diff --git a/.agents/skills/oci-deal-accelerator/SKILL.md b/.agents/skills/oci-deal-accelerator/SKILL.md
index 05420c3..f37b18a 100644
--- a/.agents/skills/oci-deal-accelerator/SKILL.md
+++ b/.agents/skills/oci-deal-accelerator/SKILL.md
@@ -567,3 +567,5 @@ KB lives under `kb/`. See [kb/README.md](kb/README.md) for the directory map, fr
 - You do NOT claim features exist if you're unsure. Check the KB first.
 - You do NOT do detailed project management. DELIVER artifacts are lightweight handover aids.
 - You do NOT add services or components the user did not request.
+
+<!-- test marker for sync hook -->
diff --git a/.gitea/workflows/skill-sync.yaml b/.gitea/workflows/skill-sync.yaml
new file mode 100644
index 0000000..cb07f47
--- /dev/null
+++ b/.gitea/workflows/skill-sync.yaml
@@ -0,0 +1,49 @@
+# SKILL.md sync gate.
+#
+# Why: the root SKILL.md (read by Claude Code) and
+# .agents/skills/oci-deal-accelerator/SKILL.md (read by Codex) MUST
+# stay byte-aligned modulo the auto-generated banner. If they drift,
+# the two agents give the user different instructions — exactly the
+# class of regression that produced the workload-driven-mode incident
+# Diego flagged on 2026-04-25.
+#
+# This workflow blocks the merge if a PR/push leaves them out of
+# sync. Locally, ``make install-hooks`` enables a pre-commit hook
+# that auto-syncs before the commit lands; this CI step is the
+# safety net for anyone who skipped the hook.
+
+name: SKILL.md sync
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'SKILL.md'
+      - '.agents/skills/oci-deal-accelerator/SKILL.md'
+      - 'scripts/sync-skill.py'
+  pull_request:
+    branches: [main]
+    paths:
+      - 'SKILL.md'
+      - '.agents/skills/oci-deal-accelerator/SKILL.md'
+      - 'scripts/sync-skill.py'
+  workflow_dispatch:
+
+jobs:
+  check-sync:
+    runs-on: ubuntu-latest
+    timeout-minutes: 2
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Python
+        run: |
+          apt-get update -qq
+          apt-get install -y --no-install-recommends python3
+          python3 --version
+
+      - name: Verify SKILL.md is in sync with the Codex copy
+        run: |
+          python3 scripts/sync-skill.py --check
diff --git a/.githooks/pre-commit b/.githooks/pre-commit
new file mode 100644
index 0000000..6461d5a
--- /dev/null
+++ b/.githooks/pre-commit
@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+# Pre-commit hook: keep .agents/skills/oci-deal-accelerator/SKILL.md
+# byte-aligned with the root SKILL.md (the source of truth that
+# CLAUDE.md / Claude Code reads). The Codex copy under .agents/
+# follows the same content with an auto-generated banner — they MUST
+# stay in lock-step or Claude Code and Codex will give the user
+# different instructions.
+#
+# Behavior:
+#   • If SKILL.md is staged but the .agents/ copy is not synced,
+#     auto-run scripts/sync-skill.py and stage the result so the
+#     commit ships both files together.
+#   • If the script can't run (no python, etc.), abort with a clear
+#     message rather than committing a desync silently.
+#
+# Install once per clone:   make install-hooks   (sets core.hooksPath)
+
+set -euo pipefail
+
+ROOT="$(git rev-parse --show-toplevel)"
+SOURCE="SKILL.md"
+TARGET=".agents/skills/oci-deal-accelerator/SKILL.md"
+SCRIPT="scripts/sync-skill.py"
+
+# Only act when SKILL.md is part of the staged change set.
+if ! git diff --cached --name-only | grep -qx "$SOURCE"; then
+    exit 0
+fi
+
+if [ ! -f "$ROOT/$SCRIPT" ]; then
+    echo "pre-commit: $SCRIPT missing — cannot verify SKILL.md sync. Aborting." >&2
+    exit 1
+fi
+
+PYTHON="$(command -v python3 || command -v python || true)"
+if [ -z "$PYTHON" ]; then
+    echo "pre-commit: no python found in PATH — cannot run $SCRIPT. Aborting." >&2
+    exit 1
+fi
+
+# Run the full sync, then stage the regenerated target so it travels
+# in the same commit. (Idempotent — if it was already in sync, the
+# file write is a no-op.)
+"$PYTHON" "$ROOT/$SCRIPT" >&2
+git add "$ROOT/$TARGET"
+
+# Final check — if for any reason the result still drifts, fail loud.
+if ! "$PYTHON" "$ROOT/$SCRIPT" --check >/dev/null 2>&1; then
+    echo "pre-commit: SKILL.md and $TARGET are still out of sync after auto-run." >&2
+    echo "             Investigate scripts/sync-skill.py before committing." >&2
+    exit 1
+fi
+
+exit 0
diff --git a/Makefile b/Makefile
index 6bdeba7..4b71b9b 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 # OCI Deal Accelerator — Build Automation
 
