fix: validate and compact session entries

src/main/agent-runtime/agent-message-schema.ts

@@ -0,0 +1,100 @@
+import type { AgentMessage } from "@mariozechner/pi-agent-core";
+
+const AGENT_MESSAGE_SCHEMA_VERSION = 1;
+const ALLOWED_AGENT_MESSAGE_ROLES = new Set(["user", "assistant", "toolResult"]);
+
+interface PersistedAgentMessageEnvelope {
+  schemaVersion: 1;
+  kind: "agent_message";
+  message: AgentMessage;
+  persistedAt: string;
+}
+
+interface SessionEntryPayloadRow {
+  id: string;
+  payloadJson: string;
+}
+
+function formatMessageError(prefix: string, message: string): Error {
+  return new Error(`${prefix}: ${message}`);
+}
+
+function assertRecord(value: unknown, prefix: string): asserts value is Record<string, unknown> {
+  if (!value || typeof value !== "object" || Array.isArray(value)) {
+    throw formatMessageError(prefix, "expected an object");
+  }
+}
+
+function normalizeAgentMessageForSession(
+  input: AgentMessage,
+  prefix = "Invalid AgentMessage",
+  options: { requireTimestamp: boolean } = { requireTimestamp: true },
+): AgentMessage {
+  assertRecord(input, prefix);
+  const role = input.role;
+  if (typeof role !== "string" || !ALLOWED_AGENT_MESSAGE_ROLES.has(role)) {
+    throw formatMessageError(prefix, `invalid role ${typeof role === "string" ? JSON.stringify(role) : "<missing>"}`);
+  }
+  const content = (input as { content?: unknown }).content;
+  if (typeof content !== "string" && !Array.isArray(content)) {
+    throw formatMessageError(prefix, "content must be a string or an array");
+  }
+  const timestamp = (input as { timestamp?: unknown }).timestamp;
+  if (typeof timestamp !== "number" || !Number.isFinite(timestamp)) {
+    if (options.requireTimestamp) {
+      throw formatMessageError(prefix, "timestamp must be a finite number");
+    }
+    return {
+      ...input,
+      timestamp: Date.now(),
+    } as AgentMessage;
+  }
+  return input;
+}
+
+export function validateNewAgentMessageForSession(input: AgentMessage, prefix = "Invalid AgentMessage"): AgentMessage {
+  return normalizeAgentMessageForSession(input, prefix, { requireTimestamp: true });
+}
+
+function normalizeLegacyAgentMessageForSession(input: AgentMessage, prefix = "Invalid legacy AgentMessage"): AgentMessage {
+  return normalizeAgentMessageForSession(input, prefix, { requireTimestamp: false });
+}
+
+export function encodeAgentMessageForSession(message: AgentMessage, persistedAt = new Date().toISOString()): string {
+  const normalized = validateNewAgentMessageForSession(message);
+  const envelope: PersistedAgentMessageEnvelope = {
+    schemaVersion: AGENT_MESSAGE_SCHEMA_VERSION,
+    kind: "agent_message",
+    message: normalized,
+    persistedAt,
+  };
+  return JSON.stringify(envelope);
+}
+
+export function decodeAgentMessageFromSessionEntry(row: SessionEntryPayloadRow): AgentMessage {
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(row.payloadJson);
+  } catch (error) {
+    throw new Error(
+      `Invalid session entry ${row.id} payload JSON: ${error instanceof Error ? error.message : String(error)}`,
+    );
+  }
+  assertRecord(parsed, `Invalid session entry ${row.id}`);
+
+  if (parsed.schemaVersion === AGENT_MESSAGE_SCHEMA_VERSION || parsed.kind === "agent_message") {
+    if (parsed.schemaVersion !== AGENT_MESSAGE_SCHEMA_VERSION || parsed.kind !== "agent_message") {
+      throw new Error(`Invalid session entry ${row.id}: unsupported AgentMessage envelope`);
+    }
+    return validateNewAgentMessageForSession(
+      parsed.message as AgentMessage,
+      `Invalid session entry ${row.id} AgentMessage`,
+    );
+  }
+
+  return normalizeLegacyAgentMessageForSession(parsed as unknown as AgentMessage, `Invalid legacy session entry ${row.id}`);
+}
+
+export function getAgentMessageRole(message: AgentMessage): string {
+  return validateNewAgentMessageForSession(message).role as string;
+}

src/main/agent-runtime/sqlite-session-store.ts

@@ -1,15 +1,22 @@
 import type { AgentMessage } from "@mariozechner/pi-agent-core";
 import type { AppDatabase } from "@main/database";
+import { compactMessagesIfNeeded } from "./context-compactor";
+import {
+  decodeAgentMessageFromSessionEntry,
+  encodeAgentMessageForSession,
+  getAgentMessageRole,
+  validateNewAgentMessageForSession,
+} from "./agent-message-schema";
 
