chore(main): release 2.3.0 (#78)

Co-authored-by: jimehbot[bot] <132453784+jimehbot[bot]@users.noreply.github.com>

.github/.release-please-manifest.json

@@ -1,3 +1,3 @@
 {
-  ".": "2.2.1"
+  ".": "2.3.0"
 }

.github/workflows/dependabot-rebuild.yml

@@ -12,7 +12,8 @@ permissions:
 jobs:
   rebuild:
     runs-on: ubuntu-latest
-    if: ${{ github.actor == 'dependabot[bot]' && github.event.sender.login == 'dependabot[bot]' }}
+    if: |-
+      ${{ github.actor == 'dependabot[bot]' && github.event.sender.login == 'dependabot[bot]' }}
     steps:
       - name: Generate app token
         id: app-token

.licenses/npm/handlebars.dep.yml

@@ -0,0 +1,36 @@
+---
+name: handlebars
+version: 4.7.8
+type: npm
+summary: Handlebars provides the power necessary to let you build semantic templates
+  effectively with no frustration
+homepage: https://www.handlebarsjs.com/
+license: mit
+licenses:
+- sources: LICENSE
+  text: |
+    Copyright (C) 2011-2019 by Yehuda Katz
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+- sources: README.markdown
+  text: |-
+    Handlebars.js is released under the MIT license.
+
+    [pull-request]: https://github.com/handlebars-lang/handlebars.js/pull/new/master
+notices: []

.licenses/npm/minimist.dep.yml

@@ -0,0 +1,44 @@
+---
+name: minimist
+version: 1.2.8
+type: npm
+summary: parse argument options
+homepage: https://github.com/minimistjs/minimist
+license: other
+licenses:
+- sources: LICENSE
+  text: |
+    This software is released under the MIT license:
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy of
+    this software and associated documentation files (the "Software"), to deal in
+    the Software without restriction, including without limitation the rights to
+    use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+    the Software, and to permit persons to whom the Software is furnished to do so,
+    subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in all
+    copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+    FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+    COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+    IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+    CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+- sources: README.md
+  text: |-
+    MIT
+
+    [package-url]: https://npmjs.org/package/minimist
+    [npm-version-svg]: https://versionbadg.es/minimistjs/minimist.svg
+    [npm-badge-png]: https://nodei.co/npm/minimist.png?downloads=true&stars=true
+    [license-image]: https://img.shields.io/npm/l/minimist.svg
+    [license-url]: LICENSE
+    [downloads-image]: https://img.shields.io/npm/dm/minimist.svg
+    [downloads-url]: https://npm-stat.com/charts.html?package=minimist
+    [codecov-image]: https://codecov.io/gh/minimistjs/minimist/branch/main/graphs/badge.svg
+    [codecov-url]: https://app.codecov.io/gh/minimistjs/minimist/
+    [actions-image]: https://img.shields.io/endpoint?url=https://github-actions-badge-u3jn4tfpocch.runkit.sh/minimistjs/minimist
+    [actions-url]: https://github.com/minimistjs/minimist/actions
+notices: []

.licenses/npm/neo-async.dep.yml

@@ -0,0 +1,36 @@
+---
+name: neo-async
+version: 2.6.2
+type: npm
+summary: 'Neo-Async is a drop-in replacement for Async, it almost fully covers its
+  functionality and runs faster '
+homepage: https://github.com/suguru03/neo-async
+license: other
+licenses:
+- sources: LICENSE
+  text: |
+    MIT License
+
+    Copyright (c) 2014-2018 Suguru Motegi
+    Based on Async.js, Copyright Caolan McMahon
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in all
+    copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+    SOFTWARE.
+- sources: README.md
+  text: "[![FOSSA Status](https://app.fossa.io/api/projects/git%2Bgithub.com%2Fsuguru03%2Fneo-async.svg?type=large)](https://app.fossa.io/projects/git%2Bgithub.com%2Fsuguru03%2Fneo-async?ref=badge_large)"
+notices: []

.licenses/npm/semver.dep.yml

@@ -0,0 +1,26 @@
+---
+name: semver
+version: 7.7.3
+type: npm
+summary: The semantic version parser used by npm.
+homepage:
+license: isc
+licenses:
+- sources: LICENSE
+  text: |
+    The ISC License
+
+    Copyright (c) Isaac Z. Schlueter and Contributors
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
+    IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+notices: []

.licenses/npm/source-map.dep.yml

@@ -0,0 +1,39 @@
+---
+name: source-map
+version: 0.6.1
+type: npm
+summary: Generates and consumes source maps
+homepage: https://github.com/mozilla/source-map
+license: other
+licenses:
+- sources: LICENSE
+  text: |2
+
+    Copyright (c) 2009-2011, Mozilla Foundation and contributors
+    All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright notice, this
+      list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above copyright notice,
+      this list of conditions and the following disclaimer in the documentation
+      and/or other materials provided with the distribution.
+
+    * Neither the names of the Mozilla Foundation nor the names of project
+      contributors may be used to endorse or promote products derived from this
+      software without specific prior written permission.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+    ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+    FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+    SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+    OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+notices: []

.licenses/npm/uglify-js.dep.yml

@@ -0,0 +1,40 @@
+---
+name: uglify-js
+version: 3.19.3
+type: npm
+summary: JavaScript parser, mangler/compressor and beautifier toolkit
+homepage:
+license: other
+licenses:
+- sources: LICENSE
+  text: |
+    UglifyJS is released under the BSD license:
+
+    Copyright 2012-2024 (c) Mihai Bazon <mihai.bazon@gmail.com>
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions
+    are met:
+
+        * Redistributions of source code must retain the above
+          copyright notice, this list of conditions and the following
+          disclaimer.
+
+        * Redistributions in binary form must reproduce the above
+          copyright notice, this list of conditions and the following
+          disclaimer in the documentation and/or other materials
+          provided with the distribution.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
+    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
+    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+    OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+    TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+    THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+    SUCH DAMAGE.
+notices: []

.licenses/npm/wordwrap.dep.yml

@@ -0,0 +1,29 @@
+---
+name: wordwrap
+version: 1.0.0
+type: npm
+summary: Wrap those words. Show them at what columns to start and stop.
+homepage:
+license: other
+licenses:
+- sources: LICENSE
+  text: |
+    This software is released under the MIT license:
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy of
+    this software and associated documentation files (the "Software"), to deal in
+    the Software without restriction, including without limitation the rights to
+    use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+    the Software, and to permit persons to whom the Software is furnished to do so,
+    subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in all
+    copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+    FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+    COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+    IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+    CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+notices: []

AGENTS.md

@@ -19,6 +19,10 @@ tags.
 up-to-date. Always run `npm run package` (or `npm run bundle`) after modifying
 `src/` files.
 
+**License Compliance**: After modifying NPM dependencies, check license status
+and re-cache if needed via `npm run licensed:status` and
+`npm run licensed:cache`.
+
 ## Development Commands
 
 Package manager: npm
@@ -35,7 +39,7 @@ npm run package       # Build src/index.ts -> dist/index.js via Rollup
 npm run bundle        # Alias: format + package
 
 # Run a single test file
-NODE_OPTIONS=--experimental-vm-modules NODE_NO_WARNINGS=1 npx jest tests/main.test.ts
+NODE_OPTIONS=--experimental-vm-modules NODE_NO_WARNINGS=1 jest tests/main.test.ts
 
 # CI variants (suppress warnings)
 npm run ci-test       # Run tests in CI mode
@@ -48,6 +52,10 @@ npm run update-readme
 
 # Watch mode
 npm run package:watch # Auto-rebuild on changes
+
+# License compliance (after modifying dependencies)
+npm run licensed:status  # Check license status of dependencies
+npm run licensed:cache   # Re-cache licenses if needed
 ```
 
 ## Code Architecture
@@ -59,6 +67,11 @@ npm run package:watch # Auto-rebuild on changes
   function that coordinates input parsing, tag processing, and output setting
 - **[src/inputs.ts](src/inputs.ts)**: Input parsing and validation. Exports
   `getInputs()` that reads action inputs and `Inputs` interface
+- **[src/derive.ts](src/derive.ts)**: Semver parsing and tag derivation:
+  - `parseSemver()`: Parses version strings into components (prefix, major,
+    minor, patch, prerelease, build)
+  - `renderTemplate()`: Renders Handlebars templates with semver context
+  - `deriveTags()`: Derives tags from a version string using a template
 - **[src/tags.ts](src/tags.ts)**: Tag planning and execution logic:
   - `planTagOperations()`: Parses tags, pre-resolves refs to SHAs in parallel,
     plans create/update/skip operations
@@ -72,13 +85,36 @@ npm run package:watch # Auto-rebuild on changes
 ### Tag Input Parsing
 
 Uses `csv-parse/sync` to handle both CSV and newline-delimited formats. Supports
-per-tag ref overrides: `v1:main` tags `v1` to `main` branch.
+per-tag ref and annotation overrides using the format `tag:ref:annotation`:
+
+- `tag` — Use default `ref` and `annotation` inputs
+- `tag:ref` — Override ref for this tag (e.g., `v1:main` tags `v1` to `main`)
+- `tag:ref:annotation` — Override both ref and annotation
+- `tag::annotation` — Override annotation only (empty ref uses default)
+
+Annotations can contain colons; everything after the second colon is treated as
+the annotation text. Per-tag values override the global `ref` and `annotation`
+inputs.
+
+### Tag Derivation
+
+The `derive_from` input allows automatic generation of tags from a semver
+version string. Uses Handlebars templates with these placeholders:
+
+- `{{prefix}}`: "v" or "V" if input had prefix, empty otherwise
+- `{{major}}`, `{{minor}}`, `{{patch}}`: Version numbers
+- `{{prerelease}}`, `{{build}}`: Optional semver components
+- `{{version}}`: Full version without prefix
+
+Default template `{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}` generates
+major and minor tags (e.g., `v1.2.3` → `v1`, `v1.2`). Supports Handlebars
+conditionals like `{{#if prerelease}}...{{/if}}`.
 
 ### Tag Update Logic
 
 1. Parse and validate inputs ([inputs.ts](src/inputs.ts))
 2. Plan all tag operations ([tags.ts](src/tags.ts):planTagOperations):
-   - Parse `tag:ref` syntax and extract per-tag refs
+   - Parse `tag:ref:annotation` syntax and extract per-tag refs/annotations
    - Pre-resolve all unique refs to SHAs in parallel (optimization)
    - For each tag, check existence and determine operation:
      - If exists + fail mode: Fail action immediately
@@ -188,12 +224,19 @@ chore(deps): bump @actions/core to v1.10.0
 
 **Inputs:**
 
-- `tags`: CSV/newline list, supports `tag:ref` syntax
-- `ref`: SHA/ref to tag (default: current commit)
+- `tags`: CSV/newline list, supports `tag:ref:annotation` syntax for per-tag
+  overrides
+- `derive_from`: Semver version string to derive tags from (e.g., "v1.2.3")
+- `derive_from_template`: Handlebars template for tag derivation (default:
+  `{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}`)
+- `ref`: Default SHA/ref to tag (default: current commit)
 - `when_exists`: update|skip|fail (default: update)
-- `annotation`: Optional message for annotated tags (default: lightweight)
+- `annotation`: Default annotation message for tags (default: lightweight/none)
+- `dry_run`: Log planned operations without executing (default: false)
 - `github_token`: Auth token (default: github.token)
 
+Either `tags` or `derive_from` (or both) must be provided.
+
 **Outputs:**
 
 - `tags`: All created/updated tags

CHANGELOG.md

@@ -1,5 +1,14 @@
 # Changelog
 
+## [2.3.0](https://github.com/jimeh/update-tags-action/compare/v2.2.1...v2.3.0) (2025-12-24)
+
+
+### Features
+
+* **inputs/derive_from:** derive tags from provided semver string ([#79](https://github.com/jimeh/update-tags-action/issues/79)) ([1d171e9](https://github.com/jimeh/update-tags-action/commit/1d171e9f3c63639b8d0145a881a6df941200742d))
+* **inputs/dry_run:** add dry run support ([#76](https://github.com/jimeh/update-tags-action/issues/76)) ([ef41989](https://github.com/jimeh/update-tags-action/commit/ef4198907727f6ff9e5813deb5ab5a4307ab4691))
+* **inputs/tags:** support per-tag annotation overrides ([#81](https://github.com/jimeh/update-tags-action/issues/81)) ([32e66b0](https://github.com/jimeh/update-tags-action/commit/32e66b04be37383e2450d698007faa436c706ffd))
+
 ## [2.2.1](https://github.com/jimeh/update-tags-action/compare/v2.2.0...v2.2.1) (2025-12-22)
 
 

README.md

@@ -22,23 +22,50 @@ to move its own major and minor tags.
 
 ### Basic
 
-<!-- x-release-please-start-minor -->
-
 ```yaml
 - uses: jimeh/update-tags-action@v2
   with:
-    tags: v2,v2.2
+    tags: v1,v1.2
 ```
 
