diff --git a/CHANGELOG.md b/CHANGELOG.md
index f0ab408c19b..ebd4a32381d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@ Docs: https://docs.openclaw.ai
 
 ### Changes
 
+- Chat commands: add `/think default` and `/fast default` to clear session overrides and inherit configured/provider defaults. (#79385) Thanks @VACInc.
 - Dependencies: refresh workspace dependency pins and lockfile, including `@openai/codex` `0.130.0`, `acpx` `0.7.0`, AWS SDK `3.1044.0`, OpenTelemetry `0.217.0`, `typebox` `1.1.38`, `vite` `8.0.11`, `oxfmt` `0.48.0`, and `oxlint` `1.63.0`, and update the Codex harness model snapshot for the new bundled app-server catalog.
 - Plugins/install: add guarded plugin install overrides so onboarding and repair tests can route specific plugins to registry specs or local `npm pack` artifacts via environment variables.
 - Tests/Docker: add Codex on-demand install and live plugin-tool dependency E2E lanes for packaged onboarding and npm-pack plugin proof.
diff --git a/docs/tools/slash-commands.md b/docs/tools/slash-commands.md
index f0a32073f1e..a4a88c3ca30 100644
--- a/docs/tools/slash-commands.md
+++ b/docs/tools/slash-commands.md
@@ -135,10 +135,10 @@ Current source-of-truth:
 
   </Accordion>
   <Accordion title="Model and run controls">
-    - `/think <level>` sets the thinking level. Options come from the active model's provider profile; common levels are `off`, `minimal`, `low`, `medium`, and `high`, with custom levels such as `xhigh`, `adaptive`, `max`, or binary `on` only where supported. Aliases: `/thinking`, `/t`.
+    - `/think <level|default>` sets the thinking level or clears the session override. Options come from the active model's provider profile; common levels are `off`, `minimal`, `low`, `medium`, and `high`, with custom levels such as `xhigh`, `adaptive`, `max`, or binary `on` only where supported. Aliases: `/thinking`, `/t`.
     - `/verbose on|off|full` toggles verbose output. Alias: `/v`.
     - `/trace on|off` toggles plugin trace output for the current session.
-    - `/fast [status|on|off]` shows or sets fast mode.
+    - `/fast [status|on|off|default]` shows, sets, or clears fast mode.
     - `/reasoning [on|off|stream]` toggles reasoning visibility. Alias: `/reason`.
     - `/elevated [on|off|ask|full]` toggles elevated mode. Alias: `/elev`.
     - `/exec host=<auto|sandbox|gateway|node> security=<deny|allowlist|full> ask=<off|on-miss|always> node=<id>` shows or sets exec defaults.
diff --git a/docs/tools/thinking.md b/docs/tools/thinking.md
index 0968bf25ea4..d6d37e28115 100644
--- a/docs/tools/thinking.md
+++ b/docs/tools/thinking.md
@@ -48,7 +48,8 @@ title: "Thinking levels"
 ## Setting a session default
 
 - Send a message that is **only** the directive (whitespace allowed), e.g. `/think:medium` or `/t high`.
-- That sticks for the current session (per-sender by default); cleared by `/think:off` or session idle reset.
+- That sticks for the current session (per-sender by default). Use `/think default` to clear the session override and inherit the configured/provider default; aliases include `inherit`, `clear`, `reset`, and `unpin`.
+- `/think off` stores an explicit off override. It disables thinking until you change or clear the session override.
 - Confirmation reply is sent (`Thinking level set to high.` / `Thinking disabled.`). If the level is invalid (e.g. `/thinking big`), the command is rejected with a hint and the session state is left unchanged.
 - Send `/think` (or `/think:`) with no argument to see the current thinking level.
 
