diff --git a/.junie/extensions.json b/.junie/extensions.json
new file mode 100644
index 0000000..119f90d
--- /dev/null
+++ b/.junie/extensions.json
@@ -0,0 +1,13 @@
+{
+    "github-JetBrains-junie-extensions": {
+        "url": "https://github.com/JetBrains/junie-extensions",
+        "extensions": [
+            "context7",
+            "kotlin-engineer"
+        ],
+        "source": {
+            "type": "git",
+            "url": "https://github.com/JetBrains/junie-extensions"
+        }
+    }
+}
\ No newline at end of file
diff --git a/.junie/plans/custom-application.md b/.junie/plans/custom-application.md
new file mode 100644
index 0000000..58ea709
--- /dev/null
+++ b/.junie/plans/custom-application.md
@@ -0,0 +1,89 @@
+# Requirements
+
+### Behavior
+- The **IDE icon** selector gains a **Custom** option in both settings pages: the main project page ("Cat Activity") and **Override Defaults**.
+- Selecting **Custom** reveals: **Application ID** field; a hint link below it (create an application in the Discord Developer Portal, `https://discord.com/developers/applications`); required **Application title** field; **Icon variant** selector with the same entries as `IDEIcon.entries` (New / Old / JetBrains / Cat Activity / Custom); when variant = Custom, a **Custom icon URL** field.
+- **Override Defaults**: Application ID, title, and (for Custom variant) URL are mandatory; Apply is blocked with inline errors otherwise.
+- **Project page**: fields are optional; blank values and `Default` variant inherit from Override Defaults. Non-blank values must be valid; effective (resolved) values must satisfy the Custom requirements, otherwise Apply is blocked.
+- **Application ID validation (strict)**: digits only, 17-20 characters, must fit into `Long` (Discord snowflake).
+- **Custom icon URL validation**: absolute HTTP(S) URL with a host; credentials and fragments rejected; query parameters allowed.
+- **Runtime**: resolved Application ID drives the Discord SDK connection (project reinit on change); resolved title is the large-image tooltip (`largeImageText`); resolved variant/URL is used for the large icon and for the small icon in File mode.
+- **Apply in Override Defaults re-renders all open non-default projects** so a new Application ID reconnects immediately.
+- Invalid values persisted manually in XML never break rendering: fall back to the current IDE's Application ID/title and the standard New icon.
+
+### Scope
+- Only the existing bundles are updated (`ConfigBundle.properties` and `ConfigBundle_en.properties`).
+- Out of scope: checking that the Application ID exists on Discord, managing app assets on the portal, README/docs updates, new locales.
+
+# Technical Design
+
+### Existing Pattern
+- `IDEIcon` / `IDEIconDefaultable` enums pair an icon with an `IDEType` (app ID + title); `UnitedState` is a fresh merge snapshot of project + app defaults per render; `TimeService.render()` reinits `ActivityRender` when `clientID` changes; the custom-icon-server feature (commit `490acf3`) is the reference for Custom UI + `validationOnApply` + conditional rows.
+- UI: Kotlin UI DSL v2; conditions from `com.intellij.ui.layout` (`visibleIf`, `selectedValueMatches`, combinable with `and`). Persistence: `XmlSerializerUtil.copyBean`, so new fields with defaults are backward/forward compatible.
+
+### Changes and Contracts
+1. **Enums** (`setting/DefaultsState.kt`, `setting/ProjectState.kt`):
+   - `IDEIcon.app: IDEType` -> `IDEType?`; add `Custom("Custom", null)`.
+   - `IDEIconDefaultable`: add `Custom("Custom", null)`.
+   - These same enums are reused for the icon variant selector (project variant additionally has `Default` = inherit).
+2. **State fields** (defaults keep old behavior):
+   - `DefaultsState`: `customApplicationId = ""`, `customApplicationTitle = ""`, `customIconVariant: IDEIcon = IDEIcon.New`, `customIconUrl = ""`.
+   - `ProjectState`: same strings; `customIconVariant: IDEIconDefaultable = IDEIconDefaultable.Default`.
+3. **Validation helpers** (top-level `internal` in `DefaultsState.kt`, next to `normalizeUrl`):
+   - `parseApplicationId(String): Long?` / `isValidApplicationId(String): Boolean` - trim, `^\d{17,20}$`, `toLongOrNull()`.
+   - `normalizeIconUrl(String): String?` - trim; absolute HTTP(S), host required, no userinfo/fragment; **query allowed**. `normalizeUrl` (server) stays unchanged.
+4. **`UnitedState`** - replace `ideIcon: IDEIcon` with resolved fields: `applicationId: Long`, `applicationTitle: String`, `iconVariant: IDEIcon`, `customIconUrl: String?`:
+   - Not Custom -> ID/title from `icon.app` (fallback `currentIDEType`), variant = icon, URL = null.
+   - Custom -> project value `ifBlank` -> default value; variant `Default` -> defaults' variant; URL only when effective variant = Custom; invalid/missing values fall back to `currentIDEType` ID/title and New icon.
+   - `resolveIDEIcon` exhaustive `when` gains `Custom`.
+5. **`TimeService`**:
+   - `buildIDEIconUrl(iconVariant, customIconUrl, theme, iconsUrl)`; `IDEIcon.Custom` -> custom URL (New URL as a safety fallback).