 ```yaml
 - uses: jimeh/update-tags-action@v2
   with:
     tags: |
-      v2
-      v2.2
+      v1
+      v1.2
 ```
 
-<!-- x-release-please-end -->
+### Deriving Tags from Version
+
+Automatically derive major and minor tags from a semver version string:
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    derive_from: v1.2.3
+    # Creates tags: v1, v1.2
+```
+
+With a custom template (major tag only):
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    derive_from: v1.2.3
+    derive_from_template: '{{prefix}}{{major}}'
+    # Creates tag: v1
+```
+
+Combine derived tags with explicit tags:
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    derive_from: v1.2.3
+    tags: latest
+    # Creates tags: latest, v1, v1.2
+```
 
 ### With Release Please
 
@@ -65,8 +92,7 @@ jobs:
     if: ${{ github.ref == 'refs/heads/main' }}
     outputs:
       release_created: ${{ steps.release-please.outputs.release_created }}
-      major: ${{ steps.release-please.outputs.major }}
-      minor: ${{ steps.release-please.outputs.minor }}
+      tag_name: ${{ steps.release-please.outputs.tag_name }}
     permissions:
       contents: write
       issues: write
@@ -79,8 +105,6 @@ jobs:
 And finally a job to create MAJOR and MINOR release tags, which only runs when
 release-please reports having created a release:
 
-<!-- x-release-please-start-major -->
-
 ```yaml
 jobs:
   # [...]
@@ -93,26 +117,153 @@ jobs:
     steps:
       - uses: jimeh/update-tags-action@v2
         with:
-          tags: |
-            v${{ needs.release-please.outputs.major }}
-            v${{ needs.release-please.outputs.major }}.${{ needs.release-please.outputs.minor }}
+          derive_from: ${{ needs.release-please.outputs.tag_name }}
+          # Creates tags: v1, v1.2 (for tag_name v1.2.3)
 ```
 
-<!-- x-release-please-end -->
-
 <!-- action-docs-inputs source="action.yml" -->
 
 ## Inputs
 
-| name           | description                                                                                                           | required | default               |
-| -------------- | --------------------------------------------------------------------------------------------------------------------- | -------- | --------------------- |
-| `tags`         | <p>List/CSV of tags to create/update.</p>                                                                             | `true`   | `""`                  |
-| `ref`          | <p>The SHA or ref to tag. Defaults to SHA of current commit.</p>                                                      | `false`  | `${{ github.sha }}`   |
-| `when_exists`  | <p>What to do if the tag already exists. Must be one of 'update', 'skip', or 'fail'.</p>                              | `false`  | `update`              |
-| `annotation`   | <p>Optional annotation message for tags. If provided, creates annotated tags. If empty, creates lightweight tags.</p> | `false`  | `""`                  |
-| `github_token` | <p>The GitHub token to use for authentication.</p>                                                                    | `false`  | `${{ github.token }}` |
+| name                   | description                                                                                                                                                                                                                                                                                                                                                                    | required | default                                             |
+| ---------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | -------- | --------------------------------------------------- |
+| `tags`                 | <p>List/CSV of tags to create/update. Supports per-tag ref and annotation overrides using the format 'tag:ref:annotation'. Use 'tag::annotation' to specify an annotation with the default ref.</p>                                                                                                                                                                            | `false`  | `""`                                                |
+| `derive_from`          | <p>Semver version string to derive tags from (e.g., 'v1.2.3'). When provided, generates tags using <code>derive_from_template</code> input. Default template will produce major and minor tags. (e.g., 'v1', 'v1.2')</p>                                                                                                                                                       | `false`  | `""`                                                |
+| `derive_from_template` | <p>Handlebars template for deriving tags from the <code>derive_from</code> input. Uses the same format as the <code>tags</code> input, and supports the following handlebars placeholders: <code>{{prefix}}</code>, <code>{{major}}</code>, <code>{{minor}}</code>, <code>{{patch}}</code>, <code>{{prerelease}}</code>, <code>{{build}}</code>, <code>{{version}}</code>.</p> | `false`  | `{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}` |
+| `ref`                  | <p>The SHA or ref to tag. Defaults to SHA of current commit.</p>                                                                                                                                                                                                                                                                                                               | `false`  | `${{ github.sha }}`                                 |
+| `when_exists`          | <p>What to do if the tag already exists. Must be one of 'update', 'skip', or 'fail'.</p>                                                                                                                                                                                                                                                                                       | `false`  | `update`                                            |
+| `annotation`           | <p>Optional default annotation message for tags. If provided, creates annotated tags. If empty, creates lightweight tags. Can be overridden per-tag using the 'tag:ref:annotation' syntax in the tags input.</p>                                                                                                                                                               | `false`  | `""`                                                |
+| `dry_run`              | <p>If true, logs planned operations without executing them.</p>                                                                                                                                                                                                                                                                                                                | `false`  | `false`                                             |
+| `github_token`         | <p>The GitHub token to use for authentication.</p>                                                                                                                                                                                                                                                                                                                             | `false`  | `${{ github.token }}`                               |
 
 <!-- action-docs-inputs source="action.yml" -->
+
+### Tag Input Syntax
+
+The `tags` input accepts a comma or newline-delimited list of tags. Each tag
+specification supports optional per-tag ref and annotation overrides using the
+format:
+
+```
+tag[:ref[:annotation]]
+```
+
+| Format               | Description                                     |
+| -------------------- | ----------------------------------------------- |
+| `tag`                | Tag using default `ref` and `annotation` inputs |
+| `tag:ref`            | Tag using specified ref, default annotation     |
+| `tag:ref:annotation` | Tag using specified ref and annotation          |
+| `tag::annotation`    | Tag using default ref with specified annotation |
+
+**Per-tag refs** allow different tags to point to different commits:
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    tags: |
+      v1:main
+      v2:develop
+```
+
+**Per-tag annotations** allow different annotation messages for each tag:
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    tags: |
+      v1:main:Latest v1.x release
+      v1.2:main:Latest v1.2.x release
+```
+
+Use `tag::annotation` to specify an annotation while using the default ref:
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    tags: |
+      v1::This is the v1 tag annotation
+      v1.2::This is the v1.2 tag annotation
+```
+
+Per-tag values override the global `ref` and `annotation` inputs:
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    tags: |
+      v1:main:Custom annotation for v1
+      v2
+    ref: develop
+    annotation: Default annotation for tags without per-tag override
+    # v1 -> main with "Custom annotation for v1"
+    # v2 -> develop with "Default annotation..."
+```
+
+Annotations can contain colons (everything after the second colon is the
+annotation):
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    tags: |
+      v1:main:Release: version 1.0.0
+    # Annotation will be "Release: version 1.0.0"
+```
+
+### Derive Template Syntax
+
+The `derive_from_template` input uses [Handlebars](https://handlebarsjs.com/)
+for template rendering. Splitting the template into separate tags by comma or
+newline is done after the template is rendered.
+
+Available placeholders:
+
+| Placeholder      | Description                                           |
+| ---------------- | ----------------------------------------------------- |
+| `{{prefix}}`     | `v` or `V` if input had a prefix, empty otherwise     |
+| `{{major}}`      | Major version number                                  |
+| `{{minor}}`      | Minor version number                                  |
+| `{{patch}}`      | Patch version number                                  |
+| `{{prerelease}}` | Prerelease identifier (e.g., `beta.1`), empty if none |
+| `{{build}}`      | Build metadata (e.g., `build.123`), empty if none     |
+| `{{version}}`    | Full version string without prefix                    |
+
+#### Conditional Sections
+
+Use Handlebars `{{#if}}` blocks to include content only when a variable has a
+value. This is useful for optional components like prerelease or build metadata:
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    derive_from: v1.2.3-beta.1
+    derive_from_template: |
+      {{prefix}}{{major}}{{#if prerelease}}-{{prerelease}}{{/if}}
+    # Creates tag: v1-beta.1
+```
+
+For a stable release without prerelease:
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    derive_from: v1.2.3
+    derive_from_template: |
+      {{prefix}}{{major}}{{#if prerelease}}-{{prerelease}}{{/if}}
+    # Creates tag: v1 (prerelease section omitted)
+```
+
+You can also use `{{#unless}}` for inverse logic:
+
+```yaml
+- uses: jimeh/update-tags-action@v2
+  with:
+    derive_from: v1.2.3
+    derive_from_template: |
+      {{prefix}}{{major}}{{#unless prerelease}}-stable{{/unless}}
+    # Creates tag: v1-stable (only for non-prerelease versions)
+```
+
 <!-- action-docs-outputs source="action.yml" -->
 
 ## Outputs

action.yml

@@ -8,8 +8,25 @@ branding:
 
 inputs:
   tags:
-    description: "List/CSV of tags to create/update."
-    required: true
+    description: >-
+      List/CSV of tags to create/update. Supports per-tag ref and annotation
+      overrides using the format 'tag:ref:annotation'. Use 'tag::annotation' to
