Address very important comment by copilot.

@Copilot wrote:

> This file is runtime-imported by weekly-reference-impl-sync.lock.yml as the agent prompt, but its content is written as documentation rather than imperative agent instructions (e.g., it doesn’t tell the agent to read .lastmerge, clone, compare commits, and must call a safe-output tool). As a result, the agentic workflow may fail or behave unpredictably. Please restore the prior imperative, step-by-step instruction style (like the deleted weekly-upstream-sync.md), updated to the new reference-impl terminology, and ensure it explicitly requires calling create-issue/close-issue/noop as appropriate.

Author: edburns

.github/workflows/weekly-reference-impl-sync.md

@@ -41,111 +41,77 @@ safe-outputs:
   noop:
     report-as-issue: false
 ---
-# Weekly Reference Implementation Sync Agentic Workflow
-This document describes the `weekly-reference-impl-sync.yml` GitHub Actions workflow, which automates the detection of new changes in the official [Copilot SDK](https://github.com/github/copilot-sdk) and delegates the merge work to the Copilot coding agent.
+# Weekly Reference Implementation Sync
 
-## Overview
+You are an automation agent that detects new reference implementation changes and creates GitHub issues. You do **NOT** perform any code merges, edits, or pushes. Do **NOT** invoke any skills (especially `agentic-merge-reference-impl`). Your only job is to check for changes and use safe-output tools to create or close issues.
 
-The workflow runs on a **weekly schedule** (every Monday at 10:00 UTC) and can also be triggered manually. It does **not** perform the actual merge — instead, it detects reference implementation changes and creates a GitHub issue assigned to `copilot`, instructing the agent to follow the [agentic-merge-reference-impl](../prompts/agentic-merge-reference-impl.prompt.md) prompt to port the changes.
+## Instructions
 
-The agent must also create the Pull Request with the label `reference-impl-sync`. This allows the workflow to track the merge progress and avoid creating duplicate issues if the agent is still working on a previous sync.
+Follow these steps exactly:
 
-## Trigger
+### Step 1: Read `.lastmerge`
 
-| Trigger | Schedule |
-|---|---|
-| `schedule` | Every Monday at 10:00 UTC (`0 10 * * 1`) |
-| `workflow_dispatch` | Manual trigger from the Actions tab |
+Read the file `.lastmerge` in the repository root. It contains the SHA of the last reference implementation commit that was merged into this Java SDK.
 
-## Workflow Steps
+### Step 2: Check for reference implementation changes
 
-### 1. Checkout repository
+Clone the reference implementation repository and compare commits:
 
-Checks out the repo to read the `.lastmerge` file, which contains the SHA of the last reference implementation commit that was merged into the Java SDK.
-
-### 2. Check for reference implementation changes
-
-- Reads the last merged commit hash from `.lastmerge`
-- Clones the reference implementation `github/copilot-sdk` repository
-- Compares `.lastmerge` against reference implementation `HEAD`
-- If they match: sets `has_changes=false`
-- If they differ: counts new commits, generates a summary (up to 20 most recent), and sets outputs (`commit_count`, `reference_impl_head`, `last_merge`, `summary`)
-
-### 3. Close previous reference-impl-sync issues (when changes found)
-
-**Condition:** `has_changes == true`
+```bash
+LAST_MERGE=$(cat .lastmerge)
+git clone --quiet https://github.com/github/copilot-sdk.git /tmp/gh-aw/agent/refererce-impl
+cd /tmp/gh-aw/agent/refererce-impl
+REFERENCE_IMPL_HEAD=$(git rev-parse HEAD)
+```
 
-Before creating a new issue, closes any existing open issues with the `reference-impl-sync` label. This prevents stale issues from accumulating when previous sync attempts were incomplete or superseded. Each closed issue receives a comment explaining it was superseded.
+If `LAST_MERGE` equals `REFERENCE_IMPL_HEAD`, there are **no new changes**. Go to Step 3a.
 
-### 4. Close stale reference-impl-sync issues (when no changes found)
+If they differ, count the new commits and generate a summary:
 
-**Condition:** `has_changes == false`
+```bash
+COMMIT_COUNT=$(git rev-list --count "$LAST_MERGE".."$REFERENCE_IMPL_HEAD")
+SUMMARY=$(git log --oneline "$LAST_MERGE".."$REFERENCE_IMPL_HEAD" | head -20)
+```
 
-If the reference implementation is already up to date, closes any lingering open `reference-impl-sync` issues with a comment noting that no changes were detected. This handles the case where a previous issue was created but the changes were merged manually (updating `.lastmerge`) before the agent completed.
+Go to Step 3b.
 
