DOCS: Add a section for which CalDAV servers have been tested

Adds tags, stored as the standard `CATEGORIES` property so they stay compatible with Nextcloud Tasks, tasks.org and DAVx⁵.

## What changed

- **Storage and sync:** tags are a new `categories` column (database v2). The migration lifts `CATEGORIES` out of the stored unknown properties for tasks that were synced before, so existing tags show up without a re-download. A line Agendula can't write back exactly as it came (e.g. a duplicated value, or the property split across several lines) stays where it was and still syncs byte for byte.
- **Provider mode (OpenTasks / tasks.org):** tags are read and written as the provider's category properties. Writes are a single batch, so a refused tag can't leave half the tags behind or create a task twice.
- **Imports:** the copy from OpenTasks/tasks.org and the legacy one-shot import both bring tags across.
- **Editor:** a new optional Tags field. Type a tag and press Done or type a comma; tags already in use are suggested while typing, and text left in the field is still saved.
- **Display:** tags show as pills on the detail screen and in each row's info line in task lists.
- **Using tags:** the home screen has a Tags section listing every tag on an open task with its count. Tapping one opens that tag's tasks across all lists, and "New task" there starts with the tag set. Every task list's sort button is now a "Sort and filter" picker, where you can tick one or more tags to narrow the list.

## Also in here

- **Keyboard:** a focused input now scrolls fully above the keyboard, not just its text line. This uses floret-kit's new `revealOnFocus` (jlmakiola/floret-kit#12), and the pointer moves to floret-kit main.
- **Edit screen:** once the title scrolls out of view, it shows in the top bar.
- **main merged in:** the branch brings main's #40 and #44 (floret-kit on its shared main, Gradle 9.8), which `release/v1.1.0` doesn't have yet.

## Where this differs from the issue

- **Filtering by several tags** shows tasks that carry *all* of them, since ticking more tags is meant to narrow the list.
- **Tags are case-sensitive:** "Work" and "work" are two tags, matching how they are stored and synced.
- **The overview** lists tags on open tasks only, the same set the editor suggests.
- **Widgets** can't be set to a tag yet.

Closes #35

Co-authored-by: Jean-Luc Makiola <business@jeanlucmakiola.de>
Reviewed-on: https://codeberg.org/jlmakiola/agendula/pulls/46

.forgejo/PULL_REQUEST_TEMPLATE.md

@@ -26,14 +26,14 @@ Which of these ran green, and anything you exercised by hand. On-device notes
 are especially useful for UI changes, and for anything touching the provider
 read/write paths (OpenTasks / tasks.org installed).
 
-  ./gradlew lintDebug :app:testDebugUnitTest :app:assembleDebug
+  ./gradlew lintFullDebug lintOfflineDebug :app:testFullDebugUnitTest :app:testOfflineDebugUnitTest :app:assembleDebug
   python3 scripts/check_translations.py
 -->
 
 
 ### Checklist
 
-- [ ] `./gradlew lintDebug :app:testDebugUnitTest :app:assembleDebug` passes locally
+- [ ] `./gradlew lintFullDebug lintOfflineDebug :app:testFullDebugUnitTest :app:testOfflineDebugUnitTest :app:assembleDebug` passes locally
 - [ ] New domain logic comes with JVM unit tests under `app/src/test/`
 - [ ] Provider details stay inside `data/tasks/`
 - [ ] No `values-*/strings.xml` touched (Weblate owns those; new English strings in `values/` are fine)

.forgejo/workflows/ci.yaml

@@ -127,10 +127,12 @@ jobs:
 
       - name: Setup Java
         if: steps.scope.outputs.code == 'true'
+        # JetBrains 21 is what gradle-daemon-jvm.properties asks for; installing it
+        # here keeps Gradle from downloading it via foojay.
         uses: actions/setup-java@v4
         with:
-          distribution: 'zulu'
-          java-version: '17'
+          distribution: 'jetbrains'
+          java-version: '21'
 
       # Fully qualified on purpose. Codeberg resolves bare `uses:` refs against
       # data.forgejo.org, Forgejo's own action mirror — actions/checkout,
@@ -178,18 +180,18 @@ jobs:
 
       # No --no-daemon: the daemon lives only as long as this job container
       # and lets the following steps skip JVM startup + reconfiguration.
-      - name: Lint (debug variant only)
+      - name: Lint (debug variants only)
         if: steps.scope.outputs.code == 'true'
-        run: ./gradlew lintDebug
+        run: ./gradlew lintFullDebug lintOfflineDebug
 
       # :dav is a plain JVM module, so it has no testDebugUnitTest — naming only
       # that task would compile the vendored suite and run none of it, which is
       # the whole safety argument in dav/PROVENANCE.md.
       - name: Unit tests
         if: steps.scope.outputs.code == 'true'
-        run: ./gradlew testDebugUnitTest :dav:test :caldav:test
+        run: ./gradlew testFullDebugUnitTest testOfflineDebugUnitTest :dav:test :caldav:test
 
-      - name: Assemble debug APK
+      - name: Assemble debug APKs
         if: steps.scope.outputs.code == 'true'
         run: ./gradlew assembleDebug
 

.forgejo/workflows/translations.yaml

@@ -2,7 +2,7 @@ name: Translations
 
 # Fast, SDK-free parity check for translation resources, so Weblate PRs (which
 # only touch values-*/strings.xml) get quick feedback without the full Android
-# build. The deeper checks still run in CI via lintDebug (ExtraTranslation).
+# build. The deeper checks still run in CI via lintFullDebug (ExtraTranslation).
 #
 # Runs on every PR (no path filter) so the required "Translations / check"
 # status is always reported — like the `ci` job. A path-filtered workflow is

.gitea/workflows/beta.yaml

@@ -3,7 +3,7 @@ name: Beta — Codeberg pre-release
 # A beta is cut by pushing a release branch whose committed versionName is
 # X.Y.Z-beta.N (see docs/RELEASING.md). Same model as release.yaml: the
 # committed version is the trigger and the vX.Y.Z-beta.N tag is an output. If
-# no tag exists for that version yet, this runs the unit tests, builds and
+# its Codeberg pre-release doesn't carry the APK yet, this runs the unit tests, builds and
 # signs the APK with the app key, records a Gitea pre-release (with the R8
 # mapping) and publishes a Codeberg pre-release with the APK + SHA-256.
 #
@@ -36,53 +36,23 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Resolve version and whether it is a new beta
+      - name: Resolve version and whether it still needs publishing
         id: v
-        env:
-          # Codeberg, not Gitea: see the same lookup in release.yaml.
-          TAG_API: https://codeberg.org/api/v1/repos/jlmakiola/agendula
         run: |
           set -e
           INFO=$(bash scripts/version_info.sh)
           echo "$INFO"
           echo "$INFO" >> "$GITHUB_OUTPUT"
-          VERSION=$(echo "$INFO" | sed -n 's/^version=//p')
-          BASE=$(echo "$INFO" | sed -n 's/^base_version=//p')
-          if [ "$(echo "$INFO" | sed -n 's/^channel=//p')" != "beta" ]; then
-            echo "versionName $VERSION is not a beta — nothing to do."
+          if [ "$(bash scripts/version_info.sh channel)" != beta ]; then
+            echo "Not a beta — nothing to do."
             echo "is_beta=false" >> "$GITHUB_OUTPUT"
             exit 0
           fi
-          # Fatal on anything but a clean 200/404, as in release.yaml: guessing
-          # "no tag" during an outage would re-cut a published beta.
-          tag_status() {
-            curl -s -o /dev/null -w '%{http_code}' "$TAG_API/git/refs/tags/$1" || echo 000
-          }
-          # A beta of a version that already shipped stable would carry a lower
-          # versionCode than the stable one: nobody could install it over it.
-          case "$(tag_status "v$BASE")" in
-            200)
-              echo "v$BASE already shipped as stable; a beta of it is pointless. Bump the version." >&2
-              exit 1 ;;
-            404) ;;
-            *) echo "Codeberg tag lookup for v$BASE failed — refusing to guess." >&2; exit 1 ;;
-          esac
-          STATUS=$(tag_status "v$VERSION")
-          case "$STATUS" in
-            200)
-              echo "Tag v$VERSION already exists on Codeberg — nothing to release."
-              echo "is_beta=false" >> "$GITHUB_OUTPUT"
-              ;;
-            404)
-              echo "No tag for v$VERSION on Codeberg yet — cutting the beta."
-              echo "is_beta=true" >> "$GITHUB_OUTPUT"
-              ;;
-            *)
-              echo "Codeberg tag lookup for v$VERSION returned HTTP $STATUS." >&2
-              echo "Refusing to guess: treating this as 'no tag' could re-cut a published beta." >&2
-              exit 1
-              ;;
-          esac
+          # Done only once its Codeberg pre-release carries the APK, so a failed
+          # publish is redone by the next push; refused unless newer than the
+          # latest stable release.
+          GATE=$(bash scripts/release_gate.sh)
+          echo "is_beta=${GATE#cut=}" >> "$GITHUB_OUTPUT"
 
   beta:
     needs: detect
@@ -100,10 +70,12 @@ jobs:
           submodules: recursive
 
       - name: Setup Java
+        # JetBrains 21 is what gradle-daemon-jvm.properties asks for; installing it
+        # here keeps Gradle from downloading it via foojay.
         uses: actions/setup-java@v4
         with:
-          distribution: 'zulu'
-          java-version: '17'
+          distribution: 'jetbrains'
+          java-version: '21'
 
       - name: Setup Android SDK
         uses: android-actions/setup-android@v3
@@ -156,7 +128,7 @@ jobs:
           grep -E 'versionName|versionCode' app/build.gradle.kts
 
       - name: Unit tests
-        run: ./gradlew testDebugUnitTest
+        run: ./gradlew testFullDebugUnitTest
 
       # The real app key, same as a stable release: a beta has to update in
       # place to the next beta and to the stable version.
@@ -175,7 +147,8 @@ jobs:
           storeFile=upload-keystore.jks
           EOF
 
-      - name: Build release APK
+      # Both flavors; the offline one goes to Codeberg only (issue #39).
+      - name: Build release APKs
         run: ./gradlew assembleRelease
 
       # Notes = a `## [X.Y.Z-beta.N]` section if there is one, else
@@ -190,7 +163,8 @@ jobs:
           bash scripts/release_notes.sh "$VERSION" > release-notes.md
           cat release-notes.md
           TAG="v$VERSION" PRERELEASE=true NOTES_FILE=release-notes.md \
-            MAPPING=app/build/outputs/mapping/release/mapping.txt \
+            MAPPING=app/build/outputs/mapping/fullRelease/mapping.txt \
+            MAPPING_OFFLINE=app/build/outputs/mapping/offlineRelease/mapping.txt \
             bash scripts/publish_gitea_release.sh
 
       # The point of the whole workflow, so NOT continue-on-error.
@@ -202,5 +176,6 @@ jobs:
         run: |
           set -e
           TAG="v$VERSION" PRERELEASE=true NOTES_FILE=release-notes.md \
-            APK=app/build/outputs/apk/release/app-release.apk \
+            APK=app/build/outputs/apk/full/release/app-full-release.apk \
+            APK_OFFLINE=app/build/outputs/apk/offline/release/app-offline-release.apk \
             bash scripts/publish_codeberg_release.sh

.gitea/workflows/release.yaml

@@ -62,17 +62,6 @@ jobs:
 
       - name: Resolve version and whether it is a new release
         id: v
-        env:
-          # Tags are read from Codeberg, which is canonical — deliberately NOT
-          # from the Gitea API this workflow runs on. The Codeberg -> Gitea sync
-          # is a push mirror, i.e. `git push --mirror`, which deletes refs the
-          # source does not have. A tag minted here on Gitea is therefore wiped
-          # by the next sync (Codeberg does not have it yet) and only reappears
-          # once the tag push at the end of this workflow propagates back.
-          # Asking Gitea inside that window would report "no tag" for a release
-          # that already shipped, and cut it a second time.
-          # Public repo, so this read needs no token.
-          TAG_API: https://codeberg.org/api/v1/repos/jlmakiola/agendula
         run: |
           set -e
           # versionName -> versionCode, channel and the pre-release flag (set
@@ -94,30 +83,11 @@ jobs:
             echo "versionName $VERSION on main is a beta. Set the stable version before merging to main." >&2
             exit 1
           fi
-          # A tag for this version already existing means the release shipped on
-          # an earlier push; do nothing. Absent => this merge cuts the release.
-          #
-          # Anything other than a clean 200/404 is treated as fatal rather than
-          # as "no tag". A Codeberg outage or a network blip would otherwise
-          # read as absent and re-cut a release that has already shipped —
-          # republishing to F-Droid. Failing here is recoverable; a duplicate
-          # release is not.
-          STATUS=$(curl -s -o /dev/null -w '%{http_code}' "$TAG_API/git/refs/tags/v$VERSION" || echo 000)
-          case "$STATUS" in
-            200)
-              echo "Tag v$VERSION already exists on Codeberg — nothing to release."
-              echo "is_release=false" >> "$GITHUB_OUTPUT"
-              ;;
-            404)
-              echo "No tag for v$VERSION on Codeberg yet — cutting the release."
-              echo "is_release=true" >> "$GITHUB_OUTPUT"
-              ;;
-            *)
-              echo "Codeberg tag lookup for v$VERSION returned HTTP $STATUS." >&2
-              echo "Refusing to guess: treating this as 'no tag' could re-cut a shipped release." >&2
-              exit 1
-              ;;
-          esac
+          # Tags are read from Codeberg, the canonical forge, by exact name: its
+          # git/refs/tags API matches by prefix, so v1.1.0-beta.1 would read as
+          # v1.1.0. A lookup error is fatal rather than read as "no tag".
+          GATE=$(bash scripts/release_gate.sh)
+          echo "is_release=${GATE#cut=}" >> "$GITHUB_OUTPUT"
 
       # Before a single Gradle task runs: F-Droid truncates the in-client
       # changelog, so an over-long one would reach users cut off mid-sentence.
@@ -150,10 +120,12 @@ jobs:
           submodules: recursive
 
       - name: Setup Java
+        # JetBrains 21 is what gradle-daemon-jvm.properties asks for; installing it
+        # here keeps Gradle from downloading it via foojay.
         uses: actions/setup-java@v4
         with:
-          distribution: 'zulu'
-          java-version: '17'
+          distribution: 'jetbrains'
+          java-version: '21'
 
       - name: Setup Android SDK
         uses: android-actions/setup-android@v3
@@ -212,7 +184,7 @@ jobs:
       # Test the exact commit being shipped (only on a real release).
       - name: Unit tests
         if: env.IS_RELEASE == 'true'
-        run: ./gradlew testDebugUnitTest
+        run: ./gradlew testFullDebugUnitTest
 
       - name: Setup Android Keystore
         if: env.IS_RELEASE == 'true'
@@ -230,7 +202,9 @@ jobs:
           storeFile=upload-keystore.jks
           EOF
 
-      - name: Build release APK
+      # Both flavors. Only full goes to F-Droid and Play; the offline one
+      # (issue #39) is a Codeberg release asset and nothing else.
+      - name: Build release APKs
         if: env.IS_RELEASE == 'true'
         run: ./gradlew assembleRelease
 
@@ -286,7 +260,7 @@ jobs:
         run: |
           set -e
           mkdir -p fdroid/repo
-          cp app/build/outputs/apk/release/app-release.apk "fdroid/repo/agendula_v${VERSION}.apk"
+          cp app/build/outputs/apk/full/release/app-full-release.apk "fdroid/repo/agendula_v${VERSION}.apk"
 
