fix(core): preserve dollar sequences in prompt template substitutions

Author: nramanath

packages/core/src/prompts/utils.test.ts

@@ -13,6 +13,7 @@ import {
 } from './utils.js';
 import type { Config } from '../config/config.js';
 import type { ToolRegistry } from '../tools/tool-registry.js';
+import * as snippets from './snippets.js';
 
 vi.mock('../utils/paths.js', () => ({
   homedir: vi.fn().mockReturnValue('/mock/home'),
@@ -312,4 +313,40 @@ describe('applySubstitutions', () => {
     );
     expect(result).toBe('A plain prompt with no variables.');
   });
+
+  it('should preserve dollar sequences in ${AgentSkills} verbatim', () => {
+    const result = applySubstitutions(
+      'Skills: ${AgentSkills} | Tail',
+      mockConfig,
+      "echo $'a\\nb' and $$ and $& and $VAR",
+    );
+    expect(result).toBe("Skills: echo $'a\\nb' and $$ and $& and $VAR | Tail");
+  });
+
+  it('should preserve dollar sequences in ${SubAgents} verbatim', () => {
+    vi.mocked(snippets.renderSubAgents).mockReturnValueOnce(
+      "echo $'a\\nb' and $$ and $&",
+    );
+    const result = applySubstitutions(
+      'Agents: ${SubAgents} | Tail',
+      mockConfig,
+      '',
+      true,
+    );
+    expect(result).toBe("Agents: echo $'a\\nb' and $$ and $& | Tail");
+  });
+
+  it('should preserve dollar sequences in ${AvailableTools} verbatim', () => {
+    (mockConfig as unknown as { toolRegistry: ToolRegistry }).toolRegistry = {
+      getAllToolNames: vi.fn().mockReturnValue(["echo $'a\\nb'", '$$', '$&']),
+      getAllTools: vi.fn().mockReturnValue([]),
+    } as unknown as ToolRegistry;
+
+    const result = applySubstitutions(
+      'Tools: ${AvailableTools} | Tail',
+      mockConfig,
+      '',
+    );
+    expect(result).toContain("- echo $'a\\nb'\n- $$\n- $& | Tail");
+  });
 });

packages/core/src/prompts/utils.ts

@@ -69,7 +69,7 @@ export function applySubstitutions(
 ): string {
   let result = prompt;
 
-  result = result.replace(/\${AgentSkills}/g, skillsPrompt);
+  result = result.replace(/\${AgentSkills}/g, () => skillsPrompt);
 
   const activeSnippets = isGemini3 ? snippets : legacySnippets;
   const subAgentsContent = activeSnippets.renderSubAgents(
@@ -82,21 +82,21 @@ export function applySubstitutions(
       })),
   );
 
-  result = result.replace(/\${SubAgents}/g, subAgentsContent);
+  result = result.replace(/\${SubAgents}/g, () => subAgentsContent);
 
   const toolRegistry = context.toolRegistry;
   const allToolNames = toolRegistry.getAllToolNames();
   const availableToolsList =
     allToolNames.length > 0
       ? allToolNames.map((name) => `- ${name}`).join('\n')
       : 'No tools are currently available.';
-  result = result.replace(/\${AvailableTools}/g, availableToolsList);
+  result = result.replace(/\${AvailableTools}/g, () => availableToolsList);
 
   for (const toolName of allToolNames) {
     const varName = `${toolName}_ToolName`;
     result = result.replace(
       new RegExp(`\\\${\\b${varName}\\b}`, 'g'),
-      toolName,
+      () => toolName,
     );
   }