diff --git a/app/api/graph/coverage/extract/route.ts b/app/api/graph/coverage/extract/route.ts
index 2687f67..1a5ea43 100644
--- a/app/api/graph/coverage/extract/route.ts
+++ b/app/api/graph/coverage/extract/route.ts
@@ -3,7 +3,8 @@
  * (vision-extraction-coverage.md): run the pipeline over ONE session's
  * uncovered content, whatever its size — the user's answer to an aborted
  * run, a pipeline error, or a session that went dormant under the chunk
- * budget. The pipeline itself batches under EXTRACTION.chunkTokens and
+ * budget. The pipeline itself batches under the graph.extractionChunkTokens setting (extraction-UX redesign,
+ * 2026-09-24) and
  * checkpoints coverage per merged batch, so this is the same run the
  * trigger fires, just user-initiated. 409 while a run is already in
  * flight (the dock is the source of truth for that); failures are logged
diff --git a/app/api/graph/import/route.ts b/app/api/graph/import/route.ts
index 0f29d85..03f5bf3 100644
--- a/app/api/graph/import/route.ts
+++ b/app/api/graph/import/route.ts
@@ -14,7 +14,12 @@
  * /api/graph/status, as with session runs.
  */
 import { extraction } from "@/src/server";
-import { ModelsNotConfiguredError, type EmissionStats } from "@/src/core";
+import {
+	ModelsNotConfiguredError,
+	PROVIDER_KEY_MISSING_CODE,
+	ProviderKeyMissingError,
+	type EmissionStats,
+} from "@/src/core";
 
 export const dynamic = "force-dynamic";
 
@@ -23,10 +28,14 @@ interface ImportResult {
 	ok: boolean;
 	stats?: EmissionStats;
 	error?: string;
-	/** The machine discriminator when ok:false is the BYOK refusal (owner,
-	 *  2026-09-22) — the client can open the setup flow off it. */
-	code?: "models_not_configured";
+	/** The machine discriminator when ok:false is a config refusal — the
+	 * BYOK models refusal (owner, 2026-09-22) or the provider-key refusal
+	 * (2026-09-25); the client can open the setup/keys flow off it. */
+	code?: "models_not_configured" | (typeof PROVIDER_KEY_MISSING_CODE);
 	missing?: string[];
+	/** The key-refusal specifics (provider_key_missing only). */
+	provider?: string;
+	slots?: string[];
 }
 
 export async function POST(request: Request) {
@@ -57,6 +66,17 @@ export async function POST(request: Request) {
 					});
 					continue;
 				}
+				if (err instanceof ProviderKeyMissingError) {
+					results.push({
+						filePath: file.name,
+						ok: false,
+						error: err.envelope.error,
+						code: PROVIDER_KEY_MISSING_CODE,
+						provider: err.envelope.provider,
+						slots: err.envelope.slots,
+					});
+					continue;
+				}
 				results.push({ filePath: file.name, ok: false, error: err instanceof Error ? err.message : String(err) });
 			}
 		}
diff --git a/src/agent/subagents/extraction.ts b/src/agent/subagents/extraction.ts
index 19d436d..e65fcb3 100644
--- a/src/agent/subagents/extraction.ts
+++ b/src/agent/subagents/extraction.ts
@@ -4,7 +4,14 @@ import type { Usage } from "@earendil-works/pi-ai";
 import { z } from "zod";
 import { lhTool, toPiTools } from "../lh-tool.ts";
 import type { ModelRole } from "../../../config.ts";
-import { FACTORY_SETTINGS, ModelsNotConfiguredError, ROLE_SLOT, type ModelSlotName } from "../../core/settings.ts";
+import {
+	FACTORY_SETTINGS,
+	ModelsNotConfiguredError,
+	ProviderKeyMissingError,
+	ROLE_SLOT,
+	type ModelSlotName,
+	type ProviderKeyMissing,
+} from "../../core/settings.ts";
 import type { PiEngine } from "../models.ts";
 import { runSubagent } from "./pi-run.ts";
 import type {
@@ -566,6 +573,14 @@ export interface ExtractionModels {
 	 *  slot → NOTHING) may end EMPTY → undefined; the front doors refuse
 	 *  with ModelsNotConfiguredError before any stage runs. */
 	engineFor?: (role: ModelRole) => PiEngine | undefined;
+	/** Key-presence gate (provider-key interlude, 2026-09-25): given a
+	 *  stage engine's provider + the role's slot tier, the injected check
+	 *  returns the refusal envelope when the provider's key is missing
+	 *  (null = run). Same injection discipline as the job runner's seam
+	 *  (the agent layer may not read the key store); absent in tests that
+	 *  inject engines directly (test engines never owe a key). A keyless
+	 *  stage refuses with ProviderKeyMissingError BEFORE any batch runs. */
+	providerKeyMissing?: (provider: string, tier: ModelSlotName) => ProviderKeyMissing | null;
 }
 
