fix: avoid duplicate prompt context

CHANGELOG.md

@@ -18,6 +18,7 @@
 - Auto-reply: removed `autoReply` from Discord/Slack/Telegram channel configs; use `requireMention` instead (Telegram topics now support `requireMention` overrides).
 
 ### Fixes
+- Agent: avoid duplicating context/skills when SDK rebuilds the system prompt. (#418)
 - Signal: reconnect SSE monitor with abortable backoff; log stream errors. Thanks @nexty5870 for PR #430.
 - Gateway: pass resolved provider as messageProvider for agent runs so provider-specific tools are available. Thanks @imfing for PR #389.
 - Discord/Telegram: add per-request retry policy with configurable delays and docs.

src/agents/pi-embedded-runner.test.ts

@@ -1,10 +1,14 @@
 import type { AgentMessage, AgentTool } from "@mariozechner/pi-agent-core";
-import { SessionManager } from "@mariozechner/pi-coding-agent";
+import {
+  buildSystemPrompt,
+  SessionManager,
+} from "@mariozechner/pi-coding-agent";
 import { Type } from "@sinclair/typebox";
 import { describe, expect, it, vi } from "vitest";
 import {
   applyGoogleTurnOrderingFix,
   buildEmbeddedSandboxInfo,
+  createSystemPromptAppender,
   splitSdkTools,
 } from "./pi-embedded-runner.js";
 import type { SandboxContext } from "./sandbox.js";
@@ -105,6 +109,22 @@ describe("splitSdkTools", () => {
   });
 });
 
+describe("createSystemPromptAppender", () => {
+  it("appends without duplicating context files", () => {
+    const sentinel = "CONTEXT_SENTINEL_42";
+    const defaultPrompt = buildSystemPrompt({
+      cwd: "/tmp",
+      contextFiles: [{ path: "/tmp/AGENTS.md", content: sentinel }],
+    });
+    const appender = createSystemPromptAppender("APPEND_SECTION");
+    const finalPrompt = appender(defaultPrompt);
+    const occurrences = finalPrompt.split(sentinel).length - 1;
+    expect(typeof appender).toBe("function");
+    expect(occurrences).toBe(1);
+    expect(finalPrompt).toContain("APPEND_SECTION");
+  });
+});
+
 describe("applyGoogleTurnOrderingFix", () => {
   const makeAssistantFirst = () =>
     [

src/agents/pi-embedded-runner.ts

@@ -10,7 +10,6 @@ import type {
 } from "@mariozechner/pi-agent-core";
 import type { Api, AssistantMessage, Model } from "@mariozechner/pi-ai";
 import {
-  buildSystemPrompt,
   createAgentSession,
   discoverAuthStorage,
   discoverModels,
@@ -492,6 +491,16 @@ export function buildEmbeddedSandboxInfo(
   };
 }
 
+export function createSystemPromptAppender(
+  appendPrompt: string,
+): (defaultPrompt: string) => string {
+  const trimmed = appendPrompt.trim();
+  if (!trimmed) {
+    return (defaultPrompt) => defaultPrompt;
+  }
+  return (defaultPrompt) => `${defaultPrompt}\n\n${appendPrompt}`;
+}
+
 const BUILT_IN_TOOL_NAMES = new Set(["read", "bash", "edit", "write"]);
 
 type AnyAgentTool = AgentTool;
@@ -775,28 +784,23 @@ export async function compactEmbeddedPiSession(params: {
           params.config?.agent?.userTimezone,
         );
         const userTime = formatUserTime(new Date(), userTimezone);
-        const systemPrompt = buildSystemPrompt({
+        const appendPrompt = buildAgentSystemPromptAppend({
-          appendPrompt: buildAgentSystemPromptAppend({
+          workspaceDir: effectiveWorkspace,
-            workspaceDir: effectiveWorkspace,
+          defaultThinkLevel: params.thinkLevel,
-            defaultThinkLevel: params.thinkLevel,
+          extraSystemPrompt: params.extraSystemPrompt,
-            extraSystemPrompt: params.extraSystemPrompt,
+          ownerNumbers: params.ownerNumbers,
-            ownerNumbers: params.ownerNumbers,
+          reasoningTagHint,
-            reasoningTagHint,
+          heartbeatPrompt: resolveHeartbeatPrompt(
-            heartbeatPrompt: resolveHeartbeatPrompt(
+            params.config?.agent?.heartbeat?.prompt,
-              params.config?.agent?.heartbeat?.prompt,
+          ),
-            ),
+          runtimeInfo,
-            runtimeInfo,
+          sandboxInfo,
-            sandboxInfo,
+          toolNames: tools.map((tool) => tool.name),
-            toolNames: tools.map((tool) => tool.name),
+          modelAliasLines: buildModelAliasLines(params.config),
-            modelAliasLines: buildModelAliasLines(params.config),
+          userTimezone,
-            userTimezone,
+          userTime,
-            userTime,
-          }),
-          contextFiles,
-          skills: promptSkills,
-          cwd: effectiveWorkspace,
-          tools,
         });
+        const systemPrompt = createSystemPromptAppender(appendPrompt);
 
         // Pre-warm session file to bring it into OS page cache
         await prewarmSessionFile(params.sessionFile);
@@ -1100,28 +1104,23 @@ export async function runEmbeddedPiAgent(params: {
             params.config?.agent?.userTimezone,
           );
           const userTime = formatUserTime(new Date(), userTimezone);
-          const systemPrompt = buildSystemPrompt({
+          const appendPrompt = buildAgentSystemPromptAppend({
-            appendPrompt: buildAgentSystemPromptAppend({
+            workspaceDir: effectiveWorkspace,
-              workspaceDir: effectiveWorkspace,
+            defaultThinkLevel: thinkLevel,
-              defaultThinkLevel: thinkLevel,
+            extraSystemPrompt: params.extraSystemPrompt,
-              extraSystemPrompt: params.extraSystemPrompt,
+            ownerNumbers: params.ownerNumbers,
-              ownerNumbers: params.ownerNumbers,
+            reasoningTagHint,
-              reasoningTagHint,
+            heartbeatPrompt: resolveHeartbeatPrompt(
-              heartbeatPrompt: resolveHeartbeatPrompt(
+              params.config?.agent?.heartbeat?.prompt,
-                params.config?.agent?.heartbeat?.prompt,
+            ),
-              ),
+            runtimeInfo,
-              runtimeInfo,
+            sandboxInfo,
-              sandboxInfo,
+            toolNames: tools.map((tool) => tool.name),
-              toolNames: tools.map((tool) => tool.name),
+            modelAliasLines: buildModelAliasLines(params.config),
-              modelAliasLines: buildModelAliasLines(params.config),
+            userTimezone,
-              userTimezone,
+            userTime,
-              userTime,
-            }),
-            contextFiles,
-            skills: promptSkills,
-            cwd: effectiveWorkspace,
-            tools,
           });
+          const systemPrompt = createSystemPromptAppender(appendPrompt);
 
           // Pre-warm session file to bring it into OS page cache
           await prewarmSessionFile(params.sessionFile);