+      specify an annotation with the default ref.
+    required: false
+  derive_from:
+    description: >-
+      Semver version string to derive tags from (e.g., 'v1.2.3'). When provided,
+      generates tags using `derive_from_template` input. Default template will
+      produce major and minor tags. (e.g., 'v1', 'v1.2')
+    required: false
+  derive_from_template:
+    description: >-
+      Handlebars template for deriving tags from the `derive_from` input. Uses
+      the same format as the `tags` input, and supports the following handlebars
+      placeholders: `{{prefix}}`, `{{major}}`, `{{minor}}`, `{{patch}}`,
+      `{{prerelease}}`, `{{build}}`, `{{version}}`.
+    required: false
+    default: "{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}"
   ref:
     description: "The SHA or ref to tag. Defaults to SHA of current commit."
     required: false
@@ -22,10 +39,16 @@ inputs:
     default: "update"
   annotation:
     description: >-
-      Optional annotation message for tags. If provided, creates annotated tags.
-      If empty, creates lightweight tags.
+      Optional default annotation message for tags. If provided, creates
+      annotated tags. If empty, creates lightweight tags. Can be overridden
+      per-tag using the 'tag:ref:annotation' syntax in the tags input.
     required: false
     default: ""
+  dry_run:
+    description: >-
+      If true, logs planned operations without executing them.
+    required: false
+    default: "false"
   github_token:
     description: "The GitHub token to use for authentication."
     required: false

package-lock.json

@@ -1,16 +1,18 @@
 {
   "name": "update-tags-action",
-  "version": "2.2.1",
+  "version": "2.3.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "update-tags-action",
-      "version": "2.2.1",
+      "version": "2.3.0",
       "dependencies": {
         "@actions/core": "^2.0.1",
         "@actions/github": "^6.0.1",
-        "csv-parse": "^6.1.0"
+        "csv-parse": "^6.1.0",
+        "handlebars": "^4.7.8",
+        "semver": "^7.7.3"
       },
       "devDependencies": {
         "@eslint/compat": "^2.0.0",
@@ -20,6 +22,7 @@
         "@rollup/plugin-typescript": "^12.3.0",
         "@types/jest": "^30.0.0",
         "@types/node": "^25.0.3",
+        "@types/semver": "^7.7.1",
         "@typescript-eslint/eslint-plugin": "^8.50.0",
         "@typescript-eslint/parser": "^8.46.2",
         "action-docs": "^2.5.1",
@@ -2333,6 +2336,13 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@types/semver": {
+      "version": "7.7.1",
+      "resolved": "https://registry.npmjs.org/@types/semver/-/semver-7.7.1.tgz",
+      "integrity": "sha512-FmgJfu+MOcQ370SD0ev7EI8TlCAfKYU+B4m5T3yXc1CiRN94g/SZPtsCkk506aUDtlMnFZvasDwHHUcZUEaYuA==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@types/stack-utils": {
       "version": "2.0.3",
       "resolved": "https://registry.npmjs.org/@types/stack-utils/-/stack-utils-2.0.3.tgz",
@@ -5215,7 +5225,6 @@
       "version": "4.7.8",
       "resolved": "https://registry.npmjs.org/handlebars/-/handlebars-4.7.8.tgz",
       "integrity": "sha512-vafaFqs8MZkRrSX7sFVUdo3ap/eNiLnb4IakshzvP56X5Nr1iGKAIqdX6tMlm6HcNRIkr6AxO5jFEoJzzpT8aQ==",
-      "dev": true,
       "license": "MIT",
       "dependencies": {
         "minimist": "^1.2.5",
@@ -7093,7 +7102,6 @@
       "version": "1.2.8",
       "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.8.tgz",
       "integrity": "sha512-2yyAR8qBkN3YuheJanUpWC5U3bb5osDywNB8RzDVlDwDHbocAJveqqj1u8+SVD7jkWT4yvsHCpWqqWqAxb0zCA==",
-      "dev": true,
       "license": "MIT",
       "funding": {
         "url": "https://github.com/sponsors/ljharb"
@@ -7153,7 +7161,6 @@
       "version": "2.6.2",
       "resolved": "https://registry.npmjs.org/neo-async/-/neo-async-2.6.2.tgz",
       "integrity": "sha512-Yd3UES5mWCSqR+qNT93S3UoYUkqAZ9lLg8a7g9rimsWmYGK8cVToA4/sF3RrshdyV3sAGMXVUmpMYOw+dLpOuw==",
-      "dev": true,
       "license": "MIT"
     },
     "node_modules/nice-try": {
@@ -8896,7 +8903,6 @@
       "version": "7.7.3",
       "resolved": "https://registry.npmjs.org/semver/-/semver-7.7.3.tgz",
       "integrity": "sha512-SdsKMrI9TdgjdweUSR9MweHA4EJ8YxHn8DFaDisvhVlUOe4BF1tLD7GAj0lIqWVl+dPb/rExr0Btby5loQm20Q==",
-      "dev": true,
       "license": "ISC",
       "bin": {
         "semver": "bin/semver.js"
@@ -9120,7 +9126,6 @@
       "version": "0.6.1",
       "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.6.1.tgz",
       "integrity": "sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g==",
-      "dev": true,
       "license": "BSD-3-Clause",
       "engines": {
         "node": ">=0.10.0"
@@ -10134,7 +10139,6 @@
       "version": "3.19.3",
       "resolved": "https://registry.npmjs.org/uglify-js/-/uglify-js-3.19.3.tgz",
       "integrity": "sha512-v3Xu+yuwBXisp6QYTcH4UbH+xYJXqnq2m/LtQVWKWzYc1iehYnLixoQDN9FH6/j9/oybfd6W9Ghwkl8+UMKTKQ==",
-      "dev": true,
       "license": "BSD-2-Clause",
       "optional": true,
       "bin": {
@@ -10480,7 +10484,6 @@
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/wordwrap/-/wordwrap-1.0.0.tgz",
       "integrity": "sha512-gvVzJFlPycKc5dZN4yPkP8w7Dc37BtP1yczEneOb4uq34pXZcvrtRTmWV8W+Ume+XCxKgbjM+nevkyFPMybd4Q==",
-      "dev": true,
       "license": "MIT"
     },
     "node_modules/wrap-ansi": {

package.json

@@ -1,6 +1,6 @@
 {
   "name": "update-tags-action",
-  "version": "2.2.1",
+  "version": "2.3.0",
   "author": "jimeh",
   "type": "module",
   "private": true,
@@ -43,7 +43,9 @@
   "dependencies": {
     "@actions/core": "^2.0.1",
     "@actions/github": "^6.0.1",
-    "csv-parse": "^6.1.0"
+    "csv-parse": "^6.1.0",
+    "handlebars": "^4.7.8",
+    "semver": "^7.7.3"
   },
   "devDependencies": {
     "@eslint/compat": "^2.0.0",
@@ -53,6 +55,7 @@
     "@rollup/plugin-typescript": "^12.3.0",
     "@types/jest": "^30.0.0",
     "@types/node": "^25.0.3",
+    "@types/semver": "^7.7.1",
     "@typescript-eslint/eslint-plugin": "^8.50.0",
     "@typescript-eslint/parser": "^8.46.2",
     "action-docs": "^2.5.1",

src/derive.ts

@@ -0,0 +1,105 @@
+import { parse } from 'csv-parse/sync'
+import Handlebars from 'handlebars'
+import * as semver from 'semver'
+
+/**
+ * Context containing parsed semver components for template rendering.
+ */
+export interface SemverContext {
+  /** "v" or "V" if input had a prefix, empty string otherwise */
+  prefix: string
+  /** Major version number */
+  major: number
+  /** Minor version number */
+  minor: number
+  /** Patch version number */
+  patch: number
+  /** Prerelease identifier (e.g., "beta.1"), empty if none */
+  prerelease: string
+  /** Build metadata (e.g., "build.123"), empty if none */
+  build: string
+  /** Full version string without prefix */
+  version: string
+}
+
+/**
+ * Parse a version string into semver components.
+ *
+ * @param input - Version string (e.g., "v1.2.3", "1.2.3-beta.1+build.456")
+ * @returns Parsed semver context
+ * @throws Error if the version string is not valid semver
+ */
+export function parseSemver(input: string): SemverContext {
+  const trimmed = input.trim()
+  if (!trimmed) {
+    throw new Error('Invalid semver: empty string')
+  }
+
+  // Check for v/V prefix and preserve original case
+  const firstChar = trimmed[0]
+  const hasPrefix = firstChar === 'v' || firstChar === 'V'
+  const prefix = hasPrefix ? firstChar : ''
+  const versionStr = hasPrefix ? trimmed.slice(1) : trimmed
+
+  // Parse with semver library
+  const parsed = semver.parse(versionStr)
+  if (!parsed) {
+    throw new Error(`Invalid semver: '${input}'`)
+  }
+
+  return {
+    prefix,
+    major: parsed.major,
+    minor: parsed.minor,
+    patch: parsed.patch,
+    prerelease: parsed.prerelease.join('.'),
+    build: parsed.build.join('.'),
+    version: parsed.version
+  }
+}
+
+/**
+ * Render a single template string with semver context using Handlebars.
+ * Supports {{#if variable}}...{{/if}} conditionals for optional sections.
+ *
+ * @param template - Handlebars template string
+ * @param ctx - Semver context for substitution
+ * @returns Rendered string
+ */
+export function renderTemplate(template: string, ctx: SemverContext): string {
+  const compiled = Handlebars.compile(template, { noEscape: true })
+  // Convert numbers to strings so 0 is truthy in conditionals
+  const stringCtx = {
+    ...ctx,
+    major: String(ctx.major),
+    minor: String(ctx.minor),
+    patch: String(ctx.patch)
+  }
+  return compiled(stringCtx)
+}
+
+/**
+ * Derive tags from a semver version string using a template.
+ *
+ * @param deriveFrom - Semver version string (e.g., "v1.2.3")
+ * @param template - CSV/newline-delimited Handlebars template string
+ * @returns Array of derived tag strings
+ */
+export function deriveTags(deriveFrom: string, template: string): string[] {
+  const ctx = parseSemver(deriveFrom)
+
+  // Render template with Handlebars first, enabling conditional tag inclusion
+  const rendered = renderTemplate(template, ctx)
+
+  // Parse rendered result as CSV/newline delimited
+  const tags = (
+    parse(rendered, {
+      delimiter: ',',
+      trim: true,
+      relax_column_count: true
+    }) as string[][]
+  ).flat()
+
+  // Exclude empty tags and tags that are just the prefix with no version data
+  return tags.filter((tag) => tag.length > 0 && tag !== ctx.prefix)
+}

src/inputs.ts

@@ -1,6 +1,7 @@
 import * as core from '@actions/core'
 import * as github from '@actions/github'
 import { parse } from 'csv-parse/sync'
+import { deriveTags } from './derive.js'
 
 const WHEN_EXISTS_MODES = ['update', 'skip', 'fail'] as const
 export type WhenExistsMode = (typeof WHEN_EXISTS_MODES)[number]
@@ -10,6 +11,7 @@ export interface Inputs {
   defaultRef: string
   whenExists: WhenExistsMode
   annotation: string
+  dryRun: boolean
   owner: string
   repo: string
   token: string
@@ -32,37 +34,62 @@ function validateWhenExists(input: string): WhenExistsMode {
   return input as WhenExistsMode
 }
 
+const DEFAULT_DERIVE_FROM_TEMPLATE =
+  '{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}'
+
 /**
  * Get and validate action inputs.
  *
  * @returns Parsed and validated inputs
  */
 export function getInputs(): Inputs {
-  const tagsInput: string = core.getInput('tags', { required: true })
+  const tagsInput: string = core.getInput('tags')
+  const deriveFrom: string = core.getInput('derive_from')
+  const deriveFromTemplate: string =
+    core.getInput('derive_from_template') || DEFAULT_DERIVE_FROM_TEMPLATE
   const defaultRef: string = core.getInput('ref')
   const whenExistsInput = core.getInput('when_exists') || 'update'
   const whenExists = validateWhenExists(whenExistsInput)
   const annotation: string = core.getInput('annotation')
+  const dryRun: boolean = core.getBooleanInput('dry_run')
   const token: string = core.getInput('github_token', {
     required: true
   })
 
   const { owner, repo } = github.context.repo
 
-  // Parse tags as CSV/newline delimited strings
-  const tags = (
-    parse(tagsInput, {
-      delimiter: ',',
-      trim: true,
-      relax_column_count: true
-    }) as string[][]
-  ).flat()
+  // Parse explicit tags as CSV/newline delimited strings
+  const explicitTags: string[] = tagsInput
+    ? (
+        parse(tagsInput, {
+          delimiter: ',',
+          trim: true,
+          relax_column_count: true
+        }) as string[][]
+      ).flat()
+    : []
+
+  // Derive tags from semver version string if provided
+  const derivedTags: string[] = deriveFrom
+    ? deriveTags(deriveFrom, deriveFromTemplate)
+    : []
+
+  // Combine explicit and derived tags
+  const tags = [...explicitTags, ...derivedTags]
+
+  // Validate that at least one tag source is provided
+  if (tags.length === 0) {
