diff --git a/etc.jl b/etc.jl
index 5d9b549..46735d2 100644
--- a/etc.jl
+++ b/etc.jl
@@ -1,28 +1,272 @@
-
-
-
-using Base.Threads
-
-println("Active Julia threads: ", nthreads())
-
-# A CPU-heavy helper function
-function compute_work(id, iterations)
-    println("  [Start] Task $id on Thread #", threadid())
-    
-    total = 0.0
-    for i in 1:iterations
-        total += sin(i) * cos(i)
-    end
-    
-    println("  [Done]  Task $id on Thread #", threadid())
-    return total
+struct preparedToolCall
+    tool::AgentTool
+    toolCall::AgentToolCall
+    args::Any
 end
 
-# ====================================================================
-# 1. Basic @spawn and fetch
-# ====================================================================
-println("\n--- 1. Single Task Spawning ---")
+struct immediateOutcome
+    result::AgentToolResult
+    isError::Bool
+end
 
-# Threads.@spawn creates a Task and schedules it onto an available worker thread
-task1 = Threads.@spawn compute_work("A", 10_000_000)
-println(typeof(task1))
\ No newline at end of file
+struct executedOutcome
+    result::AgentToolResult
+    isError::Bool
+end
+
+struct finalizedOutcome
+    toolCall::AgentToolCall
+    result::AgentToolResult
+    isError::Bool
+end
+
+struct toolCallBatch
+    messages::Vector{ToolResultMessage}
+    terminate::Bool
+end
+
+# ── helpers ─────────────────────────────────────────────────────
+
+function createErrorToolResult(msg::String)::AgentToolResult
+    return AgentToolResult([TextContent("text", msg)], Dict{Any,Any}())
+end
+
+function createToolResultMessage(f::finalizedOutcome)::ToolResultMessage
+    return ToolResultMessage(
+        "toolResult", f.toolCall.id, f.toolCall.name,
+        f.result.content, f.result.details, f.result.usage,
+        get(f.result, :addedToolNames, String[]), f.isError, now_millis()
+    )
+end
+
+function shouldTerminate(batches::Vector{finalizedOutcome})::Bool
+    return !isempty(batches) && all(b -> b.result.terminate, batches)
+end
+
+# ── per-call preparation ────────────────────────────────────────
+
+function prepareToolCall(
+    context::AgentContext,
+    assistantMsg::AssistantMessage,
+    toolCall::AgentToolCall,
+    config::AgentLoopConfig,
+    signal::Union{Nothing,AbortSignal},
+)::Union{preparedToolCall,immediateOutcome}
+
+    tool = find(t -> t.name == toolCall.name, context.tools)
+    if tool === nothing
+        return immediateOutcome(createErrorToolResult("Tool $toolCall.name not found"), true)
+    end
+
+    try
+        # 1. prepare arguments (tool-specific transform)
+        preparedArgs = prepareToolCallArguments(tool, toolCall)
+        validatedArgs = validateToolArguments(tool, preparedArgs)
+
+        # 2. beforeToolCall hook
+        if config.before_tool_call !== nothing
+            before = config.before_tool_call(
+                AssistantMsgCtx(assistantMsg, toolCall, validatedArgs, context), signal
+            )
+            if signal !== nothing && signal.aborted
+                return immediateOutcome(createErrorToolResult("Operation aborted"), true)
+            end
+            if before !== nothing && before.block
+                return immediateOutcome(
+                    createErrorToolResult(get(before, :reason, "Tool execution was blocked")), true)
+            end
+        end
+
+        return preparedToolCall(tool, toolCall, validatedArgs)
+    catch err
+        return immediateOutcome(createErrorToolResult(sprint(showerror, err)), true)
+    end
+end
+
+# ── per-call execution ──────────────────────────────────────────
+
+function executePreparedToolCall(
+    prep::preparedToolCall,
+    signal::Union{Nothing,AbortSignal},
+    emit::AgentEventSink,
+)::executedOutcome
+
+    updateEvents = Promise[]
+    accepting = true
+
+    try
+        result = prep.tool.execute(
+            prep.toolCall.id, prep.args, signal,
+            partialResult -> begin
+                if accepting
+                    push!(updateEvents,
+                          emit(ToolExecUpdateEvent(prep.toolCall.id, prep.toolCall.name,
+                                                   prep.toolCall.arguments, partialResult)))
+                end
+            end
+        )
+        accepting = false
+        wait.(updateEvents)
+        return executedOutcome(result, false)
+    catch err
+        accepting = false
+        wait.(updateEvents)
+        return executedOutcome(createErrorToolResult(sprint(showerror, err)), true)
+    end
+end
+
+# ── per-call finalization ───────────────────────────────────────
+
+function finalizeExecutedToolCall(
+    context::AgentContext,
+    assistantMsg::AssistantMessage,
+    prep::preparedToolCall,
+    executed::executedOutcome,
+    config::AgentLoopConfig,
+    signal::Union{Nothing,AbortSignal},
+)::finalizedOutcome
+
+    result = executed.result
+    isError = executed.isError
+
+    if config.afterToolCalls !== nothing
+        try
+            after = config.afterToolCalls(
+                AfterCtx(assistantMsg, prep.toolCall, prep.args, result, isError, context), signal
