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YiemAgent/learning/03-AGENTLOOP_COMPONENT.md
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2026-07-29 11:14:04 +07:00

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# AgentCore.jl - AgentLoop Component Deep Dive
## AgentLoop Architecture
```
┌─────────────────────────────────────────────────────────────────────────────┐
│ AgentLoop Layer │
└─────────────────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────────────────┐
│ Public API │
└─────────────────────────────────────────────────────────────────────────────┘
agentLoop()
├─ prompts: Vector{AgentMessage}
├─ context: AgentContext
├─ config: AgentLoopConfig
├─ signal: Union{Nothing, AbortSignal}
└─ stream_fn: StreamFn
└─ Returns: EventStream
agentLoopContinue()
├─ context: AgentContext
├─ config: AgentLoopConfig
├─ signal: Union{Nothing, AbortSignal}
└─ stream_fn: StreamFn
└─ Returns: EventStream
┌─────────────────────────────────────────────────────────────────────────────┐
│ Internal Flow │
└─────────────────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────────────────┐
│ 1. runAgentLoop() ── Entry point for new conversation │
│ - Creates copy of prompts │
│ - Appends prompts to context.messages │
│ - Emits AgentStartEvent │
│ - Emits TurnStartEvent │
│ - Emits MessageStart/End for each prompt │
│ - Calls runLoop() │
└─────────────────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────────────────┐
│ 2. runLoop() ── Main event loop │
│ ┌────────────────────────────────────────────────────────────────────┐ │
│ │ while true: │ │
│ │ 1. Get steering/follow-up messages (if any) │ │
│ │ 2. Emit messages as UserMessage │ │
│ │ 3. streamAssistantResponse() │ │
│ │ 4. Execute tool calls (sequential or parallel) │ │
│ │ 5. Emit TurnEndEvent │ │
│ │ 6. prepare_next_turn (optional) │ │
│ │ 7. should_stop_after_turn? (check termination) │ │
│ │ 8. Loop continues if not terminated │ │
│ └────────────────────────────────────────────────────────────────────┘ │
└─────────────────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────────────────┐
│ 3. streamAssistantResponse() ── LLM interaction │
│ - transform_context (optional) │
│ - convert_to_llm (transform to Message[]) │
│ - Call stream_fn (LLM API) │
│ - Stream response deltas │
│ - Emit MessageStart/Update/End events │
└─────────────────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────────────────┐
│ 4. executeToolCalls() ── Tool execution │
│ ┌────────────────────────────────────────────────────────────────────┐ │
│ │ if EXECUTION_SEQUENTIAL || has_sequential_tool: │ │
│ │ executeToolCallsSequential() │ │
│ │ else: │ │
│ │ executeToolCallsParallel() │ │
│ └────────────────────────────────────────────────────────────────────┘ │
└─────────────────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────────────────┐
│ 5. AgentEndEvent ── Final event with all messages │
└─────────────────────────────────────────────────────────────────────────────┘
```
## AgentLoopConfig
```julia
struct AgentLoopConfig
model::Model
reasoning::Union{ThinkingLevel, Nothing}
session_id::Union{String, Nothing}
on_payload::Union{Function, Nothing}
on_response::Union{Function, Nothing}
transport::String
thinking_budgets::Union{Dict{String, Int64}, Nothing}
max_retry_delay_ms::Union{Int64, Nothing}
tool_execution::ToolExecutionMode
before_tool_call::Union{Function, Nothing}
after_tool_call::Union{Function, Nothing}
prepare_next_turn::Union{Function, Nothing}
convert_to_llm::Function
transform_context::Union{Function, Nothing}
get_api_key::Union{Function, Nothing}
get_steering_messages::Union{Function, Nothing}
get_follow_up_messages::Union{Function, Nothing}
end
```
## Main Functions
### agentLoop()
```julia
function agentLoop(
prompts::Vector{AgentMessage},
context::AgentContext,
config::AgentLoopConfig,
signal::Union{Nothing, AbortSignal},
stream_fn::StreamFn,
)::EventStream
```
**Purpose**: Start a new conversation with initial prompts
**Flow**:
1. Create event stream
2. Spawn thread to run agent loop
3. Return stream for event consumption
```julia
stream = agentLoop(
[UserMessage("user", [TextContent("Hello")], timestamp)],
AgentContext(system_prompt, messages, tools),
config,
nothing,
stream_fn,
)
# Consume events
for event in stream
if event isa MessageEndEvent
