Drop support for platform version 2025.1 (#9033)

This also adds a skill for removing versions in the future.

Author: helin24

.agents/skills/remove-platform-version/SKILL.md

@@ -0,0 +1,50 @@
+---
+name: remove-platform-version
+description: Remove support for an older IntelliJ Platform / Android Studio version from the project and clean up obsolete code, baselines, and CI configurations.
+---
+
+# Skill: Remove Platform Version Support
+
+You are tasked with removing support for an older IntelliJ Platform or Android Studio version (e.g., dropping support for `2025.1` / build `251` and raising the lower bound to `2025.2` / build `252`).
+
+## Objective
+Systematically update compatibility ranges, clean up CI verification loops and baseline files, identify and remove obsolete compatibility code or TODOs, check repository issues, and update documentation.
+
+---
+
+## Workflow Instructions
+
+### 1. Establish Baseline & Identify Target Version
+- Identify the build number being removed (e.g., `251` for `2025.1`) and the new lower bound (e.g., `252` for `2025.2`).
+- Run `./gradlew testClasses` to ensure the project compiles before making changes.
+
+### 2. Update Compatibility Lower Bound (`gradle.properties`)
+- Open `gradle.properties`.
+- Update `sinceBuild=<version>` to the new lower bound build number (e.g., change `sinceBuild=251` to `sinceBuild=252`).
+
+### 3. Update CI Verification Script (`tool/github.sh`)
+- Open `tool/github.sh`.
+- Locate the `VERIFY_BOT` verification loop (`for version in ...; do`).
+- Remove the dropped version number from the list so that `./gradlew verifyPlugin` is only run against active versions in the compatibility range.
+
+### 4. Remove Obsolete Verifier Baseline (`tool/baseline/`)
+- Check `tool/baseline/<version>/` for the removed version directory.
+- Remove the directory and baseline file (e.g., using `git rm -r tool/baseline/<version>`) so baseline update scripts (`tool/update_baselines.sh`) do not attempt to verify unsupported versions.
+
+### 5. Search & Remove Obsolete Code and TODOs
+- **Search Codebase:** Grep `src/` for references to the removed build number or version string (e.g., `251`, `2025.1`).
+- **Check Version Checks:** Look for version-specific branches or workarounds (such as in `DartPluginVersion.java` or UI compatibility shims) that check for the removed version and simplify or remove dead code paths.
+- **Check TODOs:** Look for comments like `TODO: remove when dropping support for <version>` or similar workarounds that can now be cleaned up.
+
+### 6. Search Repository Issues
+- Search repository issues (via GitHub issue search or issue tracker) for issues related to dropping or moving off the removed version (e.g., `repo:flutter/flutter-intellij <version>` or platform compatibility issues).
+- Check if any open issues or tracked technical debt items specify code deletions or cleanup steps upon dropping support for that version, and implement any applicable cleanups.
+
+### 7. Update Changelog
+- **`CHANGELOG.md`:** Under the `### Removed` section, add an entry documenting the removal (e.g., `- Support for platform version 2025.1.`).
+- **Note:** Do not modify `docs/building.md`. Its version examples are illustrative and should not be updated when removing a platform version.
+
+### 8. Verify & Validate
+- Run `./gradlew testClasses` to verify compilation.
+- Run `./gradlew test` to verify unit tests pass.
+- Run `./gradlew verifyPlugin` to verify that plugin verification succeeds against the new compatibility range.

.gemini/styleguide.md

@@ -13,8 +13,7 @@ enforce standard modern Java/Kotlin coding conventions, but strictly police the
     - `[NIT]`: Idiomatic improvements or minor naming suggestions.
 - **Focus:** Prioritize logic, performance on the UI thread, and architectural consistency.
 - **No Empty Praise:** Do not leave "Looks good" or "Nice change" comments. If there are no issues, leave no comments.
-- **Copyright Headers:** Ensure all new files have a proper copyright header (e.g., `Copyright 2026 The Chromium Authors`). Flag any missing
-  headers as `[MUST-FIX]`.
+- **Copyright Headers:** Ensure all new source code files (`.java`, `.kt`, `.dart`, `.sh`) have a proper copyright header (e.g., `Copyright 2026 The Chromium Authors`). Do NOT require copyright headers on documentation, markdown (`.md`), YAML, JSON, or agent skill documents (`SKILL.md`). Flag any missing headers on source code files as `[MUST-FIX]`.
 
 ## 2. IntelliJ Platform Best Practices
 

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Changed
 
 ### Removed
+- Support for platform version 2025.1.
 
 ### Fixed
 

README.md

@@ -92,6 +92,7 @@ These skills are located in the [.agents/skills/](.agents/skills/) directory. Th
 
 ### Available Workspace Skills:
 * **[Code Review](.agents/skills/code-review/SKILL.md):** Performs a pedantic, multi-perspective code review (covering logic, correctness, resource safety, design, and styleguide compliance) on your uncommitted changes.
+* **[Remove Platform Version](.agents/skills/remove-platform-version/SKILL.md):** Remove support for an older IntelliJ Platform / Android Studio version from the project and clean up obsolete code, baselines, and CI configurations.
 
 ### How to use:
 Tell your AI assistant to run the desired skill (e.g. by typing `/code-review` or asking *"Run the code-review skill on my changes"*). The agent will automatically find, load, and follow the instructions in the corresponding `SKILL.md` file.

docs/building.md

@@ -67,7 +67,7 @@ $ gcloud storage cp <path-to-archive> gs://flutter_infra_release/flutter/intelli
 
 (The below is a summary of an internal doc on our strategy for version management.)
 
-The main branch intends to support multiple IDEA platform versions (e.g. currently, 2025.1 to 2025.3). This simplifies
+The main branch intends to support multiple IDEA platform versions (e.g. 2025.1 to 2025.3). This simplifies
 development as only one plugin is typically built and released from main.
 
 However, there may be times when we need different builds for different versions of the IDEA platform; for example, if we introduce a

gradle.properties

@@ -9,7 +9,7 @@
 androidStudioVersion=2026.1.2.8
 dartPluginVersion= 505.0.0
 # Also update the versions for verify checks in tool/github.sh.
-sinceBuild=251
+sinceBuild=252
 untilBuild=262.*
 javaVersion=21
 kotlin.stdlib.default.dependency=false