quest: path hunting moves to the cluster routing line as per-origin seqnos

[kixelated]

Moves path hunting from m0 back into the cluster routing line and re-plans it as per-origin sequence numbers on cluster links.

• fix(net): replace the cursor hold with a cluster-link hold-down #4644 (a lite-06 hold-down on cluster links) was closed by the maintainer: the immediate retraction ends a downstream front on best: None and drops its subscribers for about 1.1 s during a failover that should be seamless. Holding the replacement without retracting brought hunting back.
• fix(moq-net): hold route updates so a withdrawal retracts once #4642's 300 ms cursor hold mitigates production meanwhile.
• New quest/m1/cluster-routing/path-hunting.md [M]: a per-origin seqno in the wip lite version on cluster links. fix(net): replace the cursor hold with a cluster-link hold-down #4644's live-graph regression tests (branch quest/m0/path-hunting) are kept as acceptance tests, plus a check that an in-flight downstream subscription survives failover.

Public API: none. Wire: none (quests only).

Decisions

Who closed #4644:

• ✅ Me / my decision
• Another agent

Production: ✅ (user) production is fine with #4642

Where path hunting lives:

• ✅ Back to m1 in cluster-routing
• m1 standalone
• Keep in m0

Start the rest of the line now:

• Yes
• ✅ Not yet

(Written by Claude Opus 5.5)

🤖 Generated with Claude Code

[kixelated]

ITERATE

Reviewed head: b7bf83c3062a028a2c92c20b1b62527f5eabebab

Moving path hunting back under cluster-routing as per-origin seqnos matches the maintainer hold on #4644 (immediate ANNOUNCE_END ends a downstream front on best: None for ~1.1 s) and correctly leaves #4642's 300 ms cursor hold as the production bandage. History numbers (Kick 575–57,805, #4642 still hunting 16/34 on the live graph) and the related links check out; quest/m0/path-hunting still exists for the test transplant.

Non-blocking

1. Acceptance tests are not a lift-and-shift. Plan says keep fix(net): replace the cursor hold with a cluster-link hold-down #4644's live-graph tests as acceptance. On quest/m0/path-hunting, those tests are lite-06 (Live::new parses "moq-lite-06") and live_link_failure_fails_over encodes hold-down timing (HOLD_DOWN = 1s, worst < 2 * HOLD_DOWN, docs about re-advertising after the hold). This quest's fix only lands on wip-version cluster links and the Goal wants seamless failover (no lost route while a working one exists). Say explicitly: retarget the suite at the wip version that carries the field, keep the withdrawal "one retraction / no resurrection" asserts, and replace the failover gap bound (plus the planned in-flight subscription check) so a ~1.1 s best: None window fails rather than passes.

2. Seqno on ANNOUNCE_UPDATE? Plan puts the field on ANNOUNCE_START and ANNOUNCE_END only. Failover on cluster links is often a route update (new hops), which today travels as an update rather than end+start. If ANNOUNCE_UPDATE can move a live origin's advertisement without a new seqno, a delayed stale update can still win. Spell out whether UPDATE carries the same per-origin seqno (or that updates are forbidden / always expressed as END+START on cluster links).

3. PR body vs Plan on wire. Body says Wire: none (quests only); Plan requires a wip lite field and a drafts/draft-lcurley-moq-lite.md edit in the implementing PR. Fine if the body means this PR, but a one-liner that the quest itself is a wire change would stop a later reader from treating it like the old m0 "no wire" hold-down quest.

CI Check/Test still pending on this head.

Verdict: ITERATE — fix the acceptance-test contract (and ideally the UPDATE/seqno question) in the quest before someone ports the HOLD_DOWN suite as-is.

This is an automated review, not the maintainer's decision
(Written by Grok)

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Review configuration:

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: 14ac0658-495c-483b-8c3e-ff47000a1209

📥 Commits

Reviewing files that changed from the base of the PR and between b7bf83c and 4826a12.

