---
title: "Changes to Create Session"
method: POST
path: "/v1/sessions?beta=true"
---

# Changes to Create Session

`POST /v1/sessions?beta=true`

> Every recorded change to this endpoint, newest first.

## Timeline

Changed in 17 of 68 revisions.

- **2026-09-01** `d1d189d791d1` — 4 info
- **2026-08-19** `0042750ea1ee` — 8 breaking, 3 warning, 4 info
- **2026-08-17** `d2b230555b7f` — 31 breaking, 8 warning, 42 info
- **2026-08-06** `93d8fd7d6493` — 12 breaking, 10 info
- **2026-07-24** `a97790bd7f18` — 2 breaking, 6 info
- **2026-07-22** `5e4a8830793b` — 4 info
- **2026-07-02** `ec00b28b50c2` — 1 info
- **2026-06-30** `26335fd8487a` — 1 breaking, 1 warning
- **2026-06-30** `7caa9a75ddbc` — 2 info
- **2026-06-09** `2336fecb081b` — 1 info
- **2026-06-09** `00259327305f` — 2 info
- **2026-06-06** `546c704d347b` — 2 breaking, 10 info
- **2026-05-28** `f9d488f9290d` — 2 info
- **2026-05-06** `a4186730f56c` — 2 info
- **2026-04-23** `681182707119` — 1 breaking, 3 info
- **2026-04-16** `e0696f59ae07` — 1 info
- **2026-04-08** `69486316563e` — 1 info