-.PHONY: help install test validate example diagram deck full clean lint codex-package update-icons freshness freshness-refresh sync-skill sku-discover pptx-icons-refresh archcenter-benchmark-20 diagram-lookup diagram-validate-spec archcenter-descriptions-refresh diagram-spec-audit archcenter-smoke
+.PHONY: help install test validate example diagram deck full clean lint codex-package update-icons freshness freshness-refresh sync-skill sku-discover pptx-icons-refresh archcenter-benchmark-20 diagram-lookup diagram-validate-spec archcenter-descriptions-refresh diagram-spec-audit archcenter-smoke install-hooks
 
 # Use venv if present, otherwise find best available python3
 ifneq (,$(wildcard .venv/bin/python))
@@ -25,6 +25,15 @@ venv: ## Create virtual environment and install dependencies
 	.venv/bin/pip install --upgrade pip
 	.venv/bin/pip install -r requirements.txt
 	@echo "Virtual environment ready. Run: source .venv/bin/activate"
+	@echo "Tip: run 'make install-hooks' once to enable the pre-commit"
+	@echo "     hook that keeps SKILL.md in sync with the Codex copy."
+
+install-hooks: ## Install repo-versioned git hooks (pre-commit auto-syncs SKILL.md)
+	@if [ ! -d .git ]; then echo "install-hooks: not a git repo"; exit 1; fi
+	git config core.hooksPath .githooks
+	@echo "install-hooks: core.hooksPath set to .githooks"
+	@echo "  → pre-commit now auto-syncs .agents/skills/.../SKILL.md"
+	@echo "    whenever SKILL.md is part of the staged change set."
 
 install: ## Install Python dependencies (system-wide)
 	pip install -r requirements.txt
diff --git a/README.md b/README.md
index f5765ef..1c36d30 100644
--- a/README.md
+++ b/README.md
@@ -452,6 +452,26 @@ For temporary overrides (e.g., focusing on a specific customer), create `AGENTS.
 
 Full setup details: [`codex/README.md`](codex/README.md)
 
+#### Keeping the Claude and Codex skills in sync
+
+The root `SKILL.md` (read by Claude Code) and `.agents/skills/oci-deal-accelerator/SKILL.md` (read by Codex) MUST stay byte-aligned modulo an auto-generated banner. If they drift, the two agents give the user different instructions.
+
+Three layers of defense, run from least to most enforcement:
+
+1. **Local pre-commit hook (recommended once per clone):**
+   ```bash
+   make install-hooks
+   ```
+   Sets `core.hooksPath = .githooks`. From then on, any commit that touches `SKILL.md` auto-runs `scripts/sync-skill.py` and stages the regenerated `.agents/` copy in the same commit. No manual step required.
+
+2. **Manual sync (anytime):**
+   ```bash
+   make sync-skill          # write the .agents/ copy from SKILL.md
+   make lint                # check (also runs sync --check)
+   ```
+
+3. **CI gate (`.gitea/workflows/skill-sync.yaml`):** every push/PR runs `python scripts/sync-skill.py --check` and fails the build if the two files have drifted. Catches anyone who skipped the hook.
+
 ## Roadmap
 
 ### ECAL Completeness (see `docs/ecal-gaps-backlog.md` for full list)