feat(models): add background task model override config and runtime wiring

src/gateway/session-bridge.ts

@@ -2,12 +2,13 @@ import { randomUUID } from 'crypto';
 import type { SessionManager } from '../session/manager.js';
 import type { ModelClient } from '../models/types.js';
 import type { ModelRouter, ModelTier } from '../models/router.js';
+import { createClientFromConfig } from '../daemon/models.js';
+import type { Config, ModelConfig, ModelProvider } from '../config/index.js';
 import type { ToolRegistry } from '../tools/registry.js';
 import type { ToolExecutor } from '../tools/executor.js';
 import { AgentOrchestrator, type DelegationConfig } from '../backends/native/orchestrator.js';
 import type { ToolUseEvent } from '../backends/native/agent.js';
 import type { MemoryStore } from '../memory/store.js';
-import type { Config } from '../config/index.js';
 import { summarizeSessionOnEnd, type SessionEndSummaryConfig } from '../session/endSummary.js';
 
 export interface SessionBridgeConfig {
@@ -284,6 +285,7 @@ export class SessionBridge {
         tool_summarisation: config?.agents.delegation.tool_summarisation ?? 'fast',
         complex_reasoning: config?.agents.delegation.complex_reasoning ?? 'complex',
       };
+      const backgroundModelOverrides = this.buildBackgroundModelOverrides();
 
       agent = new AgentOrchestrator({
         modelRouter: this.config.modelClient as ModelRouter,
@@ -293,6 +295,7 @@ export class SessionBridge {
         toolExecutor: this.config.toolExecutor,
         primaryTier,
         delegation: delegationConfig,
+        backgroundModelOverrides,
         maxDelegationDepth: config?.agents.max_delegation_depth ?? 3,
         maxIterations: config?.agents.max_iterations,
         compaction: config?.compaction.enabled ? {
@@ -337,4 +340,77 @@ export class SessionBridge {
     }
     return agent;
   }
+
+  private buildBackgroundModelOverrides(): Partial<Record<keyof DelegationConfig, {
+    client: ModelClient;
+    label: string;
+    fallbackTier: ModelTier;
+  }>> {
+    const runtimeConfig = this.config.config;
+    const overrides: Partial<Record<keyof DelegationConfig, {
+      client: ModelClient;
+      label: string;
+      fallbackTier: ModelTier;
+    }>> = {};
+    if (!runtimeConfig) {
+      return overrides;
+    }
+
+    const providerConfigs = this.buildProviderConfigMap(runtimeConfig);
+    const configured = runtimeConfig.agents?.background_models ?? {};
+    const tasks: Array<keyof DelegationConfig> = [
+      'compaction',
+      'memory_extraction',
+      'classification',
+      'tool_summarisation',
+      'complex_reasoning',
+    ];
+
+    for (const task of tasks) {
+      const entry = configured[task];
+      if (!entry || entry.enabled === false) {
+        continue;
+      }
+      const template = providerConfigs[entry.provider];
+      try {
+        const client = createClientFromConfig(
+          template
+            ? { ...template, provider: entry.provider, model: entry.model }
+            : { provider: entry.provider, model: entry.model },
+        );
+        overrides[task] = {
+          client,
+          label: `${entry.provider}/${entry.model}`,
+          fallbackTier: entry.fallback_tier,
+        };
+      } catch (error) {
+        console.warn(
+          `[Flynn:gateway] Failed to initialize background model override for ${task} ` +
+          `(${entry.provider}/${entry.model}): ${error instanceof Error ? error.message : String(error)}`,
+        );
+      }
+    }
+
+    return overrides;
+  }
+
+  private buildProviderConfigMap(config: Config): Partial<Record<ModelProvider, ModelConfig>> {
+    const providerConfigs: Partial<Record<ModelProvider, ModelConfig>> = {};
+    const modelConfigs: ModelConfig[] = [
+      config.models.default,
+      ...(config.models.fast ? [config.models.fast] : []),
+      ...(config.models.complex ? [config.models.complex] : []),
+      ...(config.models.local ? [config.models.local] : []),
+      ...Object.values(config.models.local_providers ?? {}),
+    ];
+
+    for (const modelConfig of modelConfigs) {
+      providerConfigs[modelConfig.provider] = modelConfig;
+      if (modelConfig.fallback) {
+        providerConfigs[modelConfig.fallback.provider] = modelConfig.fallback;
+      }
+    }
+
+    return providerConfigs;
+  }
 }