+    throw new Error(
+      "No tags specified. Provide 'tags' input, 'derive_from' input, or both."
+    )
+  }
 
   return {
     tags,
     defaultRef,
     whenExists,
     annotation,
+    dryRun,
     owner,
     repo,
     token

src/logger.ts

@@ -0,0 +1,47 @@
+import * as core from '@actions/core'
+import type { AnnotationProperties } from '@actions/core'
+
+/**
+ * Logger interface that mirrors @actions/core logging functions.
+ */
+export interface Logger {
+  debug: (message: string) => void
+  info: (message: string) => void
+  notice: (message: string | Error, properties?: AnnotationProperties) => void
+  warning: (message: string | Error, properties?: AnnotationProperties) => void
+  error: (message: string | Error, properties?: AnnotationProperties) => void
+}
+
+/**
+ * Create a logger that optionally prefixes all messages.
+ *
+ * @param prefix - Optional prefix to prepend to all log messages
+ * @returns Logger instance with prefixed messages
+ */
+export function createLogger(prefix: string = ''): Logger {
+  const prefixMessage = (msg: string | Error): string | Error => {
+    if (!prefix) {
+      return msg
+    }
+    if (typeof msg === 'string') {
+      return `${prefix}${msg}`
+    }
+    // Wrap Error with prefixed message, preserving the original as cause
+    const wrapped = new Error(`${prefix}${msg.message}`, { cause: msg })
+    if (msg.stack) {
+      wrapped.stack = msg.stack
+    }
+    return wrapped
+  }
+
+  return {
+    debug: (message: string) => core.debug(`${prefix}${message}`),
+    info: (message: string) => core.info(`${prefix}${message}`),
+    notice: (message: string | Error, properties?: AnnotationProperties) =>
+      core.notice(prefixMessage(message), properties),
+    warning: (message: string | Error, properties?: AnnotationProperties) =>
+      core.warning(prefixMessage(message), properties),
+    error: (message: string | Error, properties?: AnnotationProperties) =>
+      core.error(prefixMessage(message), properties)
+  }
+}

src/main.ts

@@ -14,20 +14,27 @@ export async function run(): Promise<void> {
     const octokit = github.getOctokit(inputs.token)
     const operations = await planTagOperations(inputs, octokit)
 
+    if (inputs.dryRun) {
+      core.info('[dry-run] Dry-run mode enabled, no changes will be made.')
+    }
+
     const created: string[] = []
     const updated: string[] = []
     const skipped: string[] = []
 
     // Execute all planned operations.
     for (const operation of operations) {
-      await executeTagOperation(operation, octokit)
+      await executeTagOperation(operation, octokit, { dryRun: inputs.dryRun })
 
-      if (operation.operation === 'create') {
-        created.push(operation.name)
-      } else if (operation.operation === 'update') {
-        updated.push(operation.name)
-      } else if (operation.operation === 'skip') {
-        skipped.push(operation.name)
+      // Only track actual changes when not in dry-run mode
+      if (!inputs.dryRun) {
+        if (operation.operation === 'create') {
+          created.push(operation.name)
+        } else if (operation.operation === 'update') {
+          updated.push(operation.name)
+        } else if (operation.operation === 'skip') {
+          skipped.push(operation.name)
+        }
       }
     }
 

src/tags.ts

@@ -1,6 +1,6 @@
-import * as core from '@actions/core'
 import * as github from '@actions/github'
 import type { Inputs } from './inputs.js'
+import { createLogger, type Logger } from './logger.js'
 
 export interface ExistingTagInfo {
   commitSHA: string
@@ -37,12 +37,21 @@ export interface SkipOperation extends BaseOperation {
 
 export type TagOperation = CreateOperation | UpdateOperation | SkipOperation
 
-interface Context {
+export interface ExecuteOptions {
+  dryRun?: boolean
+}
+
+interface ReadContext {
   owner: string
   repo: string
   octokit: ReturnType<typeof github.getOctokit>
 }
 
+interface Context extends ReadContext {
+  dryRun: boolean
+  log: Logger
+}
+
 /**
  * Plan tag operations based on inputs.
  *
@@ -56,19 +65,18 @@ export async function planTagOperations(
 ): Promise<TagOperation[]> {
   const uniqueRefs = new Set<string>()
   const tagRefs: Record<string, string> = {}
+  const tagAnnotations: Record<string, string> = {}
 
   for (const tag of inputs.tags) {
-    const parts = tag.split(':').map((s) => s.trim())
-    if (parts.length > 2) {
-      throw new Error(
-        `Invalid tag specification '${tag}': too many colons. ` +
-          `Format should be 'tag' or 'tag:ref'.`
-      )
-    }
-    const [tagName, tagRef] = parts
+    const parts = tag.split(':')
+    const tagName = (parts[0] || '').trim()
+    const tagRef = (parts[1] || '').trim()
+    // Join remaining parts back with colons to preserve annotation content
+    const tagAnnotation = parts.slice(2).join(':').trim()
+
     if (!tagName) {
       // Skip completely empty tags, but fail on invalid ones like ":main"
-      if (tagRef) {
+      if (tagRef || tagAnnotation) {
         throw new Error(`Invalid tag: '${tag}'`)
       }
       continue
@@ -88,11 +96,14 @@ export async function planTagOperations(
     }
 
     tagRefs[tagName] = ref
+    if (tagAnnotation) {
+      tagAnnotations[tagName] = tagAnnotation
+    }
     uniqueRefs.add(ref)
   }
 
   // Pre-resolve all unique refs in parallel.
-  const ctx: Context = { owner: inputs.owner, repo: inputs.repo, octokit }
+  const ctx: ReadContext = { owner: inputs.owner, repo: inputs.repo, octokit }
   const refSHAs: Record<string, string> = {}
   await Promise.all(
     Array.from(uniqueRefs).map(async (ref) => {
@@ -106,6 +117,7 @@ export async function planTagOperations(
     tagNames.map(async (tagName) => {
       const tagRef = tagRefs[tagName]
       const sha = refSHAs[tagRef]
+      const annotation = tagAnnotations[tagName] || inputs.annotation
 
       // Check if tag already exists
       let existing: ExistingTagInfo | undefined
@@ -146,7 +158,7 @@ export async function planTagOperations(
         return {
           ...baseOp,
           operation: 'create',
-          annotation: inputs.annotation
+          annotation
         } as CreateOperation
       }
 
@@ -163,7 +175,7 @@ export async function planTagOperations(
       // whenExists === 'update' - check if update is needed
       const { commitMatches, annotationMatches } = compareTagState(
         sha,
-        inputs.annotation,
+        annotation,
         existing
       )
 
@@ -177,11 +189,11 @@ export async function planTagOperations(
       }
 
       // Plan update with reasons
-      const reasons = getUpdateReasons(sha, inputs.annotation, existing)
+      const reasons = getUpdateReasons(sha, annotation, existing)
       return {
         ...baseOp,
         operation: 'update',
-        annotation: inputs.annotation,
+        annotation,
         existingSHA: existing.commitSHA,
         existingIsAnnotated: existing.isAnnotated,
         reasons
@@ -197,26 +209,24 @@ export async function planTagOperations(
  *
  * @param operation - The planned tag operation to execute
  * @param octokit - GitHub API client
+ * @param options - Execution options (e.g., dryRun)
  */
 export async function executeTagOperation(
   operation: TagOperation,
-  octokit: ReturnType<typeof github.getOctokit>
+  octokit: ReturnType<typeof github.getOctokit>,
+  options: ExecuteOptions = {}
 ): Promise<void> {
+  const dryRun = options.dryRun ?? false
   const ctx: Context = {
     owner: operation.owner,
     repo: operation.repo,
-    octokit
+    octokit,
+    dryRun,
+    log: createLogger(dryRun ? '[dry-run] ' : '')
   }
 
   if (operation.operation === 'skip') {
-    if (operation.reason === 'when_exists_skip') {
-      core.info(`Tag '${operation.name}' exists, skipping.`)
-    } else {
-      core.info(
-        `Tag '${operation.name}' already exists with desired commit SHA ${operation.sha}` +
-          (operation.existingIsAnnotated ? ' (annotated).' : '.')
-      )
-    }
+    logSkipOperation(ctx, operation)
     return
   }
 
@@ -235,15 +245,30 @@ export async function executeTagOperation(
   )
 }
 
+/**
+ * Log a skip operation.
+ */
+function logSkipOperation(ctx: Context, operation: SkipOperation): void {
+  if (operation.reason === 'when_exists_skip') {
+    ctx.log.info(`Tag '${operation.name}' exists, skipping.`)
+  } else {
+    ctx.log.info(
+      `Tag '${operation.name}' already exists with desired ` +
+        `commit SHA ${operation.sha}` +
+        (operation.existingIsAnnotated ? ' (annotated).' : '.')
+    )
+  }
+}
+
 /**
  * Fetch information about an existing tag, dereferencing if annotated.
  *
- * @param ctx - Operation context
+ * @param ctx - Read-only operation context
  * @param tagName - The name of the tag to fetch
  * @returns Information about the existing tag
  */
 async function fetchTagInfo(
-  ctx: Context,
+  ctx: ReadContext,
   tagName: string
 ): Promise<ExistingTagInfo> {
   const ref = await ctx.octokit.rest.git.getRef({
@@ -278,11 +303,11 @@ async function fetchTagInfo(
 /**
  * Resolve a ref to a SHA.
  *
- * @param ctx - Operation context
+ * @param ctx - Read-only operation context
  * @param ref - The ref to resolve
  * @returns The SHA
  */
-async function resolveRefToSha(ctx: Context, ref: string): Promise<string> {
+async function resolveRefToSha(ctx: ReadContext, ref: string): Promise<string> {
   try {
     const {
       data: { sha }
@@ -306,19 +331,24 @@ async function updateExistingTag(
   operation: UpdateOperation
 ): Promise<void> {
   const commitMatches = operation.existingSHA === operation.sha
+  const verb = ctx.dryRun ? 'Would update' : 'Updating'
 
   if (commitMatches) {
-    core.info(
-      `Tag '${operation.name}' exists with same commit but ${operation.reasons.join(', ')}.`
+    ctx.log.info(
+      `${verb} tag '${operation.name}', ${operation.reasons.join(', ')}.`
     )
   } else {
-    core.info(
-      `Tag '${operation.name}' exists` +
-        `${operation.existingIsAnnotated ? ' (annotated)' : ''}` +
-        `, updating to ${operation.reasons.join(', ')}.`
+    ctx.log.info(
+      `${verb} tag '${operation.name}'` +
+        `${operation.existingIsAnnotated ? ' (annotated)' : ''} ` +
+        `to ${operation.reasons.join(', ')}.`
     )
   }
 
+  if (ctx.dryRun) {
+    return
+  }
+
   const targetSha = await resolveTargetSHA(
     ctx,
     operation.name,
@@ -342,10 +372,16 @@ async function createTag(
   ctx: Context,
   operation: CreateOperation
 ): Promise<void> {
-  core.info(
-    `Tag '${operation.name}' does not exist, creating with commit SHA ${operation.sha}.`
+  const verb = ctx.dryRun ? 'Would create' : 'Creating'
+  ctx.log.info(
+    `${verb} tag '${operation.name}' at commit SHA ${operation.sha}` +
+      (operation.annotation ? ' (annotated).' : '.')
   )
 
+  if (ctx.dryRun) {
+    return
+  }
+
   const targetSha = await resolveTargetSHA(
     ctx,
     operation.name,
@@ -364,14 +400,14 @@ async function createTag(
 /**
  * Resolve the target SHA for a tag (creates annotated tag object if needed).
  *
- * @param ctx - Operation context
+ * @param ctx - Read-only operation context
  * @param tagName - The tag name
  * @param commitSha - The commit SHA
  * @param annotation - The annotation message (if any)
  * @returns The SHA to use (tag object SHA if annotated, commit SHA otherwise)
  */
 async function resolveTargetSHA(
-  ctx: Context,
+  ctx: ReadContext,
   tagName: string,
   commitSha: string,
   annotation: string

tests/derive.test.ts

@@ -0,0 +1,420 @@
+/**
+ * Unit tests for the derive module, src/derive.ts
+ */
+import { parseSemver, renderTemplate, deriveTags } from '../src/derive.js'
+
+describe('parseSemver', () => {
