feat(agents): per-model reasoning effort level

Add a per-model/key reasoning effort setting to agent definitions,
surfaced and editable in the Agent Settings page and displayed at a
glance in the model selector views.

- core: single source of truth for effort levels (REASONING_EFFORTS,
  DEFAULT_REASONING_EFFORT='high', labels, isReasoningEffort guard);
  add 'xhigh' level; AgentModelEntry.effort; xhigh budget=24000 for
  classic-thinking Claude; default floor 'high'. Persist/parse effort
  in the agent TOML loader.
- api: thread effort through the fallback chain with per-model -> per-tab
  -> default precedence; validate /chat + agentModels effort from the
  canonical list.
- frontend: effort <select> per model row in AgentBuilder; effort badges
  in ModelSelector (agent + subagent chains); Thinking dropdown sourced
  from canonical list; per-tab default raised to 'high'.
- tests: +15 (loader round-trip, agent xhigh budget, canonical list +
  guard, api precedence, route validation).

16 files changed, 430 insertions, 53 deletions

diff --git a/packages/api/src/agent-manager.ts b/packages/api/src/agent-manager.ts
index 5a0ffdf..d03e696 100644
--- a/packages/api/src/agent-manager.ts
+++ b/packages/api/src/agent-manager.ts
@@ -1,6 +1,7 @@
 import {
 	Agent,
 	type AgentEvent,
+	type AgentModelEntry,
 	type AgentSkillMapping,
 	type AgentStatus,
 	appendChunks,
@@ -42,6 +43,7 @@ import {
 	loadSkills,
 	ModelRegistry,
 	type QueuedMessage,
+	type ReasoningEffort,
 	refreshAccountCredentials,
 	refreshAccountCredentialsAsync,
 	resolveApiKey,
@@ -172,7 +174,7 @@ interface TabAgent {
 	taskList: TaskList;
 	_lastPermKey?: string;
 	/** Ordered key+model fallback hierarchy from the agent definition. */
-	agentModels?: Array<{ key_id: string; model_id: string }>;
+	agentModels?: AgentModelEntry[];
 	/** Abort controller for cancelling a running agent. */
 	abortController?: AbortController;
 	/** For child agents: resolves when the agent finishes its task. */
@@ -1333,8 +1335,8 @@ export class AgentManager {
 		opts: {
 			keyId?: string;
 			modelId?: string;
-			agentModels?: Array<{ key_id: string; model_id: string }>;
-			reasoningEffort?: "none" | "low" | "medium" | "high" | "max";
+			agentModels?: AgentModelEntry[];
+			reasoningEffort?: ReasoningEffort;
 			workingDirectory?: string;
 			queueId?: string;
 			/**
@@ -1419,9 +1421,9 @@ export class AgentManager {
 		message: string,
 		keyId?: string,
 		modelId?: string,
-		reasoningEffort?: "none" | "low" | "medium" | "high" | "max",
+		reasoningEffort?: ReasoningEffort,
 		workingDirectory?: string,
-		agentModels?: Array<{ key_id: string; model_id: string }>,
+		agentModels?: AgentModelEntry[],
 	): Promise<void> {
 		const tabAgent = this._getOrCreateTabAgent(tabId);
 
@@ -1471,6 +1473,10 @@ export class AgentManager {
 			// to the tabAgent's stored defaults via the `?? tabAgent.keyId` chain.
 			currentKeyId = entry.key_id || undefined;
 			currentModelId = entry.model_id || undefined;
+			// Effort precedence: per-model (agent definition) → per-tab selector
+			// (the `reasoningEffort` arg) → the Agent's own DEFAULT_REASONING_EFFORT
+			// floor (applied inside `agent.run`).
+			const effortForEntry = entry.effort ?? reasoningEffort;
 			allOutput = "";
 
 			// Single ordered chunk list accumulating this attempt's assistant
@@ -1514,7 +1520,7 @@ export class AgentManager {
 				}
 
 				for await (const event of agent.run(message, {
-					...(reasoningEffort ? { reasoningEffort } : {}),
+					...(effortForEntry ? { reasoningEffort: effortForEntry } : {}),
 					abortSignal: tabAgent.abortController?.signal,
 				})) {
 					// Stop processing if the tab was aborted (closed/stopped).
@@ -1703,7 +1709,7 @@ export class AgentManager {
 		tabAgent: TabAgent,
 		keyId?: string,
 		modelId?: string,
-	): Array<{ key_id: string; model_id: string }> {
+	): AgentModelEntry[] {
 		// Agent mode: use the agent's configured fallback hierarchy in strict order
 		const models = tabAgent.agentModels;
 		if (models && models.length > 0) {
diff --git a/packages/api/src/app.ts b/packages/api/src/app.ts
index 0dabb0d..84afd2a 100644
--- a/packages/api/src/app.ts
+++ b/packages/api/src/app.ts
@@ -1,4 +1,9 @@
-import { getTab, NotificationDispatcher } from "@dispatch/core";
+import {
+	type AgentModelEntry,
+	getTab,
+	isReasoningEffort,
+	NotificationDispatcher,
+} from "@dispatch/core";
 import { Hono } from "hono";
 import { cors } from "hono/cors";
 import { AgentManager } from "./agent-manager.js";
@@ -10,6 +15,28 @@ import { notificationsRoutes } from "./routes/notifications.js";
 import { skillsRoutes } from "./routes/skills.js";
 import { tabsRoutes } from "./routes/tabs.js";
 