 export interface ExtractionPipelineDeps extends GraphDeps, ExtractionModels {
@@ -623,15 +638,30 @@ export function createExtractionPipeline(deps: ExtractionPipelineDeps): Extracti
 	const stageEngine = (role: ModelRole, override?: PiEngine): PiEngine | undefined =>
 		override ?? deps.engineFor?.(role);
 	/** The per-need refusal guard: which slot tiers the pipeline's stages
-	 *  found unset (test values count as configured — they ARE engines). */
-	function refuseIfStagesUnconfigured(): void {
+	 *  found unset (test values count as configured — they ARE engines),
+	 *  and whether a configured stage's provider key is gone (provider-key
+	 *  interlude, 2026-09-25) — both refuse BEFORE any batch runs. */
+	function refuseIfStagesUnready(): void {
+		const stages: readonly [ModelRole, PiEngine | undefined][] = [
+			["extractor", stageEngine("extractor", deps.extractor)],
+			["auditor", stageEngine("auditor", deps.auditor)],
+		];
 		const missing = new Set<ModelSlotName>();
-		if (!stageEngine("extractor", deps.extractor)) missing.add(ROLE_SLOT.extractor);
-		if (!stageEngine("auditor", deps.auditor)) missing.add(ROLE_SLOT.auditor);
+		for (const [role, engine] of stages) if (!engine) missing.add(ROLE_SLOT[role]);
 		if (missing.size > 0) {
 			console.info(`[extraction] refused — no model configured for: ${[...missing].join(", ")}`);
 			throw new ModelsNotConfiguredError([...missing]);
 		}
+		// Key-presence parity: first offender surfaces (extractor before
+		// auditor); fixing that key re-gates and the next run surfaces the
+		// next offender, if any.
+		for (const [role, engine] of stages) {
+			const refusal = deps.providerKeyMissing?.(engine!.model.provider, ROLE_SLOT[role]);
+			if (refusal) {
+				console.info(`[extraction] refused — ${JSON.stringify(refusal)}`);
+				throw new ProviderKeyMissingError(refusal.provider, refusal.slots);
+			}
+		}
 	}
 	// THE SHARED REGISTRIES (runs() above — globalThis): every pipeline
 	// instance (route entries in dev, tests) sees the same runs, the same
@@ -758,10 +788,11 @@ export function createExtractionPipeline(deps: ExtractionPipelineDeps): Extracti
 		try {
 			const record = chatStore.getChat(chatId);
 			if (!record) throw new Error(`Chat not found: ${chatId}`);
-			// BYOK per-need gate (owner, 2026-09-22): the write channel needs
-			// extractor + auditor engines; an empty chain refuses BEFORE any
+			// BYOK per-need gate (owner, 2026-09-22) + key presence
+			// (2026-09-25): the write channel needs extractor + auditor
+			// engines AND their providers' keys; a refusal lands BEFORE any
 			// stage runs (typed — the trigger skips, routes surface 503).
-			refuseIfStagesUnconfigured();
+			refuseIfStagesUnready();
 			const covered = coverageOf(record.messages as UIMessage[], graphStore.readCoverage(), chatId);
 			if (covered.uncovered.length === 0) {
 				console.info(`[extraction ${chatId}] nothing uncovered — no-op`);
@@ -921,9 +952,10 @@ export function createExtractionPipeline(deps: ExtractionPipelineDeps): Extracti
 		inFlight.add(id);
 		const t0 = performance.now();
 		try {
-			// BYOK per-need gate (owner, 2026-09-22): same refusal as the chat
-			// front door — no extractor/auditor engines, no run.
-			refuseIfStagesUnconfigured();
+			// BYOK per-need gate (owner, 2026-09-22) + key presence
+			// (2026-09-25): same refusal as the chat front door — no
+			// extractor/auditor engines, or a stage key gone, no run.
+			refuseIfStagesUnready();
 			console.info(`[extraction ${id}] notes pipeline start (${input.filePath})`);
 			setPhase(id, "extracting", "notes", input.filePath);
 			const findings = await notesExtract(input);
diff --git a/src/agent/subagents/runner.ts b/src/agent/subagents/runner.ts
index 2a6671b..ca636f9 100644
--- a/src/agent/subagents/runner.ts
+++ b/src/agent/subagents/runner.ts
@@ -21,7 +21,7 @@ import {
 } from "../../core/contracts.ts";
 import { registerJobAbort, unregisterJobAbort } from "./aborts.ts";
 import type { ModelRole } from "../../../config.ts";
-import { ROLE_SLOT, modelsNotConfigured } from "../../core/settings.ts";
+import { ROLE_SLOT, modelsNotConfigured, type ModelSlotName, type ProviderKeyMissing } from "../../core/settings.ts";
 import type { ChatStore, JobStore } from "../../core/ports.ts";
 import { runDemoBuilder } from "./demo-builder.ts";
 import { runPdfReaderAgent } from "./pdf-reader.ts";
@@ -84,6 +84,12 @@ export interface JobRunnerDeps {
 	 *  drop (jobTools' searchAvailable) uses the same signal — jobs already
 	 *  in flight when a key disappears still fail honestly, never crash. */
 	searchProvider?: () => SearchProvider | null;
+	/** Key-presence gate (provider-key interlude, 2026-09-25): given the
+	 *  resolved engine's provider + the kind's slot tier, return the
+	 *  refusal envelope when the provider's key is missing (null = run).
+	 *  Injected because the agent layer may not read the key store; absent
+	 *  in tests that inject engines directly (test engines never owe a key). */
+	providerKeyMissing?: (provider: string, tier: ModelSlotName) => ProviderKeyMissing | null;
 }
 
