Problem

test_invalid_url in the httplib ext test suite fails with a TypeError on Python 3.8+ (where wrapt 2.x is installed). The test expects subsegment.cause to be a dict, but it gets a str (a cause ID reference to a nested subsegment).

The root cause is that unwrap() in aws_xray_sdk/ext/util.py is a silent no-op on wrapt 2.x, which causes wrapper accumulation across patch/unpatch cycles.

Root Cause

In wrapt 2.x, there are two different ObjectProxy classes:

• wrapt.ObjectProxy → wrapt.proxies.ObjectProxy (pure Python, new in 2.x)
• FunctionWrapper inherits from → _wrappers.ObjectProxy (C extension)

These are different class objects with different id()s. The unwrap() function checks:

if f and isinstance(f, wrapt.ObjectProxy) and hasattr(f, "__wrapped__"):

This isinstance() check always returns False for wrapt-wrapped functions on wrapt 2.x, so unwrap() never actually unwraps anything.

Impact

Since unwrap() is a no-op, every unpatch() → patch() cycle adds another wrapper layer without removing the previous one:

• In tests: The construct_ctx fixture calls patch()/unpatch() per test. By the 5th test (test_invalid_url), _send_request has 5 nested wrappers → 5 nested subsegments. Only the innermost gets the real exception dict; outer ones get string cause IDs → TypeError.
• In production: Any application calling unpatch()/patch() (e.g. during reconfiguration) accumulates wrapper layers, causing subsegment bloat on every patched call.
• Affects all ext modules that use unwrap(), not just httplib.

Why exactly 5 subsegments (not infinite)

Not recursion — just test position. test_invalid_url is the 5th test function in the file. Each prior test adds one wrapper layer via the fixture's patch/unpatch cycle.

Why it doesn't reproduce on macOS

The wrapt 2.x C extension wheel may not be available or may have a different class hierarchy on macOS, causing the pure-Python fallback to be used where the classes may be unified. On Linux (including GitHub Actions Ubuntu runners), the C extension .so is always present.

Fix

Remove the isinstance(f, wrapt.ObjectProxy) check from unwrap(). The hasattr(f, "__wrapped__") check is sufficient to identify wrapt-wrapped functions and works across all wrapt versions:

def unwrap(obj, attr):
    f = getattr(obj, attr, None)
    if f and hasattr(f, "__wrapped__"):
        setattr(obj, attr, f.__wrapped__)

Verification

Confirmed locally on Linux with wrapt 2.1.2 + Python 3.12:

1. Before fix: 5 patch/unpatch cycles → wrapper depth 5 → 5 nested subsegments
2. After fix: 5 patch/unpatch cycles → wrapper depth stays at 1 → 1 subsegment with correct cause=dict
3. test_invalid_url passes with original test code (no workaround needed)

Changes

• aws_xray_sdk/ext/util.py: Remove broken isinstance(f, wrapt.ObjectProxy) guard from unwrap()
• tests/ext/httplib/test_httplib.py: No changes needed (original test code works with the fix)

Ticket: apm-telegen-2729