+/**
+ * Validate and normalise the `agentModels` fallback chain coming from the
+ * frontend. Each entry must carry string `key_id`/`model_id`; an `effort` is
+ * kept only when it's a recognised level (otherwise dropped so the per-tab /
+ * default effort applies). Returns `undefined` when the input isn't an array.
+ */
+function sanitizeAgentModels(raw: unknown): AgentModelEntry[] | undefined {
+	if (!Array.isArray(raw)) return undefined;
+	const out: AgentModelEntry[] = [];
+	for (const m of raw) {
+		if (!m || typeof m !== "object") continue;
+		const entry = m as Record<string, unknown>;
+		if (typeof entry.key_id !== "string" || typeof entry.model_id !== "string") continue;
+		out.push({
+			key_id: entry.key_id,
+			model_id: entry.model_id,
+			...(isReasoningEffort(entry.effort) ? { effort: entry.effort } : {}),
+		});
+	}
+	return out;
+}
+
 export const permissionManager = new PermissionManager();
 export const agentManager = new AgentManager(permissionManager);
 
@@ -86,15 +113,13 @@ app.post("/chat", async (c) => {
 
 	const keyId = typeof body.keyId === "string" ? body.keyId : undefined;
 	const modelId = typeof body.modelId === "string" ? body.modelId : undefined;
-	const agentModels = Array.isArray(body.agentModels) ? body.agentModels : undefined;
+	const agentModels = sanitizeAgentModels(body.agentModels);
 	const workingDirectory =
 		typeof body.workingDirectory === "string" ? body.workingDirectory : undefined;
 	const queueId = typeof body.queueId === "string" ? body.queueId : undefined;
-	const validEfforts = ["none", "low", "medium", "high", "max"];
-	const reasoningEffort =
-		typeof body.reasoningEffort === "string" && validEfforts.includes(body.reasoningEffort)
-			? (body.reasoningEffort as "none" | "low" | "medium" | "high" | "max")
-			: undefined;
+	const reasoningEffort = isReasoningEffort(body.reasoningEffort)
+		? body.reasoningEffort
+		: undefined;
 
 	// Single routing decision (queue if busy, new turn if idle) shared with the
 	// `send_to_tab` tool via `AgentManager.deliverMessage`. Non-blocking — a
diff --git a/packages/api/src/routes/agents.ts b/packages/api/src/routes/agents.ts
index 1627674..10ca714 100644
--- a/packages/api/src/routes/agents.ts
+++ b/packages/api/src/routes/agents.ts
@@ -2,7 +2,13 @@ import * as fs from "node:fs";
 import * as os from "node:os";
 import * as path from "node:path";
 import type { AgentDefinition } from "@dispatch/core";
-import { deleteAgent, getAgentDirs, loadAgents, saveAgent } from "@dispatch/core";
+import {
+	deleteAgent,
+	getAgentDirs,
+	isReasoningEffort,
+	loadAgents,
+	saveAgent,
+} from "@dispatch/core";
 import { Hono } from "hono";
 
 const SAFE_SLUG_RE = /^[a-zA-Z0-9_-]+$/;
@@ -52,7 +58,12 @@ agentsRoutes.post("/", async (c) => {
 			description: body.description || "",
 			skills: body.skills || [],
 			tools: body.tools || [],
-			models: body.models || [],
+			models: (body.models || []).map((m) => ({
+				key_id: m.key_id,
+				model_id: m.model_id,
+				// Keep `effort` only when it's a recognised level; drop anything else.
+				...(isReasoningEffort(m.effort) ? { effort: m.effort } : {}),
+			})),
 			scope: body.scope,
 			slug: body.slug,
 			...(body.cwd ? { cwd: body.cwd } : {}),
diff --git a/packages/api/tests/agent-manager.test.ts b/packages/api/tests/agent-manager.test.ts
index b9b4510..ffd87b5 100644
--- a/packages/api/tests/agent-manager.test.ts
+++ b/packages/api/tests/agent-manager.test.ts
@@ -80,6 +80,13 @@ function resetConstructedAgents(): void {
 	constructedAgents.length = 0;
 }
 
+// Capture the per-call `run()` options (notably reasoningEffort) so tests can
+// assert the per-model → per-tab → default effort resolution.
+const capturedRunOptions: Array<{ reasoningEffort?: string } | undefined> = [];
+function resetCapturedRunOptions(): void {
+	capturedRunOptions.length = 0;
+}
+
 // Configurable settings store so tests can toggle tool permissions
 // (perm_send_to_tab / perm_read_tab / ...) and assert which tools the
 // constructed Agent receives. Defaults to empty (getSetting → null).
@@ -135,7 +142,7 @@ vi.mock("@dispatch/core", () => ({
 		constructor(config: { tools?: Array<{ name: string }> }) {
 			this.toolNames = (config?.tools ?? []).map((t) => t.name);
 		}
-		async *run(message: string): AsyncGenerator<unknown> {
+		async *run(message: string, options?: { reasoningEffort?: string }): AsyncGenerator<unknown> {
 			// Snapshot the post-construction pre-populated message list
 			// the first thing `run()` does, before the real `Agent.run`
 			// would push the current user message at line 546. Tests
@@ -144,6 +151,7 @@ vi.mock("@dispatch/core", () => ({
 				initialMessages: [...this.messages],
 				toolNames: [...this.toolNames],
 			});
+			capturedRunOptions.push(options);
 			if (runImpl) {
 				for await (const ev of runImpl(message)) yield ev;
 				return;
@@ -345,6 +353,11 @@ vi.mock("@dispatch/core", () => ({
 	getSetting(key: string) {
 		return fakeSettings.get(key) ?? null;
 	},
+	isReasoningEffort(value: unknown) {
+		return (
+			typeof value === "string" && ["none", "low", "medium", "high", "xhigh", "max"].includes(value)
+		);
+	},
 	appendChunks() {
 		return [];
 	},
@@ -402,6 +415,7 @@ describe("AgentManager", () => {
 	beforeEach(() => {
 		resetFakeMessages();
 		resetConstructedAgents();
+		resetCapturedRunOptions();
 		resetFakeTabs();
 		resetFakeSettings();
 		setRunImpl(null);
@@ -519,6 +533,54 @@ describe("AgentManager", () => {
 		expect(listener2).toHaveBeenCalled();
 	});
 
