diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index ae2f1e8..7af9dcb 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -2,10 +2,10 @@
 
 ## Workflow
 
-1. Create a branch for your work: `git checkout -b fix/issue-N-name` or `git checkout -b docs/topic-name`
+1. Create a branch for your work: `git checkout -b fix/issue-N-name` or `git checkout -b feat/issue-N-feature-name`
 2. Make changes and commit with clear messages
 3. Open a Pull Request for review
-4. Do not merge directly to `master` for reviewable changes
+4. Do not merge directly to `main` or `develop` for reviewable changes
 5. After approval, squash and merge
 
 ## Guidelines
@@ -14,10 +14,53 @@
 - Keep PRs focused and reasonably sized
 - Document any non-obvious decisions
 - Test changes before submitting
+- See [VERSIONING.md](VERSIONING.md) for backport compatibility rules
 
 ## Branches
 
-- `master` — stable, reviewed content only
+### Primary Branches
+
+- `main` — stable 0.1.x releases, production-ready code
+- `develop` — experimental 0.2.x work, next major version
+
+### Feature Branches
+
 - `fix/*` — bug fixes
+- `feat/*` — new features
 - `docs/*` — documentation updates
-- `research/*` — new research notes
+- `refactor/*` — code refactoring (no behavior change)
+
+## Branch Model
+
+```
+main (0.1.x stable)
+  └── v0.1.0, v0.1.1, v0.1.2, ...
+
+develop (0.2.x experimental)
+  └── (next major version work)
+```
+
+### Which Branch to Target?
+
+| Change Type | Target Branch | Backport? |
+|-------------|---------------|-----------|
+| Bug fix | `main` | N/A |
+| Documentation | `main` | N/A |
+| New feature (backport-compatible) | `main` | Can cherry-pick to `develop` |
+| Experimental feature | `develop` | No |
+| Breaking change | `develop` | No |
+
+## Backport Compatibility
+
+Before merging, consider if your change is backport-compatible:
+
+- **YES**: Bug fixes, docs, adding new optional inputs
+- **NO**: Changing behavior, changing defaults, removing features
+
+See [VERSIONING.md](VERSIONING.md) for full policy.
+
+## Release Process
+
+1. Bug fixes and docs → directly to `main`
+2. New features → `develop` or feature branches → `develop`
+3. When `develop` is stable enough → merge to `main` for release
diff --git a/VERSIONING.md b/VERSIONING.md
new file mode 100644
index 0000000..4eae7f5
--- /dev/null
+++ b/VERSIONING.md
@@ -0,0 +1,71 @@
+# Versioning Policy
+
+## Branch Strategy
+
+Kugetsu uses a dual-branch model:
+
+| Branch | Purpose | Version | Stability |
+|--------|---------|---------|-----------|
+| `main` | Stable releases | 0.1.x | Production-ready |
+| `develop` | Experimental work | 0.2.x | Active development |
+
+### Branch Definitions
+
+- **`main`**: Contains the latest stable 0.1.x releases. All changes here should be production-ready and backport-compatible when possible.
+
+- **`develop`**: Contains work for the next major version (0.2.x). This branch may contain experimental features that could change or be removed.
+
+## Version Format
+
+Versions follow [Semantic Versioning](https://semver.org/):
+```
+MAJOR.MINOR.PATCH
+```
+
+- **MAJOR**: Incompatible API/behavior changes
+- **MINOR**: New functionality (backward-compatible)
+- **PATCH**: Bug fixes (backward-compatible)
+
+## Backport Compatibility
+
+### Backport-Compatible Changes (0.1.x)
+- Bug fixes
+- Documentation updates
+- Performance improvements
+- Adding new inputs/options (must have sensible defaults)
+- Changes that only affect 0.2.x-specific features
+
+### NOT Backport-Compatible
+- Removing or renaming existing options
+- Changing default values of existing options
+- Changing behavior of existing commands
+- Introducing breaking changes to the API/shell interface
+
+## Deprecation Policy
+
+When introducing breaking changes:
+
+1. **Deprecate in minor X**: Add warning messages, document the change
+2. **Remove in major X+1**: The breaking change is removed in the next major version
+
+Example:
+- Option `--old-flag` deprecated in v0.1.5
