Forbid agentic sync from modifying src/generated/java/ files

Agent-Logs-Url: https://github.com/github/copilot-sdk-java/sessions/38fdf90e-c98a-4df6-8954-3c965bdfb1f8

Co-authored-by: edburns <75821+edburns@users.noreply.github.com>

Author: Copilot

.github/prompts/agentic-merge-reference-impl.prompt.md

@@ -2,6 +2,43 @@
 
 You are an expert Java developer tasked with porting changes from the reference implementation of the Copilot SDK (primarily the .NET implementation) to this Java SDK.
 
+## ❌❌❌ ABSOLUTE PROHIBITION: DO NOT TOUCH GENERATED CODE ❌❌❌
+
+> ### 🚫 THE FILES UNDER `src/generated/java/` ARE FORBIDDEN 🚫
+>
+> **NEVER, UNDER ANY CIRCUMSTANCES, MODIFY ANY FILE IN `src/generated/java/`.**
+>
+> These files are AUTO-GENERATED by `scripts/codegen/java.ts` and MUST NOT be hand-edited.
+> They are regenerated automatically when the `@github/copilot` npm package version is updated.
+>
+> ❌ DO NOT edit `src/generated/java/**/*.java`
+> ❌ DO NOT create new files in `src/generated/java/`
+> ❌ DO NOT delete files from `src/generated/java/`
+> ❌ DO NOT "fix" or "improve" generated code — it will be overwritten
+>
+> **IF ANY CHANGE YOU NEED TO MAKE REQUIRES TOUCHING `src/generated/java/`:**
+>
+> 1. **STOP IMMEDIATELY** — do not make the change
+> 2. **FAIL the agentic sync** — do not attempt to work around this restriction
+> 3. **Push an explanatory commit** with a message such as:
+>    ```
+>    SYNC BLOCKED: Required change needs generated code update
+>
+>    The reference implementation change '<description>' requires updates
+>    to the generated RPC/event types in src/generated/java/. These files
+>    cannot be hand-edited — they must be regenerated.
+>
+>    ACTION REQUIRED: Re-run the update-copilot-dependency.yml workflow
+>    to update the @github/copilot npm package and regenerate the Java
+>    source files before this sync can be completed.
+>    ```
+> 4. **Document in the PR body** which reference implementation changes were blocked and why
+> 5. **Do NOT attempt to work around this restriction** by making equivalent changes elsewhere
+>
+> The correct way to update generated code is:
+> - Trigger the `update-copilot-dependency.yml` workflow with the new `@github/copilot` version
+> - That workflow updates `package.json`, regenerates all files in `src/generated/java/`, and opens a PR
+
 ## ⚠️ IMPORTANT: Java SDK Design Takes Priority
 
 **The current design and architecture of the Java SDK is the priority.** When porting changes from the reference implementation:
@@ -101,7 +138,7 @@ For each change in the reference implementation diff, determine:
 | `dotnet/src/Client.cs`             | `src/main/java/com/github/copilot/sdk/CopilotClient.java` |
 | `dotnet/src/Session.cs`            | `src/main/java/com/github/copilot/sdk/CopilotSession.java` |
 | `dotnet/src/Types.cs`              | `src/main/java/com/github/copilot/sdk/types/*.java`    |
-| `dotnet/src/Generated/*.cs`        | `src/main/java/com/github/copilot/sdk/types/*.java`    |
+| `dotnet/src/Generated/*.cs`        | ❌ **DO NOT TOUCH** `src/generated/java/**` — see top of this file |
 | `dotnet/test/*.cs`                 | `src/test/java/com/github/copilot/sdk/*Test.java`      |
 | `docs/getting-started.md`          | `README.md` and `src/site/markdown/*.md`               |
 | `docs/*.md` (new files)            | `src/site/markdown/*.md` + update `src/site/site.xml`  |
@@ -111,6 +148,10 @@ For each change in the reference implementation diff, determine:
 
 ## Step 5: Apply Changes to Java SDK
 
+> ### ❌❌❌ REMINDER: `src/generated/java/` IS FORBIDDEN ❌❌❌
+> Any change that requires modifying `src/generated/java/` MUST stop the sync.
+> See the **ABSOLUTE PROHIBITION** section at the top of this file for required actions.
+
 When porting changes:
 
 ### ⚠️ Priority: Preserve Java SDK Design
@@ -400,6 +441,7 @@ Before finishing:
 
 ## Checklist
 
+- [ ] ❌ **VERIFIED: No files in `src/generated/java/` were modified** (if any were needed, sync was stopped per ABSOLUTE PROHIBITION above)
 - [ ] New branch created from `main`
 - [ ] Copilot CLI updated to latest version
 - [ ] README.md updated with minimum CLI version requirement
@@ -430,6 +472,7 @@ Before finishing:
 
 ## Notes
 
+- ❌❌❌ **`src/generated/java/` IS FORBIDDEN** — NEVER modify generated files; re-run `update-copilot-dependency.yml` instead ❌❌❌
 - The reference implementation SDK is at: `https://github.com/github/copilot-sdk.git`
 - Primary reference implementation is in `dotnet/` folder
 - This Java SDK targets Java 17+

.github/prompts/coding-agent-merge-reference-impl-instructions.md

@@ -17,3 +17,17 @@ Add the 'reference-impl-sync' label to the existing PR by running this command i
 If after analyzing the reference implementation diff there are no relevant changes to port to the Java SDK,
 push an empty commit with a message explaining why no changes were needed, so the PR reflects
 the analysis outcome. The repository maintainer will close the PR and issue manually.
+
+❌❌❌ ABSOLUTE PROHIBITION ❌❌❌
+
+NEVER MODIFY ANY FILE UNDER src/generated/java/ — THESE FILES ARE AUTO-GENERATED AND FORBIDDEN.
+
+If any change requires modifying src/generated/java/:
+1. STOP IMMEDIATELY — do not make the change
+2. FAIL the sync with an explanatory commit message
+3. Instruct the maintainer to re-run update-copilot-dependency.yml to regenerate these files
+
+See the ABSOLUTE PROHIBITION section in .github/prompts/agentic-merge-reference-impl.prompt.md
+for the full required procedure and commit message template.
+
+❌❌❌ END ABSOLUTE PROHIBITION ❌❌❌