New Features
* #3574519 Fix the tag-release to work on linux
* #3575594 Add css to make the mdxeditor slightly taller

Tasks
* #3584421 Add OverridableFunctionCallInterface to support per-instance context definition overrides on function call plugins
* #3584415 Update full_patch_test docs for 1.3.x: cover guardrails and field widget actions
* #3542552 Allow link in allowedTypes
* #3582364 Add documentation for the Text Chunker service
* #3579480 Add CI job to validate MkDocs documentation formatting
* #3582367 Add documentation for the Guardrails system
* #3582366 Add documentation for PromptJsonDecoder and PromptCodeBlockExtractor services
* #3577970 Dispatch JS event when DeepChat completes agent calls
* #3581662 Add cshs widget support to ClassificationOptionsSelect FieldWidgetAction
* #3583725 Move the FJS skill and prepare for codex, claude etc. in gitignore
* #3545551 Put documentation through AI to check for grammar
* #3582361 Add documentation for the Tools Library form element
* #3566566 Release 1.2.6 and 1.1.9, and update documentation
* #3582359 Fix broken links, dead nav entries, duplicate YAML keys, and orphaned pages in documentation
* #3491351 Add schema validation tests ai.settings
* #3572378 Fix Markdown for Communicating Releases
* #3566924 Add AI core release managers to MAINTAINERS.txt
* #3582577 Remove duplicate entries from .cspell-project-words.txt
* #3582363 Add documentation for the Tokenizer service

Bugs
* #3575592 Tools Explorer: force_value limit is only the first character
* #3578417 AI Automators uninstall leaves ai_automator_status field and related configuration behind
* #3582743 Set temp directory in tokenizer
* #3584344 The handleApiException signature change from Exception to Throwable breaks downstream providers (e.g. Anthropic) that override this method.
* #3573429 Processing automators does not catch all errors
* #3579079 Restrict Topic guardrail silently bypassed due to case-sensitive topic matching
* #3574611 Forms are broken when automators or FWA are not configurable
* #3582074 AssertionError: Cannot load the "key" entity with NULL ID
* #3547797 AI Assistant CKEditor button has regressed
* #3583785 Fix: Guardrail and Guardrail Set config entities have incomplete config schema
* #3583705 AiProviderConfiguration form element doesn't work in nested forms with subform states
* #3578846 AiGuardrailSet does not declare config dependencies on its referenced guardrails
* #3555856 AI Chatbot blocks fail to render: Uninitialized $userMessage property in AiAssistantApiRunner
* #3577813 AI Chatbot block crashes entire site when placed without configured AI Assistant entity
* #3574181 AI Assistant to AI Agents required fields mismatch
* #3582954 Array to string conversion warning in AiApiExplorerPluginBase::addProviderCodeExample() when configuration contains arrays
* #3570159 Error 404 when trying to access ‘Submodules > AI Logging’

Contributors:
rob_e, marcus_johansson, abhisekmazumdar, ahmad khader, merilainen, cadence96, annmarysruthy, fago, a.dmitriiev, ajv009, jan kellermann, avinash.jha, shivamsen_12579, petar_basic, harivansh, jibran, breidert, robloach, bbruno, dany.almeida.kairouz, b_sharpe, sirclickalot, kelly.m.jacobs, divya.sejekan, tushar1, erichomanchuk, brtamas, ronraney, dan2k3k4, nikro, joshua1234511, jatingupta40, revathi.b, bircher, scott falconer, kristen pol, arianraeesi, hrishikesh-dalal