diff --git a/packages/core/src/prompts/snippets.ts b/packages/core/src/prompts/snippets.ts
index b049ddf58e..0fbb6b8872 100644
--- a/packages/core/src/prompts/snippets.ts
+++ b/packages/core/src/prompts/snippets.ts
@@ -806,8 +806,7 @@ function toolUsageInteractive(
 function toolUsageAiShell(options: OperationalGuidelinesOptions): string {
   if (options.interactiveShellMode !== 'ai') return '';
   return `
-- **AI-Driven Interactive Shell:** Commands using \`wait_for_output_seconds\` auto-promote to background when they stall. Once promoted, use ${formatToolName(READ_SHELL_TOOL_NAME)} to see the terminal screen, then ${formatToolName(WRITE_TO_SHELL_TOOL_NAME)} to send text input and/or special keys (arrows, Enter, Ctrl-C, etc.).
-  - Set \`wait_for_output_seconds\` **low (2-5)** for commands that prompt for input (npx, installers, REPLs). Set **high (60+)** for long builds. Omit for instant commands.
+- **AI-Driven Interactive Shell:** Commands auto-promote to background if they stall for 3 seconds. Once promoted, use ${formatToolName(READ_SHELL_TOOL_NAME)} to see the terminal screen, then ${formatToolName(WRITE_TO_SHELL_TOOL_NAME)} to send text input and/or special keys (arrows, Enter, Ctrl-C, etc.).
   - **Always read the screen before writing input.** The screen state tells you what the process is waiting for.
   - When waiting for a command to finish (e.g. npm install), use ${formatToolName(READ_SHELL_TOOL_NAME)} with \`wait_seconds\` to delay before reading. Do NOT poll in a tight loop.
   - **Clean up when done:** when your task is complete, kill background processes with ${formatToolName(WRITE_TO_SHELL_TOOL_NAME)} sending Ctrl-C, or note the PID for the user to clean up.
diff --git a/packages/core/src/tools/definitions/base-declarations.ts b/packages/core/src/tools/definitions/base-declarations.ts
index e1575966af..47e57ec8ab 100644
--- a/packages/core/src/tools/definitions/base-declarations.ts
+++ b/packages/core/src/tools/definitions/base-declarations.ts
@@ -56,7 +56,6 @@ export const READ_FILE_PARAM_END_LINE = 'end_line';
 export const SHELL_TOOL_NAME = 'run_shell_command';
 export const SHELL_PARAM_COMMAND = 'command';
 export const SHELL_PARAM_IS_BACKGROUND = 'is_background';
-export const SHELL_PARAM_WAIT_SECONDS = 'wait_for_output_seconds';
 
 // -- write_to_shell --
 export const WRITE_TO_SHELL_TOOL_NAME = 'write_to_shell';
diff --git a/packages/core/src/tools/definitions/coreTools.ts b/packages/core/src/tools/definitions/coreTools.ts
index a70ed1a33c..18ed26ea58 100644
--- a/packages/core/src/tools/definitions/coreTools.ts
+++ b/packages/core/src/tools/definitions/coreTools.ts
@@ -75,7 +75,6 @@ export {
   LS_PARAM_IGNORE,
   SHELL_PARAM_COMMAND,
   SHELL_PARAM_IS_BACKGROUND,
-  SHELL_PARAM_WAIT_SECONDS,
   WRITE_TO_SHELL_PARAM_PID,
   WRITE_TO_SHELL_PARAM_INPUT,
   WRITE_TO_SHELL_PARAM_SPECIAL_KEYS,
diff --git a/packages/core/src/tools/definitions/dynamic-declaration-helpers.ts b/packages/core/src/tools/definitions/dynamic-declaration-helpers.ts
index 6f001c7459..cade647893 100644
--- a/packages/core/src/tools/definitions/dynamic-declaration-helpers.ts
+++ b/packages/core/src/tools/definitions/dynamic-declaration-helpers.ts
@@ -22,7 +22,6 @@ import {
   PARAM_DIR_PATH,
   SHELL_PARAM_IS_BACKGROUND,
   EXIT_PLAN_PARAM_PLAN_FILENAME,
-  SHELL_PARAM_WAIT_SECONDS,
   SKILL_PARAM_NAME,
   PARAM_ADDITIONAL_PERMISSIONS,
   UPDATE_TOPIC_TOOL_NAME,
@@ -60,7 +59,7 @@ export function getShellToolDescription(
       Process Group PGID: Only included if available.`;
 
   if (isAiMode) {
-    const autoPromoteInstructions = `Commands that do not complete within \`${SHELL_PARAM_WAIT_SECONDS}\` seconds are automatically promoted to background. Once promoted, use \`write_to_shell\` and \`read_shell\` to interact with the process. Do NOT use \`&\` to background commands.`;
+    const autoPromoteInstructions = `Commands that do not complete within 3 seconds are automatically promoted to background. Once promoted, use \`write_to_shell\` and \`read_shell\` to interact with the process. Do NOT use \`&\` to background commands.`;
     return `This tool executes a given shell command as \`bash -c <command>\`. ${autoPromoteInstructions} Command is executed as a subprocess that leads its own process group. Command process group can be terminated as \`kill -- -PGID\` or signaled as \`kill -s SIGNAL -- -PGID\`.${efficiencyGuidelines}${returnedInfo}`;
   }
 
