fix(session): stop the base store warning on every session load

The live-turns read went through the isogit base's load(), which also
validates metadata.json against the vendor shape. This store writes
token usage to the sidecar instead, so every cold load failed that
validation, warned, and re-parsed turns.jsonl from disk. Parse the base
segment directly; metadata already has its own lenient reader that
still warns on a malformed document. Relaxing the vendored schema would
add a ledgered patch for a file the base store no longer owns.

Author: bwachman

src/session/optimized-context-store.test.ts

@@ -1,4 +1,5 @@
 import { defined } from "../../testkit/defined.js";
+import { withFileLogSink } from "../../testkit/file-log-sink.js";
 import { describe, test, expect } from "bun:test";
 import fs from "node:fs";
 import os from "node:os";
@@ -13,6 +14,7 @@ import {
 } from "./optimized-context-store.js";
 import { segmentFileName, listSegmentFiles } from "./incremental-jsonl.js";
 import { createPruningCompactor } from "./compactor.js";
+import { LOG_NAMESPACE_ROOT } from "../branding.js";
 
 const TURNS_FILE = "turns.jsonl";
 
@@ -421,6 +423,81 @@ describe("createOptimizedContextStore load", () => {
   });
 });
 
+describe("createOptimizedContextStore load warnings", () => {
+  function contextStoreWarnings(logged: string): string[] {
+    return logged
+      .split("\n")
+      .filter((line) => line.length > 0)
+      .map((line) => JSON.parse(line) as Record<string, unknown>)
+      .filter(
+        (record) =>
+          record.level === "warning" &&
+          record.category === `${LOG_NAMESPACE_ROOT}.session.context-store`,
+      )
+      .map((record) => JSON.stringify(record));
+  }
+
+  const pendingOp = {
+    correlationId: "corr-1",
+    kind: "approval" as const,
+    registeredAt: 1_700_000_000_000,
+    gateId: "gate-1",
+  };
+  const usage = {
+    input: 7,
+    output: 3,
+    cacheRead: 0,
+    cacheWrite: 0,
+    thinking: 0,
+  };
+
+  test("a cold load of a store written the current way logs no warning", async () => {
+    const dir = tempDir();
+    const writer = await createOptimizedContextStore(dir);
+    await writer.writeTurns([turn("a"), turn("b")]);
+    await writer.writeMetadata({
+      pendingOperations: [pendingOp],
+      tokenUsage: usage,
+    });
+    await writer.commit({ message: "checkpoint: tool-execution" });
+
+    let loaded: Awaited<ReturnType<typeof writer.load>> | undefined;
+    const logged = await withFileLogSink(async () => {
+      const resumed = await createOptimizedContextStore(dir);
+      loaded = await resumed.load();
+    });
+
+    expect(contextStoreWarnings(logged)).toEqual([]);
+    expect(turnTexts(defined(loaded).turns)).toEqual(["a", "b"]);
+    expect(defined(loaded).pendingOperations).toEqual([pendingOp]);
+    expect(defined(loaded).tokenUsage).toEqual(usage);
+  });
+
+  test("a malformed metadata.json still warns on load", async () => {
+    const dir = tempDir();
+    const writer = await createOptimizedContextStore(dir);
+    await writer.writeTurns([turn("a")]);
+    await writer.writeMetadata(EMPTY_CHECKPOINT_METADATA);
+    await writer.commit({ message: "checkpoint: tool-execution" });
+    fs.writeFileSync(
+      path.join(dir, "metadata.json"),
+      JSON.stringify({ pendingOperations: 42 }),
+    );
+
+    let loaded: Awaited<ReturnType<typeof writer.load>> | undefined;
+    const logged = await withFileLogSink(async () => {
+      const resumed = await createOptimizedContextStore(dir);
+      loaded = await resumed.load();
+    });
+
+    const warnings = contextStoreWarnings(logged);
+    expect(warnings).toHaveLength(1);
+    expect(warnings[0]).toContain("metadata.json has unexpected structure");
+    expect(turnTexts(defined(loaded).turns)).toEqual(["a"]);
+    expect(defined(loaded).pendingOperations).toEqual([]);
+  });
+});
+
 describe("loadRecentTurns", () => {
   test("reads only the tail segments needed to satisfy the window, in order", async () => {
     const dir = tempDir();

