Croway commented on code in PR #24116:
URL: https://github.com/apache/camel/pull/24116#discussion_r3441912539
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components/camel-ai/camel-a2a/src/main/docs/a2a-component.adoc:
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@@ -471,6 +471,69 @@ You can also emit with an explicit state:
NOTE: Use `script` EIP (not `setBody`) for `${a2a:emit()}` calls — `script`
evaluates the expression for its side effect without changing the message body.
Use `setBody` only for the final response.
+=== Scoped progress updates with `a2aSubTask`
+
+Camel routes can group related work with the `a2aSubTask` EIP and emit
progress updates before, after, or when the grouped steps fail.
+This is a regular Camel route step, not a YAML-only extension, and it can be
used from Camel's model-based DSLs when `camel-a2a` is on the classpath.
+The `emitBefore`, `emitAfter`, and `emitOnError` fields are optional and are
evaluated as Simple expressions against the current Exchange.
+The nested `steps` behave like normal Camel route steps: in YAML they are
configured under `steps`, and in Java DSL they are added after `.a2aSubTask()`
until `.end()`.
+If the nested steps fail, `emitOnError` can access the original exception, for
example with `$\{exception.message}`, and the original exception continues to
propagate through the route.
+Failures while evaluating the `emitBefore`, `emitAfter`, or `emitOnError`
Simple expressions are route failures.
+Failures while storing or notifying the resulting A2A progress event are
best-effort: they are logged at debug level and do not stop nested work, fail
an otherwise successful exchange, or replace the original nested-step exception.
+By default, emitting progress outside an active A2A task context is a no-op.
+Set `failIfNoTaskContext=true` when a route should fail instead if the current
Exchange does not carry an active A2A task.
+An active task context is normally created by an A2A consumer while it is
processing a task.
+Use stable `id` values on long-lived sub-tasks so route tracing and
route-structure views keep stable node names.
+
+[source,yaml]
+----
+- route:
+ from:
+ uri: a2a:classpath:agent-card.json
+ parameters:
+ protocolBinding: JSONRPC
+ httpServerComponent: undertow
+ validateAuth: false
+ steps:
+ - a2aSubTask:
+ id: search-docs-progress
+ emitBefore: "Searching docs..."
+ emitAfter: "Docs found: ${body.size()}"
+ emitOnError: "Error searching docs: ${exception.message}"
+ failIfNoTaskContext: true
+ steps:
+ - to:
+ uri: "elasticsearch:docs?operation=Search"
+ - a2aSubTask:
+ id: draft-answer-progress
+ emitBefore: "Drafting answer..."
+ emitAfter: "Answer drafted: ${body}"
+ emitOnError: "Error drafting answer: ${exception.message}"
+ steps:
+ - bean:
+ ref: answerDraftingService
+ method: draft
+ - setBody:
+ simple: "Final answer: ${body}"
+----
+
+The route examples in this section are local-only because they disable
operation auth. Keep `validateAuth=true` and configure a card security scheme
for network-exposed agents.
+
+The same route step is also available from Java DSL:
+
+[source,java]
+----
+from("a2a:classpath:agent-card.json?protocolBinding=JSONRPC&httpServerComponent=undertow&validateAuth=false")
+ .a2aSubTask()
Review Comment:
@davsclaus didn't we discussed that we should not modify the DSL?
I remember having similar discussion for an AI/Agent DSL, and we decided
that we shouldn't introduce new DSL for agentic stuff
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