println("Received: $(event.message)")
end
end
```
### runAgentLoop()
```julia
function runAgentLoop(
prompts::Vector{AgentMessage},
context::AgentContext,
config::AgentLoopConfig,
emit::AgentEventSink,
signal::Union{Nothing, AbortSignal},
stream_fn::StreamFn,
)::Vector{AgentMessage}
```
**Purpose**: Execute agent loop with initial prompts
**Flow**:
1. Copy prompts to new_messages
2. Append prompts to context.messages
3. Emit AgentStartEvent
4. For each prompt: emit MessageStartEvent, MessageEndEvent
5. Call runLoop()
### runLoop() - The Heart of AgentLoop
```julia
function runLoop(
initial_context::AgentContext,
new_messages::Vector{AgentMessage},
initial_config::AgentLoopConfig,
signal::Union{Nothing, AbortSignal},
emit::AgentEventSink,
stream_function::StreamFn,
)::Nothing
```
**Main Loop**:
```julia
current_context = initial_context
config = initial_config
first_turn = true
pending_messages = get_steering_messages()
while true
# Process steering/follow-up messages
while !isempty(pending_messages)
if !first_turn
emit(TurnStartEvent())
else
first_turn = false
end
# Emit pending messages
for message in pending_messages
emit(MessageStartEvent(message))
emit(MessageEndEvent(message))
push!(current_context.messages, message)
push!(new_messages, message)
end
pending_messages = []
end
# Stream assistant response
message = streamAssistantResponse(
current_context,
config,
signal,
emit,
stream_function,
)
push!(new_messages, message)
# Check for errors
if message.stop_reason in ("error", "aborted")
emit(TurnEndEvent(message, []))
emit(AgentEndEvent(new_messages))
return
end
# Execute tool calls
tool_calls = filter(c -> c isa ToolCall, message.content)
tool_results = []
has_more_tool_calls = false
if !isempty(tool_calls)
executed_batch = if message.stop_reason == "length"
failToolCallsFromTruncatedMessage(tool_calls, emit)
else
executeToolCalls(
current_context,
message,
config,
signal,
emit,
)
end
append!(tool_results, executed_batch.messages)
has_more_tool_calls = !executed_batch.terminate
for result in tool_results
push!(current_context.messages, result)
push!(new_messages, result)
end
end
emit(TurnEndEvent(message, tool_results))
# Prepare next turn (optional)
next_turn_context = PrepareNextTurnContext(
message, tool_results, current_context, new_messages
)
next_turn_snapshot = prepare_next_turn(config, next_turn_context)
if !isnothing(next_turn_snapshot)
current_context = next_turn_snapshot.context
config = AgentLoopConfig(
model = next_turn_snapshot.model,
reasoning = next_turn_snapshot.thinking_level,
# ... other config fields
)
end
# Check if should stop
if should_stop_after_turn(config, next_turn_context)
emit(AgentEndEvent(new_messages))
return
end
# Get next pending messages
pending_messages = get_steering_messages()
# Check follow-up messages
follow_up_messages = get_follow_up_messages()
if !isempty(follow_up_messages)
pending_messages = follow_up_messages
continue
end
break
end
emit(AgentEndEvent(new_messages))
```
### streamAssistantResponse()
```julia
function streamAssistantResponse(
context::AgentContext,
config::AgentLoopConfig,
signal::Union{Nothing, AbortSignal},
emit::AgentEventSink,
stream_function::StreamFn,
)::AssistantMessage
```
**Flow**:
1. Get messages from context
2. Apply transform_context (optional)
3. Convert to LLM messages with convert_to_llm
4. Create Context object
5. Resolve API key
6. Call stream_fn with model, context, and config
7. Stream events:
- "start" → MessageStartEvent
- "text_start", "text_delta", "text_end" → MessageUpdateEvent
- "done", "error" → MessageEndEvent
### executeToolCalls()
```julia
function executeToolCalls(
current_context::AgentContext,
assistant_message::AssistantMessage,
config::AgentLoopConfig,
signal::Union{Nothing, AbortSignal},
emit::AgentEventSink,
)::ExecutedToolCallBatch
```
**Logic**:
```julia
tool_calls = filter(c -> c isa ToolCall, assistant_message.content)
# Check if any tool requires sequential execution
has_sequential = any(tc -> begin
tool = findfirst(t -> t.name == tc.name, current_context.tools)
!isnothing(tool) && tool.execution_mode == EXECUTION_SEQUENTIAL
end, tool_calls)
# Determine execution mode
if config.tool_execution == EXECUTION_SEQUENTIAL || has_sequential
executeToolCallsSequential(...)
else
executeToolCallsParallel(...)