+	// ─── per-model reasoning effort precedence ───────────────────────
+
+	describe("reasoning effort precedence (per-model → per-tab → default)", () => {
+		it("uses the per-model effort over the per-tab selector for that fallback entry", async () => {
+			const manager = new AgentManager();
+			// Agent definition supplies a fallback chain where each entry has its
+			// own configured effort; the per-tab selector ("low") must NOT win.
+			await manager.processMessage(
+				"tab-effort-permodel",
+				"go",
+				"key-a",
+				"model-a",
+				"low",
+				undefined,
+				[{ key_id: "key-a", model_id: "model-a", effort: "xhigh" }],
+			);
+			expect(capturedRunOptions.at(-1)?.reasoningEffort).toBe("xhigh");
+		});
+
+		it("falls back to the per-tab selector when the model entry has no effort", async () => {
+			const manager = new AgentManager();
+			await manager.processMessage(
+				"tab-effort-tab",
+				"go",
+				"key-a",
+				"model-a",
+				"medium",
+				undefined,
+				[{ key_id: "key-a", model_id: "model-a" }],
+			);
+			expect(capturedRunOptions.at(-1)?.reasoningEffort).toBe("medium");
+		});
+
+		it("passes no effort (Agent applies its default) when neither is set", async () => {
+			const manager = new AgentManager();
+			await manager.processMessage(
+				"tab-effort-default",
+				"go",
+				"key-a",
+				"model-a",
+				undefined,
+				undefined,
+				[{ key_id: "key-a", model_id: "model-a" }],
+			);
+			expect(capturedRunOptions.at(-1)?.reasoningEffort).toBeUndefined();
+		});
+	});
+
 	// ─── v6 reasoning-end tests ───────────────────────────────────────
 
 	it("reasoning-end event is broadcast to WS listeners", async () => {
diff --git a/packages/api/tests/routes.test.ts b/packages/api/tests/routes.test.ts
index c768cee..3bf446d 100644
--- a/packages/api/tests/routes.test.ts
+++ b/packages/api/tests/routes.test.ts
@@ -169,6 +169,11 @@ vi.mock("@dispatch/core", () => ({
 	getTab() {
 		return null;
 	},
+	isReasoningEffort(value: unknown) {
+		return (
+			typeof value === "string" && ["none", "low", "medium", "high", "xhigh", "max"].includes(value)
+		);
+	},
 	listOpenTabs() {
 		return [];
 	},
@@ -353,6 +358,34 @@ describe("POST /chat", () => {
 		expect(body).toEqual({ status: "ok" });
 	});
 
+	it("accepts xhigh as a valid reasoningEffort", async () => {
+		const res = await app.request("/chat", {
+			method: "POST",
+			headers: { "Content-Type": "application/json" },
+			body: JSON.stringify({
+				tabId: "tab-xhigh",
+				message: "hello",
+				reasoningEffort: "xhigh",
+			}),
+		});
+		expect(res.status).toBe(200);
+		expect(await res.json()).toEqual({ status: "ok" });
+	});
+
+	it("tolerates an invalid agentModels effort (sanitized, not rejected)", async () => {
+		const res = await app.request("/chat", {
+			method: "POST",
+			headers: { "Content-Type": "application/json" },
+			body: JSON.stringify({
+				tabId: "tab-badeffort",
+				message: "hello",
+				agentModels: [{ key_id: "k", model_id: "m", effort: "turbo" }],
+			}),
+		});
+		expect(res.status).toBe(200);
+		expect(await res.json()).toEqual({ status: "ok" });
+	});
+
 	it("returns 400 with empty message", async () => {
 		const res = await app.request("/chat", {
 			method: "POST",
diff --git a/packages/core/src/agent/agent.ts b/packages/core/src/agent/agent.ts
index c6f1322..4bfa7eb 100644
--- a/packages/core/src/agent/agent.ts
+++ b/packages/core/src/agent/agent.ts
diff --git a/packages/core/src/agents/loader.ts b/packages/core/src/agents/loader.ts
index f4a6c5a..9971803 100644
--- a/packages/core/src/agents/loader.ts
+++ b/packages/core/src/agents/loader.ts
@@ -2,7 +2,7 @@ import * as fs from "node:fs";
 import * as os from "node:os";
 import * as path from "node:path";
 import { parse as parseTOML, stringify as stringifyTOML } from "smol-toml";
-import type { AgentDefinition, AgentModelEntry } from "../types/index.js";
+import { type AgentDefinition, type AgentModelEntry, isReasoningEffort } from "../types/index.js";
 
 // ─── Helpers ─────────────────────────────────────────────────────
 
@@ -192,6 +192,7 @@ export function saveAgent(agent: AgentDefinition): void {
 		tomlContent.models = agent.models.map((m) => ({
 			key_id: m.key_id,
 			model_id: m.model_id,
+			...(m.effort ? { effort: m.effort } : {}),
 		}));
 	}
 
