A .capmod is Captivity Reloaded's installable mod package. Internally it is a deterministic ZIP archive with manifest.json at its root. Use the project packager instead of assembling the archive by hand: it validates the source, rejects unsafe files, produces repeatable output, and reports the exact byte size and SHA-256 digest needed by the community catalog.

In Unity 2021.3.45f1, select Captivity Reloaded > Modding > Captivity Mod Packager.

The window supports two workflows:

The source directory must contain manifest.json directly at its root. Save the resulting package outside the source directory.

Do not create the release by selecting the mod folder in Explorer and choosing Compress to ZIP. That normally adds an extra wrapper directory, and renaming the resulting .zip to .capmod does not repair it.

Correct .capmod contents:

manifest.json
content/
assets/
levels/

Rejected wrapper layout:

my-mod/
  manifest.json
  content/
  assets/

The official packager writes the correct root layout and .capmod extension. A source ZIP may be useful for collaborators, but it is not the installable release artifact.

Choose the directory containing the pack's manifest. Validate Mod checks the manifest, declared content roots, preview files, content definitions, file types, paths, counts, and size limits. Resolve every error before building. Warnings deserve review but do not necessarily prevent packaging.

Run the packager from the same game release or source commit that the mod claims to support. During the pre-v1 freeze period, modApiVersion: 1 identifies the draft API line; it does not prove that experimental fields from two different development builds are interchangeable.

Build .capmod proposes a filename in this form:

<pack-id>-<version>.capmod

The resulting archive preserves forward-slash relative paths and assigns a fixed internal timestamp so identical source files produce reproducible package contents.

Unity assets are optional. Use them only when a portable content type cannot express the required prefab presentation.

The Mod Authoring Profile supplies:

• the loose source directory;
• the prefab assets to package;
• the Windows, Android, and WebGL targets to build.

Every packaged prefab must be a unique prefab below Assets/, have a CapmodPrefabDescriptor on its root, and use an ID in the pack namespace under prefab/.... The first public bundle slice rejects other custom MonoBehaviour scripts. This is a data-oriented asset path, not arbitrary code loading.

Do not write assetBundles into the source manifest. Build Unity .capmod builds deterministic content.bundle files, places them below bundles/<platform>/, computes their sizes and SHA-256 digests, and writes the generated declarations into the staged manifest.

Install the Unity platform modules for every selected target. Selecting an unavailable build target produces bundle.platform-module.

Installable archives accept these file extensions:

.json  .tsj  .tx  .png  .ogg  .wav  .md  .txt  .bundle

Executables, scripts, symbolic links, reparse points, absolute paths, traversal paths, duplicate paths, and undeclared bundles are rejected. An archive may contain at most 4,096 entries and at most 512 MiB after extraction. Platform-specific download limits can be lower; see Resource limits and Windows, Android, and WebGL.

Before publishing:

1. Select Validate Mod in the exact Unity project revision used to build the target game. JSON syntax checking by itself is not sufficient.
2. Resolve every error, including unknown fields and unsupported event names. Do not assume a plausible field exists because a similar field is available on another content type.
3. Build the .capmod through the packager. Do not manually ZIP or rename a ZIP.
4. Copy the .capmod into the current build's Mods directory or select it with the Mods panel Browse action.
5. Install it through the game, restart when requested, and confirm its status is Loaded.
6. Exercise the advertised content using the author test matrix.
7. Record the package's exact byte count and lowercase SHA-256 shown by the packager.
8. Install that exact final file once more. Do not test one archive and upload a rebuilt archive with a different digest.

If an AI assistant, custom generator, or third-party template produced any JSON, verify every generated property against the current field reference or authoritative schemas before publishing. Generated prose, comments, and README claims do not establish API support.

Use the validation/error-code catalog to investigate a packager or installer diagnostic.