       # Per-version "What's New": ensure this version's changelog exists in the
       # fastlane tree (committed at release-cut time for the official repo; this
@@ -348,7 +322,8 @@ jobs:
           set -e
           bash scripts/release_notes.sh "$VERSION" > release-notes.md
           TAG="v$VERSION" NOTES_FILE=release-notes.md \
-            MAPPING=app/build/outputs/mapping/release/mapping.txt \
+            MAPPING=app/build/outputs/mapping/fullRelease/mapping.txt \
+            MAPPING_OFFLINE=app/build/outputs/mapping/offlineRelease/mapping.txt \
             bash scripts/publish_gitea_release.sh
 
       # Publish the release on Codeberg, which is canonical for tags and
@@ -371,7 +346,8 @@ jobs:
           set -e
           [ -s release-notes.md ] || bash scripts/release_notes.sh "$VERSION" > release-notes.md
           TAG="v$VERSION" NOTES_FILE=release-notes.md \
-            APK=app/build/outputs/apk/release/app-release.apk \
+            APK=app/build/outputs/apk/full/release/app-full-release.apk \
+            APK_OFFLINE=app/build/outputs/apk/offline/release/app-offline-release.apk \
             bash scripts/publish_codeberg_release.sh
 
       # Play takes an App Bundle, not the APK: a second artifact from the same
@@ -386,7 +362,7 @@ jobs:
       - name: Build release AAB
         if: env.IS_RELEASE == 'true'
         continue-on-error: true
-        run: ./gradlew bundleRelease
+        run: ./gradlew bundleFullRelease
 
       # NOT actions/upload-artifact@v4: its client refuses any non-github.com
       # server as unsupported GHES (go-gitea/gitea#36024). This fork drops that
@@ -398,7 +374,7 @@ jobs:
         uses: https://github.com/ChristopherHX/gitea-upload-artifact@81f940d004763f986ba3582c007fd842dd5cb0d7 # v4
         with:
           name: release-aab-${{ needs.detect.outputs.version }}
-          path: app/build/outputs/bundle/release/app-release.aab
+          path: app/build/outputs/bundle/fullRelease/app-full-release.aab
           if-no-files-found: error
           retention-days: 14
 
@@ -492,7 +468,7 @@ jobs:
         run: |
           set -euo pipefail
           # Absolute: a lane body runs from fastlane/, not the workspace root.
-          AAB="$GITHUB_WORKSPACE/dist/app-release.aab"
+          AAB="$GITHUB_WORKSPACE/dist/app-full-release.aab"
           test -f "$AAB" || { echo "No AAB at $AAB — the artifact handoff failed." >&2; ls -la dist || true; exit 1; }
           bundle exec fastlane deploy \
             aab:"$AAB" \

CHANGELOG.md

@@ -12,6 +12,11 @@ All notable changes to this project are documented here. The format follows
 - A widget can show tasks from several lists at once, optionally grouped by
   list.
 - A setting under Settings → Task form pre-fills a new task's start with today.
+- An offline version of Agendula with no sync and no network access at all,
+  published as a separate APK on Codeberg (#39).
+- Tags. Add them while editing a task, see them on the task and in lists,
+  browse them from the home screen and filter any list by them. They are saved
+  as `CATEGORIES`, so they sync with Nextcloud Tasks, tasks.org and DAVx⁵ (#35).
 
 ### Changed
 - The Tasks widget has agenda-style rows, an optional row colour and an "All
@@ -21,9 +26,15 @@ All notable changes to this project are documented here. The format follows
   showed.
 - Synced lists can be renamed and deleted, not only device-only ones. A
   read-only share shows the edit button greyed out and explains why on tap.
+- The sort button in task lists now opens "Sort and filter", which can also
+  filter by tag.
+- While editing a task, its title moves into the top bar once you scroll past
+  it.
 
 ### Fixed
 - The list editor's Where and smart-lists rows no longer have double padding.
+- A field you tap now scrolls fully above the keyboard, and the "add subtask"
+  row in task lists no longer ends up hidden behind it.
 
 ## [1.0.0] - 2026-09-21
 

CONTRIBUTING.md

@@ -28,9 +28,9 @@ layer.
 ## Build, test, lint
 
 ```sh
-./gradlew :app:assembleDebug        # build the debug APK
-./gradlew :app:testDebugUnitTest    # JVM unit tests (JUnit5 + Truth + Turbine)
-./gradlew lintDebug                 # Android lint (CI runs this on every PR)
+./gradlew :app:assembleDebug            # build the debug APKs (full + offline)
+./gradlew :app:testFullDebugUnitTest    # JVM unit tests (JUnit5 + Truth + Turbine)
+./gradlew lintFullDebug lintOfflineDebug  # Android lint (CI runs this on every PR)
 ```
 
 CI (`.forgejo/workflows/ci.yaml`, on Codeberg) runs a reproducible-release invariant check,

README.md

@@ -76,6 +76,16 @@ back to a full comparison where it does not. Everything the store does not model
 is kept verbatim and sent back unchanged, so passing your tasks through Agendula
 does not quietly lose fields another client wrote.
 
+### Tested With
+
+The following CalDAV Services have been Tested
+
+
+
+| Service | Version | Date | Status | User |
+|---|---|---|---|---|
+| **Nextcloud** | 25.0.0 | Oct 9th 2026 | ✅ | [@jlmakiola](https://codeberg.org/jlmakiola) [@Schanbro](https://codeberg.org/Schanbro)
+
 ## Where your tasks live
 
 |  | Where | Sync | Needs |
@@ -119,9 +129,21 @@ APK and a `.sha256` checksum attached — the same APK the F-Droid repository
 serves. For automatic updates from there, use
 **[Obtainium](https://github.com/ImranR98/Obtainium)** and
 **[add Agendula in one tap](https://apps.obtainium.imranr.dev/redirect?r=obtainium://add/https://codeberg.org/jlmakiola/agendula)**.
+Each release carries two APKs (see [Offline version](#offline-version)), so set
+*Filter APKs by regular expression* to `^agendula_v` to always get the regular
+app.
 Betas of upcoming versions are published there too, as pre-releases; to test
 them, switch on *Include prereleases* for Agendula in Obtainium.
 