@@ -246,9 +247,14 @@ function loadAgentsFromDir(dir: string, scope: string): AgentDefinition[] {
 			if (Array.isArray(parsed.models)) {
 				for (const m of parsed.models) {
 					if (m && typeof m === "object" && "key_id" in m && "model_id" in m) {
+						const rawEffort = (m as Record<string, unknown>).effort;
 						models.push({
 							key_id: String((m as Record<string, unknown>).key_id),
 							model_id: String((m as Record<string, unknown>).model_id),
+							// Only carry `effort` when it's a recognised level; an
+							// unset or invalid value falls back to the per-tab /
+							// default effort at the call site.
+							...(isReasoningEffort(rawEffort) ? { effort: rawEffort } : {}),
 						});
 					}
 				}
diff --git a/packages/core/src/types/index.ts b/packages/core/src/types/index.ts
index ced3dc2..bab17f1 100644
--- a/packages/core/src/types/index.ts
+++ b/packages/core/src/types/index.ts
@@ -308,7 +308,43 @@ export interface ToolDefinition {
 
 // ─── Agent Configuration ─────────────────────────────────────────
 
-export type ReasoningEffort = "none" | "low" | "medium" | "high" | "max";
+/**
+ * Canonical, ordered list of reasoning-effort levels — the SINGLE SOURCE OF
+ * TRUTH for effort values across the whole codebase (core LLM call site, API
+ * validation, agent TOML persistence, and the frontend UI). Ordered from least
+ * to most effort.
+ *
+ * `none` disables reasoning. `low`/`medium`/`high`/`xhigh` are forwarded
+ * verbatim to providers that accept them (OpenAI-compatible `reasoning_effort`,
+ * Anthropic adaptive `effort`) — `xhigh` is accepted by newer OpenAI reasoning
+ * models. `max` is Dispatch's own top tier, mapped per-provider at the call
+ * site (e.g. classic-thinking Claude budget tokens).
+ */
+export const REASONING_EFFORTS = ["none", "low", "medium", "high", "xhigh", "max"] as const;
+
+export type ReasoningEffort = (typeof REASONING_EFFORTS)[number];
+
+/**
+ * Default effort applied when nothing more specific is configured (no per-model
+ * effort and no per-tab selection). Resolution order is
+ * per-model → per-tab → this default.
+ */
+export const DEFAULT_REASONING_EFFORT: ReasoningEffort = "high";
+
+/** Human-readable labels for each effort level (UI display). */
+export const REASONING_EFFORT_LABELS: Record<ReasoningEffort, string> = {
+	none: "Off",
+	low: "Low",
+	medium: "Medium",
+	high: "High",
+	xhigh: "X-High",
+	max: "Max",
+};
+
+/** Runtime type guard for narrowing an arbitrary value to a `ReasoningEffort`. */
+export function isReasoningEffort(value: unknown): value is ReasoningEffort {
+	return typeof value === "string" && (REASONING_EFFORTS as readonly string[]).includes(value);
+}
 
 export interface AgentConfig {
 	model: string;
@@ -416,6 +452,12 @@ export interface QueueCallbacks {
 export interface AgentModelEntry {
 	key_id: string;
 	model_id: string;
+	/**
+	 * Per-model/key reasoning effort. When set, overrides the per-tab effort
+	 * selector for generations that use this entry (resolution order:
+	 * per-model → per-tab → DEFAULT_REASONING_EFFORT). Omitted when unset.
+	 */
+	effort?: ReasoningEffort;
 }
 
 export interface AgentDefinition {
diff --git a/packages/core/tests/agent/agent.test.ts b/packages/core/tests/agent/agent.test.ts
index 188129c..d8edec7 100644
--- a/packages/core/tests/agent/agent.test.ts
+++ b/packages/core/tests/agent/agent.test.ts
@@ -1514,7 +1514,7 @@ describe("anthropicThinkingProviderOptions — adaptive-thinking model detection
 	});
 
 	it("maps reasoning effort → budgetTokens for enabled (non-adaptive) models", () => {
-		const budget = (e: "low" | "medium" | "high" | "max") => {
+		const budget = (e: "low" | "medium" | "high" | "xhigh" | "max") => {
 			const opts = anthropicThinkingProviderOptions("claude-3-7-sonnet", e) as {
 				thinking: { type: "enabled"; budgetTokens: number };
 			};
@@ -1523,6 +1523,25 @@ describe("anthropicThinkingProviderOptions — adaptive-thinking model detection
 		expect(budget("low")).toBe(2000);
 		expect(budget("medium")).toBe(5000);
 		expect(budget("high")).toBe(16000);
+		expect(budget("xhigh")).toBe(24000);
 		expect(budget("max")).toBe(31999);
 	});
+
+	it("xhigh budget sits strictly between high and max (ordering invariant)", () => {
+		const budget = (e: "high" | "xhigh" | "max") => {
+			const opts = anthropicThinkingProviderOptions("claude-3-7-sonnet", e) as {
+				thinking: { type: "enabled"; budgetTokens: number };
+			};
+			return opts.thinking.budgetTokens;
+		};
+		expect(budget("high")).toBeLessThan(budget("xhigh"));
+		expect(budget("xhigh")).toBeLessThan(budget("max"));
+	});
+
+	it("forwards xhigh verbatim as the adaptive effort sibling (Opus 4.7+)", () => {
+		expect(anthropicThinkingProviderOptions("claude-opus-4-8", "xhigh")).toEqual({
+			thinking: { type: "adaptive", display: "summarized" },
+			effort: "xhigh",
+		});
+	});
 });
diff --git a/packages/core/tests/agents/loader.test.ts b/packages/core/tests/agents/loader.test.ts
index 35ab0cf..92f9877 100644
--- a/packages/core/tests/agents/loader.test.ts
+++ b/packages/core/tests/agents/loader.test.ts
@@ -2,7 +2,12 @@ import * as fs from "node:fs";
 import * as os from "node:os";
 import * as path from "node:path";
 import { afterEach, beforeEach, describe, expect, it } from "vitest";
-import { expandAgentToolNames, getAgentDirPaths, loadAgent } from "../../src/agents/loader.js";
+import {
+	expandAgentToolNames,
+	getAgentDirPaths,
+	loadAgent,
+	saveAgent,
+} from "../../src/agents/loader.js";
 
