Function checkWritePermissionForTool

src/utils/permissions/filesystem.ts:1205–1412

(
  tool: Tool<Input>,
  input: z.infer<Input>,
  toolPermissionContext: ToolPermissionContext,
  precomputedPathsToCheck?: readonly string[],
)

 *   stale value would silently check deny rules for the wrong path.
 */
export function checkWritePermissionForTool<Input extends AnyObject>(
  tool: Tool<Input>,
  input: z.infer<Input>,
  toolPermissionContext: ToolPermissionContext,
  precomputedPathsToCheck?: readonly string[],
): PermissionDecision {
  if (typeof tool.getPath !== 'function') {
    return {
      behavior: 'ask',
      message: `Claude requested permissions to use ${tool.name}, but you haven't granted it yet.`,
    }
  }
  const path = tool.getPath(input)

  // 1. Check for deny rules - check both the original path and resolved symlink path
  const pathsToCheck =
    precomputedPathsToCheck ?? getPathsForPermissionCheck(path)
  for (const pathToCheck of pathsToCheck) {
    const denyRule = matchingRuleForInput(
      pathToCheck,
      toolPermissionContext,
      'edit',
      'deny',
    )
    if (denyRule) {
      return {
        behavior: 'deny',
        message: `Permission to edit ${path} has been denied.`,
        decisionReason: {
          type: 'rule',
          rule: denyRule,
        },
      }
    }
  }

  // 1.5. Allow writes to internal editable paths (plan files, scratchpad)
  // This MUST come before isDangerousFilePathToAutoEdit check since .claude is a dangerous directory
  const absolutePathForEdit = expandPath(path)
  const internalEditResult = checkEditableInternalPath(
    absolutePathForEdit,
    input,
  )
  if (internalEditResult.behavior !== 'passthrough') {
    return internalEditResult
  }

  // 1.6. Check for .claude/** allow rules BEFORE safety checks
  // This allows session-level permissions to bypass the safety blocks for .claude/
  // We only allow this for session-level rules to prevent users from accidentally
  // permanently granting broad access to their .claude/ folder.
  //
  // matchingRuleForInput returns the first match across all sources. If the user
  // also has a broader Edit(.claude) rule in userSettings (e.g. from sandbox
  // write-allow conversion), that rule would be found first and its source check
  // below would fail. Scope the search to session-only rules so the dialog's
  // "allow Claude to edit its own settings for this session" option actually works.
  const claudeFolderAllowRule = matchingRuleForInput(