+  it('parses simple version without prefix', () => {
+    const result = parseSemver('1.2.3')
+    expect(result).toEqual({
+      prefix: '',
+      major: 1,
+      minor: 2,
+      patch: 3,
+      prerelease: '',
+      build: '',
+      version: '1.2.3'
+    })
+  })
+
+  it('parses version with v prefix', () => {
+    const result = parseSemver('v1.2.3')
+    expect(result).toEqual({
+      prefix: 'v',
+      major: 1,
+      minor: 2,
+      patch: 3,
+      prerelease: '',
+      build: '',
+      version: '1.2.3'
+    })
+  })
+
+  it('parses version with uppercase V prefix', () => {
+    const result = parseSemver('V1.2.3')
+    expect(result).toEqual({
+      prefix: 'V',
+      major: 1,
+      minor: 2,
+      patch: 3,
+      prerelease: '',
+      build: '',
+      version: '1.2.3'
+    })
+  })
+
+  it('parses version with prerelease', () => {
+    const result = parseSemver('v1.0.0-beta.1')
+    expect(result).toEqual({
+      prefix: 'v',
+      major: 1,
+      minor: 0,
+      patch: 0,
+      prerelease: 'beta.1',
+      build: '',
+      version: '1.0.0-beta.1'
+    })
+  })
+
+  it('parses version with build metadata', () => {
+    const result = parseSemver('v1.0.0+build.456')
+    expect(result).toEqual({
+      prefix: 'v',
+      major: 1,
+      minor: 0,
+      patch: 0,
+      prerelease: '',
+      build: 'build.456',
+      version: '1.0.0'
+    })
+  })
+
+  it('parses version with both prerelease and build metadata', () => {
+    const result = parseSemver('v1.2.3-alpha.1+build.789')
+    expect(result).toEqual({
+      prefix: 'v',
+      major: 1,
+      minor: 2,
+      patch: 3,
+      prerelease: 'alpha.1',
+      build: 'build.789',
+      version: '1.2.3-alpha.1'
+    })
+  })
+
+  it('handles whitespace around version string', () => {
+    const result = parseSemver('  v1.2.3  ')
+    expect(result).toEqual({
+      prefix: 'v',
+      major: 1,
+      minor: 2,
+      patch: 3,
+      prerelease: '',
+      build: '',
+      version: '1.2.3'
+    })
+  })
+
+  it('throws on empty string', () => {
+    expect(() => parseSemver('')).toThrow('Invalid semver: empty string')
+  })
+
+  it('throws on whitespace only', () => {
+    expect(() => parseSemver('   ')).toThrow('Invalid semver: empty string')
+  })
+
+  it('throws on invalid semver', () => {
+    expect(() => parseSemver('not-a-version')).toThrow(
+      "Invalid semver: 'not-a-version'"
+    )
+  })
+
+  it('throws on incomplete version', () => {
+    expect(() => parseSemver('v1.2')).toThrow("Invalid semver: 'v1.2'")
+  })
+})
+
+describe('renderTemplate', () => {
+  const ctx = {
+    prefix: 'v',
+    major: 1,
+    minor: 2,
+    patch: 3,
+    prerelease: 'beta.1',
+    build: 'build.456',
+    version: '1.2.3-beta.1'
+  }
+
+  it('renders prefix placeholder', () => {
+    expect(renderTemplate('{{prefix}}', ctx)).toBe('v')
+  })
+
+  it('renders major placeholder', () => {
+    expect(renderTemplate('{{major}}', ctx)).toBe('1')
+  })
+
+  it('renders minor placeholder', () => {
+    expect(renderTemplate('{{minor}}', ctx)).toBe('2')
+  })
+
+  it('renders patch placeholder', () => {
+    expect(renderTemplate('{{patch}}', ctx)).toBe('3')
+  })
+
+  it('renders prerelease placeholder', () => {
+    expect(renderTemplate('{{prerelease}}', ctx)).toBe('beta.1')
+  })
+
+  it('renders build placeholder', () => {
+    expect(renderTemplate('{{build}}', ctx)).toBe('build.456')
+  })
+
+  it('renders version placeholder', () => {
+    expect(renderTemplate('{{version}}', ctx)).toBe('1.2.3-beta.1')
+  })
+
+  it('renders multiple placeholders', () => {
+    expect(renderTemplate('{{prefix}}{{major}}.{{minor}}', ctx)).toBe('v1.2')
+  })
+
+  it('renders same placeholder multiple times', () => {
+    expect(renderTemplate('{{major}}-{{major}}', ctx)).toBe('1-1')
+  })
+
+  it('preserves text without placeholders', () => {
+    expect(renderTemplate('latest', ctx)).toBe('latest')
+  })
+
+  it('handles empty prefix', () => {
+    const noPrefix = { ...ctx, prefix: '' }
+    expect(renderTemplate('{{prefix}}{{major}}', noPrefix)).toBe('1')
+  })
+
+  it('handles empty prerelease', () => {
+    const noPrerelease = { ...ctx, prerelease: '' }
+    expect(renderTemplate('{{major}}-{{prerelease}}', noPrerelease)).toBe('1-')
+  })
+
+  describe('Handlebars conditionals', () => {
+    it('renders {{#if}} section when variable has value', () => {
+      expect(
+        renderTemplate('{{major}}{{#if prerelease}}-{{prerelease}}{{/if}}', ctx)
+      ).toBe('1-beta.1')
+    })
+
+    it('omits {{#if}} section when variable is empty', () => {
+      const noPrerelease = { ...ctx, prerelease: '' }
+      expect(
+        renderTemplate(
+          '{{major}}{{#if prerelease}}-{{prerelease}}{{/if}}',
+          noPrerelease
+        )
+      ).toBe('1')
+    })
+
+    it('handles {{#if}} with zero-valued numbers (converted to strings)', () => {
+      const zeroMinor = { ...ctx, minor: 0 }
+      expect(
+        renderTemplate('{{major}}{{#if minor}}.{{minor}}{{/if}}', zeroMinor)
+      ).toBe('1.0')
+    })
+
+    it('handles nested conditionals', () => {
+      expect(
+        renderTemplate(
+          '{{major}}{{#if prerelease}}-{{prerelease}}{{#if build}}+{{build}}{{/if}}{{/if}}',
+          ctx
+        )
+      ).toBe('1-beta.1+build.456')
+    })
+
+    it('handles nested conditionals with inner empty', () => {
+      const noBuild = { ...ctx, build: '' }
+      expect(
+        renderTemplate(
+          '{{major}}{{#if prerelease}}-{{prerelease}}{{#if build}}+{{build}}{{/if}}{{/if}}',
+          noBuild
+        )
+      ).toBe('1-beta.1')
+    })
+
+    it('handles {{#unless}} for inverse logic', () => {
+      const noPrerelease = { ...ctx, prerelease: '' }
+      expect(
+        renderTemplate('{{major}}{{#unless prerelease}}-stable{{/unless}}', ctx)
+      ).toBe('1')
+      expect(
+        renderTemplate(
+          '{{major}}{{#unless prerelease}}-stable{{/unless}}',
+          noPrerelease
+        )
+      ).toBe('1-stable')
+    })
+
+    it('handles multiple {{#if}} sections', () => {
+      const noBuild = { ...ctx, build: '' }
+      expect(
+        renderTemplate(
+          '{{major}}{{#if prerelease}}-{{prerelease}}{{/if}}{{#if build}}+{{build}}{{/if}}',
+          noBuild
+        )
+      ).toBe('1-beta.1')
+    })
+  })
+})
+
+describe('deriveTags', () => {
+  it('generates tags with default-style template', () => {
+    const result = deriveTags(
+      'v1.2.3',
+      '{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}'
+    )
+    expect(result).toEqual(['v1', 'v1.2'])
+  })
+
+  it('generates single tag from simple template', () => {
+    const result = deriveTags('v1.2.3', '{{prefix}}{{major}}')
+    expect(result).toEqual(['v1'])
+  })
+
+  it('handles version without prefix', () => {
+    const result = deriveTags(
+      '1.2.3',
+      '{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}'
+    )
+    expect(result).toEqual(['1', '1.2'])
+  })
+
+  it('handles prerelease in template', () => {
+    const result = deriveTags(
+      'v1.0.0-rc.1',
+      '{{prefix}}{{major}}-{{prerelease}}'
+    )
+    expect(result).toEqual(['v1-rc.1'])
+  })
+
+  it('filters empty tags and prefix-only tags from result', () => {
+    const result = deriveTags('v1.2.3', '{{prefix}}{{major}},,{{prefix}}')
+    expect(result).toEqual(['v1'])
+  })
+
+  it('trims whitespace around template parts', () => {
+    const result = deriveTags('v1.2.3', '  {{prefix}}{{major}}  ,  latest  ')
+    expect(result).toEqual(['v1', 'latest'])
+  })
+
+  it('generates full version tag', () => {
+    const result = deriveTags('v1.2.3', '{{prefix}}{{version}}')
+    expect(result).toEqual(['v1.2.3'])
+  })
+
+  it('throws on invalid semver', () => {
+    expect(() => deriveTags('invalid', '{{major}}')).toThrow(
+      "Invalid semver: 'invalid'"
+    )
+  })
+
+  it('handles newline-delimited template', () => {
+    const result = deriveTags(
+      'v1.2.3',
+      '{{prefix}}{{major}}\n{{prefix}}{{major}}.{{minor}}'
+    )
+    expect(result).toEqual(['v1', 'v1.2'])
+  })
+
+  it('handles mixed newlines and commas in template', () => {
+    const result = deriveTags(
+      'v1.2.3',
+      '{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}\nlatest'
+    )
+    expect(result).toEqual(['v1', 'v1.2', 'latest'])
+  })
+
+  describe('with Handlebars conditionals', () => {
+    it('generates tag with optional prerelease when present', () => {
+      const result = deriveTags(
+        'v1.0.0-beta.1',
+        '{{prefix}}{{major}}{{#if prerelease}}-{{prerelease}}{{/if}}'
+      )
+      expect(result).toEqual(['v1-beta.1'])
+    })
+
+    it('generates tag without prerelease section when absent', () => {
+      const result = deriveTags(
+        'v1.0.0',
+        '{{prefix}}{{major}}{{#if prerelease}}-{{prerelease}}{{/if}}'
+      )
+      expect(result).toEqual(['v1'])
+    })
+
+    it('generates multiple tags with conditionals', () => {
+      const result = deriveTags(
+        'v1.2.3-rc.1',
+        '{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}{{#if prerelease}}-{{prerelease}}{{/if}}'
+      )
+      expect(result).toEqual(['v1', 'v1.2-rc.1'])
+    })
+
+    it('handles build metadata conditional', () => {
+      const result = deriveTags(
+        'v1.0.0+build.123',
+        '{{prefix}}{{major}}{{#if build}}+{{build}}{{/if}}'
+      )
+      expect(result).toEqual(['v1+build.123'])
+    })
+
+    it('handles both prerelease and build conditionals', () => {
+      const result = deriveTags(
+        'v1.0.0-alpha.1+build.789',
+        '{{prefix}}{{major}}{{#if prerelease}}-{{prerelease}}{{/if}}{{#if build}}+{{build}}{{/if}}'
+      )
+      expect(result).toEqual(['v1-alpha.1+build.789'])
+    })
+  })
+
+  describe('conditional tag inclusion', () => {
+    it('includes latest tag only for stable releases', () => {
+      // Stable release gets latest tag
+      const stable = deriveTags(
+        'v1.2.3',
+        '{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}{{#unless prerelease}},latest{{/unless}}'
+      )
+      expect(stable).toEqual(['v1', 'v1.2', 'latest'])
+
+      // Prerelease does not get latest tag
+      const prerelease = deriveTags(
+        'v1.2.3-beta.1',
+        '{{prefix}}{{major}},{{prefix}}{{major}}.{{minor}}{{#unless prerelease}},latest{{/unless}}'
+      )
+      expect(prerelease).toEqual(['v1', 'v1.2'])
+    })
+
+    it('conditionally includes entire tag group with {{#if}}', () => {
+      // With prerelease: include prerelease-specific tags
+      const withPre = deriveTags(
+        'v2.0.0-rc.1',
+        '{{prefix}}{{major}}{{#if prerelease}},{{prefix}}{{major}}-{{prerelease}}{{/if}}'
+      )
+      expect(withPre).toEqual(['v2', 'v2-rc.1'])
+
+      // Without prerelease: only major tag
+      const withoutPre = deriveTags(
+        'v2.0.0',
+        '{{prefix}}{{major}}{{#if prerelease}},{{prefix}}{{major}}-{{prerelease}}{{/if}}'
+      )
+      expect(withoutPre).toEqual(['v2'])
+    })
+
+    it('conditionally includes newline-separated tags', () => {
+      // Stable release includes all tags
+      const stable = deriveTags(
+        'v1.0.0',
+        '{{prefix}}{{major}}\n{{prefix}}{{major}}.{{minor}}{{#unless prerelease}}\nstable{{/unless}}'
+      )
+      expect(stable).toEqual(['v1', 'v1.0', 'stable'])
+
+      // Prerelease excludes stable tag
+      const prerelease = deriveTags(
+        'v1.0.0-alpha.1',
+        '{{prefix}}{{major}}\n{{prefix}}{{major}}.{{minor}}{{#unless prerelease}}\nstable{{/unless}}'
+      )
+      expect(prerelease).toEqual(['v1', 'v1.0'])
+    })
+
+    it('excludes multiple tags conditionally', () => {
+      const result = deriveTags(
