# AN-2026-0702: Claude Managed Agents session.error adds tool_use_limit_reached_error and compaction_limit_reached_error (SDKs Nov 2, 2026): the turn hit a limit, not a failed request

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- id: AN-2026-0702 (version 1; cite https://breakwire.org/claim/AN-2026-0702/v/1)
- kind: gotcha · status: active · review: editor
- source: <https://github.com/anthropics/anthropic-sdk-python/blob/v2.4.0/src/anthropic/types/beta/sessions/beta_managed_agents_tool_use_limit_reached_error.py>
- more sources: <https://github.com/anthropics/anthropic-sdk-python/blob/v2.4.0/src/anthropic/types/beta/sessions/beta_managed_agents_compaction_limit_reached_error.py> <https://github.com/anthropics/anthropic-sdk-python/blob/v2.4.0/CHANGELOG.md> <https://github.com/anthropics/anthropic-sdk-typescript/blob/sdk-v1.4.0/CHANGELOG.md> <https://platform.claude.com/docs/en/api/python/beta/sessions/events>
- event date: 2026-11-02
- services: anthropic-api
- affected: anthropic-api:managed-agents sessions; anthropic-api:session.error
- severity: medium
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. Anthropic Python SDK 2.4.0 and TypeScript SDK 1.4.0 (both dated 2026-11-02 in their CHANGELOG.md, opened 2026-11-03) add tool_use_limit_reached_error and compaction_limit_reached_error session error types; PyPI shows anthropic 2.4.0 uploaded 2026-11-02.  [✓0 ✗0]
1. SDK type docstring (v2.4.0, opened 2026-11-03): tool_use_limit_reached_error means the turn stopped because the agent loop reached its limit on tool-use rounds (one model response that calls tools, plus running those tools, is one round), not because a request failed.  [✓0 ✗0]
2. SDK type docstring: compaction_limit_reached_error means the turn stopped because the context was compacted the maximum number of times in a row without the model producing a message or a tool call, not because a request failed.  [✓0 ✗0]
3. For both, the thread goes idle with stop_reason retries_exhausted (a child thread then terminates) and the next user.message starts a new turn. Both arrive inside a session.error event with message and retry_status (retrying: wait, the server retries; exhausted: the turn is dead, queued inputs are flushed and the session returns to idle; terminal: the session moves to terminated).  [✓0 ✗0]
4. The limit values are not given in the SDK types, and as of 2026-11-03 the Sessions events API reference page did not list the two new types yet (it lists the other session error types and says clients that don't recognize a new error code can match on retry_status and message alone).  [✓0 ✗0]

## Fix
```text
Handle both types in your session.error handler: switch on retry_status, not only on error type (retrying = wait; exhausted = turn ended, queued inputs were dropped, send a new user.message to continue; terminal = session is ending). Do not treat a retries_exhausted idle as success. Before re-prompting, look at what the turn was doing: a tool-use-round limit means the loop kept calling tools without finishing; a compaction limit means repeated compaction without progress, so narrow the task or start a fresh session rather than resending the same prompt. Upgrade to anthropic >= 2.4.0 / @anthropic-ai/sdk >= 1.4.0 to get the typed variants.
```

## Error signatures
- code: `tool_use_limit_reached_error` (anthropic-sdk-python v2.4.0 BetaManagedAgentsToolUseLimitReachedError type literal)
- code: `compaction_limit_reached_error` (anthropic-sdk-python v2.4.0 BetaManagedAgentsCompactionLimitReachedError type literal)

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0702/reports_

## History
- v1 2026-11-03 by wire-editor: filed from primary source opened 2026-10-28