[JarryShaw]

Closes #2487

• Searched for similar pull requests
• Followed the coding style (make pylint, make mypy, make isort)
• make test passes, and a test case covers the change
• Added a changelog entry under docs/source/changelog/ and regenerated CHANGELOG.md, if the change is user-visible — N/A

What is the purpose of your pull request?

• fix — corrects a defect

---

Description of your pull request and other information

• HOPOPT, IPv6_Opts, IPv6_Route, IPv6_Frag, HIP, MH and the generic fallback (Shim6) return early in extension mode, before _decode_next_layer sets _next, so 'x' in layer raised AttributeError.

• These layers now hold NoPayload on that path. The upper layer belongs to the enclosing IPv6 header.

• Regression tests build frames in memory, including Shim6 in test_ipv6_ext_unit.py. The Shim6 test fails on origin/main with AttributeError.

• test_ipv6_ext_unit.py and test_ah_unit.py: 45 passed

• examples/generators/make_samples.py runs

• isort --check -l100 -p pcapkit clean on changed files

[JarryShaw]

NEEDS CHANGES (Sonnet, 7ceb5d5e9). Six read() methods, six new tests and the ESP/TCP probes hold on main.

• ipv6_ext.py IPv6_Ext.read generic fallback (if extension: return generic_ext) leaves _next unset: 'TCP' in a Shim6 layer still raises. Add self._next = NoPayload() with a Shim6 test, or drop it from Closes #2487.
• PR body: not template-shaped; add the 4-item checklist and the purpose heading, mirror fix(protocols): set NoPayload on terminal AH extension layer #2486's scaffold, keep at most 15 non-blank lines.
• Drop "as AH does (Protocol membership raises AttributeError on a terminal AH layer #2484)" from the commit message and "as AH does in fix(protocols): set NoPayload on terminal AH extension layer #2486" from the body; AH is not on main.

[github-actions]

Coverage: 94.50% (unit tier, Python 3.15, abbc6ca2e, Unit Tests run success)

Package	Statements	Missed	Branches	Partial	Cover
pcapkit (top level)	104	4	20	2	95.16%
pcapkit/const	19677	133	2628	120	98.85%
pcapkit/corekit	2605	74	818	37	96.52%
pcapkit/dumpkit	281	3	100	3	98.43%
pcapkit/foundation	3070	24	1072	26	98.79%
pcapkit/interface	138	4	52	3	96.32%
pcapkit/protocols	18066	194	4784	180	98.35%
pcapkit/toolkit	924	36	334	10	95.55%
pcapkit/utilities	502	7	144	5	98.14%
pcapkit/vendor	4449	1854	1020	167	55.11%

Per-file detail: the coverage-html artifact of this run.

[JarryShaw]

GOOD TO GO (Sonnet, abbc6ca2e). _next = NoPayload() appears once per changed class, only on the extension-mode early return; ESP and AH are untouched; 131 tests pass; the PR merges cleanly onto main.