+        'v1.0.0-beta.1',
+        '{{prefix}}{{major}}{{#unless prerelease}},latest,stable,production{{/unless}}'
+      )
+      expect(result).toEqual(['v1'])
+    })
+
+    it('includes multiple tags conditionally for stable', () => {
+      const result = deriveTags(
+        'v1.0.0',
+        '{{prefix}}{{major}}{{#unless prerelease}},latest,stable,production{{/unless}}'
+      )
+      expect(result).toEqual(['v1', 'latest', 'stable', 'production'])
+    })
+  })
+})

tests/fixtures/core.ts

@@ -4,7 +4,9 @@ import { jest } from '@jest/globals'
 export const debug = jest.fn<typeof core.debug>()
 export const error = jest.fn<typeof core.error>()
 export const info = jest.fn<typeof core.info>()
+export const notice = jest.fn<typeof core.notice>()
 export const getInput = jest.fn<typeof core.getInput>()
+export const getBooleanInput = jest.fn<typeof core.getBooleanInput>()
 export const setOutput = jest.fn<typeof core.setOutput>()
 export const setFailed = jest.fn<typeof core.setFailed>()
 export const warning = jest.fn<typeof core.warning>()

tests/logger.test.ts

@@ -0,0 +1,193 @@
+/**
+ * Unit tests for the logger module, src/logger.ts
+ */
+import { jest } from '@jest/globals'
+import * as core from './fixtures/core.js'
+
+jest.unstable_mockModule('@actions/core', () => core)
+
+const { createLogger } = await import('../src/logger.js')
+
+describe('createLogger', () => {
+  beforeEach(() => {
+    jest.resetAllMocks()
+  })
+
+  describe('without prefix', () => {
+    it('calls core.debug with the message', () => {
+      const log = createLogger()
+      log.debug('test debug message')
+      expect(core.debug).toHaveBeenCalledWith('test debug message')
+    })
+
+    it('calls core.info with the message', () => {
+      const log = createLogger()
+      log.info('test info message')
+      expect(core.info).toHaveBeenCalledWith('test info message')
+    })
+
+    it('calls core.notice with string message', () => {
+      const log = createLogger()
+      log.notice('test notice message')
+      expect(core.notice).toHaveBeenCalledWith('test notice message', undefined)
+    })
+
+    it('calls core.notice with Error unchanged', () => {
+      const log = createLogger()
+      const error = new Error('test error')
+      log.notice(error)
+      expect(core.notice).toHaveBeenCalledWith(error, undefined)
+    })
+
+    it('calls core.notice with properties', () => {
+      const log = createLogger()
+      const props = { title: 'Notice Title' }
+      log.notice('test notice', props)
+      expect(core.notice).toHaveBeenCalledWith('test notice', props)
+    })
+
+    it('calls core.warning with string message', () => {
+      const log = createLogger()
+      log.warning('test warning message')
+      expect(core.warning).toHaveBeenCalledWith(
+        'test warning message',
+        undefined
+      )
+    })
+
+    it('calls core.warning with Error unchanged', () => {
+      const log = createLogger()
+      const error = new Error('warning error')
+      log.warning(error)
+      expect(core.warning).toHaveBeenCalledWith(error, undefined)
+    })
+
+    it('calls core.warning with properties', () => {
+      const log = createLogger()
+      const props = { title: 'Warning Title' }
+      log.warning('test warning', props)
+      expect(core.warning).toHaveBeenCalledWith('test warning', props)
+    })
+
+    it('calls core.error with string message', () => {
+      const log = createLogger()
+      log.error('test error message')
+      expect(core.error).toHaveBeenCalledWith('test error message', undefined)
+    })
+
+    it('calls core.error with Error unchanged', () => {
+      const log = createLogger()
+      const error = new Error('error error')
+      log.error(error)
+      expect(core.error).toHaveBeenCalledWith(error, undefined)
+    })
+
+    it('calls core.error with properties', () => {
+      const log = createLogger()
+      const props = { title: 'Error Title' }
+      log.error('test error', props)
+      expect(core.error).toHaveBeenCalledWith('test error', props)
+    })
+  })
+
+  describe('with prefix', () => {
+    it('prefixes debug messages', () => {
+      const log = createLogger('[dry-run] ')
+      log.debug('test debug message')
+      expect(core.debug).toHaveBeenCalledWith('[dry-run] test debug message')
+    })
+
+    it('prefixes info messages', () => {
+      const log = createLogger('[dry-run] ')
+      log.info('test info message')
+      expect(core.info).toHaveBeenCalledWith('[dry-run] test info message')
+    })
+
+    it('prefixes notice string messages', () => {
+      const log = createLogger('[dry-run] ')
+      log.notice('test notice message')
+      expect(core.notice).toHaveBeenCalledWith(
+        '[dry-run] test notice message',
+        undefined
+      )
+    })
+
+    it('wraps notice Error with prefixed message and cause', () => {
+      const log = createLogger('[dry-run] ')
+      const original = new Error('notice error')
+      log.notice(original)
+
+      expect(core.notice).toHaveBeenCalledTimes(1)
+      const [wrapped, props] = core.notice.mock.calls[0]
+      expect(wrapped).toBeInstanceOf(Error)
+      expect((wrapped as Error).message).toBe('[dry-run] notice error')
+      expect((wrapped as Error).cause).toBe(original)
+      expect((wrapped as Error).stack).toBe(original.stack)
+      expect(props).toBeUndefined()
+    })
+
+    it('prefixes warning string messages', () => {
+      const log = createLogger('[dry-run] ')
+      log.warning('test warning message')
+      expect(core.warning).toHaveBeenCalledWith(
+        '[dry-run] test warning message',
+        undefined
+      )
+    })
+
+    it('wraps warning Error with prefixed message and cause', () => {
+      const log = createLogger('[dry-run] ')
+      const original = new Error('warning error')
+      log.warning(original)
+
+      expect(core.warning).toHaveBeenCalledTimes(1)
+      const [wrapped, props] = core.warning.mock.calls[0]
+      expect(wrapped).toBeInstanceOf(Error)
+      expect((wrapped as Error).message).toBe('[dry-run] warning error')
+      expect((wrapped as Error).cause).toBe(original)
+      expect((wrapped as Error).stack).toBe(original.stack)
+      expect(props).toBeUndefined()
+    })
+
+    it('prefixes error string messages', () => {
+      const log = createLogger('[dry-run] ')
+      log.error('test error message')
+      expect(core.error).toHaveBeenCalledWith(
+        '[dry-run] test error message',
+        undefined
+      )
+    })
+
+    it('wraps error Error with prefixed message and cause', () => {
+      const log = createLogger('[dry-run] ')
+      const original = new Error('error error')
+      log.error(original)
+
+      expect(core.error).toHaveBeenCalledTimes(1)
+      const [wrapped, props] = core.error.mock.calls[0]
+      expect(wrapped).toBeInstanceOf(Error)
+      expect((wrapped as Error).message).toBe('[dry-run] error error')
+      expect((wrapped as Error).cause).toBe(original)
+      expect((wrapped as Error).stack).toBe(original.stack)
+      expect(props).toBeUndefined()
+    })
+
+    it('preserves properties when prefixing', () => {
+      const log = createLogger('[test] ')
+      const props = { title: 'Test Title', file: 'test.ts', startLine: 10 }
+      log.warning('message with props', props)
+      expect(core.warning).toHaveBeenCalledWith(
+        '[test] message with props',
+        props
+      )
+    })
+  })
+
+  describe('with empty prefix', () => {
+    it('behaves the same as no prefix', () => {
+      const log = createLogger('')
+      log.info('test message')
+      expect(core.info).toHaveBeenCalledWith('test message')
+    })
+  })
+})

tests/main.test.ts

@@ -16,9 +16,14 @@ jest.unstable_mockModule('csv-parse/sync', () => csvParse)
 const { run } = await import('../src/main.js')
 
 // Helper functions for cleaner test setup
-const setupInputs = (inputs: Record<string, string>): void => {
+const setupInputs = (inputs: Record<string, string | boolean>): void => {
   core.getInput.mockImplementation((name: string) => {
-    return inputs[name] || ''
+    const value = inputs[name]
+    return typeof value === 'string' ? value : ''
+  })
+  core.getBooleanInput.mockImplementation((name: string) => {
+    const value = inputs[name]
+    return typeof value === 'boolean' ? value : false
   })
 }
 
@@ -123,7 +128,7 @@ describe('run', () => {
     })
 
     expect(core.info).toHaveBeenCalledWith(
-      "Tag 'v1' does not exist, creating with commit SHA sha-abc123."
+      "Creating tag 'v1' at commit SHA sha-abc123."
     )
     expect(getOutputs()).toEqual({
       created: ['v1', 'v1.0'],
@@ -155,7 +160,7 @@ describe('run', () => {
     })
 
     expect(core.info).toHaveBeenCalledWith(
-      "Tag 'v1' exists, updating to commit SHA sha-def456 (was sha-old123)."
+      "Updating tag 'v1' to commit SHA sha-def456 (was sha-old123)."
     )
     expect(getOutputs()).toEqual({
       created: [],
@@ -533,22 +538,42 @@ describe('run', () => {
     })
   })
 
-  it('fails when tag specification has multiple colons', async () => {
+  it('creates annotated tag with per-tag annotation syntax', async () => {
     setupInputs({
-      tags: 'stable:refs/heads/main:latest',
+      tags: 'stable:refs/heads/main:Release annotation',
       ref: '',
       github_token: 'test-token',
       when_exists: 'update'
     })
+    setupCommitResolver({ 'refs/heads/main': 'sha-main' })
+    setupTagDoesNotExist()
+
+    github.mockOctokit.rest.git.createTag.mockResolvedValue({
+      data: { sha: 'sha-tag-object-stable' }
+    })
 
     await run()
 
-    expect(core.setFailed).toHaveBeenCalledWith(
-      expect.stringContaining('Invalid tag specification')
-    )
-    expect(core.setFailed).toHaveBeenCalledWith(
-      expect.stringContaining('too many colons')
-    )
+    expect(github.mockOctokit.rest.git.createTag).toHaveBeenCalledWith({
+      owner: 'test-owner',
+      repo: 'test-repo',
+      tag: 'stable',
+      message: 'Release annotation',
+      object: 'sha-main',
+      type: 'commit'
+    })
+    expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+      owner: 'test-owner',
+      repo: 'test-repo',
+      ref: 'refs/tags/stable',
+      sha: 'sha-tag-object-stable'
+    })
+    expect(getOutputs()).toEqual({
+      created: ['stable'],
+      updated: [],
+      skipped: [],
+      tags: ['stable']
+    })
   })
 
   it('handles mixed scenario with multiple tags', async () => {
@@ -1219,4 +1244,645 @@ describe('run', () => {
       tags: ['v1']
     })
   })
+
+  describe('dry-run mode', () => {
+    it('logs planned creates without executing them', async () => {
+      setupInputs({
+        tags: 'v1,v1.0',
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update',
+        dry_run: true
+      })
+      setupCommitResolver('sha-abc123')
+      setupTagDoesNotExist()
+
+      await run()
+
+      // Should NOT call createRef in dry-run mode
+      expect(github.mockOctokit.rest.git.createRef).not.toHaveBeenCalled()
+
+      // Should log dry-run messages
+      expect(core.info).toHaveBeenCalledWith(
+        '[dry-run] Dry-run mode enabled, no changes will be made.'
+      )
+      expect(core.info).toHaveBeenCalledWith(
+        "[dry-run] Would create tag 'v1' at commit SHA sha-abc123."
+      )
+      expect(core.info).toHaveBeenCalledWith(
+        "[dry-run] Would create tag 'v1.0' at commit SHA sha-abc123."
+      )
+
+      // Outputs should be empty in dry-run mode
+      expect(getOutputs()).toEqual({
+        created: [],
+        updated: [],
+        skipped: [],
+        tags: []
+      })
+    })
+
+    it('logs planned updates without executing them', async () => {
