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https://issues.apache.org/jira/browse/CAMEL-23776?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Luigi De Masi updated CAMEL-23776:
----------------------------------
    Description: 
CAMEL-23063 introduces A2A progress event emission from Camel routes through 
the Simple language function:

${a2a:emit('Searching docs...')}

This allows route authors to emit progress updates, but common use cases 
require several explicit route steps around the actual work being performed. 
For example, a route may need to
emit a progress event before a search, another event after the search succeeds, 
and another event if the search fails.

This improvement proposes adding an `a2aSubTask` YAML route step in camel-a2a.

The `a2aSubTask` step should group one or more nested Camel route steps and 
emit A2A progress events around that grouped work.

Example:
{code}
  steps:
  - a2aSubTask:
      emitBefore: Searching docs...
      emitAfter: 'Docs found: ${body.size()}'
      emitOnError: 'Error searching docs: ${exception.message}'
      steps:
        - to:
            uri: 'elasticsearch:docs?operation=Search'
  - a2aSubTask:
      emitBefore: Drafting answer...
      emitAfter: 'Answer drafted: ${body}'
      emitOnError: 'Error drafting answer: ${exception.message}'
      steps:
        - bean:
            ref: answerDraftingService
            method: draft
  - setBody:
      simple: 'Final answer: ${body}'
{code}

The emitted messages should support Simple expressions and should be evaluated 
against the current Exchange at the time each event is emitted.

Expected behavior:
 * `emitBefore` is evaluated and emitted before the nested steps are executed.
 * `emitAfter` is evaluated and emitted after the nested steps complete 
successfully.
 * `emitOnError` is evaluated and emitted when the nested steps throw an 
exception.
 * `emitOnError` must not swallow, replace, or hide the original exception.
 * All emit fields are optional.
 * The step should support one or more nested Camel route steps.
 * The nested steps should behave like normal route steps.
 * Existing `${a2a:emit(...)}` support remains available and unchanged.

Implementation notes:
 * This issue should add the A2A-specific route model/reifier/processor support 
needed by `a2aSubTask`.
 * The YAML parser integration should use the generic YAML DSL extension 
mechanism tracked separately.
 * The YAML DSL core should not hard-code the `a2aSubTask` step.

Acceptance criteria:
 * `camel-a2a` provides an `a2aSubTask` YAML route step.
 * `a2aSubTask` supports nested `steps`.
 * `emitBefore`, `emitAfter`, and `emitOnError` are optional.
 * Emit message templates are evaluated as Simple expressions.
 * `emitOnError` can access the exception through `${exception.message}`.
 * Exceptions from nested steps continue to propagate normally.
 * Tests cover successful execution, failure execution, no emit fields, only 
one emit field, and multiple nested steps.
 * Documentation includes the new YAML syntax and at least one full route 
example.

> camel-a2a: Add a2aSubTask YAML route step for scoped progress events
> --------------------------------------------------------------------
>
>                 Key: CAMEL-23776
>                 URL: https://issues.apache.org/jira/browse/CAMEL-23776
>             Project: Camel
>          Issue Type: Improvement
>            Reporter: Luigi De Masi
>            Assignee: Luigi De Masi
>            Priority: Major
>
> CAMEL-23063 introduces A2A progress event emission from Camel routes through 
> the Simple language function:
> ${a2a:emit('Searching docs...')}
> This allows route authors to emit progress updates, but common use cases 
> require several explicit route steps around the actual work being performed. 
> For example, a route may need to
> emit a progress event before a search, another event after the search 
> succeeds, and another event if the search fails.
> This improvement proposes adding an `a2aSubTask` YAML route step in camel-a2a.
> The `a2aSubTask` step should group one or more nested Camel route steps and 
> emit A2A progress events around that grouped work.
> Example:
> {code}
>   steps:
>   - a2aSubTask:
>       emitBefore: Searching docs...
>       emitAfter: 'Docs found: ${body.size()}'
>       emitOnError: 'Error searching docs: ${exception.message}'
>       steps:
>         - to:
>             uri: 'elasticsearch:docs?operation=Search'
>   - a2aSubTask:
>       emitBefore: Drafting answer...
>       emitAfter: 'Answer drafted: ${body}'
>       emitOnError: 'Error drafting answer: ${exception.message}'
>       steps:
>         - bean:
>             ref: answerDraftingService
>             method: draft
>   - setBody:
>       simple: 'Final answer: ${body}'
> {code}
> The emitted messages should support Simple expressions and should be 
> evaluated against the current Exchange at the time each event is emitted.
> Expected behavior:
>  * `emitBefore` is evaluated and emitted before the nested steps are executed.
>  * `emitAfter` is evaluated and emitted after the nested steps complete 
> successfully.
>  * `emitOnError` is evaluated and emitted when the nested steps throw an 
> exception.
>  * `emitOnError` must not swallow, replace, or hide the original exception.
>  * All emit fields are optional.
>  * The step should support one or more nested Camel route steps.
>  * The nested steps should behave like normal route steps.
>  * Existing `${a2a:emit(...)}` support remains available and unchanged.
> Implementation notes:
>  * This issue should add the A2A-specific route model/reifier/processor 
> support needed by `a2aSubTask`.
>  * The YAML parser integration should use the generic YAML DSL extension 
> mechanism tracked separately.
>  * The YAML DSL core should not hard-code the `a2aSubTask` step.
> Acceptance criteria:
>  * `camel-a2a` provides an `a2aSubTask` YAML route step.
>  * `a2aSubTask` supports nested `steps`.
>  * `emitBefore`, `emitAfter`, and `emitOnError` are optional.
>  * Emit message templates are evaluated as Simple expressions.
>  * `emitOnError` can access the exception through `${exception.message}`.
>  * Exceptions from nested steps continue to propagate normally.
>  * Tests cover successful execution, failure execution, no emit fields, only 
> one emit field, and multiple nested steps.
>  * Documentation includes the new YAML syntax and at least one full route 
> example.



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