diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 94756279d..e7aef8031 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -4,7 +4,7 @@
 
 ### Fixed
 
-- Fixed plan approval applying the wrong execution model when the model-tier slider sat on the model that exit would restore. The match check now compares the selected role's effective thinking level against the pre-plan thinking level, so picking the active planning tier is retained and picking a same-model tier with an explicit thinking suffix (e.g. `default = sonnet:off` while plan-mode raised thinking to `high`) goes through `applyRoleModel` instead of silently restoring the pre-plan level. ([#3554](https://github.com/can1357/oh-my-pi/issues/3554))
+- Fixed plan approval applying the wrong execution model when the model-tier slider sat on the model that exit would restore. The match check now compares the selected role's effective thinking level against the pre-plan thinking level, and a singleton cycle (only `modelRoles.plan` configured, default unset, so `getRoleModelCycle` synthesizes a lone `default` entry from the active plan model and the slider stays hidden) is no longer pinned as the execution tier — approval falls through to the pre-plan restore instead of silently switching back to the plan model. ([#3554](https://github.com/can1357/oh-my-pi/issues/3554))
 
 - Fixed the `eval` Julia kernel showing only runner-internal backtrace frames (`at top-level scope (./none:N)`, `at main (…runner-…jl:635)`) with no exception type or message, making cell errors undebuggable. The host renderer (`packages/coding-agent/src/eval/kernel-base.ts`) displays a non-empty `traceback` verbatim and only falls back to `ename: evalue` when it is empty; the Python and Ruby runners embed the rendered error in `traceback`, but the Julia runner (`packages/coding-agent/src/eval/jl/runner.jl`) built `traceback` from stack frames only, so the message was dropped. `emit_error` now seeds `traceback` with the `showerror` output (matching the REPL's `ERROR:` text) ahead of the frames.
 
diff --git a/packages/coding-agent/src/modes/interactive-mode.ts b/packages/coding-agent/src/modes/interactive-mode.ts
index 4ed306b44..440324795 100644
--- a/packages/coding-agent/src/modes/interactive-mode.ts
+++ b/packages/coding-agent/src/modes/interactive-mode.ts
@@ -3022,6 +3022,13 @@ export class InteractiveMode implements InteractiveModeContext {
 				// applies it AFTER #exitPlanMode. #exitPlanMode normally restores
 				// #planModePreviousModelState (the model from before plan mode), so
 				// applying the slider choice any earlier would be silently reverted.
+				// Pass executionModel only when the slider was actually shown — a
+				// singleton cycle (e.g. only modelRoles.plan is configured, so
+				// getRoleModelCycle synthesizes a lone `default` entry from the
+				// currently active plan model) hides the slider, the operator made
+				// no selection, and the pre-plan model is not in the cycle. Pinning
+				// that singleton would silently switch the session back to the plan
+				// model after #exitPlanMode restored the pre-plan model.
 				// Treat the choice as implicit only when applying the selected role
 				// would land on the same end state as the restore — same model AND
 				// the same effective thinking level. A role with an explicit thinking
@@ -3038,7 +3045,7 @@ export class InteractiveMode implements InteractiveModeContext {
 							})
 						: -1;
 				const executionModel =
-					cycle && selectedTierIndex !== restoredIndex ? cycle.models[selectedTierIndex] : undefined;
+					slider && cycle && selectedTierIndex !== restoredIndex ? cycle.models[selectedTierIndex] : undefined;
 				await this.#approvePlan(latestPlanContent, {
 					planFilePath,
 					title: details.title,
diff --git a/packages/coding-agent/test/interactive-mode-plan-review.test.ts b/packages/coding-agent/test/interactive-mode-plan-review.test.ts
index 55e0bc2e3..428e596e3 100644
--- a/packages/coding-agent/test/interactive-mode-plan-review.test.ts
+++ b/packages/coding-agent/test/interactive-mode-plan-review.test.ts
@@ -835,6 +835,46 @@ describe("InteractiveMode plan review rendering", () => {
 		expect(defaultApply?.[0]?.explicitThinkingLevel).toBe(true);
 	});
 
+	it("falls back to the pre-plan model when only plan is configured and the slider is hidden", async () => {
+		const sonnet = session.modelRegistry.find("anthropic", "claude-sonnet-4-5");
+		const opus = session.modelRegistry.find("anthropic", "claude-opus-4-5");
+		if (!sonnet || !opus) throw new Error("Expected sonnet + opus to exist in registry");
+		expect(session.model?.id).toBe(sonnet.id);
+
+		// Only the plan role is configured. getRoleModelCycle synthesizes a
+		// singleton `default` entry from the active plan model (opus), so the
+		// slider is hidden — the operator made no selection and approval must
+		// fall through to the pre-plan sonnet restore instead of pinning the
+		// lone plan tier.
+		session.settings.setModelRole("plan", "anthropic/claude-opus-4-5");
+
+		const planFilePath = "local://PLAN.md";
+		const resolvedPlanPath = resolveLocalUrlToPath(planFilePath, {
+			getArtifactsDir: () => session.sessionManager.getArtifactsDir(),
+			getSessionId: () => session.sessionManager.getSessionId(),
+		});
+		await Bun.write(resolvedPlanPath, "# Plan\n\nNo slider, restore default.");
+
+		await mode.handlePlanModeCommand();
+		expect(session.model?.id).toBe(opus.id);
+
+		vi.spyOn(session, "getContextUsage").mockReturnValue(undefined);
+		vi.spyOn(session, "prompt").mockResolvedValue(undefined as never);
+
+		let sliderShown: HookSelectorSlider | undefined;
+		vi.spyOn(mode, "showPlanReview").mockImplementation(
+			async (_planContent, _title, _options, _dialogOptions, extra?: { slider?: HookSelectorSlider }) => {
+				sliderShown = extra?.slider;
+				return "Approve and keep context";
+			},
+		);
+
+		await mode.handlePlanApproval({ planFilePath, planExists: true, title: "PLAN" });
+
+		expect(sliderShown).toBeUndefined();
+		expect(session.model?.id).toBe(sonnet.id);
+	});
+
 	it("compaction runs on the plan model and restores the pre-plan model after success", async () => {
 		const planModel = session.modelRegistry.find("anthropic", "claude-opus-4-5");
 		const prePlanModel = session.modelRegistry.find("anthropic", "claude-sonnet-4-5");