end
```
### executeToolCallsSequential()
```julia
function executeToolCallsSequential(
current_context::AgentContext,
assistant_message::AssistantMessage,
tool_calls::Vector{ToolCall},
config::AgentLoopConfig,
signal::Union{Nothing, AbortSignal},
emit::AgentEventSink,
)::ExecutedToolCallBatch
```
**Flow** (for each tool call):
1. Emit ToolExecutionStartEvent
2. prepareToolCall() → PreparedToolCall or ImmediateToolCallOutcome
3. If prepared: executePreparedToolCall()
4. finalizeExecutedToolCall()
5. Emit ToolExecutionEndEvent
6. Emit ToolResultMessage
7. Check if signal.aborted → break
### executeToolCallsParallel()
```julia
function executeToolCallsParallel(
current_context::AgentContext,
assistant_message::AssistantMessage,
tool_calls::Vector{ToolCall},
config::AgentLoopConfig,
signal::Union{Nothing, AbortSignal},
emit::AgentEventSink,
)::ExecutedToolCallBatch
```
**Flow**:
1. For each tool call:
- If immediate: execute and add to finalized_calls
- If prepared: create closure, add to finalized_calls
2. For each entry in finalized_calls:
- If closure: execute closure
- If finalized: use as-is
3. Collect all tool results
4. Return batch
### prepareToolCall()
```julia
function prepareToolCall(
current_context::AgentContext,
assistant_message::AssistantMessage,
tool_call::ToolCall,
config::AgentLoopConfig,
signal::Union{Nothing, AbortSignal},
)::Union{PreparedToolCall, ImmediateToolCallOutcome}
```
**Flow**:
1. Find tool by name
2. If not found → ImmediateToolCallOutcome (error)
3. before_tool_call hook (optional)
4. prepareToolCallArguments() (optional)
5. validateToolArguments()
6. Return PreparedToolCall
### executePreparedToolCall()
```julia
function executePreparedToolCall(
prepared::PreparedToolCall,
signal::Union{Nothing, AbortSignal},
emit::AgentEventSink,
)::ExecutedToolCallOutcome
```
**Flow**:
1. Call tool.execute(id, args, signal, on_update)
2. Collect update events (if any)
3. Wait for all update events
4. Return ExecutedToolCallOutcome(result)
### finalizeExecutedToolCall()
```julia
function finalizeExecutedToolCall(
current_context::AgentContext,
assistant_message::AssistantMessage,
prepared::PreparedToolCall,
executed::ExecutedToolCallOutcome,
config::AgentLoopConfig,
signal::Union{Nothing, AbortSignal},
)::FinalizedToolCallOutcome
```
**Flow**:
1. after_tool_call hook (optional)
2. Return FinalizedToolCallOutcome
### createToolResultMessage()
```julia
function createToolResultMessage(
finalized::FinalizedToolCallOutcome,
)::ToolResultMessage
```
**Creates**:
```julia
ToolResultMessage(
"toolResult",
finalized.tool_call.id,
finalized.tool_call.name,
finalized.result.content,
finalized.result.details,
finalized.result.usage,
finalized.result.added_tool_names,
finalized.is_error,
timestamp,
)
```
## Execution Modes
### Sequential Execution
```
┌─────────────────────────────────────────────────────────────────────────┐
│ Sequential Execution Flow │
└─────────────────────────────────────────────────────────────────────────┘
┌──────┐
│ TC1 │ ──► prepareToolCall()
└──────┘ │
┌──────────────┐
│ execute() │ ──► Wait for completion
└──────────────┘ │
│ ▼
├───────────── createToolResultMessage()
│ │
▼ ▼
┌──────────────┐ ┌──────────┐
│ TC2 │ ──► │ │ Result1 │
└──────┘ └──────────┘
┌──────────────┐
│ execute() │
└──────────────┘
┌──────────────┐
│ TC3 │ ──► │
└──────┘ │
│ ▼
├───── createToolResultMessage()
│ │
▼ ▼
┌──────────────┐ ┌──────────┐
│ execute() │ │ │ Result2 │
└──────────────┘ └──────────┘
┌──────────┐
│ Result3 │
└──────────┘
```
### Parallel Execution
```
┌─────────────────────────────────────────────────────────────────────────┐
│ Parallel Execution Flow │
└─────────────────────────────────────────────────────────────────────────┘
┌──────┐
│ TC1 │ ──► prepareToolCall() ──► create closure ──► ┐
└──────┘ │
┌──────┐ │
│ TC2 │ ──► prepareToolCall() ──► create closure ──► ├─► All closures queued
└──────┘ │
┌──────┐ │
│ TC3 │ ──► prepareToolCall() ──► create closure ──► ┘
└──────┘
┌───────────────────────┐
│ for closure in closures│
│ execute_closure() │
└───────────────────────┘
┌───────────────────────┐
│ Collect all results │
└───────────────────────┘
┌───────────────────────┐
│ createToolResult() │
└───────────────────────┘
```
## Helper Types
### ExecutedToolCallBatch
```julia
struct ExecutedToolCallBatch
messages::Vector{ToolResultMessage}
terminate::Bool
end
```
- `messages`: All tool result messages
- `terminate`: If true, stop agent after this batch
### PrepareNextTurnContext
```julia
struct PrepareNextTurnContext
message::AssistantMessage
tool_results::Vector{ToolResultMessage}
context::AgentContext
new_messages::Vector{AgentMessage}
end
```
Used by prepare_next_turn hook to decide next steps.
