diff --git a/scripts/format-staged.js b/scripts/format-staged.js
index 0ad2d7dd7..5a524f821 100644
--- a/scripts/format-staged.js
+++ b/scripts/format-staged.js
@@ -61,6 +61,9 @@ function resolveOxfmtCommand(repoRoot) {
   const binName = process.platform === "win32" ? "oxfmt.cmd" : "oxfmt";
   const local = path.join(repoRoot, "node_modules", ".bin", binName);
   if (fs.existsSync(local)) {
+    if (process.platform === "win32" && local.toLowerCase().endsWith(".cmd")) {
+      return { command: "cmd.exe", args: ["/d", "/s", "/c", local] };
+    }
     return { command: local, args: [] };
   }
 
diff --git a/src/agents/cli-runner/helpers.ts b/src/agents/cli-runner/helpers.ts
index 833771a1f..94e9a4d8f 100644
--- a/src/agents/cli-runner/helpers.ts
+++ b/src/agents/cli-runner/helpers.ts
@@ -13,6 +13,7 @@ import type { EmbeddedContextFile } from "../pi-embedded-helpers.js";
 import { buildSystemPromptParams } from "../system-prompt-params.js";
 import { resolveDefaultModelForAgent } from "../model-selection.js";
 import { buildAgentSystemPrompt } from "../system-prompt.js";
+import { detectRuntimeShell } from "../shell-utils.js";
 import { buildTtsSystemPromptHint } from "../../tts/tts.js";
 
 const CLI_RUN_QUEUE = new Map<string, Promise<unknown>>();
@@ -193,6 +194,7 @@ export function buildSystemPrompt(params: {
       node: process.version,
       model: params.modelDisplay,
       defaultModel: defaultModelLabel,
+      shell: detectRuntimeShell(),
     },
   });
   const ttsHint = params.config ? buildTtsSystemPromptHint(params.config) : undefined;
diff --git a/src/agents/pi-embedded-runner/compact.ts b/src/agents/pi-embedded-runner/compact.ts
index dc68561c2..91786ebc2 100644
--- a/src/agents/pi-embedded-runner/compact.ts
+++ b/src/agents/pi-embedded-runner/compact.ts
@@ -67,6 +67,7 @@ import { buildEmbeddedSystemPrompt, createSystemPromptOverride } from "./system-
 import { splitSdkTools } from "./tool-split.js";
 import type { EmbeddedPiCompactResult } from "./types.js";
 import { formatUserTime, resolveUserTimeFormat, resolveUserTimezone } from "../date-time.js";
+import { detectRuntimeShell } from "../shell-utils.js";
 import { describeUnknownError, mapThinkingLevel, resolveExecToolDefaults } from "./utils.js";
 import { buildTtsSystemPromptHint } from "../../tts/tts.js";
 
@@ -300,6 +301,7 @@ export async function compactEmbeddedPiSessionDirect(
       arch: os.arch(),
       node: process.version,
       model: `${provider}/${modelId}`,
+      shell: detectRuntimeShell(),
       channel: runtimeChannel,
       capabilities: runtimeCapabilities,
       channelActions,
diff --git a/src/agents/pi-embedded-runner/run/attempt.ts b/src/agents/pi-embedded-runner/run/attempt.ts
index 46a53bd8f..3e62233b7 100644
--- a/src/agents/pi-embedded-runner/run/attempt.ts
+++ b/src/agents/pi-embedded-runner/run/attempt.ts
@@ -77,6 +77,7 @@ import { buildEmbeddedSystemPrompt, createSystemPromptOverride } from "../system
 import { splitSdkTools } from "../tool-split.js";
 import { toClientToolDefinitions } from "../../pi-tool-definition-adapter.js";
 import { buildSystemPromptParams } from "../../system-prompt-params.js";
+import { detectRuntimeShell } from "../../shell-utils.js";
 import { describeUnknownError, mapThinkingLevel } from "../utils.js";
 import { resolveSandboxRuntimeStatus } from "../../sandbox/runtime-status.js";
 import { buildTtsSystemPromptHint } from "../../../tts/tts.js";
@@ -319,6 +320,7 @@ export async function runEmbeddedAttempt(
         node: process.version,
         model: `${params.provider}/${params.modelId}`,
         defaultModel: defaultModelLabel,
+        shell: detectRuntimeShell(),
         channel: runtimeChannel,
         capabilities: runtimeCapabilities,
         channelActions,
diff --git a/src/agents/shell-utils.ts b/src/agents/shell-utils.ts
index 6d4efac59..2bb2c73d1 100644
--- a/src/agents/shell-utils.ts
+++ b/src/agents/shell-utils.ts
@@ -59,6 +59,42 @@ function resolveShellFromPath(name: string): string | undefined {
   return undefined;
 }
 
