refactor: migrate agent context assembly to TypeScript

Author: tomdps

.gitignore

@@ -184,6 +184,8 @@ src/agent/context-metrics.js
 src/agent/agent-liveness-poll.js
 src/agent/context-replay-policy.js
 src/agent/agent-context-sources.js
+src/agent/agent-context-builder.js
+src/agent/agent-context-packs.js
 src/agent/agent-context-sections.js
 src/agent/agent-context-types.js
 src/agent/agent-context-environment-sections.js

eslint.config.mjs

@@ -438,6 +438,8 @@ export default [
       'src/agent/output-extraction-failures.js',
       'src/agent/agent-trigger-evaluator.js',
       'src/agent/agent-context-sections.js',
+      'src/agent/agent-context-builder.js',
+      'src/agent/agent-context-packs.js',
       'src/agent/agent-context-types.js',
       'src/agent/agent-context-environment-sections.js',
       'src/agent/agent-context-prompt-sections.js',

src/agent/agent-context-builder.js

@@ -0,0 +1,51 @@
+import contextMetrics = require('./context-metrics');
+import contextPackBuilder = require('./context-pack-builder');
+import agentContextPacks = require('./agent-context-packs');
+
+import type { BuildContextParams, ContextStrategy } from './agent-context-types';
+
+const MAX_CONTEXT_CHARS = 500000;
+const { buildContextMetrics, emitContextMetrics, resolveLegacyMaxTokens, updateTotalMetrics } =
+  contextMetrics;
+const { buildContextPacks } = contextPackBuilder;
+const { buildAgentContextPacks } = agentContextPacks;
+
+function buildContext(params: BuildContextParams): string {
+  const strategy: ContextStrategy = params.config.contextStrategy || { sources: [] };
+  const continuation = params.mode === 'continuation';
+  const packs = buildAgentContextPacks(params, strategy, continuation);
+  const maxTokens = resolveLegacyMaxTokens(strategy);
+  const packResult = buildContextPacks({
+    packs,
+    maxTokens,
+    maxChars: MAX_CONTEXT_CHARS,
+  });
+
+  const metrics = buildContextMetrics({
+    clusterId: params.cluster.id,
+    agentId: params.id,
+    role: params.role,
+    iteration: params.iteration,
+    triggeringMessage: params.triggeringMessage,
+    strategy: {
+      ...strategy,
+      contextMode: continuation ? 'continuation' : 'full',
+    },
+    packs: packResult.packDecisions,
+    budget: packResult.budget,
+    truncation: packResult.truncation,
+  });
+
+  updateTotalMetrics(metrics, packResult.context.length);
+  emitContextMetrics(metrics, {
+    messageBus: params.messageBus,
+    clusterId: params.cluster.id,
+    agentId: params.id,
+  });
+
+  return packResult.context;
+}
+
+export = {
+  buildContext,
+};