## Changes

- **2026-09-01** `d1d189d791d1` — 4 info
  - added `subschema #2` to the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[#/components/schemas/BetaManagedAgentsModelConfigParams]/id` request property `anyOf` list
  - added `subschema #2` to the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[subschema #1: BetaManagedAgentsModel]/allOf[subschema #1: BetaManagedAgentsModel]/` request property `anyOf` list
  - added `subschema #2` to the `agent/model/id` response property `anyOf` list for the response status `200`
  - added `subschema #2` to the `agent/multiagent/anyOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/oneOf[#/components/schemas/BetaManagedAgentsSessionThreadAgent]/model/id` response property `anyOf` list for the response status `200`
- **2026-08-19** `0042750ea1ee` — 8 breaking, 3 warning, 4 info
  - added `#/components/schemas/BetaManagedAgentsBashToolConfig, #/components/schemas/BetaManagedAgentsEditToolConfig, #/components/schemas/BetaManagedAgentsReadToolConfig, #/components/schemas/BetaManagedAgentsWriteToolConfig, #/components/schemas/BetaManagedAgentsGlobToolConfig, #/components/schemas/BetaManagedAgentsGrepToolConfig, #/components/schemas/BetaManagedAgentsWebFetchToolConfig, #/components/schemas/BetaManagedAgentsWebSearchToolConfig` to the `agent/multiagent/anyOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/oneOf[#/components/schemas/BetaManagedAgentsSessionThreadAgent]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401]/configs/items/` response property `oneOf` list for the response status `200`
  - added `#/components/schemas/BetaManagedAgentsBashToolConfig, #/components/schemas/BetaManagedAgentsEditToolConfig, #/components/schemas/BetaManagedAgentsReadToolConfig, #/components/schemas/BetaManagedAgentsWriteToolConfig, #/components/schemas/BetaManagedAgentsGlobToolConfig, #/components/schemas/BetaManagedAgentsGrepToolConfig, #/components/schemas/BetaManagedAgentsWebFetchToolConfig, #/components/schemas/BetaManagedAgentsWebSearchToolConfig` to the `agent/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401]/configs/items/` response property `oneOf` list for the response status `200`
  - removed the required property `agent/multiagent/anyOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/oneOf[#/components/schemas/BetaManagedAgentsSessionThreadAgent]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401]/configs/items/enabled` from the response with the `200` status
  - removed the required property `agent/multiagent/anyOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/oneOf[#/components/schemas/BetaManagedAgentsSessionThreadAgent]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401]/configs/items/name` from the response with the `200` status
  - removed the required property `agent/multiagent/anyOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/oneOf[#/components/schemas/BetaManagedAgentsSessionThreadAgent]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401]/configs/items/permission_policy` from the response with the `200` status
  - removed the required property `agent/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401]/configs/items/enabled` from the response with the `200` status
  - removed the required property `agent/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401]/configs/items/name` from the response with the `200` status
  - removed the required property `agent/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401]/configs/items/permission_policy` from the response with the `200` status
  - removed the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/configs/items/enabled`
  - removed the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/configs/items/name`
  - removed the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/configs/items/permission_policy`
  - added discriminator to `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/configs/items/` request property
  - added `#/components/schemas/BetaManagedAgentsBashToolConfigParams, #/components/schemas/BetaManagedAgentsEditToolConfigParams, #/components/schemas/BetaManagedAgentsReadToolConfigParams, #/components/schemas/BetaManagedAgentsWriteToolConfigParams, #/components/schemas/BetaManagedAgentsGlobToolConfigParams, #/components/schemas/BetaManagedAgentsGrepToolConfigParams, #/components/schemas/BetaManagedAgentsWebFetchToolConfigParams, #/components/schemas/BetaManagedAgentsWebSearchToolConfigParams` to the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/configs/items/` request property `oneOf` list
  - added discriminator to `agent/multiagent/anyOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/oneOf[#/components/schemas/BetaManagedAgentsSessionThreadAgent]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401]/configs/items/` response property for the response status `200`
  - added discriminator to `agent/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401]/configs/items/` response property for the response status `200`
- **2026-08-17** `d2b230555b7f` — 31 breaking, 8 warning, 42 info
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[#/components/schemas/BetaManagedAgentsModelConfigParams]/effort` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[#/components/schemas/BetaManagedAgentsModelConfigParams]/inference_geo` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[#/components/schemas/BetaManagedAgentsModelConfigParams]/speed` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/skills/items/oneOf[#/components/schemas/BetaManagedAgentsAnthropicSkillParams]/version` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/skills/items/oneOf[#/components/schemas/BetaManagedAgentsCustomSkillParams]/version` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/system` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/configs/items/enabled` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/configs/items/permission_policy` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/default_config` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsMCPToolsetParams]/configs/items/enabled` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsMCPToolsetParams]/configs/items/permission_policy` became not nullable
  - the request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsMCPToolsetParams]/default_config` became not nullable
  - the request property `initial_events/items/oneOf[#/components/schemas/BetaManagedAgentsUserDefineOutcomeEventParams]/max_iterations` became not nullable
  - the request property `initial_events/items/oneOf[#/components/schemas/BetaManagedAgentsUserMessageEventParams]/content/items/oneOf[#/components/schemas/BetaManagedAgentsDocumentBlock]/context` became not nullable
  - the request property `initial_events/items/oneOf[#/components/schemas/BetaManagedAgentsUserMessageEventParams]/content/items/oneOf[#/components/schemas/BetaManagedAgentsDocumentBlock]/title` became not nullable
  - the request property `resources/items/oneOf[#/components/schemas/BetaManagedAgentsFileResourceParams]/mount_path` became not nullable
  - the request property `resources/items/oneOf[#/components/schemas/BetaManagedAgentsGitHubRepositoryResourceParams]/checkout` became not nullable
