fix(assistant): improve middleware dispatch and inject kwargs in middleware by WilliamBergamin · Pull Request #1456 · slackapi/bolt-python

WilliamBergamin · 2026-03-11T21:47:54Z

Summary

Extracts assistant kwargs injection (say, set_status, set_title, set_suggested_prompts, get_thread_context, save_thread_context) from App._init_context / AsyncApp._init_context into
dedicated listener middleware (AttachingAssistantKwargs / AsyncAttachingAssistantKwargs)
Generalizes extract_thread_ts to work for all event types (not just assistant events), populating context.thread_ts for any threaded event
Removes thread_ts from the default Say constructor in BoltContext.say — assistant threading is now handled entirely by the Assistant middleware

Testing

Pull this branch and build the project
Create a new app with bolt-python-assistant-template
Use the new Bolt version in the app
There should be no behavior changes 🟢

Requirements

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

I've read and understood the Contributing Guidelines and have done my best effort to follow them.
I've read and agree to the Code of Conduct.
I've run ./scripts/install_all_and_run_tests.sh after making the changes.

…stantKwargs

codecov · 2026-03-11T21:51:06Z

Codecov Report

❌ Patch coverage is 95.60440% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.15%. Comparing base (4d15431) to head (ebc67bb).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
slack_bolt/middleware/assistant/assistant.py	77.77%	2 Missing ⚠️
slack_bolt/middleware/assistant/async_assistant.py	77.77%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1456      +/-   ##
==========================================
+ Coverage   90.67%   91.15%   +0.48%     
==========================================
  Files         226      229       +3     
  Lines        7205     7262      +57     
==========================================
+ Hits         6533     6620      +87     
+ Misses        672      642      -30

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

srtaalej

good catch on process() skipping listener-level middleware! keeping the AttachingAssistantKwargs seperate from generic context makes the assistant code much cleaner 🫧 .
my only recommendation would be to add a changelog 🦋 for users who rely on getting thread_ts in non assistant listeners 🤔
for example - @mention -ing the app in a channel thread. if you start a thread on a regular message, then @mention the bot in that thread the handle_mention listener's say() posts to the channel (not the thread), because thread_ts is no longer injected into say for non-assistant listeners

srtaalej · 2026-03-12T19:47:34Z

slack_bolt/context/context.py

        """
        if "say" not in self:
-            self["say"] = Say(client=self.client, channel=self.channel_id, thread_ts=self.thread_ts)
+            self["say"] = Say(client=self.client, channel=self.channel_id)


🌟 praise: In agreement with @srtaalej this is a good change - the thread_ts attempted before was not set at this point in execution. Now we want to avoid changing this behavior while still improving the available context values. Solid!

srtaalej · 2026-03-12T20:34:29Z

slack_bolt/middleware/assistant/attaching_assistant_kwargs.py

+from slack_bolt.response.response import BoltResponse
+
+
+class AttachingAssistantKwargs(Middleware):


great to see this consolidated into one file ⭐

WilliamBergamin · 2026-03-12T21:30:55Z

my only recommendation would be to add a changelog 🦋 for users who rely on getting thread_ts in non assistant listeners 🤔
for example - @mention -ing the app in a channel thread. if you start a thread on a regular message, then @mention the bot in that thread the handle_mention listener's say() posts to the channel (not the thread), because thread_ts is no longer injected into say for non-assistant listeners

I understand your concern around the @mention -ing the app in a channel thread, but from my testing this behavior was not present, looking at the implementation of extract_thread_ts, thread_ts would be None if the payload was not a is_assistant_event, thus for @mention events thread_ts would be None and say() would posts to the channel

But I agree its worth calling out in the changelog that some undocumented behaviors around assistant events may change slightly

WilliamBergamin · 2026-03-12T22:49:15Z

@srtaalej these are good concerns 💯 in a follow up PR I will address these concerns

zimeg

@WilliamBergamin Awesome separation of middleware! Testing went well for me and these patterns are looking good to me 🚢

I left a question about the scope of middleware but this might be a misunderstanding I have in how events are processed.

