MLflow 3.5.0 includes several major features and improvements!

Major Features​

• ⚙️ Job Execution Backend: Introduced a new job execution backend infrastructure for running asynchronous tasks with individual execution pools, job search capabilities, and transient error handling. (#17676, #18012, #18070, #18071, #18112, #18049, @WeichenXu123)
• 🎯 Flexible Prompt Optimization API: Introduced a new flexible API for prompt optimization with support for model switching and the GEPA algorithm, enabling more efficient prompt tuning with fewer rollouts. See the documentation to get started. (#18183, #18031, @TomeHirata)
• 🎨 Enhanced UI Onboarding: Improved in-product onboarding experience with trace quickstart drawer and updated homepage guidance to help users discover MLflow's latest features. (#18098, #18187, @B-Step62)
• 🔐 Security Middleware for Tracking Server: Added a security middleware layer to protect against DNS rebinding, CORS attacks, and other security threats. Read the documentation for configuration details. (#17910, @BenWilson2)

Features​

• [Tracing / Tracking] Add unlink_traces_from_run batch operation (#18316, @harupy)
• [Tracing] Add batch trace link/unlink operations to DatabricksTracingRestStore (#18295, @harupy)
• [Tracking] Claude Code SDK autologging support (#18022, @smoorjani)
• [Tracing] Add support for reading trace configuration from environment variables (#17792, @joelrobin18)
• [Tracking] Mistral tracing improvements (#16370, @joelrobin18)
• [Tracking] Gemini token count tracking (#16248, @joelrobin18)
• [Tracking] Gemini streaming support (#16249, @joelrobin18)
• [Tracking] CrewAI token count tracking with documentation updates (#16373, @joelrobin18)
• [Evaluation] Allow passing empty scorer list for manual result comparison (#18265, @B-Step62)
• [Evaluation] Log assessments to DSPy evaluation traces (#18136, @B-Step62)
• [Evaluation] Add support for trace inputs to built-in scorers (#17943, @BenWilson2)
• [Evaluation] Add synonym handling for built-in scorers (#17980, @BenWilson2)
• [Evaluation] Add span timing tool for Agent Judges (#17948, @BenWilson2)
• [Evaluation] Allow disabling evaluation sample check (#18032, @B-Step62)
• [Evaluation] Reduce verbosity of SIMBA optimizer logs when aligning judges (#17795, @BenWilson2)
• [Evaluation] Add __repr__ method for Judges (#17794, @BenWilson2)
• [Prompts] Add prompt registry support to MLflow webhooks (#17640, @harupy)
• [Prompts] Prompt Registry Chat UI (#17334, @joelrobin18)
• [UI] Delete parent and child runs together (#18052, @joelrobin18)
• [UI] Added move to top, move to bottom for charts (#17742, @joelrobin18)
• [Tracking] Use sampling data for run comparison to improve performance (#17645, @lkuo)
• [Tracking] Add optional 'outputs' column for evaluation dataset records (#17735, @WeichenXu123)

Bug Fixes​

• [Tracing] Fix parent run resolution mechanism for LangChain (#17273, @B-Step62)
• [Tracing] Add client-side retry for get_trace to improve reliability (#18224, @B-Step62)
• [Tracing] Fix OpenTelemetry dual export (#18163, @B-Step62)
• [Tracing] Suppress false warnings from span logging (#18092, #18276, @B-Step62)
• [Tracing] Fix OpenTelemetry resource attributes not propagating correctly (#18019, @xiaosha007)
• [Tracing] Fix DSPy prompt display (#17988, @B-Step62)
• [Tracing] Fix usage aggregation to avoid ancestor duplication (#17921, @TomeHirata)
• [Tracing] Fix double counting in Strands tracing (#17855, @joelrobin18)
• [Tracing] Fix to_predict_fn to handle traces without tags field (#17784, @harupy)
• [Tracing] URL-encode trace tag keys in delete_trace_tag to prevent 404 errors (#18232, @copilot-swe-agent)
• [Tracking] Fix Claude Code autologging inputs not displaying (#17858, @smoorjani)
• [Tracking] Fix runs with 0-valued metrics not appearing in experiment list contour plots (#17916, @WeichenXu123)
• [Tracking] Fix DSPy run display (#18137, @B-Step62)
• [Tracking] Allow list of types in tools JSON Schema for OpenAI autolog (#17908, @fedem96)
• [Tracking] Set tracking URI environment variable for job runner (#18073, @WeichenXu123)
• [Evaluation] Add atomicity to job_start API (#18226, @BenWilson2)
• [Evaluation] Fix trace ingest for outputs in merge_records() API (#18047, @BenWilson2)
• [Evaluation] Fix judge regression (#18039, @B-Step62)
• [Evaluation] Fix judges to use non-empty user messages for Anthropic model compatibility (#17935, @dbczumar)
• [Evaluation] Fix endpoints error in judge (#18048, @joelrobin18)
• [Model Registry] Fix creating model versions from non-Databricks tracking to Databricks Unity Catalog registry (#18244, @austinwarner-8451)
• [Model Registry] Fix registry URI instantiation for artifact download (#17982, @arpitjasa-db)
• [Model Registry] Include original error details in Unity Catalog model copy failure messages (#17997, @harupy)
• [Model Registry] Fix webhook delivery to exit early for FileStore instances (#18015, @copilot-swe-agent)
• [Prompts] Fix error suppression during prompt alias resolution when allow_missing is set (#17541, @mr-brobot)
• [UI] General UI improvements (#18281, @joelrobin18)
• [Models] Fix dataset issue (#18081, @joelrobin18)
• [Models] Forward dataset name and digest to PolarsDataset's to_evaluation_dataset method (#17886, @sadelcarpio)
• [Build] Fix mlflow server exiting immediately when optional huey package is missing (#18016, @harupy)
• [Scoring] Fix chat completion arguments (#18248, @aravind-segu)

Documentation Updates​

• [Docs] Add self-hosted documentation support (#17986, @B-Step62)
• [Docs] Add GitHub feature requests section to GenAI documentation (#18342, @TomeHirata)
• [Docs] Update Claude Code SDK tracing documentation (#18026, @smoorjani)
• [Docs] Add documentation for Analyze Experiment MCP/CLI command (#17978, @nsthorat)
• [Docs] Add deprecation notice for custom prompt judge (#18287, @smoorjani)
• [Docs] Overhaul scorer documentation (#17930, @B-Step62)
• [Docs] Add default optimizer documentation (#17814, @BenWilson2)
• [Docs] Update TypeScript SDK contribution documentation (#17995, @joelrobin18)
• [Docs] Fix Postgres 18+ mount path in documentation (#18192, @soyun11)
• [Docs] Fix typo: correct variable name from max_few_show_examples to max_few_shot_examples (#18246, @srinathmkce)
• [Docs] Replace single quotes with double quotes for Windows compatibility (#18266, @PavithraNelluri)
• [Docs] Fix typo in model registry documentation (#18038, @EddieMG)

For a comprehensive list of changes, see the release change log, and check out the latest documentation on mlflow.org.