+   - `applyIDEInfo`/`applyFileInfo` accept `UnitedState` (title = `applicationTitle`); all four call sites updated.
+   - Reinit check uses `configState.applicationId`; `ActivityRender` keeps its default `clientID = currentIDEType.applicationId` and switches on first render.
+6. **UI**:
+   - `DefaultsConfigurable`: rows after IDE icon, `visibleIf(ideIcon == Custom)` - Application ID (validationOnApply), link row (`BrowserUtil.browse`), Application title (validationOnApply non-blank), Icon variant combo; URL row visibility = combined condition (`selectedValueMatches` on both combos joined with `and`), validationOnApply only when effective variant Custom. `apply()` additionally renders open non-default projects via `ProjectManager`.
+   - `ProjectConfigurable`: same rows using `IDEIconDefaultable`; `emptyText = leaveBlankDefaultValue` on text fields; validation resolves effective values from `CatActivitySettingAppState` (project `ifBlank` -> defaults); variant `Default` inherits.
+7. **Bundles** (both files): `customApplicationId`, `customApplicationTitle`, `customIconVariant`, `customIconUrl`, `createApplicationLink`, `invalidApplicationId`, `emptyApplicationTitle`, `invalidCustomIconUrl`, plus a short tooltip help for title.
+
+### File Structure
+- Modify: `src/main/kotlin/cat/wavy/catactivity/setting/{DefaultsState,ProjectState,UnitedState,DefaultsConfigurable,ProjectConfigurable}.kt`, `service/TimeService.kt`, `src/main/resources/messages/ConfigBundle.properties`, `ConfigBundle_en.properties`.
+- Add: `src/test/kotlin/cat/wavy/catactivity/setting/CustomApplicationValidationTest.kt`.
+- Unchanged: `render/ActivityRender.kt` (only its default clientID is used as a fallback), `CatSettingState.kt`, `types/IDEType.kt`, `plugin.xml`.
+
+### Settings Flow
+```mermaid
+graph LR
+    UI[Configurables] --> States[DefaultsState / ProjectState]
+    States --> United[UnitedState resolution]
+    United --> Time[TimeService: URL, title, clientID]
+    Time --> Render[ActivityRender reinit / updateActivity]
+```
+
+# Testing
+
+### Automated Checks
+- Plain JUnit 4 tests (no platform deps) for the pure helpers: snowflake acceptance (17-20 digits) and rejection (blank, non-digit, too short/long, Long overflow); `normalizeIconUrl` acceptance (HTTP/HTTPS, port, base path, query) and rejection (relative, ftp, userinfo, fragment, blank); `normalizeUrl` regression unchanged. `UnitedState`/`IDEIcon` tests are intentionally not added - enum init touches `currentIDEType`, which requires the platform runtime.
+- `.\gradlew.bat check` (compile + tests) and `.\gradlew.bat verifyPlugin`.
+- Sandbox smoke test via `.\gradlew.bat runIde`: open both settings pages, exercise validation, Apply re-render, inheritance, and File-mode icon swap.
+
+# Delivery Steps
+
+### Step 1: Settings model and validators
+Enums and both state classes support custom app values; validation helpers exist and are unit-tested.
+- Extend `IDEIcon`/`IDEIconDefaultable`; add state fields; add `parseApplicationId`/`isValidApplicationId`/`normalizeIconUrl`; add `CustomApplicationValidationTest`.
+
+### Step 2: Resolution and runtime wiring
+Custom values reach Discord: app ID/title/icon are resolved and applied per render.
+- Extend `UnitedState` resolution (inheritance + fallbacks); rework `buildIDEIconUrl`, `applyIDEInfo`, `applyFileInfo`, and the `clientID` reinit check in `TimeService`.
+
+### Step 3: Override Defaults UI
+Custom controls with validation and an immediate effect.
+- Add conditional rows + link + validation to `DefaultsConfigurable`; re-render open projects on apply; add bundle keys to both files.
+
+### Step 4: Project settings UI
+Overrides with blank/`Default` inheritance.
+- Add the same rows to `ProjectConfigurable` using `IDEIconDefaultable`, `leaveBlankDefaultValue`, and effective-value validation.
+
+### Step 5: Verification
+Build, tests, and manual smoke checks pass; bundle keys resolve.
+- Run `.\gradlew.bat check` and `.\gradlew.bat verifyPlugin`; smoke-test in `runIde`.
diff --git a/src/main/kotlin/cat/wavy/catactivity/service/TimeService.kt b/src/main/kotlin/cat/wavy/catactivity/service/TimeService.kt
index 8a0cd5d..e78a3df 100644
--- a/src/main/kotlin/cat/wavy/catactivity/service/TimeService.kt
+++ b/src/main/kotlin/cat/wavy/catactivity/service/TimeService.kt
@@ -148,8 +148,8 @@ class TimeService : Disposable {
                                 state = configState.idleStateFormat.replaceVariables(variables),
                                 details = configState.idleDetailFormat.ifBlank { null }?.replaceVariables(variables),
                                 startTimestamp = startIdleTimestamp
-                            ).applyIDEInfo(configState.ideIcon, configState.theme, configState.iconsUrl)
-                                .applyFileInfo(configState.ideIcon, configState.theme, configState.iconsUrl)
+                            ).applyIDEInfo(configState)
+                                .applyFileInfo(configState)
 