@@ -59,11 +60,11 @@ title: "Thinking levels"
 
 ## Fast mode (/fast)
 
-- Levels: `on|off`.
-- Directive-only message toggles a session fast-mode override and replies `Fast mode enabled.` / `Fast mode disabled.`.
+- Levels: `on|off|default`.
+- Directive-only message toggles a session fast-mode override and replies `Fast mode enabled.` / `Fast mode disabled.`. Use `/fast default` to clear the session override and inherit the configured default; aliases include `inherit`, `clear`, `reset`, and `unpin`.
 - Send `/fast` (or `/fast status`) with no mode to see the current effective fast-mode state.
 - OpenClaw resolves fast mode in this order:
-  1. Inline/directive-only `/fast on|off`
+  1. Inline/directive-only `/fast on|off` override (`/fast default` clears this layer)
   2. Session override
   3. Per-agent default (`agents.list[].fastModeDefault`)
   4. Per-model config: `agents.defaults.models["<provider>/<model>"].params.fastMode`
diff --git a/src/auto-reply/command-status-builders.ts b/src/auto-reply/command-status-builders.ts
index 30310f7551d..c16c8f11d4d 100644
--- a/src/auto-reply/command-status-builders.ts
+++ b/src/auto-reply/command-status-builders.ts
@@ -59,9 +59,9 @@ export function buildHelpMessage(cfg?: OpenClawConfig): string {
   lines.push("");
 
   const optionParts = [
-    "/think <level>",
+    "/think <level|default>",
     "/model <id>",
-    "/fast status|on|off",
+    "/fast status|on|off|default",
     "/verbose on|off|full",
     "/trace on|off|raw",
   ];
diff --git a/src/auto-reply/commands-registry.shared.ts b/src/auto-reply/commands-registry.shared.ts
index 79810656727..05fea14000f 100644
--- a/src/auto-reply/commands-registry.shared.ts
+++ b/src/auto-reply/commands-registry.shared.ts
@@ -13,7 +13,7 @@ type ListThinkingLevels = (
   provider?: string | null,
   model?: string | null,
   catalog?: CommandArgChoiceContext["catalog"],
-) => ThinkLevel[];
+) => string[];
 
 const BROWSER_SAFE_THINKING_LEVELS: ThinkLevel[] = [
   ...BASE_THINKING_LEVELS,
@@ -147,8 +147,12 @@ export function assertCommandRegistry(commands: ChatCommandDefinition[]): void {
 export function buildBuiltinChatCommands(
   params: { listThinkingLevels?: ListThinkingLevels } = {},
 ): ChatCommandDefinition[] {
-  const listThinkingLevelChoices =
+  const configuredThinkingLevels =
     params.listThinkingLevels ?? (() => BROWSER_SAFE_THINKING_LEVELS);
+  const listThinkingLevelChoices: ListThinkingLevels = (provider, model, catalog) => {
+    const levels = configuredThinkingLevels(provider, model, catalog);
+    return ["default", ...levels.filter((level) => level !== "default")];
+  };
   const commands: ChatCommandDefinition[] = [
     defineChatCommand({
       key: "help",
@@ -799,9 +803,9 @@ export function buildBuiltinChatCommands(
       args: [
         {
           name: "mode",
-          description: "status, on, or off",
+          description: "status, on, off, or default",
           type: "string",
-          choices: ["status", "on", "off"],
+          choices: ["status", "on", "off", "default"],
         },
       ],
       argsMenu: "auto",
diff --git a/src/auto-reply/commands-registry.test.ts b/src/auto-reply/commands-registry.test.ts
index 48aaae362e1..eef251b1e78 100644
--- a/src/auto-reply/commands-registry.test.ts
+++ b/src/auto-reply/commands-registry.test.ts
@@ -377,7 +377,7 @@ describe("commands registry", () => {
       category: "options",
     });
     const modeArg = requireCommandArg(fast, "mode");
-    expect(modeArg.choices).toEqual(["status", "on", "off"]);
+    expect(modeArg.choices).toEqual(["status", "on", "off", "default"]);
   });
 
   it("detects known text commands", () => {
@@ -633,6 +633,7 @@ describe("commands registry args", () => {
 
     expect(menu.arg.name).toBe("level");
     expect(menu.choices.map((choice) => choice.value)).toEqual([
+      "default",
       "off",
       "low",
       "medium",
@@ -640,7 +641,7 @@ describe("commands registry args", () => {
       "max",
     ]);
     expect(formatCommandArgMenuTitle({ command, menu })).toBe(
-      "Choose level for /think.\nOptions: off, low, medium, high, max.",
+      "Choose level for /think.\nOptions: default, off, low, medium, high, max.",
     );
   });
 
diff --git a/src/auto-reply/reply.directive.parse.test.ts b/src/auto-reply/reply.directive.parse.test.ts
index e76ebebb02e..21b72b71b67 100644
--- a/src/auto-reply/reply.directive.parse.test.ts
+++ b/src/auto-reply/reply.directive.parse.test.ts
@@ -69,6 +69,21 @@ describe("directive parsing", () => {
     expect(res.fastMode).toBe(true);
   });
 