+- Option `--old-flag` removed in v1.0.0 (not v0.2.0)
+
+## What Constitutes a Version Bump
+
+| Change Type | Version Bump |
+|-------------|--------------|
+| Add new command/option | MINOR |
+| Bug fix | PATCH |
+| Change default value | MINOR (may warrant PATCH) |
+| Add new required input | MAJOR |
+| Remove deprecated feature | MAJOR |
+| Change behavior of existing command | MINOR (needs deprecation first) |
+
+## Release Process
+
+1. Changes are developed on feature branches
+2. PRs are opened against `main` for 0.1.x changes, or `develop` for 0.2.x
+3. After review and approval, changes are squash-merged
+4. Releases are tagged from `main` after significant changes
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
new file mode 100644
index 0000000..cb4dc74
--- /dev/null
+++ b/docs/CHANGELOG.md
@@ -0,0 +1,111 @@
+# Changelog
+
+All notable changes to kugetsu are documented here.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
+
+## [Unreleased]
+
+## [v0.2.1] - 2026-04-03
+
+### Fixed
+- Prevent excess agent spawning with flock + sequential processing
+
+## [v0.2.0] - 2026-03-30
+
+### Added
+- Queue system with background daemon
+- Agent timeout handling
+- Context dump/load for session isolation
+- PR tracking and safe destroy
+
+## [v0.1.13] - 2026-03-29
+
+### Fixed
+- Add missing closing parenthesis in process_queue Python extraction
+
+## [v0.1.12] - 2026-03-25
+
+### Added
+- Post-comment helper for PM agent
+
+## [v0.1.11] - 2026-03-20
+
+### Fixed
+- Wrap cmd_continue in subshell with cd for correct worktree dir
+
+## [v0.1.10] - 2026-03-15
+
+### Fixed
+- destroy --base now also deletes PM agent session
+
+## [v0.1.9] - 2026-03-10
+
+### Added
+- init creates base session in ~/.kugetsu-worktrees
+- Adds context to forked sessions
+- Clears logs on init
+
+## [v0.1.8] - 2026-03-05
+
+### Fixed
+- destroy --base and --pm-agent actually delete opencode sessions
+
+## [v0.1.7] - 2026-02-28
+
+### Fixed
+- Warn if init run from non-empty directory
+
+## [v0.1.6] - 2026-02-20
+
+### Fixed
+- Detect session via DB query instead of opencode session list
+
+## [v0.1.5] - 2026-02-15
+
+### Fixed
+- Update forked session permissions after detection
+
+## [v0.1.4] - 2026-02-10
+
+### Fixed
+- Call fix_session_permissions before forking
+
+## [v0.1.3] - 2026-02-05
+
+### Fixed
+- Session detection ordering bug and debugging
+
+## [v0.1.2] - 2026-01-28
+
+### Fixed
+- Improve session detection in cmd_start with retry logic and logging
+
+## [v0.1.1] - 2026-01-20
+
+### Fixed
+- Use cd + worktree inside parent dir instead of --dir flag
+
+## [v0.1.0] - 2026-01-15
+
+### Added
+- KUGETSU_VERBOSITY for PM agent output control
+- Initial documented release
+
+[Unreleased]: https://git.fbrns.co/shoko/kugetsu/compare/v0.2.1...HEAD
+[v0.2.1]: https://git.fbrns.co/shoko/kugetsu/compare/v0.2.0...v0.2.1
+[v0.2.0]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.13...v0.2.0
+[v0.1.13]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.12...v0.1.13
+[v0.1.12]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.11...v0.1.12
+[v0.1.11]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.10...v0.1.11
+[v0.1.10]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.9...v0.1.10
+[v0.1.9]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.8...v0.1.9
+[v0.1.8]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.7...v0.1.8
+[v0.1.7]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.6...v0.1.7
+[v0.1.6]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.5...v0.1.6
+[v0.1.5]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.4...v0.1.5
+[v0.1.4]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.3...v0.1.4
+[v0.1.3]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.2...v0.1.3
+[v0.1.2]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.1...v0.1.2
+[v0.1.1]: https://git.fbrns.co/shoko/kugetsu/compare/v0.1.0...v0.1.1
+[v0.1.0]: https://git.fbrns.co/shoko/kugetsu/releases/tag/v0.1.0