+      setupInputs({
+        tags: 'v1',
+        ref: 'def456',
+        github_token: 'test-token',
+        when_exists: 'update',
+        dry_run: true
+      })
+      setupCommitResolver('sha-def456')
+      setupTagExistsForAll('sha-old123')
+
+      await run()
+
+      // Should NOT call updateRef in dry-run mode
+      expect(github.mockOctokit.rest.git.updateRef).not.toHaveBeenCalled()
+
+      // Should log dry-run messages
+      expect(core.info).toHaveBeenCalledWith(
+        '[dry-run] Dry-run mode enabled, no changes will be made.'
+      )
+      expect(core.info).toHaveBeenCalledWith(
+        "[dry-run] Would update tag 'v1' " +
+          'to commit SHA sha-def456 (was sha-old123).'
+      )
+
+      // Outputs should be empty in dry-run mode
+      expect(getOutputs()).toEqual({
+        created: [],
+        updated: [],
+        skipped: [],
+        tags: []
+      })
+    })
+
+    it('logs skipped tags with dry-run prefix', async () => {
+      setupInputs({
+        tags: 'v1',
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update',
+        dry_run: true
+      })
+      setupCommitResolver('sha-abc123')
+      setupTagExistsForAll('sha-abc123')
+
+      await run()
+
+      expect(core.info).toHaveBeenCalledWith(
+        '[dry-run] Dry-run mode enabled, no changes will be made.'
+      )
+      expect(core.info).toHaveBeenCalledWith(
+        "[dry-run] Tag 'v1' already exists with desired commit SHA sha-abc123."
+      )
+
+      expect(getOutputs()).toEqual({
+        created: [],
+        updated: [],
+        skipped: [],
+        tags: []
+      })
+    })
+
+    it('handles mixed operations in dry-run mode', async () => {
+      setupInputs({
+        tags: 'v1,v2,v3',
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update',
+        dry_run: true
+      })
+      setupCommitResolver('sha-abc123')
+
+      // v1 exists with different SHA, v2 matches, v3 doesn't exist
+      github.mockOctokit.rest.git.getRef.mockImplementation(
+        async (args: unknown) => {
+          const { ref } = args as { ref: string }
+          if (ref === 'tags/v1') {
+            return {
+              data: {
+                ref: 'refs/tags/v1',
+                object: { sha: 'sha-old', type: 'commit' }
+              }
+            }
+          }
+          if (ref === 'tags/v2') {
+            return {
+              data: {
+                ref: 'refs/tags/v2',
+                object: { sha: 'sha-abc123', type: 'commit' }
+              }
+            }
+          }
+          throw { status: 404 }
+        }
+      )
+
+      await run()
+
+      // No actual operations should happen
+      expect(github.mockOctokit.rest.git.createRef).not.toHaveBeenCalled()
+      expect(github.mockOctokit.rest.git.updateRef).not.toHaveBeenCalled()
+
+      // Should log all planned operations
+      expect(core.info).toHaveBeenCalledWith(
+        '[dry-run] Dry-run mode enabled, no changes will be made.'
+      )
+      expect(core.info).toHaveBeenCalledWith(
+        "[dry-run] Would update tag 'v1' to commit SHA sha-abc123 (was sha-old)."
+      )
+      expect(core.info).toHaveBeenCalledWith(
+        "[dry-run] Tag 'v2' already exists with desired commit SHA sha-abc123."
+      )
+      expect(core.info).toHaveBeenCalledWith(
+        "[dry-run] Would create tag 'v3' at commit SHA sha-abc123."
+      )
+
+      expect(getOutputs()).toEqual({
+        created: [],
+        updated: [],
+        skipped: [],
+        tags: []
+      })
+    })
+
+    it('logs annotated tag creation in dry-run mode', async () => {
+      setupInputs({
+        tags: 'v1',
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update',
+        annotation: 'Release v1',
+        dry_run: true
+      })
+      setupCommitResolver('sha-abc123')
+      setupTagDoesNotExist()
+
+      await run()
+
+      expect(github.mockOctokit.rest.git.createTag).not.toHaveBeenCalled()
+      expect(github.mockOctokit.rest.git.createRef).not.toHaveBeenCalled()
+
+      expect(core.info).toHaveBeenCalledWith(
+        "[dry-run] Would create tag 'v1' at commit SHA sha-abc123 (annotated)."
+      )
+
+      expect(getOutputs()).toEqual({
+        created: [],
+        updated: [],
+        skipped: [],
+        tags: []
+      })
+    })
+
+    it('executes normally when dry_run is false', async () => {
+      setupInputs({
+        tags: 'v1',
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update',
+        dry_run: false
+      })
+      setupCommitResolver('sha-abc123')
+      setupTagDoesNotExist()
+
+      await run()
+
+      // Should actually create the tag
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledTimes(1)
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/v1',
+        sha: 'sha-abc123'
+      })
+
+      expect(getOutputs()).toEqual({
+        created: ['v1'],
+        updated: [],
+        skipped: [],
+        tags: ['v1']
+      })
+    })
+  })
+
+  describe('derive_from input', () => {
+    it('derives tags from semver using default template', async () => {
+      setupInputs({
+        derive_from: 'v1.2.3',
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+      setupCommitResolver('sha-abc123')
+      setupTagDoesNotExist()
+
+      await run()
+
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledTimes(2)
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/v1',
+        sha: 'sha-abc123'
+      })
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/v1.2',
+        sha: 'sha-abc123'
+      })
+
+      expect(getOutputs()).toEqual({
+        created: ['v1', 'v1.2'],
+        updated: [],
+        skipped: [],
+        tags: ['v1', 'v1.2']
+      })
+    })
+
+    it('derives tags using custom template', async () => {
+      setupInputs({
+        derive_from: 'v2.5.0',
+        derive_from_template: '{{prefix}}{{major}}',
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+      setupCommitResolver('sha-abc123')
+      setupTagDoesNotExist()
+
+      await run()
+
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledTimes(1)
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/v2',
+        sha: 'sha-abc123'
+      })
+
+      expect(getOutputs()).toEqual({
+        created: ['v2'],
+        updated: [],
+        skipped: [],
+        tags: ['v2']
+      })
+    })
+
+    it('combines derive_from with explicit tags', async () => {
+      setupInputs({
+        tags: 'latest',
+        derive_from: 'v1.0.0',
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+      setupCommitResolver('sha-abc123')
+      setupTagDoesNotExist()
+
+      await run()
+
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledTimes(3)
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/latest',
+        sha: 'sha-abc123'
+      })
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/v1',
+        sha: 'sha-abc123'
+      })
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/v1.0',
+        sha: 'sha-abc123'
+      })
+
+      expect(getOutputs()).toEqual({
+        created: ['latest', 'v1', 'v1.0'],
+        updated: [],
+        skipped: [],
+        tags: ['latest', 'v1', 'v1.0']
+      })
+    })
+
+    it('handles version without v prefix', async () => {
+      setupInputs({
+        derive_from: '3.0.0',
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+      setupCommitResolver('sha-abc123')
+      setupTagDoesNotExist()
+
+      await run()
+
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledTimes(2)
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/3',
+        sha: 'sha-abc123'
+      })
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/3.0',
+        sha: 'sha-abc123'
+      })
+
+      expect(getOutputs()).toEqual({
+        created: ['3', '3.0'],
+        updated: [],
+        skipped: [],
+        tags: ['3', '3.0']
+      })
+    })
+
+    it('fails when neither tags nor derive_from is provided', async () => {
+      setupInputs({
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+
+      await run()
+
+      expect(core.setFailed).toHaveBeenCalledWith(
+        "No tags specified. Provide 'tags' input, 'derive_from' input, or both."
+      )
+    })
+
+    it('fails on invalid semver in derive_from', async () => {
+      setupInputs({
+        derive_from: 'not-a-version',
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+
+      await run()
+
+      expect(core.setFailed).toHaveBeenCalledWith(
+        "Invalid semver: 'not-a-version'"
+      )
+    })
+
+    it('deduplicates when tags and derive_from produce overlapping tags', async () => {
+      setupInputs({
+        tags: 'v1,v1.2',
+        derive_from: 'v1.2.3', // Derives v1 and v1.2, overlapping with explicit
+        ref: 'abc123',
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+      setupCommitResolver('sha-abc123')
+      setupTagDoesNotExist()
+
+      await run()
+
+      // Should only create 2 tags (deduplicated), not 4
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledTimes(2)
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/v1',
+        sha: 'sha-abc123'
+      })
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/v1.2',
+        sha: 'sha-abc123'
+      })
+
+      expect(getOutputs()).toEqual({
+        created: ['v1', 'v1.2'],
+        updated: [],
+        skipped: [],
+        tags: ['v1', 'v1.2']
+      })
+    })
+
+    it('fails when tags and derive_from produce same tag with different refs', async () => {
+      setupInputs({
+        tags: 'v1:main', // Explicit v1 pointing to main
+        derive_from: 'v1.2.3', // Derives v1 (using default ref)
+        ref: 'develop', // Different default ref
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+
+      await run()
+
+      expect(core.setFailed).toHaveBeenCalledWith(
+        "Duplicate tag 'v1' with different refs: 'main' and 'develop'"
+      )
+      expect(github.mockOctokit.rest.git.createRef).not.toHaveBeenCalled()
+    })
+  })
+
+  describe('per-tag annotations', () => {
+    it('creates tag with per-tag annotation using empty ref fallback', async () => {
+      setupInputs({
+        tags: 'v1::Per-tag annotation',
+        ref: 'main',
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+      setupCommitResolver('sha-main')
+      setupTagDoesNotExist()
+
+      github.mockOctokit.rest.git.createTag.mockResolvedValue({
+        data: { sha: 'sha-tag-object-v1' }
+      })
+
+      await run()
+
+      expect(github.mockOctokit.rest.git.createTag).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        tag: 'v1',
+        message: 'Per-tag annotation',
+        object: 'sha-main',
+        type: 'commit'
+      })
+      expect(github.mockOctokit.rest.git.createRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'refs/tags/v1',
+        sha: 'sha-tag-object-v1'
+      })
+      expect(getOutputs()).toEqual({
+        created: ['v1'],
+        updated: [],
+        skipped: [],
+        tags: ['v1']
+      })
+    })
+
+    it('handles per-tag annotation containing colons', async () => {
+      setupInputs({
+        tags: 'v1:main:Release: version 1.0.0: stable',
+        ref: '',
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+      setupCommitResolver({ main: 'sha-main' })
+      setupTagDoesNotExist()
+
+      github.mockOctokit.rest.git.createTag.mockResolvedValue({
+        data: { sha: 'sha-tag-object-v1' }
+      })
+
+      await run()
+
+      expect(github.mockOctokit.rest.git.createTag).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        tag: 'v1',
+        message: 'Release: version 1.0.0: stable',
+        object: 'sha-main',
+        type: 'commit'
+      })
+    })
+
+    it('mixes per-tag annotations with global annotation', async () => {
+      setupInputs({
