Index: src/ai/ai.hpp
===================================================================
--- src/ai/ai.hpp	(revision 18960)
+++ src/ai/ai.hpp	(working copy)
@@ -64,6 +64,8 @@
 	 */
 	static void Stop(CompanyID company);
 
+	static void Suspend(CompanyID company);
+
 	/**
 	 * Kill any and all AIs we manage.
 	 */
Index: src/ai/ai_core.cpp
===================================================================
--- src/ai/ai_core.cpp	(revision 18960)
+++ src/ai/ai_core.cpp	(working copy)
@@ -108,6 +108,21 @@
 	DeleteWindowById(WC_AI_SETTINGS, company);
 }
 
+/* static */ void AI::Suspend(CompanyID company)
+{
+	if (_networking && !_network_server) return;
+
+	CompanyID old_company = _current_company;
+	_current_company = company;
+	Company *c = Company::Get(company);
+
+	c->ai_instance->Suspend();
+
+	_current_company = old_company;
+
+	InvalidateWindowData(WC_AI_DEBUG, 0, -1);
+}
+
 /* static */ void AI::KillAll()
 {
 	/* It might happen there are no companies .. than we have nothing to loop */
Index: src/ai/ai_gui.cpp
===================================================================
--- src/ai/ai_gui.cpp	(revision 18960)
+++ src/ai/ai_gui.cpp	(working copy)
@@ -13,6 +13,7 @@
 #include "../openttd.h"
 #include "../gui.h"
 #include "../window_gui.h"
+#include "../querystring_gui.h"
 #include "../company_func.h"
 #include "../company_base.h"
 #include "../company_gui.h"
@@ -24,6 +25,7 @@
 #include "../textbuf_gui.h"
 #include "../settings_func.h"
 #include "../network/network_content.h"
+#include "../openttd.h"
 
 #include "ai.hpp"
 #include "api/ai_log.hpp"
@@ -701,12 +703,14 @@
 	AID_WIDGET_SCROLLBAR,
 	AID_WIDGET_COMPANY_BUTTON_START,
 	AID_WIDGET_COMPANY_BUTTON_END = AID_WIDGET_COMPANY_BUTTON_START + 14,
+	AID_WIDGET_BREAK_POINT_EDIT_BOX,
+	AID_WIDGET_CONTINUE_BTN,
 };
 
 /**
  * Window with everything an AI prints via AILog.
  */
-struct AIDebugWindow : public Window {
+struct AIDebugWindow : public QueryStringBaseWindow {
 	static const int top_offset;    ///< Offset of the text at the top of the #AID_WIDGET_LOG_PANEL.
 	static const int bottom_offset; ///< Offset of the text at the bottom of the #AID_WIDGET_LOG_PANEL.
 
@@ -715,7 +719,9 @@
 	int last_vscroll_pos;
 	bool autoscroll;
 
-	AIDebugWindow(const WindowDesc *desc, WindowNumber number) : Window()
+	static const unsigned int MAX_BREAK_POINT_STRING_LENGTH = 256;
+
+	AIDebugWindow(const WindowDesc *desc, WindowNumber number) : QueryStringBaseWindow(MAX_BREAK_POINT_STRING_LENGTH)
 	{
 		this->InitNested(desc, number);
 		/* Disable the companies who are not active or not an AI */
@@ -724,9 +730,11 @@
 		}
 		this->DisableWidget(AID_WIDGET_RELOAD_TOGGLE);
 		this->DisableWidget(AID_WIDGET_SETTINGS);
+		this->DisableWidget(AID_WIDGET_CONTINUE_BTN);
 
 		this->last_vscroll_pos = 0;
 		this->autoscroll = true;
+		InitializeTextBuffer(&this->text, this->edit_str_buf, this->edit_str_size, MAX_BREAK_POINT_STRING_LENGTH);
 
 		if (ai_debug_company != INVALID_COMPANY) this->LowerWidget(ai_debug_company + AID_WIDGET_COMPANY_BUTTON_START);
 	}
@@ -774,6 +782,8 @@
 
 		if (this->IsShaded()) return; // Don't draw anything when the window is shaded.
 