 describe("expandAgentToolNames", () => {
 	it("expands 'read' into the granular read tools", () => {
@@ -145,6 +150,76 @@ describe("loadAgent — project-scoped sandbox", () => {
 		expect(agent?.scope).toBe(tmpProject);
 	});
 
+	it("parses a per-model effort when it is a recognised level", () => {
+		writeAgentToml(
+			TEST_SLUG,
+			[
+				'name = "Fixture"',
+				"skills = []",
+				'tools = ["read"]',
+				"",
+				"[[models]]",
+				'key_id = "opencode-1"',
+				'model_id = "deepseek-v4-flash"',
+				'effort = "low"',
+				"",
+				"[[models]]",
+				'key_id = "claude-max"',
+				'model_id = "claude-opus-4-8"',
+				'effort = "xhigh"',
+				"",
+			].join("\n"),
+		);
+
+		const agent = loadAgent(TEST_SLUG, tmpProject);
+		expect(agent?.models).toEqual([
+			{ key_id: "opencode-1", model_id: "deepseek-v4-flash", effort: "low" },
+			{ key_id: "claude-max", model_id: "claude-opus-4-8", effort: "xhigh" },
+		]);
+	});
+
+	it("drops an invalid effort value so the call site falls back to the default", () => {
+		writeAgentToml(
+			TEST_SLUG,
+			[
+				'name = "Fixture"',
+				"skills = []",
+				'tools = ["read"]',
+				"",
+				"[[models]]",
+				'key_id = "opencode-1"',
+				'model_id = "deepseek-v4-flash"',
+				'effort = "turbo"',
+				"",
+			].join("\n"),
+		);
+
+		const agent = loadAgent(TEST_SLUG, tmpProject);
+		expect(agent?.models).toEqual([{ key_id: "opencode-1", model_id: "deepseek-v4-flash" }]);
+		expect(agent?.models[0]).not.toHaveProperty("effort");
+	});
+
+	it("round-trips effort through saveAgent → loadAgent", () => {
+		saveAgent({
+			name: "Fixture",
+			description: "",
+			skills: [],
+			tools: ["read"],
+			models: [
+				{ key_id: "opencode-1", model_id: "deepseek-v4-flash", effort: "medium" },
+				{ key_id: "claude-max", model_id: "claude-opus-4-8" },
+			],
+			scope: tmpProject,
+			slug: TEST_SLUG,
+		});
+
+		const agent = loadAgent(TEST_SLUG, tmpProject);
+		expect(agent?.models).toEqual([
+			{ key_id: "opencode-1", model_id: "deepseek-v4-flash", effort: "medium" },
+			{ key_id: "claude-max", model_id: "claude-opus-4-8" },
+		]);
+	});
+
 	it("sanitizes the slug so path traversal can't reach outside the agents dir", () => {
 		// Even if a caller passes something gnarly, the lookup is by
 		// sanitized slug — no file outside the configured dirs should
diff --git a/packages/core/tests/types/reasoning-effort.test.ts b/packages/core/tests/types/reasoning-effort.test.ts
new file mode 100644
index 0000000..97cd26c
--- /dev/null
+++ b/packages/core/tests/types/reasoning-effort.test.ts
@@ -0,0 +1,48 @@
+import { describe, expect, it } from "vitest";
+import {
+	DEFAULT_REASONING_EFFORT,
+	isReasoningEffort,
+	REASONING_EFFORT_LABELS,
+	REASONING_EFFORTS,
+} from "../../src/types/index.js";
+
+describe("REASONING_EFFORTS — canonical effort list (single source of truth)", () => {
+	it("is ordered least→most and includes xhigh between high and max", () => {
+		expect(REASONING_EFFORTS).toEqual(["none", "low", "medium", "high", "xhigh", "max"]);
+		const hi = REASONING_EFFORTS.indexOf("high");
+		const xhi = REASONING_EFFORTS.indexOf("xhigh");
+		const mx = REASONING_EFFORTS.indexOf("max");
+		expect(hi).toBeLessThan(xhi);
+		expect(xhi).toBeLessThan(mx);
+	});
+
+	it("has a human-readable label for every level (no gaps)", () => {
+		for (const effort of REASONING_EFFORTS) {
+			expect(REASONING_EFFORT_LABELS[effort]).toBeTruthy();
+		}
+		expect(Object.keys(REASONING_EFFORT_LABELS).sort()).toEqual([...REASONING_EFFORTS].sort());
+	});
+
+	it("defaults to high", () => {
+		expect(DEFAULT_REASONING_EFFORT).toBe("high");
+		expect(REASONING_EFFORTS).toContain(DEFAULT_REASONING_EFFORT);
+	});
+});
+
+describe("isReasoningEffort", () => {
+	it("accepts every canonical level", () => {
+		for (const effort of REASONING_EFFORTS) {
+			expect(isReasoningEffort(effort)).toBe(true);
+		}
+	});
+
+	it("rejects unknown strings and non-strings", () => {
+		expect(isReasoningEffort("turbo")).toBe(false);
+		expect(isReasoningEffort("HIGH")).toBe(false);
+		expect(isReasoningEffort("")).toBe(false);
+		expect(isReasoningEffort(undefined)).toBe(false);
+		expect(isReasoningEffort(null)).toBe(false);
+		expect(isReasoningEffort(3)).toBe(false);
+		expect(isReasoningEffort({})).toBe(false);
+	});
+});
diff --git a/packages/frontend/src/App.svelte b/packages/frontend/src/App.svelte
index eaa28e8..3f1c500 100644
--- a/packages/frontend/src/App.svelte
+++ b/packages/frontend/src/App.svelte
@@ -1,4 +1,5 @@
 <script lang="ts">
+import { DEFAULT_REASONING_EFFORT } from "@dispatch/core/src/types/index.js";
 import { onMount } from "svelte";
 import AgentBuilder from "./lib/components/AgentBuilder.svelte";
 import ChatInput from "./lib/components/ChatInput.svelte";
@@ -141,20 +142,14 @@ onMount(() => {
 				apiBase={config.apiBase}
 				activeKeyId={tabStore.activeTab?.keyId ?? null}
 				activeModelId={tabStore.activeTab?.modelId ?? null}
-				reasoningEffort={tabStore.activeTab?.reasoningEffort ?? "max"}
+				reasoningEffort={tabStore.activeTab?.reasoningEffort ?? DEFAULT_REASONING_EFFORT}
 				activeAgentSlug={tabStore.activeTab?.agentSlug ?? null}
 				activeTabParentId={tabStore.activeTab?.parentTabId ?? null}
 				activeAgentModels={tabStore.activeTab?.agentModels ?? null}
 				workingDirectory={tabStore.activeTab?.workingDirectory ?? null}
 				onKeyChange={(keyId) => tabStore.setKey(keyId)}
 				onModelChange={(keyId, modelId) => tabStore.changeModel(keyId, modelId)}
-				onReasoningChange={(effort) => {
-					const tab = tabStore.activeTab;
-					if (tab) {
-						// Update reasoning effort for active tab
-						tabStore.tabs.find(t => t.id === tab.id)!.reasoningEffort = effort;
-					}
-				}}
+				onReasoningChange={(effort) => tabStore.setReasoningEffort(effort)}
 				onAgentChange={(agent) => tabStore.setAgent(agent)}
 				onWorkingDirectoryChange={(dir) => tabStore.setWorkingDirectory(dir)}
 			onAddKey={() => { showAddKeyModal = true; addKeyId = ""; addKeyProvider = "anthropic"; addKeyError = null; }}
diff --git a/packages/frontend/src/lib/components/AgentBuilder.svelte b/packages/frontend/src/lib/components/AgentBuilder.svelte
index d8ae530..bbdb83c 100644
--- a/packages/frontend/src/lib/components/AgentBuilder.svelte
+++ b/packages/frontend/src/lib/components/AgentBuilder.svelte
@@ -4,6 +4,11 @@ const modelCache = new Map();
 </script>
 