src/session/optimized-context-store.ts

@@ -510,9 +510,8 @@ export async function loadRecentTurns(
 }
 
 /**
- * Resilient parse of `turns.jsonl` alone (extras merged by the caller).
- * Mirrors `load()`'s recovery when the isogit base hard-fails, so a torn or
- * poisoned base cannot block the healing write.
+ * Resilient parse of `turns.jsonl` alone (extras merged by the caller), so a
+ * torn or poisoned base cannot block the healing write.
  */
 async function readBaseTurnsFromDisk(dir: string): Promise<ConversationTurn[]> {
   const basePath = path.join(dir, TURNS_FILE);
@@ -1358,9 +1357,7 @@ export async function createSessionStores(
     return count;
   }
 
-  async function readLiveTurnsCached(
-    signal?: AbortSignal,
-  ): Promise<ConversationTurn[]> {
+  async function readLiveTurnsCached(): Promise<ConversationTurn[]> {
     const segments = await turnSegmentStats();
     if (
       turnsCache !== null &&
@@ -1375,23 +1372,14 @@ export async function createSessionStores(
         : sharedSegmentPrefix(turnsCache.segments, segments);
     // Base segment stat unchanged: its parse is still exactly what disk
     // holds, so only the newer segments get re-read and re-parsed.
-    let baseTurns: ConversationTurn[];
-    if (reused >= 1 && turnsCache !== null) {
-      baseTurns = turnsCache.baseTurns;
-    } else {
-      try {
-        baseTurns = (await base.load(signal)).turns;
-      } catch (cause) {
-        // A torn or poisoned base must not block the healing write; recover
-        // the usable turns the same way load() always has. Corrupt
-        // metadata.json also slides — callers here only need the turns.
-        log.warn(
-          "base context store load failed; recovering base segment from disk",
-          { cause: cause instanceof Error ? cause.message : String(cause) },
-        );
-        baseTurns = await readBaseTurnsFromDisk(dir);
-      }
-    }
+    // Otherwise parse turns.jsonl here rather than through the isogit base's
+    // load(): that also validates metadata.json against the vendor shape,
+    // which this store no longer writes (tokenUsage lives on the sidecar).
+    // Metadata is read separately by readSessionMetadata.
+    const baseTurns =
+      reused >= 1 && turnsCache !== null
+        ? turnsCache.baseTurns
+        : await readBaseTurnsFromDisk(dir);
     const parsedExtras: ConversationTurn[][] = [];
     for (let index = 1; index < segments.length; index++) {
       const cached =
@@ -1422,10 +1410,8 @@ export async function createSessionStores(
     return merged;
   }
 
-  async function readLiveTurns(
-    signal?: AbortSignal,
-  ): Promise<ConversationTurn[]> {
-    return readLiveTurnsCached(signal);
+  async function readLiveTurns(): Promise<ConversationTurn[]> {
+    return readLiveTurnsCached();
   }
 
   async function resolveFirstWrite(
@@ -1546,15 +1532,15 @@ export async function createSessionStores(
 
   const store: ContextStore & AuditStore = {
     // Full-history read: the reactor's initialization contract. Turns come
-    // through the shared generation cache (strict base parse with resilient
-    // recovery, resilient extras, orphan-tail heal), so a repeated load within
-    // one store generation does not re-parse segments whose stat is unchanged.
+    // through the shared generation cache (resilient base and extras,
+    // orphan-tail heal), so a repeated load within one store generation does
+    // not re-parse segments whose stat is unchanged.
     // Metadata stays a fresh read: corrupt metadata.json soft-defaults so
     // resume does not die or wipe pending ops.
-    async load(signal) {
+    async load() {
       let turns: ConversationTurn[];
       try {
-        turns = await readLiveTurnsCached(signal);
+        turns = await readLiveTurnsCached();
       } catch (cause) {
         // Unrecoverable history: rethrow with the file name in the message.
         throw new Error(