diff --git a/document-generate/SKILL.md b/document-generate/SKILL.md
index 22c8053dc..6e3511905 100644
--- a/document-generate/SKILL.md
+++ b/document-generate/SKILL.md
@@ -1145,7 +1145,7 @@ docs: generate [scope] documentation (Diataxis)
 
 Quadrants: [list which quadrants were produced]
 
-Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
+Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
 EOF
 )"
 ```
diff --git a/document-release/sections/release-body.md b/document-release/sections/release-body.md
index f391eb8a3..726d9c677 100644
--- a/document-release/sections/release-body.md
+++ b/document-release/sections/release-body.md
@@ -196,7 +196,7 @@ committing.
 git commit -m "$(cat <<'EOF'
 docs: update project documentation for vX.Y.Z.W
 
-Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
+Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
 EOF
 )"
 ```
diff --git a/hosts/claude.ts b/hosts/claude.ts
index f805da040..097fc1360 100644
--- a/hosts/claude.ts
+++ b/hosts/claude.ts
@@ -38,7 +38,7 @@ const claude: HostConfig = {
     linkingStrategy: 'real-dir-symlink',
   },
 
-  coAuthorTrailer: 'Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>',
+  coAuthorTrailer: 'Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>',
   learningsMode: 'full',
 };
 
diff --git a/scripts/resolvers/utility.ts b/scripts/resolvers/utility.ts
index 3d2e368a2..a6bfbbef7 100644
--- a/scripts/resolvers/utility.ts
+++ b/scripts/resolvers/utility.ts
@@ -369,7 +369,7 @@ Minimum 0 per category.
 export function generateCoAuthorTrailer(ctx: TemplateContext): string {
   const { getHostConfig } = require('../../hosts/index');
   const hostConfig = getHostConfig(ctx.host);
-  return hostConfig.coAuthorTrailer || 'Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>';
+  return hostConfig.coAuthorTrailer || 'Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>';
 }
 
 export function generateChangelogWorkflow(_ctx: TemplateContext): string {
diff --git a/ship/SKILL.md b/ship/SKILL.md
index c20a4d1b1..51c571e61 100644
--- a/ship/SKILL.md
+++ b/ship/SKILL.md
@@ -1174,7 +1174,7 @@ user via AskUserQuestion rather than destroying non-WIP commits.
 git commit -m "$(cat <<'EOF'
 chore: bump version and changelog (vX.Y.Z.W)
 
-Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
+Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
 EOF
 )"
 ```
diff --git a/test/fixtures/golden/claude-ship-SKILL.md b/test/fixtures/golden/claude-ship-SKILL.md
index 8fd3e61b7..51c571e61 100644
--- a/test/fixtures/golden/claude-ship-SKILL.md
+++ b/test/fixtures/golden/claude-ship-SKILL.md
@@ -1174,7 +1174,7 @@ user via AskUserQuestion rather than destroying non-WIP commits.
 git commit -m "$(cat <<'EOF'
 chore: bump version and changelog (vX.Y.Z.W)
 
-Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
+Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
 EOF
 )"
 ```
@@ -1225,6 +1225,8 @@ git push -u origin <branch-name>
 
 ---
 
+**PR/MR title invariant (always applies — do not skip even if you don't open the section below):** Any PR or MR you create OR update in the next step MUST have a title that starts with `v$NEW_VERSION` (the version bumped in Step 12), in the format `v<NEW_VERSION> <type>: <summary>`. Never create or edit a PR/MR title without this prefix. Compute the correct title with the single source of truth helper: `~/.claude/skills/gstack/bin/gstack-pr-title-rewrite.sh "$NEW_VERSION" "<current title>"`. The full create/update procedure (idempotency, redaction scan, self-check) is in the section below.
+
 > **STOP.** Before syncing docs and creating or updating the PR/MR (Steps 18-19), Read `~/.claude/skills/gstack/ship/sections/pr-body.md` and execute it
 > in full. Do not work from memory — that section is the source of truth for this step.