fix: prefer deterministic transcript session keys

src/gateway/session-transcript-key.test.ts

@@ -113,4 +113,18 @@ describe("resolveSessionKeyForTranscriptFile", () => {
     expect(resolveSessionKeyForTranscriptFile("   ")).toBeUndefined();
     expect(loadCombinedSessionStoreForGatewayMock).not.toHaveBeenCalled();
   });
+
+  it("prefers the deterministic session key when duplicate sessionIds share a transcript path", () => {
+    const store = {
+      "agent:other:main": { sessionId: "run-dup", updatedAt: now + 1 },
+      "agent:main:acp:run-dup": { sessionId: "run-dup", updatedAt: now },
+    } satisfies Record<string, SessionEntry>;
+    loadCombinedSessionStoreForGatewayMock.mockReturnValue({
+      storePath: "(multiple)",
+      store,
+    });
+    resolveSessionTranscriptCandidatesMock.mockReturnValue(["/tmp/shared.jsonl"]);
+
+    expect(resolveSessionKeyForTranscriptFile("/tmp/shared.jsonl")).toBe("agent:main:acp:run-dup");
+  });
 });

src/gateway/session-transcript-key.ts

@@ -3,6 +3,7 @@ import path from "node:path";
 import { loadConfig } from "../config/config.js";
 import type { SessionEntry } from "../config/sessions/types.js";
 import { normalizeAgentId } from "../routing/session-key.js";
+import { resolvePreferredSessionKeyForSessionIdMatches } from "../sessions/session-id-resolution.js";
 import {
   loadCombinedSessionStoreForGateway,
   resolveGatewaySessionStoreTarget,
@@ -74,6 +75,7 @@ export function resolveSessionKeyForTranscriptFile(sessionFile: string): string
     return cachedKey;
   }
 
+  const matchingEntries: Array<[string, SessionEntry]> = [];
   for (const [key, entry] of Object.entries(store)) {
     if (!entry?.sessionId || key === cachedKey) {
       continue;
@@ -86,8 +88,21 @@ export function resolveSessionKeyForTranscriptFile(sessionFile: string): string
         targetPath,
       })
     ) {
-      TRANSCRIPT_SESSION_KEY_CACHE.set(targetPath, key);
-      return key;
+      matchingEntries.push([key, entry]);
+    }
+  }
+
+  if (matchingEntries.length > 0) {
+    const firstSessionId = matchingEntries[0]?.[1].sessionId;
+    const sameSessionMatches = matchingEntries.filter(
+      (entry): entry is [string, SessionEntry] => entry[1].sessionId === firstSessionId,
+    );
+    const resolvedKey =
+      resolvePreferredSessionKeyForSessionIdMatches(sameSessionMatches, firstSessionId) ??
+      matchingEntries[0]?.[0];
+    if (resolvedKey) {
+      TRANSCRIPT_SESSION_KEY_CACHE.set(targetPath, resolvedKey);
+      return resolvedKey;
     }
   }