diff --git a/.github/prompts/commit-message.prompt.yml b/.github/prompts/commit-message.prompt.yml
index 16d5c280..ce975fe9 100644
--- a/.github/prompts/commit-message.prompt.yml
+++ b/.github/prompts/commit-message.prompt.yml
@@ -3,13 +3,15 @@ messages:
     content: |-
       You write concise git commit messages describing automated updates to a Slack Web
       API reference JSON repository (methods, groups and events scraped from Slack's docs).
-      Given a diffstat and a diff, respond with:
+      Given a diffstat and a diff, respond with ONLY a single JSON object (no markdown code
+      fences, no other text) with exactly these two keys:
+      {"title": "...", "summary": "..."}
       - title: a single line, imperative mood, at most 72 characters, no trailing period,
         describing the most significant change (e.g. "Add chat.appendStream and
         chat.stopStream methods").
       - summary: 1-5 short bullet points (each starting with "- "), each describing one
         notable change: new/removed/renamed methods or events, added/removed arguments,
-        changed error codes, etc.
+        changed error codes, etc. Use "" if nothing notable.
       If the diff is routine or has no notable API surface changes, keep the title generic
       (e.g. "Minor documentation updates") and the summary brief or empty.
   - role: user
@@ -19,25 +21,3 @@ messages:
 
       Diff (may be truncated):
       {{diff}}
-model: openai/gpt-4o-mini
-responseFormat: json_schema
-jsonSchema: |-
-  {
-    "name": "commit_message",
-    "strict": true,
-    "schema": {
-      "type": "object",
-      "properties": {
-        "title": {
-          "type": "string",
-          "description": "Single-line, imperative-mood commit title, max 72 characters, no trailing period"
-        },
-        "summary": {
-          "type": "string",
-          "description": "1-5 short bullet points, each starting with '- ', or empty string if nothing notable"
-        }
-      },
-      "additionalProperties": false,
-      "required": ["title", "summary"]
-    }
-  }
diff --git a/.github/workflows/update.yml b/.github/workflows/update.yml
index 1f54574c..d0eaf22a 100644
--- a/.github/workflows/update.yml
+++ b/.github/workflows/update.yml
@@ -7,7 +7,6 @@ on:
 
 permissions:
   contents: write
-  models: read
 
 jobs:
   update:
@@ -39,25 +38,35 @@ jobs:
       - name: Prepare diff for AI summary
         if: steps.changes.outputs.changed == 'true'
         run: |
-          git diff --stat > /tmp/diff_stat.txt
-          git diff | head -c 20000 > /tmp/diff.txt
+          git diff --stat | sed 's/^/      /' > /tmp/diff_stat.txt
+          git diff | head -c 20000 | sed 's/^/      /' > /tmp/diff.txt
+      - name: Set up Node
+        if: steps.changes.outputs.changed == 'true'
+        uses: actions/setup-node@v6
+      - name: Install Copilot CLI
+        if: steps.changes.outputs.changed == 'true'
+        run: npm install -g @github/copilot
       - name: Generate commit message with AI
         if: steps.changes.outputs.changed == 'true'
         id: ai
-        uses: actions/ai-inference@v1
+        uses: actions/ai-inference@v3
         with:
           prompt-file: ./.github/prompts/commit-message.prompt.yml
+          model: ''
           file_input: |
             diff_stat: /tmp/diff_stat.txt
             diff: /tmp/diff.txt
+        env:
+          COPILOT_GITHUB_TOKEN: ${{ secrets.COPILOT_PAT }}
       - name: Build commit message
         id: message
         run: |
           title=""
           summary=""
           if [ "${{ steps.changes.outputs.changed }}" = "true" ]; then
-            title="$(jq -r '.title // empty' "${{ steps.ai.outputs.response-file }}" 2>/dev/null)"
-            summary="$(jq -r '.summary // empty' "${{ steps.ai.outputs.response-file }}" 2>/dev/null)"
+            response="$(grep -v '^```' "${{ steps.ai.outputs.response-file }}" 2>/dev/null)"
+            title="$(echo "$response" | jq -r '.title // empty' 2>/dev/null)"
+            summary="$(echo "$response" | jq -r '.summary // empty' 2>/dev/null)"
           fi
           if [ -z "$title" ]; then
             title="Updated from Slack docs, ${CURRENT_DATE}"
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 73f36a42..744d9141 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@ Changelog
 Some notable infrastructure contributions below. See [commits](commits/master) for Slack API updates.
 
 * Your contribution here.
+* [#89](https://github.com/slack-ruby/slack-api-ref/pull/89): Migrate AI commit message generation to Copilot CLI after GitHub Models retirement - [@dblock](https://github.com/dblock).
 * [#87](https://github.com/slack-ruby/slack-api-ref/pull/87): Generate AI commit summaries for automated API updates - [@dblock](https://github.com/dblock).
 * [#64](https://github.com/slack-ruby/slack-api-ref/pull/64): Add `arg_groups` for groups of arguments whose requirement is interdependent - [@jmanian](https://github.com/jmanian).
 * [#64](https://github.com/slack-ruby/slack-api-ref/pull/64): Add `"format": "json"` attribute for arguments that need to be JSON strings - [@jmanian](https://github.com/jmanian).