                             activityWrapper.let {
                                 activityRender.updateActivity(it)
@@ -179,8 +179,8 @@ class TimeService : Disposable {
                             state = configState.fileStateFormat.replaceVariables(variables),
                             details = configState.fileDetailFormat.ifBlank { null }?.replaceVariables(variables),
                             startTimestamp = editingFile?.key?.let { timeTracker.getIfPresent(it) },
-                        ).applyIDEInfo(configState.ideIcon, configState.theme, configState.iconsUrl)
-                            .applyFileInfo(configState.ideIcon, configState.theme, configState.iconsUrl)
+                        ).applyIDEInfo(configState)
+                            .applyFileInfo(configState)
 
                         if (configState.showRepositoryButton && !gitRemotes.isNullOrEmpty()) {
                             activityWrapper.applyRepoButton(gitRemotes[0])
@@ -192,7 +192,7 @@ class TimeService : Disposable {
                             state = configState.projectStateFormat.replaceVariables(variables),
                             details = configState.projectDetailFormat.ifBlank { null }?.replaceVariables(variables),
                             startTimestamp = editingProject?.key?.let { timeTracker.getIfPresent(it) },
-                        ).applyIDEInfo(configState.ideIcon, configState.theme, configState.iconsUrl)
+                        ).applyIDEInfo(configState)
 
                         if (configState.showRepositoryButton && !gitRemotes.isNullOrEmpty()) {
                             activityWrapper.applyRepoButton(gitRemotes[0])
@@ -203,14 +203,14 @@ class TimeService : Disposable {
                         activityWrapper = ActivityWrapper(
                             state = ApplicationInfoEx.getInstanceEx().fullApplicationName,
                             startTimestamp = startTime,
-                        ).applyIDEInfo(configState.ideIcon, configState.theme, configState.iconsUrl)
+                        ).applyIDEInfo(configState)
                     }
                 }
 
                 thisLogger().info("Rendering file: ${activityWrapper.details}")
 
-                if (activityRender.clientID != configState.ideIcon.app.applicationId) activityRender.apply {
-                    clientID = configState.ideIcon.app.applicationId
+                if (activityRender.clientID != configState.applicationId) activityRender.apply {
+                    clientID = configState.applicationId
                     project.service<ActivityNotificationService>().ignoreReloadAlert.set(false)
                     reinit(false)
                 }
@@ -261,18 +261,18 @@ class TimeService : Disposable {
         return this
     }
 
-    private fun ActivityWrapper.applyIDEInfo(ideIcon: IDEIcon, theme: Theme, iconsUrl: String): ActivityWrapper {
-        largeImageKey = buildIDEIconUrl(ideIcon, theme, iconsUrl)
-        largeImageText = ideIcon.app.title
+    private fun ActivityWrapper.applyIDEInfo(configState: UnitedState): ActivityWrapper {
+        largeImageKey = buildIDEIconUrl(configState.iconVariant, configState.customIconUrl, configState.theme, configState.iconsUrl)
+        largeImageText = configState.applicationTitle
         return this
     }
 
-    private fun ActivityWrapper.applyFileInfo(ideIcon: IDEIcon, theme: Theme, iconsUrl: String): ActivityWrapper {
+    private fun ActivityWrapper.applyFileInfo(configState: UnitedState): ActivityWrapper {
         editingFile?.let {
             val type = getFileTypeByName(it.type, it.fileName, it.extension)
-            smallImageKey = buildIDEIconUrl(ideIcon, theme, iconsUrl)
+            smallImageKey = buildIDEIconUrl(configState.iconVariant, configState.customIconUrl, configState.theme, configState.iconsUrl)
             smallImageText = largeImageText // swap
-            largeImageKey = buildLangIconUrl(type.icon, theme, iconsUrl)
+            largeImageKey = buildLangIconUrl(type.icon, configState.theme, configState.iconsUrl)
             largeImageText = type.typeName
         }
         return this
@@ -284,11 +284,12 @@ class TimeService : Disposable {
 internal fun buildLangIconUrl(icon: String, theme: Theme, iconsUrl: String): String =
     "$iconsUrl/${theme.name}/$icon.webp"
 