+### Offline version
+
+Each Codeberg release also carries `agendula-offline_v<version>.apk`: Agendula
+without CalDAV sync and **without the network permission**, so it cannot
+connect to anything. It installs alongside the regular app rather than replacing
+it; move tasks between the two with Settings → Storage → Export / Import. In
+Obtainium, pick it with *Filter APKs by regular expression* set to
+`^agendula-offline_v`.
+
 ### Build from source
 
 ```sh

app/build.gradle.kts

@@ -1,3 +1,4 @@
+import com.android.build.api.artifact.SingleArtifact
 import java.util.Properties
 import java.io.FileInputStream
 
@@ -32,8 +33,8 @@ android {
         // (1.0.x: 1.0.0 -> 10000; from 1.1.0: 1.1.0-beta.1 -> 1010001,
         // 1.1.0 -> 1010099), and CI fails if the committed one doesn't match.
         // See docs/RELEASING.md.
-        versionCode = 1010001
-        versionName = "1.1.0-beta.1"
+        versionCode = 1010003
+        versionName = "1.1.0-beta.3"
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
 
@@ -46,6 +47,20 @@ android {
         resValue("string", "sync_authority", "de.jeanlucmakiola.agendula.sync")
     }
 
+    // `offline` (#39): no sync code, network libraries or network permission.
+    flavorDimensions += "network"
+    productFlavors {
+        create("full") {
+            dimension = "network"
+            buildConfigField("boolean", "SYNC_ENABLED", "true")
+        }
+        create("offline") {
+            dimension = "network"
+            applicationIdSuffix = ".offline"
+            buildConfigField("boolean", "SYNC_ENABLED", "false")
+        }
+    }
+
     signingConfigs {
         if (keystorePropertiesFile.exists()) {
             create("release") {
@@ -208,26 +223,26 @@ dependencies {
     // @HiltWorker plumbing.
     implementation(libs.androidx.work.runtime.ktx)
     // Custom Tabs: the Nextcloud login flow hands the browser an approval page.
-    implementation(libs.androidx.browser)
+    "fullImplementation"(libs.androidx.browser)
     implementation(libs.androidx.hilt.work)
     ksp(libs.androidx.hilt.compiler)
 
     // Push sync: a UnifiedPush distributor delivers the server's WebDAV-Push messages.
-    implementation(libs.unifiedpush.connector)
+    "fullImplementation"(libs.unifiedpush.connector)
 
     // RFC 5545 recurrence expansion, in-process; see the catalog for the pin.
     implementation(libs.dmfs.lib.recur)
 
     // Vendored dav4jvm — the CalDAV protocol layer. See dav/PROVENANCE.md.
-    implementation(project(":dav"))
+    "fullImplementation"(project(":dav"))
     // Discovery, auth and Nextcloud Login Flow v2.
-    implementation(project(":caldav"))
+    "fullImplementation"(project(":caldav"))
     // :dav gets org.xmlpull.v1 from the Android framework at runtime and declares
     // xpp3 compileOnly, which is not transitive. Unit tests run on a plain JVM
     // with no framework, and android.jar's stub factory returns null under
     // isReturnDefaultValues — so anything touching XmlUtils would NPE without a
     // real implementation here.
-    testImplementation(libs.xpp3)
+    "testFullImplementation"(libs.xpp3)
 
     implementation(libs.androidx.room.runtime)
     implementation(libs.androidx.room.ktx)
@@ -266,3 +281,34 @@ dependencies {
     androidTestImplementation(platform(libs.androidx.compose.bom))
     androidTestImplementation(libs.androidx.ui.test.junit4)
 }
+
+/** Fails the build if the offline flavor's merged manifest asks for the network. */
+abstract class VerifyNoNetworkPermissions : DefaultTask() {
+    @get:InputFile
+    @get:PathSensitive(PathSensitivity.NONE)
+    abstract val manifest: RegularFileProperty
+
+    @TaskAction
+    fun verify() {
+        val text = manifest.get().asFile.readText()
+        val found = listOf("INTERNET", "ACCESS_NETWORK_STATE", "ACCESS_WIFI_STATE", "CHANGE_NETWORK_STATE")
+            .filter { "\"android.permission.$it\"" in text }
+        if (found.isNotEmpty()) {
+            throw GradleException(
+                "The offline flavor's merged manifest declares ${found.joinToString()}. " +
+                    "Remove it in app/src/offline/AndroidManifest.xml with tools:node=\"remove\".",
+            )
+        }
+    }
+}
+
+androidComponents {
+    onVariants(selector().withFlavor("network" to "offline")) { variant ->
+        val name = variant.name.replaceFirstChar { it.uppercase() }
+        val verify = tasks.register<VerifyNoNetworkPermissions>("verify${name}Manifest") {
+            manifest.set(variant.artifacts.get(SingleArtifact.MERGED_MANIFEST))
+        }
+        tasks.matching { it.name in setOf("package$name", "package${name}Bundle", "check") }
+            .configureEach { dependsOn(verify) }
+    }
+}

app/schemas/de.jeanlucmakiola.agendula.data.tasks.room.TasksDatabase/2.json

@@ -0,0 +1,529 @@
+{
+  "formatVersion": 1,
+  "database": {
+    "version": 2,
+    "identityHash": "14b159c51416ba27653f6320ac7f6f03",
+    "entities": [
+      {
+        "tableName": "accounts",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `display_name` TEXT NOT NULL, `principal_url` TEXT, `home_set_url` TEXT, `username` TEXT, `last_sync_at` INTEGER, `last_sync_error` TEXT)",
+        "fields": [
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "displayName",
+            "columnName": "display_name",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "principalUrl",
+            "columnName": "principal_url",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "homeSetUrl",
+            "columnName": "home_set_url",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "username",
+            "columnName": "username",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "lastSyncAt",
+            "columnName": "last_sync_at",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "lastSyncError",
+            "columnName": "last_sync_error",
+            "affinity": "TEXT"
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": true,
+          "columnNames": [
+            "id"
+          ]
+        }
+      },
+      {
+        "tableName": "task_lists",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `name` TEXT NOT NULL, `color` INTEGER NOT NULL, `account_id` INTEGER, `is_visible` INTEGER NOT NULL DEFAULT 1, `is_synced` INTEGER NOT NULL DEFAULT 1, `owner` TEXT, `is_read_only` INTEGER NOT NULL DEFAULT 0, `sort_order` INTEGER NOT NULL DEFAULT 0, `href` TEXT, `ctag` TEXT, `sync_token` TEXT, `is_dirty` INTEGER NOT NULL DEFAULT 0, FOREIGN KEY(`account_id`) REFERENCES `accounts`(`id`) ON UPDATE NO ACTION ON DELETE SET NULL )",
+        "fields": [
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "name",
+            "columnName": "name",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "color",
+            "columnName": "color",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "accountId",
+            "columnName": "account_id",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "isVisible",
+            "columnName": "is_visible",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "1"
+          },
+          {
+            "fieldPath": "isSynced",
+            "columnName": "is_synced",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "1"
+          },
+          {
+            "fieldPath": "owner",
+            "columnName": "owner",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "isReadOnly",
+            "columnName": "is_read_only",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "sortOrder",
+            "columnName": "sort_order",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "href",
+            "columnName": "href",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "ctag",
+            "columnName": "ctag",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "syncToken",
+            "columnName": "sync_token",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "isDirty",
+            "columnName": "is_dirty",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": true,
+          "columnNames": [
+            "id"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_task_lists_account_id",
+            "unique": false,
+            "columnNames": [
+              "account_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_task_lists_account_id` ON `${TABLE_NAME}` (`account_id`)"
+          }
+        ],
+        "foreignKeys": [
+          {
+            "table": "accounts",
+            "onDelete": "SET NULL",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "account_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          }
+        ]
+      },
+      {
+        "tableName": "tasks",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `list_id` INTEGER NOT NULL, `uid` TEXT NOT NULL, `href` TEXT, `etag` TEXT, `title` TEXT, `description` TEXT, `location` TEXT, `url` TEXT, `color` INTEGER, `categories` TEXT NOT NULL DEFAULT '', `status` INTEGER NOT NULL DEFAULT 0, `percent_complete` INTEGER, `completed_at` INTEGER, `priority` INTEGER NOT NULL DEFAULT 0, `classification` INTEGER, `dtstart` INTEGER, `due` INTEGER, `duration` TEXT, `is_all_day` INTEGER NOT NULL DEFAULT 0, `timezone` TEXT, `rrule` TEXT, `rdate` TEXT, `exdate` TEXT, `recurrence_id` INTEGER, `master_id` INTEGER, `parent_id` INTEGER, `sort_order` INTEGER NOT NULL DEFAULT 0, `created_at` INTEGER, `last_modified` INTEGER, `sequence` INTEGER NOT NULL DEFAULT 0, `is_dirty` INTEGER NOT NULL DEFAULT 0, `is_deleted` INTEGER NOT NULL DEFAULT 0, `unknown_properties` TEXT, FOREIGN KEY(`list_id`) REFERENCES `task_lists`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE , FOREIGN KEY(`master_id`) REFERENCES `tasks`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE , FOREIGN KEY(`parent_id`) REFERENCES `tasks`(`id`) ON UPDATE NO ACTION ON DELETE SET NULL )",
+        "fields": [
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "listId",
+            "columnName": "list_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "uid",
+            "columnName": "uid",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "href",
+            "columnName": "href",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "etag",
+            "columnName": "etag",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "title",
+            "columnName": "title",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "description",
+            "columnName": "description",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "location",
+            "columnName": "location",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "url",
+            "columnName": "url",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "color",
+            "columnName": "color",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "categories",
+            "columnName": "categories",
+            "affinity": "TEXT",
+            "notNull": true,
+            "defaultValue": "''"
+          },
+          {
+            "fieldPath": "status",
+            "columnName": "status",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "percentComplete",
+            "columnName": "percent_complete",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "completedAt",
+            "columnName": "completed_at",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "priority",
+            "columnName": "priority",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "classification",
+            "columnName": "classification",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "dtstart",
+            "columnName": "dtstart",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "due",
+            "columnName": "due",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "duration",
+            "columnName": "duration",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "isAllDay",
+            "columnName": "is_all_day",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "timezone",
+            "columnName": "timezone",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "rrule",
+            "columnName": "rrule",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "rdate",
+            "columnName": "rdate",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "exdate",
+            "columnName": "exdate",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "recurrenceId",
+            "columnName": "recurrence_id",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "masterId",
+            "columnName": "master_id",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "parentId",
+            "columnName": "parent_id",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "sortOrder",
+            "columnName": "sort_order",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "createdAt",
+            "columnName": "created_at",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "lastModified",
+            "columnName": "last_modified",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "sequence",
+            "columnName": "sequence",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "isDirty",
+            "columnName": "is_dirty",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "isDeleted",
+            "columnName": "is_deleted",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "unknownProperties",
+            "columnName": "unknown_properties",
+            "affinity": "TEXT"
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": true,
+          "columnNames": [
+            "id"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_tasks_list_id_is_deleted",
+            "unique": false,
+            "columnNames": [
+              "list_id",
+              "is_deleted"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_tasks_list_id_is_deleted` ON `${TABLE_NAME}` (`list_id`, `is_deleted`)"
+          },
+          {
+            "name": "index_tasks_parent_id",
+            "unique": false,
+            "columnNames": [
+              "parent_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_tasks_parent_id` ON `${TABLE_NAME}` (`parent_id`)"
+          },
+          {
+            "name": "index_tasks_master_id_recurrence_id",
+            "unique": false,
+            "columnNames": [
+              "master_id",
+              "recurrence_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_tasks_master_id_recurrence_id` ON `${TABLE_NAME}` (`master_id`, `recurrence_id`)"
+          },
+          {
+            "name": "index_tasks_is_dirty",
+            "unique": false,
+            "columnNames": [
+              "is_dirty"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_tasks_is_dirty` ON `${TABLE_NAME}` (`is_dirty`)"
+          },
+          {
+            "name": "index_tasks_list_id_uid_recurrence_id",
+            "unique": true,
+            "columnNames": [
+              "list_id",
+              "uid",
+              "recurrence_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE UNIQUE INDEX IF NOT EXISTS `index_tasks_list_id_uid_recurrence_id` ON `${TABLE_NAME}` (`list_id`, `uid`, `recurrence_id`)"
+          }
+        ],
+        "foreignKeys": [
+          {
+            "table": "task_lists",
+            "onDelete": "CASCADE",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "list_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          },
+          {
+            "table": "tasks",
+            "onDelete": "CASCADE",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "master_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          },
+          {
+            "table": "tasks",
+            "onDelete": "SET NULL",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "parent_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          }
+        ]
+      },
+      {
+        "tableName": "task_alarms",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `task_id` INTEGER NOT NULL, `minutes_before` INTEGER NOT NULL, `reference` TEXT NOT NULL DEFAULT 'DUE', `message` TEXT, FOREIGN KEY(`task_id`) REFERENCES `tasks`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE )",
+        "fields": [
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "taskId",
+            "columnName": "task_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "minutesBefore",
+            "columnName": "minutes_before",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "reference",
+            "columnName": "reference",
+            "affinity": "TEXT",
+            "notNull": true,
+            "defaultValue": "'DUE'"
+          },
+          {
+            "fieldPath": "message",
+            "columnName": "message",
+            "affinity": "TEXT"
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": true,
+          "columnNames": [
+            "id"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_task_alarms_task_id",
+            "unique": false,
+            "columnNames": [
+              "task_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_task_alarms_task_id` ON `${TABLE_NAME}` (`task_id`)"
+          }
+        ],
+        "foreignKeys": [
+          {
+            "table": "tasks",
+            "onDelete": "CASCADE",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "task_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          }
+        ]
+      }
+    ],
+    "setupQueries": [
+      "CREATE TABLE IF NOT EXISTS room_master_table (id INTEGER PRIMARY KEY,identity_hash TEXT)",
+      "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, '14b159c51416ba27653f6320ac7f6f03')"
+    ]
+  }
+}

