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+# Sync TSL Playbook Workflow Upgrade Design
+
+## Background
+
+The `tsl-playbook` branch is a mixed branch: the synchronization workflow owns the
+generated TSL playbook paths, while README files and other manually maintained
+content must survive each publication.
+
+The current workflow treats the whole `docs/` and `skills/` directories as generated:
+
+```bash
+generated_paths=(AGENTS.md docs skills)
+```
+
+That ownership boundary is wider than the bundle actually owns. TSL syntax is now
+provided by `tsl-syntax-reference`, while the branch may also contain unrelated
+documentation and Skills that the workflow must not delete.
+
+## Goal
+
+Redesign `.gitea/workflows/sync-tsl-playbook.yml` so it updates only the TSL
+playbook paths while preserving every unrelated target-branch file.
+
+## Managed Paths
+
+The workflow exclusively owns these four paths:
+
+```text
+AGENTS.md
+docs/tsl/
+skills/tsl-syntax-reference/
+skills/tsl-api-reference/
+```
+
+It must preserve all other paths, including:
+
+- root files such as `README.md`;
+- non-TSL documentation under `docs/`;
+- unrelated Skills under `skills/`;
+- any other manually maintained target-branch content.
+
+The workflow does not special-case `docs/tsl/syntax`. Whether that path exists is
+determined by the source tree and the bundle builder, not by publication logic.
+
+## Publication Flow
+
+1. Clone and check out the latest `origin/main` in a temporary repository.
+2. Build the TSL bundle outside the repository working tree.
+3. Validate that all four managed paths exist in the bundle.
+4. Check out the existing remote target branch, or create an orphan target branch.
+5. Remove only the four managed paths from the target working tree.
+6. Copy each managed path explicitly from the bundle.
+7. Stage changes only for the four managed paths.
+8. Exit successfully without a commit when the staged diff is empty.
+9. Otherwise commit with the source SHA footer and push the target branch.
+
+Explicit copying is preferred over copying the bundle root. This keeps the workflow's
+write behavior aligned with its declared ownership boundary even if the bundle gains
+additional top-level files later.
+
+## Branch Behavior
+
+For an existing `tsl-playbook` branch, the workflow starts from
+`origin/tsl-playbook`, so unmanaged files retain their current content and history.
+
+For a new target branch, the workflow creates an orphan branch and clears the inherited
+index before adding the four managed paths. Source-only files from `main` must not leak
+into the new branch.
+
+The workflow must not merge the source and target branches. It publishes a generated
+commit directly on the target branch.
+
+## Failure Handling and Security
+
+- Missing bundle paths fail before the target branch is modified.
+- `set -euo pipefail` remains enabled for shell steps.
+- The bundle remains outside the repository so branch checkout cannot clobber it.
+- Authentication continues through `GIT_ASKPASS`; credentials are never embedded in
+  the remote URL.
+- Temporary bundle and askpass files are removed through existing cleanup paths.
+- A failed copy or validation must prevent commit and push.
+
+## Test Strategy
+
+Update the workflow contract and integration tests before changing the workflow.
+
+The tests must demonstrate that:
+
+- the managed path list contains the four exact paths and not the broad `docs` or
+  `skills` directories;
+- root files outside the managed set survive synchronization;
+- non-TSL documentation under `docs/` survives synchronization;
+- unrelated Skills under `skills/` survive synchronization;
+- stale files inside each managed directory are deleted;
+- a newly created target branch contains the bundle paths without source-branch
+  leakage;
+- an unchanged bundle produces no commit;
+- token handling remains based on `GIT_ASKPASS` and a credential-free repository URL.
+
+## Non-Goals
+
+- Do not change the contents of `AGENTS.md`, TSL documentation, or either TSL Skill.
+- Do not add special handling for obsolete syntax-document paths.
+- Do not redesign `scripts/build_tsl_playbook.py` unless a workflow test exposes an
+  interface mismatch required by the exact managed-path contract.
+- Do not delete or rewrite unrelated files on the target branch.
+- Do not change the target branch name or commit-message convention.
+
+## Acceptance Criteria
+
+- Publication changes are limited to the four managed paths.
+- Unmanaged target-branch files are byte-for-byte preserved.
+- Stale content inside managed paths is removed.
+- New target branches contain no accidental files inherited from `main`.
+- Existing workflow security assertions and sync integration tests pass.
+- The full `test_build_tsl_playbook.py` suite passes.