 <script lang="ts">
+	import {
+		DEFAULT_REASONING_EFFORT,
+		REASONING_EFFORTS,
+		REASONING_EFFORT_LABELS,
+	} from "@dispatch/core/src/types/index.js";
 	import { config } from "../config.js";
 	import { router } from "../router.svelte.js";
 	import type { KeyInfo } from "../types.js";
@@ -13,6 +18,7 @@ const modelCache = new Map();
 	interface AgentModelEntry {
 		key_id: string;
 		model_id: string;
+		effort?: string;
 	}
 
 	interface AgentDefinition {
@@ -173,6 +179,10 @@ const modelCache = new Map();
 		formModels = formModels.filter((_, idx) => idx !== i);
 	}
 
+	function setEffortEntry(i: number, effort: string) {
+		formModels = formModels.map((m, idx) => (idx === i ? { ...m, effort } : m));
+	}
+
 	async function openKeyModal(i: number) {
 		modelModalIndex = i;
 		modelModalType = "key";
@@ -546,6 +556,16 @@ const modelCache = new Map();
 								>
 									{entry.model_id || "Select Model"}
 								</button>
+								<select
+									class="select select-bordered select-sm shrink-0 w-28"
+									title="Reasoning effort for this model"
+									value={entry.effort ?? DEFAULT_REASONING_EFFORT}
+									onchange={(e) => setEffortEntry(i, e.currentTarget.value)}
+								>
+									{#each REASONING_EFFORTS as effort}
+										<option value={effort}>{REASONING_EFFORT_LABELS[effort]}</option>
+									{/each}
+								</select>
 								<button
 									type="button"
 									class="btn btn-sm btn-ghost text-error"
diff --git a/packages/frontend/src/lib/components/ModelSelector.svelte b/packages/frontend/src/lib/components/ModelSelector.svelte
index a752f5d..c328511 100644
--- a/packages/frontend/src/lib/components/ModelSelector.svelte
+++ b/packages/frontend/src/lib/components/ModelSelector.svelte
@@ -3,6 +3,12 @@ const modelCache = new Map<string, string[]>();
 </script>
 