-internal fun buildIDEIconUrl(ideIcon: IDEIcon, theme: Theme, iconsUrl: String): String = when (ideIcon) {
+internal fun buildIDEIconUrl(iconVariant: IDEIcon, customIconUrl: String?, theme: Theme, iconsUrl: String): String = when (iconVariant) {
     IDEIcon.New -> "$iconsUrl/IDE/new/${theme.name}/${currentIDEType.icon}.webp"
     IDEIcon.Old -> "$iconsUrl/IDE/${theme.name}/${currentIDEType.icon}.webp"
     IDEIcon.JetBrains -> "$iconsUrl/IDE/${theme.name}/jetbrains.webp"
     IDEIcon.CatActivity -> "$iconsUrl/IDE/${theme.name}/cat_activity.webp"
+    IDEIcon.Custom -> customIconUrl ?: "$iconsUrl/IDE/${theme.name}/cat_activity.webp"
 }
 
 sealed class TimedItem(
diff --git a/src/main/kotlin/cat/wavy/catactivity/setting/DefaultsConfigurable.kt b/src/main/kotlin/cat/wavy/catactivity/setting/DefaultsConfigurable.kt
index 83d8f86..ec210fd 100644
--- a/src/main/kotlin/cat/wavy/catactivity/setting/DefaultsConfigurable.kt
+++ b/src/main/kotlin/cat/wavy/catactivity/setting/DefaultsConfigurable.kt
@@ -1,13 +1,16 @@
 package cat.wavy.catactivity.setting
 
 import cat.wavy.catactivity.bundle.ConfigBundle
+import cat.wavy.catactivity.service.TimeService
 import com.intellij.ide.BrowserUtil
 import com.intellij.openapi.components.service
 import com.intellij.openapi.options.Configurable
+import com.intellij.openapi.project.ProjectManager
 import com.intellij.openapi.ui.ComboBox
 import com.intellij.ui.JBColor
 import com.intellij.ui.components.JBTextField
 import com.intellij.ui.dsl.builder.*
+import com.intellij.ui.layout.and
 import com.intellij.ui.layout.enteredTextSatisfies
 import com.intellij.ui.layout.selectedValueMatches
 import com.intellij.ui.dsl.listCellRenderer.textListCellRenderer
@@ -17,6 +20,8 @@ class DefaultsConfigurable : Configurable {
     private val panel = panel {
         val state = service<CatActivitySettingAppState>().state
         var customServerSelector: ComboBox<Boolean>? = null
+        var ideIconSelector: ComboBox<IDEIcon>? = null
+        var iconVariantSelector: ComboBox<IDEIcon>? = null
 
         group(ConfigBundle.message("display")) {
             row(ConfigBundle.message("theme")) {
@@ -26,11 +31,65 @@ class DefaultsConfigurable : Configurable {
             row(ConfigBundle.message("ideIcons")) {
                 comboBox(items = IDEIcon.entries)
                     .applyToComponent {
+                        ideIconSelector = this
                         renderer = textListCellRenderer("") { it.displayName }
                     }
                     .bindItem(state::ideIcon.toNullableProperty())
             }
 
+            val isCustomApplication = ideIconSelector!!.selectedValueMatches { it == IDEIcon.Custom }
+
+            row(ConfigBundle.message("customApplicationId")) {
+                textField().columns(COLUMNS_LARGE)
+                    .bindText(state::customApplicationId)
+                    .validationOnApply {
+                        if (state.ideIcon == IDEIcon.Custom && !isValidApplicationId(state.customApplicationId)) {
+                            error(ConfigBundle.message("invalidApplicationId"))
+                        } else null
+                    }
+
+                contextHelp(ConfigBundle.message("customApplicationHelp"))
+            }.visibleIf(isCustomApplication)
+
+            row {
+                link(ConfigBundle.message("createApplicationLink")) {
+                    BrowserUtil.browse("https://discord.com/developers/applications")
+                }
+            }.visibleIf(isCustomApplication)
+
+            row(ConfigBundle.message("customApplicationTitle")) {
+                textField().columns(COLUMNS_LARGE)
+                    .bindText(state::customApplicationTitle)
+                    .validationOnApply {
+                        if (state.ideIcon == IDEIcon.Custom && state.customApplicationTitle.isBlank()) {
+                            error(ConfigBundle.message("emptyApplicationTitle"))
+                        } else null
+                    }
+
+                contextHelp(ConfigBundle.message("customApplicationTitleHelp"))
+            }.visibleIf(isCustomApplication)
+
+            row(ConfigBundle.message("customIconVariant")) {
+                comboBox(items = IDEIcon.entries)
+                    .applyToComponent {
+                        iconVariantSelector = this
+                        renderer = textListCellRenderer("") { it.displayName }
+                    }
+                    .bindItem(state::customIconVariant.toNullableProperty())
+            }.visibleIf(isCustomApplication)
+
+            row(ConfigBundle.message("customIconUrl")) {
+                textField().columns(COLUMNS_LARGE)
+                    .bindText(state::customIconUrl)
+                    .validationOnApply {
+                        if (state.ideIcon == IDEIcon.Custom && state.customIconVariant == IDEIcon.Custom &&
+                            normalizeIconUrl(state.customIconUrl) == null
+                        ) {
+                            error(ConfigBundle.message("invalidCustomIconUrl"))
+                        } else null
+                    }
+            }.visibleIf(isCustomApplication and iconVariantSelector!!.selectedValueMatches { it == IDEIcon.Custom })
+
             row(ConfigBundle.message("iconsServer")) {
                 comboBox(items = listOf(false, true))
                     .applyToComponent {
@@ -151,7 +210,11 @@ class DefaultsConfigurable : Configurable {
 
     override fun isModified(): Boolean = panel.isModified()
 