+		this->DrawEditBox(AID_WIDGET_BREAK_POINT_EDIT_BOX);
+
 		/* If there are no active companies, don't display anything else. */
 		if (ai_debug_company == INVALID_COMPANY) return;
 
@@ -931,6 +941,13 @@
 			case AID_WIDGET_SETTINGS:
 				ShowAISettingsWindow(ai_debug_company);
 				break;
+
+			case AID_WIDGET_CONTINUE_BTN:
+				/* Unpause */
+				DoCommand(0, PM_PAUSED_NORMAL, 0, DC_EXEC, CMD_PAUSE);
+				this->DisableWidget(AID_WIDGET_CONTINUE_BTN);
+				this->RaiseWidget(AID_WIDGET_CONTINUE_BTN); // Disabled widgets doesn't raise themself
+				break;
 		}
 	}
 
@@ -941,9 +958,61 @@
 		this->SetDirty();
 	}
 
+	virtual void OnMouseLoop()
+	{
+		this->HandleEditBox(AID_WIDGET_BREAK_POINT_EDIT_BOX);
+
+		/* Zuu: [regarding this patch] I think this check is a bit expansive. 
+		 *      Or at least there will be many many unnecessary checks. Maybe
+		 *      there is some code somewhere that is executed only when pause
+		 *      state changes. That code could ivalidate data of this window
+		 *      with data parameter := -2.
+		 *      .. or the continue button is completely removed. However it is
+		 *      a nice visual clue that the game has been paused.
+		 */
+
+		/* The continue button should be disabled when the game is unpaused */
+		if ((_pause_mode & PM_PAUSED_NORMAL) == PM_UNPAUSED) {
+			this->DisableWidget(AID_WIDGET_CONTINUE_BTN);
+			this->SetWidgetDirty(AID_WIDGET_CONTINUE_BTN);
+		}
+	}
+
+	virtual EventState OnKeyPress(uint16 key, uint16 keycode)
+	{
+		EventState state;
+		this->HandleEditBoxKey(AID_WIDGET_BREAK_POINT_EDIT_BOX, key, keycode, state);
+		return state;
+	}
+
 	virtual void OnInvalidateData(int data = 0)
 	{
 		if (data == -1 || ai_debug_company == data) this->SetDirty();
+
+		/* If the log message is related to the active company tab, check the break string */
+		if (data == ai_debug_company && !StrEmpty(this->edit_str_buf))
+		{
+			/* Get the log instance of the active company */
+			CompanyID old_company = _current_company;
+			_current_company = ai_debug_company;
+			AILog::LogData *log = (AILog::LogData *)AIObject::GetLogPointer();
+			_current_company = old_company;
+			if(log != NULL)
+			{
+				if(strstr(log->lines[log->pos], this->edit_str_buf) != 0)
+				{
+					// the break string was found in the last log mesage -> pause
+					if ((_pause_mode & PM_PAUSED_NORMAL) == PM_UNPAUSED) {
+						AI::Suspend(ai_debug_company);
+						DoCommand(0, PM_PAUSED_NORMAL, 1, DC_EXEC, CMD_PAUSE);
+
+						/* Make it possible to click on the continue button */
+						this->EnableWidget(AID_WIDGET_CONTINUE_BTN);
+						this->SetWidgetDirty(AID_WIDGET_CONTINUE_BTN);
+					}
+				}
+			}
+		}
 	}
 