 <script lang="ts">
+	import {
+		DEFAULT_REASONING_EFFORT,
+		isReasoningEffort,
+		REASONING_EFFORTS,
+		REASONING_EFFORT_LABELS,
+	} from "@dispatch/core/src/types/index.js";
 	import type { KeyInfo } from "../types.js";
 	import { config } from "../config.js";
 	import { router } from "../router.svelte.js";
@@ -14,7 +20,7 @@ const modelCache = new Map<string, string[]>();
 		description: string;
 		skills: string[];
 		tools: string[];
-		models: Array<{ key_id: string; model_id: string }>;
+		models: Array<{ key_id: string; model_id: string; effort?: string }>;
 		cwd?: string;
 		is_subagent?: boolean;
 	}
@@ -30,6 +36,15 @@ const modelCache = new Map<string, string[]>();
 		};
 	}
 
+	/**
+	 * Human-readable effort label for a (possibly-unset / arbitrary) effort
+	 * string. Falls back to the default level's label when unset/invalid so the
+	 * displayed badge always reflects what will actually be used.
+	 */
+	function effortLabel(effort: string | undefined): string {
+		return REASONING_EFFORT_LABELS[isReasoningEffort(effort) ? effort : DEFAULT_REASONING_EFFORT];
+	}
+
 	const {
 		keys = [],
 		activeKeyId = null,
@@ -37,7 +52,7 @@ const modelCache = new Map<string, string[]>();
 		reasoningEffort = "max",
 		activeAgentSlug = null,
 		activeTabParentId = null as string | null,
-		activeAgentModels = null as Array<{ key_id: string; model_id: string }> | null,
+		activeAgentModels = null as Array<{ key_id: string; model_id: string; effort?: string }> | null,
 		workingDirectory = null,
 		onKeyChange,
 		onModelChange,
@@ -51,7 +66,7 @@ const modelCache = new Map<string, string[]>();
 		reasoningEffort?: string;
 		activeAgentSlug?: string | null;
 		activeTabParentId?: string | null;
-		activeAgentModels?: Array<{ key_id: string; model_id: string }> | null;
+		activeAgentModels?: Array<{ key_id: string; model_id: string; effort?: string }> | null;
 		workingDirectory?: string | null;
 		onKeyChange: (keyId: string) => void;
 		onModelChange: (keyId: string, modelId: string) => void;
@@ -264,11 +279,9 @@ const modelCache = new Map<string, string[]>();
 					value={reasoningEffort}
 					onchange={(e) => onReasoningChange(e.currentTarget.value)}
 				>
-					<option value="none">Off</option>
-					<option value="low">Low</option>
-					<option value="medium">Medium</option>
-					<option value="high">High</option>
-					<option value="max">Max</option>
+					{#each REASONING_EFFORTS as effort}
+						<option value={effort}>{REASONING_EFFORT_LABELS[effort]}</option>
+					{/each}
 				</select>
 			</div>
 		{/if}
@@ -312,8 +325,9 @@ const modelCache = new Map<string, string[]>();
 					</div>
 					<div class="mt-1 flex flex-col gap-0.5">
 						{#each subModels as m, i}
-							<div class="text-xs font-mono truncate {i === displayIdx ? 'opacity-100 font-semibold' : 'opacity-50'}">
-								{i + 1}. {m.key_id} / {m.model_id}
+							<div class="text-xs font-mono truncate flex items-center gap-1 {i === displayIdx ? 'opacity-100 font-semibold' : 'opacity-50'}">
+								<span class="truncate">{i + 1}. {m.key_id} / {m.model_id}</span>
+								<span class="badge badge-xs badge-ghost shrink-0">{effortLabel(m.effort)}</span>
 							</div>
 						{/each}
 					</div>
@@ -373,8 +387,9 @@ const modelCache = new Map<string, string[]>();
 							{@const displayIdx = sliderDragging !== null ? sliderDragging : (currentIdx >= 0 ? currentIdx : 0)}
 							{@const displayModel = agent.models[displayIdx]}
 							<div class="mt-2 pt-2 border-t border-primary-content/20">
-								<div class="text-xs font-semibold mb-1 truncate">
-									{displayModel ? `${displayModel.key_id} / ${displayModel.model_id}` : `${activeKeyId} / ${activeModelId}`}
+								<div class="text-xs font-semibold mb-1 truncate flex items-center gap-1">
+									<span class="truncate">{displayModel ? `${displayModel.key_id} / ${displayModel.model_id}` : `${activeKeyId} / ${activeModelId}`}</span>
+									<span class="badge badge-xs shrink-0">{effortLabel(displayModel?.effort)}</span>
 								</div>
 								<input
 									type="range"
diff --git a/packages/frontend/src/lib/components/SidebarPanel.svelte b/packages/frontend/src/lib/components/SidebarPanel.svelte
index 491b1bd..3372396 100644
--- a/packages/frontend/src/lib/components/SidebarPanel.svelte
+++ b/packages/frontend/src/lib/components/SidebarPanel.svelte
@@ -34,7 +34,7 @@ const {
 	reasoningEffort = "max",
 	activeAgentSlug = null as string | null,
 	activeTabParentId = null as string | null,
-	activeAgentModels = null as Array<{ key_id: string; model_id: string }> | null,
+	activeAgentModels = null as Array<{ key_id: string; model_id: string; effort?: string }> | null,
 	workingDirectory = null as string | null,
 	onKeyChange,
 	onModelChange,
@@ -54,7 +54,7 @@ const {
 	reasoningEffort?: string;
 	activeAgentSlug?: string | null;
