docs: document lint warnings and upload sanitization for empty dashboard filters

Author: mintlify[bot]

guides/cli/how-to-use-lightdash-lint.mdx

@@ -53,6 +53,26 @@ Example output:
 Found 1 error in 1 file
 ```
 
+## Errors vs. warnings
+
+`lightdash lint` reports two severities:
+
+- **Errors** (red `✗`) — schema validation failures. These cause the command to exit with a non-zero status, so they fail CI.
+- **Warnings** (yellow `⚠`) — non-fatal issues that don't block deployment but signal a configuration that's likely to behave unexpectedly. Warnings do **not** affect the exit code.
+
+### Malformed empty dashboard filters
+
+Dashboard YAML can include filters that are active (`disabled: false`) but have no values (`values: []` or `values: ~`) on an operator that requires values (for example, `equals` or `greaterThan`). These filters look empty in the UI but silently override chart-level filters at runtime.
+
+`lightdash lint` flags them as warnings so you can find and fix them in your YAML:
+
+```
+⚠ ./lightdash/dashboards/revenue.yml
+  filters.dimensions[0]: dashboard filter is active but has no values — it will override chart filters at runtime
+```
+
+To resolve the warning, either remove the filter, set `disabled: true`, or provide values. When you next run `lightdash upload`, the CLI also strips these filters from the payload automatically and prints a warning listing which dashboards were affected.
+
 ### Verbose output
 
 Use `--verbose` to see all validated files, including those that passed:

references/lightdash-cli.mdx

@@ -699,6 +699,10 @@ Uploads charts and dashboards that you've made changes to from the `lightdash/`
 
 If there have been changes made to a chart or dashboard in the application that is being uploaded from code, `lightdash upload` will overwrite the changes.
 
+<Note>
+`lightdash upload` automatically drops malformed empty dashboard filters (active filters with no values on operators that require values) from the payload before sending it to the API. When this happens, the CLI prints a warning listing the affected dashboards and recommends running [`lightdash lint`](/references/lightdash-cli#lightdash-lint) to locate the offending filters in your YAML.
+</Note>
+
 **Options:**
 
 - `--force`
@@ -984,6 +988,15 @@ Output results in SARIF JSON format (useful for CI/CD integration):
 lightdash lint --format json
 ```
 
+**Errors and warnings:**
+
+Lint results are reported at two severities:
+
+- **Errors** (`✗`, red) — schema validation failures. The command exits with a non-zero status, failing CI.
+- **Warnings** (`⚠`, yellow) — non-fatal issues like malformed empty dashboard filters (active filters with no values on operators that require them). Warnings don't change the exit code.
+
+See [How to use lightdash lint](/guides/cli/how-to-use-lightdash-lint#errors-vs-warnings) for details.
+
 ### `lightdash pre-aggregate-audit`
 
 Reports pre-aggregate hit/miss coverage for one dashboard or every dashboard in the project. Use it to find gaps in your pre-aggregate YAML or to gate CI on dashboard coverage.