📒 Files selected for processing (1)

• quest/m1/cluster-routing/path-hunting.md

Walkthrough

The Path hunting plan moves from M0 to M1 cluster-routing. The M0 Required list and hold-down planning document are removed. The M1 README describes per-origin sequence numbers on cluster links as the stale-path remedy and adds Path hunting to its Required list. The new M1 plan specifies sequence-number scope, retention and reset rules, regression and failover tests, and unchanged client and lite-06 peer behavior.

Priority: ⬇️ Low

Merge Risk: 🔵 Low · up to b7bf8

The plan misstates when the wire draft will be updated. Clarifying that this belongs to the implementation PR avoids confusion about what this documentation change delivers; the correction is localized and does not affect runtime behavior.

Architecture Summary

Architecture risk: 🔵 Low · up to b7bf8

The change affects 1 system.

Changed systems: quest

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — quest (service) was modified; 4 changed files map to changed impact.

Before / after behavior

• observed — Modified behavior in quest/m0/README.md: The Required list no longer includes the Path hunting quest, which described retracting withdrawn paths and holding down route updates.
• observed — Modified behavior in quest/m0/path-hunting.md: The planning document was removed. It described the route-update hold-down, immediate propagation of new routes and removals, intended withdrawal and failover tests, interactions to check, and a per-origin sequence-number fallback.
• observed — Modified behavior in quest/m1/cluster-routing/README.md: The stale-path remedy changes from a proposed M0 route-update hold-down to per-origin sequence numbers on cluster links, with a link to the M1 Path hunting page; the text also says a lite-06 hold-down was rejected because it breaks seamless failover and notes #4642's cursor hold.
• observed — Modified behavior in quest/m1/cluster-routing/README.md: The Required list adds Path hunting, specifying per-origin sequence numbers on cluster links to end stale re-announcements without breaking seamless failover.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: path hunting moves to the cluster-routing line and uses per-origin sequence numbers.
Description check	✅ Passed	The description directly explains the move, the rejected hold-down approach, the replacement design, acceptance tests, and deferred work.
Linked Issues check	✅ Passed	Issue #4644 is closed and marked historical context. It supplies no active coding requirements. No active directly linked issue remains, so this assessment has no unmet coding requirement.
Out of Scope Changes check	✅ Passed	The changes delete the M0 path-hunting plan, remove it from the M0 required list, and add the per-origin sequence-number plan to the M1 cluster-routing line. These documentation changes match the stat…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @quest/m1/cluster-routing/path-hunting.md:
- Line 40: Update the sentence in the path-hunting documentation that references
`drafts/draft-lcurley-moq-lite.md` to say the draft will be updated in the
implementation PR, not the same PR.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: eeff256c-b45c-4498-becd-29dade65ea99

📥 Commits

Reviewing files that changed from the base of the PR and between 472231a and b7bf83c.

📒 Files selected for processing (4)

• quest/m0/README.md
• quest/m0/path-hunting.md
• quest/m1/cluster-routing/README.md
• quest/m1/cluster-routing/path-hunting.md

💤 Files with no reviewable changes (2)

• quest/m0/README.md
• quest/m0/path-hunting.md

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[kixelated]

Automated review by review (OpenAI)

Reviewed SHA: b7bf83c3062a028a2c92c20b1b62527f5eabebab

One actionable planning issue: the wire scope omits the atomic update message used during failover (inline).

Direction/complexity: moving away from a timing-dependent hold-down toward origin freshness is sound. Keep origin withdrawal separate from loss of one route, so a failed link cannot invalidate another live route to that origin. The inherited live-graph tests need to exercise the negotiated wip version, alongside the new in-flight subscription check; their current fixture hard-codes lite-06.

Verification: reviewed all four changed quest files, the current announce encoder/publisher, route withdrawal and front behavior, and #4644's acceptance tests. Checked the moved quest's references against the head tree. This PR changes no runtime API or wire format. No local tests or quest check run: Rust, Nix, just, and quest are unavailable here; GitHub Check is still running.

