diff --git a/.github/workflows/opencode-gpt-5-codex.yml b/.github/workflows/opencode-gpt-5-codex.yml
new file mode 100644
index 0000000..7066901
--- /dev/null
+++ b/.github/workflows/opencode-gpt-5-codex.yml
@@ -0,0 +1,55 @@
+name: opencode-gpt-5-codex
+
+on:
+  issue_comment:
+    types: [created]
+  pull_request_review_comment:
+    types: [created]
+  issues:
+    types: [opened, edited]
+  pull_request_review:
+    types: [submitted]
+
+jobs:
+  opencode:
+    timeout-minutes: 30 # to accommodate Codex's ability to run for extended periods
+    concurrency:
+      group: opencode-${{ github.event_name }}-${{ github.event.issue.number || github.event.pull_request.number || github.run_id }}
+      cancel-in-progress: true
+    if: |
+      (
+        github.event_name == 'issue_comment' &&
+        contains(github.event.comment.body, '/oc-codex') &&
+        contains(fromJson('["OWNER","MEMBER","COLLABORATOR"]'), github.event.comment.author_association)
+      ) || (
+        github.event_name == 'pull_request_review_comment' &&
+        contains(github.event.comment.body, '/oc-codex') &&
+        contains(fromJson('["OWNER","MEMBER","COLLABORATOR"]'), github.event.comment.author_association)
+      ) || (
+        github.event_name == 'pull_request_review' &&
+        github.event.review.body != null &&
+        contains(github.event.review.body, '/oc-codex') &&
+        contains(fromJson('["OWNER","MEMBER","COLLABORATOR"]'), github.event.review.author_association)
+      ) || (
+        github.event_name == 'issues' &&
+        (
+          (github.event.issue.body != null && contains(github.event.issue.body, '/oc-codex')) ||
+          contains(github.event.issue.title, '/oc-codex')
+        ) &&
+        contains(fromJson('["OWNER","MEMBER","COLLABORATOR"]'), github.event.issue.author_association)
+      )
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      id-token: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Run opencode
+        # They are moving fast at https://github.com/sst/opencode/releases, so pinning the version isn't practical yet. We'll keep it at `latest` for now and monitor the changes for a stable version. Latest version as of this writing is `v0.15.3`.
+        uses: sst/opencode/github@latest
+        env:
+          OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY_FOR_OPENCODE }}
+        with:
+          model: openai/gpt-5-codex