[AGE-4027] fix(api): Stop session rename from bumping the activity timestamp

[bekossy]

Summary

Fixes #5579. In the playground's Session history list, sending a message in session A then session B correctly shows B on top (most recent first) — but reloading the page can flip the order back, even though B still has the more recent message.

Root cause: the session list has one sort function on both the live and reload paths, keyed on lastMessageAt. Live updates stamp it precisely client-side when a turn settles. On reload, the value is folded in from the server's SessionStream.updated_at column — documented as "the heartbeat timestamp." But update_header() in the API also bumped that same column on every rename, including the frontend's fire-and-forget auto-title call that fires on every session's first message. That call is unawaited, so its write can land arbitrarily late — including after a different session's entire exchange has finished — silently reordering the list on the next reconcile (mount/reload/focus/60s poll).

Changes

update_header() (api/oss/src/dbs/postgres/sessions/streams/dao.py) no longer touches updated_at. That's the real heartbeat path's job (update(), a separate method) — a rename/auto-title is not activity. Checked: on the frontend, updated_at has exactly one consumer (the session-list sort), and nothing else on the backend depends on rename bumping it.

Testing

Verified locally

• ruff format / ruff check clean.
• Reproduced the underlying issue manually (create two sessions, message both, rename the older one, reload — order flips) to confirm the diagnosis before writing the fix.

Added or updated tests

• api/oss/tests/pytest/unit/sessions/test_stream_header_no_activity_bump.py: a fake-engine unit test (no live DB) asserting a rename leaves updated_at untouched. Verified it fails against the pre-fix code and passes against the fix.
• Full api/oss/tests/pytest/unit/sessions/ suite (142 tests) passes.

QA follow-up

• Create two chat sessions on the same agent, message the older one, message the newer one — history list shows newest on top. Rename the older session, reload — order should stay the same (newest still on top).
• Regression: the live/in-tab ordering (already correct before this fix) should be unaffected.

Demo

Checklist

• I have included a video or screen recording for UI changes, or marked Demo as N/A
• Relevant tests pass locally
• Relevant linting and formatting pass locally
• I have signed the CLA, or I will sign it when the bot prompts me

Contributor Resources

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[linear-code]

AGE-4027

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Project	Deployment	Actions	Updated (UTC)
agenta-documentation	Ready	Preview	Aug 1, 2026 4:37pm

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 3ab54160-2368-42cb-acea-5eb7b3233654

📥 Commits

Reviewing files that changed from the base of the PR and between 7c395db and 5bd23d8.

📒 Files selected for processing (2)

• api/oss/src/dbs/postgres/sessions/streams/dao.py
• api/oss/tests/pytest/unit/sessions/test_stream_header_no_activity_bump.py

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes

  • Updating a session stream’s name no longer changes its activity timestamp.
  • Heartbeat timing now remains accurate when stream header details are edited.

• Tests

  • Added coverage to verify session name updates preserve the existing activity timestamp.

Walkthrough

SessionStreamsDAO.update_header now preserves the existing heartbeat timestamp when changing stream header data. A database-free asynchronous unit test verifies that the session name changes without modifying updated_at.

Changes

Stream header timestamp behavior

Layer / File(s)	Summary
Preserve heartbeat timestamp api/oss/src/dbs/postgres/sessions/streams/dao.py	update_header no longer assigns the current time to updated_at when updating header data.
Validate header updates api/oss/tests/pytest/unit/sessions/test_stream_header_no_activity_bump.py	Adds fake asynchronous transaction components and a test that verifies the session name changes while the existing heartbeat timestamp remains unchanged.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the fix: session renames no longer update the activity timestamp.
Description check	✅ Passed	The description explains the reload sorting bug, root cause, code change, tests, and validation steps.
Linked Issues check	✅ Passed	The change addresses issue #5579 by preserving updated_at during renames and keeping session ordering stable after reloads.
Out of Scope Changes check	✅ Passed	The changes are limited to the DAO behavior and a focused regression test for the linked issue.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch AGE-4027-/-playground-session-list-sort-order-flips-after-reload

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[chatgpt-codex-connector]

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Reviewed commit: 5bd23d85f8

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[chatgpt-codex-connector]

Condense the explanatory comment

This four-line block duplicates details already documented by SessionStreamDBE and the frontend, making the DAO harder to scan and creating another explanation that can become stale. Condense it to a terse invariant about preserving the heartbeat timestamp; api/AGENTS.md explicitly requires minimal comments and prohibits multi-line narration of what the code does.

AGENTS.md reference: api/AGENTS.md:L20-L22

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