fix(skill): wrap slash-activated skill content in system-reminder tags

.changeset/slash-skill-system-reminder.md

@@ -0,0 +1,6 @@
+---
+"@moonshot-ai/agent-core": patch
+"@moonshot-ai/kimi-code": patch
+---
+
+Fix slash-activated skills not being recognized by the model due to missing system reminder wrapper.

packages/agent-core/src/agent/context/notification-xml.ts

@@ -24,6 +24,8 @@
  * look alike (`agent-...`) but live in different namespaces.
  */
 
+import { escapeXmlAttr } from '#/utils/xml-escape';
+
 export function renderNotificationXml(data: Record<string, unknown>): string {
   const id = stringAttr(data['id'], 'unknown');
   const category = stringAttr(data['category'], 'unknown');
@@ -74,10 +76,7 @@ function truncateTailOutput(raw: string, maxLines: number, maxChars: number): st
 
 function stringAttr(value: unknown, fallback: string): string {
   if (typeof value !== 'string' || value.length === 0) return fallback;
-  // Attribute boundary safety: escape `&` and `"`. Body-text `<` / `>`
-  // stay untouched — the injection target is an LLM-visible transcript
-  // where double-escaping would be noisier than literal punctuation.
-  return value.replaceAll('&', '&amp;').replaceAll('"', '&quot;');
+  return escapeXmlAttr(value);
 }
 
 /** Like `stringAttr` but returns `undefined` instead of a fallback so the

packages/agent-core/src/agent/injection/plugin-session-start.ts

@@ -1,5 +1,6 @@
 import type { EnabledPluginSessionStart } from '../../plugin/types';
 import type { SkillDefinition } from '../../skill';
+import { escapeXmlAttr } from '../../utils/xml-escape';
 import { DynamicInjector } from './injector';
 
 export class PluginSessionStartInjector extends DynamicInjector {
@@ -43,11 +44,7 @@ function renderSessionStartBlock(
   skillContent: string,
 ): string {
   return (
-    `<plugin_session_start plugin="${escapeAttr(sessionStart.pluginId)}" ` +
-    `skill="${escapeAttr(skill.name)}">\n${skillContent}\n</plugin_session_start>`
+    `<plugin_session_start plugin="${escapeXmlAttr(sessionStart.pluginId)}" ` +
+    `skill="${escapeXmlAttr(skill.name)}">\n${skillContent}\n</plugin_session_start>`
   );
 }
-
-function escapeAttr(value: string): string {
-  return value.replaceAll('"', '&quot;');
-}

packages/agent-core/src/agent/skill/index.ts

@@ -6,6 +6,7 @@ import type { ContentPart } from '@moonshot-ai/kosong';
 import type { Agent } from '..';
 import { ErrorCodes, KimiError } from '#/errors';
 import { isUserActivatableSkillType, type SkillRegistry } from '../../skill';
+import { escapeXml } from '#/utils/xml-escape';
 import type { SkillActivationOrigin } from '../context';
 
 export class SkillManager {
@@ -23,6 +24,21 @@ export class SkillManager {
       throw new KimiError(ErrorCodes.SKILL_TYPE_UNSUPPORTED, `Skill "${skill.name}" cannot be activated by the user`);
     }
 
+    const skillContent = this.registry.renderSkillPrompt(skill, input.args ?? '');
+    const args = input.args;
+    const argsAttr = args ? ` args="${escapeXml(args)}"` : '';
+    const wrapped = [
+      {
+        type: 'text' as const,
+        text:
+          `<system-reminder>\n` +
+          `<kimi-skill-loaded name="${escapeXml(skill.name)}"${argsAttr}>\n` +
+          `${skillContent}\n` +
+          `</kimi-skill-loaded>\n` +
+          `</system-reminder>`,
+      },
+    ];
+
     this.recordActivation(
       {
         kind: 'skill_activation',
@@ -34,12 +50,7 @@ export class SkillManager {
         skillSource: skill.source,
         skillArgs: input.args,
       },
-      [
-        {
-          type: 'text',
-          text: this.registry.renderSkillPrompt(skill, input.args ?? ''),
-        },
-      ],
+      wrapped,
     );
   }
 

packages/agent-core/src/skill/parser.ts

@@ -6,6 +6,7 @@ import regexpEscape from 'regexp.escape';
 