 /**
  * SQLite-backed pi `AgentMessage[]` store.
  *
  * One store instance per task_session. `appendMessage` runs exactly
  * once per pi `message_end` event; `loadMessages` reads the live
- * transcript back at `prepareRun`. Compaction happens at LLM-call
- * time via pi's `transformContext` hook and does not rewrite the
- * persisted transcript — the session shadow is the durable truth,
- * the compacted payload is a per-call view.
+ * transcript back at `prepareRun`. When the persisted transcript
+ * crosses the compaction threshold, `loadMessages` writes a durable
+ * summary row and supersedes the older rows inside one DB transaction,
+ * leaving the recent tail as the active transcript.
  */
 export class SqliteSessionStore {
   constructor(
@@ -19,21 +26,37 @@ export class SqliteSessionStore {
 
   loadMessages(): AgentMessage[] {
     const rows = this.db.projection.sessionEntries.listActive(this.taskSessionId);
-    const result: AgentMessage[] = [];
+    const messages: AgentMessage[] = [];
     for (const row of rows) {
       if (row.kind === "message") {
-        result.push(JSON.parse(row.payloadJson) as AgentMessage);
+        messages.push(decodeAgentMessageFromSessionEntry(row));
       }
     }
-    return result;
+    const outcome = compactMessagesIfNeeded(messages);
+    if (!outcome.changed || !outcome.messages || !outcome.telemetry) {
+      return messages;
+    }
+    const summary = outcome.messages[0];
+    if (!summary) {
+      return messages;
+    }
+    const olderRows = rows.slice(0, outcome.telemetry.compactedOlderMessageCount);
+    this.db.projection.sessionEntries.compactWithSummary({
+      taskSessionId: this.taskSessionId,
+      supersedeEntryIds: olderRows.map((row) => row.id),
+      summaryRole: getAgentMessageRole(summary),
+      summaryPayloadJson: encodeAgentMessageForSession(summary),
+    });
+    return outcome.messages;
   }
 
   appendMessage(message: AgentMessage): void {
+    const normalized = validateNewAgentMessageForSession(message);
     this.db.projection.sessionEntries.append({
       taskSessionId: this.taskSessionId,
       kind: "message",
-      role: (message as { role?: string }).role ?? null,
-      payloadJson: JSON.stringify(message),
+      role: getAgentMessageRole(normalized),
+      payloadJson: encodeAgentMessageForSession(normalized),
     });
   }
 }

src/main/database/session-entries.ts

@@ -1,5 +1,5 @@
 import { randomUUID } from "node:crypto";
-import type { DatabaseSync } from "node:sqlite";
+import type { DatabaseSync, SQLInputValue } from "node:sqlite";
 import type { ReadAll, Transaction } from "./helpers";
 import { nowIso } from "./helpers";
 
@@ -33,7 +33,7 @@ export interface AppendInput {
 export function buildSessionEntryMethods(
   getDb: () => DatabaseSync,
   readAll: ReadAll,
-  _transaction: Transaction,
+  transaction: Transaction,
 ) {
   function nextSequence(taskSessionId: string): number {
     const rows = readAll<{ maxSeq: number | null }>(
@@ -82,7 +82,7 @@ export function buildSessionEntryMethods(
       payload_json: string;
       created_at: string;
     }>(
-      "select id, task_session_id, sequence, kind, role, payload_json, created_at from session_entries where task_session_id = ? and is_superseded = 0 order by created_at asc, sequence asc",
+      "select id, task_session_id, sequence, kind, role, payload_json, created_at from session_entries where task_session_id = ? and is_superseded = 0 order by sequence asc, created_at asc",
       taskSessionId,
     );
     return rows.map((row) => ({
@@ -96,5 +96,52 @@ export function buildSessionEntryMethods(
     }));
   }
 
-  return { append, listActive };
+  function compactWithSummary(input: {
+    taskSessionId: string;
+    supersedeEntryIds: string[];
+    summaryRole: string | null;
+    summaryPayloadJson: string;
+  }): SessionEntryRow {
+    return transaction(() => {
+      const uniqueIds = [...new Set(input.supersedeEntryIds)];
+      if (uniqueIds.length === 0) {
+        throw new Error("session_entries compaction requires at least one entry to supersede.");
+      }
+      const placeholders = uniqueIds.map(() => "?").join(", ");
+      const rows = readAll<{ id: string; sequence: number }>(
+        `select id, sequence from session_entries where task_session_id = ? and is_superseded = 0 and id in (${placeholders}) order by sequence asc`,
+        input.taskSessionId,
+        ...(uniqueIds as SQLInputValue[]),
+      );
+      if (rows.length !== uniqueIds.length) {
+        throw new Error(`session_entries compaction expected ${uniqueIds.length} active row(s), found ${rows.length}.`);
+      }
+      const summarySequence = rows[0]?.sequence;
+      if (summarySequence === undefined) {
+        throw new Error("session_entries compaction could not resolve summary sequence.");
+      }
+      getDb()
+        .prepare(`update session_entries set is_superseded = 1 where task_session_id = ? and id in (${placeholders})`)
+        .run(input.taskSessionId, ...(uniqueIds as SQLInputValue[]));
+
+      const id = randomUUID();
+      const created = nowIso();
+      getDb()
+        .prepare(
+          "insert into session_entries (id, task_session_id, sequence, kind, role, payload_json, is_superseded, created_at) values (?, ?, ?, 'message', ?, ?, 0, ?)",
+        )
+        .run(id, input.taskSessionId, summarySequence, input.summaryRole, input.summaryPayloadJson, created);
+      return {
+        id,
+        taskSessionId: input.taskSessionId,
+        sequence: summarySequence,
+        kind: "message",
+        role: input.summaryRole,
+        payloadJson: input.summaryPayloadJson,
+        createdAt: created,
+      };
+    });
+  }
+
+  return { append, listActive, compactWithSummary };
 }