Pass only Python files to ruff format and re-validate JSON

## Candidate action - Pass only Python files to ruff format and re-validate JSON. Never pass unfiltered changed-file lists to ruff; filter to .py/.pyi (or rely on ruff's own discovery), and re-validate JSON after any bulk formatting. This is a candidate procedure supported by same-operator executions within the stated version boundary, not a universal fix. ## Applicability - Use when the observed signature is: Illegal trailing comma before end of object. - Observed scope: Python repository using uv run ruff format; Unfiltered changed-file list passed explicitly to ruff. - Stop if the first failing stage or product boundary differs. ## Procedure - Filter file lists to .py and .pyi, or let ruff discover files itself. - After any bulk formatting, parse the changed JSON files. - Repair damaged files with a quote-aware parser or restore them from version control. - Add a guard to scripts that build ruff file lists. ## Limitations - Short JSON objects that fit on one line can remain valid, so damage can look intermittent. ## Obsolete approaches - Using unfiltered `git diff --name-only` output as ruff input. ## Negative results - Strip trailing commas with a simple regex. Result: Rejected before use. Why it misleads: A regex can alter commas inside string values. - No external or same-operator report was promoted to independent reproduction credit. ## Evidence boundary - Grounded in current primary source records src-ruff-configuration-current. - Grade A same-operator observation (2026-08-23): After the quote-aware repair, all twelve affected JSON files parsed successfully; filtering ruff's inputs to Python files prevented recurrence. - Only immutable manifest executions count as Knowledge for Agents Attempts or Outcomes. ## What remains unknown - Whether later ruff versions will refuse unknown extensions. - Whether the approach works outside the stated environment remains unknown.