 export interface JobRunner {
@@ -189,18 +195,15 @@ export function createJobRunner(deps: JobRunnerDeps): JobRunner {
 			return;
 		}
 		const engine = pickEngine(job.kind);
-		if (!engine) {
-			// BYOK per-need refusal (owner, 2026-09-22): this kind's tier has
-			// no model. Refuse through the SAME convention as every other
-			// failed job — record the honest error (no status flip:
-			// finalizeJob owns the terminal flip after delivery), then steer
-			// the kind's failure shape through finishJob so the wake
-			// pipeline resumes the lesson and the teacher reads the refusal
-			// instead of waiting forever on a job it already dispatched.
-			const tier = ROLE_SLOT[KIND_ROLE[job.kind]];
-			const envelope = modelsNotConfigured([tier]);
-			const reason = `${envelope.error} (missing: ${tier})`;
-			console.info(`[job ${jobId}] refused — ${JSON.stringify(envelope)}`);
+		// The per-need refusal guards (BYOK 2026-09-22 / provider-key
+		// interlude 2026-09-25): no engine for the kind's tier, or the
+		// resolved engine's provider key gone — both refuse through the SAME
+		// convention as every other failed job: record the honest error (no
+		// status flip: finalizeJob owns the terminal flip after delivery),
+		// then steer the kind's failure shape through finishJob so the wake
+		// pipeline resumes the lesson and the teacher reads the refusal
+		// instead of waiting forever on a job it already dispatched.
+		const refuse = async (reason: string): Promise<void> => {
 			if (stillRunning(jobId)) jobStore.updateJob(jobId, { error: reason });
 			const resolved = resolveInput(job, input) as
 				| ResearchToolInput
@@ -229,6 +232,23 @@ export function createJobRunner(deps: JobRunnerDeps): JobRunner {
 									pagesConsulted: [],
 								};
 			await finishJob(jobId, failure);
+		};
+		if (!engine) {
+			const tier = ROLE_SLOT[KIND_ROLE[job.kind]];
+			const envelope = modelsNotConfigured([tier]);
+			console.info(`[job ${jobId}] refused — ${JSON.stringify(envelope)}`);
+			await refuse(`${envelope.error} (missing: ${tier})`);
+			return;
+		}
+		// Key presence (2026-09-25): the engine exists, but its provider's
+		// key may be gone — refuse the spawn BEFORE the loop, same
+		// convention (the injected check reads the key store; absent in
+		// engine-injecting tests).
+		const keyRefusal =
+			deps.providerKeyMissing?.(engine.model.provider, ROLE_SLOT[KIND_ROLE[job.kind]]) ?? null;
+		if (keyRefusal) {
+			console.info(`[job ${jobId}] refused — ${JSON.stringify(keyRefusal)}`);
+			await refuse(keyRefusal.error);
 			return;
 		}
 		try {
diff --git a/src/core/settings.ts b/src/core/settings.ts
index 4316a4b..7b13e8c 100644
--- a/src/core/settings.ts
+++ b/src/core/settings.ts
@@ -28,6 +28,7 @@
  */
 
 import type { ThinkingLevel } from "@earendil-works/pi-agent-core";
+import { AUTH_PROVIDER_KEYS } from "./auth-keys.ts";
 import type { ModelRole } from "../../config.ts";
 import type { ChatSettings } from "./contracts/chat.ts";
 import type { SearchEngineId } from "./search.ts";
@@ -133,6 +134,56 @@ export class ModelsNotConfiguredError extends Error {
 	}
 }
 