app/src/androidTest/java/de/jeanlucmakiola/agendula/data/tasks/legacy/OneShotImportTest.kt

@@ -212,6 +212,15 @@ class OneShotImportTest {
         assertThat(db.alarms().all().map { it.message }).doesNotContain("Errands")
     }
 
+    @Test
+    fun importsCategoryPropertiesAsTags() {
+        importer.importFrom(fixture())
+        val tasks = taskRows()
+
+        assertThat(tasks.getValue("Buy milk").categories).containsExactly("Errands")
+        assertThat(tasks.getValue("Ship the release").categories).isEmpty()
+    }
+
     // --- running it -----------------------------------------------------------
 
     @Test

app/src/androidTest/java/de/jeanlucmakiola/agendula/data/tasks/room/TasksDatabaseMigrationTest.kt

@@ -8,27 +8,7 @@ import org.junit.Rule
 import org.junit.Test
 import org.junit.runner.RunWith
 
-/**
- * The migration harness, proven against the committed schema in `app/schemas/`.
- *
- * There is one schema version today, so all there is to assert is that the helper
- * can build v1 from the exported JSON, seed it, and validate it back — i.e. the
- * export, the assets wiring and the identity hash all line up. That is the point:
- * the first real migration only has to add its own case.
- *
- * **Adding a v1 → v2 case.** When sync adds columns, bump [TasksDatabase]'s
- * `version`, let KSP export `2.json`, declare the `Migration(1, 2)` next to the
- * database, and add a test here shaped like this:
- *
- * ```
- * helper.createDatabase(TEST_DB, 1).use { db ->
- *     db.execSQL("INSERT INTO task_lists (name, color) VALUES ('Groceries', 0)")
- * }
- * helper.runMigrationsAndValidate(TEST_DB, 2, true, MIGRATION_1_2).use { db ->
- *     // read the seeded rows back — validation proves the shape, not the data
- * }
- * ```
- */
+/** Migrations, proven against the committed schemas in `app/schemas/`. */
 @RunWith(AndroidJUnit4::class)
 class TasksDatabaseMigrationTest {
 
@@ -62,6 +42,39 @@ class TasksDatabaseMigrationTest {
         }
     }
 
+    @Test
+    fun liftsCategoriesOutOfTheResidueWithoutDirtyingTheTask() {
+        helper.createDatabase(TEST_DB, 1).use { db ->
+            db.execSQL("INSERT INTO task_lists (id, name, color) VALUES (1, 'Work', 0)")
+            db.execSQL(
+                "INSERT INTO tasks (id, list_id, uid, title, unknown_properties) VALUES (?, 1, ?, ?, ?)",
+                arrayOf<Any?>(1, "uid-1", "Claimed", "X-FOO:bar\r\nCATEGORIES:Work,Home\r\n"),
+            )
+            db.execSQL(
+                "INSERT INTO tasks (id, list_id, uid, title, unknown_properties) VALUES (?, 1, ?, ?, ?)",
+                arrayOf<Any?>(2, "uid-2", "Split", "CATEGORIES:a\r\nCATEGORIES:b\r\n"),
+            )
+            db.execSQL("INSERT INTO tasks (id, list_id, uid, title) VALUES (3, 1, 'uid-3', 'Untagged')")
+        }
+
+        helper.runMigrationsAndValidate(TEST_DB, 2, true, TasksDatabase.MIGRATION_1_2).use { db ->
+            db.query("SELECT categories, unknown_properties, is_dirty FROM tasks ORDER BY id").use { c ->
+                c.moveToNext()
+                assertThat(c.getString(0)).isEqualTo("Work,Home")
+                assertThat(c.getString(1)).doesNotContain("CATEGORIES")
+                assertThat(c.getString(1)).contains("X-FOO:bar")
+                assertThat(c.getInt(2)).isEqualTo(0)
+
+                c.moveToNext()
+                assertThat(c.getString(0)).isEqualTo("a,b")
+                assertThat(c.getString(1)).isEqualTo("CATEGORIES:a\r\nCATEGORIES:b\r\n")
+
+                c.moveToNext()
+                assertThat(c.getString(0)).isEmpty()
+            }
+        }
+    }
+
     private companion object {
         const val TEST_DB = "migration-test.db"
     }

app/src/androidTest/java/de/jeanlucmakiola/agendula/data/tasks/transfer/ExternalImportTest.kt

@@ -107,6 +107,17 @@ class ExternalImportTest {
         assertThat(importer.hasRun.first()).isTrue()
     }
 
+    @Test
+    fun copiesTagsCleanedUp() = runBlocking {
+        source.lists = listOf(list(7, "Errands"))
+        source.tasks = mapOf(7L to listOf(task(100, "Milk", tags = listOf("Shop", " Shop ", "", "Home"))))
+
+        importer.run()
+
+        assertThat(db.tasks().tasks(listId = null, includeCompleted = true).single().task.categories)
+            .containsExactly("Shop", "Home").inOrder()
+    }
+
     /** Every list arrives device-only: the account belongs to the sync app. */
     @Test
     fun importedListsAreDeviceOnly() = runBlocking {
@@ -241,6 +252,7 @@ class ExternalImportTest {
         title: String,
         uid: String? = "uid-$id",
         parentId: Long? = null,
+        tags: List<String> = emptyList(),
     ) = ExportTask(
         taskId = id,
         uid = uid,
@@ -260,6 +272,7 @@ class ExternalImportTest {
         rrule = null,
         rdate = null,
         parentId = parentId,
+        tags = tags,
     )
 
     private companion object {

app/src/full/AndroidManifest.xml

@@ -0,0 +1,88 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- CalDAV sync and UnifiedPush; everything here needs the network. -->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <!-- CalDAV sync. ACCESS_NETWORK_STATE is merged in by work-runtime anyway,
+         but it shows in F-Droid's permission diff, so declare it deliberately
+         rather than letting it appear from nowhere.
+
+         READ_SYNC_SETTINGS / WRITE_SYNC_SETTINGS are what the ContentResolver
+         sync APIs need. No FOREGROUND_SERVICE: sync is a plain worker, and the
+         dataSync FGS type would bring the Android 15 six-hours-per-24 budget
+         (whose failure mode is a fatal RemoteServiceException) and a Play
+         requirement for a video demo.
+
+         Two more permissions appear in the merged manifest without being
+         declared here, and both come from work-runtime: WAKE_LOCK, and
+         FOREGROUND_SERVICE. The latter is not us taking the FGS route — below
+         API 31 WorkManager implements expedited work with a foreground service,
+         and minSdk is 29, so it is load-bearing for the "Sync now" button.
+         Removing it with tools:node="remove" would break expedited work on
+         exactly the older devices that need it most. Noted because it shows in
+         F-Droid's permission diff and would otherwise look unexplained. -->
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.READ_SYNC_SETTINGS" />
+    <uses-permission android:name="android.permission.WRITE_SYNC_SETTINGS" />
+
+    <queries>
+        <!-- Custom Tabs provider detection. Without this entry it silently finds
+             nothing on API 30+, and the Nextcloud login flow falls back to an
+             external browser for no visible reason. -->
+        <intent>
+            <action android:name="android.support.customtabs.action.CustomTabsService" />
+        </intent>
+    </queries>
+
+    <application android:networkSecurityConfig="@xml/network_security_config">
+
+        <!-- Sync plumbing. The stub provider exists only to give the sync
+             adapter an authority to register against: Agendula publishes no real
+             ContentProvider since :provider was deleted, and without an authority
+             ContentService.hasAuthorityAccess() makes every ContentResolver sync
+             call a silent no-op at targetSdk >= 34. -->
+        <provider
+            android:name=".data.sync.SyncStubProvider"
+            android:authorities="${applicationId}.sync"
+            android:exported="false"
+            android:syncable="true" />
+
+        <!-- Exported and guarded by ACCOUNT_MANAGER. Note that
+             android.permission.ACCOUNT_AUTHENTICATOR does not exist. -->
+        <service
+            android:name=".data.sync.AuthenticatorService"
+            android:exported="true"
+            android:permission="android.permission.ACCOUNT_MANAGER">
+            <intent-filter>
+                <action android:name="android.accounts.AccountAuthenticator" />
+            </intent-filter>
+            <meta-data
+                android:name="android.accounts.AccountAuthenticator"
+                android:resource="@xml/authenticator" />
+        </service>
+
+        <service
+            android:name=".data.sync.SyncAdapterService"
+            android:exported="true"
+            android:permission="android.permission.BIND_SYNC_ADAPTER">
+            <intent-filter>
+                <action android:name="android.content.SyncAdapter" />
+            </intent-filter>
+            <meta-data
+                android:name="android.content.SyncAdapter"
+                android:resource="@xml/sync_adapter" />
+        </service>
+
+        <!-- UnifiedPush: the connector binds this to deliver endpoints and
+             WebDAV-Push messages. Not exported; the connector's own receiver is
+             what distributors talk to. -->
+        <service
+            android:name=".data.sync.push.AgendulaPushService"
+            android:exported="false">
+            <intent-filter>
+                <action android:name="org.unifiedpush.android.connector.PUSH_EVENT" />
+            </intent-filter>
+        </service>
+    </application>
+
+</manifest>

app/src/full/java/de/jeanlucmakiola/agendula/data/di/SyncModule.kt

@@ -0,0 +1,131 @@
+package de.jeanlucmakiola.agendula.data.di
+
+import android.content.Context
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.preferencesDataStore
+import dagger.Binds
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import dagger.multibindings.IntoSet
+import de.jeanlucmakiola.agendula.data.sync.AccountCreator
+import de.jeanlucmakiola.agendula.data.sync.AccountRepository
+import de.jeanlucmakiola.agendula.data.sync.CalDavGateway
+import de.jeanlucmakiola.agendula.data.sync.LoginFlowRecord
+import de.jeanlucmakiola.agendula.data.sync.OkHttpCalDavGateway
+import de.jeanlucmakiola.agendula.data.sync.PendingLoginFlowStore
+import de.jeanlucmakiola.agendula.data.sync.RemoteListRepository
+import de.jeanlucmakiola.agendula.data.sync.RemoteLists
+import de.jeanlucmakiola.agendula.data.sync.SyncNoticeNotifier
+import de.jeanlucmakiola.agendula.data.sync.SyncOnEdit
+import de.jeanlucmakiola.agendula.data.sync.SyncRequests
+import de.jeanlucmakiola.agendula.data.sync.SyncTrigger
+import de.jeanlucmakiola.agendula.data.sync.push.PushRegistrar
+import de.jeanlucmakiola.agendula.data.tasks.room.LocalWriteListener
+import javax.inject.Provider
+import javax.inject.Singleton
+
+/** See [CredentialsDataStore] for why this is a separate file. */
+private val Context.credentialsDataStore: DataStore<Preferences> by preferencesDataStore(
+    name = CREDENTIALS_DATASTORE,
+    corruptionHandler = replaceCorrupted(),
+)
+
+/** See [SyncStateDataStore] for why this is a separate file. */
+private val Context.syncStateDataStore: DataStore<Preferences> by preferencesDataStore(
+    name = SYNC_STATE_DATASTORE,
+    corruptionHandler = replaceCorrupted(),
+)
+
+/**
+ * Named here and in `backup_rules.xml` / `data_extraction_rules.xml`, which
+ * exclude `datastore/$CREDENTIALS_DATASTORE.preferences_pb` by this name.
+ */
+const val CREDENTIALS_DATASTORE = "agendula_credentials"
+
+/**
+ * Named here and in `backup_rules.xml` / `data_extraction_rules.xml`, which
+ * exclude `datastore/$SYNC_STATE_DATASTORE.preferences_pb` by this name.
+ */
+const val SYNC_STATE_DATASTORE = "agendula_sync_state"
+
+/** CalDAV sync: the `full` flavor's side of the seams `main` declares. */
+@Module
+@InstallIn(SingletonComponent::class)
+abstract class SyncBindModule {
+
+    @Binds
+    @Singleton
+    abstract fun bindCalDavGateway(impl: OkHttpCalDavGateway): CalDavGateway
+
+    @Binds
+    @Singleton
+    abstract fun bindAccountCreator(impl: AccountRepository): AccountCreator
+
+    @Binds
+    @Singleton
+    abstract fun bindLoginFlowRecord(impl: PendingLoginFlowStore): LoginFlowRecord
+
+    @Binds
+    @Singleton
+    abstract fun bindLocalWriteListener(impl: SyncOnEdit): LocalWriteListener
+
+    @Binds
+    @Singleton
+    abstract fun bindRemoteLists(impl: RemoteListRepository): RemoteLists
+
+    @Binds
+    @Singleton
+    abstract fun bindSyncRequests(impl: SyncTrigger): SyncRequests
+
+    @Binds
+    @IntoSet
+    abstract fun bindSyncNoticeChannel(impl: SyncNoticeNotifier): ChannelRefresher
+}
+
+@Module
+@InstallIn(SingletonComponent::class)
+object SyncProvideModule {
+
+    @Provides
+    @Singleton
+    @CredentialsDataStore
+    fun provideCredentialsDataStore(@ApplicationContext context: Context): DataStore<Preferences> =
+        context.credentialsDataStore
+
+    @Provides
+    @Singleton
+    @SyncStateDataStore
+    fun provideSyncStateDataStore(@ApplicationContext context: Context): DataStore<Preferences> =
+        context.syncStateDataStore
+
+    /**
+     * Sync hard on app open: the periodic worker's interval is a floor, and in
+     * the `rare` and `restricted` App Standby buckets it may not have run at
+     * all. `KEEP` makes rescheduling idempotent, so this also repairs a schedule
+     * lost to "clear app data" or to a restore.
+     */
+    @Provides
+    @IntoSet
+    fun syncOnOpenHook(
+        accounts: Provider<AccountRepository>,
+        syncTrigger: Provider<SyncTrigger>,
+        pendingLoginFlows: Provider<PendingLoginFlowStore>,
+        push: Provider<PushRegistrar>,
+    ): LaunchHook = LaunchHook {
+        runCatching {
+            accounts.get().rescheduleAll()
+            accounts.get().syncable().forEach { syncTrigger.get().enqueue(it.displayName) }
+            // A login flow the previous process died in the middle of.
+            // Its password, if the user approved, exists nowhere else.
+            pendingLoginFlows.get().reclaim()
+        }
+        // Last and on its own: it waits on the network, and must not hold up
+        // the reclaim above. Re-registering on open is what the connector
+        // recommends.
+        runCatching { push.get().updateAll() }
+    }
+}

app/src/full/java/de/jeanlucmakiola/agendula/data/di/SyncQualifiers.kt

@@ -0,0 +1,34 @@
+package de.jeanlucmakiola.agendula.data.di
+
+import javax.inject.Qualifier
+
+/**
+ * Marks the DataStore holding **only** the Keystore-encrypted app passwords.
+ *
+ * A separate file from `agendula_prefs` on purpose: Auto Backup includes
+ * `datastore/`, and a restored ciphertext is permanently undecryptable because
+ * Keystore keys are non-exportable. Its own file is what lets the backup rules
+ * exclude the credentials and nothing else — excluding the whole database or
+ * all of DataStore would trade a latent bug for a live one.
+ */
+@Qualifier
+@Retention(AnnotationRetention.BINARY)
+annotation class CredentialsDataStore
+
+/**
+ * Marks the DataStore holding per-device **sync bookkeeping** — the quarantine
+ * counters and the full-reconciliation clock.
+ *
+ * Its own file for the same reason the credentials have one: Auto Backup
+ * includes `datastore/`, and every value in here is a statement about *this*
+ * device's conversation with a server. Restored onto a new install they are all
+ * lies, and two of them are dangerous — a restored "reconciled recently" makes
+ * the engine trust a sync token for another day, which is precisely the silently
+ * pruned change log the full path exists to catch, and a restored quarantine
+ * count silently skips resources that were never tried here.
+ *
+ * Not user data, so nothing is lost by excluding it.
+ */
+@Qualifier
+@Retention(AnnotationRetention.BINARY)
+annotation class SyncStateDataStore

app/src/full/java/de/jeanlucmakiola/agendula/data/sync/RemoteListRepository.kt

@@ -1,6 +1,7 @@
 package de.jeanlucmakiola.agendula.data.sync
 
 import de.jeanlucmakiola.agendula.data.di.IoDispatcher
+import de.jeanlucmakiola.agendula.data.sync.RemoteLists.Outcome
 import de.jeanlucmakiola.agendula.data.sync.push.PushStore
 import de.jeanlucmakiola.agendula.data.tasks.ProviderResolver
 import de.jeanlucmakiola.agendula.data.tasks.StorageMode
@@ -53,38 +54,7 @@ class RemoteListRepository @Inject constructor(
     private val resolver: ProviderResolver,
     private val push: PushStore,
     @IoDispatcher private val io: CoroutineDispatcher,
-) {
-
-    /** Why a collection write did not happen, in a form the UI can translate. */
-    sealed interface Outcome {
-        data object Done : Outcome
-
-        /** The server said no, and will say no again. */
-        data class Refused(val code: Int) : Outcome
-
-        /** The server could not be reached. Worth another try. */
-        data object Unreachable : Outcome
-
-        /** This account cannot make collections at all — iCloud, Posteo, Google. */
-        data object Unsupported : Outcome
-
-        /** Ours is a read-only share; the write belongs to whoever owns it. */
-        data object ReadOnly : Outcome
-
-        /** The account is gone, stopped, or has no credential we can decrypt. */
-        data object NoAccount : Outcome
-
-        /**
-         * The server answered something this call cannot make sense of.
-         *
-         * ⚠️ Not [Unreachable]. `CollectionOutcome` is one type across create,
-         * update and delete, so each of them has branches the other's method
-         * can return and its own cannot — and mapping those to [Unreachable]
-         * told someone sitting on wifi that they were offline. Unreachable is a
-         * claim about the network, and this is not one.
-         */
-        data object Unexpected : Outcome
-    }
+) : RemoteLists {
 
     /**