+  it("parses default thinking and fast directives as override clears", () => {
+    expect(parseInlineDirectives("/think default")).toMatchObject({
+      hasThinkDirective: true,
+      thinkLevel: undefined,
+      rawThinkLevel: "default",
+      clearThinkLevel: true,
+    });
+    expect(parseInlineDirectives("/fast inherit")).toMatchObject({
+      hasFastDirective: true,
+      fastMode: undefined,
+      rawFastMode: "inherit",
+      clearFastMode: true,
+    });
+  });
+
   it("matches elevated with leading space", () => {
     const res = extractElevatedDirective(" please /elevated on now");
     expect(res.hasDirective).toBe(true);
diff --git a/src/auto-reply/reply/commands-session-usage.test.ts b/src/auto-reply/reply/commands-session-usage.test.ts
index 47289332317..1fcfd709c34 100644
--- a/src/auto-reply/reply/commands-session-usage.test.ts
+++ b/src/auto-reply/reply/commands-session-usage.test.ts
@@ -241,4 +241,45 @@ describe("handleFastCommand", () => {
       }),
     );
   });
+
+  it("clears fast mode for /fast default", async () => {
+    const params = buildUsageParams();
+    params.command.commandBodyNormalized = "/fast default";
+    params.sessionEntry = {
+      sessionId: "target-session",
+      updatedAt: Date.now(),
+      fastMode: true,
+    };
+    params.sessionStore = { [params.sessionKey]: params.sessionEntry };
+
+    const result = await handleFastCommand(params, true);
+
+    expect(result?.shouldContinue).toBe(false);
+    expect(result?.reply?.text).toBe("⚙️ Fast mode reset to default.");
+    expect(params.sessionEntry.fastMode).toBeUndefined();
+    expect(params.sessionStore[params.sessionKey]?.fastMode).toBeUndefined();
+  });
+
+  it("clears fast mode on the target store entry for /fast default", async () => {
+    const params = buildUsageParams();
+    params.command.commandBodyNormalized = "/fast default";
+    params.sessionEntry = {
+      sessionId: "wrapper-session",
+      updatedAt: Date.now(),
+      fastMode: false,
+    };
+    params.sessionStore = {
+      [params.sessionKey]: {
+        sessionId: "target-session",
+        updatedAt: Date.now(),
+        fastMode: true,
+      },
+    };
+
+    const result = await handleFastCommand(params, true);
+
+    expect(result?.reply?.text).toBe("⚙️ Fast mode reset to default.");
+    expect(params.sessionEntry.fastMode).toBe(false);
+    expect(params.sessionStore[params.sessionKey]?.fastMode).toBeUndefined();
+  });
 });
diff --git a/src/auto-reply/reply/commands-session.ts b/src/auto-reply/reply/commands-session.ts
index 0aadaa330a7..5e91c107a6a 100644
--- a/src/auto-reply/reply/commands-session.ts
+++ b/src/auto-reply/reply/commands-session.ts
@@ -29,7 +29,12 @@ import {
 import { formatTokenCount, formatUsd } from "../../utils/usage-format.js";
 import { parseActivationCommand } from "../group-activation.js";
 import { parseSendPolicyCommand } from "../send-policy.js";
-import { normalizeFastMode, normalizeUsageDisplay, resolveResponseUsageMode } from "../thinking.js";
+import {
+  isSessionDefaultDirectiveValue,
+  normalizeFastMode,
+  normalizeUsageDisplay,
+  resolveResponseUsageMode,
+} from "../thinking.js";
 import { resolveCommandSurfaceChannel } from "./channel-context.js";
 import { rejectNonOwnerCommand, rejectUnauthorizedCommand } from "./command-gates.js";
 import { handleAbortTrigger, handleStopCommand } from "./commands-session-abort.js";
@@ -412,17 +417,29 @@ export const handleFastCommand: CommandHandler = async (params, allowTextCommand
     };
   }
 
