diff --git a/src/integrations/claude-code/__tests__/run.spec.ts b/src/integrations/claude-code/__tests__/run.spec.ts
index fa5aedcd36..50e9dbefd8 100644
--- a/src/integrations/claude-code/__tests__/run.spec.ts
+++ b/src/integrations/claude-code/__tests__/run.spec.ts
@@ -141,7 +141,7 @@ describe("runClaudeCode", () => {
 		expect(typeof result[Symbol.asyncIterator]).toBe("function")
 	})
 
-	test("should handle platform-specific stdin behavior", async () => {
+	test("should pass system prompt and messages via stdin for all platforms", async () => {
 		const { runClaudeCode } = await import("../run")
 		const messages = [{ role: "user" as const, content: "Hello world!" }]
 		const systemPrompt = "You are a helpful assistant"
@@ -160,7 +160,7 @@ describe("runClaudeCode", () => {
 			results.push(chunk)
 		}
 
-		// On Windows, should NOT have --system-prompt in args
+		// Should NOT have --system-prompt in args
 		const [, args] = mockExeca.mock.calls[0]
 		expect(args).not.toContain("--system-prompt")
 
@@ -181,13 +181,12 @@ describe("runClaudeCode", () => {
 			results2.push(chunk)
 		}
 
-		// On non-Windows, should have --system-prompt in args
+		// Should NOT have --system-prompt in args (same behavior for all platforms now)
 		const [, args2] = mockExeca.mock.calls[0]
-		expect(args2).toContain("--system-prompt")
-		expect(args2).toContain(systemPrompt)
+		expect(args2).not.toContain("--system-prompt")
 
-		// Should only pass messages via stdin
-		expect(mockStdin.write).toHaveBeenCalledWith(JSON.stringify(messages), "utf8", expect.any(Function))
+		// Should pass both system prompt and messages via stdin (same as Windows)
+		expect(mockStdin.write).toHaveBeenCalledWith(expectedStdinData, "utf8", expect.any(Function))
 	})
 
 	test("should include model parameter when provided", async () => {
diff --git a/src/integrations/claude-code/run.ts b/src/integrations/claude-code/run.ts
index 3f438df0fc..2e3eff2aab 100644
--- a/src/integrations/claude-code/run.ts
+++ b/src/integrations/claude-code/run.ts
@@ -151,16 +151,10 @@ function runProcess({
 	maxOutputTokens,
 }: ClaudeCodeOptions & { maxOutputTokens?: number }) {
 	const claudePath = path || "claude"
-	const isWindows = os.platform() === "win32"
 
-	// Build args based on platform
+	// Build args - no longer passing system prompt as command line argument
 	const args = ["-p"]
 
-	// Pass system prompt as flag on non-Windows, via stdin on Windows (avoids cmd length limits)
-	if (!isWindows) {
-		args.push("--system-prompt", systemPrompt)
-	}
-
 	args.push(
 		"--verbose",
 		"--output-format",
@@ -193,17 +187,12 @@ function runProcess({
 		timeout: CLAUDE_CODE_TIMEOUT,
 	})
 
-	// Prepare stdin data: Windows gets both system prompt & messages (avoids 8191 char limit),
-	// other platforms get messages only (avoids Linux E2BIG error from ~128KiB execve limit)
-	let stdinData: string
-	if (isWindows) {
-		stdinData = JSON.stringify({
-			systemPrompt,
-			messages,
-		})
-	} else {
-		stdinData = JSON.stringify(messages)
-	}
+	// Pass both system prompt and messages via stdin for all platforms
+	// This avoids command line argument issues with --system-prompt flag
+	const stdinData = JSON.stringify({
+		systemPrompt,
+		messages,
+	})
 
 	// Use setImmediate to ensure process is spawned before writing (prevents stdin race conditions)
 	setImmediate(() => {