      * The accounts a new list may be created on, freshest answer first.
@@ -95,7 +65,7 @@ class RemoteListRepository @Inject constructor(
      * able to say so, and the only moment that costs nothing is while the user
      * is looking at the picker.
      */
-    suspend fun creatableAccounts(): List<AccountEntity> = withContext(io) {
+    override suspend fun creatableAccounts(): List<AccountEntity> = withContext(io) {
         // ⚠️ Empty in External mode, whatever the accounts table holds. The
         // lists on screen then come from a third-party provider, so a row
         // inserted into ours would exist, sync, and be visible to nobody.
@@ -120,7 +90,7 @@ class RemoteListRepository @Inject constructor(
      *
      * @return the new list's local id, or why there is none.
      */
-    suspend fun create(
+    override suspend fun create(
         accountId: Long,
         name: String,
         color: Int,
@@ -189,7 +159,7 @@ class RemoteListRepository @Inject constructor(
      * a row that has already been renamed locally by then reads as a rename that
      * worked and then quietly reverted on the next sync.
      */
-    suspend fun rename(listId: Long, name: String, color: Int): Outcome = withContext(io) {
+    override suspend fun rename(listId: Long, name: String, color: Int): Outcome = withContext(io) {
         val list = database.taskLists().entity(listId) ?: return@withContext Outcome.NoAccount
         if (list.isReadOnly) return@withContext Outcome.ReadOnly
         val url = list.href?.toHttpUrlOrNull() ?: return@withContext Outcome.NoAccount
@@ -227,7 +197,7 @@ class RemoteListRepository @Inject constructor(
      * grades 404 and 410 that way — because otherwise a collection someone
      * removed from another client leaves a row here that nothing can get rid of.
      */
-    suspend fun delete(listId: Long): Outcome = withContext(io) {
+    override suspend fun delete(listId: Long): Outcome = withContext(io) {
         val list = database.taskLists().entity(listId) ?: return@withContext Outcome.Done
         if (list.isReadOnly) return@withContext Outcome.ReadOnly
         val url = list.href?.toHttpUrlOrNull() ?: return@withContext Outcome.NoAccount

app/src/full/java/de/jeanlucmakiola/agendula/data/sync/SyncNoticeNotifier.kt

@@ -14,6 +14,7 @@ import androidx.core.app.NotificationManagerCompat
 import androidx.core.content.ContextCompat
 import dagger.hilt.android.qualifiers.ApplicationContext
 import de.jeanlucmakiola.agendula.MainActivity
+import de.jeanlucmakiola.agendula.data.di.ChannelRefresher
 import de.jeanlucmakiola.agendula.R
 import javax.inject.Inject
 import javax.inject.Singleton
@@ -33,7 +34,7 @@ import javax.inject.Singleton
 @Singleton
 class SyncNoticeNotifier @Inject constructor(
     @ApplicationContext private val context: Context,
-) {
+) : ChannelRefresher {
 
     fun canPost(): Boolean {
         val granted = Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU ||
@@ -123,7 +124,7 @@ class SyncNoticeNotifier @Inject constructor(
      * extra names the account for routing to Settings → Accounts → it.
      */
     private fun signInIntent(accountId: Long): Intent =
-        MainActivity.openIntent(context).putExtra(EXTRA_SIGN_IN_ACCOUNT_ID, accountId)
+        MainActivity.openIntent(context).putExtra(MainActivity.EXTRA_SIGN_IN_ACCOUNT_ID, accountId)
 
     private fun ensureSignInChannel() {
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) return
@@ -170,16 +171,13 @@ class SyncNoticeNotifier @Inject constructor(
     }
 
     /** Re-create the channel, if it exists, in the current language. */
-    fun refreshChannel() {
+    override fun refreshChannel() {
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) return
         val manager = context.getSystemService(NotificationManager::class.java)
         if (manager.getNotificationChannel(CHANNEL_ID) != null) ensureChannel()
     }
 
     companion object {
-        /** The account a sign-in notification is about, on the intent it opens. */
-        const val EXTRA_SIGN_IN_ACCOUNT_ID = "de.jeanlucmakiola.agendula.extra.SIGN_IN_ACCOUNT_ID"
-
         private const val CHANNEL_ID = "sync_notices"
         private const val NOTIFICATION_ID = 2
         private const val SIGN_IN_CHANNEL_ID = "account_sign_in"

app/src/full/java/de/jeanlucmakiola/agendula/data/sync/SyncTrigger.kt

@@ -35,7 +35,11 @@ import kotlin.time.Duration.Companion.seconds
 @Singleton
 class SyncTrigger @Inject constructor(
     @ApplicationContext private val context: Context,
-) {
+) : SyncRequests {
+
+    override fun syncNow(accountName: String) {
+        enqueue(accountName)
+    }
 
     /**
      * Starts a sync now.

app/src/full/java/de/jeanlucmakiola/agendula/ui/onboarding/AccountStep.kt

@@ -0,0 +1,35 @@
+package de.jeanlucmakiola.agendula.ui.onboarding
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.hilt.lifecycle.viewmodel.compose.hiltViewModel
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import de.jeanlucmakiola.agendula.ui.accounts.add.ADD_ACCOUNT_STEPS
+import de.jeanlucmakiola.agendula.ui.accounts.add.AddAccountScreen
+import de.jeanlucmakiola.agendula.ui.accounts.add.AddAccountViewModel
+
+/** The inline wizard's shortest length, before a provider is picked. */
+internal const val ACCOUNT_STEP_SLOTS = ADD_ACCOUNT_STEPS
+
+/** [OnboardingStep.Account]: the add-account wizard, given the whole screen. */
+@Composable
+internal fun AccountStep(state: OnboardingUiState, viewModel: OnboardingViewModel) {
+    // The same instance the wizard resolves for itself, so its length can be
+    // read here without keeping a second copy of its state.
+    val account: AddAccountViewModel = hiltViewModel()
+    val accountState by account.state.collectAsStateWithLifecycle()
+    // ⚠️ The wizard grows a step for a provider that needs an app password
+    // minted first, and the outer bar has to grow with it — otherwise first
+    // run counts one flow while the screen inside it counts another.
+    LaunchedEffect(accountState.totalSteps) {
+        viewModel.onAccountStepsChanged(accountState.totalSteps)
+    }
+    AddAccountScreen(
+        onDone = { viewModel.onAccountFinished(added = true) },
+        onBack = { viewModel.onAccountFinished(added = false) },
+        stepOffset = state.position - 1,
+        totalSteps = state.total,
+        viewModel = account,
+    )
+}

app/src/full/java/de/jeanlucmakiola/agendula/ui/settings/AccountSections.kt

@@ -0,0 +1,78 @@
+package de.jeanlucmakiola.agendula.ui.settings
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.hilt.lifecycle.viewmodel.compose.hiltViewModel
+import de.jeanlucmakiola.agendula.data.tasks.room.AccountEntity
+import de.jeanlucmakiola.agendula.ui.accounts.AccountDetailScreen
+import de.jeanlucmakiola.agendula.ui.accounts.AccountsScreen
+import de.jeanlucmakiola.agendula.ui.accounts.AccountsViewModel
+import de.jeanlucmakiola.agendula.ui.accounts.add.AddAccountScreen
+import de.jeanlucmakiola.agendula.ui.accounts.add.AddAccountViewModel
+
+/** Settings → Accounts and the screens under it, layered over the hub. */
+@Composable
+internal fun AccountSections(
+    section: SettingsSection?,
+    initialAccountId: Long?,
+    onSection: (SettingsSection?) -> Unit,
+) {
+    // Hoisted so the add flow can refresh the list it returns to.
+    val accountsViewModel: AccountsViewModel = hiltViewModel()
+    // Shared with the add flow's own lookup, so "sign in again" can prefill it.
+    val addAccountViewModel: AddAccountViewModel = hiltViewModel()
+    val signInAgain: (AccountEntity) -> Unit = { account ->
+        addAccountViewModel.startReauthentication(account.id, account.principalUrl, account.username)
+        onSection(SettingsSection.AddAccount)
+    }
+    // Which account the detail screen is showing; the section alone cannot say.
+    var openAccount by rememberSaveable(initialAccountId) { mutableStateOf(initialAccountId) }
+
+    // Accounts stays composed under Add account, for the same reason Storage
+    // stays composed under Export: the deeper screen slides over it.
+    val accountsOpen = section == SettingsSection.Accounts ||
+        section?.parent == SettingsSection.Accounts
+    SlideInSection(visible = accountsOpen) {
+        AccountsScreen(
+            onAddAccount = {
+                // A sign-in abandoned half-way must not turn this into one.
+                if (addAccountViewModel.state.value.reauthenticating) addAccountViewModel.onStartOver()
+                onSection(SettingsSection.AddAccount)
+            },
+            onSignInAgain = signInAgain,
+            onOpenAccount = {
+                openAccount = it
+                onSection(SettingsSection.Account)
+            },
+            onOpenStorage = { onSection(SettingsSection.Storage) },
+            onBack = { onSection(null) },
+            viewModel = accountsViewModel,
+        )
+    }
+    SlideInSection(visible = section == SettingsSection.Account) {
+        openAccount?.let { id ->
+            AccountDetailScreen(
+                accountId = id,
+                onBack = { onSection(SettingsSection.Accounts) },
+                onRemoved = { onSection(SettingsSection.Accounts) },
+                onSignInAgain = signInAgain,
+                onOpenStorage = { onSection(SettingsSection.Storage) },
+                viewModel = accountsViewModel,
+            )
+        }
+    }
+    SlideInSection(visible = section == SettingsSection.AddAccount) {
+        AddAccountScreen(
+            // The list stays composed underneath, so nothing re-runs its
+            // init and OnResume never fires on a section change. It no longer
+            // needs to: the accounts come from an observed query, so a new
+            // account — and every later sync — arrives on its own.
+            onDone = { onSection(SettingsSection.Accounts) },
+            onBack = { onSection(SettingsSection.Accounts) },
+            viewModel = addAccountViewModel,
+        )
+    }
+}

app/src/main/AndroidManifest.xml

@@ -16,29 +16,6 @@
     <uses-permission android:name="org.tasks.permission.READ_TASKS" />
     <uses-permission android:name="org.tasks.permission.WRITE_TASKS" />
 
-    <!-- CalDAV sync. ACCESS_NETWORK_STATE is merged in by work-runtime anyway,
-         but it shows in F-Droid's permission diff, so declare it deliberately
-         rather than letting it appear from nowhere.
-
-         READ_SYNC_SETTINGS / WRITE_SYNC_SETTINGS are what the ContentResolver
-         sync APIs need. No FOREGROUND_SERVICE: sync is a plain worker, and the
-         dataSync FGS type would bring the Android 15 six-hours-per-24 budget
-         (whose failure mode is a fatal RemoteServiceException) and a Play
-         requirement for a video demo.
-
-         Two more permissions appear in the merged manifest without being
-         declared here, and both come from work-runtime: WAKE_LOCK, and
-         FOREGROUND_SERVICE. The latter is not us taking the FGS route — below
-         API 31 WorkManager implements expedited work with a foreground service,
-         and minSdk is 29, so it is load-bearing for the "Sync now" button.
-         Removing it with tools:node="remove" would break expedited work on
-         exactly the older devices that need it most. Noted because it shows in
-         F-Droid's permission diff and would otherwise look unexplained. -->
-    <uses-permission android:name="android.permission.INTERNET" />
-    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
-    <uses-permission android:name="android.permission.READ_SYNC_SETTINGS" />
-    <uses-permission android:name="android.permission.WRITE_SYNC_SETTINGS" />
-
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
     <!-- Exact due-time reminders. User-granted: USE_EXACT_ALARM is reserved for
@@ -55,12 +32,6 @@
             <action android:name="android.intent.action.MAIN" />
             <category android:name="android.intent.category.LAUNCHER" />
         </intent>
-        <!-- Custom Tabs provider detection. Without this entry it silently finds
-             nothing on API 30+, and the Nextcloud login flow falls back to an
-             external browser for no visible reason. -->
-        <intent>
-            <action android:name="android.support.customtabs.action.CustomTabsService" />
-        </intent>
     </queries>
 
     <application
@@ -71,7 +42,6 @@
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:localeConfig="@xml/locales_config"
-        android:networkSecurityConfig="@xml/network_security_config"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/Theme.Agendula"
@@ -263,54 +233,6 @@
             </intent-filter>
         </receiver>
 
-        <!-- Sync plumbing. The stub provider exists only to give the sync
-             adapter an authority to register against: Agendula publishes no real
-             ContentProvider since :provider was deleted, and without an authority
-             ContentService.hasAuthorityAccess() makes every ContentResolver sync
-             call a silent no-op at targetSdk >= 34. -->
-        <provider
-            android:name=".data.sync.SyncStubProvider"
-            android:authorities="${applicationId}.sync"
-            android:exported="false"
-            android:syncable="true" />
-
-        <!-- Exported and guarded by ACCOUNT_MANAGER. Note that
-             android.permission.ACCOUNT_AUTHENTICATOR does not exist. -->
-        <service
-            android:name=".data.sync.AuthenticatorService"
-            android:exported="true"
-            android:permission="android.permission.ACCOUNT_MANAGER">
-            <intent-filter>
-                <action android:name="android.accounts.AccountAuthenticator" />
-            </intent-filter>
-            <meta-data
-                android:name="android.accounts.AccountAuthenticator"
-                android:resource="@xml/authenticator" />
-        </service>
-
-        <service
-            android:name=".data.sync.SyncAdapterService"
-            android:exported="true"
-            android:permission="android.permission.BIND_SYNC_ADAPTER">
-            <intent-filter>
-                <action android:name="android.content.SyncAdapter" />
-            </intent-filter>
-            <meta-data
-                android:name="android.content.SyncAdapter"
-                android:resource="@xml/sync_adapter" />
-        </service>
-
-        <!-- UnifiedPush: the connector binds this to deliver endpoints and
-             WebDAV-Push messages. Not exported; the connector's own receiver is
-             what distributors talk to. -->
-        <service
-            android:name=".data.sync.push.AgendulaPushService"
-            android:exported="false">
-            <intent-filter>
-                <action android:name="org.unifiedpush.android.connector.PUSH_EVENT" />
-            </intent-filter>
-        </service>
-
         <!-- WorkManager's on-demand initialisation. Removing the default
              initializer is what lets AgendulaApp supply a HiltWorkerFactory, so
              @HiltWorker workers can take injected dependencies. -->

app/src/main/java/de/jeanlucmakiola/agendula/AgendulaApp.kt

@@ -10,10 +10,10 @@ import dagger.hilt.android.EntryPointAccessors
 import dagger.hilt.android.HiltAndroidApp
 import dagger.hilt.components.SingletonComponent
 import de.jeanlucmakiola.agendula.data.di.ApplicationScope
+import de.jeanlucmakiola.agendula.data.di.ChannelRefresher
 import de.jeanlucmakiola.agendula.data.reminders.ReminderMaintenanceWorker
 import de.jeanlucmakiola.agendula.data.reminders.ReminderScheduler
 import de.jeanlucmakiola.agendula.data.reminders.TaskNotifier
-import de.jeanlucmakiola.agendula.data.sync.SyncNoticeNotifier
 import de.jeanlucmakiola.agendula.data.tasks.ProviderResolver
 import de.jeanlucmakiola.agendula.data.tasks.StartupGate
 import de.jeanlucmakiola.agendula.data.tasks.room.DatabaseCheckpoint
@@ -105,7 +105,7 @@ class AgendulaApp : Application(), Configuration.Provider {
         val entryPoint = EntryPointAccessors.fromApplication(this, AppEntryPoint::class.java)
         runCatching {
             entryPoint.taskNotifier().refreshChannel()
-            entryPoint.syncNoticeNotifier().refreshChannel()
+            entryPoint.channelRefreshers().forEach { it.refreshChannel() }
         }
     }
 
@@ -120,7 +120,7 @@ class AgendulaApp : Application(), Configuration.Provider {
         fun applicationScope(): CoroutineScope
         fun databaseCheckpoint(): DatabaseCheckpoint
         fun taskNotifier(): TaskNotifier
-        fun syncNoticeNotifier(): SyncNoticeNotifier
+        fun channelRefreshers(): Set<@JvmSuppressWildcards ChannelRefresher>
         fun taskWidgetUpdater(): TaskWidgetUpdater
     }
 }

app/src/main/java/de/jeanlucmakiola/agendula/MainActivity.kt

@@ -25,7 +25,6 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.lifecycle.lifecycleScope
 import dagger.hilt.android.AndroidEntryPoint
 import de.jeanlucmakiola.agendula.data.di.LaunchHook
-import de.jeanlucmakiola.agendula.data.sync.SyncNoticeNotifier
 import de.jeanlucmakiola.agendula.domain.SmartList
 import de.jeanlucmakiola.agendula.ui.imports.importIntentUri
 import de.jeanlucmakiola.agendula.ui.navigation.AppShortcuts
@@ -33,10 +32,6 @@ import de.jeanlucmakiola.agendula.data.prefs.ThemeMode
 import de.jeanlucmakiola.agendula.ui.RootScreen
 import de.jeanlucmakiola.agendula.ui.crash.CrashReportActivity
 import de.jeanlucmakiola.agendula.ui.navigation.NavRequest
