diff --git a/packages/coding-agent/src/tools/yield.ts b/packages/coding-agent/src/tools/yield.ts
index f03b0dc7f..8b8049fc7 100644
--- a/packages/coding-agent/src/tools/yield.ts
+++ b/packages/coding-agent/src/tools/yield.ts
@@ -321,26 +321,27 @@ export class YieldTool implements AgentTool<TSchema, YieldDetails> {
 
 		const status = errorMessage !== undefined ? "aborted" : "success";
 		let schemaValidationOverridden = false;
+		// Unknown incremental labels are a hard contract mismatch with the closed caller
+		// schema. Reject before the last-turn short-circuit too: `type: ["findings"], result: {}`
+		// would otherwise be accepted as a typed last-turn incremental yield, then a sibling
+		// section's MAX_SCHEMA_RETRIES override flips schemaOverridden in finalization and the
+		// stale section rides along untouched.
+		if (status === "success" && isIncremental) {
+			const unknownLabels = this.#unknownIncrementalLabels(yieldType as string[]);
+			if (unknownLabels.length > 0) {
+				const validLabels =
+					this.#validateSection && this.#validateSection.size > 0
+						? formatYieldLabels([...this.#validateSection.keys()])
+						: "none";
+				throw new Error(
+					`Section ${formatYieldLabels(yieldType as string[])} uses unknown incremental yield label(s): ${formatYieldLabels(unknownLabels)}. Resubmit with one of the schema's labels: ${validLabels}.`,
+				);
+			}
+		}
 		if (status === "success" && !useLastTurn) {
 			if (data === null) {
 				throw new Error("data is required when yield indicates success");
 			}
-			// Unknown incremental labels are a hard contract mismatch with the closed
-			// caller schema, not a shape error a retry can fix. Reject them every time
-			// without touching the schema-retry counter so the override path never
-			// accepts a stale agent-native section name.
-			if (isIncremental) {
-				const unknownLabels = this.#unknownIncrementalLabels(yieldType as string[]);
-				if (unknownLabels.length > 0) {
-					const validLabels =
-						this.#validateSection && this.#validateSection.size > 0
-							? formatYieldLabels([...this.#validateSection.keys()])
-							: "none";
-					throw new Error(
-						`Section ${formatYieldLabels(yieldType as string[])} uses unknown incremental yield label(s): ${formatYieldLabels(unknownLabels)}. Resubmit with one of the schema's labels: ${validLabels}.`,
-					);
-				}
-			}
 			const sectionFailure = isIncremental
 				? this.#validateIncrementalSection(yieldType as string[], data)
 				: this.#validate
diff --git a/packages/coding-agent/test/tools/yield.test.ts b/packages/coding-agent/test/tools/yield.test.ts
index 6363af92b..653bf96b0 100644
--- a/packages/coding-agent/test/tools/yield.test.ts
+++ b/packages/coding-agent/test/tools/yield.test.ts
@@ -282,6 +282,19 @@ describe("YieldTool", () => {
 			);
 		}
 
+		// The last-turn short-circuit (`type: ["findings"], result: {}`) MUST also reject
+		// the unknown label. Otherwise the stale section silently accepts the last assistant
+		// text and rides along when a sibling section trips MAX_SCHEMA_RETRIES and
+		// schemaOverridden in finalization (issue #3927 follow-up review).
+		await expect(
+			tool.execute("call-native-reviewer-label-last-turn", {
+				type: ["findings"],
+				result: {},
+			} as never),
+		).rejects.toThrow(
+			/Section "findings" uses unknown incremental yield label\(s\): "findings"\. Resubmit with one of the schema's labels: "issue_key", "verdict", "blockers", "non_blocking_notes"\./,
+		);
+
 		// Schema-retry budget intact: a separate, shape-only mismatch still fires the
 		// first-attempt retry hint (`2 retry attempt(s) remain`), proving the unknown-label
 		// path didn't burn the override.