  - the request property `resources/items/oneOf[#/components/schemas/BetaManagedAgentsGitHubRepositoryResourceParams]/mount_path` became not nullable
  - the request property `resources/items/oneOf[#/components/schemas/BetaManagedAgentsMemoryStoreResourceParam]/access` became not nullable
  - the request property `resources/items/oneOf[#/components/schemas/BetaManagedAgentsMemoryStoreResourceParam]/instructions` became not nullable
  - the request property `title` became not nullable
  - response property `agent/description` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `agent/system` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `deployment_id` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `outcome_evaluations/items/explanation` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `resources/items/oneOf[#/components/schemas/BetaManagedAgentsMemoryStoreResource]/instructions` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `resources/items/oneOf[#/components/schemas/BetaManagedAgentsMemoryStoreResource]/mount_path` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `resources/items/oneOf[#/components/schemas/BetaManagedAgentsMemoryStoreResource]/name` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `title` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - the `resources/items/oneOf[#/components/schemas/BetaManagedAgentsMemoryStoreResource]/instructions` response property's maxLength was unset from `4096` for the response status `200`
  - the `resources/items/oneOf[#/components/schemas/BetaManagedAgentsGitHubRepositoryResource]/checkout` response's property type/format changed from `object`/`` to ``/`` for status `200`
  - removed `#/components/schemas/BetaManagedAgentsAgentToolsetDefaultConfigParams` from the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/default_config` request property `allOf` list
  - removed `#/components/schemas/BetaManagedAgentsEffortParams` from the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[#/components/schemas/BetaManagedAgentsModelConfigParams]/effort` request property `allOf` list
  - removed `#/components/schemas/BetaManagedAgentsMCPToolsetDefaultConfigParams` from the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsMCPToolsetParams]/default_config` request property `allOf` list
  - removed `#/components/schemas/BetaManagedAgentsMountMode` from the `resources/items/oneOf[#/components/schemas/BetaManagedAgentsMemoryStoreResourceParam]/access` request property `allOf` list
  - removed `#/components/schemas/BetaManagedAgentsPermissionPolicy` from the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/configs/items/permission_policy` request property `allOf` list
  - removed `#/components/schemas/BetaManagedAgentsPermissionPolicy` from the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsMCPToolsetParams]/configs/items/permission_policy` request property `allOf` list
  - removed `#/components/schemas/BetaManagedAgentsRepositoryCheckout` from the `resources/items/oneOf[#/components/schemas/BetaManagedAgentsGitHubRepositoryResourceParams]/checkout` request property `allOf` list
  - removed `#/components/schemas/BetaManagedAgentsSpeed` from the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[#/components/schemas/BetaManagedAgentsModelConfigParams]/speed` request property `allOf` list
  - added `#/components/schemas/BetaManagedAgentsAgentToolsetDefaultConfigParams, subschema #2` to the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsAgentToolset20260401Params]/default_config` request property `anyOf` list
  - …41 more
- **2026-08-06** `93d8fd7d6493` — 12 breaking, 10 info
  - added `#/components/schemas/BetaManagedAgentsSessionThreadAgent, #/components/schemas/BetaManagedAgentsAdvisor` to the `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/` response property `oneOf` list for the response status `200`
  - the `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/` response's property type/format changed from `object`/`` to ``/`` for status `200`
  - removed the required property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/description` from the response with the `200` status
  - removed the required property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/id` from the response with the `200` status
  - removed the required property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/mcp_servers` from the response with the `200` status
  - removed the required property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/model` from the response with the `200` status
  - removed the required property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/name` from the response with the `200` status
  - removed the required property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/skills` from the response with the `200` status
  - removed the required property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/system` from the response with the `200` status
  - removed the required property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/tools` from the response with the `200` status
  - removed the required property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/type` from the response with the `200` status
  - removed the required property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/version` from the response with the `200` status
  - added the new optional request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[#/components/schemas/BetaManagedAgentsModelConfigParams]/inference_geo`
  - added the new optional request property `budget`
  - added `redacted` discriminator mapping keys to the `initial_events/items/oneOf[#/components/schemas/BetaManagedAgentsUserMessageEventParams]/content/items/` request property
  - added `#/components/schemas/BetaManagedAgentsRedactedBlock` to the `initial_events/items/oneOf[#/components/schemas/BetaManagedAgentsUserMessageEventParams]/content/items/` request property `oneOf` list
  - added the optional property `agent/model/inference_geo` to the response with the `200` status
  - added the optional property `usage/allOf[#/components/schemas/BetaManagedAgentsSessionUsage]/active_seconds` to the response with the `200` status
  - added the optional property `usage/allOf[#/components/schemas/BetaManagedAgentsSessionUsage]/list_cost` to the response with the `200` status
  - added the optional property `usage/allOf[#/components/schemas/BetaManagedAgentsSessionUsage]/server_tool_use` to the response with the `200` status
  - added discriminator to `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/` response property for the response status `200`
  - added the required property `budget` to the response with the `200` status
- **2026-07-24** `a97790bd7f18` — 2 breaking, 6 info
  - removed `subschema #4, subschema #5, subschema #6, subschema #10, subschema #11` from the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[#/components/schemas/BetaManagedAgentsModelConfigParams]/id` request property `anyOf` list