-    override fun apply() = panel.apply()
+    override fun apply() = panel.apply().also {
+        ProjectManager.getInstance().openProjects
+            .filter { !it.isDefault }
+            .forEach { project -> project.service<TimeService>().render(project) }
+    }
 
     override fun reset() = panel.reset()
 
diff --git a/src/main/kotlin/cat/wavy/catactivity/setting/DefaultsState.kt b/src/main/kotlin/cat/wavy/catactivity/setting/DefaultsState.kt
index e877008..d80d9ea 100644
--- a/src/main/kotlin/cat/wavy/catactivity/setting/DefaultsState.kt
+++ b/src/main/kotlin/cat/wavy/catactivity/setting/DefaultsState.kt
@@ -8,6 +8,10 @@ import java.net.URI
 data class DefaultsState(
     var theme: Theme = Theme.Macchiato,
     var ideIcon: IDEIcon = IDEIcon.New,
+    var customApplicationId: String = "",
+    var customApplicationTitle: String = "",
+    var customIconVariant: IDEIcon = IDEIcon.New,
+    var customIconUrl: String = "",
     var useCustomIconsServer: Boolean = false,
     var customIconsUrl: String = "",
 
@@ -38,6 +42,28 @@ internal fun normalizeUrl(value: String): String? {
     }.getOrNull()
 }
 
+internal fun parseApplicationId(value: String): Long? {
+    val trimmed = value.trim()
+    if (!trimmed.matches(Regex("^\\d{17,20}$"))) return null
+    return trimmed.toLongOrNull()
+}
+
+internal fun isValidApplicationId(value: String): Boolean = parseApplicationId(value) != null
+
+internal fun normalizeIconUrl(value: String): String? {
+    val trimmed = value.trim()
+    if (trimmed.isEmpty()) return null
+
+    return runCatching {
+        val uri = URI(trimmed)
+        if (!uri.isAbsolute || uri.host.isNullOrBlank() || uri.rawUserInfo != null ||
+            uri.rawFragment != null ||
+            !uri.scheme.equals("http", ignoreCase = true) && !uri.scheme.equals("https", ignoreCase = true)
+        ) return null
+        uri.toASCIIString()
+    }.getOrNull()
+}
+
 enum class Theme {
     Frappe,
     Latte,
@@ -45,10 +71,10 @@ enum class Theme {
     Mocha,
 }
 
-enum class IDEIcon(val displayName: String, val app: IDEType) {
+enum class IDEIcon(val displayName: String, val app: IDEType?) {
     New("${currentIDEType.title} (New)", currentIDEType),
     Old("${currentIDEType.title} (Old)", currentIDEType),
     JetBrains("JetBrains", IDEType.JETBRAINS),
     CatActivity("Cat Activity", IDEType.CATACTIVITY),
+    Custom("Custom", null),
 }
-
diff --git a/src/main/kotlin/cat/wavy/catactivity/setting/ProjectConfigurable.kt b/src/main/kotlin/cat/wavy/catactivity/setting/ProjectConfigurable.kt
index 82647b6..393c81d 100644
--- a/src/main/kotlin/cat/wavy/catactivity/setting/ProjectConfigurable.kt
+++ b/src/main/kotlin/cat/wavy/catactivity/setting/ProjectConfigurable.kt
@@ -1,6 +1,7 @@
 package cat.wavy.catactivity.setting
 
 import cat.wavy.catactivity.bundle.ConfigBundle
+import com.intellij.ide.BrowserUtil
 import com.intellij.openapi.components.service
 import com.intellij.openapi.options.Configurable
 import com.intellij.openapi.project.Project
@@ -9,6 +10,7 @@ import cat.wavy.catactivity.service.TimeService
 import com.intellij.openapi.ui.ComboBox
 import com.intellij.ui.components.JBCheckBox
 import com.intellij.ui.dsl.listCellRenderer.textListCellRenderer
+import com.intellij.ui.layout.and
 import com.intellij.ui.layout.selected
 import com.intellij.ui.layout.selectedValueIs
 import com.intellij.ui.layout.selectedValueMatches
@@ -19,9 +21,12 @@ class ProjectConfigurable(
 ) : Configurable {
     private val panel = panel {
         val state = project.service<CatActivitySettingProjectState>().state
+        val defaults = service<CatActivitySettingAppState>().state
 
         var enableCheck: JBCheckBox? = null
         var displayCombo: ComboBox<Details>? = null
+        var ideIconSelector: ComboBox<IDEIconDefaultable>? = null
+        var iconVariantSelector: ComboBox<IDEIconDefaultable>? = null
 
