fix(chat): strip runtime turn context from projection before model input

packages/junior/src/chat/runtime/reply-executor.ts

@@ -214,7 +214,7 @@ async function loadPiMessagesForTurn(args: {
   if (projection.length > 0) {
     return {
       canCompact: true,
-      piMessages: projection,
+      piMessages: stripRuntimeTurnContext(projection),
     };
   }
 

packages/junior/tests/unit/misc/respond-helpers-runtime-context.test.ts

@@ -1,6 +1,10 @@
 import { describe, expect, it } from "vitest";
 import type { PiMessage } from "@/chat/pi/messages";
-import { prependMissingRuntimeTurnContext } from "@/chat/respond-helpers";
+import {
+  hasRuntimeTurnContext,
+  prependMissingRuntimeTurnContext,
+  stripRuntimeTurnContext,
+} from "@/chat/respond-helpers";
 
 describe("prependMissingRuntimeTurnContext", () => {
   it("leaves recorded bootstrap prompts unchanged", () => {
@@ -47,6 +51,62 @@ describe("prependMissingRuntimeTurnContext", () => {
     expect(JSON.stringify(updated[0])).not.toContain("slack:C123:updated");
   });
 
+  it("injects new requester context after stripping stale projected context", () => {
+    // Simulates a thread started by user A, where the runtime turn context
+    // from the first turn was persisted into the session log projection.
+    // When user B sends a follow-up message, `loadPiMessagesForTurn` must
+    // strip the stale context before returning, so `hasRuntimeTurnContext`
+    // returns false and a fresh context block carrying user B's identity
+    // is injected instead.
+    const projectionWithStaleContext: PiMessage[] = [
+      {
+        role: "user",
+        content: [
+          {
+            type: "text",
+            text: [
+              "<runtime-turn-context>",
+              "<requester>",
+              "- full_name: User Alpha",
+              "- user_name: user.alpha",
+              "- user_id: U_ALPHA",
+              "</requester>",
+              "</runtime-turn-context>",
+            ].join("\n"),
+          },
+          { type: "text", text: "original question" },
+        ],
+        timestamp: 1,
+      },
+      {
+        role: "assistant",
+        content: [{ type: "text", text: "original answer" }],
+        timestamp: 2,
+      },
+    ] as PiMessage[];
+
+    // Before stripping: stale context is present, so no new context would be injected
+    expect(hasRuntimeTurnContext(projectionWithStaleContext)).toBe(true);
+
+    // After stripping (what loadPiMessagesForTurn now does): fresh injection is possible
+    const stripped = stripRuntimeTurnContext(projectionWithStaleContext);
+    expect(hasRuntimeTurnContext(stripped)).toBe(false);
+
+    const userBContext = [
+      "<runtime-turn-context>",
+      "<requester>",
+      "- user_name: user.beta",
+      "- user_id: U_BETA",
+      "</requester>",
+      "</runtime-turn-context>",
+    ].join("\n");
+    const updated = prependMissingRuntimeTurnContext(stripped, userBContext);
+
+    expect(JSON.stringify(updated)).toContain("user.beta");
+    expect(JSON.stringify(updated)).not.toContain("user.alpha");
+    expect(JSON.stringify(updated)).not.toContain("User Alpha");
+  });
+
   it("adds bootstrap context to a pre-prompt user boundary", () => {
     const messages: PiMessage[] = [
       {