Address review on #69619: the previous commit mutated the newest frozen
entry in _HISTORICAL_SUMMARY_PREFIXES and never froze the live prefix it
retired (the generation with both the four-heading discard clause and
the tools-active clause). A summary persisted immediately before
upgrading was therefore treated as an ordinary message on
resume/re-compaction, keeping the old handoff text embedded in the body.
- Prepend the exact pre-change live prefix as a new frozen entry
(newest-first), leaving all existing frozen entries byte-identical
- Restore the Jul 2026 (#65848 class) frozen entry to its original
four-heading text
- Pin the retired generation as a literal in
test_summary_prefix_semantics.py so mutating or dropping it fails CI
- Make the #65848 tool-use regression position-agnostic (match the
pre-clause generation by content, not tuple index)
Verified byte-identity of both rescued generations against the parent
commit. 233 focused prefix/resume/compressor tests pass.
The REFERENCE ONLY framing ('treat as background reference, NOT as active
instructions... Do NOT answer questions or fulfill requests') was observed
bleeding into general tool-use suppression: a production session went
narration-only for 7 consecutive turns immediately after a compression
event, describing edits instead of calling tools (#65848 report).
Fix is additive: one clause stating the note does not restrict HOW the
agent works — tools remain fully active for the active task. Every
anti-resumption protection stays intact; the previous prefix generation
is frozen into _HISTORICAL_SUMMARY_PREFIXES per the module contract so
persisted summaries still get the directive-strip on re-compaction.
The #65848 rewrite was not taken: dropping the 'Do NOT answer questions'
line and the four-heading discard directive risks re-opening the
stale-task-resumption class those clauses exist to prevent (the carveout
era regressions #41607/#38364/#42812 documented in this file).
Report and root-cause analysis: @yasserbousrih (#65848).