### Before/After Tool Call Contexts
```julia
struct BeforeToolCallContext
assistant_message::AssistantMessage
tool_call::ToolCall
args::Any
context::AgentContext
end
struct BeforeToolCallResult
block::Union{Bool, Nothing}
reason::Union{String, Nothing}
end
struct AfterToolCallContext
assistant_message::AssistantMessage
tool_call::ToolCall
args::Any
result::AgentToolResult
is_error::Bool
context::AgentContext
end
struct AfterToolCallResult
content::Union{Vector{MessageContent}, Nothing}
details::Union{Any, Nothing}
is_error::Union{Bool, Nothing}
usage::Union{Usage, Nothing}
terminate::Union{Bool, Nothing}
end
```
## Event Emission Timeline
```
AgentStartEvent
├─ TurnStartEvent (turn 1)
│ │
│ ├─ MessageStartEvent (user prompt)
│ ├─ MessageEndEvent (user prompt)
│ │
│ ├─ MessageStartEvent (assistant)
│ ├─ MessageUpdateEvent (text delta)
│ ├─ MessageUpdateEvent (tool call delta)
│ ├─ MessageEndEvent (assistant)
│ │
│ ├─ ToolExecutionStartEvent (tc1)
│ ├─ ToolExecutionEndEvent (tc1)
│ │
│ ├─ ToolExecutionStartEvent (tc2)
│ ├─ ToolExecutionEndEvent (tc2)
│ │
│ └─ TurnEndEvent (assistant, tool_results)
├─ TurnStartEvent (turn 2 - if needed)
│ │
│ ├─ MessageStartEvent (steering/follow-up)
│ ├─ MessageEndEvent (steering/follow-up)
│ │
│ ├─ MessageStartEvent (assistant)
│ ├─ MessageUpdateEvent (text)
│ ├─ MessageEndEvent (assistant)
│ │
│ └─ TurnEndEvent (assistant, [])
└─ AgentEndEvent (final messages)
```
## Key Concepts
### 1. Message Transformation Pipeline
```
AgentMessage[] (internal)
│ transform_context()
AgentMessage[] (transformed)
│ convert_to_llm()
Message[] (LLM API)
```
### 2. Tool Call Lifecycle
```
ToolCall (in assistant message)
├─ before_tool_call (hook)
├─ prepareToolCall()
│ ├─ validate arguments
│ └─ prepare arguments (optional)
├─ execute()
│ ├─ Immediate: return result
│ └─ Prepared: async execution
├─ after_tool_call (hook)
└─ createToolResultMessage()
```
### 3. Turn Termination
```julia
# Turn ends when:
# 1. No more pending messages
# 2. No more tool calls to execute
# 3. should_stop_after_turn() returns true
# Reasons to stop:
# - Max turns reached
# - Tool returned terminate=true
# - Error or abort
# - Steering/follow-up queues empty
```
## Best Practices
1. **Use sequential execution** for tools that modify shared state
2. **Use parallel execution** for independent tool calls (better performance)
3. **Implement prepare_next_turn** for dynamic model/thinking level changes
4. **Use before_tool_call** for logging or blocking sensitive operations
5. **Use after_tool_call** for modifying results or collecting metrics
## Complete Example
```julia
using AgentCore
# Create config
config = AgentLoopConfig(
model = my_model,
reasoning = THINKING_MEDIUM,
tool_execution = EXECUTION_PARALLEL,
before_tool_call = myBeforeToolCallHook,
after_tool_call = myAfterToolCallHook,
prepare_next_turn = myPrepareNextTurnHook,
convert_to_llm = myConvertToLlm,
transform_context = myTransformContext,
get_api_key = myGetApiKey,
get_steering_messages = myGetSteeringMessages,
get_follow_up_messages = myGetFollowUpMessages,
)
# Start agent loop
stream = agentLoop(
[UserMessage("user", [TextContent("Hello")], timestamp)],
AgentContext(system_prompt, messages, tools),
config,
nothing,
stream_fn,
)
# Consume events
final_messages = []
for event in stream
if event isa MessageEndEvent
push!(final_messages, event.message)
end
end
# Or use event sink
messages = []
emit(event) = push!(messages, event)
messages = runAgentLoop(
[UserMessage(...)],
context,
config,
emit,
nothing,
stream_fn,
)
```
This documentation provides a comprehensive understanding of the AgentLoop component, including its architecture, main functions, execution modes, and best practices for building AI agents with AgentCore.jl.