feat(ai): support for server-side compaction

CHANGELOG.md

@@ -4,6 +4,10 @@
 
 - [Previous Changelogs](https://github.com/eclipse-theia/theia/tree/master/doc/changelogs/)
 
+## 1.74.0 - tbd
+
+- [ai-anthropic, ai-chat, ai-chat-ui, ai-core, ai-openai] added provider-native server-side compaction for chat sessions, modeled as a model capability (`LanguageModelMetaData.serverSideCompactionSupport`) plus layered activation: a global preference (`ai-features.chat.serverSideCompaction`, default on), a per-provider override, and a per-session override (in the session settings dialog) that wins over both. Honored by the Anthropic Messages API (beta) and the OpenAI Responses API; the compaction marker is persisted in the session, replayed on subsequent requests, surfaced as an inline chat marker, and reflected in the token-usage tooltip (cumulative usage and a "compacted Nx" count). Providers/models without the capability ignore it [#17636](https://github.com/eclipse-theia/theia/issues/17636)
+
 ## 1.73.0 - 6/25/2026
 
 - [ai] supported deferred tool loading via provider tool search [#17449](https://github.com/eclipse-theia/theia/pull/17449)

packages/ai-anthropic/src/browser/anthropic-frontend-application-contribution.ts

@@ -17,9 +17,10 @@
 import { FrontendApplicationContribution } from '@theia/core/lib/browser';
 import { inject, injectable } from '@theia/core/shared/inversify';
 import { AnthropicLanguageModelsManager, AnthropicModelDescription } from '../common';
-import { API_KEY_PREF, CUSTOM_ENDPOINTS_PREF, MODELS_PREF } from '../common/anthropic-preferences';
-import { AICorePreferences, PREFERENCE_NAME_MAX_RETRIES } from '@theia/ai-core/lib/common/ai-core-preferences';
+import { API_KEY_PREF, CUSTOM_ENDPOINTS_PREF, MODELS_PREF, SERVER_SIDE_COMPACTION_PREF } from '../common/anthropic-preferences';
+import { AICorePreferences, PREFERENCE_NAME_MAX_RETRIES, PREFERENCE_NAME_SERVER_SIDE_COMPACTION } from '@theia/ai-core/lib/common/ai-core-preferences';
 import { PreferenceService } from '@theia/core';
+import { resolveCompactionDefault, ServerSideCompactionSetting } from '@theia/ai-core';
 
 const ANTHROPIC_PROVIDER_ID = 'anthropic';
 
@@ -63,6 +64,8 @@ export class AnthropicFrontendApplicationContribution implements FrontendApplica
                 } else if (event.preferenceName === 'http.proxy') {
                     this.manager.setProxyUrl(this.preferenceService.get<string>('http.proxy', undefined));
                     this.updateAllModels();
+                } else if (event.preferenceName === SERVER_SIDE_COMPACTION_PREF || event.preferenceName === PREFERENCE_NAME_SERVER_SIDE_COMPACTION) {
+                    this.updateAllModels();
                 } else if (event.preferenceName === CUSTOM_ENDPOINTS_PREF) {
                     this.handleCustomModelChanges(this.preferenceService.get<Partial<AnthropicModelDescription>[]>(CUSTOM_ENDPOINTS_PREF, []));
                 }
@@ -101,6 +104,7 @@ export class AnthropicFrontendApplicationContribution implements FrontendApplica
                 model.apiKey === newModel.apiKey &&
                 model.maxRetries === newModel.maxRetries &&
                 model.useCaching === newModel.useCaching &&
+                model.serverSideCompactionEnabledByDefault === newModel.serverSideCompactionEnabledByDefault &&
                 model.enableStreaming === newModel.enableStreaming));
 
         this.manager.removeLanguageModels(...modelsToRemove.map(model => model.id));
@@ -120,19 +124,26 @@ export class AnthropicFrontendApplicationContribution implements FrontendApplica
     protected createAnthropicModelDescription(modelId: string): AnthropicModelDescription {
         const id = `${ANTHROPIC_PROVIDER_ID}/${modelId}`;
         const maxRetries = this.aiCorePreferences.get(PREFERENCE_NAME_MAX_RETRIES) ?? 3;
+        const globalCompaction = this.preferenceService.get<boolean>(PREFERENCE_NAME_SERVER_SIDE_COMPACTION, true);
+        const compactionOverride = this.preferenceService.get<ServerSideCompactionSetting>(SERVER_SIDE_COMPACTION_PREF, 'default');
+        const serverSideCompactionEnabledByDefault = resolveCompactionDefault(globalCompaction, compactionOverride);
 
         return {
             id: id,
             model: modelId,
             apiKey: true,
             enableStreaming: true,
             useCaching: true,
-            maxRetries: maxRetries
+            maxRetries: maxRetries,
+            serverSideCompactionEnabledByDefault
         };
     }
 
