@@ -25,11 +25,14 @@ export function requestID(message: MessageV2.WithParts): string | undefined {
   return String(original?.metadata?.learnOriginalMessage ?? message.info.id)
 }
 
-/** The request of the newest message that carries one. */
+/** The request of the newest message that carries one. Newest by id, not by position, like `MessageV2.latest`:
+ * ids are chronological, and the loop's history is not in id order after a compaction that keeps a tail
+ * (`filterCompacted` places the summary after the retained tail). */
 export function latestRequestID(messages: MessageV2.WithParts[]): string | undefined {
-  for (let i = messages.length - 1; i >= 0; i--) {
-    const id = requestID(messages[i])
-    if (id !== undefined) return id
+  let newest: { id: string; request: string } | undefined
+  for (const message of messages) {
+    const request = requestID(message)
+    if (request !== undefined && (!newest || message.info.id > newest.id)) newest = { id: message.info.id, request }
   }
-  return undefined
+  return newest?.request
 }
@@ -76,6 +76,13 @@ describe("latestRequestID", () => {
     expect(latestRequestID(history)).toBe(queued.info.id)
   })
 
+  test("is the newest by id, not by position: a compaction that keeps a tail reorders history", () => {
+    const retained = message("user", [text("first")])
+    const queued = message("user", [text("sent during compaction")])
+    // `filterCompacted` places the summary after the retained tail, so the older request comes last.
+    expect(latestRequestID([queued, message("assistant", [text("summary")]), retained])).toBe(queued.info.id)
+  })
+
   test("is undefined when no message carries one", () => {
     expect(latestRequestID([message("user", [{ type: "compaction", auto: true }])])).toBeUndefined()
     expect(latestRequestID([])).toBeUndefined()
 
@@ -71,6 +71,18 @@ describe("workspace turn boundary", () => {
     expect(catalogs([a], h2)).toEqual([true, true])
   })
 
+  test("runs for a message queued during a compaction that keeps a tail, which reorders history", () => {
+    // The trace from review: request A is catalogued; compaction starts and keeps A as its tail; B
+    // is queued after the marker, before the summary is saved; compaction writes its continuation.
+    // `filterCompacted` returns [marker, B, summary, A, continuation]: A last by position, B newest by id.
+    const a = asked("first")
+    const m = marker()
+    const b = asked("sent during compaction")
+    const summary = reply()
+    const continuation = loopWrote("Continue if you have next steps")
+    expect(catalogs([a], [m, b, summary, a, continuation])).toEqual([true, true])
+  })
+
   test("does not run again for a stamped replay of an earlier request", () => {
     const a = asked("first")
     const b = asked("second")
Original file line number	Diff line number	Diff line change
`@@ -25,11 +25,14 @@ export function requestID(message: MessageV2.WithParts): string \| undefined {`
`25`	`25`	`return String(original?.metadata?.learnOriginalMessage ?? message.info.id)`
`26`	`26`	`}`
`27`	`27`
`28`		`-/** The request of the newest message that carries one. */`
	`28`	+/** The request of the newest message that carries one. Newest by id, not by position, like `MessageV2.latest`:
	`29`	`+ * ids are chronological, and the loop's history is not in id order after a compaction that keeps a tail`
	`30`	+ * (`filterCompacted` places the summary after the retained tail). */
`29`	`31`	`export function latestRequestID(messages: MessageV2.WithParts[]): string \| undefined {`
`30`		`- for (let i = messages.length - 1; i >= 0; i--) {`
`31`		`- const id = requestID(messages[i])`
`32`		`- if (id !== undefined) return id`
	`32`	`+ let newest: { id: string; request: string } \| undefined`
	`33`	`+ for (const message of messages) {`
	`34`	`+ const request = requestID(message)`
	`35`	`+ if (request !== undefined && (!newest \|\| message.info.id > newest.id)) newest = { id: message.info.id, request }`
`33`	`36`	`}`
`34`		`- return undefined`
	`37`	`+ return newest?.request`
`35`	`38`	`}`