diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 3f4a65296..99d7bd1cd 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -61,3 +61,6 @@ Full layer validation (the `common` behave suite from
 - [`docs/contributing/reviewer-ladder.md`](docs/contributing/reviewer-ladder.md) —
   draft proposal for a four-rung contributor ladder (Triager, Domain
   Reviewer); unadopted until a maintainer decision.
+- [`docs/contributing/agent-lane-throttle.md`](docs/contributing/agent-lane-throttle.md) —
+  draft proposal for demand-side throttling of agent-filed PRs under review
+  backlog; unadopted until a maintainer decision.
diff --git a/docs/contributing/agent-lane-throttle.md b/docs/contributing/agent-lane-throttle.md
new file mode 100644
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@@ -0,0 +1,221 @@
+# Agent-Lane Output Throttle — Contribution Strategy (Planning Draft)
+
+> **Status**: hold-gated planning artifact. Human review required before adoption.
+> Filed by the strategist agent. Tracks [common#1052](https://github.com/projectbluefin/common/issues/1052);
+> pairs with the prioritization rubric in [common#1043](https://github.com/projectbluefin/common/issues/1043).
+>
+> Nothing below changes GitHub roles, branch protection, CODEOWNERS, workflow behavior,
+> label semantics, or hold-gate enforcement until a maintainer adopts it. It is written
+> down for maintainer review rather than applied autonomously.
+
+## Vocabulary
+
+Two terms are used below and are defined here because neither appears in the
+existing factory docs on their own:
+
+- **Agent lane** — a class of agent work defined by who files it and what it
+  produces, not by a workflow label. The lanes observed in the hold-gated queue
+  are **sec-check** (security and supply-chain fixes), **ci-maintainer**
+  (workflow and release-gate repairs), **quality** (test coverage), **scanner**
+  (dependency and drift updates), and **strategist** (planning artifacts such as
+  this file).
+- **Demand-side throttle** — a rule that limits how much *new* work a lane may
+  file while a review queue is above a threshold. It constrains filings, not
+  merges. Nothing already open is closed, relabelled, or reverted.
+
+## Problem
+
+The review bottleneck has three levers. Supply is reviewer coverage
+([common#1029](https://github.com/projectbluefin/common/issues/1029), drafted in
+[`reviewer-ladder.md`](reviewer-ladder.md)). Ordering is which PR a reviewer
+picks up first ([common#1043](https://github.com/projectbluefin/common/issues/1043),
+drafted in [common#1188](https://github.com/projectbluefin/common/pull/1188)).
+Neither addresses **demand**: how much unreviewed work the factory is allowed to
+add to the queue in the first place.
+
+Every open hold-gated PR is a standing cost against a fixed reviewer budget.
+When the filing rate exceeds the review rate, the queue grows monotonically no
+matter how the existing items are ordered. Queue depth is therefore not only a
+symptom of the bottleneck — it is the mechanism.
+
+Reported state, using the snapshots on
+[common#1052](https://github.com/projectbluefin/common/issues/1052) and
+[common#1058](https://github.com/projectbluefin/common/issues/1058):
+
+- **85 open hold-gated PRs**, up from 33 in the preceding 48 hours and 74 less
+  than 24 hours later — a filing rate with no matching review rate.
+  ([common#1052](https://github.com/projectbluefin/common/issues/1052),
+  2026-08-30 snapshot.)
+- Concentration per repo at that snapshot: common 18, server 12, finpilot 9,
+  dakota-iso 9, bluefin-lts 8, bluefin 7, testsuite 7, actions 6, dakota 5,
+  fsdk-containers 4.
+- **Redundant filings inside one repo.** server held four overlapping PXE
+  installer PRs (#22, #25, #26, #27) at that snapshot, all filed 2026-08-21
+  through 2026-08-27 and all competing for the same single reviewer. All four
+  have since been closed without a fix landing. This is the demand-side failure
+  in miniature: the queue is deep because multiple lanes filed against a repo
+  whose review capacity had already been consumed.
+- The downstream consequence is measured elsewhere: bluefin stable frozen 46
+  days as of 2026-09-04, bluefin-lts 28 days stale, common missing its
+  v2026.09 monthly tag ([common#1078](https://github.com/projectbluefin/common/issues/1078)).