-import de.jeanlucmakiola.agendula.data.sync.AccountRepository
-import de.jeanlucmakiola.agendula.data.sync.PendingLoginFlowStore
-import de.jeanlucmakiola.agendula.data.sync.SyncTrigger
-import de.jeanlucmakiola.agendula.data.sync.push.PushRegistrar
 import de.jeanlucmakiola.agendula.ui.settings.SettingsViewModel
 import de.jeanlucmakiola.agendula.ui.theme.AgendulaTheme
 import de.jeanlucmakiola.floret.crash.CrashReportDialog
@@ -55,14 +50,6 @@ class MainActivity : ComponentActivity() {
 
     @Inject lateinit var launchHooks: Set<@JvmSuppressWildcards LaunchHook>
 
-    @Inject lateinit var accounts: AccountRepository
-
-    @Inject lateinit var syncTrigger: SyncTrigger
-
-    @Inject lateinit var pendingLoginFlows: PendingLoginFlowStore
-
-    @Inject lateinit var push: PushRegistrar
-
     // A captured crash report awaiting the user's decision, surfaced as a dialog
     // over the app on the next launch (the single-crash path). A startup
     // crash-loop is handled out of band, before setContent — see below.
@@ -94,34 +81,9 @@ class MainActivity : ComponentActivity() {
         // Surface a single captured crash as a dialog on the next launch.
         if (CrashReporter.shouldPrompt(this)) pendingCrashReport = CrashReporter.pendingReport(this)
 
-        // Sync hard on app open: the periodic worker's interval is a floor, and
-        // in the `rare` and `restricted` App Standby buckets it may not have run
-        // at all. `KEEP` makes rescheduling idempotent, so this also repairs a
-        // schedule lost to "clear app data" or to a restore.
-        //
-        // ⚠️ Only on a genuine open. This activity declares no `configChanges`,
-        // so onCreate runs again on every rotation, theme switch, locale change
-        // and font-scale change — each of which would otherwise start a fresh
-        // network sync the moment the previous one finished.
+        // Each hook on its own, so one waiting on the network holds up no other.
         if (savedInstanceState == null) {
-            lifecycleScope.launch {
-                runCatching {
-                    accounts.rescheduleAll()
-                    accounts.syncable().forEach { syncTrigger.enqueue(it.displayName) }
-                    // A login flow the previous process died in the middle of.
-                    // Its password, if the user approved, exists nowhere else.
-                    pendingLoginFlows.reclaim()
-                }
-                // Last and on its own: it waits on the network, and must not
-                // hold up the reclaim above. Re-registering on open is what
-                // the connector recommends.
-                runCatching { push.updateAll() }
-            }
-        }
-
-        // Variant hooks: the demo seeder in debug builds, nothing in release.
-        if (savedInstanceState == null) {
-            lifecycleScope.launch { launchHooks.forEach { runCatching { it.onLaunch(intent) } } }
+            launchHooks.forEach { hook -> lifecycleScope.launch { runCatching { hook.onLaunch(intent) } } }
         }
         setContent {
             val settingsViewModel: SettingsViewModel = hiltViewModel()
@@ -180,6 +142,9 @@ class MainActivity : ComponentActivity() {
         const val EXTRA_TASK_ID = "de.jeanlucmakiola.agendula.extra.TASK_ID"
         const val EXTRA_OCCURRENCE_START = "de.jeanlucmakiola.agendula.extra.OCCURRENCE_START"
         private const val EXTRA_OPEN_ACCOUNTS = "de.jeanlucmakiola.agendula.extra.OPEN_ACCOUNTS"
+
+        /** The account a sign-in notification is about, on the intent it opens. */
+        const val EXTRA_SIGN_IN_ACCOUNT_ID = "de.jeanlucmakiola.agendula.extra.SIGN_IN_ACCOUNT_ID"
         const val ACTION_NEW_TASK = "de.jeanlucmakiola.agendula.action.NEW_TASK"
         const val ACTION_TODAY = "de.jeanlucmakiola.agendula.action.TODAY"
         private const val ACTION_OPEN_SMART = "de.jeanlucmakiola.agendula.action.OPEN_SMART"
@@ -235,9 +200,11 @@ class MainActivity : ComponentActivity() {
 
         internal fun navRequestOf(intent: Intent?): NavRequest? {
             if (intent == null) return null
-            intent.getLongExtra(SyncNoticeNotifier.EXTRA_SIGN_IN_ACCOUNT_ID, -1L).takeIf { it > 0L }
-                ?.let { return NavRequest.OpenAccount(it) }
-            if (intent.getBooleanExtra(EXTRA_OPEN_ACCOUNTS, false)) return NavRequest.OpenAccounts
+            if (BuildConfig.SYNC_ENABLED) {
+                intent.getLongExtra(EXTRA_SIGN_IN_ACCOUNT_ID, -1L).takeIf { it > 0L }
+                    ?.let { return NavRequest.OpenAccount(it) }
+                if (intent.getBooleanExtra(EXTRA_OPEN_ACCOUNTS, false)) return NavRequest.OpenAccounts
+            }
             when (intent.action) {
                 ACTION_NEW_TASK -> return NavRequest.NewTask(
                     listId = intent.getLongExtra(EXTRA_PRESET_LIST_ID, -1L).takeIf { it > 0L },

app/src/main/java/de/jeanlucmakiola/agendula/data/di/ChannelRefresher.kt

@@ -0,0 +1,22 @@
+package de.jeanlucmakiola.agendula.data.di
+
+import dagger.Module
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+import dagger.multibindings.Multibinds
+
+/**
+ * A notification channel a build variant adds, re-created in the current
+ * language on start and on a configuration change. The `full` flavor
+ * contributes the sync notices; `offline` has none.
+ */
+fun interface ChannelRefresher {
+    fun refreshChannel()
+}
+
+@Module
+@InstallIn(SingletonComponent::class)
+abstract class ChannelRefresherModule {
+    @Multibinds
+    abstract fun channelRefreshers(): Set<ChannelRefresher>
+}

app/src/main/java/de/jeanlucmakiola/agendula/data/di/DataModule.kt

@@ -12,13 +12,6 @@ import dagger.Provides
 import dagger.hilt.InstallIn
 import dagger.hilt.android.qualifiers.ApplicationContext
 import dagger.hilt.components.SingletonComponent
-import de.jeanlucmakiola.agendula.data.sync.AccountCreator
-import de.jeanlucmakiola.agendula.data.sync.AccountRepository
-import de.jeanlucmakiola.agendula.data.sync.CalDavGateway
-import de.jeanlucmakiola.agendula.data.sync.LoginFlowRecord
-import de.jeanlucmakiola.agendula.data.sync.PendingLoginFlowStore
-import de.jeanlucmakiola.agendula.data.sync.SyncOnEdit
-import de.jeanlucmakiola.agendula.data.sync.OkHttpCalDavGateway
 import de.jeanlucmakiola.agendula.data.tasks.AndroidProviderEnvironment
 import de.jeanlucmakiola.agendula.data.tasks.AndroidTasksDataSource
 import de.jeanlucmakiola.agendula.data.tasks.ModeRoutingTasksDataSource
@@ -27,7 +20,6 @@ import de.jeanlucmakiola.agendula.data.tasks.ProviderResolver
 import de.jeanlucmakiola.agendula.data.tasks.TasksDataSource
 import de.jeanlucmakiola.agendula.data.tasks.TasksRepository
 import de.jeanlucmakiola.agendula.data.tasks.TasksRepositoryImpl
-import de.jeanlucmakiola.agendula.data.tasks.room.LocalWriteListener
 import de.jeanlucmakiola.agendula.data.tasks.room.RoomTasksDataSource
 import de.jeanlucmakiola.agendula.data.tasks.room.TasksDatabase
 import androidx.datastore.core.handlers.ReplaceFileCorruptionHandler
@@ -51,37 +43,13 @@ import javax.inject.Singleton
  * reconciled", and the credential store to accounts that ask to be signed in
  * again — all states the app already knows how to be in, unlike a launch loop.
  */
-private fun replaceCorrupted() = ReplaceFileCorruptionHandler { emptyPreferences() }
+internal fun replaceCorrupted() = ReplaceFileCorruptionHandler { emptyPreferences() }
 
 private val Context.agendulaDataStore: DataStore<Preferences> by preferencesDataStore(
     name = "agendula_prefs",
     corruptionHandler = replaceCorrupted(),
 )
 
-/** See [CredentialsDataStore] for why this is a separate file. */
-private val Context.credentialsDataStore: DataStore<Preferences> by preferencesDataStore(
-    name = CREDENTIALS_DATASTORE,
-    corruptionHandler = replaceCorrupted(),
-)
-
-/** See [SyncStateDataStore] for why this is a separate file. */
-private val Context.syncStateDataStore: DataStore<Preferences> by preferencesDataStore(
-    name = SYNC_STATE_DATASTORE,
-    corruptionHandler = replaceCorrupted(),
-)
-
-/**
- * Named here and in `backup_rules.xml` / `data_extraction_rules.xml`, which
- * exclude `datastore/$CREDENTIALS_DATASTORE.preferences_pb` by this name.
- */
-const val CREDENTIALS_DATASTORE = "agendula_credentials"
-
-/**
- * Named here and in `backup_rules.xml` / `data_extraction_rules.xml`, which
- * exclude `datastore/$SYNC_STATE_DATASTORE.preferences_pb` by this name.
- */
-const val SYNC_STATE_DATASTORE = "agendula_sync_state"
-
 @Module
 @InstallIn(SingletonComponent::class)
 abstract class DataBindModule {
@@ -94,22 +62,6 @@ abstract class DataBindModule {
     @Singleton
     abstract fun bindProviderEnvironment(impl: AndroidProviderEnvironment): ProviderEnvironment
 
-    @Binds
-    @Singleton
-    abstract fun bindCalDavGateway(impl: OkHttpCalDavGateway): CalDavGateway
-
-    @Binds
-    @Singleton
-    abstract fun bindAccountCreator(impl: AccountRepository): AccountCreator
-
-    @Binds
-    @Singleton
-    abstract fun bindLoginFlowRecord(impl: PendingLoginFlowStore): LoginFlowRecord
-
-    @Binds
-    @Singleton
-    abstract fun bindLocalWriteListener(impl: SyncOnEdit): LocalWriteListener
-
     // Deliberately unqualified-free of the routing above: this is the external
     // store itself, for the one caller that has to read it while another store is
     // the active one.
@@ -128,18 +80,6 @@ object DataProvideModule {
     fun provideDataStore(@ApplicationContext context: Context): DataStore<Preferences> =
         context.agendulaDataStore
 
-    @Provides
-    @Singleton
-    @CredentialsDataStore
-    fun provideCredentialsDataStore(@ApplicationContext context: Context): DataStore<Preferences> =
-        context.credentialsDataStore
-
-    @Provides
-    @Singleton
-    @SyncStateDataStore
-    fun provideSyncStateDataStore(@ApplicationContext context: Context): DataStore<Preferences> =
-        context.syncStateDataStore
-
     @Provides
     @Singleton
     fun provideTasksDatabase(@ApplicationContext context: Context): TasksDatabase =
@@ -149,6 +89,7 @@ object DataProvideModule {
             // backed-up `.db` does not. The backup rules carry all three files and
             // the app checkpoints on ON_STOP.
             .setJournalMode(RoomDatabase.JournalMode.WRITE_AHEAD_LOGGING)
+            .addMigrations(TasksDatabase.MIGRATION_1_2)
             .build()
 
     /**

app/src/main/java/de/jeanlucmakiola/agendula/data/di/LaunchHook.kt

@@ -7,9 +7,8 @@ import dagger.hilt.components.SingletonComponent
 import dagger.multibindings.Multibinds
 
 /**
- * Something a build variant wants to run when the app is launched with [Intent].
- * Release builds contribute none; the debug source set adds the demo seeder, so
- * that class never ships.
+ * Something a build variant runs on a genuine app open (not on a configuration
+ * change): sync in the `full` flavor, the demo seeder in debug builds.
  */
 fun interface LaunchHook {
     suspend fun onLaunch(intent: Intent)

app/src/main/java/de/jeanlucmakiola/agendula/data/di/Qualifiers.kt

@@ -17,37 +17,6 @@ annotation class IoDispatcher
 @Retention(AnnotationRetention.BINARY)
 annotation class ApplicationScope
 
-/**
- * Marks the DataStore holding **only** the Keystore-encrypted app passwords.
- *
- * A separate file from `agendula_prefs` on purpose: Auto Backup includes
- * `datastore/`, and a restored ciphertext is permanently undecryptable because
- * Keystore keys are non-exportable. Its own file is what lets the backup rules
- * exclude the credentials and nothing else — excluding the whole database or
- * all of DataStore would trade a latent bug for a live one.
- */
-@Qualifier
-@Retention(AnnotationRetention.BINARY)
-annotation class CredentialsDataStore
-
-/**
- * Marks the DataStore holding per-device **sync bookkeeping** — the quarantine
- * counters and the full-reconciliation clock.
- *
- * Its own file for the same reason the credentials have one: Auto Backup
- * includes `datastore/`, and every value in here is a statement about *this*
- * device's conversation with a server. Restored onto a new install they are all
- * lies, and two of them are dangerous — a restored "reconciled recently" makes
- * the engine trust a sync token for another day, which is precisely the silently
- * pruned change log the full path exists to catch, and a restored quarantine
- * count silently skips resources that were never tried here.
- *
- * Not user data, so nothing is lost by excluding it.
- */
-@Qualifier
-@Retention(AnnotationRetention.BINARY)
-annotation class SyncStateDataStore
-
 /**
  * Marks the **external** provider's [de.jeanlucmakiola.agendula.data.tasks
  * .TasksDataSource] — the OpenTasks/tasks.org path specifically, rather than

app/src/main/java/de/jeanlucmakiola/agendula/data/sync/RemoteLists.kt

@@ -0,0 +1,52 @@
+package de.jeanlucmakiola.agendula.data.sync
+
+import de.jeanlucmakiola.agendula.data.tasks.room.AccountEntity
+
+/**
+ * Task lists that live on a server: making, renaming, recolouring and deleting
+ * them. The `full` flavor talks CalDAV; the `offline` one has no accounts, so
+ * every list is device-only and none of this is ever reached with a real one.
+ */
+interface RemoteLists {
+
+    /** Why a collection write did not happen, in a form the UI can translate. */
+    sealed interface Outcome {
+        data object Done : Outcome
+
+        /** The server said no, and will say no again. */
+        data class Refused(val code: Int) : Outcome
+
+        /** The server could not be reached. Worth another try. */
+        data object Unreachable : Outcome
+
+        /** This account cannot make collections at all — iCloud, Posteo, Google. */
+        data object Unsupported : Outcome
+
+        /** Ours is a read-only share; the write belongs to whoever owns it. */
+        data object ReadOnly : Outcome
+
+        /** The account is gone, stopped, or has no credential we can decrypt. */
+        data object NoAccount : Outcome
+
+        /**
+         * The server answered something this call cannot make sense of.
+         *
+         * ⚠️ Not [Unreachable]. `CollectionOutcome` is one type across create,
+         * update and delete, so each of them has branches the other's method
+         * can return and its own cannot — and mapping those to [Unreachable]
+         * told someone sitting on wifi that they were offline. Unreachable is a
+         * claim about the network, and this is not one.
+         */
+        data object Unexpected : Outcome
+    }
+
+    /** The accounts a new list may be created on. */
+    suspend fun creatableAccounts(): List<AccountEntity>
+
+    /** Makes a collection on [accountId]'s home set and a row pointing at it. */
+    suspend fun create(accountId: Long, name: String, color: Int): Outcome
+
+    suspend fun rename(listId: Long, name: String, color: Int): Outcome
+
+    suspend fun delete(listId: Long): Outcome
+}

app/src/main/java/de/jeanlucmakiola/agendula/data/sync/SyncRequests.kt

@@ -0,0 +1,6 @@
+package de.jeanlucmakiola.agendula.data.sync
+
+/** Asks for an account to be synced now. A no-op in the `offline` flavor. */
+fun interface SyncRequests {
+    fun syncNow(accountName: String)
+}

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/AndroidTasksDataSource.kt

@@ -1,5 +1,6 @@
 package de.jeanlucmakiola.agendula.data.tasks
 
+import android.content.ContentProviderOperation
 import android.content.ContentResolver
 import android.content.ContentUris
 import android.content.ContentValues
@@ -19,6 +20,7 @@ import de.jeanlucmakiola.agendula.domain.Task
 import de.jeanlucmakiola.agendula.domain.TaskForm
 import de.jeanlucmakiola.agendula.domain.TaskList
 import de.jeanlucmakiola.agendula.domain.export.ExportTask
+import de.jeanlucmakiola.agendula.domain.normalizeTags
 import de.jeanlucmakiola.agendula.domain.recurrence.ExpansionWindow
 import de.jeanlucmakiola.agendula.domain.recurrence.RecurrenceExpander
 import de.jeanlucmakiola.agendula.domain.recurrence.RecurrenceSpec
@@ -90,11 +92,14 @@ class AndroidTasksDataSource @Inject constructor(
         // `is_recurring` / `distance_from_current`). The by-name mapper reads
         // whatever is present and nulls the rest; the repository re-sorts, so we
         // don't depend on a provider sort column either.
-        return resolver.query(uri, null, selection, args, null)
+        val tasks = resolver.query(uri, null, selection, args, null)
             ?.use { c ->
                 val reader = CursorColumnReader(c)
                 buildList { while (c.moveToNext()) add(TaskMapper.task(reader)) }
             } ?: emptyList()
+        if (tasks.isEmpty()) return tasks
+        val tags = categories(tasks.map { it.taskId })
+        return tasks.map { task -> tags[task.taskId]?.let { task.copy(tags = it) } ?: task }
     }
 
     override fun exportTasks(listId: Long): List<ExportTask> {
@@ -102,7 +107,7 @@ class AndroidTasksDataSource @Inject constructor(
         // table's shape varies across provider versions, and the by-name mapper
         // reads what's there.
         val uri = TasksContract.tasksUri(authority())
-        return resolver.query(
+        val tasks = resolver.query(
             uri,
             null,
             // _deleted marks a row awaiting a sync round-trip. It's gone as far as
@@ -115,21 +120,39 @@ class AndroidTasksDataSource @Inject constructor(
             val reader = CursorColumnReader(c)
             buildList { while (c.moveToNext()) add(TaskMapper.exportTask(reader)) }
