fix: prevent E2BIG error when system prompt is too long for Claude Code CLI

src/integrations/claude-code/__tests__/run.spec.ts

@@ -1,4 +1,4 @@
-import { describe, test, expect, vi, beforeEach } from "vitest"
+import { describe, test, expect, vi, afterEach, beforeEach } from "vitest"
 
 // Mock vscode workspace
 vi.mock("vscode", () => ({
@@ -287,4 +287,88 @@ describe("runClaudeCode", () => {
 		consoleErrorSpy.mockRestore()
 		await generator.return(undefined)
 	})
+
+	describe("system prompt truncation", () => {
+		test("should truncate system prompt when memory bank content is detected", async () => {
+			const { runClaudeCode } = await import("../run")
+
+			const longSystemPrompt = `You are Claude Code, Anthropic's official CLI for Claude.
+You are Kilo Code, a highly skilled software engineer.
+
+RULES
+
+All responses MUST follow specific guidelines.
+
+USER'S CUSTOM INSTRUCTIONS
+
+The following additional instructions are provided by the user, and should be followed to the best of your ability without interfering with the TOOL USE guidelines.
+
+Very long memory bank content that would cause E2BIG errors when passed as command line argument...`.repeat(100)
+
+			const options = {
+				systemPrompt: longSystemPrompt,
+				messages: [{ role: "user" as const, content: "Hello" }],
+			}
+
+			const generator = runClaudeCode(options)
+
+			// Since we're mocking execa, we can check what arguments were passed
+			await generator.next()
+
+			expect(mockExeca).toHaveBeenCalledWith(
+				"claude",
+				expect.arrayContaining([
+					"-p",
+					"--system-prompt",
+					expect.stringMatching(/^You are Claude Code.*RULES.*All responses MUST follow.*$/s),
+				]),
+				expect.any(Object)
+			)
+
+			// Verify the system prompt was truncated
+			const call = mockExeca.mock.calls[0]
+			const systemPromptArg = call[1][call[1].indexOf("--system-prompt") + 1]
+			expect(systemPromptArg).not.toContain("USER'S CUSTOM INSTRUCTIONS")
+			expect(systemPromptArg.length).toBeLessThan(longSystemPrompt.length)
+		})
+
+		test("should truncate system prompt when it exceeds maximum safe size", async () => {
+			const { runClaudeCode } = await import("../run")
+
+			const veryLongSystemPrompt = "You are a helpful assistant. ".repeat(2000) // ~60KB
+
+			const options = {
+				systemPrompt: veryLongSystemPrompt,
+				messages: [{ role: "user" as const, content: "Hello" }],
+			}
+
+			const generator = runClaudeCode(options)
+			await generator.next()
+
+			// Verify the system prompt was truncated to safe size
+			const call = mockExeca.mock.calls[0]
+			const systemPromptArg = call[1][call[1].indexOf("--system-prompt") + 1]
+			expect(systemPromptArg.length).toBeLessThanOrEqual(32000)
+			expect(systemPromptArg.length).toBeLessThan(veryLongSystemPrompt.length)
+		})
+
+		test("should not truncate normal-sized system prompts", async () => {
+			const { runClaudeCode } = await import("../run")
+
+			const normalSystemPrompt = "You are a helpful assistant."
+
+			const options = {
+				systemPrompt: normalSystemPrompt,
+				messages: [{ role: "user" as const, content: "Hello" }],
+			}
+
+			const generator = runClaudeCode(options)
+			await generator.next()
+
+			// Verify the system prompt was not truncated
+			const call = mockExeca.mock.calls[0]
+			const systemPromptArg = call[1][call[1].indexOf("--system-prompt") + 1]
+			expect(systemPromptArg).toBe(normalSystemPrompt)
+		})
+	})
 })

src/integrations/claude-code/run.ts

@@ -110,10 +110,14 @@ const CLAUDE_CODE_TIMEOUT = 600000 // 10 minutes
 function runProcess({ systemPrompt, messages, path, modelId }: ClaudeCodeOptions) {
 	const claudePath = path || "claude"
 
+	// Truncate system prompt to avoid E2BIG errors
+	// Keep only the role definition part, as Claude Code CLI loads memory bank from CLAUDE.md
+	const truncatedSystemPrompt = truncateSystemPrompt(systemPrompt)
+
 	const args = [
 		"-p",
 		"--system-prompt",
-		systemPrompt,
+		truncatedSystemPrompt,
 		"--verbose",
 		"--output-format",
 		"stream-json",
@@ -198,3 +202,54 @@ function attemptParseChunk(data: string): ClaudeCodeMessage | null {
 		return null
 	}
 }
+
+/**
+ * Truncates the system prompt to avoid E2BIG errors when spawning subprocess.
+ * Keeps only the role definition part since Claude Code CLI loads memory bank from CLAUDE.md.
+ *
+ * The system prompt structure typically follows:
+ * 1. Role definition (essential)
+ * 2. Memory bank instructions with content (can be large, not needed for Claude Code CLI)
+ *
+ * @param systemPrompt The full system prompt
+ * @returns Truncated system prompt containing only the role definition
+ */
+function truncateSystemPrompt(systemPrompt: string): string {
+	// Look for common patterns that indicate the start of memory bank content
+	const memoryBankIndicators = [
+		"USER'S CUSTOM INSTRUCTIONS",
+		"The following additional instructions are provided by the user",
+		"# Rules from",
+		"# Memory Bank",
+		"CLAUDE.md",
+		"memory bank",
+		"custom instructions"
+	]
+
+	// Find the first occurrence of any memory bank indicator
+	let truncationPoint = systemPrompt.length
+
+	for (const indicator of memoryBankIndicators) {
+		const index = systemPrompt.indexOf(indicator)
+		if (index !== -1 && index < truncationPoint) {
+			truncationPoint = index
+		}
+	}
+
+	// If we found a truncation point, cut off there
+	if (truncationPoint < systemPrompt.length) {
+		const truncated = systemPrompt.substring(0, truncationPoint).trim()
+		console.log(`System prompt truncated from ${systemPrompt.length} to ${truncated.length} characters`)
+		return truncated
+	}
+
+	// If no memory bank content found, but still very long, truncate to reasonable size
+	const MAX_SAFE_SIZE = 32000 // Conservative limit to avoid E2BIG
+	if (systemPrompt.length > MAX_SAFE_SIZE) {
+		const truncated = systemPrompt.substring(0, MAX_SAFE_SIZE).trim()
+		console.log(`System prompt truncated from ${systemPrompt.length} to ${truncated.length} characters (size limit)`)
+		return truncated
+	}
+
+	return systemPrompt
+}