+/** The key-presence refusal (provider-key interlude, owner, 2026-09-25):
+ * a PINNED model is not enough — its provider's key must be present, or
+ * the action dies mid-stream masked to a generic error. Same envelope
+ * family as modelsNotConfigured: HTTP callers get 503 + this JSON;
+ * in-band consumers (the job record's error field) carry the human
+ * `error` line. `provider` names whose key is gone; `slots` names the
+ * slot tier(s) the refused action resolves to that provider. */
+export const PROVIDER_KEY_MISSING_CODE = "provider_key_missing" as const;
+export interface ProviderKeyMissing {
+	/** Human-readable — safe to render as-is. */
+	error: string;
+	/** The machine discriminator the client switches on. */
+	code: typeof PROVIDER_KEY_MISSING_CODE;
+	/** The provider whose key is gone, e.g. "openrouter". */
+	provider: string;
+	/** Which slot tiers the refused action resolves to that provider. */
+	slots: ModelSlotName[];
+}
+/** The refusal wording's invariant tail — the matcher below keys on it
+ * (the label prefix varies by provider). */
+const PROVIDER_KEY_MISSING_TAIL = "key is set — add one in Settings → Keys";
+export function providerKeyMissing(provider: string, slots: ModelSlotName[]): ProviderKeyMissing {
+	const label = AUTH_PROVIDER_KEYS.find((p) => p.id === provider)?.label ?? provider;
+	return {
+		error: `No ${label} ${PROVIDER_KEY_MISSING_TAIL}`,
+		code: PROVIDER_KEY_MISSING_CODE,
+		provider,
+		slots,
+	};
+}
+/** The refusal error text (same discipline as isModelsRefusal): UI
+ * consumers detect key-refused work by the wording (info tone, not
+ * scary-error) — the envelope's home module owns the string so the
+ * writer and the matcher can never drift. */
+export function isProviderKeyRefusal(error: string | undefined): boolean {
+	return !!error && error.endsWith(PROVIDER_KEY_MISSING_TAIL);
+}
+/** The typed throw for in-process seams (extraction pipeline) — the
+ * ProviderKeyMissing sibling of ModelsNotConfiguredError: callers catch
+ * it to skip honestly (trigger) or surface the 503 envelope (routes). */
+export class ProviderKeyMissingError extends Error {
+	readonly envelope: ProviderKeyMissing;
+	constructor(provider: string, slots: ModelSlotName[]) {
+		const envelope = providerKeyMissing(provider, slots);
+		super(envelope.error);
+		this.name = "ProviderKeyMissingError";
+		this.envelope = envelope;
+	}
+}
+
 /** One slot's stored state. BYOK (owner, 2026-09-22): the WRITE side
  *  requires model (a level alone can never run — no factory floor); the
  *  sanitizer keeps whatever is on disk, but RESOLUTION treats a slot
diff --git a/src/server/chat-handler.ts b/src/server/chat-handler.ts
index 80d24fd..5c77728 100644
--- a/src/server/chat-handler.ts
+++ b/src/server/chat-handler.ts
@@ -10,13 +10,14 @@ import { recordToPiMessages } from "./pi/record-adapter.ts";
 import { createPiTurnResponse } from "./pi/ui-stream.ts";
 import { effectiveSettings, stores } from "./stores.ts";
 import { searchAvailable, searchProvider } from "./search.ts";
+import { providerKeyPresent } from "./keys.ts";
 import {
 	extractionEnabled,
 	graphToolsEnabled,
 	resolveConversationSpec,
 	resolveRoleSpec,
 } from "../core/settings-resolution.ts";
-import { modelsNotConfigured } from "../core/settings.ts";
+import { modelsNotConfigured, providerKeyMissing as providerKeyMissingEnvelope, type ProviderKeyMissing } from "../core/settings.ts";
 import { beginTurn, endTurn } from "./turn-liveness.ts";
 import { persistTurn, triggerExtraction, withMessageIds } from "./turn-service.ts";
 import type { CallUsage } from "../core/contracts.ts";
@@ -50,6 +51,12 @@ const jobRunner = createJobRunner({
 	// undefined and the runner refuses the spawn honestly.
 	engineFor: (role) =>
 		resolveEngine(role),
+	// Key-presence gate (provider-key interlude, 2026-09-25): the runner
+	// reads the resolved engine's provider and asks THIS check (the agent
+	// layer may not read the key store); a missing key refuses the spawn
+	// with the 503-envelope family instead of dying mid-run.
+	providerKeyMissing: (provider, tier) =>
+		providerKeyPresent(provider) ? null : providerKeyMissingEnvelope(provider, [tier]),
 	// Search port wave (2026-09-20): the researcher's web_search runs on the
 	// injected port — resolved FRESH per job (key rotations land immediately).
 	// null = honestly unavailable; the dispatch-level drop (below) uses the
@@ -67,6 +74,11 @@ export const extraction = createExtractionPipeline({
 	// with the typed ModelsNotConfiguredError. Direct test values still win.
 	engineFor: (role) =>
 		resolveEngine(role),
+	// Key-presence gate (provider-key interlude, 2026-09-25): same check
+	// the job runner gets — a stage engine whose provider key is gone
+	// refuses BEFORE any batch runs (the typed throw), never mid-run.
+	providerKeyMissing: (provider, tier) =>
+		providerKeyPresent(provider) ? null : providerKeyMissingEnvelope(provider, [tier]),
 });
 
 
@@ -151,6 +163,21 @@ export async function handleChatRequest(
 		return Response.json(envelope, { status: 503 });
 	}
 
