[yunusarda-sudo]

Summary

In openadapt_flow/privacy.py:bind_text, bound values were replaced sequentially in descending length order using individual regex substitutions. Because ⟦ and . are non-word characters, a short value that also appears as a word within placeholder syntax (for example "task" in ⟦task.identity_1⟧) matched inside previously inserted placeholders, corrupting them into nested structures like ⟦⟦task.kind⟧.identity_1⟧.

Changes

1. Single-Pass Placeholder Binding (bind_text):
   • Construct a single regex pattern that matches existing placeholder tokens (\u27e6[^\u27e6\u27e7]*\u27e7) or whole-word value branches sorted by length descending.
   • Any already-present placeholder span is emitted unmodified.
   • Matched values are substituted via dictionary lookup in a single pass without re-scanning or corrupting inserted placeholders.
2. Tests:
   • Added test_task_value_cannot_rewrite_another_placeholder verifying that short values such as "task" cannot rewrite placeholder names.
   • Added test_bind_text_preserves_preexisting_placeholders ensuring pre-existing placeholders in text remain untouched.
   • Added test_short_value_overbinding_in_task_text_is_pinned pinning the intended privacy trade-off where values under 3 characters (e.g. "M") bind every whole-word occurrence in task text to prevent raw PHI transmission to the model.

Closes #2130.

Signed-off-by: Yunus Ardaguney yunusarda-sudo@users.noreply.github.com