📣 We might want to callout that context.thread_ts is available more often now in CHANGELOG entries too but I don't know if this is documented elsewhere so no blocker!

zimeg · 2026-03-16T22:19:12Z

slack_bolt/context/context.py

        """
        if "say" not in self:
-            self["say"] = Say(client=self.client, channel=self.channel_id, thread_ts=self.thread_ts)
+            self["say"] = Say(client=self.client, channel=self.channel_id)


🌟 praise: In agreement with @srtaalej this is a good change - the thread_ts attempted before was not set at this point in execution. Now we want to avoid changing this behavior while still improving the available context values. Solid!

zimeg · 2026-03-16T22:45:26Z

slack_bolt/middleware/assistant/assistant.py

+                            # This means the listener is not for this incoming request.
+                            continue
+                        if middleware_resp is not None:
+                            resp = middleware_resp


👁️‍🗨️ question: Was middleware not handled for the assistant listener? I'm curious if app.py#L907 is a sufficient addition or if this is also needed? I haven't given detailed look to this, but I understood the order:

Global middleware

Listener middleware

And it's not clear to me if the global middleware is sufficient or if this is gives us confidence that listeners for the assistant class has these arguments in all cases?

zimeg · 2026-03-16T22:46:45Z

slack_bolt/request/internals.py

+    if payload.get("event") is not None:
+        return extract_thread_ts(payload["event"])


🪐 praise: Nice extractions!

zimeg · 2026-03-16T22:52:51Z

tests/scenario_tests/test_events_assistant.py

        def start_thread(say: Say, set_suggested_prompts: SetSuggestedPrompts, context: BoltContext):
            assert context.channel_id == "D111"
            assert context.thread_ts == "1726133698.626339"
+            assert say.thread_ts == context.thread_ts


🧪 praise: Thanks for adding asserts!

fix(assistant): improve middleware dispatch and extract AttachingAssi…

69f8f93

…stantKwargs

WilliamBergamin added this to the 1.27.1 milestone Mar 11, 2026

WilliamBergamin requested review from mwbrooks, srtaalej and zimeg March 11, 2026 21:47

WilliamBergamin self-assigned this Mar 11, 2026

WilliamBergamin requested a review from a team as a code owner March 11, 2026 21:47

WilliamBergamin added area:async improvement area:sync python Pull requests that update Python code semver:patch labels Mar 11, 2026

srtaalej approved these changes Mar 12, 2026

View reviewed changes

Merge branch 'main' into set-assistant-say-in-middleware

5a9f0f1

Merge branch 'main' into set-assistant-say-in-middleware

38c40a1

WilliamBergamin added 2 commits March 13, 2026 10:19

prevent any possible breaking changes

807e53b

Add unit tests

ebc67bb

zimeg mentioned this pull request Mar 16, 2026

ci: attempt updates to python dependencies daily slack-samples/bolt-python-assistant-template#58

Open

3 tasks

zimeg approved these changes Mar 16, 2026

View reviewed changes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

fix(assistant): improve middleware dispatch and inject kwargs in middleware#1456

fix(assistant): improve middleware dispatch and inject kwargs in middleware#1456
WilliamBergamin wants to merge 5 commits intomainfrom
set-assistant-say-in-middleware

WilliamBergamin commented Mar 11, 2026

Uh oh!

codecov bot commented Mar 11, 2026 •

edited

Loading

Uh oh!

srtaalej left a comment •

edited

Loading

Uh oh!

srtaalej Mar 12, 2026

Uh oh!

zimeg Mar 16, 2026

Uh oh!

srtaalej Mar 12, 2026

Uh oh!

WilliamBergamin commented Mar 12, 2026 •

edited

Loading

Uh oh!

WilliamBergamin commented Mar 12, 2026

Uh oh!

zimeg left a comment

Uh oh!

zimeg Mar 16, 2026

Uh oh!

zimeg Mar 16, 2026

Uh oh!

zimeg Mar 16, 2026

Uh oh!

zimeg Mar 16, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

		from slack_bolt.response.response import BoltResponse


		class AttachingAssistantKwargs(Middleware):

		if payload.get("event") is not None:
		return extract_thread_ts(payload["event"])

Conversation

WilliamBergamin commented Mar 11, 2026

Summary

Testing

Category

Requirements

Uh oh!

codecov bot commented Mar 11, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Codecov Report

Uh oh!

srtaalej left a comment • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

srtaalej Mar 12, 2026

Choose a reason for hiding this comment

Uh oh!

zimeg Mar 16, 2026

Choose a reason for hiding this comment

Uh oh!

srtaalej Mar 12, 2026

Choose a reason for hiding this comment

Uh oh!

WilliamBergamin commented Mar 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

WilliamBergamin commented Mar 12, 2026

Uh oh!

zimeg left a comment

Choose a reason for hiding this comment

Uh oh!

zimeg Mar 16, 2026

Choose a reason for hiding this comment

Uh oh!

zimeg Mar 16, 2026

Choose a reason for hiding this comment

Uh oh!

zimeg Mar 16, 2026

Choose a reason for hiding this comment

Uh oh!

zimeg Mar 16, 2026

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

codecov bot commented Mar 11, 2026 •

edited

Loading

srtaalej left a comment •

edited

Loading

WilliamBergamin commented Mar 12, 2026 •

edited

Loading