 import type { SkillDefinition, SkillMetadata, SkillSource } from './types';
 import { isSupportedSkillType } from './types';
+import { escapeXmlTags } from '../utils/xml-escape';
 
 export class FrontmatterError extends Error {
   constructor(message: string, cause?: unknown) {
@@ -186,28 +187,28 @@ export function expandSkillParameters(
     const escaped = regexpEscape(name);
     content = content.replaceAll(
       new RegExp(`\\$${escaped}(?![\\[\\w])`, 'g'),
-      tokens[index] ?? '',
+      escapeXmlTags(tokens[index] ?? ''),
     );
   }
 
   content = content
     .replaceAll(/\$ARGUMENTS\[(\d+)\]/g, (_match, indexText: string) => {
       const index = Number.parseInt(indexText, 10);
-      return tokens[index] ?? '';
+      return escapeXmlTags(tokens[index] ?? '');
     })
     .replaceAll(/\$(\d+)(?!\w)/g, (_match, indexText: string) => {
       const index = Number.parseInt(indexText, 10);
-      return tokens[index] ?? '';
+      return escapeXmlTags(tokens[index] ?? '');
     })
-    .replaceAll('$ARGUMENTS', rawArgs);
+    .replaceAll('$ARGUMENTS', escapeXmlTags(rawArgs));
 
   const hasArgumentPlaceholder = content !== body;
   content = content
     .replaceAll('${KIMI_SKILL_DIR}', context.skillDir)
     .replaceAll('${KIMI_SESSION_ID}', context.sessionId ?? '');
 
   if (!hasArgumentPlaceholder && rawArgs.length > 0) {
-    return `${content}\n\nARGUMENTS: ${rawArgs}`;
+    return `${content}\n\nARGUMENTS: ${escapeXmlTags(rawArgs)}`;
   }
   return content;
 }

packages/agent-core/src/skill/registry.ts

@@ -2,6 +2,7 @@ import { expandSkillParameters, skillArgumentNames } from './parser';
 import { discoverSkills, type DiscoverSkillsOptions } from './scanner';
 import type { SkillDefinition, SkillRoot, SkillSource, SkippedSkill } from './types';
 import { isInlineSkillType, normalizeSkillName } from './types';
+import { escapeXmlAttr } from '../utils/xml-escape';
 
 const LISTING_DESC_MAX = 250;
 
@@ -98,7 +99,7 @@ export class SkillRegistry {
     const instructions = plugin.instructions;
     if (instructions === undefined || instructions.trim().length === 0) return content;
     return (
-      `<kimi-plugin-instructions plugin="${escapeAttr(plugin.id)}">\n` +
+      `<kimi-plugin-instructions plugin="${escapeXmlAttr(plugin.id)}">\n` +
       `${instructions}\n` +
       `</kimi-plugin-instructions>\n\n${content}`
     );
@@ -181,7 +182,3 @@ function formatModelSkill(skill: SkillDefinition): readonly string[] {
 function truncate(value: string, max: number): string {
   return value.length > max ? value.slice(0, max) : value;
 }
-
-function escapeAttr(value: string): string {
-  return value.replaceAll('&', '&amp;').replaceAll('"', '&quot;');
-}

packages/agent-core/src/tools/builtin/collaboration/skill-tool.ts

@@ -21,6 +21,7 @@ import type { BuiltinTool } from '../../../agent/tool';
 import type { ExecutableToolResult, ToolExecution } from '../../../loop/types';
 import { isInlineSkillType, type SkillDefinition } from '../../../skill';
 import { renderPrompt } from '../../../utils/render-prompt';
+import { escapeXml } from '../../../utils/xml-escape';
 import { toInputJsonSchema } from '../../support/input-schema';
 import { matchesGlobRuleSubject } from '../../support/rule-match';
 import skillDescriptionTemplate from './skill-tool.md';
@@ -163,10 +164,3 @@ function skillOrigin(
   };
 }
 
