Creating a new translation over an English working copy returns a false existing-translation conflict

Problem/Motivation

Creating a Spanish draft on a node with a pending English working copy returns HTTP 409 saying the translation already exists, although the fixture has not created Spanish. The existing testEnglishWorkingCopyPreservedWhenAddingTranslation regression fails at McpDraftTranslationTest.php:193.

Steps to reproduce

1. Use MCP Sentinel 2.25.5 with Drupal 11.3.18 and PHP 8.3.
2. Create a published English page with translation and editorial moderation enabled.
3. Save a pending English draft.
4. POST the governed translation-create endpoint for Spanish with the live and working revision IDs in If-Match.

Expected: HTTP 200, Spanish draft created, pending English and published revision preserved. Actual: HTTP 409, "A translation for this language already exists. Continue it instead of creating it."

Reproduced in hosted previous-minor jobs 12546779, 12550363, and 12550414. An isolated PostgreSQL fixture on Drupal 11.3.18/PHP 8.3.32 reproduces the same failure: 1 test, 7 assertions, 1 failure. Dependency deprecations remain visible.

Proposed resolution

Investigate the revision re-read under the save lock. The candidate working revision is mutated before the existing-translation check; a cached revision may expose that in-memory mutation. This is a hypothesis pending instrumentation, not an established cause. Preserve stale-write rejection and all live/working translation data.

Remaining tasks

Confirm the cause, implement the bounded repair, rerun translation and preservation tests across supported Drupal versions, and review concurrency behavior.

User interface changes

None proposed.

API changes

Restore the existing successful translation-create contract; retain genuine conflict responses.

Data model changes

None proposed.