"j \SrSSKJr SSKJr SSKJr SSKJr \(aSSK J r S Sjr g ) u Anthropic `container_upload` placement and rejected-container retry. **Placement.** The server only materializes a `container_upload` that falls inside the turn it is generating — everything after the last completed assistant response. A block in an earlier finished turn is inert (https://github.com/pydantic/pydantic-ai/issues/7775). A `tool_use`/`tool_result` exchange does not end the turn. The blocks are recomputed from static `CodeExecutionTool.files` every request, so a message that carries them must carry them on every later request too. Tracking the tail, or pinning first-and-last, moves the insertion point as history grows and busts the cacheable prefix. So they go on every user message except one whose content is only `tool_result` blocks. That message never opens a turn, so the prompt that did already carries the block. The skip is also required: `_drop_unpaired_native_tool_calls` keeps an unpaired native call only while every later message is that shape — the one shape Anthropic accepts when a client-tool call is mixed with code execution (https://platform.claude.com/docs/en/agents-and-tools/tool-use/code-execution-tool#how-code-execution-works). Adding a block there retroactively invalidates that decision and the next request 400s with `bash_code_execution tool use ... was found without ...`. Each message gets its own block objects. Later passes mutate blocks in place (`cache_control`); sharing one dict would smear a write across every message. **Retry.** Anthropic's documented recovery for a container that cannot be reused: Send the request again without the `container` parameter to get a new container. https://platform.claude.com/docs/en/agents-and-tools/tool-use/code-execution-tool#container-reuse The docs do not name the error. The shape we measured is 500 with a generic `api_error` body (`Internal server error`) when a history-resolved id is paired with `container_upload` blocks — not the 404 a never-existed id returns. That body is the same envelope as any other Anthropic 500, so wording cannot distinguish this failure; the guard keys on the request shape instead. Containers expire 30 days after creation; after ~5 minutes of inactivity they are checkpointed and a request inside that window restores them. `expires_at` is a shorter rolling value that does not report the 30-day limit. The recorded history-resolved id was created on 2026-06-30 and retried on 2026-08-28, about 59 days later, so it had expired. Its generic 500 with `container_upload` has no typed error or discriminator; that gap is https://github.com/pydantic/pydantic-ai/issues/7833. The guard needs both halves of that shape: an id we resolved from history, and uploads on the wire. A caller-set `anthropic_container` and a `pause_turn` reconnect id stay on the wire. One retry, not a loop; the client's `max_retries` still multiplies it. If Anthropic ever returns the typed error the docs imply, widen this guard to it and drop the 500 special case. ) annotations)Sequence) TYPE_CHECKING is_str_dict)BetaContentBlockParamcJ[U5=(a [SU55$)uZTrue when a user message is only `tool_result` blocks — answers a turn, never opens one.c3V# UHn[U5=(a USS:Hv M! g7f)type tool_resultNr).0blocks e/home/mande/repo/quber/.venv/lib/python3.13/site-packages/pydantic_ai/models/_anthropic_containers.py &is_tool_result_only..As) ldk[`U!3!Vf 8V!Vdks'))boolall)contents ris_tool_result_onlyr?s = lS ldk lllN)rzSequence[BetaContentBlockParam]returnr) __doc__ __future__rcollections.abcrtypingr_utilsranthropic.types.betar rrrr s'/b#$  mr