+            )
+            if after !== nothing
+                result = merge(result, Dict(:content=>get(after,:content,result.content),
+                                            :details=>get(after,:details,result.details),
+                                            :usage=>get(after,:usage,result.usage),
+                                            :terminate=>get(after,:terminate,result.terminate)))
+                isError = get(after, :is_error, isError)
+            end
+        catch err
+            result = createErrorToolResult(sprint(showerror, err))
+            isError = true
+        end
+    end
+
+    return finalizedOutcome(prep.toolCall, result, isError)
+end
+
+function emitToolExecutionEnd(finalized::finalizedOutcome, emit::AgentEventSink)
+    emit(ToolExecEndEvent(finalized.toolCall.id, finalized.toolCall.name,
+                          finalized.result, finalized.isError))
+end
+
+# ── sequential execution ────────────────────────────────────────
+
+function executeToolCallsSequential(
+    context::AgentContext,
+    assistantMsg::AssistantMessage,
+    toolCalls::Vector{AgentToolCall},
+    config::AgentLoopConfig,
+    signal::Union{Nothing,AbortSignal},
+    emit::AgentEventSink,
+)::toolCallBatch
+
+    finalizedCalls = finalizedOutcome[]
+    messages = ToolResultMessage[]
+
+    for tc in toolCalls
+        emit(ToolExecStartEvent(tc.id, tc.name, tc.arguments))
+
+        prep = prepareToolCall(context, assistantMsg, tc, config, signal)
+
+        if prep isa immediateOutcome
+            finalized = finalizedOutcome(tc, prep.result, prep.isError)
+        else
+            executed = executePreparedToolCall(prep, signal, emit)
+            finalized = finalizeExecutedToolCall(context, assistantMsg, prep, executed, config, signal)
+        end
+
+        emitToolExecutionEnd(finalized, emit)
+        push!(messages, createToolResultMessage(finalized))
+        push!(finalizedCalls, finalized)
+
+        if signal !== nothing && signal.aborted
+            break
+        end
+    end
+
+    return toolCallBatch(messages, shouldTerminate(finalizedCalls))
+end
+
+# ── parallel execution ──────────────────────────────────────────
+
+function executeToolCallsParallel(
+    context::AgentContext,
+    assistantMsg::AssistantMessage,
+    toolCalls::Vector{AgentToolCall},
+    config::AgentLoopConfig,
+    signal::Union{Nothing,AbortSignal},
+    emit::AgentEventSink,
+)::toolCallBatch
+
+    # Each entry: finalizedOutcome (already done) or Task → finalizedOutcome (pending)
+    entries = Union{finalizedOutcome,Task{finalizedOutcome}}[]
+
+    for tc in toolCalls
+        emit(ToolExecStartEvent(tc.id, tc.name, tc.arguments))
+
+        prep = prepareToolCall(context, assistantMsg, tc, config, signal)
+
+        if prep isa immediateOutcome
+            finalized = finalizedOutcome(tc, prep.result, prep.isError)
+            emitToolExecutionEnd(finalized, emit)
+            push!(entries, finalized)
+        else
+            # spawn lazy computation task
+            task = Task() do
+                executed = executePreparedToolCall(prep, signal, emit)
+                finalized = finalizeExecutedToolCall(context, assistantMsg, prep, executed, config, signal)
+                emitToolExecutionEnd(finalized, emit)
+                return finalized
+            end
+            schedule(task)
+            push!(entries, task)
+        end
+
+        if signal !== nothing && signal.aborted
+            break
+        end
+    end
+
+    # Wait for all tasks, collect in order
+    finalizedCalls = finalizedOutcome[]
+    for entry in entries
+        outcome = entry isa Task ? fetch(entry) : entry
+        push!(finalizedCalls, outcome)
+    end
+
+    messages = ToolResultMessage[]
+    for f in finalizedCalls
+        push!(messages, createToolResultMessage(f))
+    end
+
+    return toolCallBatch(messages, shouldTerminate(finalizedCalls))
+end
+
+# ── dispatcher ──────────────────────────────────────────────────
+
+function executeToolCalls(
+    context::AgentContext,
+    assistantMsg::AssistantMessage,
+    toolCalls::Vector{AgentToolCall},
+    config::AgentLoopConfig,
+    signal::Union{Nothing,AbortSignal},
+    emit::AgentEventSink,
+)::toolCallBatch
+
+    # Check if any tool is marked sequential, or config forces sequential
+    hasSequential = any(tc ->
+        any(t -> t.name == tc.name && get(t.executionMode, "parallel") == "sequential",
+            context.tools), toolCalls)
+
+    if config.tool_execution == "sequential" || hasSequential
+        return executeToolCallsSequential(context, assistantMsg, toolCalls, config, signal, emit)
+    else
+        return executeToolCallsParallel(context, assistantMsg, toolCalls, config, signal, emit)
+    end
+end
diff --git a/src/agentCore.jl b/src/agentCore.jl
index c2656c2..71f3bdb 100644
--- a/src/agentCore.jl
+++ b/src/agentCore.jl
@@ -176,7 +176,7 @@ julia> # Currently returns a placeholder echo response
 function _process_message(agent::yiemAgent, msg)::assistantMessage
   # WORKING 
 
