Tencent/WeKnora · error

old_string and new_string are identical; no change would be

Error message

old_string and new_string are identical; no change would be made

What it means

applySandboxEdit in internal/agent/tools/sandbox_edit.go validates a file-edit request before applying it. It throws this error when the caller passes an edit where old_string and newString are byte-for-byte identical, which would be a no-op. The tool rejects it early so the agent/user notices the mistake instead of silently doing nothing.

Source

Thrown at internal/agent/tools/sandbox_edit.go:281

			"size":         len(content),
			"replacements": replacements,
		},
	}, nil
}

// Cleanup releases any resources.
func (t *EditSandboxFileTool) Cleanup(ctx context.Context) error {
	return nil
}

// applySandboxEdit performs an exact string replacement. replaceAll=false
// requires a unique match.
func applySandboxEdit(content, oldString, newString string, replaceAll bool) (string, int, error) {
	if oldString == "" {
		return "", 0, fmt.Errorf("old_string is required; copy the exact text to change, including whitespace")
	}
	if oldString == newString {
		return "", 0, fmt.Errorf("old_string and new_string are identical; no change would be made")
	}
	n := strings.Count(content, oldString)
	if n == 0 {
		return "", 0, fmt.Errorf("old_string was not found in the file. Copy the exact text (including whitespace) from the file")
	}
	if n > 1 && !replaceAll {
		return "", 0, fmt.Errorf(
			"old_string matched %d times. Include more surrounding context so it is unique, or set replace_all=true",
			n,
		)
	}
	if replaceAll {
		return strings.ReplaceAll(content, oldString, newString), n, nil
	}
	return strings.Replace(content, oldString, newString, 1), 1, nil
}

View on GitHub (pinned to 988cbb0330)

Solutions

1. Re-read the current file content and diff it against your intended final state to see what actually still needs changing.
2. Make newString genuinely different from oldString, or skip the edit entirely if the file already has the desired content.
3. If many arguments were passed positionally, verify oldString and newString weren't swapped or duplicated.

Example fix

// before
applySandboxEdit(content, oldString, oldString, false)
// after
if oldString == newString {
    return content // no-op; skip edit
}
newContent, _, err := applySandboxEdit(content, oldString, newString, false)

if oldString == newString {
    return fmt.Errorf("skipping edit: old_string equals new_string")
}

newContent, n, err := applySandboxEdit(content, oldString, newString, replaceAll)
if err != nil && strings.Contains(err.Error(), "identical") {
    // treat as no-op: re-read file and confirm desired state already present
    return content, nil
}

When it happens

Trigger: Calling the sandbox edit tool (via Execute) with old_string equal to new_string, e.g. retrying an edit after it already succeeded so the target text now equals the replacement, or copy-pasting the same block into both fields.

Common situations: An LLM agent re-sends a previously applied edit; a developer constructs an edit programmatically with the same variable for both arguments; whitespace-only 'changes' that turn out identical; retry loops without re-reading the file.

Related errors

• model ID cannot be empty
• unknown credential field:
• member_limit must be >= 0
• cannot request upgrade to same or lower role
• E2B timeout must be at least one second

AI-assisted analysis of Tencent/WeKnora@988cbb0330 (2026-09-02). Data as JSON: /api/errors/8e575138d51cadd2. Report an issue: GitHub.