default model id 'auto'", () => {
+    // اسلات auto برای vibe mode لازمه — وگرنه درخواست میره AWS
+    const auto = kiro.defaultModels.find((m) => m.id === "auto");
+    expect(auto).toBeTruthy();
+    expect(auto.alias).toBe("auto");
+  });
+
   it("offers a mappable slot for Claude Sonnet 5", () => {
     const sonnet5 = kiro.defaultModels.find((m) => m.id === "claude-sonnet-5");
     expect(sonnet5).toBeTruthy();