chore: add 3.5 release notes and config options (#6428)

* chore: add 3.5 release notes and config options

* docs(plugins): enhance --plugin-repo documentation with usage examples

- Add comprehensive plugin-repo configuration documentation
- Document custom repository setup with practical examples
- Add Option 3 for custom plugin repositories in usage guide
- Include use cases for private repos, air-gapped environments, and development
- Cross-reference between config options and usage guide
- Add note about custom repositories in setup section

* Update content/shared/influxdb3-cli/config-options.md

Co-authored-by: Jason Stirnaman <jstirnaman@influxdata.com>

---------

Co-authored-by: Jason Stirnaman <jstirnaman@influxdata.com>

content/shared/influxdb3-cli/config-options.md

@@ -152,6 +152,7 @@ influxdb3 serve
   - [query-file-limit](#query-file-limit)
 - [Processing Engine](#processing-engine)
   - [plugin-dir](#plugin-dir)
+  - [plugin-repo](#plugin-repo)
   - [virtual-env-location](#virtual-env-location)
   - [package-manager](#package-manager)
 {{% show-in "enterprise" %}}
@@ -1743,6 +1744,7 @@ the following side-effects:
 ### Processing Engine
 
 - [plugin-dir](#plugin-dir)
+- [plugin-repo](#plugin-repo)
 - [virtual-env-location](#virtual-env-location)
 - [package-manager](#package-manager)
 
@@ -1756,6 +1758,42 @@ Specifies the local directory that contains Python plugins and their test files.
 
 ---
 
+#### plugin-repo
+
+Specifies the base URL of the remote repository used when referencing plugins with the `gh:` prefix.
+When you create a trigger with a plugin filename starting with `gh:`, InfluxDB fetches
+the plugin code from this repository URL.
+
+The URL construction automatically handles trailing slashes—both formats work identically:
+- `https://example.com/plugins/` (with trailing slash)
+- `https://example.com/plugins` (without trailing slash)
+
+**Default:** The official InfluxDB 3 plugins repository at `https://raw.githubusercontent.com/influxdata/influxdb3_plugins/main/`
+
+| influxdb3 serve option | Environment variable    |
+| :--------------------- | :---------------------- |
+| `--plugin-repo`        | `INFLUXDB3_PLUGIN_REPO` |
+
+##### Example usage
+
+```bash
+# Use a custom organization repository
+influxdb3 serve \
+  --plugin-dir ~/.plugins \
+  --plugin-repo "https://raw.githubusercontent.com/myorg/influxdb-plugins/main/"
+
+# Use an internal mirror
+influxdb3 serve \
+  --plugin-dir ~/.plugins \
+  --plugin-repo "https://internal.company.com/influxdb-plugins/"
+
+# Set via environment variable
+export INFLUXDB3_PLUGIN_REPO="https://custom-repo.example.com/plugins/"
+influxdb3 serve --plugin-dir ~/.plugins
+```
+
+---
+
 #### virtual-env-location
 
 Specifies the location of the Python virtual environment that the processing

content/shared/influxdb3-plugins/_index.md

@@ -32,7 +32,7 @@ Once you have all the prerequisites in place, follow these steps to implement th
 
 ## Set up the Processing Engine
 
-To activate the Processing Engine, start your {{% product-name %}} server with the `--plugin-dir` flag. This flag tells InfluxDB where to load your plugin files. 
+To activate the Processing Engine, start your {{% product-name %}} server with the `--plugin-dir` flag. This flag tells InfluxDB where to load your plugin files.
 
 {{% code-placeholders "NODE_ID|OBJECT_STORE_TYPE|PLUGIN_DIR" %}}
 
@@ -51,6 +51,14 @@ In the example above, replace the following:
 - {{% code-placeholder-key %}}`OBJECT_STORE_TYPE`{{% /code-placeholder-key %}}: Type of object store (for example, file or s3)
 - {{% code-placeholder-key %}}`PLUGIN_DIR`{{% /code-placeholder-key %}}: Absolute path to the directory where plugin files are stored. Store all plugin files in this directory or its subdirectories.
 