+        tags: 'v1:main:Custom message,v2',
+        ref: 'main',
+        github_token: 'test-token',
+        when_exists: 'update',
+        annotation: 'Global annotation'
+      })
+      setupCommitResolver('sha-main')
+      setupTagDoesNotExist()
+
+      github.mockOctokit.rest.git.createTag.mockImplementation(
+        async (args: unknown) => {
+          const { tag } = args as { tag: string }
+          return { data: { sha: `sha-tag-object-${tag}` } }
+        }
+      )
+
+      await run()
+
+      expect(github.mockOctokit.rest.git.createTag).toHaveBeenCalledTimes(2)
+      expect(github.mockOctokit.rest.git.createTag).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        tag: 'v1',
+        message: 'Custom message',
+        object: 'sha-main',
+        type: 'commit'
+      })
+      expect(github.mockOctokit.rest.git.createTag).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        tag: 'v2',
+        message: 'Global annotation',
+        object: 'sha-main',
+        type: 'commit'
+      })
+    })
+
+    it('per-tag annotation overrides global annotation', async () => {
+      setupInputs({
+        tags: 'v1:main:Per-tag wins',
+        ref: 'main',
+        github_token: 'test-token',
+        when_exists: 'update',
+        annotation: 'Global annotation should be ignored'
+      })
+      setupCommitResolver('sha-main')
+      setupTagDoesNotExist()
+
+      github.mockOctokit.rest.git.createTag.mockResolvedValue({
+        data: { sha: 'sha-tag-object-v1' }
+      })
+
+      await run()
+
+      expect(github.mockOctokit.rest.git.createTag).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        tag: 'v1',
+        message: 'Per-tag wins',
+        object: 'sha-main',
+        type: 'commit'
+      })
+    })
+
+    it('updates tag when per-tag annotation differs from existing', async () => {
+      setupInputs({
+        tags: 'v1:main:New annotation',
+        ref: '',
+        github_token: 'test-token',
+        when_exists: 'update'
+      })
+      setupCommitResolver({ main: 'sha-main' })
+
+      // Tag exists as annotated with different message but same commit
+      github.mockOctokit.rest.git.getRef.mockResolvedValue({
+        data: {
+          ref: 'refs/tags/v1',
+          object: { sha: 'sha-tag-object-old', type: 'tag' }
+        }
+      })
+      github.mockOctokit.rest.git.getTag.mockResolvedValue({
+        data: {
+          sha: 'sha-tag-object-old',
+          message: 'Old annotation',
+          object: { sha: 'sha-main', type: 'commit' }
+        }
+      })
+      github.mockOctokit.rest.git.createTag.mockResolvedValue({
+        data: { sha: 'sha-tag-object-new' }
+      })
+
+      await run()
+
+      expect(github.mockOctokit.rest.git.createTag).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        tag: 'v1',
+        message: 'New annotation',
+        object: 'sha-main',
+        type: 'commit'
+      })
+      expect(github.mockOctokit.rest.git.updateRef).toHaveBeenCalledWith({
+        owner: 'test-owner',
+        repo: 'test-repo',
+        ref: 'tags/v1',
+        sha: 'sha-tag-object-new',
+        force: true
+      })
+      expect(getOutputs()).toEqual({
+        created: [],
+        updated: ['v1'],
+        skipped: [],
+        tags: ['v1']
+      })
+    })
+
+    it('fails when empty tag name with per-tag annotation', async () => {
+      setupInputs({
+        tags: '::Some annotation',
+        ref: 'main',
+        github_token: 'test-token'
+      })
+
+      await run()
+
+      expect(core.setFailed).toHaveBeenCalledWith(
+        "Invalid tag: '::Some annotation'"
+      )
+    })
+  })
 })

tests/tags.test.ts

@@ -4,14 +4,262 @@
 import { jest } from '@jest/globals'
 import * as core from './fixtures/core.js'
 import * as github from './fixtures/github.js'
+import type { Inputs } from '../src/inputs.js'
 
 // Mocks should be declared before the module being tested is imported.
 jest.unstable_mockModule('@actions/core', () => core)
 jest.unstable_mockModule('@actions/github', () => github)
 
 // The module being tested should be imported dynamically.
-const { executeTagOperation } = await import('../src/tags.js')
-import type { TagOperation } from '../src/tags.js'
+const { executeTagOperation, planTagOperations } =
+  await import('../src/tags.js')
+import type {
+  TagOperation,
+  CreateOperation,
+  UpdateOperation
+} from '../src/tags.js'
+
+// Helper to create a minimal Inputs object for testing
+const createInputs = (overrides: Partial<Inputs> = {}): Inputs => ({
+  tags: [],
+  defaultRef: 'main',
+  whenExists: 'update',
+  annotation: '',
+  dryRun: false,
+  owner: 'test-owner',
+  repo: 'test-repo',
+  token: 'test-token',
+  ...overrides
+})
+
+describe('planTagOperations', () => {
+  beforeEach(() => {
+    jest.resetAllMocks()
+    github.getOctokit.mockReturnValue(github.mockOctokit)
+  })
+
+  const setupCommitResolver = (
+    refToSha: Record<string, string> | string
+  ): void => {
+    if (typeof refToSha === 'string') {
+      github.mockOctokit.rest.repos.getCommit.mockResolvedValue({
+        data: { sha: refToSha }
+      })
+    } else {
+      github.mockOctokit.rest.repos.getCommit.mockImplementation(
+        async (args: unknown) => {
+          const { ref } = args as { ref: string }
+          const sha = refToSha[ref]
+          if (sha) return { data: { sha } }
+          throw new Error(`Unknown ref: ${ref}`)
+        }
+      )
+    }
+  }
+
+  const setupTagDoesNotExist = (): void => {
+    github.mockOctokit.rest.git.getRef.mockRejectedValue({
+      status: 404
+    })
+  }
+
+  describe('per-tag annotations', () => {
+    it('parses per-tag annotation with explicit ref', async () => {
+      const inputs = createInputs({
+        tags: ['v1:main:Custom annotation'],
+        annotation: 'Global annotation'
+      })
+      setupCommitResolver('sha-main')
+      setupTagDoesNotExist()
+
+      const operations = await planTagOperations(
+        inputs,
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        github.mockOctokit as any
+      )
+
+      expect(operations).toHaveLength(1)
+      expect(operations[0].operation).toBe('create')
+      expect((operations[0] as CreateOperation).annotation).toBe(
+        'Custom annotation'
+      )
+    })
+
+    it('parses per-tag annotation with empty ref (fallback to default)', async () => {
+      const inputs = createInputs({
+        tags: ['v1::Custom annotation'],
+        defaultRef: 'develop',
+        annotation: 'Global annotation'
+      })
+      setupCommitResolver('sha-develop')
+      setupTagDoesNotExist()
+
+      const operations = await planTagOperations(
+        inputs,
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        github.mockOctokit as any
+      )
+
+      expect(operations).toHaveLength(1)
+      expect(operations[0].operation).toBe('create')
+      expect(operations[0].ref).toBe('develop')
+      expect((operations[0] as CreateOperation).annotation).toBe(
+        'Custom annotation'
+      )
+    })
+
+    it('handles annotation containing colons', async () => {
+      const inputs = createInputs({
+        tags: ['v1:main:Release: v1.0.0'],
+        annotation: ''
+      })
+      setupCommitResolver('sha-main')
+      setupTagDoesNotExist()
+
+      const operations = await planTagOperations(
+        inputs,
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        github.mockOctokit as any
+      )
+
+      expect(operations).toHaveLength(1)
+      expect((operations[0] as CreateOperation).annotation).toBe(
+        'Release: v1.0.0'
+      )
+    })
+
+    it('falls back to global annotation when per-tag not specified', async () => {
+      const inputs = createInputs({
+        tags: ['v1', 'v2:main'],
+        annotation: 'Global annotation'
+      })
+      setupCommitResolver('sha-main')
+      setupTagDoesNotExist()
+
+      const operations = await planTagOperations(
+        inputs,
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        github.mockOctokit as any
+      )
+
+      expect(operations).toHaveLength(2)
+      expect((operations[0] as CreateOperation).annotation).toBe(
+        'Global annotation'
+      )
+      expect((operations[1] as CreateOperation).annotation).toBe(
+        'Global annotation'
+      )
+    })
+
+    it('mixes per-tag and global annotations', async () => {
+      const inputs = createInputs({
+        tags: ['v1:main:Per-tag message', 'v2'],
+        annotation: 'Global annotation'
+      })
+      setupCommitResolver('sha-main')
+      setupTagDoesNotExist()
+
+      const operations = await planTagOperations(
+        inputs,
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        github.mockOctokit as any
+      )
+
+      expect(operations).toHaveLength(2)
+      expect((operations[0] as CreateOperation).annotation).toBe(
+        'Per-tag message'
+      )
+      expect((operations[1] as CreateOperation).annotation).toBe(
+        'Global annotation'
+      )
+    })
+
+    it('uses per-tag annotation for update comparison', async () => {
+      const inputs = createInputs({
+        tags: ['v1:main:New annotation'],
+        annotation: 'Global annotation',
+        whenExists: 'update'
+      })
+      setupCommitResolver('sha-main')
+
+      // Tag exists with same commit but different annotation
+      github.mockOctokit.rest.git.getRef.mockResolvedValue({
+        data: {
+          ref: 'refs/tags/v1',
+          object: { sha: 'sha-tag-object', type: 'tag' }
+        }
+      })
+      github.mockOctokit.rest.git.getTag.mockResolvedValue({
+        data: {
+          sha: 'sha-tag-object',
+          message: 'Old annotation',
+          object: { sha: 'sha-main', type: 'commit' }
+        }
+      })
+
+      const operations = await planTagOperations(
+        inputs,
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        github.mockOctokit as any
+      )
+
+      expect(operations).toHaveLength(1)
+      expect(operations[0].operation).toBe('update')
+      expect((operations[0] as UpdateOperation).annotation).toBe(
+        'New annotation'
+      )
+      expect((operations[0] as UpdateOperation).reasons).toContain(
+        'annotation message changed'
+      )
+    })
+
+    it('skips tag when per-tag annotation matches existing', async () => {
+      const inputs = createInputs({
+        tags: ['v1:main:Same annotation'],
+        annotation: 'Global annotation',
+        whenExists: 'update'
+      })
+      setupCommitResolver('sha-main')
+
+      github.mockOctokit.rest.git.getRef.mockResolvedValue({
+        data: {
+          ref: 'refs/tags/v1',
+          object: { sha: 'sha-tag-object', type: 'tag' }
+        }
+      })
+      github.mockOctokit.rest.git.getTag.mockResolvedValue({
+        data: {
+          sha: 'sha-tag-object',
+          message: 'Same annotation',
+          object: { sha: 'sha-main', type: 'commit' }
+        }
+      })
+
+      const operations = await planTagOperations(
+        inputs,
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        github.mockOctokit as any
+      )
+
+      expect(operations).toHaveLength(1)
+      expect(operations[0].operation).toBe('skip')
+    })
+
+    it('rejects empty tag name with annotation', async () => {
+      const inputs = createInputs({
+        tags: ['::Some annotation']
+      })
+
+      await expect(
+        planTagOperations(
+          inputs,
+          // eslint-disable-next-line @typescript-eslint/no-explicit-any
+          github.mockOctokit as any
+        )
+      ).rejects.toThrow("Invalid tag: '::Some annotation'")
+    })
+  })
+})
 
 describe('executeTagOperation', () => {
   beforeEach(() => {