         } ?: emptyList()
+        if (tasks.isEmpty()) return tasks
+        val tags = categories(tasks.map { it.taskId })
+        return tasks.map { task -> tags[task.taskId]?.let { task.copy(tags = it) } ?: task }
     }
 
     // --- writes ---------------------------------------------------------------
 
     override fun insertTask(form: TaskForm): Long {
         val values = TaskWriteMapper.seriesValues(form, ZoneId.systemDefault().id)
-        val uri = resolver.insert(TasksContract.tasksUri(authority()), values.toContentValues())
-            ?: throw TaskWriteFailedException("insert task")
-        return uri.lastPathSegment?.toLongOrNull() ?: throw TaskWriteFailedException("insert task: no id")
+        // One batch, so a refused tag leaves no task behind for a retry to duplicate.
+        val authority = authority()
+        val ops = arrayListOf(
+            ContentProviderOperation.newInsert(TasksContract.tasksUri(authority))
+                .withValues(values.toContentValues())
+                .build(),
+        )
+        normalizeTags(form.tags).forEach { tag ->
+            ops += ContentProviderOperation.newInsert(TasksContract.propertiesUri(authority))
+                .withValues(TaskWriteMapper.categoryValues(0, tag).toContentValues().apply { remove(Properties.TASK_ID) })
+                .withValueBackReference(Properties.TASK_ID, 0)
+                .build()
+        }
+        val results = runCatching { resolver.applyBatch(authority, ops) }
+            .getOrElse { throw TaskWriteFailedException("insert task", it) }
+        return results.firstOrNull()?.uri?.lastPathSegment?.toLongOrNull()
+            ?: throw TaskWriteFailedException("insert task: no id")
     }
 
     override fun updateTask(taskId: Long, form: TaskForm) {
         val values = TaskWriteMapper.seriesValues(form, ZoneId.systemDefault().id)
         val rows = resolver.update(taskUri(authority(), taskId), values.toContentValues(), null, null)
         if (rows == 0) throw TaskWriteFailedException("update task $taskId")
+        setCategories(taskId, form.tags)
     }
 
     override fun updateSeries(seriesId: Long, occurrenceStart: Instant, form: TaskForm) {
@@ -151,6 +174,7 @@ class AndroidTasksDataSource @Inject constructor(
             (Tasks.DUE to shifted(anchors?.second, occurrence?.due, form.due))
         val rows = resolver.update(taskUri(authority(), seriesId), values.toContentValues(), null, null)
         if (rows == 0) throw TaskWriteFailedException("update series $seriesId")
+        setCategories(seriesId, form.tags)
     }
 
     /**
@@ -243,8 +267,28 @@ class AndroidTasksDataSource @Inject constructor(
             ?: throw TaskWriteFailedException("update instance $taskId@$occurrenceStart: no such occurrence")
         val values = TaskWriteMapper.instanceValues(form, ZoneId.systemDefault().id)
         val uri = TasksContract.instanceUri(authority(), instanceId)
-        val rows = resolver.update(uri, values.toContentValues(), null, null)
-        if (rows == 0) throw TaskWriteFailedException("update instance $instanceId")
+        // The fork copies the series' properties onto the override, so the tags
+        // go onto the series first and are put back once the override exists.
+        // Unchanged tags are inherited as they are, and the series is left alone.
+        val seriesTags = categories(listOf(taskId))[taskId].orEmpty()
+        val retag = normalizeTags(form.tags) != seriesTags
+        if (retag) setCategories(taskId, form.tags)
+        var failure: Throwable? = null
+        try {
+            val rows = resolver.update(uri, values.toContentValues(), null, null)
+            if (rows == 0) throw TaskWriteFailedException("update instance $instanceId")
+        } catch (e: Throwable) {
+            failure = e
+            throw e
+        } finally {
+            if (retag) {
+                try {
+                    setCategories(taskId, seriesTags)
+                } catch (e: Throwable) {
+                    failure?.addSuppressed(e) ?: throw e
+                }
+            }
+        }
     }
 
     /**
@@ -348,6 +392,58 @@ class AndroidTasksDataSource @Inject constructor(
         } ?: emptyList()
     }
 
+    /** Tags by task id for [taskIds], in stored order. */
+    private fun categories(taskIds: Collection<Long>): Map<Long, List<String>> {
+        val rows = taskIds.distinct().chunked(MAX_SQL_ARGS - 1).flatMap { chunk ->
+            val selection = "${Properties.MIMETYPE} = ? AND ${Properties.TASK_ID} IN (${chunk.joinToString(",") { "?" }})"
+            val args = (listOf(TasksContract.Category.MIMETYPE) + chunk.map(Long::toString)).toTypedArray()
+            resolver.query(
+                TasksContract.propertiesUri(authority()),
+                arrayOf(Properties.TASK_ID, TasksContract.Category.NAME),
+                selection,
+                args,
+                Properties.PROPERTY_ID,
+            )?.use { c ->
+                val reader = CursorColumnReader(c)
+                buildList {
+                    while (c.moveToNext()) {
+                        val id = reader.getLong(Properties.TASK_ID) ?: continue
+                        val name = reader.getString(TasksContract.Category.NAME) ?: continue
+                        add(id to name)
+                    }
+                }
+            } ?: emptyList()
+        }
+        return rows.groupBy({ it.first }, { it.second }).mapValues { normalizeTags(it.value) }
+    }
+
+    /**
+     * Replaces [taskId]'s category rows in one batch, so a refused insert cannot
+     * leave half the tags, and leaves them alone when nothing changed so the task
+     * isn't dirtied.
+     */
+    private fun setCategories(taskId: Long, tags: List<String>) {
+        val wanted = normalizeTags(tags)
+        if (categories(listOf(taskId))[taskId].orEmpty() == wanted) return
+        val authority = authority()
+        val uri = TasksContract.propertiesUri(authority)
+        val ops = arrayListOf(
+            ContentProviderOperation.newDelete(uri)
+                .withSelection(
+                    "${Properties.TASK_ID} = ? AND ${Properties.MIMETYPE} = ?",
+                    arrayOf(taskId.toString(), TasksContract.Category.MIMETYPE),
+                )
+                .build(),
+        )
+        wanted.forEach {
+            ops += ContentProviderOperation.newInsert(uri)
+                .withValues(TaskWriteMapper.categoryValues(taskId, it).toContentValues())
+                .build()
+        }
+        runCatching { resolver.applyBatch(authority, ops) }
+            .getOrElse { throw TaskWriteFailedException("set categories for task $taskId", it) }
+    }
+
     override fun setCancelled(taskId: Long, cancelled: Boolean) {
         val rows = resolver.update(taskUri(authority(), taskId), cancelValues(cancelled).toContentValues(), null, null)
         if (rows == 0) throw TaskWriteFailedException("cancel task $taskId")
@@ -460,3 +556,6 @@ class AndroidTasksDataSource @Inject constructor(
         return cv
     }
 }
+
+/** SQLite's default bound-argument limit on older Android releases. */
+private const val MAX_SQL_ARGS = 999

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/Failures.kt

@@ -5,8 +5,8 @@ class ProviderUnavailableException :
     IllegalStateException("No tasks provider installed")
 
 /** A ContentResolver write returned no URI or affected no rows. */
-class TaskWriteFailedException(operation: String) :
-    RuntimeException("Task write failed: $operation")
+class TaskWriteFailedException(operation: String, cause: Throwable? = null) :
+    RuntimeException("Task write failed: $operation", cause)
 
 /**
  * The task changed (e.g. a DAVx5 sync or another app) since the edit form loaded

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/TaskWriteMapper.kt

@@ -113,6 +113,12 @@ object TaskWriteMapper {
         Alarm.ALARM_TYPE to Alarm.TYPE_MESSAGE,
     )
 
+    fun categoryValues(taskId: Long, name: String): Map<String, Any?> = mapOf(
+        Properties.TASK_ID to taskId,
+        Properties.MIMETYPE to TasksContract.Category.MIMETYPE,
+        TasksContract.Category.NAME to name,
+    )
+
     /** The user-owned columns of a list — what an edit is allowed to change. */
     fun listValues(name: String, color: Int): Map<String, Any?> = mapOf(
         Lists.NAME to name.trim(),

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/TasksContract.kt

@@ -154,6 +154,18 @@ object TasksContract {
         const val TYPE_MESSAGE = 1
     }
 
+    /**
+     * A category property row — one tag. DAVx5 maps these to and from
+     * `CATEGORIES`. Inserting with only [NAME] is enough: the provider looks the
+     * category up in the task's account, or creates it, and fills in `data0`.
+     */
+    object Category {
+        const val MIMETYPE = "vnd.android.cursor.item/category"
+
+        /** `data1` — the tag as spelled. */
+        const val NAME = "data1"
+    }
+
     fun propertiesUri(authority: String): Uri = "content://$authority/${Properties.PATH}".toUri()
 
     // --- status values (TaskColumns.STATUS_*) --------------------------------

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/TasksRepositoryImpl.kt

@@ -66,6 +66,7 @@ class TasksRepositoryImpl @Inject constructor(
             // Same over-read as Smart: TaskQuery.listId only narrows to one list, so
             // several lists are read in full and membership is filtered in-memory.
             is TaskFilter.OfLists -> TaskQuery(includeCompleted = true)
+            is TaskFilter.Tagged -> TaskQuery(includeCompleted = true)
         }
         val (todayStart, todayEnd) = DayWindow.today(Clock.System.now(), ZoneId.systemDefault())
         val all = SeriesCollapse.visible(dataSource.tasks(query))
@@ -112,6 +113,7 @@ class TasksRepositoryImpl @Inject constructor(
                 parentId = parentId,
                 location = task.location,
                 url = task.url,
+                tags = task.tags,
             ),
         )
         val reminders = dataSource.reminders()[task.taskId].orEmpty()

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/ical/VTodoMapper.kt

@@ -9,6 +9,7 @@ import de.jeanlucmakiola.agendula.domain.ical.ICalParser
 import de.jeanlucmakiola.agendula.domain.ical.ICalProperty
 import de.jeanlucmakiola.agendula.domain.ical.ICalSerializer
 import de.jeanlucmakiola.agendula.domain.ical.ICalValues
+import de.jeanlucmakiola.agendula.domain.normalizeTags
 import java.time.ZoneId
 import kotlin.time.Clock
 import kotlin.time.Instant
@@ -81,6 +82,8 @@ object VTodoMapper {
         // Parameterised copies stay in the residue verbatim; authoring the
         // column beside them would emit the same exclusions twice.
         "RDATE", "EXDATE",
+        // Several lines, or one the column would not re-serialise exactly.
+        "CATEGORIES",
     )
 
     /** What a VTODO yields. Row identity ([TaskEntity.id], `listId`) is the caller's. */
@@ -200,6 +203,9 @@ object VTodoMapper {
             CLASS_NAMES.indexOf(classProperty?.value?.trim()?.uppercase()).takeIf { it >= 0 },
         )
 
+        val (categories, categoriesProperty) = readCategories(vtodo)
+        claim(categoriesProperty)
+
         val sequenceProperty = vtodo.property("SEQUENCE")
         val sequence = take(
             sequenceProperty,
@@ -225,6 +231,7 @@ object VTodoMapper {
             title = take(vtodo.property("SUMMARY"), vtodo.property("SUMMARY")?.text()),
             description = take(vtodo.property("DESCRIPTION"), vtodo.property("DESCRIPTION")?.text()),
             location = take(vtodo.property("LOCATION"), vtodo.property("LOCATION")?.text()),
+            categories = categories,
             // URI, not TEXT — escaping it would corrupt a query string.
             url = take(vtodo.property("URL"), vtodo.property("URL")?.value?.trim()),
             status = status,
@@ -284,8 +291,9 @@ object VTodoMapper {
         now: Instant = Clock.System.now(),
     ): ICalComponent {
         val residue = parseResidue(entity.unknownProperties)
+        val residueCategories = normalizeTags(residue.properties("CATEGORIES").flatMap(::categoryValues))
         val keptResidue =
-            residue.properties.filterNot { contradictsResidue(it, residue, entity, parentUid) }
+            residue.properties.filterNot { contradictsResidue(it, residue, residueCategories, entity, parentUid) }
         val suppressed = keptResidue
             .map { it.name.uppercase() }
             .filterTo(mutableSetOf()) { it in SUPPRESSED_BY_RESIDUE }
@@ -307,6 +315,7 @@ object VTodoMapper {
         add("DESCRIPTION", entity.description?.let(ICalValues::escapeText))
         add("LOCATION", entity.location?.let(ICalValues::escapeText))
         add("URL", entity.url)
+        add("CATEGORIES", normalizeTags(entity.categories).takeIf { it.isNotEmpty() }?.let(ICalValues::formatTextList))
 
         add("STATUS", entity.status.toICalName())
         add("PERCENT-COMPLETE", entity.percentComplete?.toString())
@@ -386,6 +395,7 @@ object VTodoMapper {
     private fun contradictsResidue(
         property: ICalProperty,
         residue: ICalComponent,
+        residueCategories: List<String>,
         entity: TaskEntity,
         parentUid: String?,
     ): Boolean {
@@ -433,6 +443,7 @@ object VTodoMapper {
             "PRIORITY" -> entity.priority != PRIORITY_NONE
             "PERCENT-COMPLETE" -> entity.percentComplete != null
             "CLASS" -> entity.classification != null
+            "CATEGORIES" -> entity.categories != residueCategories
             // Not SEQUENCE: it is the organiser's counter and never ours to bump,
             // so the column stays at its fallback and the residue always wins.
             else -> false
@@ -475,6 +486,23 @@ object VTodoMapper {
 
     // -------------------------------------------------------------- helpers
 
+    /**
+     * Every `CATEGORIES` copy's values, merged, and the one line to claim — only
+     * when it is the sole, parameterless copy and the column re-serialises it
+     * byte for byte. Anything else is read for display and stays in the residue.
+     */
+    private fun readCategories(vtodo: ICalComponent): Pair<List<String>, ICalProperty?> {
+        val copies = vtodo.properties("CATEGORIES")
+        val values = normalizeTags(copies.flatMap(::categoryValues))
+        val claimable = copies.singleOrNull()?.takeIf {
+            it.params.isEmpty() && values.isNotEmpty() && ICalValues.formatTextList(values) == it.value
+        }
+        return values to claimable
+    }
+
+    private fun categoryValues(property: ICalProperty): List<String> =
+        normalizeTags(ICalValues.parseTextList(property.value))
+
     private val CLASS_NAMES = listOf("PUBLIC", "PRIVATE", "CONFIDENTIAL")
 
     private class TimeRead(

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/legacy/OneShotImport.kt

@@ -15,6 +15,7 @@ import de.jeanlucmakiola.agendula.data.tasks.room.TaskEntity
 import de.jeanlucmakiola.agendula.data.tasks.room.TaskListEntity
 import de.jeanlucmakiola.agendula.data.tasks.room.TasksDatabase
 import de.jeanlucmakiola.agendula.domain.PRIORITY_NONE
+import de.jeanlucmakiola.agendula.domain.normalizeTags
 import de.jeanlucmakiola.agendula.domain.statusFromInt
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.Flow
@@ -221,12 +222,17 @@ class OneShotImport @Inject constructor(
             }
 
         val alarms = mutableListOf<LegacyAlarm>()
-        db.rawQuery("SELECT task_id, mimetype, data0, data1, data2 FROM Properties", null)
+        val categories = mutableMapOf<Long, MutableList<String>>()
+        db.rawQuery("SELECT task_id, mimetype, data0, data1, data2 FROM Properties ORDER BY property_id", null)
             .use { cursor ->
                 val r = CursorColumnReader(cursor)
                 while (cursor.moveToNext()) {
-                    if (r.getString("mimetype") != ALARM_MIMETYPE) continue
                     val taskId = r.getLong("task_id") ?: continue
+                    if (r.getString("mimetype") == CATEGORY_MIMETYPE) {
+                        r.getString("data1")?.let { categories.getOrPut(taskId, ::mutableListOf) += it }
+                        continue
+                    }
+                    if (r.getString("mimetype") != ALARM_MIMETYPE) continue
                     val minutes = r.getString("data0")?.trim()?.toIntOrNull() ?: continue
                     alarms += LegacyAlarm(
                         taskId = taskId,
@@ -241,7 +247,7 @@ class OneShotImport @Inject constructor(
                 }
             }
 
-        return LegacySnapshot(lists, rows, alarms)
+        return LegacySnapshot(lists, rows, alarms, categories.mapValues { normalizeTags(it.value) })
     }
 
     // --- writing into Room ----------------------------------------------------
@@ -276,7 +282,12 @@ class OneShotImport @Inject constructor(
             // the unique index; a fresh uid costs the row nothing it still has.
             val uid = row.entity.uid.takeIf { seen.add(Triple(listId, it, recurrenceId)) }
                 ?: UUID.randomUUID().toString()
-            val entity = row.entity.copy(listId = listId, uid = uid, recurrenceId = recurrenceId)
+            val entity = row.entity.copy(
+                listId = listId,
+                uid = uid,
+                recurrenceId = recurrenceId,
+                categories = snapshot.categories[row.id].orEmpty(),