     protected createCustomModelDescriptionsFromPreferences(preferences: Partial<AnthropicModelDescription>[]): AnthropicModelDescription[] {
         const maxRetries = this.aiCorePreferences.get(PREFERENCE_NAME_MAX_RETRIES) ?? 3;
+        const globalCompaction = this.preferenceService.get<boolean>(PREFERENCE_NAME_SERVER_SIDE_COMPACTION, true);
+        const compactionOverride = this.preferenceService.get<ServerSideCompactionSetting>(SERVER_SIDE_COMPACTION_PREF, 'default');
+        const serverSideCompactionEnabledByDefault = resolveCompactionDefault(globalCompaction, compactionOverride);
         return preferences.reduce((acc, pref) => {
             if (!pref.model || !pref.url || typeof pref.model !== 'string' || typeof pref.url !== 'string') {
                 return acc;
@@ -146,7 +157,8 @@ export class AnthropicFrontendApplicationContribution implements FrontendApplica
                     apiKey: typeof pref.apiKey === 'string' || pref.apiKey === true ? pref.apiKey : undefined,
                     enableStreaming: pref.enableStreaming ?? true,
                     useCaching: pref.useCaching ?? true,
-                    maxRetries: pref.maxRetries ?? maxRetries
+                    maxRetries: pref.maxRetries ?? maxRetries,
+                    serverSideCompactionEnabledByDefault
                 }
             ];
         }, []);

packages/ai-anthropic/src/common/anthropic-language-models-manager.ts

@@ -13,6 +13,7 @@
 //
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
 // *****************************************************************************
+
 export const ANTHROPIC_LANGUAGE_MODELS_MANAGER_PATH = '/services/anthropic/language-model-manager';
 export const AnthropicLanguageModelsManager = Symbol('AnthropicLanguageModelsManager');
 
@@ -31,6 +32,8 @@ export interface AnthropicModelDescription {
     useCaching: boolean;
     /** Maximum number of retry attempts when a request fails. Default is 3. */
     maxRetries: number;
+    /** Resolved default enablement of server-side compaction (global preference folded with the per-provider override). Defaults to disabled when omitted. */
+    serverSideCompactionEnabledByDefault?: boolean;
 }
 export interface AnthropicLanguageModelsManager {
     apiKey: string | undefined;

packages/ai-anthropic/src/common/anthropic-preferences.ts

@@ -14,12 +14,13 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
 // *****************************************************************************
 
-import { AI_CORE_PREFERENCES_TITLE } from '@theia/ai-core/lib/common/ai-core-preferences';
+import { AI_CORE_PREFERENCES_TITLE, PREFERENCE_NAME_SERVER_SIDE_COMPACTION } from '@theia/ai-core/lib/common/ai-core-preferences';
 import { LINUX_ENV_HINT, nls, PreferenceSchema } from '@theia/core';
 
 export const API_KEY_PREF = 'ai-features.anthropic.AnthropicApiKey';
 export const MODELS_PREF = 'ai-features.anthropic.AnthropicModels';
 export const CUSTOM_ENDPOINTS_PREF = 'ai-features.anthropicCustom.customAnthropicModels';
+export const SERVER_SIDE_COMPACTION_PREF = 'ai-features.anthropic.serverSideCompaction';
 
 export const AnthropicPreferencesSchema: PreferenceSchema = {
     properties: {
@@ -46,6 +47,22 @@ export const AnthropicPreferencesSchema: PreferenceSchema = {
                 type: 'string'
             }
         },
+        [SERVER_SIDE_COMPACTION_PREF]: {
+            type: 'string',
+            enum: ['default', 'enabled', 'disabled'],
+            enumDescriptions: [
+                nls.localize('theia/ai/anthropic/compaction/default', 'Follow the global chat server-side compaction setting.'),
+                nls.localize('theia/ai/anthropic/compaction/enabled', 'Always request server-side compaction for Anthropic models.'),
+                nls.localize('theia/ai/anthropic/compaction/disabled', 'Never request server-side compaction for Anthropic models.')
+            ],
+            default: 'default',
+            markdownDescription: nls.localize('theia/ai/anthropic/compaction/description',
+                'Override provider-native server-side compaction for Anthropic models. "default" follows the global chat setting ' +
+                '({0}). When effectively enabled, the Anthropic Beta Messages API is used so the provider can summarize ' +
+                'older turns once the conversation grows past its threshold.',
+                `\`#${PREFERENCE_NAME_SERVER_SIDE_COMPACTION}#\``),
+            title: AI_CORE_PREFERENCES_TITLE,
+        },
         [CUSTOM_ENDPOINTS_PREF]: {
             type: 'array',
             title: AI_CORE_PREFERENCES_TITLE,