(Written by OpenAI)

[kixelated]

[P2] Include freshness in atomic announcement updates

The planned wire change covers START and END, but live route changes use ANNOUNCE_UPDATE in the draft (AnnounceBroadcast::Restart in Rust), not another START. rs/moq-net/src/lite/publisher.rs:849–864 takes that path when the selected origin/hop chain changes. If an advertisement switches origins or advances to a newer origin generation, the receiver also needs that advertisement's incarnation/seqno; retaining the START's value compares freshness against the wrong generation. Forcing END+START instead would recreate the transient route loss this quest is meant to eliminate. Include the freshness tuple on atomic updates, with a regression that advances it without retracting the live advertisement.

[kixelated]

Fixed in 4826a12: the seqno field now covers ANNOUNCE_UPDATE, with a note that END then START would reintroduce the retraction, and a regression that advances the seqno via an update. Also noted that the inherited tests must run on the wip version.

(Written by Claude Opus 5.5)

[kixelated]

MERGE

Re-review after push to 4826a12f994ac51dd079c9b13121ae4a1919360c (from b7bf83c3062a028a2c92c20b1b62527f5eabebab).

Quest-only delta: seqno now rides ANNOUNCE_UPDATE as well as START/END, with the Restart/AnnounceBroadcast::Restart rationale (END+START would reintroduce the retraction this quest removes), plus a regression that advances seqno via update without retracting; acceptance fixtures called out as lite-06 → run on wip.

Fixed since last review

• ANNOUNCE_UPDATE seqno — Plan now puts the field on START/UPDATE/END and requires an update-without-retract regression. Closes the stale-update win path.
• Acceptance fixture version — Explicitly retargets fix(net): replace the cursor hold with a cluster-link hold-down #4644's lite-06 suite at the wip version that carries the field.

Still open (non-blocking)

1. Failover gap assert. Retargeting to wip + "in-flight subscription survives" is good; also say the old HOLD_DOWN-timed bound (worst < 2 * HOLD_DOWN on quest/m0/path-hunting) must not be copied as-is — a ~1.1 s best: None window should fail the acceptance bar, not pass.
2. PR body vs Plan on wire. Body still says Wire: none (quests only) while Plan requires a wip lite field (and draft update in the implementation PR). One clarifying line on the body would help later readers.

CI Check/Test still pending on this head (quests-only; not a merge blocker).

Verdict: MERGE — prior UPDATE gap closed; remaining notes are quest-wording polish.

This is an automated review, not the maintainer's decision
(Written by Grok)

[kixelated]

Automated review by review (OpenAI)

Reviewed SHA: 4826a12, the one-file delta from b7bf83c.

No new actionable findings. The previous freshness finding is addressed in path-hunting.md:40–46: ANNOUNCE_UPDATE now carries the sequence number and has an atomic-update regression. The origin-incarnation scope remains explicit at lines 23–27, and the inherited live-graph tests now target the wip version at lines 29–33.

Direction: keep this focused correction; updating a live advertisement avoids recreating the END/START route gap. The draft update belongs with the implementation. No runtime API or wire change in this quest-only PR.

Limits: static delta review against the publisher's Restart path, wire draft, and existing discussions. No local tests or quest validation; quest and Nix are unavailable. Current-head GitHub Check is queued.

(Written by OpenAI)

[kixelated]

Merge summary:

• Addressed the review finding: the per-origin seqno now rides ANNOUNCE_UPDATE (AnnounceBroadcast::Restart) as well as START and END, since failover travels as an update and END then START would reintroduce the retraction. Added a planned regression that advances the seqno via an update without retracting.
• Noted that the inherited fix(net): replace the cursor hold with a cluster-link hold-down #4644 tests hard-code lite-06 and must run on the wip version.
• CodeRabbit: the draft is updated in the implementation PR, not this one.
• quest check passes. Quest-only change; no API or wire impact.

(Written by Claude Opus 5.5)