+	// THE KEY-PRESENCE GATE (provider-key interlude, owner, 2026-09-25): a
+	// pinned model is not enough — its PROVIDER's key must be present, or
+	// the turn dies mid-stream masked to a generic error. Truth is env-first
+	// (providerKeyPresent reads what pi-ai would read at request time), so
+	// an env-shadowed key passes. Same placement discipline as the models
+	// gate: BEFORE beginTurn (no liveness effects) and the write-ahead
+	// persist (nothing durable changes); wake-pipeline turns ride the same
+	// path. The affected tier is strong — the conversation chain's own tier
+	// (a chat.model override still resolves through it).
+	if (!providerKeyPresent(conversation.provider)) {
+		const envelope = providerKeyMissingEnvelope(conversation.provider, ["strong"]);
+		console.info(`[chat ${chatId}] turn refused — ${JSON.stringify(envelope)}`);
+		return Response.json(envelope, { status: 503 });
+	}
+
 	// One turn per chat, ever. A second request while a turn runs means a
 	// stale/remounted client raced a live one — its message list is outdated,
 	// and letting it through would double-run the teacher and clobber the
diff --git a/src/server/keys.ts b/src/server/keys.ts
index 5779e2b..17e79d7 100644
--- a/src/server/keys.ts
+++ b/src/server/keys.ts
@@ -193,6 +193,17 @@ export function keyValue(id: string): string | undefined {
 	return process.env[id] ?? authStore.authVars()[id];
 }
 
+/** The key-presence truth for one model provider (provider-key interlude,
+ * 2026-09-25): would this provider's key be present at request time?
+ * Reads through keyValue — the SAME env-first lookup pi-ai performs
+ * natively at every request — so an env-shadowed key counts as present
+ * (gate by what would run). Providers absent from AUTH_PROVIDER_KEYS take
+ * no key at all: nothing to gate, present by definition. */
+export function providerKeyPresent(provider: string): boolean {
+	const info = AUTH_PROVIDER_KEYS.find((p) => p.id === provider);
+	return info ? keyValue(info.envVar) !== undefined : true;
+}
+
 /**
  * Save one key (PUT). Shape gate first (owner decision: bad pastes are
  * 400s, never stored), then the file write, then the env reflection. A
diff --git a/src/server/turn-service.ts b/src/server/turn-service.ts
index 568ba61..94a9318 100644
--- a/src/server/turn-service.ts
+++ b/src/server/turn-service.ts
@@ -20,7 +20,7 @@ import { withPlanBlocks } from "../core/plan-blocks.ts";
 import { coverageOf } from "../core/coverage.ts";
 import type { ChatStore, GraphStore } from "../core/ports.ts";
 import type { ExtractionPipeline } from "../agent/subagents/extraction.ts";
-import { ModelsNotConfiguredError } from "../core/settings.ts";
+import { ModelsNotConfiguredError, ProviderKeyMissingError } from "../core/settings.ts";
 
 /**
  * The canonical state write: the client owns the message list between turns
@@ -101,13 +101,18 @@ export function triggerExtraction(
 		const covered = coverageOf(record.messages as UIMessage[], deps.graphStore.readCoverage(), chatId);
 		if (covered.uncoveredTokens < chunkTokens) return;
 		void extraction.runExtraction(chatId).catch((err) => {
-			// BYOK (owner, 2026-09-22): an unconfigured write channel SKIPS
-			// (the coverage ledger keeps the messages uncovered — the next
-			// trigger retries once slots are set); only real failures log.
+			// BYOK (owner, 2026-09-22) + key presence (provider-key interlude,
+			// 2026-09-25): an unconfigured OR keyless write channel SKIPS (the
+			// coverage ledger keeps the messages uncovered — the next trigger
+			// retries once slots/keys are set); only real failures log.
 			if (err instanceof ModelsNotConfiguredError) {
 				console.info(`[chat ${chatId}] extraction skipped — ${err.envelope.error} (missing: ${err.envelope.missing.join(", ")})`);
 				return;
 			}
+			if (err instanceof ProviderKeyMissingError) {
+				console.info(`[chat ${chatId}] extraction skipped — ${err.envelope.error} (provider: ${err.envelope.provider})`);
+				return;
+			}
 			console.error(`[chat ${chatId}] extraction pipeline failed:`, err);
 		});
 	} catch (err) {
diff --git a/tests/byok-refusal.test.ts b/tests/byok-refusal.test.ts
index 7055728..e772666 100644
--- a/tests/byok-refusal.test.ts
+++ b/tests/byok-refusal.test.ts
@@ -2,7 +2,13 @@ import { describe, it } from "node:test";
 import assert from "node:assert/strict";
 import { parseModelsRefusal } from "../components/chat.tsx";
 import { prefillFromSlots, prefillLevelFromPin, setupStage } from "../components/setup-dialog.tsx";
-import { isModelsRefusal, modelsNotConfigured } from "../src/core/settings.ts";
+import {
+	isModelsRefusal,
+	isProviderKeyRefusal,
+	modelsNotConfigured,
+	providerKeyMissing,
+	PROVIDER_KEY_MISSING_CODE,
+} from "../src/core/settings.ts";
 import type { ModelCatalogEntry, ModelSlotName } from "../src/core/index.ts";
 
