refactor(agents): remove transcript token cost enrichment

artifacts/architecture-design.md

@@ -155,7 +155,6 @@ interface Agent {
 
   // Optional
   postLaunchSetup?(session: Session): Promise<void>;
-  estimateCost?(session: Session): Promise<CostEstimate>;
 }
 ```
 

packages/core/src/session-manager.ts

@@ -1157,7 +1157,7 @@ export function createSessionManager(deps: SessionManagerDeps): OpenCodeSessionM
         session.activitySignal = createActivitySignal("probe_failure", { source: "native" });
       }
 
-      // Enrich with agent session info (summary, cost, native restore metadata).
+      // Enrich with lightweight agent session info (summary and native restore metadata).
       await persistAgentSessionInfo();
     }
   }

packages/core/src/types.ts

@@ -311,7 +311,7 @@ export interface Session {
   /** Runtime handle for communicating with the session */
   runtimeHandle: RuntimeHandle | null;
 
-  /** Agent session info (summary, cost, etc.) */
+  /** Agent session info (summary and native restore metadata) */
   agentInfo: AgentSessionInfo | null;
 
   /** When the session was created */
@@ -515,7 +515,7 @@ export interface Agent {
    */
   isProcessRunning(handle: RuntimeHandle): Promise<ProcessProbeResult>;
 
-  /** Extract information from agent's internal data (summary, cost, session ID) */
+  /** Extract lightweight information from agent-owned metadata (summary and native session ID) */
   getSessionInfo(session: Session): Promise<AgentSessionInfo | null>;
 
   /**
@@ -636,14 +636,6 @@ export interface AgentSessionInfo {
   agentSessionId: string | null;
   /** Agent-owned metadata worth persisting for later restore. */
   metadata?: Record<string, string>;
-  /** Estimated cost so far */
-  cost?: CostEstimate;
-}
-
-export interface CostEstimate {
-  inputTokens: number;
-  outputTokens: number;
-  estimatedCostUsd: number;
 }
 
 // =============================================================================

packages/plugins/agent-aider/src/index.test.ts

@@ -6,12 +6,13 @@ import {
   type AgentLaunchConfig,
 } from "@aoagents/ao-core";
 
-// Mock fs/promises for getSessionInfo tests (readFile for .aider.chat.history.md)
+// Mock fs/promises for getSessionInfo tests
 vi.mock("node:fs/promises", async (importOriginal) => {
   const actual = (await importOriginal()) as Record<string, unknown>;
   return {
     ...actual,
     readFile: vi.fn().mockRejectedValue(new Error("ENOENT")),
+    open: vi.fn().mockRejectedValue(new Error("ENOENT")),
   };
 });
 
@@ -125,6 +126,24 @@ function mockTmuxWithProcess(processName: string, found = true) {
   });
 }
 
+function makeFakeFileHandle(content: string) {
+  const buf = Buffer.from(content, "utf-8");
+  return {
+    read: vi
+      .fn()
+      .mockImplementation(
+        (buffer: Buffer, offset: number, length: number, position: number | null) => {
+          const start = position ?? 0;
+          if (start >= buf.length) return Promise.resolve({ bytesRead: 0, buffer });
+          const bytesToCopy = Math.min(length, buf.length - start);
+          buf.copy(buffer, offset, start, start + bytesToCopy);
+          return Promise.resolve({ bytesRead: bytesToCopy, buffer });
+        },
+      ),
+    close: vi.fn().mockResolvedValue(undefined),
+  };
+}
+
 beforeEach(() => {
   vi.clearAllMocks();
 });
@@ -412,28 +431,29 @@ describe("getSessionInfo", () => {
   });
 
   it("returns null when no chat history file exists", async () => {
-    const { readFile } = await import("node:fs/promises");
-    vi.mocked(readFile).mockRejectedValueOnce(new Error("ENOENT"));
+    const { open } = await import("node:fs/promises");
+    vi.mocked(open).mockRejectedValueOnce(new Error("ENOENT"));
     expect(await agent.getSessionInfo(makeSession())).toBeNull();
   });
 
   it("extracts summary from chat history file", async () => {
-    const { readFile } = await import("node:fs/promises");
-    vi.mocked(readFile).mockResolvedValueOnce(
-      "# aider chat started\n\n#### Fix the login bug in auth.ts\n\nSome response here...\n",
+    const { open } = await import("node:fs/promises");
+    vi.mocked(open).mockResolvedValueOnce(
+      makeFakeFileHandle(
+        "# aider chat started\n\n#### Fix the login bug in auth.ts\n\nSome response here...\n",
+      ) as never,
     );
     const info = await agent.getSessionInfo(makeSession());
     expect(info).not.toBeNull();
     expect(info!.summary).toBe("Fix the login bug in auth.ts");
     expect(info!.summaryIsFallback).toBe(true);
     expect(info!.agentSessionId).toBeNull();
-    expect(info!.cost).toBeUndefined();
   });
 
   it("truncates long summaries to 120 chars", async () => {
-    const { readFile } = await import("node:fs/promises");
+    const { open } = await import("node:fs/promises");
     const longMsg = "A".repeat(200);
-    vi.mocked(readFile).mockResolvedValueOnce(`#### ${longMsg}\n`);
+    vi.mocked(open).mockResolvedValueOnce(makeFakeFileHandle(`#### ${longMsg}\n`) as never);
     const info = await agent.getSessionInfo(makeSession());
     expect(info!.summary).toHaveLength(123); // 120 + "..."
     expect(info!.summary!.endsWith("...")).toBe(true);

packages/plugins/agent-aider/src/index.ts

@@ -23,7 +23,7 @@ import {
 } from "@aoagents/ao-core";
 import { execFile, execFileSync } from "node:child_process";
 import { promisify } from "node:util";
-import { stat, access, readFile } from "node:fs/promises";
+import { stat, access, open } from "node:fs/promises";
 import { join } from "node:path";
 import { constants, readFileSync } from "node:fs";
 
@@ -59,7 +59,15 @@ async function getChatHistoryMtime(workspacePath: string): Promise<Date | null>
 async function extractAiderSummary(workspacePath: string): Promise<string | null> {
   try {
     const chatFile = join(workspacePath, ".aider.chat.history.md");
-    const content = await readFile(chatFile, "utf-8");
+    const handle = await open(chatFile, "r");
+    let content: string;
+    try {
+      const buffer = Buffer.allocUnsafe(64 * 1024);
+      const { bytesRead } = await handle.read(buffer, 0, buffer.length, 0);
+      content = buffer.subarray(0, bytesRead).toString("utf-8");
+    } finally {
+      await handle.close();
+    }
 
     // Aider chat history uses "#### " prefix for user messages
     for (const line of content.split("\n")) {
@@ -277,7 +285,6 @@ function createAiderAgent(): Agent {
         summary,
         summaryIsFallback: true,
         agentSessionId: null,
-        // Aider doesn't expose token/cost data
       };
     },