@@ -98,15 +97,9 @@ export function getShellDeclaration(
 ): FunctionDeclaration {
   const isAiMode = interactiveShellMode === 'ai';
 
-  // In AI mode, use wait_for_output_seconds instead of is_background
+  // In AI mode, auto-promotion is enabled by default, no background param needed
   const backgroundParam = isAiMode
-    ? {
-        [SHELL_PARAM_WAIT_SECONDS]: {
-          type: 'number' as const,
-          description:
-            'Max seconds to wait for command to complete before auto-promoting to background (default: 5). Set low (2-5) for commands likely to prompt for input (npx, installers, REPLs). Set high (60-300) for long builds or installs. Once promoted, use write_to_shell/read_shell to interact.',
-        },
-      }
+    ? {}
     : {
         [SHELL_PARAM_IS_BACKGROUND]: {
           type: 'boolean' as const,
diff --git a/packages/core/src/tools/shell.ts b/packages/core/src/tools/shell.ts
index 053cc4b00d..66e61841f6 100644
--- a/packages/core/src/tools/shell.ts
+++ b/packages/core/src/tools/shell.ts
@@ -72,7 +72,6 @@ export interface ShellToolParams {
   is_background?: boolean;
   delay_ms?: number;
   [PARAM_ADDITIONAL_PERMISSIONS]?: SandboxPermissions;
-  wait_for_output_seconds?: number;
 }
 
 export class ShellToolInvocation extends BaseToolInvocation<
@@ -228,8 +227,8 @@ export class ShellToolInvocation extends BaseToolInvocation<
   override getExplanation(): string {
     let explanation = this.getContextualDetails().trim();
     const isAiMode = this.context.config.getInteractiveShellMode() === 'ai';
-    if (this.params.wait_for_output_seconds !== undefined || isAiMode) {
-      explanation += ` [auto-background after ${this.params.wait_for_output_seconds ?? 5}s]`;
+    if (isAiMode) {
+      explanation += ` [auto-background after 3s]`;
     }
     return explanation;
   }
@@ -507,9 +506,8 @@ export class ShellToolInvocation extends BaseToolInvocation<
 
       let currentPid: number | undefined;
       const isAiMode = this.context.config.getInteractiveShellMode() === 'ai';
-      const shouldAutoPromote =
-        this.params.wait_for_output_seconds !== undefined || isAiMode;
-      const waitMs = (this.params.wait_for_output_seconds ?? 5) * 1000;
+      const shouldAutoPromote = isAiMode;
+      const waitMs = isAiMode ? 3000 : 0;
 
       const resetAutoPromoteTimer = () => {
         if (shouldAutoPromote && currentPid) {
@@ -650,7 +648,7 @@ export class ShellToolInvocation extends BaseToolInvocation<
           }
         }
 
-        // In AI mode with wait_for_output_seconds, set up auto-promotion timer.
+        // In AI mode, set up auto-promotion timer.
         // When the timer fires, promote to background instead of cancelling.
         currentPid = pid;
         resetAutoPromoteTimer();
diff --git a/packages/core/src/tools/write-to-shell.ts b/packages/core/src/tools/write-to-shell.ts
index 652cb31bf5..2ac6862cab 100644
--- a/packages/core/src/tools/write-to-shell.ts
+++ b/packages/core/src/tools/write-to-shell.ts
@@ -167,7 +167,7 @@ export class WriteToShellTool extends BaseDeclarativeTool<
     super(
       WriteToShellTool.Name,
       'WriteToShell',
-      'Sends input to a running background shell process. Use this to interact with TUI applications, REPLs, and interactive commands. After writing, the current screen state is returned. Works with processes that were auto-promoted to background via wait_for_output_seconds or started with is_background=true.',
+      'Sends input to a running background shell process. Use this to interact with TUI applications, REPLs, and interactive commands. After writing, the current screen state is returned. Works with processes that were auto-promoted to background or started with is_background=true.',
       Kind.Execute,
       {
         type: 'object',