-function escapeXml(input: string): string {
-  return input
-    .replaceAll('&', '&')
-    .replaceAll('<', '&lt;')
-    .replaceAll('>', '&gt;')
-    .replaceAll('"', '&quot;');
-}

packages/agent-core/src/utils/xml-escape.ts

@@ -0,0 +1,18 @@
+/** Escape XML content — escapes both tag and attribute boundary chars (& < > ") */
+export function escapeXml(input: string): string {
+  return input
+    .replaceAll('&', '&amp;')
+    .replaceAll('<', '&lt;')
+    .replaceAll('>', '&gt;')
+    .replaceAll('"', '&quot;');
+}
+
+/** Escape XML attribute value — only escapes attribute boundary chars (& "), not tag chars */
+export function escapeXmlAttr(input: string): string {
+  return input.replaceAll('&', '&amp;').replaceAll('"', '&quot;');
+}
+
+/** Escape tag delimiters only — prevents XML tag injection without corrupting Markdown (& " stay literal) */
+export function escapeXmlTags(input: string): string {
+  return input.replaceAll('<', '&lt;').replaceAll('>', '&gt;');
+}

packages/agent-core/test/harness/skill-session.test.ts

@@ -184,7 +184,9 @@ describe('HarnessAPI session skills', () => {
     const records = await readMainWire(created.sessionDir);
     const prompt = records.find((record) => record['type'] === 'turn.prompt');
     const userMessage = records.find((record) => record['type'] === 'context.append_message');
-    const expectedPrompt = 'Review the requested file.\n\nARGUMENTS: src/app.ts';
+    const expectedPrompt =
+      '<system-reminder>\n<kimi-skill-loaded name="phase-one-review" args="src/app.ts">\n' +
+      'Review the requested file.\n\nARGUMENTS: src/app.ts\n</kimi-skill-loaded>\n</system-reminder>';
     expect(prompt).toMatchObject({
       type: 'turn.prompt',
       input: [{ type: 'text', text: expectedPrompt }],
@@ -264,11 +266,15 @@ describe('HarnessAPI session skills', () => {
     const prompt = records.find((record) => record['type'] === 'turn.prompt');
     const skillDir = await realpath(join(workDir, '.kimi-code', 'skills', 'templated-review'));
     const expectedPrompt = [
+      '<system-reminder>',
+      '<kimi-skill-loaded name="templated-review" args="&quot;src/app.ts&quot; careful">',
       'Target: src/app.ts',
       'Mode: careful',
       'Raw: "src/app.ts" careful',
       `Dir: ${skillDir}`,
       'Session: ses_skill_template',
+      '</kimi-skill-loaded>',
+      '</system-reminder>',
     ].join('\n');
     expect(prompt).toMatchObject({
       type: 'turn.prompt',
@@ -354,7 +360,7 @@ describe('HarnessAPI session skills', () => {
         content: [
           {
             type: 'text',
-            text: 'Review the requested file.\n\nARGUMENTS: src/app.ts',
+            text: '<system-reminder>\n<kimi-skill-loaded name="phase-one-review" args="src/app.ts">\nReview the requested file.\n\nARGUMENTS: src/app.ts\n</kimi-skill-loaded>\n</system-reminder>',
           },
         ],
         origin: {

packages/agent-core/test/tools/skill-tool.test.ts

@@ -236,7 +236,7 @@ describe('SkillTool execution', () => {
     await execute(tool, { skill: 'a&b', args: '<raw "value">' });
 
     expect(methods.recordSystemReminder.mock.calls[0]?.[0]).toContain(
-      '<kimi-skill-loaded name="a&amp;b" args="&lt;raw &quot;value&quot;&gt;">\nbody of a&b\n\nARGUMENTS: <raw "value">\n</kimi-skill-loaded>',
+      '<kimi-skill-loaded name="a&amp;b" args="&lt;raw &quot;value&quot;&gt;">\nbody of a&b\n\nARGUMENTS: &lt;raw "value"&gt;\n</kimi-skill-loaded>',
     );
     expect(methods.recordSkillActivation).toHaveBeenCalledTimes(1);
   });

packages/node-sdk/test/session-skills.test.ts

@@ -178,7 +178,7 @@ describe('Session skills', () => {
         input: [
           {
             type: 'text',
-            text: 'Review the requested file.\n\nARGUMENTS: src/app.ts',
+            text: '<system-reminder>\n<kimi-skill-loaded name="review" args="src/app.ts">\nReview the requested file.\n\nARGUMENTS: src/app.ts\n</kimi-skill-loaded>\n</system-reminder>',
           },
         ],
         origin: {