+> [!Note]
+> #### Use custom plugin repositories
+>
+> By default, plugins referenced with the `gh:` prefix are fetched from the official
+> [influxdata/influxdb3_plugins](https://github.com/influxdata/influxdb3_plugins) repository.
+> To use a custom repository, add the `--plugin-repo` flag when starting the server.
+> See [Use a custom plugin repository](#option-3-use-a-custom-plugin-repository) for details.
+
 ### Configure distributed environments
 
 When running {{% product-name %}} in a distributed setup, follow these steps to configure the Processing Engine:
@@ -132,6 +140,42 @@ This approach:
 - Simplifies updates and maintenance
 - Reduces local storage requirements
 
+##### Option 3: Use a custom plugin repository
+
+For organizations that maintain their own plugin repositories or need to use private/internal plugins,
+configure a custom plugin repository URL:
+
+```bash
+# Start the server with a custom plugin repository
+influxdb3 serve \
+  --node-id node0 \
+  --object-store file \
+  --data-dir ~/.influxdb3 \
+  --plugin-dir ~/.plugins \
+  --plugin-repo "https://internal.company.com/influxdb-plugins/"
+```
+
+Then reference plugins from your custom repository using the `gh:` prefix:
+
+```bash
+# Fetches from: https://internal.company.com/influxdb-plugins/myorg/custom_plugin.py
+influxdb3 create trigger \
+  --trigger-spec "every:5m" \
+  --plugin-filename "gh:myorg/custom_plugin.py" \
+  --database my_database \
+  custom_trigger
+```
+
+**Use cases for custom repositories:**
+
+- **Private plugins**: Host proprietary plugins not suitable for public repositories
+- **Air-gapped environments**: Use internal mirrors when external internet access is restricted
+- **Development and staging**: Test plugins from development branches before production deployment
+- **Compliance requirements**: Meet data governance policies requiring internal hosting
+
+The `--plugin-repo` option accepts any HTTP/HTTPS URL that serves raw plugin files.
+See the [plugin-repo configuration option](/influxdb3/version/reference/config-options/#plugin-repo) for more details.
+
 Plugins have various functions such as: 
 
 - Receive plugin-specific arguments (such as written data, call time, or an HTTP request)

content/shared/v3-core-enterprise-release-notes/_index.md

@@ -5,13 +5,55 @@
 > All updates to Core are automatically included in Enterprise.
 > The Enterprise sections below only list updates exclusive to Enterprise.
 
-## v3.4.2 {date="2025-09-11"}
+## v3.5.0 {date="2025-09-30"}
 
 ### Core
 
 #### Features
 
-- No new features in this release
+- **Custom Plugin Repository**: 
+  - Use the `--plugin-repo` option with `influxdb3 serve` to specify custom plugin repositories. This enables loading plugins from personal repos or disabling remote repo access.
+
+#### Bug fixes
+
+- **Database reliability**:
+  - Table index updates now complete atomically before creating new indices, preventing race conditions that could corrupt database state ([#26838](https://github.com/influxdata/influxdb/pull/26838))
+  - Delete operations are now idempotent, preventing errors during object store cleanup ([#26839](https://github.com/influxdata/influxdb/pull/26839))
+- **Write path**: 
+  - Write operations to soft-deleted databases are now rejected, preventing data loss ([#26722](https://github.com/influxdata/influxdb/pull/26722))
+- **Runtime stability**: 
+  - Fixed a compatibility issue that could cause deadlocks for concurrent operations ([#26804](https://github.com/influxdata/influxdb/pull/26804))
+- Other bug fixes and performance improvements
+
+#### Security & Misc
+
+- Sensitive environment variable values are now hidden in CLI output and log messages ([#26837](https://github.com/influxdata/influxdb/pull/26837))
+
+### Enterprise
+
+All Core updates are included in Enterprise. Additional Enterprise-specific features and fixes:
+
+#### Features
+
+- **Cache optimization**: 
+  - Last Value Cache (LVC) and Distinct Value Cache (DVC) now populate on creation and only on query nodes, reducing resource usage on ingest nodes.
+
+#### Bug fixes
+
+- **Object store reliability**: 
+  - Object store operations now use retryable mechanisms with better error handling
+
+#### Operational improvements
+
+- **Compaction optimizations**:
+  - Compaction producer now waits 10 seconds before starting cycles, reducing resource contention during startup
+  - Enhanced scheduling algorithms distribute compaction work more efficiently across available resources
+- **System tables**: 
+  - System tables now provide consistent data across different node modes (ingest, query, compact), enabling better monitoring in multi-node deployments
+
+## v3.4.2 {date="2025-09-11"}
+
+### Core
 
 #### Bug fixes
 
@@ -267,8 +309,8 @@ All Core updates are included in Enterprise. Additional Enterprise-specific feat
 - Tokens can now be granted `CREATE` permission for creating databases
 
 #### Additional Updates
-- Last value caches populate on creation and reload on restart
-- Distinct value caches populate on creation and reload on restart
+- Last value caches reload on restart
+- Distinct value caches reload on restart
 - Other performance improvements
 - Replaces remaining "INFLUXDB_IOX" Dockerfile environment variables with the following:
   - `ENV INFLUXDB3_OBJECT_STORE=file`