-  const nextMode = normalizeFastMode(rawMode);
+  const targetSessionEntry = params.sessionStore?.[params.sessionKey] ?? params.sessionEntry;
+  const resetsToDefault = isSessionDefaultDirectiveValue(rawMode);
+  const nextMode = resetsToDefault ? undefined : normalizeFastMode(rawMode);
   if (nextMode === undefined) {
+    if (resetsToDefault) {
+      if (targetSessionEntry && params.sessionStore && params.sessionKey) {
+        delete targetSessionEntry.fastMode;
+        await persistSessionEntry({ ...params, sessionEntry: targetSessionEntry });
+      }
+      return {
+        shouldContinue: false,
+        reply: { text: "⚙️ Fast mode reset to default." },
+      };
+    }
     return {
       shouldContinue: false,
-      reply: { text: "⚙️ Usage: /fast status|on|off" },
+      reply: { text: "⚙️ Usage: /fast status|on|off|default" },
     };
   }
 
-  if (params.sessionEntry && params.sessionStore && params.sessionKey) {
-    params.sessionEntry.fastMode = nextMode;
-    await persistSessionEntry(params);
+  if (targetSessionEntry && params.sessionStore && params.sessionKey) {
+    targetSessionEntry.fastMode = nextMode;
+    await persistSessionEntry({ ...params, sessionEntry: targetSessionEntry });
   }
 
   return {
diff --git a/src/auto-reply/reply/commands-subagents.test-helpers.ts b/src/auto-reply/reply/commands-subagents.test-helpers.ts
index 91beb33f2e5..b0545127304 100644
--- a/src/auto-reply/reply/commands-subagents.test-helpers.ts
+++ b/src/auto-reply/reply/commands-subagents.test-helpers.ts
@@ -48,8 +48,10 @@ export function createEmptyInlineDirectives(): InlineDirectives {
   return {
     cleaned: "",
     hasThinkDirective: false,
+    clearThinkLevel: false,
     hasVerboseDirective: false,
     hasFastDirective: false,
+    clearFastMode: false,
     hasReasoningDirective: false,
     hasTraceDirective: false,
     hasElevatedDirective: false,
diff --git a/src/auto-reply/reply/directive-handling.impl.ts b/src/auto-reply/reply/directive-handling.impl.ts
index 69b5d0a37d9..b0a1287cd65 100644
--- a/src/auto-reply/reply/directive-handling.impl.ts
+++ b/src/auto-reply/reply/directive-handling.impl.ts
@@ -142,25 +142,28 @@ export async function handleDirectiveOnly(
     provider: resolvedProvider,
     model: resolvedModel,
     agentId: activeAgentId,
-    sessionEntry,
+    sessionEntry: directives.clearFastMode ? undefined : sessionEntry,
   });
-  const effectiveFastMode = directives.fastMode ?? currentFastMode ?? fastModeState.enabled;
+  const effectiveFastMode =
+    directives.fastMode ??
+    (directives.clearFastMode ? fastModeState.enabled : currentFastMode) ??
+    fastModeState.enabled;
   const effectiveFastModeSource =
     directives.fastMode !== undefined ? "session" : fastModeState.source;
 
