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fix: resolve Claude CLI --system-prompt flag error by passing via stdin #6536

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fix: resolve Claude CLI --system-prompt flag error by passing via stdin #6536

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13 changes: 6 additions & 7 deletions src/integrations/claude-code/__tests__/run.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -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"
Expand All @@ -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
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@roomote roomote bot Aug 1, 2025

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This comment references Windows-specific behavior that no longer exists. Could we update it to reflect the unified behavior?

const [, args] = mockExeca.mock.calls[0]
expect(args).not.toContain("--system-prompt")

Expand All @@ -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)
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@roomote roomote bot Aug 1, 2025

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Same here - this comment still mentions platform differences that we've eliminated. Consider:

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 () => {
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25 changes: 7 additions & 18 deletions src/integrations/claude-code/run.ts
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Expand Up @@ -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
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@roomote roomote bot Aug 1, 2025

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The comment could be more descriptive about why we're making this change. Consider:

This would help future maintainers understand the reasoning behind this architectural decision.

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",
Expand Down Expand Up @@ -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
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@roomote roomote bot Aug 1, 2025

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These two comment lines could be consolidated for brevity:

// 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(() => {
Expand Down