Add fallback target logging and unified failures

src/ai/unified-ai-request-pipeline.ts

@@ -3,6 +3,7 @@ import {AI_VOICE_MODE_TRANSCRIPT, DEFAULT_AI_RESPONSE_LANGUAGE} from "../common/
 import {Environment} from "../common/environment";
 import {UserRequestPipeline, type UserRequestPipelineState, type UserRequestPipelineStage} from "./user-request-pipeline";
 import {PipelineFallbackNotifier} from "./user-request-pipeline/fallback-notifier";
+import {buildToolRankFallbackTargetDetails} from "./user-request-pipeline/fallback-target-details";
 import type {AiDownloadedFile} from "./telegram-attachments";
 import type {TelegramStreamMessage} from "./telegram-stream-message";
 import type {ChatMessage} from "./chat-messages-types";
@@ -304,6 +305,23 @@ export async function prepareUnifiedAiRequestPipeline(params: {
             "audit_finish",
         ],
         onFallback: async decision => {
+            if (decision.action === "use_alternate_target") {
+                aiLog("warn", "request.fallback.use_alternate_target", {
+                    provider: options.provider,
+                    stage: decision.stage,
+                    reason: decision.reason,
+                    ...buildToolRankFallbackTargetDetails(options.provider, config),
+                });
+            }
+
+            if (decision.action === "fail_request") {
+                aiLog("error", "request.fallback.fail_request", {
+                    provider: options.provider,
+                    stage: decision.stage,
+                    reason: decision.reason,
+                });
+            }
+
             const notification = await fallbackNotifier.notify(state.requestId, decision);
             state.audit.push({
                 stage: decision.stage,
@@ -315,6 +333,9 @@ export async function prepareUnifiedAiRequestPipeline(params: {
                     fallbackNotification: notification.text,
                     fallbackNotified: notification.notified,
                     reason: decision.reason,
+                    ...(decision.action === "use_alternate_target"
+                        ? buildToolRankFallbackTargetDetails(options.provider, config)
+                        : {}),
                 },
             });
         },

src/ai/unified-ai-response-pipeline.ts

@@ -25,6 +25,7 @@ import {summarizeModelOutput} from "./response-model-output";
 import {summarizeToolLoop} from "./tool-loop-summary";
 import {persistToolLoopSummaryArtifactAttachment} from "./tool-loop-artifact-store";
 import {PipelineFallbackNotifier} from "./user-request-pipeline/fallback-notifier";
+import {buildToolRankFallbackTargetDetails} from "./user-request-pipeline/fallback-target-details";
 import {
     resolveTextToSpeechProviderForUser,
     sendSynthesizedSpeech,
@@ -395,6 +396,23 @@ export async function runUnifiedAiResponsePipeline(params: {
             "audit_finish",
         ],
         onFallback: async decision => {
+            if (decision.action === "use_alternate_target") {
+                aiLog("warn", "response.fallback.use_alternate_target", {
+                    provider: options.provider,
+                    stage: decision.stage,
+                    reason: decision.reason,
+                    ...buildToolRankFallbackTargetDetails(options.provider, config),
+                });
+            }
+
+            if (decision.action === "fail_request") {
+                aiLog("error", "response.fallback.fail_request", {
+                    provider: options.provider,
+                    stage: decision.stage,
+                    reason: decision.reason,
+                });
+            }
+
             const notification = await fallbackNotifier.notify(state.requestId, decision);
             state.audit.push({
                 stage: decision.stage,
@@ -406,6 +424,9 @@ export async function runUnifiedAiResponsePipeline(params: {
                     fallbackNotification: notification.text,
                     fallbackNotified: notification.notified,
                     reason: decision.reason,
+                    ...(decision.action === "use_alternate_target"
+                        ? buildToolRankFallbackTargetDetails(options.provider, config)
+                        : {}),
                 },
             });
         },

src/ai/user-request-pipeline/fallback-failure.ts

@@ -0,0 +1,12 @@
+import type {PipelineFallbackDecision} from "./fallback-executor.js";
+
+export class PipelineRequestFailure extends Error {
+    constructor(public readonly decision: PipelineFallbackDecision, message: string) {
+        super(message);
+        this.name = "PipelineRequestFailure";
+    }
+}
+
+export function raisePipelineRequestFailure(decision: PipelineFallbackDecision, stageName: string): never {
+    throw new PipelineRequestFailure(decision, `Pipeline send failed at stage ${stageName} with fallback action ${decision.action}`);
+}

src/ai/user-request-pipeline/fallback-target-details.ts

@@ -0,0 +1,15 @@
+import {AiProvider} from "../../model/ai-provider.js";
+import type {RuntimeConfigSnapshot} from "../unified-ai-runner.shared.js";
+import {aiLogProviderTarget} from "../../logging/ai-logger.js";
+import {buildRankerTarget} from "../tool-ranker-pipeline.js";
+import {providerChatTarget} from "../unified-ai-runner.shared.js";
+
+export function buildToolRankFallbackTargetDetails(provider: AiProvider, config: RuntimeConfigSnapshot) {
+    const sourceTarget = buildRankerTarget(config, provider);
+    const alternateTarget = providerChatTarget(provider, config);
+
+    return {
+        sourceTarget: aiLogProviderTarget(sourceTarget),
+        alternateTarget: aiLogProviderTarget(alternateTarget),
+    };
+}

src/ai/user-request-pipeline/pipeline.ts

@@ -1,5 +1,6 @@
 import {DEFAULT_PIPELINE_FALLBACK_POLICIES, USER_REQUEST_PIPELINE_STAGES} from "./blueprint.js";
 import {decidePipelineFallback, type PipelineFallbackDecision} from "./fallback-executor.js";
+import {raisePipelineRequestFailure} from "./fallback-failure.js";
 import type {
     PipelineAuditEvent,
     PipelineFallbackPolicy,
@@ -66,7 +67,7 @@ export class UserRequestPipeline {
                     },
                 }));
                 if (decision.shouldFailRequest) {
-                    throw new Error(`Required pipeline stage is not registered: ${stageName}`);
+                    raisePipelineRequestFailure(decision, stageName);
                 }
                 continue;
             }
@@ -112,7 +113,7 @@ export class UserRequestPipeline {
                     error: error instanceof Error ? error.message : String(error),
                 }));
                 if (decision.shouldFailRequest) {
-                    throw error;
+                    raisePipelineRequestFailure(decision, stageName);
                 }
             }
         }