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The new edge-only hooks pages linked each other with versionless paths like `/learn/step-hooks`, which mintlify resolves against the frozen default version where those pages do not exist, breaking the CI link check. Uses the `/en/learn/...` form the other edge pages already use.
143 lines
4.4 KiB
Plaintext
143 lines
4.4 KiB
Plaintext
---
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title: Step Hooks
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description: Intercept task and flow-method steps with PRE_STEP and POST_STEP hooks in CrewAI
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mode: "wide"
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---
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Step hooks intercept each unit of work inside an execution: every crew **task**
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and every **flow method**. Use them to inspect or rewrite what goes into a
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step, transform what comes out, or trace step-by-step progress — without
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touching the level of individual LLM or tool calls.
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## Overview
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Two interception points cover steps:
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| Point | When | `ctx.payload` |
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|-------|------|---------------|
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| `PRE_STEP` | Before a task or flow method runs | step input (see below) |
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| `POST_STEP` | After a task or flow method runs | step output (see below) |
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What the payload holds depends on `ctx.kind`:
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| `ctx.kind` | `PRE_STEP` payload | `POST_STEP` payload |
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|------------|--------------------|---------------------|
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| `"task"` | The context string passed to the agent | The `TaskOutput` object |
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| `"flow_method"` | The method's parameters as a `dict` | The method's return value |
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For flow methods, positional arguments appear in the params dict under `_0`,
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`_1`, ... keys and keyword arguments under their own names; edits and
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replacements are mapped back onto the actual call.
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## Hook Signature
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```python
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from crewai.hooks import on, HookAborted, InterceptionPoint
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@on(InterceptionPoint.PRE_STEP)
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def step_hook(ctx) -> Any | None:
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# Mutate ctx.payload in place, or
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# return a non-None value to replace it, or
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# raise HookAborted(reason, source) to stop the step
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return None
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```
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## Context Schema
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Both points receive a `StepContext`:
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```python
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class StepContext(InterceptionContext):
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payload: Any # Step input (pre) or step output (post)
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kind: str | None # "task" or "flow_method"
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step_name: str | None # Task name/description, or flow method name
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output: Any # POST_STEP only: same object as payload
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agent: Any # Task steps: the executing agent (else None)
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agent_role: str | None # Task steps: the agent's role (else None)
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task: Any # Task steps: the Task instance (else None)
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crew: Any # None for step points
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flow: Any # Flow-method steps: the Flow instance (else None)
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```
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For task steps, `step_name` is the task's `name` (falling back to its
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description). For flow-method steps, it is the method name.
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## Common Use Cases
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### Step Tracing
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```python
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@on(InterceptionPoint.POST_STEP)
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def trace_steps(ctx):
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print(f"{ctx.kind} '{ctx.step_name}' finished")
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```
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### Rewriting Task Context
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```python
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@on(InterceptionPoint.PRE_STEP)
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def inject_disclaimer(ctx):
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if ctx.kind != "task":
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return None
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return f"{ctx.payload}\n\nNote: treat all figures as estimates."
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```
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### Transforming Task Output
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```python
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@on(InterceptionPoint.POST_STEP)
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def normalize_output(ctx):
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if ctx.kind != "task":
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return None
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ctx.payload.raw = ctx.payload.raw.strip()
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```
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<Note>
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`POST_STEP` runs before the task's output is stored, so rewrites propagate
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everywhere the output is used: downstream task context, callbacks, the final
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crew output, and the task's `output_file` on disk.
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</Note>
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### Guarding Flow Methods
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```python
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@on(InterceptionPoint.PRE_STEP)
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def guard_publish(ctx):
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if ctx.kind == "flow_method" and ctx.step_name == "publish":
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if not ctx.flow.state.get("reviewed"):
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raise HookAborted(reason="publish requires review", source="review-gate")
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```
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### Filtering by Agent
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Step hooks support the same `agents=` filter as the other points (matched
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against the executing agent's role on task steps):
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```python
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@on(InterceptionPoint.POST_STEP, agents=["Researcher"])
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def log_research_steps(ctx):
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print(f"research step done: {ctx.step_name}")
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```
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## Aborting a Step
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Raising `HookAborted` in `PRE_STEP` stops the step before any agent or method
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work happens, and the abort propagates out of the execution with its reason —
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it is not swallowed. Any other exception raised by a step hook is swallowed
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(fail-open), like at every other point.
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## Managing Hooks in Tests
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```python
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from crewai.hooks import clear_all_hooks
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clear_all_hooks() # Clears every point, including steps
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```
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## Related Documentation
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- [Execution Hooks Overview →](/en/learn/execution-hooks)
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- [Execution Boundary Hooks →](/en/learn/execution-boundary-hooks)
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- [LLM Call Hooks →](/en/learn/llm-hooks)
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- [Tool Call Hooks →](/en/learn/tool-hooks)
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