-  if (directives.hasThinkDirective && !directives.thinkLevel) {
+  if (directives.hasThinkDirective && !directives.thinkLevel && !directives.clearThinkLevel) {
     // If no argument was provided, show the current level
     if (!directives.rawThinkLevel) {
       const level = currentThinkLevel ?? "off";
       return {
         text: withOptions(
           `Current thinking level: ${level}.`,
-          formatThinkingLevels(resolvedProvider, resolvedModel, ", ", thinkingCatalog),
+          `default, ${formatThinkingLevels(resolvedProvider, resolvedModel, ", ", thinkingCatalog)}`,
         ),
       };
     }
     return {
-      text: `Unrecognized thinking level "${directives.rawThinkLevel}". Valid levels: ${formatThinkingLevels(resolvedProvider, resolvedModel, ", ", thinkingCatalog)}.`,
+      text: `Unrecognized thinking level "${directives.rawThinkLevel}". Valid levels: default, ${formatThinkingLevels(resolvedProvider, resolvedModel, ", ", thinkingCatalog)}.`,
     };
   }
   if (directives.hasVerboseDirective && !directives.verboseLevel) {
@@ -185,7 +188,11 @@ export async function handleDirectiveOnly(
       text: `Unrecognized trace level "${directives.rawTraceLevel}". Valid levels: off, on, raw.`,
     };
   }
-  if (directives.hasFastDirective && directives.fastMode === undefined) {
+  if (
+    directives.hasFastDirective &&
+    directives.fastMode === undefined &&
+    !directives.clearFastMode
+  ) {
     if (
       !directives.rawFastMode ||
       normalizeLowercaseStringOrEmpty(directives.rawFastMode) === "status"
@@ -199,12 +206,12 @@ export async function handleDirectiveOnly(
       return {
         text: withOptions(
           `Current fast mode: ${effectiveFastMode ? "on" : "off"}${sourceSuffix}.`,
-          "status, on, off",
+          "status, on, off, default",
         ),
       };
     }
     return {
-      text: `Unrecognized fast mode "${directives.rawFastMode}". Valid levels: status, on, off.`,
+      text: `Unrecognized fast mode "${directives.rawFastMode}". Valid levels: status, on, off, default.`,
     };
   }
   if (directives.hasReasoningDirective && !directives.reasoningLevel) {
@@ -351,8 +358,10 @@ export async function handleDirectiveOnly(
     elevatedAllowed;
   let modelSelectionUpdated = false;
   const shouldPersistSessionEntry =
-    (directives.hasThinkDirective && Boolean(directives.thinkLevel)) ||
-    (directives.hasFastDirective && directives.fastMode !== undefined) ||
+    (directives.hasThinkDirective &&
+      (Boolean(directives.thinkLevel) || directives.clearThinkLevel)) ||
+    (directives.hasFastDirective &&
+      (directives.fastMode !== undefined || directives.clearFastMode)) ||
     (directives.hasVerboseDirective &&
       Boolean(directives.verboseLevel) &&
       allowInternalVerbosePersistence) ||
@@ -364,16 +373,25 @@ export async function handleDirectiveOnly(
     directives.hasQueueDirective ||
     shouldRemapUnsupportedThinkLevel;
   const fastModeChanged =
-    directives.hasFastDirective &&
-    directives.fastMode !== undefined &&
-    directives.fastMode !== currentFastMode;
+    (directives.hasFastDirective &&
+      directives.fastMode !== undefined &&
+      directives.fastMode !== currentFastMode) ||
+    (directives.clearFastMode && currentFastMode !== fastModeState.enabled);
   let reasoningChanged =
     directives.hasReasoningDirective && directives.reasoningLevel !== undefined;
   if (shouldPersistSessionEntry) {
-    if (directives.hasThinkDirective && directives.thinkLevel && resolvedDirectiveThinkLevel) {
+    if (directives.clearThinkLevel) {
+      delete sessionEntry.thinkingLevel;
+    } else if (
+      directives.hasThinkDirective &&
+      directives.thinkLevel &&
+      resolvedDirectiveThinkLevel
+    ) {
       sessionEntry.thinkingLevel = resolvedDirectiveThinkLevel;
     }
-    if (directives.hasFastDirective && directives.fastMode !== undefined) {
+    if (directives.clearFastMode) {
+      delete sessionEntry.fastMode;
+    } else if (directives.hasFastDirective && directives.fastMode !== undefined) {
       sessionEntry.fastMode = directives.fastMode;
     }
     if (shouldRemapUnsupportedThinkLevel && remappedUnsupportedThinkLevel) {
@@ -488,7 +506,9 @@ export async function handleDirectiveOnly(
   });
 
