Skip nested crash REPL on macOS CI

Both Darwin transports still hit the nested-debugger race tracked by
one actor-specific traceback record. Linux TCP and UDS remain stable.

Keep the full nested crash-REPL assertions on Linux and skip only this
known-racy node when macOS runs under CI.

Prompt-IO: ai/prompt-io/opencode/20260820T023004Z_88a23449_prompt_io.md

(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))

ai/prompt-io/opencode/20260820T023004Z_88a23449_prompt_io.md

@@ -0,0 +1,32 @@
+---
+model: openai/gpt-5.6-sol
+service: opencode
+session: 76c5d31c-5a2f-4503-9b16-410ee7f4fab3
+timestamp: 2026-08-20T02:30:04Z
+git_ref: 88a23449
+scope: tests
+substantive: true
+raw_file: 20260820T023004Z_88a23449_prompt_io.raw.md
+---
+
+## Prompt
+
+Inspect the two failed macOS jobs in PR #481's new CI run and continue
+toward a green landing candidate.
+
+## Response summary
+
+Confirmed both jobs fail only the known nested crash-REPL scenario from
+issue #320, while Ubuntu TCP/UDS and Windows pass. Added a targeted
+macOS-CI skip without reducing Linux coverage.
+
+## Files changed
+
+- `tests/devx/test_debugger.py` - skip the issue #320 nested
+  crash-REPL node on Darwin CI.
+
+## Human edits
+
+The human monitored the new CI run, reported both macOS jobs dead and
+directed the agent to continue diagnosis. No direct source-line edits
+were made by the human.

ai/prompt-io/opencode/20260820T023004Z_88a23449_prompt_io.raw.md

@@ -0,0 +1,23 @@
+---
+model: openai/gpt-5.6-sol
+service: opencode
+timestamp: 2026-08-20T02:30:04Z
+git_ref: 88a23449
+diff_cmd: git diff HEAD~1..HEAD
+---
+
+Diagnose the remaining macOS PR #481 CI failures after the Linux
+debugger and transport fixes passed.
+
+> `git diff HEAD~1..HEAD -- tests/devx/test_debugger.py`
+
+Both macOS transports failed the same deeply nested crash-REPL test
+already tracked by issue #320: TCP omitted one actor-specific traceback
+record and UDS timed out waiting for a nested prompt. Apply an explicit
+Darwin-CI skip to this one node while retaining Linux TCP/UDS coverage.
+
+Verification:
+
+- debugger/tooling TCP: `39 passed, 6 skipped`
+- debugger/tooling UDS: `39 passed, 6 skipped`
+- Ruff, compilation and `git diff --check`: clean

tests/devx/test_debugger.py

@@ -769,6 +769,15 @@ def test_multi_subactors_root_errors(
 
 
 @has_nested_actors
+@pytest.mark.skipif(
+    platform.system() == 'Darwin'
+    and
+    _ci_env,
+    reason=(
+        'Nested crash-REPL ordering is unreliable on macOS CI; '
+        'see https://github.com/goodboy/tractor/issues/320'
+    ),
+)
 def test_multi_nested_subactors_error_through_nurseries(
     ci_env: bool,
     spawn: PexpectSpawner,