+
+A throttle does not clear the backlog. It stops the backlog from growing while
+the supply and ordering fixes land, which is what makes those fixes measurable.
+
+### The burst is the failure mode, not the steady state
+
+The 2026-08-30 snapshot is a spike, and it is worth being precise about that,
+because it changes what this proposal is for. Measured on 2026-09-23 the same
+queue holds **32 open agent-filed PRs across 14 repos, with no repo above 6** —
+below both proposed thresholds. The trajectory is:
+
+| Date | Org-wide open agent PRs | Note |
+|---|---|---|
+| 2026-08-28 (approx.) | 33 | before the burst |
+| 2026-08-29, +48h | 61 | +52 net in 48 hours |
+| 2026-08-30 | 74 → 85 | +13 in under 24 hours |
+| 2026-09-23 | 32 | drained; max 6 in any one repo |
+
+The drain was not a throttle — none exists — it was review and merge. **121
+hive-authored PRs were merged across the org in the week from 2026-09-16**, so
+the merge side does clear a queue once reviewers have the capacity to work it.
+What it did not do is prevent the queue from tripling in 48 hours in the first
+place.
+
+That is the argument for this proposal, stated narrowly: the review bottleneck
+is not a constant backlog that a filing gate would slowly starve, it is an
+intermittent burst that a filing gate can cap at the moment it starts. A
+threshold-triggered, self-lifting throttle is dormant through the 2026-09-23
+state and only binds during a repeat of the 2026-08-28 episode. It is burst
+control, not a permanent ration.
+
+## Proposal: a per-repo filing gate
+
+When a repository's open hold-gated PR count is at or above a threshold, that
+repository stops accepting **new filings from non-P0 lanes** until the queue
+drains below it.
+
+### Thresholds (proposed, not current policy)
+
+| Scope | Threshold | Effect when met |
+|---|---|---|
+| Per repo | 8 open hold-gated PRs | Non-P0 lanes stand down for that repo |
+| Org-wide | 60 open hold-gated PRs | Non-P0 lanes stand down everywhere |
+
+Both numbers are proposals, not current policy, and both are deliberately
+conservative: they sit well below the 2026-08-30 peak (85 org-wide, 9 repos at
+or above 8) and below the ROADMAP target of <40, so the gate releases before the
+target is reached rather than becoming a permanent ration. A maintainer tuning
+these numbers changes one table.
+
+At the 2026-09-23 snapshot the gate would be **dormant**: 32 open agent-filed
+PRs across 14 repos, none above 6. That is the intended resting state — the
+throttle exists for the burst, not for the baseline.
+
+### Which lanes stand down
+
+- **Non-P0 lanes that stand down:** quality (coverage), scanner (dependency and
+  drift updates that are not security-relevant), and any refactor or
+  documentation lane — including this strategist lane.
+- **Lanes that may still file:** sec-check, and ci-maintainer work that repairs
+  a release gate. A broken release gate is not competing with review capacity;
+  it is the thing consuming it.
+- **Exempt entirely:** human-filed PRs. This throttle governs agent filing only.
+  The factory's stated problem is agent output crowding out human review, so
+  constraining humans would invert the intent.
+
+### Optional per-lane WIP caps (stricter, additive)
+
+The 2026-08-30 comment on
+[common#1052](https://github.com/projectbluefin/common/issues/1052) recommended
+per-lane caps as a stricter alternative to a repo-wide gate: **scanner ≤5** and
+**quality ≤8** open PRs per repo, in force until the org-wide queue drains below
+40. These are compatible with the gate above — a lane cap binds even when the
+repo is under threshold, and the repo gate binds even when a lane is under its
+cap. A maintainer may adopt either, both, or neither.
+
+### Reversibility
+
+The throttle is self-clearing by construction:
+
+- It is a function of queue depth, not a schedule. There is nothing to turn off
+  manually and no expiry date to forget.
+- It never closes, relabels, reverts, or deprioritizes an open PR. Queue depth
+  falls only through review, merge, or human close — the actions the bottleneck
+  is actually about.