 /**
@@ -42,6 +48,35 @@ describe("isModelsRefusal — the job-record matcher", () => {
 	});
 });
 
+describe("providerKeyMissing — the envelope factory (provider-key interlude, 2026-09-25)", () => {
+	it("names the provider from the curated label and carries the exact machine code", () => {
+		const envelope = providerKeyMissing("openrouter", ["strong"]);
+		assert.deepEqual(envelope, {
+			error: "No OpenRouter key is set — add one in Settings → Keys",
+			code: PROVIDER_KEY_MISSING_CODE,
+			provider: "openrouter",
+			slots: ["strong"],
+		});
+		assert.equal(envelope.code, "provider_key_missing");
+	});
+
+	it("an unknown provider falls back to its raw id as the label", () => {
+		const envelope = providerKeyMissing("weird", ["cheap"]);
+		assert.equal(envelope.error, "No weird key is set — add one in Settings → Keys");
+	});
+});
+
+describe("isProviderKeyRefusal — the job-record matcher (provider-key interlude)", () => {
+	it("matches the envelope wording regardless of provider label, not real failures", () => {
+		assert.equal(isProviderKeyRefusal(providerKeyMissing("together", ["cheap"]).error), true);
+		assert.equal(isProviderKeyRefusal(providerKeyMissing("openai", ["strong"]).error), true);
+		assert.equal(isProviderKeyRefusal(""), false);
+		assert.equal(isProviderKeyRefusal(undefined), false);
+		assert.equal(isProviderKeyRefusal("FAILED: headless crashed"), false);
+		assert.equal(isProviderKeyRefusal(modelsNotConfigured(["strong"]).error), false, "the models refusal is a different failure");
+	});
+});
+
 describe("prefillFromSlots — the SetupDialog prefill (BYOK wave)", () => {
 	const entry = (id: string, provider: string): ModelCatalogEntry => ({
 		id,
diff --git a/tests/chat-flow.test.ts b/tests/chat-flow.test.ts
index 0407780..2f9a825 100644
--- a/tests/chat-flow.test.ts
+++ b/tests/chat-flow.test.ts
@@ -36,6 +36,11 @@ import type { TeachingAgent } from "../src/agent/teacher-agent.ts";
 import type { UIMessage } from "ai";
 import { PATHS } from "../config.ts";
 
+// The key-presence turn gate (provider-key interlude, 2026-09-25): scripted
+// turns pin openrouter per chat — the gate reads env-first truth, so the
+// key must be present in the test process like any real setup.
+process.env.OPENROUTER_API_KEY ??= "test-key-presence-gate";
+
 const QUIZ_INPUT = {
 	question: "Which planet is closest to the sun?",
 	options: [
@@ -612,3 +617,56 @@ describe("the BYOK turn gate (no factory floor — owner, 2026-09-22)", () => {
 		await drain(res);
 	});
 });
+
+// ─── the key-presence turn gate (provider-key interlude, owner, 2026-09-25) ─
+
+describe("the key-presence turn gate (provider-key interlude, 2026-09-25)", () => {
+	// The gate's truth is env-first (keyValue): in tests process.env is the
+	// WHOLE truth (the throwaway data dir has no auth.json), so each test
+	// pins its provider's env var explicitly and restores it after.
+	it("a pinned provider whose key is gone refuses with 503 provider_key_missing — nothing lingers", async () => {
+		const chat = chatStore.createChat("Test: keyless provider");
+		createdChats.push(chat.id);
+		const saved = process.env.TOGETHER_API_KEY;
+		delete process.env.TOGETHER_API_KEY;
+		try {
+			// The chat's own model override pins the provider — the same
+			// chain the strong slot rides. The gate fires BEFORE the engine
+			// build, so the fake model id never hits the catalog.
+			chatStore.saveSettings(chat.id, { model: { provider: "together", id: "no-such-model" } });
+			const firstUser = { id: "u1", role: "user", parts: [{ type: "text", text: "teach me something" }] };
+			const res = await handleChatRequest(post(chat.id, [firstUser]), agentFactory(scriptedTeacher(defaultLesson).engine));
+
+			assert.equal(res.status, 503, "the key-presence gate refuses before beginTurn");
+			const body = (await res.json()) as { error: string; code: string; provider: string; slots: string[] };
+			assert.equal(body.code, "provider_key_missing");
+			assert.equal(body.provider, "together", "the envelope names whose key is gone");
+			assert.deepEqual(body.slots, ["strong"], "the conversation tier is the affected slot");
+			assert.equal(body.error, "No Together key is set — add one in Settings → Keys", "the human line names the provider");
+			assert.equal(isTurnRunning(chat.id), false, "the refusal never registers a live turn");
+			assert.equal(chatStore.getChat(chat.id)!.messages.length, 0, "no write-ahead persist before the gate");
+		} finally {
+			if (saved !== undefined) process.env.TOGETHER_API_KEY = saved;
+		}
+	});
+
+	it("an env-present key passes the gate (gate by what would run)", async () => {
+		const chat = chatStore.createChat("Test: env-keyed provider");
+		createdChats.push(chat.id);
+		const saved = process.env.OPENAI_API_KEY;
+		process.env.OPENAI_API_KEY = "test-key-presence-gate";
+		try {
+			// A REAL catalog model: the engine build AFTER the gate must
+			// resolve — the injected agent replaces the loop, not the build.
+			chatStore.saveSettings(chat.id, { model: { provider: "openai", id: "gpt-4" } });
+			const firstUser = { id: "u1", role: "user", parts: [{ type: "text", text: "teach me something" }] };
+			const res = await handleChatRequest(post(chat.id, [firstUser]), agentFactory(scriptedTeacher(defaultLesson).engine));
+
+			assert.equal(res.status, 200, "the env-shadowed key counts as present — the turn runs");
+			await drain(res);
+		} finally {
+			if (saved !== undefined) process.env.OPENAI_API_KEY = saved;
+			else delete process.env.OPENAI_API_KEY;
+		}
+	});
+});
diff --git a/tests/demos.test.tsx b/tests/demos.test.tsx
index 2c80f6d..c3aaa9d 100644
--- a/tests/demos.test.tsx
+++ b/tests/demos.test.tsx
@@ -1,3 +1,4 @@
+
 /**
  * Demo + visual artifact tests (W6) — deterministic, zero network, no real
  * Chrome:
@@ -83,6 +84,13 @@ function testRunner() {
 }
 import { artifactRenderers } from "../components/artifacts/index.ts";
 