+            )
             val newId = taskDao.insert(entity)
             taskIds[row.id] = newId
             inserted += row to entity.copy(id = newId)
@@ -379,6 +390,7 @@ class OneShotImport @Inject constructor(
         const val ARCHIVE_NAME = "tasks.db.imported"
 
         private const val ALARM_MIMETYPE = "vnd.android.cursor.item/alarm"
+        private const val CATEGORY_MIMETYPE = "vnd.android.cursor.item/category"
         private const val REFERENCE_START = "2"
         private val SIDECARS = listOf("-journal", "-wal", "-shm")
         private val IMPORT_DONE = booleanPreferencesKey("legacy_import_done")
@@ -391,6 +403,8 @@ private class LegacySnapshot(
     val lists: List<LegacyList>,
     val tasks: List<LegacyTaskRow>,
     val alarms: List<LegacyAlarm>,
+    /** Tags by legacy task `_id`. */
+    val categories: Map<Long, List<String>>,
 )
 
 private class LegacyList(val id: Long, val entity: TaskListEntity)

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/room/CategoriesLift.kt

@@ -0,0 +1,44 @@
+package de.jeanlucmakiola.agendula.data.tasks.room
+
+import de.jeanlucmakiola.agendula.domain.ical.ICalComponent
+import de.jeanlucmakiola.agendula.domain.ical.ICalParser
+import de.jeanlucmakiola.agendula.domain.ical.ICalProperty
+import de.jeanlucmakiola.agendula.domain.ical.ICalSerializer
+import de.jeanlucmakiola.agendula.domain.ical.ICalValues
+
+/**
+ * Lifts `CATEGORIES` out of a residue written before v2 claimed it.
+ *
+ * ⚠️ Frozen with [TasksDatabase.MIGRATION_1_2]. The claim rule is copied here
+ * rather than shared with the mapper, so a later change to what the mapper
+ * claims cannot change what this migration produced for an earlier upgrader.
+ */
+internal object CategoriesLift {
+
+    /**
+     * Every copy's values merged, and the residue with the one claimed line
+     * removed — or `null` for the residue when nothing was claimed, so the caller
+     * leaves the stored one alone.
+     */
+    data class Result(val categories: List<String>, val residue: String?, val claimed: Boolean)
+
+    fun lift(residue: String?): Result {
+        val component = parse(residue) ?: return Result(emptyList(), residue, claimed = false)
+        val copies = component.properties.filter { it.name.equals("CATEGORIES", ignoreCase = true) }
+        val values = copies.flatMap(::values)
+        val claim = copies.singleOrNull()?.takeIf {
+            it.params.isEmpty() && values.isNotEmpty() && ICalValues.formatTextList(values) == it.value
+        } ?: return Result(values, residue, claimed = false)
+        val rest = ICalSerializer.serializeProperties(component.properties.filterNot { it === claim }) +
+            ICalSerializer.serializeAll(component.components)
+        return Result(values, rest.ifEmpty { null }, claimed = true)
+    }
+
+    private fun values(property: ICalProperty): List<String> =
+        ICalValues.parseTextList(property.value).map(String::trim).filter(String::isNotEmpty).distinct()
+
+    private fun parse(text: String?): ICalComponent? {
+        if (text.isNullOrEmpty()) return null
+        return runCatching { ICalParser.parse("BEGIN:VTODO\r\n$text\r\nEND:VTODO\r\n") }.getOrNull()
+    }
+}

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/room/Converters.kt

@@ -2,6 +2,8 @@ package de.jeanlucmakiola.agendula.data.tasks.room
 
 import androidx.room.TypeConverter
 import de.jeanlucmakiola.agendula.domain.TaskStatus
+import de.jeanlucmakiola.agendula.domain.ical.ICalValues
+import de.jeanlucmakiola.agendula.domain.normalizeTags
 import de.jeanlucmakiola.agendula.domain.statusFromInt
 import de.jeanlucmakiola.agendula.domain.toInt
 import kotlin.time.Instant
@@ -36,3 +38,17 @@ object Converters {
     fun alarmReferenceFrom(value: String): AlarmReference =
         runCatching { AlarmReference.valueOf(value) }.getOrDefault(AlarmReference.DUE)
 }
+
+/**
+ * [TaskEntity.categories] stored as a `CATEGORIES` value, so escaping has one
+ * home; empty when there are none. Scoped to that field rather than the
+ * database, so no other `List<String>` picks up iCalendar escaping by accident.
+ */
+object CategoriesConverter {
+    @TypeConverter
+    fun toText(value: List<String>): String = ICalValues.formatTextList(normalizeTags(value))
+
+    @TypeConverter
+    fun fromText(value: String): List<String> =
+        if (value.isEmpty()) emptyList() else normalizeTags(ICalValues.parseTextList(value))
+}

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/room/Entities.kt

@@ -5,6 +5,7 @@ import androidx.room.Entity
 import androidx.room.ForeignKey
 import androidx.room.Index
 import androidx.room.PrimaryKey
+import androidx.room.TypeConverters
 import de.jeanlucmakiola.agendula.domain.PRIORITY_NONE
 import de.jeanlucmakiola.agendula.domain.TaskStatus
 import kotlin.time.Instant
@@ -71,7 +72,7 @@ data class TaskListEntity(
      *
      * ⚠️ It was set by a rename and read by nobody. A collection's name and
      * colour are now written server-first by
-     * [de.jeanlucmakiola.agendula.data.sync.RemoteListRepository], so there is
+     * [de.jeanlucmakiola.agendula.data.sync.RemoteLists], so there is
      * no local edit left waiting to be pushed — and a flag that means "owed to
      * the server" while nothing ever pays it is worse than no flag at all.
      */
@@ -143,6 +144,10 @@ data class TaskEntity(
     @ColumnInfo(name = "url") val url: String? = null,
     /** ARGB override for the list colour. */
     @ColumnInfo(name = "color") val color: Int? = null,
+    /** RFC 5545 `CATEGORIES` — the tags — in the spelling each task carries them. */
+    @ColumnInfo(name = "categories", defaultValue = "")
+    @field:TypeConverters(CategoriesConverter::class)
+    val categories: List<String> = emptyList(),
 
     // state
     @ColumnInfo(name = "status", defaultValue = "0") val status: TaskStatus = TaskStatus.NEEDS_ACTION,

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/room/RoomTaskMapper.kt

@@ -49,6 +49,7 @@ object RoomTaskMapper {
         description = row.task.description,
         location = row.task.location,
         url = row.task.url,
+        tags = row.task.categories,
         priority = priorityFromICal(row.task.priority),
         status = row.task.status,
         percentComplete = row.task.percentComplete,
@@ -79,6 +80,7 @@ object RoomTaskMapper {
         description = task.description,
         location = task.location,
         url = task.url,
+        tags = task.categories,
         priority = priorityFromICal(task.priority),
         status = task.status,
         percentComplete = task.percentComplete,

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/room/RoomTasksDataSource.kt

@@ -520,7 +520,7 @@ class RoomTasksDataSource @Inject constructor(
 
     /**
      * ⚠️ Device-only lists. An account-backed collection is renamed through
-     * [de.jeanlucmakiola.agendula.data.sync.RemoteListRepository], which sends
+     * [de.jeanlucmakiola.agendula.data.sync.RemoteLists], which sends
      * the PROPPATCH first and writes here only once the server has taken it.
      *
      * This used to set `is_dirty` for an account list instead, on the theory

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/room/TaskFormWriter.kt

@@ -3,6 +3,7 @@ package de.jeanlucmakiola.agendula.data.tasks.room
 import de.jeanlucmakiola.agendula.domain.TaskForm
 import de.jeanlucmakiola.agendula.domain.TaskStatus
 import de.jeanlucmakiola.agendula.domain.ical.ICalValues
+import de.jeanlucmakiola.agendula.domain.normalizeTags
 import de.jeanlucmakiola.agendula.domain.toICal
 import kotlin.time.Duration.Companion.days
 import kotlin.time.Duration.Companion.seconds
@@ -50,6 +51,7 @@ object TaskFormWriter {
             description = form.description?.trim()?.ifBlank { null },
             location = form.location?.trim()?.ifBlank { null },
             url = form.url?.trim()?.ifBlank { null },
+            categories = normalizeTags(form.tags),
             priority = form.priority.toICal(),
             percentComplete = percent,
             status = statusFor(percent, current.status),

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/room/TasksDatabase.kt

@@ -3,6 +3,8 @@ package de.jeanlucmakiola.agendula.data.tasks.room
 import androidx.room.Database
 import androidx.room.RoomDatabase
 import androidx.room.TypeConverters
+import androidx.room.migration.Migration
+import androidx.sqlite.db.SupportSQLiteDatabase
 
 /**
  * Agendula's own task store. Four tables, designed from
@@ -18,7 +20,7 @@ import androidx.room.TypeConverters
         TaskEntity::class,
         TaskAlarmEntity::class,
     ],
-    version = 1,
+    version = 2,
     exportSchema = true,
 )
 @TypeConverters(Converters::class)
@@ -30,5 +32,36 @@ abstract class TasksDatabase : RoomDatabase() {
 
     companion object {
         const val NAME = "agendula-tasks.db"
+
+        /**
+         * v2 adds `categories`. Until then `CATEGORIES` lived in the residue, and
+         * an unchanged task is never downloaded again, so the values are lifted
+         * out here. Not marked dirty: nothing changed on the server's side.
+         */
+        val MIGRATION_1_2 = object : Migration(1, 2) {
+            override fun migrate(db: SupportSQLiteDatabase) {
+                db.execSQL("ALTER TABLE tasks ADD COLUMN categories TEXT NOT NULL DEFAULT ''")
+                val lifted = mutableListOf<Pair<Long, CategoriesLift.Result>>()
+                db.query(
+                    "SELECT id, unknown_properties FROM tasks WHERE unknown_properties LIKE '%CATEGORIES%'",
+                ).use { cursor ->
+                    while (cursor.moveToNext()) {
+                        val result = CategoriesLift.lift(cursor.getString(1))
+                        if (result.categories.isNotEmpty()) lifted += cursor.getLong(0) to result
+                    }
+                }
+                lifted.forEach { (id, result) ->
+                    val categories = CategoriesConverter.toText(result.categories)
+                    if (result.claimed) {
+                        db.execSQL(
+                            "UPDATE tasks SET categories = ?, unknown_properties = ? WHERE id = ?",
+                            arrayOf<Any?>(categories, result.residue, id),
+                        )
+                    } else {
+                        db.execSQL("UPDATE tasks SET categories = ? WHERE id = ?", arrayOf<Any?>(categories, id))
+                    }
+                }
+            }
+        }
     }
 }

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/transfer/ExternalImport.kt

@@ -16,6 +16,7 @@ import de.jeanlucmakiola.agendula.data.tasks.room.TaskListEntity
 import de.jeanlucmakiola.agendula.data.tasks.room.TasksDatabase
 import de.jeanlucmakiola.agendula.domain.TaskList
 import de.jeanlucmakiola.agendula.domain.export.ExportTask
+import de.jeanlucmakiola.agendula.domain.normalizeTags
 import de.jeanlucmakiola.agendula.domain.toICal
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
@@ -213,6 +214,7 @@ class ExternalImport @Inject constructor(
         description = description,
         location = location,
         url = url,
+        categories = normalizeTags(tags),
         status = status,
         percentComplete = percentComplete,
         completedAt = completedAt,

app/src/main/java/de/jeanlucmakiola/agendula/domain/Models.kt

@@ -52,6 +52,8 @@ data class Task(
     val description: String?,
     val location: String?,
     val url: String?,
+    /** `CATEGORIES`, as the task spells them. */
+    val tags: List<String> = emptyList(),
     val priority: Priority,
     val status: TaskStatus,
     val percentComplete: Int?,
@@ -161,3 +163,10 @@ fun TaskStatus.toInt(): Int = when (this) {
     TaskStatus.COMPLETED -> ICalStatus.COMPLETED
     TaskStatus.CANCELLED -> ICalStatus.CANCELLED
 }
+
+/** Tags as every writer stores them: trimmed, no blanks, each spelling once, order kept. */
+fun normalizeTags(tags: List<String>): List<String> = tags.map(String::trim).filter(String::isNotEmpty).distinct()
+
+/** Every tag on [tasks], each spelling once, alphabetically ignoring case. */
+fun tagsInUse(tasks: Iterable<Task>): List<String> =
+    tasks.flatMap { it.tags }.distinct().sortedWith(String.CASE_INSENSITIVE_ORDER)

app/src/main/java/de/jeanlucmakiola/agendula/domain/TaskFilter.kt

@@ -5,12 +5,14 @@ import kotlin.time.Instant
 /** The built-in "smart" lists, computed from due dates rather than membership. */
 enum class SmartList { ALL, TODAY, UPCOMING, OVERDUE, NO_DATE, COMPLETED }
 
-/** What a task screen is showing: one real list, or a smart list. */
+/** What a task screen is showing: one real list, a smart list, or a tag. */
 sealed interface TaskFilter {
     data class OfList(val listId: Long) : TaskFilter
     /** Several lists shown together, e.g. one widget covering more than one list. */
     data class OfLists(val listIds: Set<Long>) : TaskFilter
     data class Smart(val list: SmartList) : TaskFilter
+    /** Every task carrying [tag], open and completed, across all lists. */
+    data class Tagged(val tag: String) : TaskFilter
 }
 
 /**
@@ -25,8 +27,12 @@ object TaskFiltering {
             is TaskFilter.OfList -> task.listId == filter.listId
             is TaskFilter.OfLists -> task.listId in filter.listIds
             is TaskFilter.Smart -> matchesSmart(task, filter.list, todayStart, todayEnd)
+            is TaskFilter.Tagged -> filter.tag in task.tags
         }
 
+    /** Whether [task] carries every one of [tags]; an empty set matches everything. */
+    fun hasAllTags(task: Task, tags: Set<String>): Boolean = task.tags.containsAll(tags)
+
     private fun matchesSmart(task: Task, list: SmartList, todayStart: Instant, todayEnd: Instant): Boolean {
         val due = task.due
         return when (list) {

app/src/main/java/de/jeanlucmakiola/agendula/domain/TaskForm.kt

@@ -22,6 +22,7 @@ data class TaskForm(
     val reminders: List<Int> = emptyList(),
     val location: String? = null,
     val url: String? = null,
+    val tags: List<String> = emptyList(),
     /** The series' `RRULE` value; `null` = does not repeat. Ignored for a single-occurrence edit. */
     val rrule: String? = null,
 ) {
@@ -44,7 +45,7 @@ enum class TaskFormError { BLANK_TITLE, NO_LIST, DUE_BEFORE_START, REMINDER_WITH
  * a setting; the rest unfold on demand. Declaring these as an enum keeps the
  * disclosure generic, so adding a field later is one entry plus its card.
  */
-enum class TaskFormField { Description, Recurrence, Priority, Progress, Parent, Reminder, Location, Url }
+enum class TaskFormField { Description, Recurrence, Priority, Progress, Parent, Reminder, Location, Url, Tags }
 
 /** The optional fields that already carry a value — auto-revealed when editing. */
 fun TaskForm.populatedFields(): Set<TaskFormField> = buildSet {
@@ -56,4 +57,5 @@ fun TaskForm.populatedFields(): Set<TaskFormField> = buildSet {
     if (rrule != null) add(TaskFormField.Recurrence)
     if (!location.isNullOrBlank()) add(TaskFormField.Location)
     if (!url.isNullOrBlank()) add(TaskFormField.Url)
+    if (tags.isNotEmpty()) add(TaskFormField.Tags)
 }

app/src/main/java/de/jeanlucmakiola/agendula/domain/export/ExportModels.kt

@@ -42,6 +42,7 @@ data class ExportTask(
     val rdate: String?,
     /** `tasks._id` of the parent, for `RELATED-TO;RELTYPE=PARENT`. */
     val parentId: Long?,
+    val tags: List<String> = emptyList(),
 )
 
 /** A task list and everything in it, ready to become one `.ics` document. */

app/src/main/java/de/jeanlucmakiola/agendula/domain/export/ICalendarWriter.kt

@@ -88,6 +88,7 @@ object ICalendarWriter {
         task.location?.takeIf { it.isNotBlank() }?.let { property("LOCATION", it) }
         // URL is a URI, not TEXT: it must not be escaped like one.
         task.url?.takeIf { it.isNotBlank() }?.let { rawProperty("URL", it) }
+        task.tags.takeIf { it.isNotEmpty() }?.let { rawProperty("CATEGORIES", ICalValues.formatTextList(it)) }
 
         task.start?.let { dateProperty("DTSTART", it, task.isAllDay) }
         task.due?.let { dateProperty("DUE", it, task.isAllDay) }

app/src/main/java/de/jeanlucmakiola/agendula/domain/ical/ICalValues.kt

@@ -49,6 +49,37 @@ object ICalValues {
         return out.toString()
     }
 
+    /**
+     * A multi-valued TEXT property (`CATEGORIES`, §3.8.1.2): split on the
+     * commas that are not escaped, then unescape each value.
+     */
+    fun parseTextList(value: String): List<String> {
+        val values = mutableListOf<String>()
+        val current = StringBuilder()
+        var i = 0
+        while (i < value.length) {
+            val c = value[i]
+            when {
+                c == '\\' && i + 1 < value.length -> {
+                    current.append(c).append(value[i + 1])
+                    i += 2
+                    continue
+                }
+                c == ',' -> {
+                    values += unescapeText(current.toString())
+                    current.clear()
+                }
+                else -> current.append(c)
+            }
+            i++
+        }
+        values += unescapeText(current.toString())
+        return values
+    }
+
+    /** The inverse of [parseTextList]. */
+    fun formatTextList(values: List<String>): String = values.joinToString(",", transform = ::escapeText)
+
     /** How a DATE / DATE-TIME property was written, and whether we can reproduce it. */
     sealed interface TimeValue {
         /** `VALUE=DATE` — date-only. */