fix: fallback phoenix parent trace when parent tracing disabled

[Blackoutta]

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Summary

Fixes #36289

This PR ports the Phoenix parent trace fallback behavior described in the source-branch spec docs/superpowers/specs/2026-05-16-phoenix-parent-trace-fallback-design.md from commit f224813e63d33f582a79f5c76e573738620f28b0 into the current trace provider package layout.

Nested workflow traces can include a parent_trace_context so Phoenix/Arize can attach the child workflow under the parent workflow's tool node span. When the parent workflow has Phoenix/Arize tracing disabled, that parent span carrier can never be published to Redis. The current provider treats the missing carrier as pending and retries until the retry budget is exhausted.

The change keeps normal parent-carrier behavior for traceable parents, but falls back to a synthetic root keyed by parent_workflow_run_id when the parent app cannot publish Phoenix/Arize carrier data. Missing carriers remain retryable when the parent app can publish context, unknown parent workflow runs remain retryable, and malformed Redis carriers still fail as hard errors.

It also starts Phoenix synthetic root spans with an empty OpenTelemetry Context() so an ambient unsampled parent span cannot suppress or parent the synthetic root.

Screenshots

Before	After
N/A	N/A

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran make lint && make type-check (backend) and cd web && pnpm exec vp staged (frontend) to appease the lint gods

Validation run:

uv run --project api pytest api/providers/trace/trace-arize-phoenix/tests/unit_tests/arize_phoenix_trace/test_arize_phoenix_trace.py -q
uv run --project api pytest api/tests/unit_tests/tasks/test_ops_trace_task.py -q
uv run --project api ruff format --check api/providers/trace/trace-arize-phoenix/src/dify_trace_arize_phoenix/arize_phoenix_trace.py api/providers/trace/trace-arize-phoenix/tests/unit_tests/arize_phoenix_trace/test_arize_phoenix_trace.py
uv run --project api ruff check api/providers/trace/trace-arize-phoenix/src/dify_trace_arize_phoenix/arize_phoenix_trace.py api/providers/trace/trace-arize-phoenix/tests/unit_tests/arize_phoenix_trace/test_arize_phoenix_trace.py

[github-actions]

Pyrefly Diff

base → PR

--- /tmp/pyrefly_base.txt	2026-05-18 03:27:52.286187295 +0000
+++ /tmp/pyrefly_pr.txt	2026-05-18 03:27:44.229106557 +0000
@@ -72,6 +72,10 @@
   --> extensions/storage/huawei_obs_storage.py:31:20
 ERROR Argument `Module[Crypto.Hash.SHA1] | Unknown` is not assignable to parameter with type `Hash | HashModule` [bad-argument-type]
   --> libs/gmpy2_pkcs10aep_cipher.py:73:49
+ERROR `opentelemetry.trace.Tracer` is not assignable to attribute `tracer` with type `opentelemetry.sdk.trace.Tracer` [bad-assignment]
+    --> providers/trace/trace-arize-phoenix/tests/unit_tests/arize_phoenix_trace/test_arize_phoenix_trace.py:1722:29
+ERROR Object of class `NoneType` has no attribute `trace_id` [missing-attribute]
+    --> providers/trace/trace-arize-phoenix/tests/unit_tests/arize_phoenix_trace/test_arize_phoenix_trace.py:1744:12
 ERROR Argument `SimpleNamespace` is not assignable to parameter `dataset` with type `Dataset` in function `dify_vdb_alibabacloud_mysql.alibabacloud_mysql_vector.AlibabaCloudMySQLVectorFactory.init_vector` [bad-argument-type]
   --> providers/vdb/vdb-alibabacloud-mysql/tests/unit_tests/test_alibabacloud_mysql_factory.py:42:38
 ERROR Argument `SimpleNamespace` is not assignable to parameter `dataset` with type `Dataset` in function `dify_vdb_alibabacloud_mysql.alibabacloud_mysql_vector.AlibabaCloudMySQLVectorFactory.init_vector` [bad-argument-type]

[github-actions]

Pyrefly Type Coverage

Metric	Base	PR	Delta
Type coverage	0.00%	43.70%	+43.70%
Strict coverage	0.00%	43.22%	+43.22%
Typed symbols	0	22,156	+22,156
Untyped symbols	0	28,859	+28,859
Modules	0	2558	+2,558