From 328a44695fbbb3c0bea684211ac91f2ef36b3223 Mon Sep 17 00:00:00 2001
From: Vincent Koc <vincentkoc@ieee.org>
Date: Mon, 22 Jun 2026 06:17:14 +0800
Subject: [PATCH] chore(deadcode): remove unused agent-core prompt formatter

---
 packages/agent-core/package.json              |  4 --
 .../agent-core/src/harness/system-prompt.ts   | 44 -------------------
 packages/agent-core/src/harness/types.ts      |  9 +---
 packages/agent-core/src/index.ts              |  1 -
 tsdown.config.ts                              |  1 -
 5 files changed, 2 insertions(+), 57 deletions(-)
 delete mode 100644 packages/agent-core/src/harness/system-prompt.ts

diff --git a/packages/agent-core/package.json b/packages/agent-core/package.json
index 1f08fc311438..a6ceec12aaf7 100644
--- a/packages/agent-core/package.json
+++ b/packages/agent-core/package.json
@@ -89,10 +89,6 @@
       "types": "./dist/harness/skills.d.ts",
       "default": "./dist/harness/skills.js"
     },
-    "./harness/system-prompt": {
-      "types": "./dist/harness/system-prompt.d.ts",
-      "default": "./dist/harness/system-prompt.js"
-    },
     "./harness/utils/truncate": {
       "types": "./dist/harness/utils/truncate.d.ts",
       "default": "./dist/harness/utils/truncate.js"
diff --git a/packages/agent-core/src/harness/system-prompt.ts b/packages/agent-core/src/harness/system-prompt.ts
deleted file mode 100644
index 51a83549e400..000000000000
--- a/packages/agent-core/src/harness/system-prompt.ts
+++ /dev/null
@@ -1,44 +0,0 @@
-// Agent Core module implements system prompt behavior.
-import type { Skill } from "./types.js";
-
-/** Format model-visible skill metadata for inclusion in the harness system prompt. */
-export function formatSkillsForSystemPrompt(skills: Skill[]): string {
-  // Hidden skills can still be invoked directly by host code, but should not be
-  // advertised to the model for autonomous selection.
-  const visibleSkills = skills.filter((skill) => !skill.disableModelInvocation);
-  if (visibleSkills.length === 0) {
-    return "";
-  }
-
-  const lines = [
-    "The following skills provide specialized instructions for specific tasks.",
-    "Read the full skill file when the task matches its description.",
-    "If a skill's <version> differs from a previous turn, re-read its SKILL.md before using it.",
-    "When a skill file references a relative path, resolve it against the skill directory (parent of SKILL.md / dirname of the path) and use that absolute path in tool commands.",
-    "",
-    "<available_skills>",
-  ];
-
-  for (const skill of visibleSkills) {
-    lines.push("  <skill>");
-    lines.push(`    <name>${escapeXml(skill.name)}</name>`);
-    lines.push(`    <description>${escapeXml(skill.description)}</description>`);
-    lines.push(`    <location>${escapeXml(skill.filePath)}</location>`);
-    if (skill.promptVersion) {
-      lines.push(`    <version>${escapeXml(skill.promptVersion)}</version>`);
-    }
-    lines.push("  </skill>");
-  }
-
-  lines.push("</available_skills>");
-  return lines.join("\n");
-}
-
-function escapeXml(value: string): string {
-  return value
-    .replace(/&/g, "&amp;")
-    .replace(/</g, "&lt;")
-    .replace(/>/g, "&gt;")
-    .replace(/"/g, "&quot;")
-    .replace(/'/g, "&apos;");
-}
diff --git a/packages/agent-core/src/harness/types.ts b/packages/agent-core/src/harness/types.ts
index c5d85f7eec19..cba34e3a0220 100644
--- a/packages/agent-core/src/harness/types.ts
+++ b/packages/agent-core/src/harness/types.ts
@@ -42,8 +42,8 @@ export function toError(error: unknown): Error {
 /**
  * Skill loaded from a `SKILL.md` file or provided by an application.
  *
- * `name`, `description`, `filePath`, and optional `promptVersion` are inserted into the system prompt in an XML-formatted block as suggested by agentskills.io.
- * Use {@link formatSkillsForSystemPrompt} to generate the spec-compatible system prompt block.
+ * `name`, `description`, `filePath`, and optional `promptVersion` are available to host-owned prompt builders and
+ * direct skill invocation.
  */
 export interface Skill {
   /** Stable skill name used for lookup and model-visible listings. */
@@ -723,11 +723,6 @@ export type AgentHarnessEventResultMap = {
   settled: undefined;
 };
 
-/** Options for a prompt submitted through AgentHarness. */
-export interface AgentHarnessPromptOptions {
-  images?: ImageContent[];
-}
-
 /** Queued messages removed by an abort operation. */
 export interface AbortResult {
   clearedSteer: AgentMessage[];
diff --git a/packages/agent-core/src/index.ts b/packages/agent-core/src/index.ts
index 92d9b5e12644..7a959646bf99 100644
--- a/packages/agent-core/src/index.ts
+++ b/packages/agent-core/src/index.ts
@@ -11,7 +11,6 @@ export * from "./harness/env/kill-tree.js";
 export * from "./harness/messages.js";
 export * from "./harness/prompt-template-arguments.js";
 export * from "./harness/skills.js";
-export * from "./harness/system-prompt.js";
 export * from "./harness/types.js";
 export * from "./harness/session/jsonl-storage.js";
 export * from "./harness/session/memory-storage.js";
diff --git a/tsdown.config.ts b/tsdown.config.ts
index 0714e0d38c35..9418df0141bf 100644
--- a/tsdown.config.ts
+++ b/tsdown.config.ts
@@ -351,7 +351,6 @@ function buildAgentCoreDistEntries(): Record<string, string> {
     "harness/prompt-template-arguments":
       "packages/agent-core/src/harness/prompt-template-arguments.ts",
     "harness/skills": "packages/agent-core/src/harness/skills.ts",
-    "harness/system-prompt": "packages/agent-core/src/harness/system-prompt.ts",
     "harness/utils/truncate": "packages/agent-core/src/harness/utils/truncate.ts",
   };
 }