  - removed `subschema #4, subschema #5, subschema #6, subschema #10, subschema #11` from the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[subschema #1: BetaManagedAgentsModel]/allOf[subschema #1: BetaManagedAgentsModel]/` request property `anyOf` list
  - added `subschema #4, subschema #5, subschema #6, subschema #7, subschema #11, subschema #12` to the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[#/components/schemas/BetaManagedAgentsModelConfigParams]/id` request property `anyOf` list
  - added `subschema #4, subschema #5, subschema #6, subschema #7, subschema #11, subschema #12` to the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[subschema #1: BetaManagedAgentsModel]/allOf[subschema #1: BetaManagedAgentsModel]/` request property `anyOf` list
  - added `subschema #4, subschema #5, subschema #6, subschema #7, subschema #11, subschema #12` to the `agent/model/id` response property `anyOf` list for the response status `200`
  - added `subschema #4, subschema #5, subschema #6, subschema #7, subschema #11, subschema #12` to the `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/model/id` response property `anyOf` list for the response status `200`
  - removed `subschema #4, subschema #5, subschema #6, subschema #10, subschema #11` from the `agent/model/id` response property `anyOf` list for the response status `200`
  - removed `subschema #4, subschema #5, subschema #6, subschema #10, subschema #11` from the `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/model/id` response property `anyOf` list for the response status `200`
- **2026-07-22** `5e4a8830793b` — 4 info
  - added the new optional request property `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/model/allOf[#/components/schemas/BetaManagedAgentsModelParams]/oneOf[#/components/schemas/BetaManagedAgentsModelConfigParams]/effort`
  - added the new optional request property `initial_events`
  - added the optional property `agent/model/effort` to the response with the `200` status
  - added the optional property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/model/effort` to the response with the `200` status
- **2026-07-02** `ec00b28b50c2` — 1 info
  - the `agent/allOf[#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams]/oneOf[subschema #2]/oneOf[#/components/schemas/BetaManagedAgentsAgentWithOverridesParams]/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomToolParams]/description` request property's maxLength was increased from `1024` to `4096`
- **2026-06-30** `26335fd8487a` — 1 breaking, 1 warning
  - added `#/components/schemas/BetaManagedAgentsCreateSessionAgentUnionParams` to the `agent` request property `allOf` list
  - removed `#/components/schemas/BetaManagedAgentsAgentUnionParams` from the `agent` request property `allOf` list
- **2026-06-30** `7caa9a75ddbc` — 2 info
  - added `subschema #2` to the `agent/model/id` response property `anyOf` list for the response status `200`
  - added `subschema #2` to the `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/model/id` response property `anyOf` list for the response status `200`
- **2026-06-09** `2336fecb081b` — 1 info
  - added the optional property `deployment_id` to the response with the `200` status
- **2026-06-09** `00259327305f` — 2 info
  - added `subschema #2` to the `agent/model/id` response property `anyOf` list for the response status `200`
  - added `subschema #2` to the `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/model/id` response property `anyOf` list for the response status `200`
- **2026-06-06** `546c704d347b` — 2 breaking, 10 info
  - response property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomTool]/input_schema/required` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `agent/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomTool]/input_schema/required` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - removed `#/components/schemas/BetaManagedAgentsStruct` from the `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomTool]/input_schema/properties` response property `allOf` list for the response status `200`
  - removed `#/components/schemas/BetaManagedAgentsStruct` from the `agent/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomTool]/input_schema/properties` response property `allOf` list for the response status `200`
  - added `subschema #1, subschema #2` to the `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomTool]/input_schema/properties` response property `anyOf` list for the response status `200`
  - added `subschema #1, subschema #2` to the `agent/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomTool]/input_schema/properties` response property `anyOf` list for the response status `200`
  - the response property `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomTool]/input_schema/type` became required for the status `200`
  - the response property `agent/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomTool]/input_schema/type` became required for the status `200`
  - the `type` response property const value `object` was added for the status `200`
  - the `type` response property const value `object` was added for the status `200`
  - removed the `object` enum value from the `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomTool]/input_schema/type` response property for the response status `200`
  - removed the `object` enum value from the `agent/tools/items/oneOf[#/components/schemas/BetaManagedAgentsCustomTool]/input_schema/type` response property for the response status `200`
- **2026-05-28** `f9d488f9290d` — 2 info
  - added `subschema #2` to the `agent/model/id` response property `anyOf` list for the response status `200`
  - added `subschema #2` to the `agent/multiagent/allOf[#/components/schemas/BetaManagedAgentsSessionMultiagent]/oneOf[#/components/schemas/BetaManagedAgentsSessionMultiagentCoordinator]/agents/items/model/id` response property `anyOf` list for the response status `200`
- **2026-05-06** `a4186730f56c` — 2 info
  - added the required property `agent/multiagent` to the response with the `200` status
  - added the required property `outcome_evaluations` to the response with the `200` status
- **2026-04-23** `681182707119` — 1 breaking, 3 info
  - added `#/components/schemas/BetaManagedAgentsMemoryStoreResource` to the `resources/items/` response property `oneOf` list for the response status `200`
  - added `memory_store` discriminator mapping keys to the `resources/items/` request property
  - added `#/components/schemas/BetaManagedAgentsMemoryStoreResourceParam` to the `resources/items/` request property `oneOf` list
  - added `memory_store` discriminator mapping keys to the `resources/items/` response property for the response status `200`
- **2026-04-16** `e0696f59ae07` — 1 info
  - added `subschema #2` to the `agent/model/id` response property `anyOf` list for the response status `200`
- **2026-04-08** `69486316563e` — 1 info
  - endpoint added

---

[Operation](https://skmtc.dev/anthropics/apis/anthropic-api/docs/v1/sessions?beta=true/post.md) · [API](https://skmtc.dev/anthropics/apis/anthropic-api.md) · [Page](https://skmtc.dev/anthropics/apis/anthropic-api/changes/v1/sessions?beta=true/post)