Fabric Weekly

2026-W39

Sep 21, 2026 – Sep 27, 2026 · 6 articles · 0 low-priority · latest →

AI Readiness · 3

Fabric RLM: Why Harness Matters

fabric.guru Sep 27, 2026 3/5 · Tier B AI ReadinessPySpark deep-dive

<p><strong>Fabric-RLM</strong> improves deterministic tasks by giving a language model an executable Python workspace, a limited turn loop, and an output contract. Instead of asking the model to reason directly from token patterns, the harness lets it construct a list, run code, inspect the result, and submit a typed answer.</p><p>Across nine small and midsize models, only one answered the weekday-letter question correctly without the harness, while all nine succeeded through Fabric-RLM. The result demonstrates tool-assisted verification rather than increased model knowledge; it does not establish reliability for open-ended generation or complex data work.</p>

Measured model comparison demonstrates how executable tools and guardrails improve deterministic data tasks, though the example is intentionally simple.

Introducing Fabric-RLM

fabric.guru Sep 25, 2026 4/5 · Tier A AI ReadinessAPI AutomationData Quality deep-dive

<p><strong>Fabric-RLM</strong> runs recursive language-model tasks beside Fabric data instead of placing entire files into a prompt. The model writes Python, executes it in the notebook environment, inspects results, repairs failures, and returns only outputs matching a typed contract and optional validators.</p><p>Inputs can include Lakehouse files, Delta tables, and semantic models; skills provide reusable procedures for exploration, Excel, PDFs, Delta, and semantic-model work. Each run records generated code, outputs, errors, tokens, timings, and validation repairs, enabling inspection and replay.</p><p>A 140 MB IMF CSV containing 1.57 million rows was processed with DuckDB and openpyxl in 78 seconds, producing a validated workbook. The approach still depends on model-generated code, notebook execution limits, validator quality, and model-endpoint or external-model costs.</p>

Concrete Fabric-native RLM implementation includes measured performance, validation, cost comparison, and operational traceability.

Where we stand on AI and DAX in 2026

SQLBI Sep 22, 2026 2/5 · Tier B AI ReadinessSemantic Model opinion

<p>AI-generated DAX has become more useful in 2026, particularly for drafting measures, transforming models, and handling longer development tasks. The productivity gain is strongest when the request clearly states business intent and the developer can inspect the generated semantics.</p><p>AI still does not reliably resolve filter context, data-model design, edge cases, or performance without validation. The article is primarily an opinion and training-position update rather than a Fabric feature or measured production study.</p>

The opinion reports improving AI-generated DAX but emphasizes human validation, modeling judgment, and performance review.

Governance · 1

On-premises data gateway September 2026 release

Fabric Updates Sep 25, 2026 2/5 · Tier B Governance release-notes

<p>On-premises data gateway version 3000.334 introduces <strong>soft delete</strong>: deleted gateways are retained for 30 days and can be recovered, reducing disruption from accidental administrative deletion.</p><p>The release also updates the embedded Log4j library, addresses CVE-2026-18401, improves Windows Server 2016 sign-in and configurator accessibility, and aligns gateway execution with the September 2026 Power BI Desktop release. Most other changes are maintenance and security updates rather than new Fabric data capabilities.</p>

Gateway soft delete adds operational recovery, while the remaining release is mainly security, compatibility, and patch maintenance.

Report Authoring · 1

Improvements To Power Query Integration In Power BI Report Builder

Crossjoin Sep 27, 2026 2/5 · Tier B Report AuthoringGovernance announcement

<p><strong>Power BI Report Builder</strong> now presents Power Query datasets with a dedicated custom-property view. The view exposes the dataset's M code, configured parameters, and the ID of its Fabric cloud connection.</p><p>Copying the connection ID and searching for it in <strong>Manage Connections and Gateways</strong> makes it easier to locate the precise connection, edit it, or refresh credentials. The change improves supportability but does not introduce a new query engine or materially change report execution behavior.</p>

Useful Report Builder usability improvement exposes Power Query connection identifiers, but scope is narrow and operationally focused.

Semantic Model · 1

The hidden complexity of a daily average in DAX

SQLBI Sep 21, 2026 4/5 · Tier A Semantic Model deep-dive

<p>A daily average is not a single business definition. <strong>AVERAGEX</strong> excludes blank measure results but includes zeros, so averaging over visible dates can silently calculate an average over selling days rather than calendar days.</p><p>Calendar-day averages require a denominator that includes dates without sales, while the date range must represent the actual observation period. A calendar extending beyond transaction history understates results, and transaction first and last dates are only proxies unless data availability is known.</p><p>The article uses AI to draft measures and validation queries, but the important control remains testing filter direction, blank handling, date boundaries, and edge cases against explicit business requirements.</p>

The article exposes how blanks, calendar scope, and data-availability boundaries change daily-average DAX results.