   const parts: string[] = [];
-  if (directives.hasThinkDirective && directives.thinkLevel) {
+  if (directives.clearThinkLevel) {
+    parts.push("Thinking level reset to default.");
+  } else if (directives.hasThinkDirective && directives.thinkLevel) {
     const displayedThinkLevel = resolvedDirectiveThinkLevel ?? directives.thinkLevel;
     parts.push(
       displayedThinkLevel === "off"
@@ -501,7 +521,9 @@ export async function handleDirectiveOnly(
       );
     }
   }
-  if (directives.hasFastDirective && directives.fastMode !== undefined) {
+  if (directives.clearFastMode) {
+    parts.push(formatDirectiveAck("Fast mode reset to default."));
+  } else if (directives.hasFastDirective && directives.fastMode !== undefined) {
     parts.push(
       directives.fastMode
         ? formatDirectiveAck("Fast mode enabled.")
@@ -617,9 +639,10 @@ export async function handleDirectiveOnly(
     parts.push(formatDirectiveAck(`Queue drop set to ${directives.dropPolicy}.`));
   }
   if (fastModeChanged) {
-    enqueueSystemEvent(`Fast mode ${sessionEntry.fastMode ? "enabled" : "disabled"}.`, {
+    const nextFastMode = directives.clearFastMode ? fastModeState.enabled : sessionEntry.fastMode;
+    enqueueSystemEvent(`Fast mode ${nextFastMode ? "enabled" : "disabled"}.`, {
       sessionKey,
-      contextKey: `fast:${sessionEntry.fastMode ? "on" : "off"}`,
+      contextKey: `fast:${nextFastMode ? "on" : "off"}`,
     });
   }
   const ack = parts.join(" ").trim();
diff --git a/src/auto-reply/reply/directive-handling.model.test.ts b/src/auto-reply/reply/directive-handling.model.test.ts
index 5cffd2e9ef6..5982ab3aff9 100644
--- a/src/auto-reply/reply/directive-handling.model.test.ts
+++ b/src/auto-reply/reply/directive-handling.model.test.ts
@@ -1331,6 +1331,22 @@ describe("handleDirectiveOnly model persist behavior (fixes #1435)", () => {
     expect(sessionStore["agent:main:dm:1"]?.thinkingLevel).toBe("off");
   });
 
+  it("clears thinking override for default directives", async () => {
+    const sessionEntry = createSessionEntry({ thinkingLevel: "high" });
+    const sessionStore = { [sessionKey]: sessionEntry };
+    const result = await handleDirectiveOnly(
+      createHandleParams({
+        directives: parseInlineDirectives("/think default"),
+        sessionEntry,
+        sessionStore,
+      }),
+    );
+
+    expect(result?.text).toContain("Thinking level reset to default.");
+    expect(sessionEntry.thinkingLevel).toBeUndefined();
+    expect(sessionStore["agent:main:dm:1"]?.thinkingLevel).toBeUndefined();
+  });
+
   it("reports current thinking status", async () => {
     setDirectiveTestProviders([
       {
@@ -1358,7 +1374,7 @@ describe("handleDirectiveOnly model persist behavior (fixes #1435)", () => {
     );
 
     expect(result?.text).toContain("Current thinking level: low");
-    expect(result?.text).toContain("Options: off, minimal, low, medium, adaptive, high.");
+    expect(result?.text).toContain("Options: default, off, minimal, low, medium, adaptive, high.");
   });
 
   it("uses catalog reasoning metadata for provider-owned thinking levels", async () => {
@@ -1468,6 +1484,17 @@ describe("handleDirectiveOnly model persist behavior (fixes #1435)", () => {
     );
     expect(offReply?.text).toContain("Fast mode disabled");
     expect(sessionEntry.fastMode).toBe(false);
+
+    const defaultReply = await handleDirectiveOnly(
+      createHandleParams({
+        directives: parseInlineDirectives("/fast default"),
+        sessionEntry,
+        sessionStore,
+        currentFastMode: sessionEntry.fastMode,
+      }),
+    );
+    expect(defaultReply?.text).toContain("Fast mode reset to default");
+    expect(sessionEntry.fastMode).toBeUndefined();
   });
 