         row {
             checkBox(ConfigBundle.message("enablePlugin")).bindSelected(state::isEnabled)
@@ -53,10 +58,71 @@ class ProjectConfigurable(
             row(ConfigBundle.message("ideIcons")) {
                 comboBox(items = IDEIconDefaultable.entries)
                     .applyToComponent {
+                        ideIconSelector = this
                         renderer = textListCellRenderer("") { it.displayName }
                     }
                     .bindItem(state::ideIcon.toNullableProperty())
             }
+
+            val isCustomApplication = ideIconSelector!!.selectedValueMatches { it == IDEIconDefaultable.Custom }
+
+            row(ConfigBundle.message("customApplicationId")) {
+                textField().columns(COLUMNS_LARGE)
+                    .bindText(state::customApplicationId)
+                    .applyToComponent { emptyText.text = ConfigBundle.message("leaveBlankDefaultValue") }
+                    .validationOnApply {
+                        val effectiveId = state.customApplicationId.ifBlank { defaults.customApplicationId }
+                        if (state.ideIcon == IDEIconDefaultable.Custom && !isValidApplicationId(effectiveId)) {
+                            error(ConfigBundle.message("invalidApplicationId"))
+                        } else null
+                    }
+
+                contextHelp(ConfigBundle.message("customApplicationHelp"))
+            }.visibleIf(isCustomApplication)
+
+            row {
+                link(ConfigBundle.message("createApplicationLink")) {
+                    BrowserUtil.browse("https://discord.com/developers/applications")
+                }
+            }.visibleIf(isCustomApplication)
+
+            row(ConfigBundle.message("customApplicationTitle")) {
+                textField().columns(COLUMNS_LARGE)
+                    .bindText(state::customApplicationTitle)
+                    .applyToComponent { emptyText.text = ConfigBundle.message("leaveBlankDefaultValue") }
+                    .validationOnApply {
+                        val effectiveTitle = state.customApplicationTitle.ifBlank { defaults.customApplicationTitle }
+                        if (state.ideIcon == IDEIconDefaultable.Custom && effectiveTitle.isBlank()) {
+                            error(ConfigBundle.message("emptyApplicationTitle"))
+                        } else null
+                    }
+
+                contextHelp(ConfigBundle.message("customApplicationTitleHelp"))
+            }.visibleIf(isCustomApplication)
+
+            row(ConfigBundle.message("customIconVariant")) {
+                comboBox(items = IDEIconDefaultable.entries)
+                    .applyToComponent {
+                        iconVariantSelector = this
+                        renderer = textListCellRenderer("") { it.displayName }
+                    }
+                    .bindItem(state::customIconVariant.toNullableProperty())
+            }.visibleIf(isCustomApplication)
+
+            row(ConfigBundle.message("customIconUrl")) {
+                textField().columns(COLUMNS_LARGE)
+                    .bindText(state::customIconUrl)
+                    .applyToComponent { emptyText.text = ConfigBundle.message("leaveBlankDefaultValue") }
+                    .validationOnApply {
+                        val effectiveVariant = UnitedState.resolveIconVariant(state.customIconVariant, defaults.customIconVariant)
+                        val effectiveUrl = state.customIconUrl.ifBlank { defaults.customIconUrl }
+                        if (state.ideIcon == IDEIconDefaultable.Custom && effectiveVariant == IDEIcon.Custom &&
+                            normalizeIconUrl(effectiveUrl) == null
+                        ) {
+                            error(ConfigBundle.message("invalidCustomIconUrl"))
+                        } else null
+                    }
+            }.visibleIf(isCustomApplication and iconVariantSelector!!.selectedValueMatches { it == IDEIconDefaultable.Custom })
         }.enabledIf(enableCheck.selected)
 
         group(ConfigBundle.message("formatProject")) {
@@ -133,4 +199,4 @@ class ProjectConfigurable(
     override fun reset() = panel.reset()
 
     override fun getDisplayName(): String = ConfigBundle.message("projectTitle")
-}
\ No newline at end of file
+}
diff --git a/src/main/kotlin/cat/wavy/catactivity/setting/ProjectState.kt b/src/main/kotlin/cat/wavy/catactivity/setting/ProjectState.kt
index d240774..52411ec 100644
--- a/src/main/kotlin/cat/wavy/catactivity/setting/ProjectState.kt
+++ b/src/main/kotlin/cat/wavy/catactivity/setting/ProjectState.kt
@@ -8,6 +8,10 @@ data class ProjectState(
     var details: Details = Details.IDE,
     var theme: ThemeDefaultable = ThemeDefaultable.Default,
     var ideIcon: IDEIconDefaultable = IDEIconDefaultable.Default,
+    var customApplicationId: String = "",
+    var customApplicationTitle: String = "",
+    var customIconVariant: IDEIconDefaultable = IDEIconDefaultable.Default,
+    var customIconUrl: String = "",
     var showRepositoryButton: Boolean = false,
 
     var projectStateFormat: String = "",
@@ -42,4 +46,5 @@ enum class IDEIconDefaultable(val displayName: String, val app: IDEType?) {
     Old("${currentIDEType.title} (Old)", currentIDEType),
     JetBrains("JetBrains", IDEType.JETBRAINS),
     CatActivity("Cat Activity", IDEType.CATACTIVITY),
+    Custom("Custom", null),
 }
diff --git a/src/main/kotlin/cat/wavy/catactivity/setting/UnitedState.kt b/src/main/kotlin/cat/wavy/catactivity/setting/UnitedState.kt
index 9450673..c235269 100644
--- a/src/main/kotlin/cat/wavy/catactivity/setting/UnitedState.kt
+++ b/src/main/kotlin/cat/wavy/catactivity/setting/UnitedState.kt
@@ -1,10 +1,15 @@
 package cat.wavy.catactivity.setting
 