-  # loop until LLM didn't use tool calls
+  # loop until llmCall() response didn't use tool calls
   while 
     # take every messages from agent.inputChannel, convert them into userMessage 
     # and add them to agent._state.messages
@@ -185,11 +185,15 @@ function _process_message(agent::yiemAgent, msg)::assistantMessage
 
     # Call agent.formatMsgForLLM(agent._state) to format for LLM
 
-    # Call the LLM (blocking — the task waits here)
+    # Call llmCall() (blocking — the task waits here)
 
-    # call toolArgumentValidation() to make sure soon-to-call tools has valid arguments
+    # if LLM use tool calls
 
-    # If agent has tools, handle tool calls in a loop, save tool
+      # call executeToolCalls()
+
+    # else
+      # break out of while loop
+      
   end
 
   # Build assistantMessage and return it
@@ -207,9 +211,7 @@ function _process_message(agent::yiemAgent, msg)::assistantMessage
 end
 
 
-function createToolResultMessage()::toolResultMessage
-  
-end
+
 
 
 
diff --git a/src/type.jl b/src/type.jl
index bf6e0ce..71276fe 100644
--- a/src/type.jl
+++ b/src/type.jl
@@ -386,7 +386,7 @@ mutable struct yiemAgent <: agent             # High-level agent wrapper
   # Callback invoked before executing a tool call (ask for user permission/confirmation/abort, etc..)
   beforeToolCall::Union{Function, Nothing}    
 
-  executeToolCalls::Function                  # execute tool calls
+  executeToolCalls::Function                  # execute tool calls ()
   
   # Callback invoked after executing a tool call to sanitize tools output so the output is ready 
   # to be converted into toolResults message