+// The key-presence turn gate (provider-key interlude, 2026-09-25): scripted
+// turns pin openrouter per chat — the gate reads env-first truth, so the
+// key must be present in the test process like any real setup.
+process.env.OPENROUTER_API_KEY ??= "test-key-presence-gate";
+
+
+
 const JOBS_DIR = path.join(PATHS.data, "jobs");
 const createdChats: string[] = [];
 const createdJobs: string[] = [];
diff --git a/tests/extraction.test.ts b/tests/extraction.test.ts
index 215c2ac..5817162 100644
--- a/tests/extraction.test.ts
+++ b/tests/extraction.test.ts
@@ -39,7 +39,7 @@ import type {
 } from "../src/core/contracts.ts";
 import type { GraphStore } from "../src/core/ports.ts";
 import { abortExtraction, createExtractionPipeline, extractionStatuses, transcriptView } from "../src/agent/subagents/extraction.ts";
-import { ModelsNotConfiguredError } from "../src/core/settings.ts";
+import { ModelsNotConfiguredError, ProviderKeyMissingError, providerKeyMissing, type ModelSlotName } from "../src/core/settings.ts";
 import { batchTag, coverageOf, coverageSlots } from "../src/core/coverage.ts";
 import { chatStore } from "../src/store/chats.ts";
 import { PATHS } from "../config.ts";
@@ -394,6 +394,54 @@ describe("the extraction pipeline (extractor → auditor → merger)", () => {
 		assert.equal(ledgers.readCoverage().length, 0);
 	});
 