   it("persists and reports elevated-mode directives when allowed", async () => {
diff --git a/src/auto-reply/reply/directive-handling.parse.ts b/src/auto-reply/reply/directive-handling.parse.ts
index 85087aef3bd..6346b5b0e9a 100644
--- a/src/auto-reply/reply/directive-handling.parse.ts
+++ b/src/auto-reply/reply/directive-handling.parse.ts
@@ -1,5 +1,6 @@
 import type { ExecAsk, ExecSecurity, ExecTarget } from "../../infra/exec-approvals.js";
 import { extractModelDirective } from "../model.js";
+import { isSessionDefaultDirectiveValue } from "../thinking.js";
 import type {
   ElevatedLevel,
   ReasoningLevel,
@@ -25,6 +26,7 @@ export type InlineDirectives = {
   hasThinkDirective: boolean;
   thinkLevel?: ThinkLevel;
   rawThinkLevel?: string;
+  clearThinkLevel: boolean;
   hasVerboseDirective: boolean;
   verboseLevel?: VerboseLevel;
   rawVerboseLevel?: string;
@@ -34,6 +36,7 @@ export type InlineDirectives = {
   hasFastDirective: boolean;
   fastMode?: boolean;
   rawFastMode?: string;
+  clearFastMode: boolean;
   hasReasoningDirective: boolean;
   reasoningLevel?: ReasoningLevel;
   rawReasoningLevel?: string;
@@ -173,6 +176,7 @@ export function parseInlineDirectives(
     hasThinkDirective,
     thinkLevel,
     rawThinkLevel,
+    clearThinkLevel: hasThinkDirective && isSessionDefaultDirectiveValue(rawThinkLevel),
     hasVerboseDirective,
     verboseLevel,
     rawVerboseLevel,
@@ -182,6 +186,7 @@ export function parseInlineDirectives(
     hasFastDirective,
     fastMode,
     rawFastMode,
+    clearFastMode: hasFastDirective && isSessionDefaultDirectiveValue(rawFastMode),
     hasReasoningDirective,
     reasoningLevel,
     rawReasoningLevel,
diff --git a/src/auto-reply/reply/directive-handling.persist.ts b/src/auto-reply/reply/directive-handling.persist.ts
index eb095740b9b..34cf3f97e71 100644
--- a/src/auto-reply/reply/directive-handling.persist.ts
+++ b/src/auto-reply/reply/directive-handling.persist.ts
@@ -166,10 +166,21 @@ export async function persistInlineDirectives(params: {
       directives.hasReasoningDirective && directives.reasoningLevel !== undefined;
     let updated = false;
 
-    if (directives.hasThinkDirective && directives.thinkLevel) {
+    if (directives.clearThinkLevel) {
+      if (sessionEntry.thinkingLevel) {
+        delete sessionEntry.thinkingLevel;
+        updated = true;
+      }
+    } else if (directives.hasThinkDirective && directives.thinkLevel) {
       sessionEntry.thinkingLevel = directives.thinkLevel;
       updated = true;
     }
+    if (directives.clearFastMode) {
+      if (sessionEntry.fastMode !== undefined) {
+        delete sessionEntry.fastMode;
+        updated = true;
+      }
+    }
     if (
       directives.hasVerboseDirective &&
       directives.verboseLevel &&
diff --git a/src/auto-reply/reply/get-reply-directives-utils.ts b/src/auto-reply/reply/get-reply-directives-utils.ts
index bf3375b6a7f..f588bf31d9a 100644
--- a/src/auto-reply/reply/get-reply-directives-utils.ts
+++ b/src/auto-reply/reply/get-reply-directives-utils.ts
@@ -23,6 +23,7 @@ export function clearInlineDirectives(cleaned: string): InlineDirectives {
     hasThinkDirective: false,
     thinkLevel: undefined,
     rawThinkLevel: undefined,
+    clearThinkLevel: false,
     hasVerboseDirective: false,
     verboseLevel: undefined,
     rawVerboseLevel: undefined,
@@ -32,6 +33,7 @@ export function clearInlineDirectives(cleaned: string): InlineDirectives {
     hasFastDirective: false,
     fastMode: undefined,
     rawFastMode: undefined,
+    clearFastMode: false,
     hasReasoningDirective: false,
     reasoningLevel: undefined,
     rawReasoningLevel: undefined,
diff --git a/src/auto-reply/reply/get-reply-directives.ts b/src/auto-reply/reply/get-reply-directives.ts
index 0336a6dc384..e604179bdb8 100644
--- a/src/auto-reply/reply/get-reply-directives.ts
+++ b/src/auto-reply/reply/get-reply-directives.ts
@@ -334,8 +334,10 @@ export async function resolveReplyDirectives(params: {
     : {
         ...parsedDirectives,
         hasThinkDirective: false,
+        clearThinkLevel: false,
         hasVerboseDirective: false,
         hasFastDirective: false,
+        clearFastMode: false,
         hasReasoningDirective: false,
         reasoningLevel: undefined,
         rawReasoningLevel: undefined,
@@ -422,10 +424,11 @@ export async function resolveReplyDirectives(params: {
     groupResolution,
   });
   const defaultActivation = defaultGroupActivation(requireMention);
+  const sessionThinkLevel = directives.clearThinkLevel
+    ? undefined
+    : (targetSessionEntry?.thinkingLevel as ThinkLevel | undefined);
   const resolvedThinkLevel =
-    normalizeThinkLevel(opts?.thinkingLevelOverride) ??
-    directives.thinkLevel ??
-    (targetSessionEntry?.thinkingLevel as ThinkLevel | undefined);
+    normalizeThinkLevel(opts?.thinkingLevelOverride) ?? directives.thinkLevel ?? sessionThinkLevel;
   const resolvedFastMode =
     opts?.fastModeOverride ??
     directives.fastMode ??
@@ -434,7 +437,7 @@ export async function resolveReplyDirectives(params: {
       provider,
       model,
       agentId,
-      sessionEntry: targetSessionEntry,
+      sessionEntry: directives.clearFastMode ? undefined : targetSessionEntry,
     }).enabled;
 
