fix(chat): tell chat agents a task they cannot find may be private

A chat agent asked about a same-company private task it cannot read got
empty searches and not-found lookups, with nothing telling it private
tasks are hidden from it. It kept searching through other tools,
endpoints and files and never answered within the turn.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/__tests__/agent-conversations.test.ts

@@ -1057,6 +1057,11 @@ describe("chat prompt policy", () => {
     const prompt = buildPaperclipTaskMarkdown({ issue: { id: "chat", identifier: null, title: "Chat", workMode: "ask", conversationAgentId: "agent" } });
     expect(prompt).toContain("/<its prefix>/issues/<identifier>");
   });
+  it("treats a same-company task the agent cannot find as possibly private instead of searching for a way in", () => {
+    expect(AGENT_CHAT_DIRECTIVE).toContain("A private task is hidden from you unless you have access to it");
+    expect(AGENT_CHAT_DIRECTIVE).toContain("it may be private rather than missing. Do not search for it further");
+    expect(AGENT_CHAT_DIRECTIVE).toContain("share it with you from its sharing controls");
+  });
   it("tells chat agents to keep every listed task linked, and where a long list goes", () => {
     expect(AGENT_CHAT_DIRECTIVE).toContain("write each task identifier in full");
     expect(AGENT_CHAT_DIRECTIVE).toContain("a range such as RUN-12–14 links only its first task");

server/src/services/agent-conversations.ts

@@ -120,6 +120,8 @@ A person's own display name and avatar belong to their account, and only they ca
 
 This conversation and your credentials belong to one company. A task identifier whose prefix differs from this conversation's prefix belongs to another company or to none, and you cannot read it here, even when the person can open it themselves: a lookup that is not found does not mean the task does not exist. Do not search for it further, guess its content or copy anything from it. Say that this chat can only work in this company, and that to use that task the person can switch to its company and open a chat there. Link the task at /<its prefix>/issues/<identifier>, taking the prefix from the identifier the person gave; this is the one link that does not use this conversation's prefix.
 
+Tasks and projects in this company can be private. A private task is hidden from you unless you have access to it: your searches, lists and direct lookups leave it out or return not found, even when the person who asks can open it. So when the person refers to a task in this company that one search does not find, especially one they call private, it may be private rather than missing. Do not search for it further through other tools, endpoints, files or activity records, and do not guess its content. Say that this chat cannot see that task, possibly because it is private, and that if they want you to work on it they can open the task and share it with you from its sharing controls, or paste the parts they want here.
+
 For status updates, distinguish recorded task status from active execution and verified progress. Read the latest relevant comments and run outcome before explaining a blocker or claiming work is underway. Use the advertised API tools for another task's details when needed. A completed dependency does not prove a block is stale; report the assignee's recorded reason. Agent configuration may be redacted: an empty configuration object without configuration-read permission does not prove settings are disabled or at their defaults. If the evidence is unavailable, say what you could verify and what remains unknown rather than guessing or recommending a status change.
 
 Keep discussion here and leave the conversation available for the next message. Link handed-off tasks in your reply; do not make this conversation blocked by their completion or wait for them. Paperclip will bring completed handed-off tasks back as a new input here so you can explain the result and link it without another user message. After creating an assigned task, let its own run execute the work; do not create its deliverables or change its execution status from this chat. Reply normally and end your turn; Paperclip manages the conversation waiting state. Do not change its status, create a review confirmation just to finish a reply, mark it complete, or poll for another reply. An accepted plan authorizes handoff to execution tasks, never implementation on this conversation. Honor normal approvals. Ask mode is non-mutating. Plan mode supports research and writing/revising the plan; hand off for execution only through the normal authorized workflow.`;