+function normalizeShellName(value: string): string {
+  const trimmed = value.trim();
+  if (!trimmed) return "";
+  return path.basename(trimmed).replace(/\.(exe|cmd|bat)$/i, "");
+}
+
+export function detectRuntimeShell(): string | undefined {
+  const overrideShell = process.env.CLAWDBOT_SHELL?.trim();
+  if (overrideShell) {
+    const name = normalizeShellName(overrideShell);
+    if (name) return name;
+  }
+
+  if (process.platform === "win32") {
+    if (process.env.POWERSHELL_DISTRIBUTION_CHANNEL) {
+      return "pwsh";
+    }
+    return "powershell";
+  }
+
+  const envShell = process.env.SHELL?.trim();
+  if (envShell) {
+    const name = normalizeShellName(envShell);
+    if (name) return name;
+  }
+
+  if (process.env.POWERSHELL_DISTRIBUTION_CHANNEL) return "pwsh";
+  if (process.env.BASH_VERSION) return "bash";
+  if (process.env.ZSH_VERSION) return "zsh";
+  if (process.env.FISH_VERSION) return "fish";
+  if (process.env.KSH_VERSION) return "ksh";
+  if (process.env.NU_VERSION || process.env.NUSHELL_VERSION) return "nu";
+
+  return undefined;
+}
+
 export function sanitizeBinaryOutput(text: string): string {
   const scrubbed = text.replace(/[\p{Format}\p{Surrogate}]/gu, "");
   if (!scrubbed) return scrubbed;
diff --git a/src/agents/system-prompt-params.ts b/src/agents/system-prompt-params.ts
index 276203ecb..499b28059 100644
--- a/src/agents/system-prompt-params.ts
+++ b/src/agents/system-prompt-params.ts
@@ -17,6 +17,7 @@ export type RuntimeInfoInput = {
   node: string;
   model: string;
   defaultModel?: string;
+  shell?: string;
   channel?: string;
   capabilities?: string[];
   /** Supported message actions for the current channel (e.g., react, edit, unsend) */
diff --git a/src/agents/system-prompt.ts b/src/agents/system-prompt.ts
index ed97fd539..6d7fd2a06 100644
--- a/src/agents/system-prompt.ts
+++ b/src/agents/system-prompt.ts
@@ -155,6 +155,7 @@ export function buildAgentSystemPrompt(params: {
     node?: string;
     model?: string;
     defaultModel?: string;
+    shell?: string;
     channel?: string;
     capabilities?: string[];
     repoRoot?: string;
@@ -562,6 +563,7 @@ export function buildRuntimeLine(
     node?: string;
     model?: string;
     defaultModel?: string;
+    shell?: string;
     repoRoot?: string;
   },
   runtimeChannel?: string,
@@ -580,6 +582,7 @@ export function buildRuntimeLine(
     runtimeInfo?.node ? `node=${runtimeInfo.node}` : "",
     runtimeInfo?.model ? `model=${runtimeInfo.model}` : "",
     runtimeInfo?.defaultModel ? `default_model=${runtimeInfo.defaultModel}` : "",
+    runtimeInfo?.shell ? `shell=${runtimeInfo.shell}` : "",
     runtimeChannel ? `channel=${runtimeChannel}` : "",
     runtimeChannel
       ? `capabilities=${runtimeCapabilities.length > 0 ? runtimeCapabilities.join(",") : "none"}`