+	it("key-presence refusal: a stage engine whose provider key is gone throws before any batch (provider-key interlude, 2026-09-25)", async () => {
+		const { chatId } = fixtureChat();
+		const ledgers = memoryLedgers();
+		const extractor = fauxEngine([]);
+		const auditor = fauxEngine([]);
+		const seen: Array<[string, ModelSlotName]> = [];
+		const pipeline = createExtractionPipeline({
+			chatStore,
+			graphStore: ledgers,
+			extractor,
+			auditor,
+			providerKeyMissing: (provider, tier) => {
+				seen.push([provider, tier]);
+				return providerKeyMissing(provider, [tier]);
+			},
+		});
+		await assert.rejects(pipeline.runExtraction(chatId), (err: unknown) => {
+			assert.ok(err instanceof ProviderKeyMissingError);
+			assert.equal(err.envelope.code, "provider_key_missing");
+			assert.equal(err.envelope.provider, extractor.model.provider, "the provider of the keyless engine");
+			assert.deepEqual(err.envelope.slots, ["cheap"], "extractor + auditor are the cheap tier");
+			return true;
+		});
+		// FIRST offender surfaces (extractor before auditor) — and nothing
+		// ran: the refusal lands before any batch, no coverage writes.
+		assert.deepEqual(seen, [[extractor.model.provider, "cheap"]]);
+		assert.equal(ledgers.readCoverage().length, 0);
+	});
+
+	it("key-presence pass-through: null from the check lets a stage through — the NEXT keyless stage surfaces (first-offender discipline)", async () => {
+		const { chatId } = fixtureChat();
+		const ledgers = memoryLedgers();
+		let calls = 0;
+		const pipeline = createExtractionPipeline({
+			chatStore,
+			graphStore: ledgers,
+			extractor: fauxEngine([]),
+			auditor: fauxEngine([]),
+			providerKeyMissing: (provider, tier) => (calls++ === 0 ? null : providerKeyMissing(provider, [tier])),
+		});
+		await assert.rejects(pipeline.runExtraction(chatId), (err: unknown) => {
+			assert.ok(err instanceof ProviderKeyMissingError, "the auditor's refusal surfaces after the extractor passed");
+			return true;
+		});
+		assert.equal(calls, 2, "both stages were checked, in order");
+		assert.equal(ledgers.readCoverage().length, 0);
+	});
+
 	it("the LLM cluster-namer is DEAD (wave 7): a merge mints no naming runs — labels are session names now", async () => {
 		const { chatId } = fixtureChat();
 		const ledgers = memoryLedgers();
diff --git a/tests/jobs.test.ts b/tests/jobs.test.ts
index 5446c8e..1aa9361 100644
--- a/tests/jobs.test.ts
+++ b/tests/jobs.test.ts
@@ -58,6 +58,7 @@ import { persistTurn, withMessageIds } from "../src/server/turn-service.ts";
 import { chatStore } from "../src/store/chats.ts";
 import { jobStore } from "../src/store/jobs.ts";
 import { createJobRunner, pdfModelOverride, researchModelOverride } from "../src/agent/subagents/runner.ts";
+import { providerKeyMissing, type ModelSlotName } from "../src/core/settings.ts";
 import type { PiEngine } from "../src/agent/models.ts";
 import type { SearchProvider } from "../src/core/search.ts";
 import { PATHS } from "../config.ts";
@@ -65,6 +66,11 @@ import { PATHS } from "../config.ts";
 const JOBS_DIR = path.join(PATHS.data, "jobs");
 
 const createdChats: string[] = [];
+
+// The key-presence turn gate (provider-key interlude, 2026-09-25): scripted
+// turns pin openrouter per chat — the gate reads env-first truth, so the
+// key must be present in the test process like any real setup.
+process.env.OPENROUTER_API_KEY ??= "test-key-presence-gate";
 const createdJobs: string[] = [];
 
 function trackChat(id: string) {
@@ -1391,3 +1397,56 @@ describe("BYOK job refusal (no factory floor)", () => {
 		assert.equal(result.sources.length, 0, "the failure result matches the research convention");
 	});
 });
+
+// ─── provider-key: the key-presence job refusal (owner, 2026-09-25) ─────────
+
+describe("provider-key job refusal (key-presence interlude)", () => {
+	it("an engine whose provider key is gone refuses the spawn — envelope wording, no phantom run", async () => {
+		const chat = chatStore.createChat("Test: keyless spawn");
+		trackChat(chat.id);
+		chatStore.saveMessages(chat.id, [
+			{ id: "u1", role: "user", parts: [{ type: "text", text: "hi" }] },
+			{
+				id: "a1",
+				role: "assistant",
+				parts: [{ type: "tool-research", toolCallId: "call-km1", state: "output-available", input: RESEARCH_INPUT, output: "Dispatched." }],
+			},
+		] as never);
+
+		const job = jobStore.createJob({ kind: "research", chatId: chat.id, toolCallId: "call-km1" });
+		trackJob(job.id);
+
+		const delivery = fakeDeliver();
+		// The chain RESOLVES (an engine exists) — the KEY is what's missing.
+		// The injected check is the server seam's stand-in: it sees the
+		// engine's provider + the kind's slot tier, exactly as wired.
+		const engine = fauxEngine([]);
+		const seen: Array<[string, ModelSlotName]> = [];
+		const runner = createJobRunner({
+			chatStore,
+			jobStore,
+			deliver: delivery.deliver,
+			engineFor: () => engine,
+			providerKeyMissing: (provider, tier) => {
+				seen.push([provider, tier]);
+				return providerKeyMissing(provider, [tier]);
+			},
+		});
+		await runner.runJob(job.id);
+
+		// The refusal lands through the SAME convention as every failed job:
+		// honest record, kind failure shape steered, terminal flip after.
+		const done = jobStore.getJob(job.id)!;
+		assert.equal(done.status, "error", "the job lands error, never a phantom run");
+		assert.equal(done.error, providerKeyMissing(engine.model.provider, ["cheap"]).error, "the envelope's error line verbatim");
+		assert.deepEqual(seen, [[engine.model.provider, "cheap"]], "the check saw the engine's provider + the researcher's tier");
+		assert.equal(delivery.steers.length, 1, "the refusal STEERED — the teacher is not stranded");
+		const text = delivery.steers[0]!.parts[0];
+		assert.ok(
+			text.type === "text" && text.text.includes(`Research failed: No ${engine.model.provider} key is set`),
+			"the steer carries the kind's failure shape",
+		);
+		const result = done.result as ResearchResult;
+		assert.equal(result.sources.length, 0, "the failure result matches the research convention");
+	});
+});