feat: Remove string truncation for events

[alexander-alderman-webb]

Description

Remove the default string limit applied when serializing envelopes.

The max_value_length parameter is now optionally None, in which case there is no string truncation. The default value is changed to None.

The change follows on from raising the limit in #4632.

Replaces DEFAULT_MAX_VALUE_LENGTH with the 1024 literal in tests, which was the original limit.

Issues

Closes#4988
Closes PY-1916

Reminders

• Please add tests to validate your changes, and lint your code using tox -e linters.
• Add GH Issue ID & Linear ID (if applicable)
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
24358	1	24357	1709

View the top 1 failed test(s) by shortest run time

tests.tracing.test_decorator::test_trace_decorator_async_no_trx

Stack Traces | 0.053s run time

tests/tracing/test_decorator.py:81: in test_trace_decorator_async_no_trx
fake_debug.assert_called_once_with(
.../hostedtoolcache/Python/3.14.0.../x64/lib/python3.14/unittest/mock.py:996: in assert_called_once_with
raise AssertionError(msg)
E AssertionError: Expected 'mock' to be called once. Called 3 times.
E Calls: [call('[Monitor] health check negative, downsampling with a factor of %d', 10),
E call('Cannot create a child span for %s. Please start a Sentry transaction before calling this function.', 'time.sleep'),
E call('Cannot create a child span for %s. Please start a Sentry transaction before calling this function.', 'test_decorator.my_async_example_function'),
E call('[Monitor] health check negative, downsampling with a factor of %d', 10),
E call('Cannot create a child span for %s. Please start a Sentry transaction before calling this function.', 'time.sleep')].

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[linear]

PY-1916 Remove max value length

[cursor]

Bug: Truncation Limit Ignored for Local Variables

The serialize() call for local variables doesn't pass through the max_value_length parameter from serialize_frame(), causing local variables to never be truncated even when users explicitly set max_value_length. This breaks the intended truncation behavior for stack frame local variables.

sentry_sdk/utils.py#L620-L624

sentry-python/sentry_sdk/utils.py

Lines 620 to 624 in 6238237

	defcurrent_stacktrace(
	include_local_variables=True, # type: bool
	include_source_context=True, # type: bool

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