 	virtual void OnResize()
@@ -1012,8 +1081,13 @@
 	NWidget(NWID_HORIZONTAL),
 		NWidget(WWT_PANEL, COLOUR_GREY, AID_WIDGET_LOG_PANEL), SetMinimalSize(287, 180), SetResize(1, 1),
 		EndContainer(),
-		NWidget(NWID_VERTICAL),
-			NWidget(WWT_SCROLLBAR, COLOUR_GREY, AID_WIDGET_SCROLLBAR),
+		NWidget(WWT_SCROLLBAR, COLOUR_GREY, AID_WIDGET_SCROLLBAR),
+	EndContainer(),	
+	NWidget(WWT_PANEL, COLOUR_GREY),
+		NWidget(NWID_HORIZONTAL),
+			NWidget(WWT_LABEL, COLOUR_GREY), SetPadding(0, 4, 0, 4), SetDataTip(STR_AI_DEBUG_BREAK_ON_LABEL, 0x0),
+			NWidget(WWT_EDITBOX, COLOUR_WHITE, AID_WIDGET_BREAK_POINT_EDIT_BOX), SetFill(1, 1), SetResize(1, 0), SetDataTip(STR_AI_DEBUG_BREAK_POINT_OSKTITLE, STR_AI_DEBUG_BREAK_POINT_TOOLTIP),
+			NWidget(WWT_PUSHTXTBTN, COLOUR_GREY, AID_WIDGET_CONTINUE_BTN), SetDataTip(STR_AI_DEBUG_CONTINUE, STR_AI_DEBUG_CONTINUE_TOOLTIP),
 			NWidget(WWT_RESIZEBOX, COLOUR_GREY),
 		EndContainer(),
 	EndContainer(),
Index: src/ai/ai_instance.cpp
===================================================================
--- src/ai/ai_instance.cpp	(revision 18960)
+++ src/ai/ai_instance.cpp	(working copy)
@@ -658,6 +658,16 @@
 
 }
 
+void AIInstance::Suspend()
+{
+	if (this->engine->CanSuspend()) {
+		HSQUIRRELVM vm = this->engine->GetVM();
+		const int big_number = 100000;
+		sq_decreaseops(vm, big_number);
+		//this->sq_suspendvm(vm);
+	}
+}
+
 /* static */ bool AIInstance::LoadObjects(HSQUIRRELVM vm)
 {
 	SlObject(NULL, _ai_byte);
Index: src/ai/ai_instance.hpp
===================================================================
--- src/ai/ai_instance.hpp	(revision 18960)
+++ src/ai/ai_instance.hpp	(working copy)
@@ -137,6 +137,7 @@
 	 */
 	static void LoadEmpty();
 
+	void Suspend();
 private:
 	class AIController *controller;
 	class AIStorage *storage;
Index: src/lang/english.txt
===================================================================
--- src/lang/english.txt	(revision 18960)
+++ src/lang/english.txt	(working copy)
@@ -3217,6 +3217,11 @@
 STR_AI_DEBUG_SETTINGS_TOOLTIP                                   :{BLACK}Change the settings of the AI
 STR_AI_DEBUG_RELOAD                                             :{BLACK}Reload AI
 STR_AI_DEBUG_RELOAD_TOOLTIP                                     :{BLACK}Kill the AI, reload the script, and restart the AI
+STR_AI_DEBUG_BREAK_ON_LABEL                                     :{BLACK}Break on:
+STR_AI_DEBUG_BREAK_POINT_OSKTITLE                               :{BLACK}Break on
+STR_AI_DEBUG_BREAK_POINT_TOOLTIP                                :{BLACK}When an AILog message matches this string, the game is paused.
+STR_AI_DEBUG_CONTINUE                                           :{BLACK}Continue
+STR_AI_DEBUG_CONTINUE_TOOLTIP                                   :{BLACK}Unpause and continue the AI
 
 STR_ERROR_AI_NO_AI_FOUND                                        :No suitable AI found to load.{}This AI is a dummy AI and won't do anything.{}You can download several AIs via the 'Online Content' system.
 STR_ERROR_AI_PLEASE_REPORT_CRASH                                :{WHITE}One of the running AIs crashed. Please report this to the AI author with a screenshot of the AI Debug Window.