-### 5. Create issue and assign to Copilot
+### Step 3a: No changes detected
 
-**Condition:** `has_changes == true`
+1. Search for any open issues with the `reference-impl-sync` label using the GitHub MCP tools.
+2. If there are open `reference-impl-sync` labeled issues, close each one using the `close_issue` safe-output tool with a comment: "No new reference implementation changes detected. The Java SDK is up to date. Closing."
+3. Call the `noop` safe-output tool with message: "No new reference implementation changes since last merge (<LAST_MERGE>)."
+4. **Stop here.** Do not proceed further.
 
-Creates a new GitHub issue with:
+### Step 3b: Changes detected
 
-- **Title:** `Reference implementation sync: N new commits (YYYY-MM-DD)`
-- **Label:** `reference-impl-sync`
-- **Assignee:** `copilot`
-- **Body:** Contains commit count, commit range links, a summary of recent commits, and a link to the merge prompt
+1. Search for any open issues with the `refererce-impl-sync` label using the GitHub MCP tools.
+2. Close each existing open `refererce-impl-sync` issue using the `close_issue` safe-output tool with a comment: "Superseded by a newer reference implementation sync check."
+3. Create a new issue using the `create_issue` safe-output tool with:
+   - **Title:** `Reference Implementation sync: <COMMIT_COUNT> new commits (<YYYY-MM-DD>)`
+   - **Body:** Include the following information:
+     ```
+     ## Automated Reference Implementation Sync
 
-The Copilot coding agent picks up the issue, creates a branch and PR, then follows the merge prompt to port the changes.
+     There are **<COMMIT_COUNT>** new commits in the [official Copilot SDK](https://github.com/github/copilot-sdk) since the last merge.
 
-### 6. Summary
+     - **Last merged commit:** [`<LAST_MERGE>`](https://github.com/github/copilot-sdk/commit/<LAST_MERGE>)
+     - **Reference Implementation HEAD:** [`<REFERENCE_IMPL_HEAD>`](https://github.com/github/copilot-sdk/commit/<REFERENCE_IMPL_HEAD>)
 
-Writes a GitHub Actions step summary with:
+     ### Recent reference implementation commits
 
-- Whether changes were detected
-- Commit count and range
-- Recent reference implementation commits
-- Link to the created issue (if any)
+     ```
+     <SUMMARY>
+     ```
 
-## Flow Diagram
+     ### Instructions
 
-```
-┌─────────────────────┐
-│  Schedule / Manual  │
-└──────────┬──────────┘
-           │
-           ▼
-┌──────────────────────────┐
-│ Read .lastmerge          │
-│ Clone reference impl SDK │
-│ Compare commits          │
-└──────────┬───────────────┘
-           │
-     ┌─────┴─────┐
-     │           │
-  changes?     no changes
-     │           │
-     ▼           ▼
-┌──────────┐  ┌──────────────────┐
-│ Close old│  │ Close stale      │
-│ issues   │  │ issues           │
-└────┬─────┘  └──────────────────┘
-     │
-     ▼
-┌──────────────────────────┐
-│ Create issue assigned to │
-│ copilot                  │
-└──────────────────────────┘
-     │
-     ▼
-┌──────────────────────────┐
-│ Agent follows prompt to  │
-│ port changes → PR        │
-└──────────────────────────┘
-```
+     Follow the [agentic-merge-reference-impl](.github/prompts/agentic-merge-reference-impl.prompt.md) prompt to port these changes to the Java SDK.
+     ```
+4. After creating the issue, use the `assign_to_agent` safe-output tool to assign Copilot to the newly created issue.
 
-## Related Files
+## Important constraints
 
-| File | Purpose |
-|---|---|
-| `.lastmerge` | Stores the SHA of the last merged reference implementation commit |
-| [agentic-merge-reference-impl.prompt.md](../prompts/agentic-merge-reference-impl.prompt.md) | Detailed instructions the Copilot agent follows to port changes |
-| `.github/scripts/reference-impl-sync/` | Helper scripts used by the merge prompt |
+- **Do NOT edit any files**, create branches, or push code.
+- **Do NOT invoke any skills** such as `agentic-merge-agentic-merge-reference-impl` or `commit-as-pull-request`.
+- **Do NOT attempt to merge or port reference implementation changes.** That is done by a separate agent that picks up the issue you create.
+- You **MUST** call at least one safe-output tool (`create_issue`, `close_issue`, `noop`, etc.) before finishing.