+import cat.wavy.catactivity.types.currentIDEType
+
 data class UnitedState(
     var isEnabled: Boolean,
     var details: Details,
     var theme: Theme,
-    var ideIcon: IDEIcon,
+    var applicationId: Long,
+    var applicationTitle: String,
+    var iconVariant: IDEIcon,
+    var customIconUrl: String?,
     var iconsUrl: String,
     var showRepositoryButton: Boolean,
 
@@ -23,7 +28,10 @@ data class UnitedState(
         isEnabled = projectState.isEnabled,
         details = projectState.details,
         theme = resolveTheme(projectState.theme, defaultsState.theme),
-        ideIcon = resolveIDEIcon(projectState.ideIcon, defaultsState.ideIcon),
+        applicationId = resolveApplicationId(projectState, defaultsState),
+        applicationTitle = resolveApplicationTitle(projectState, defaultsState),
+        iconVariant = resolveIconVariant(projectState, defaultsState),
+        customIconUrl = resolveCustomIconUrl(projectState, defaultsState),
         iconsUrl = defaultsState.iconsUrl,
         showRepositoryButton = projectState.showRepositoryButton,
         projectStateFormat = projectState.projectStateFormat.ifBlank { defaultsState.projectStateFormat },
@@ -46,14 +54,66 @@ data class UnitedState(
             }
         }
 