+- Standing down delays a filing; it does not cancel the work. A lane that stands
+  down re-files once the repo drops below threshold, and the issue it would have
+  filed is unchanged in the meantime.
+
+## Pairing with the P0/P1/P2 rubric
+
+The gate is only mechanical if "P0" is mechanical. The rubric proposed in
+[common#1043](https://github.com/projectbluefin/common/issues/1043) supplies
+exactly that vocabulary, and this document does not redefine it:
+
+- A filing is **P0** — and therefore permitted while the throttle is active —
+  when it is a security, supply-chain, or core-integrity fix. That is the
+  rubric's own P0 tier.
+- Everything the rubric places in **P1** and **P2** stands down while the
+  throttle is active. P1 defects are delayed by this proposal, which is a real
+  cost and the reason the thresholds are set to release early.
+
+The two drafts are independent: either can be adopted without the other.
+Adopting the rubric alone orders the queue but does not bound its growth;
+adopting the throttle alone gates filings on a P0 definition that lives in the
+rubric. Together they are the demand-side half of the review-bottleneck
+response.
+
+### Compliance with the seven-label contract
+
+The throttle is a **filing gate, not a workflow state**. It adds no label,
+removes no label, and changes no transition:
+
+- It does not alter `1-triage`, `2-discussing`, `3-human-queue`,
+  `3-clanker-queue`, `4-review`, `blocked`, or `hold`.
+- It does not create a new overlay. The rubric's proposed `hold-p0` / `hold-p1`
+  / `hold-p2` labels are reviewer filters there; this document does not propose
+  labels of its own and does not depend on those existing.
+- It is enforced at the moment an agent decides whether to open a PR — a
+  developer-time convention evaluated by the agent, in the same class as the
+  attribution trailers in
+  [`agentic-model.md`](../factory/agentic-model.md), not a CI check. Per the
+  same contract, a process convention must not become a bespoke blocking CI job.
+
+## Operating metrics
+
+Draft measures, to be baselined at adoption:
+
+- **Open hold-gated PR count, org-wide** — baseline 85 on 2026-08-30; gate
+  releases below 60; ROADMAP target <40 and shrinking.
+- **Repos at or above threshold** — baseline 9 of 10 on 2026-08-30; target 0.
+- **Filing rate vs. review rate** — the ratio this proposal exists to invert.
+  Baseline: +52 net in 48 hours, then +13 in under 24 hours.
+- **Stand-down events and their duration** — how often the throttle binds and
+  how long each episode lasts. A throttle that is never active is either
+  mistuned or unnecessary; one that never releases means the thresholds are
+  wrong, not that the lanes should be silenced.
+- **P1 delay** — median age at merge for P1 filings, before and after. This is
+  the proposal's principal cost and should be tracked as one.
+
+## What this document deliberately does not do
+
+- No workflow, CI, or label changes — it proposes no new check, no new label,
+  and no automation.
+- No changes to merge protection, branch protection, or CODEOWNERS.
+- No threshold enforcement mechanism. This draft states the rule; wiring it into
+  any agent runtime or queue tool is a separate, maintainer-owned decision.
+- No closure, relabelling, or reverting of any currently open PR.
+- No reviewer-ladder or prioritization-rubric content — those are
+  [`reviewer-ladder.md`](reviewer-ladder.md) and
+  [common#1043](https://github.com/projectbluefin/common/issues/1043)
+  ([draft PR](https://github.com/projectbluefin/common/pull/1188)).
+
+## Related
+
+- [common#1052](https://github.com/projectbluefin/common/issues/1052) — agent-lane output throttle finding (this doc's tracker)
+- [common#1043](https://github.com/projectbluefin/common/issues/1043) — hold-gate prioritization rubric (supplies the P0/P1/P2 tiers)
+- [common#1029](https://github.com/projectbluefin/common/issues/1029) — reviewer-scaling rung (supply-side counterpart)
+- [common#1058](https://github.com/projectbluefin/common/issues/1058) — reviewer coverage map / repo-concentration data
+- [`reviewer-ladder.md`](reviewer-ladder.md) — draft four-rung contributor ladder proposal
+- [common#1078](https://github.com/projectbluefin/common/issues/1078) — release cadence breakdown (downstream symptom)
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