[9.2] [ML][AI Connector] Anthropic Connector: ensure max tokens parameter is passed as expected by service (#241188) (#241208)

# Backport

This will backport the following commits from `main` to `9.2`:
- [[ML][AI Connector] Anthropic Connector: ensure max tokens parameter
is passed as expected by service
(#241188)](#241188)

<!--- Backport version: 9.6.6 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sorenlouv/backport)

<!--BACKPORT [{"author":{"name":"Melissa
Alvarez","email":"[email protected]"},"sourceCommit":{"committedDate":"2025-10-29T21:00:37Z","message":"[ML][AI
Connector] Anthropic Connector: ensure max tokens parameter is passed as
expected by service (#241188)\n\n## Summary\n\nFixes
https://github.com/elastic/kibana/issues/241142\n\nThis is a temporary
workaround for anthropic max_tokens handling until\nthe services
endpoint is updated to reflect the correct structure.\nAnthropic is
unique in that it requires max_tokens to be sent as part of\nthe
task_settings instead of the usual service_settings.\nUntil the services
endpoint is updated to reflect that, there is no way\nfor the form UI to
know where to put max_tokens. This can be removed\nonce that update is
made.\n\n\nhttps://github.com/user-attachments/assets/e89e7fb2-5509-45c6-9f43-deccb0873267\n\n\n###
Checklist\n\nCheck the PR satisfies following conditions. \n\nReviewers
should verify this PR satisfies this list as well.\n\n- [ ] Any text
added follows [EUI's
writing\nguidelines](https://elastic.github.io/eui/#/guidelines/writing),
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functional\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\nwere
updated or added to match the most common scenarios\n- [ ] If a plugin
configuration key changed, check if it needs to be\nallowlisted in the
cloud and added to the
[docker\nlist](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)\n-
[ ] This was checked for breaking HTTP API changes, and any
breaking\nchanges have been approved by the breaking-change committee.
The\n`release_note:breaking` label should be applied in these
situations.\n- [ ] [Flaky
Test\nRunner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1)
was\nused on any tests changed\n- [ ] The PR description includes the
appropriate Release Notes section,\nand the correct `release_note:*`
label is applied per
the\n[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)\n-
[ ] Review the
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Anthropic Connector: ensure max tokens parameter is passed as expected
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Connector] Anthropic Connector: ensure max tokens parameter is passed as
expected by service (#241188)\n\n## Summary\n\nFixes
https://github.com/elastic/kibana/issues/241142\n\nThis is a temporary
workaround for anthropic max_tokens handling until\nthe services
endpoint is updated to reflect the correct structure.\nAnthropic is
unique in that it requires max_tokens to be sent as part of\nthe
task_settings instead of the usual service_settings.\nUntil the services
endpoint is updated to reflect that, there is no way\nfor the form UI to
know where to put max_tokens. This can be removed\nonce that update is
made.\n\n\nhttps://github.com/user-attachments/assets/e89e7fb2-5509-45c6-9f43-deccb0873267\n\n\n###
Checklist\n\nCheck the PR satisfies following conditions. \n\nReviewers
should verify this PR satisfies this list as well.\n\n- [ ] Any text
added follows [EUI's
writing\nguidelines](https://elastic.github.io/eui/#/guidelines/writing),
uses\nsentence case text and includes
[i18n\nsupport](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md)\n-
[
]\n[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)\nwas
added for features that require explanation or tutorials\n- [ ] [Unit or
functional\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\nwere
updated or added to match the most common scenarios\n- [ ] If a plugin
configuration key changed, check if it needs to be\nallowlisted in the
cloud and added to the
[docker\nlist](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)\n-
[ ] This was checked for breaking HTTP API changes, and any
breaking\nchanges have been approved by the breaking-change committee.
The\n`release_note:breaking` label should be applied in these
situations.\n- [ ] [Flaky
Test\nRunner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1)
was\nused on any tests changed\n- [ ] The PR description includes the
appropriate Release Notes section,\nand the correct `release_note:*`
label is applied per
the\n[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)\n-
[ ] Review the
[backport\nguidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)\nand
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Connector] Anthropic Connector: ensure max tokens parameter is passed as
expected by service (#241188)\n\n## Summary\n\nFixes
https://github.com/elastic/kibana/issues/241142\n\nThis is a temporary
workaround for anthropic max_tokens handling until\nthe services
endpoint is updated to reflect the correct structure.\nAnthropic is
unique in that it requires max_tokens to be sent as part of\nthe
task_settings instead of the usual service_settings.\nUntil the services
endpoint is updated to reflect that, there is no way\nfor the form UI to
know where to put max_tokens. This can be removed\nonce that update is
made.\n\n\nhttps://github.com/user-attachments/assets/e89e7fb2-5509-45c6-9f43-deccb0873267\n\n\n###
Checklist\n\nCheck the PR satisfies following conditions. \n\nReviewers
should verify this PR satisfies this list as well.\n\n- [ ] Any text
added follows [EUI's
writing\nguidelines](https://elastic.github.io/eui/#/guidelines/writing),
uses\nsentence case text and includes
[i18n\nsupport](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md)\n-
[
]\n[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)\nwas
added for features that require explanation or tutorials\n- [ ] [Unit or
functional\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\nwere
updated or added to match the most common scenarios\n- [ ] If a plugin
configuration key changed, check if it needs to be\nallowlisted in the
cloud and added to the
[docker\nlist](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)\n-
[ ] This was checked for breaking HTTP API changes, and any
breaking\nchanges have been approved by the breaking-change committee.
The\n`release_note:breaking` label should be applied in these
situations.\n- [ ] [Flaky
Test\nRunner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1)
was\nused on any tests changed\n- [ ] The PR description includes the
appropriate Release Notes section,\nand the correct `release_note:*`
label is applied per
the\n[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)\n-
[ ] Review the
[backport\nguidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)\nand
apply applicable `backport:*`
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BACKPORT-->

---------

Co-authored-by: Melissa Alvarez <[email protected]>

Author: kibanamachine

x-pack/platform/plugins/shared/stack_connectors/server/connector_types/inference/index.ts

@@ -65,7 +65,27 @@ export const getConnectorType = (): SubActionConnectorType<Config, Secrets> => (
   minimumLicenseRequired: 'enterprise' as const,
   preSaveHook: async ({ config, secrets, logger, services, isUpdate }) => {
     const esClient = services.scopedClusterClient.asInternalUser;
+
     try {
+      // NOTE: This is a temporary workaround for anthropic max_tokens handling until the services endpoint is updated to reflect the correct structure.
+      // Anthropic is unique in that it requires max_tokens to be sent as part of the task_settings instead of the usual service_settings.
+      // Until the services endpoint is updated to reflect that, there is no way for the form UI to know where to put max_tokens. This can be removed once that update is made.
+      if (
+        config?.provider === ServiceProviderKeys.anthropic &&
+        // @ts-ignore max_tokens is not defined in the type, but we allow it in the schema
+        config?.providerConfig?.max_tokens
+      ) {
+        // @ts-ignore
+        config.taskTypeConfig = {
+          ...(config.taskTypeConfig ?? {}),
+          // @ts-ignore
+          max_tokens: config.providerConfig.max_tokens,
+        };
+        // This field is unknown to the anthropic service config, so we remove it
+        // @ts-ignore
+        delete config.providerConfig.max_tokens;
+      }
+
       const taskSettings = config?.taskTypeConfig
         ? {
             ...unflattenObject(config?.taskTypeConfig),