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fix: prevent E2BIG errors and mixed system prompts in Claude Code provider #8120

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fix: prevent E2BIG errors and mixed system prompts in Claude Code provider #8120

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15 changes: 8 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 @@ -139,7 +139,7 @@ describe("runClaudeCode", () => {
expect(typeof result[Symbol.asyncIterator]).toBe("function")
})

test("should handle platform-specific stdin behavior", async () => {
test("should always pass system prompt via flag and messages via stdin", async () => {
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Good update to the test name! This now accurately reflects that we're testing consistent behavior across all platforms rather than platform-specific behavior.

const { runClaudeCode } = await import("../run")
const messages = [{ role: "user" as const, content: "Hello world!" }]
const systemPrompt = "You are a helpful assistant"
Expand All @@ -158,12 +158,13 @@ describe("runClaudeCode", () => {
results.push(chunk)
}

// On Windows, should NOT have --system-prompt in args
// On Windows, should now ALWAYS have --system-prompt in args
const [, args] = mockExeca.mock.calls[0]
expect(args).not.toContain("--system-prompt")
expect(args).toContain("--system-prompt")
expect(args).toContain(systemPrompt)

// Should pass both system prompt and messages via stdin
const expectedStdinData = JSON.stringify({ systemPrompt, messages })
// Should only pass messages via stdin (no longer includes system prompt)
const expectedStdinData = JSON.stringify(messages)
expect(mockStdin.write).toHaveBeenCalledWith(expectedStdinData, "utf8", expect.any(Function))

// Reset mocks for non-Windows test
Expand All @@ -179,12 +180,12 @@ describe("runClaudeCode", () => {
results2.push(chunk)
}

// On non-Windows, should have --system-prompt in args
// On non-Windows, should also have --system-prompt in args
const [, args2] = mockExeca.mock.calls[0]
expect(args2).toContain("--system-prompt")
expect(args2).toContain(systemPrompt)

// Should only pass messages via stdin
// Should only pass messages via stdin (consistent across platforms)
expect(mockStdin.write).toHaveBeenCalledWith(JSON.stringify(messages), "utf8", expect.any(Function))
})

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24 changes: 5 additions & 19 deletions src/integrations/claude-code/run.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -154,15 +154,9 @@ function runProcess({
maxOutputTokens,
}: ClaudeCodeOptions & { maxOutputTokens?: number }) {
const claudePath = path || "claude"
const isWindows = os.platform() === "win32"

// Build args based on platform
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)
}
// Build args - always pass system prompt as flag to avoid mixing with Claude Code's default
const args = ["-p", "--system-prompt", systemPrompt]
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Could we expand this comment to be more explicit about the dual purpose? Something like:

Suggested change
const args = ["-p", "--system-prompt", systemPrompt]
// Build args - always pass system prompt as flag to ensure Claude Code replaces its default prompt entirely
// (avoids mixing prompts) while keeping argv small by sending messages via stdin (avoids E2BIG)


args.push(
"--verbose",
Expand Down Expand Up @@ -196,17 +190,9 @@ 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)
}
// Prepare stdin data: only send messages to avoid E2BIG errors
// System prompt is now always passed via --system-prompt flag
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Great simplification! These comments clearly explain the rationale. Is the os import on line 7 still needed now that we've removed the platform-specific logic?

const stdinData = JSON.stringify(messages)

// Use setImmediate to ensure process is spawned before writing (prevents stdin race conditions)
setImmediate(() => {
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