feat(subscriptions): add AI-prompt subscription fields + activity logging

[vdekrijger]

Problem

Subscriptions currently only support insights and dashboards as their target resource. To support AI-powered subscription reports (where a user provides a prompt rather than linking to an existing insight or dashboard), the model needs a way to represent and classify this new resource type.

Additionally, subscription saves were not being recorded in the activity log, making it impossible to audit changes to subscription configuration.

Changes

• Adds a prompt field to Subscription for AI-prompt subscriptions
• Classifies a subscription as insight, dashboard, or ai_prompt via a derived resource_type property rather than a stored column. Because it is computed on read from the existing relation/prompt:
  • there is no migration backfill and no column default to keep in sync
  • it can be omitted from activity-log change diffs — it is not a field, so prompt/relation edits are tracked but resource_type never shows up as its own spurious change
  • the ResourceType choices are retained for the resource-type lookups needed by the follow-up PRs
• url and resource_info now dispatch on the derived resource_type
• Adds a display_name property that resolves a human-readable name from the subscription's resource info, falling back gracefully through title → prompt snippet → "AI report"
• Wires Subscription into the activity logging system via ModelActivityMixin and a model_activity_signal receiver, so creates and updates are recorded in the activity log
• Excludes next_delivery_date from both signal emission (via signal_exclusions) and change diffs (via diff_exclusions), so scheduler-only saves never produce spurious activity log entries
• Adds resource_type (derived) and prompt_length to get_analytics_metadata()
• Registers a new feature flag constant SUBSCRIPTION_AI_PROMPT_FEATURE_FLAG_KEY = "ai-subscriptions"

How did you test this code?

New test file test_subscription_activity_log.py covers:

• Activity log entries created on subscription create (parameterized across insight / dashboard / AI) and update
• Correct display_name resolution across all resource types and fallback cases
• Prompt field change recording, including null transitions
• Soft-delete recording
• Exclusion of next_delivery_date from diffs even in mixed saves
• Scheduler-only saves (both with and without update_fields) producing no new log entries

Existing test_subscription_model.py extended with parameterized tests verifying resource_type is correctly derived from the relation.

Publish to changelog?

No

[vdekrijger]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(subscriptions): gate AI subscriptions on AI credit budget #59634
• feat(subscriptions): expose AI subscriptions + ad-hoc reports as MCP tools #59633
• feat(subscriptions): AI subscription API, validation, telemetry, and UI #59632
• feat(subscriptions): scheduled AI delivery via Temporal (email + Slack) #59631
• feat(subscriptions): AI report pipeline primitive (planner, HogQL, synthesis) + sanitization #59630
• feat(subscriptions): add AI-prompt subscription fields + activity logging #59629 👈 (View in Graphite)
• feat(subscriptions): gate AI summaries on AI credit budget #59625
• feat(subscriptions): bring subscriptions to the free tier (freemium, synced to alerts) #59624
• master

This stack of pull requests is managed by Graphite. Learn more about stacking.

[github-actions]

🎭 Playwright didn't run on this PR — your changes touch code that could affect E2E behavior, but Playwright is opt-in via label now to keep CI cost down.

Add the run-playwright label if you want an E2E sweep before merging — CI will pick it up automatically.

Most PRs don't need this. Real regressions still get caught on master and fix-forward.

[github-actions]

Migration SQL Changes

Hey 👋, we've detected some migrations on this PR. Here's the SQL output for each migration, make sure they make sense:

posthog/migrations/1177_subscription_ai_fields.py

BEGIN;
--
-- Add field prompt to subscription
--
ALTER TABLE "posthog_subscription" ADD COLUMN "prompt" text NULL;
COMMIT;

Last updated: 2026-05-27 11:33 UTC (429d4c6)

[github-actions]

🔍 Migration Risk Analysis

We've analyzed your migrations for potential risks.

Summary: 1 Safe | 0 Needs Review | 0 Blocked

✅ Safe

Brief or no lock, backwards compatible

posthog.1177_subscription_ai_fields
  └─ #1 ✅ AddField
     Adding nullable field requires brief lock
     model: subscription, field: prompt

📚 How to Deploy These Changes Safely

AddField:

This operation acquires a brief lock but doesn't rewrite the table.

Deployment uses lock timeouts with automatic retries, so lock contention will cause retries rather than connection pile-up.

Last updated: 2026-05-27 11:34 UTC (429d4c6)

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
posthog/models/test/test_subscription_activity_log.py:37-82
**AI and non-AI creation tests can be unified**

`test_creating_ai_subscription_logs_activity` and `test_non_ai_subscription_logs_activity` test the same assertion pattern (count, activity, item_id, name) for three symmetric cases. The AI case can be added as a third entry in the `@parameterized.expand` list so all three resource-type creation scenarios live in one parameterised test, following the team's preference for parameterised tests over one-off test methods for symmetric cases.

_{Reviews (1): Last reviewed commit: "chore(subscriptions): drop explanatory c..." | Re-trigger Greptile}

[github-actions]

ClickHouse migration SQL per cloud environment

No ClickHouse migrations changed in this PR.

[stamphog]

Gates denied this PR: it touches billing-related code (subscriptions) and is classified as requiring human review. This needs a human reviewer to approve.