fix(dedupe): Track seen exceptions via attribute instead of ContextVar

[ericapisani]

Replace DedupeIntegration's weakref/ContextVar-based "last seen"
tracking with a _handled_by_sentry flag set directly on the
exception. This avoids the contextvar leaking across async contexts
and removes the need for reset_last_seen(), which the client used
to call after before_send dropped an exception.

Add a regression test for the case where the same exception instance
is re-raised (e.g. Django re-raising in middleware after a view
already handled it) to confirm it's still deduped correctly.

Fixes PY-2381
Fixes #6094

[linear-code]

PY-2381

[github-actions]

Codecov Results 📊

✅ 66097 passed | ⏭️ 2999 skipped | Total: 69096 | Pass Rate: 95.66% | Execution Time: 188m 32s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📉 -68610
Passed Tests	📉 -64487
Failed Tests	—
Skipped Tests	📉 -4123

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 2074 uncovered lines.
❌ Project coverage is 90.09%. Comparing base (f46fbb6) to head (900ad90).

Coverage diff

@@            Coverage Diff             @@
##        master       #PR       +/-##
==========================================
- Coverage    90.28%    90.09%    -0.19%
==========================================
  Files          193       179       -14
  Lines        25729     20923     -4806
  Branches      9496      7522     -1974
==========================================
+ Hits         23228     18849     -4379
- Misses        2501      2074      -427
- Partials      1432      1180      -252

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Dropped events still mark exceptions handled

Medium Severity

The _handled_by_sentry flag is set in the event processor, which runs before before_send. If before_send then drops the event, the flag stays set, so a later capture of the same exception instance is discarded by DedupeIntegration even though Sentry never received the first one. This reintroduces the previously fixed dropped-event dedupe bug.

Additional Locations (1)

• sentry_sdk/client.py#L601-L608

 

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