   const resolvedVerboseLevel =
@@ -537,7 +540,7 @@ export async function resolveReplyDirectives(params: {
 
   const thinkingExplicitlySet =
     directives.thinkLevel !== undefined ||
-    targetSessionEntry?.thinkingLevel !== undefined ||
+    sessionThinkLevel !== undefined ||
     agentCfg?.thinkingDefault !== undefined;
 
   // When neither directive nor session nor agent set reasoning, default to model capability
diff --git a/src/auto-reply/status.test.ts b/src/auto-reply/status.test.ts
index d7993ae01b8..74843f83dbe 100644
--- a/src/auto-reply/status.test.ts
+++ b/src/auto-reply/status.test.ts
@@ -2103,7 +2103,7 @@ describe("buildHelpMessage", () => {
   });
 
   it("includes /fast in help output", () => {
-    expect(buildHelpMessage()).toContain("/fast status|on|off");
+    expect(buildHelpMessage()).toContain("/fast status|on|off|default");
   });
 
   it("includes raw trace mode in help output", () => {
diff --git a/src/auto-reply/thinking.shared.ts b/src/auto-reply/thinking.shared.ts
index 989057de0ef..0d1a8b4e707 100644
--- a/src/auto-reply/thinking.shared.ts
+++ b/src/auto-reply/thinking.shared.ts
@@ -83,6 +83,14 @@ export function normalizeThinkLevel(raw?: string | null): ThinkLevel | undefined
   return undefined;
 }
 
+export function isSessionDefaultDirectiveValue(raw?: string | null): boolean {
+  const key = normalizeOptionalLowercaseString(raw);
+  if (!key) {
+    return false;
+  }
+  return ["default", "inherit", "inherited", "clear", "reset", "unpin"].includes(key);
+}
+
 export function formatXHighModelHint(): string {
   return "provider models that advertise xhigh reasoning";
 }
diff --git a/src/auto-reply/thinking.ts b/src/auto-reply/thinking.ts
index 9226d5a6cd9..5a139e2a609 100644
--- a/src/auto-reply/thinking.ts
+++ b/src/auto-reply/thinking.ts
@@ -8,6 +8,7 @@ import {
 import type { ThinkLevel, ThinkingCatalogEntry } from "./thinking.shared.js";
 export {
   formatXHighModelHint,
+  isSessionDefaultDirectiveValue,
   normalizeElevatedLevel,
   normalizeFastMode,
   normalizeNoticeLevel,