-        private fun resolveIDEIcon(settingIcon: IDEIconDefaultable, defaultIcon: IDEIcon): IDEIcon {
+        internal fun resolveIDEIcon(settingIcon: IDEIconDefaultable, defaultIcon: IDEIcon): IDEIcon {
             return when (settingIcon) {
                 IDEIconDefaultable.Default -> defaultIcon
                 IDEIconDefaultable.New -> IDEIcon.New
                 IDEIconDefaultable.Old -> IDEIcon.Old
                 IDEIconDefaultable.JetBrains -> IDEIcon.JetBrains
                 IDEIconDefaultable.CatActivity -> IDEIcon.CatActivity
+                IDEIconDefaultable.Custom -> IDEIcon.Custom
+            }
+        }
+
+        internal fun resolveIconVariant(settingVariant: IDEIconDefaultable, defaultVariant: IDEIcon): IDEIcon {
+            return when (settingVariant) {
+                IDEIconDefaultable.Default -> defaultVariant
+                IDEIconDefaultable.New -> IDEIcon.New
+                IDEIconDefaultable.Old -> IDEIcon.Old
+                IDEIconDefaultable.JetBrains -> IDEIcon.JetBrains
+                IDEIconDefaultable.CatActivity -> IDEIcon.CatActivity
+                IDEIconDefaultable.Custom -> IDEIcon.Custom
+            }
+        }
+
+        internal fun resolveApplicationId(projectState: ProjectState, defaultsState: DefaultsState): Long {
+            val ideIcon = resolveIDEIcon(projectState.ideIcon, defaultsState.ideIcon)
+            if (ideIcon != IDEIcon.Custom) {
+                return ideIcon.app?.applicationId ?: currentIDEType.applicationId
             }
+            val raw = projectState.customApplicationId.ifBlank { defaultsState.customApplicationId }
+            return parseApplicationId(raw) ?: currentIDEType.applicationId
+        }
+
+        internal fun resolveApplicationTitle(projectState: ProjectState, defaultsState: DefaultsState): String {
+            val ideIcon = resolveIDEIcon(projectState.ideIcon, defaultsState.ideIcon)
+            if (ideIcon != IDEIcon.Custom) {
+                return ideIcon.app?.title ?: currentIDEType.title
+            }
+            return projectState.customApplicationTitle.ifBlank { defaultsState.customApplicationTitle }
+                .ifBlank { currentIDEType.title }
+        }
+
+        internal fun resolveIconVariant(projectState: ProjectState, defaultsState: DefaultsState): IDEIcon {
+            val ideIcon = resolveIDEIcon(projectState.ideIcon, defaultsState.ideIcon)
+            if (ideIcon != IDEIcon.Custom) return ideIcon
+
+            val variant = resolveIconVariant(projectState.customIconVariant, defaultsState.customIconVariant)
+            if (variant == IDEIcon.Custom && resolveCustomIconUrl(projectState, defaultsState) == null) {
+                return IDEIcon.New
+            }
+            return variant
+        }
+
+        internal fun resolveCustomIconUrl(projectState: ProjectState, defaultsState: DefaultsState): String? {
+            val ideIcon = resolveIDEIcon(projectState.ideIcon, defaultsState.ideIcon)
+            if (ideIcon != IDEIcon.Custom) return null
+
+            val variant = resolveIconVariant(projectState.customIconVariant, defaultsState.customIconVariant)
+            if (variant != IDEIcon.Custom) return null
+
+            val raw = projectState.customIconUrl.ifBlank { defaultsState.customIconUrl }
+            return normalizeIconUrl(raw)
         }
     }
 }
diff --git a/src/main/resources/messages/ConfigBundle.properties b/src/main/resources/messages/ConfigBundle.properties
index 4cc8254..9e28549 100644
--- a/src/main/resources/messages/ConfigBundle.properties
+++ b/src/main/resources/messages/ConfigBundle.properties
@@ -11,7 +11,17 @@ detailsModeHelp=<ul>\
     <li><b>File</b>: display project and file information</li>\
 </ul>
 enablePlugin=Enable Rich Presence
-ideIcons=IDE icon
+ideIcons=App Icon
+customApplicationId=Application ID
+customApplicationHelp=The Discord application used for the presence. You can create your own application in the Discord Developer Portal.
+createApplicationLink=Create an application in the Discord Developer Portal
+customApplicationTitle=Application title
+customApplicationTitleHelp=Shown as the tooltip of the large icon.
+customIconVariant=Icon variant
+customIconUrl=Custom icon URL
+invalidApplicationId=Enter a numeric Discord Application ID (17-20 digits).
+emptyApplicationTitle=Application title can't be empty
+invalidCustomIconUrl=Enter an absolute HTTP(S) URL with a host and no credentials or fragment.
 iconsServer=Icon server
 defaultServer=Default server
 customServer=Custom server
diff --git a/src/main/resources/messages/ConfigBundle_en.properties b/src/main/resources/messages/ConfigBundle_en.properties
index 4cc8254..9e28549 100644
--- a/src/main/resources/messages/ConfigBundle_en.properties
+++ b/src/main/resources/messages/ConfigBundle_en.properties
@@ -11,7 +11,17 @@ detailsModeHelp=<ul>\
     <li><b>File</b>: display project and file information</li>\
 </ul>
 enablePlugin=Enable Rich Presence
-ideIcons=IDE icon
+ideIcons=App Icon
+customApplicationId=Application ID
+customApplicationHelp=The Discord application used for the presence. You can create your own application in the Discord Developer Portal.
+createApplicationLink=Create an application in the Discord Developer Portal
+customApplicationTitle=Application title
+customApplicationTitleHelp=Shown as the tooltip of the large icon.
+customIconVariant=Icon variant
+customIconUrl=Custom icon URL
+invalidApplicationId=Enter a numeric Discord Application ID (17-20 digits).
+emptyApplicationTitle=Application title can't be empty
+invalidCustomIconUrl=Enter an absolute HTTP(S) URL with a host and no credentials or fragment.
 iconsServer=Icon server
 defaultServer=Default server
 customServer=Custom server
diff --git a/src/test/kotlin/cat/wavy/catactivity/setting/CustomApplicationValidationTest.kt b/src/test/kotlin/cat/wavy/catactivity/setting/CustomApplicationValidationTest.kt
new file mode 100644
index 0000000..ed7b2bf
--- /dev/null
+++ b/src/test/kotlin/cat/wavy/catactivity/setting/CustomApplicationValidationTest.kt
@@ -0,0 +1,60 @@
+package cat.wavy.catactivity.setting
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class CustomApplicationValidationTest {
+    @Test
+    fun `application id accepts valid snowflake`() {
+        assertEquals(1226060730273497098L, parseApplicationId("1226060730273497098"))
+        assertTrue(isValidApplicationId("1226060730273497098"))
+    }
+
+    @Test
+    fun `application id is trimmed`() {
+        assertTrue(isValidApplicationId("  1226060730273497098  "))
+    }
+
+    @Test
+    fun `application id rejects invalid values`() {
+        assertFalse(isValidApplicationId(""))
+        assertFalse(isValidApplicationId("   "))
+        assertFalse(isValidApplicationId("1226060730273497"))
+        assertFalse(isValidApplicationId("123456789012345678901"))
+        assertFalse(isValidApplicationId("12260607302734970a"))
+        assertFalse(isValidApplicationId("1226060730273497098L"))
+        assertFalse(isValidApplicationId("99999999999999999999"))
+    }
+
+    @Test
+    fun `icon url accepts http https and query`() {
+        assertEquals("https://cdn.example.com/icon.webp", normalizeIconUrl("https://cdn.example.com/icon.webp"))
+        assertEquals("http://example.com/a/b.webp", normalizeIconUrl("http://example.com/a/b.webp"))
+        assertEquals(
+            "https://cdn.example.com/icon.webp?token=abc",
+            normalizeIconUrl("https://cdn.example.com/icon.webp?token=abc")
+        )
+        assertEquals("https://example.com:8443/icon.webp", normalizeIconUrl("https://example.com:8443/icon.webp"))
+    }
+
+    @Test
+    fun `icon url rejects invalid values`() {
+        assertNull(normalizeIconUrl(""))
+        assertNull(normalizeIconUrl("   "))
+        assertNull(normalizeIconUrl("/icon.webp"))
+        assertNull(normalizeIconUrl("ftp://example.com/icon.webp"))
+        assertNull(normalizeIconUrl("https://user:pass@example.com/icon.webp"))
+        assertNull(normalizeIconUrl("https://example.com/icon.webp#frag"))
+        assertNull(normalizeIconUrl("https:///icon.webp"))
+    }
+
+    @Test
+    fun `server url still rejects query and fragment`() {
+        assertEquals("https://example.com/base", normalizeUrl("https://example.com/base/"))
+        assertNull(normalizeUrl("https://example.com/base?x=1"))
+        assertNull(normalizeUrl("https://example.com/base#frag"))
+    }
+}