 	activeTabParentId?: string | null;
-	activeAgentModels?: Array<{ key_id: string; model_id: string }> | null;
+	activeAgentModels?: Array<{ key_id: string; model_id: string; effort?: string }> | null;
 	workingDirectory?: string | null;
 	onKeyChange: (keyId: string) => void;
 	onModelChange: (keyId: string, modelId: string) => void;
diff --git a/packages/frontend/src/lib/tabs.svelte.ts b/packages/frontend/src/lib/tabs.svelte.ts
index 3fd7e5f..d3061c3 100644
--- a/packages/frontend/src/lib/tabs.svelte.ts
+++ b/packages/frontend/src/lib/tabs.svelte.ts
@@ -12,6 +12,12 @@ import {
 // source of truth for HISTORY; `groupRowsToMessages` derives render bubbles.
 import { groupRowsToMessages, type MessageRow } from "@dispatch/core/src/chunks/transform.js";
 import type { ChunkRow } from "@dispatch/core/src/types/index.js";
+import {
+	type AgentModelEntry,
+	DEFAULT_REASONING_EFFORT,
+	isReasoningEffort,
+	type ReasoningEffort,
+} from "@dispatch/core/src/types/index.js";
 import { config } from "./config.js";
 import { appSettings } from "./settings.svelte.js";
 import type {
@@ -154,7 +160,7 @@ export interface Tab {
 	agentStatus: "idle" | "running" | "error";
 	keyId: string | null;
 	modelId: string | null;
-	reasoningEffort: string;
+	reasoningEffort: ReasoningEffort;
 	currentAssistantId: string | null;
 	tasks: TaskItem[];
 	injectedSkills: string[];
@@ -162,7 +168,7 @@ export interface Tab {
 	persistent: boolean;
 	agentSlug: string | null;
 	agentScope: string | null;
-	agentModels: Array<{ key_id: string; model_id: string }> | null;
+	agentModels: AgentModelEntry[] | null;
 	workingDirectory: string | null;
 	queuedMessages: QueuedMessage[];
 	chunkLimit: number;
@@ -280,7 +286,7 @@ export function createTabStore() {
 			agentStatus: "idle",
 			keyId: null,
 			modelId: null,
-			reasoningEffort: "max",
+			reasoningEffort: DEFAULT_REASONING_EFFORT,
 			currentAssistantId: null,
 			tasks: [],
 			injectedSkills: [],
@@ -355,7 +361,7 @@ export function createTabStore() {
 				agentStatus: "idle",
 				keyId: tabData.keyId ?? null,
 				modelId: tabData.modelId ?? null,
-				reasoningEffort: "max",
+				reasoningEffort: DEFAULT_REASONING_EFFORT,
 				currentAssistantId: null,
 				tasks: [],
 				injectedSkills: [],
@@ -829,7 +835,7 @@ export function createTabStore() {
 				agentStatus,
 				keyId: row.keyId ?? null,
 				modelId: row.modelId ?? null,
-				reasoningEffort: "max",
+				reasoningEffort: DEFAULT_REASONING_EFFORT,
 				currentAssistantId,
 				tasks: [],
 				injectedSkills: [],
@@ -1154,7 +1160,7 @@ export function createTabStore() {
 					parentTabId: string | null;
 					agentSlug?: string | null;
 					workingDirectory: string | null;
-					agentModels?: Array<{ key_id: string; model_id: string }> | null;
+					agentModels?: AgentModelEntry[] | null;
 				};
 				// Only add if we don't already have this tab
 				if (!getTabById(newTabEvent.id)) {
@@ -1168,7 +1174,7 @@ export function createTabStore() {
 						agentStatus: "running",
 						keyId: newTabEvent.keyId ?? null,
 						modelId: newTabEvent.modelId ?? null,
-						reasoningEffort: "max",
+						reasoningEffort: DEFAULT_REASONING_EFFORT,
 						currentAssistantId: null,
 						tasks: [],
 						injectedSkills: [],
@@ -1382,7 +1388,7 @@ export function createTabStore() {
 					name: string;
 					skills: string[];
 					tools: string[];
-					models: Array<{ key_id: string; model_id: string }>;
+					models: AgentModelEntry[];
 					cwd?: string;
 				}>;
 			};
@@ -1451,7 +1457,7 @@ export function createTabStore() {
 				agents?: Array<{
 					slug: string;
 					scope: string;
-					models: Array<{ key_id: string; model_id: string }>;
+					models: AgentModelEntry[];
 					cwd?: string;
 				}>;
 			};
@@ -1733,6 +1739,19 @@ export function createTabStore() {
 		}).catch(() => {});
 	}
 
+	/**
+	 * Update the per-tab reasoning-effort selector. Ignores unrecognised
+	 * values so an out-of-range string from the UI can't corrupt the tab
+	 * state. This is the per-tab effort in the per-model → per-tab → default
+	 * resolution chain.
+	 */
+	function setReasoningEffort(effort: string): void {
+		if (!isReasoningEffort(effort)) return;
+		const tab = getActiveTab();
+		if (!tab) return;
+		updateTab(tab.id, { reasoningEffort: effort });
+	}
+
 	function setWorkingDirectory(dir: string | null): void {
 		const tab = getActiveTab();
 		if (!tab) return;
@@ -1745,7 +1764,7 @@ export function createTabStore() {
 			scope: string;
 			skills: string[];
 			tools: string[];
-			models: Array<{ key_id: string; model_id: string }>;
+			models: AgentModelEntry[];
 			cwd?: string;
 		} | null,
 	): void {
@@ -2002,6 +2021,7 @@ export function createTabStore() {
 		stopGeneration,
 		changeModel,
 		setKey,
+		setReasoningEffort,
 		setAgent,
 		replyPermission,
 		copyConversation,