--- title: "Changes to Create an agent session" method: POST path: "/agents/sessions" --- # Changes to Create an agent session `POST /agents/sessions` > Every recorded change to this operation, newest first. ## Timeline Changed in 21 of 554 revisions. - **2026-10-30** `f13a1920916a`: 7 info - **2026-10-29** `5029b1cd1a90`: 7 info - **2026-10-28** `584627423036`: 7 info - **2026-10-23** `3af3b5fec3f6`: 6 breaking, 8 info - **2026-10-16** `909d15009c82`: 1 info - **2026-10-16** `bd21bf914a07`: 7 warning - **2026-10-08** `c686bf249e4c`: 1 breaking, 10 warning, 1 info - **2026-10-08** `4ce25559b07f`: 1 info - **2026-10-08** `d747b8568df2`: 7 info - **2026-10-06** `9e0991b213ec`: 5 warning - **2026-10-06** `9aaaaa5d9c73`: 1 info - **2026-10-02** `c7e20d7679dc`: 15 warning - **2026-10-01** `e3373b531836`: 1 breaking - **2026-09-29** `1c3e85fd629d`: 14 breaking, 24 info - **2026-09-29** `977c132ac3d0`: 7 info - **2026-09-27** `4b75527da17b`: 5 warning - **2026-09-25** `82d76d5c86cf`: 6 warning, 1 info - **2026-09-25** `e0550bdbb545`: 5 warning - **2026-09-19** `d4e842399c2e`: 1 breaking, 1 info - **2026-09-11** `8c3c08961f62`: 5 warning - **2026-09-10** `f2dae1a9aced`: 1 info ## Changes - **2026-10-30** `f13a1920916a`: 7 info - added the new optional request property `review` - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/review` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/review` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/review` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/review` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/review` to the response with the `201` status (media type: text/event-stream) - added the optional property `review` to the response with the `201` status (media type: application/json) - **2026-10-29** `5029b1cd1a90`: 7 info - added the new optional request property `agent/experimental` - added the optional property `agent/experimental` to the response with the `201` status (media type: application/json) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/agent/experimental` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/agent/experimental` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/agent/experimental` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/agent/experimental` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/agent/experimental` to the response with the `201` status (media type: text/event-stream) - **2026-10-28** `584627423036`: 7 info - added the new optional request property `agent/compaction` - added the optional property `agent/compaction` to the response with the `201` status (media type: application/json) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/agent/compaction` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/agent/compaction` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/agent/compaction` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/agent/compaction` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/agent/compaction` to the response with the `201` status (media type: text/event-stream) - **2026-10-23** `3af3b5fec3f6`: 6 breaking, 8 info - added `#/components/schemas/AgentToolResourceAutomations` to the `agent/tools/items/` response property `oneOf` list for the response status `201` (media type: application/json) - added `#/components/schemas/AgentToolResourceAutomations` to the `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/agent/tools/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/AgentToolResourceAutomations` to the `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/agent/tools/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/AgentToolResourceAutomations` to the `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/agent/tools/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/AgentToolResourceAutomations` to the `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/agent/tools/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/AgentToolResourceAutomations` to the `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/agent/tools/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `automations` discriminator mapping keys to the `agent/tools/items/` request property - added `#/components/schemas/AgentToolConfigParamAutomations` to the `agent/tools/items/` request property `oneOf` list - added `automations` discriminator mapping keys to the `agent/tools/items/` response property for the response status `201` (media type: application/json) - added `automations` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/agent/tools/items/` response property for the response status `201` (media type: text/event-stream) - added `automations` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/agent/tools/items/` response property for the response status `201` (media type: text/event-stream) - added `automations` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/agent/tools/items/` response property for the response status `201` (media type: text/event-stream) - added `automations` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/agent/tools/items/` response property for the response status `201` (media type: text/event-stream) - added `automations` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/agent/tools/items/` response property for the response status `201` (media type: text/event-stream) - **2026-10-16** `909d15009c82`: 1 info - added the new `ultrafast` enum value to the request property `agent/service_tier/anyOf[#/components/schemas/ServiceTierParam]/` - **2026-10-16** `bd21bf914a07`: 7 warning - removed the request property `spend_control` - removed the optional property `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/spend_control` from the response with the `201` status (media type: text/event-stream) - removed the optional property `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/spend_control` from the response with the `201` status (media type: text/event-stream) - removed the optional property `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/spend_control` from the response with the `201` status (media type: text/event-stream) - removed the optional property `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/spend_control` from the response with the `201` status (media type: text/event-stream) - removed the optional property `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/spend_control` from the response with the `201` status (media type: text/event-stream) - removed the optional property `spend_control` from the response with the `201` status (media type: application/json) - **2026-10-08** `c686bf249e4c`: 1 breaking, 10 warning, 1 info - added `#/components/schemas/SessionEventAgentSessionEnvironmentSuspended, #/components/schemas/SessionEventAgentSessionEnvironmentExpired` to the response body `oneOf` list for the response status `201` - added the new `expired` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionEnvironmentConnected]/environment/status` response property for the response status `201` - added the new `expired` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionEnvironmentDisconnected]/environment/status` response property for the response status `201` - added the new `expired` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionEnvironmentFailed]/environment/status` response property for the response status `201` - added the new `expired` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionEnvironmentPending]/environment/status` response property for the response status `201` - added the new `expired` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionEnvironmentReady]/environment/status` response property for the response status `201` - added the new `suspended` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionEnvironmentConnected]/environment/status` response property for the response status `201` - added the new `suspended` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionEnvironmentDisconnected]/environment/status` response property for the response status `201` - added the new `suspended` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionEnvironmentFailed]/environment/status` response property for the response status `201` - added the new `suspended` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionEnvironmentPending]/environment/status` response property for the response status `201` - added the new `suspended` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionEnvironmentReady]/environment/status` response property for the response status `201` - added `agent.session.environment.suspended, agent.session.environment.expired` mapping keys to the response discriminator for the response status `201` - **2026-10-08** `4ce25559b07f`: 1 info - added the new optional request property `environment/oneOf[#/components/schemas/EnvironmentParamOpenaiHosted]/environment_id` - **2026-10-08** `d747b8568df2`: 7 info - added the new optional request property `spend_control` - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/spend_control` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/spend_control` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/spend_control` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/spend_control` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/spend_control` to the response with the `201` status (media type: text/event-stream) - added the optional property `spend_control` to the response with the `201` status (media type: application/json) - **2026-10-06** `9e0991b213ec`: 5 warning - added the new `billing_not_active` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCancelled]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `billing_not_active` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCompleted]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `billing_not_active` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCreated]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `billing_not_active` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnFailed]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `billing_not_active` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnInProgress]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - **2026-10-06** `9aaaaa5d9c73`: 1 info - added the non-success response with the status `429` - **2026-10-02** `c7e20d7679dc`: 15 warning - added the new `organization_spend_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCancelled]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `organization_spend_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCompleted]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `organization_spend_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCreated]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `organization_spend_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnFailed]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `organization_spend_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnInProgress]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `organization_usage_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCancelled]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `organization_usage_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCompleted]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `organization_usage_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCreated]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `organization_usage_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnFailed]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `organization_usage_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnInProgress]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `project_spend_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCancelled]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `project_spend_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCompleted]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `project_spend_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCreated]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `project_spend_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnFailed]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `project_spend_limit_exceeded` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnInProgress]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - **2026-10-01** `e3373b531836`: 1 breaking - removed the enum value `ultrafast` of the request property `agent/service_tier/anyOf[#/components/schemas/ServiceTierParam]/` - **2026-09-29** `1c3e85fd629d`: 14 breaking, 24 info - added `#/components/schemas/AgentToolResourceComputerUse` to the `agent/tools/items/` response property `oneOf` list for the response status `201` (media type: application/json) - added `#/components/schemas/AgentToolResourceComputerUse` to the `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/agent/tools/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/AgentToolResourceComputerUse` to the `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/agent/tools/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/AgentToolResourceComputerUse` to the `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/agent/tools/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/AgentToolResourceComputerUse` to the `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/agent/tools/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/AgentToolResourceComputerUse` to the `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/agent/tools/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/ComputerUseCallItemResource, #/components/schemas/BrowserAuthenticationRequestItemResource` to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnItemDone]/item` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/ComputerUseCallItemResource, #/components/schemas/BrowserAuthenticationRequestItemResource, #/components/schemas/ComputerUseApprovalRequestResultItemResource` to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnItemAdded]/item` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/SessionRequiredActionResourceComputerUseApprovalRequest` to the `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/required_actions/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/SessionRequiredActionResourceComputerUseApprovalRequest` to the `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/required_actions/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/SessionRequiredActionResourceComputerUseApprovalRequest` to the `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/required_actions/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/SessionRequiredActionResourceComputerUseApprovalRequest` to the `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/required_actions/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/SessionRequiredActionResourceComputerUseApprovalRequest` to the `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/required_actions/items/` response property `oneOf` list for the response status `201` (media type: text/event-stream) - added `#/components/schemas/SessionRequiredActionResourceComputerUseApprovalRequest` to the `required_actions/items/` response property `oneOf` list for the response status `201` (media type: application/json) - added the new optional request property `environment/oneOf[#/components/schemas/EnvironmentParamOpenaiHosted]/desktop` - added the new optional request property `environment/oneOf[#/components/schemas/EnvironmentParamOpenaiHosted]/network/anyOf[#/components/schemas/NetworkPolicyParam]/blocked_domains` - added `computer_use` discriminator mapping keys to the `agent/tools/items/` request property - added `#/components/schemas/AgentToolConfigParamComputerUse` to the `agent/tools/items/` request property `oneOf` list - added `computer_use` discriminator mapping keys to the `agent/tools/items/` response property for the response status `201` (media type: application/json) - added `computer_use` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/agent/tools/items/` response property for the response status `201` (media type: text/event-stream) - added `computer_use` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/agent/tools/items/` response property for the response status `201` (media type: text/event-stream) - added `computer_use` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/agent/tools/items/` response property for the response status `201` (media type: text/event-stream) - added `computer_use` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/agent/tools/items/` response property for the response status `201` (media type: text/event-stream) - added `computer_use` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/agent/tools/items/` response property for the response status `201` (media type: text/event-stream) - added `computer_use_approval_request` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/required_actions/items/` response property for the response status `201` (media type: text/event-stream) - added `computer_use_approval_request` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/required_actions/items/` response property for the response status `201` (media type: text/event-stream) - added `computer_use_approval_request` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/required_actions/items/` response property for the response status `201` (media type: text/event-stream) - added `computer_use_approval_request` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/required_actions/items/` response property for the response status `201` (media type: text/event-stream) - added `computer_use_approval_request` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/required_actions/items/` response property for the response status `201` (media type: text/event-stream) - added `computer_use_approval_request` discriminator mapping keys to the `required_actions/items/` response property for the response status `201` (media type: application/json) - added `computer_use_call, computer_use_approval_request` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnItemDone]/item` response property for the response status `201` (media type: text/event-stream) - added `computer_use_call, computer_use_approval_request, computer_use_approval_request_result` discriminator mapping keys to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnItemAdded]/item` response property for the response status `201` (media type: text/event-stream) - added the required property `environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/desktop` to the response with the `201` status (media type: application/json) - added the required property `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/desktop` to the response with the `201` status (media type: text/event-stream) - added the required property `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/desktop` to the response with the `201` status (media type: text/event-stream) - added the required property `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/desktop` to the response with the `201` status (media type: text/event-stream) - added the required property `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/desktop` to the response with the `201` status (media type: text/event-stream) - added the required property `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/desktop` to the response with the `201` status (media type: text/event-stream) - **2026-09-29** `977c132ac3d0`: 7 info - added the new optional request property `environment/oneOf[#/components/schemas/EnvironmentParamOpenaiHosted]/container_size` - added the optional property `environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/container_size` to the response with the `201` status (media type: application/json) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/container_size` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/container_size` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/container_size` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/container_size` to the response with the `201` status (media type: text/event-stream) - added the optional property `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/environment/oneOf[#/components/schemas/EnvironmentResourceOpenaiHosted]/container_size` to the response with the `201` status (media type: text/event-stream) - **2026-09-27** `4b75527da17b`: 5 warning - added the new `flex_unavailable` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCancelled]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `flex_unavailable` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCompleted]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `flex_unavailable` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCreated]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `flex_unavailable` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnFailed]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `flex_unavailable` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnInProgress]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - **2026-09-25** `82d76d5c86cf`: 6 warning, 1 info - added the new `ultrafast` enum value to the `agent/service_tier` response property for the response status `201` (media type: application/json) - added the new `ultrafast` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionCreated]/session/agent/service_tier` response property for the response status `201` (media type: text/event-stream) - added the new `ultrafast` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionFailed]/session/agent/service_tier` response property for the response status `201` (media type: text/event-stream) - added the new `ultrafast` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionIdle]/session/agent/service_tier` response property for the response status `201` (media type: text/event-stream) - added the new `ultrafast` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionInProgress]/session/agent/service_tier` response property for the response status `201` (media type: text/event-stream) - added the new `ultrafast` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionRequiresAction]/session/agent/service_tier` response property for the response status `201` (media type: text/event-stream) - added the new `ultrafast` enum value to the request property `agent/service_tier/anyOf[#/components/schemas/ServiceTierParam]/` - **2026-09-25** `e0550bdbb545`: 5 warning - added the new `misalignment_policy_violation` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCancelled]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `misalignment_policy_violation` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCompleted]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `misalignment_policy_violation` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCreated]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `misalignment_policy_violation` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnFailed]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `misalignment_policy_violation` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnInProgress]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - **2026-09-19** `d4e842399c2e`: 1 breaking, 1 info - added `#/components/schemas/SessionEventAgentSessionEnvironmentReset` to the response body `oneOf` list for the response status `201` - added `agent.session.environment.reset` mapping keys to the response discriminator for the response status `201` - **2026-09-11** `8c3c08961f62`: 5 warning - added the new `credit_balance_exhausted` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCancelled]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `credit_balance_exhausted` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCompleted]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `credit_balance_exhausted` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnCreated]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `credit_balance_exhausted` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnFailed]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - added the new `credit_balance_exhausted` enum value to the `oneOf[#/components/schemas/SessionEventAgentSessionTurnInProgress]/turn/error/anyOf[#/components/schemas/SessionTurnErrorResource]/code` response property for the response status `201` - **2026-09-10** `f2dae1a9aced`: 1 info - endpoint added --- [Operation](https://skmtc.dev/openai/apis/openai-api-4/docs/agents/sessions/post.md) - [API](https://skmtc.dev/openai/apis/openai-api-4.md) - [Page](https://skmtc.dev/openai/apis/openai-api-4/changes/agents/sessions/post)