diff --git a/src/resources/extensions/sf/auto-dispatch.ts b/src/resources/extensions/sf/auto-dispatch.ts
index d494ff2a9..17454a9b9 100644
--- a/src/resources/extensions/sf/auto-dispatch.ts
+++ b/src/resources/extensions/sf/auto-dispatch.ts
@@ -67,6 +67,7 @@ import {
 import type { SFState } from "./types.js";
 import { selectReactiveDispatchBatch } from "./uok/execution-graph.js";
 import { resolveUokFlags } from "./uok/flags.js";
+import { UokGateRunner } from "./uok/gate-runner.js";
 import { EXECUTION_ENTRY_PHASES } from "./uok/plan-v2.js";
 import { extractVerdict, isAcceptableUatVerdict } from "./verdict-parser.js";
 import { logError, logWarning } from "./workflow-logger.js";
@@ -960,6 +961,7 @@ export const DISPATCH_RULES: DispatchRule[] = [
 			// execution remains sequential
 			if (maxParallel <= 1) return null;
 
+			const uokFlags = resolveUokFlags(prefs);
 			try {
 				const {
 					loadSliceTaskIO,
@@ -984,8 +986,6 @@ export const DISPATCH_RULES: DispatchRule[] = [
 
 				// Only activate reactive dispatch when >1 task is ready
 				if (readyIds.length <= 1) return null;
-
-				const uokFlags = resolveUokFlags(prefs);
 				const selected = uokFlags.executionGraph
 					? selectReactiveDispatchBatch({
 							graph,
@@ -1033,9 +1033,36 @@ export const DISPATCH_RULES: DispatchRule[] = [
 				};
 			} catch (err) {
 				// Non-fatal — fall through to sequential execution
+				const errMsg = (err as Error).message;
 				logError("dispatch", "reactive graph derivation failed", {
-					error: (err as Error).message,
+					error: errMsg,
 				});
+				// Persist execution-graph failure to gate audit when gates are enabled
+				if (uokFlags.executionGraph && uokFlags.gates) {
+					const egRunner = new UokGateRunner();
+					egRunner.register({
+						id: "execution-graph-gate",
+						type: "execution",
+						execute: async () => ({
+							outcome: "fail" as const,
+							failureClass: "execution" as const,
+							rationale: "reactive graph derivation failed — falling back to sequential",
+							findings: errMsg,
+						}),
+					});
+					egRunner
+						.run("execution-graph-gate", {
+							basePath,
+							traceId: `dispatch:${mid}/${sid}`,
+							turnId: `${mid}/${sid}`,
+							milestoneId: mid,
+							sliceId: sid,
+							unitType: "reactive-execute",
+						})
+						.catch(() => {
+							/* gate telemetry must never block dispatch */
+						});
+				}
 				return null;
 			}
 		},
diff --git a/src/resources/extensions/sf/auto-worktree.ts b/src/resources/extensions/sf/auto-worktree.ts
index 055fa0238..3d90f3fea 100644
--- a/src/resources/extensions/sf/auto-worktree.ts
+++ b/src/resources/extensions/sf/auto-worktree.ts
@@ -983,6 +983,7 @@ function syncMilestoneDir(
  * Failure is non-fatal — returns the error message or null on success.
  *
  * Reads the hook path from git.worktree_post_create in preferences.
+ * Also runs workspace.after_create (inline shell script) if configured.
  * Pass hookPath directly to bypass preference loading (useful for testing).
  */
 export function runWorktreePostCreateHook(
@@ -990,53 +991,85 @@ export function runWorktreePostCreateHook(
 	worktreeDir: string,
 	hookPath?: string,
 ): string | null {
-	if (hookPath === undefined) {
-		const prefs = loadEffectiveSFPreferences()?.preferences?.git;
-		hookPath = prefs?.worktree_post_create;
-	}
-	if (!hookPath) return null;
+	const errors: string[] = [];
 
-	// Resolve relative paths against the source project root.
-	// On Windows, convert 8.3 short paths (e.g. RUNNER~1) to long paths
-	// so execFileSync can locate the file correctly.
-	let resolved = isAbsolute(hookPath) ? hookPath : join(sourceDir, hookPath);
-	if (!existsSync(resolved)) {
-		return `Worktree post-create hook not found: ${resolved}`;
+	// ── Legacy file-path hook (git.worktree_post_create) ─────────────────────
+	let resolvedHookPath = hookPath;
+	if (resolvedHookPath === undefined) {
+		const prefs = loadEffectiveSFPreferences()?.preferences?.git;
+		resolvedHookPath = prefs?.worktree_post_create;
 	}
-	if (process.platform === "win32") {
-		try {
-			resolved = realpathSync.native(resolved);
-		} catch (err) {
-			/* keep original */
-			logWarning(
-				"worktree",
-				`realpath failed: ${err instanceof Error ? err.message : String(err)}`,
-			);
+	if (resolvedHookPath) {
+		// Resolve relative paths against the source project root.
+		// On Windows, convert 8.3 short paths (e.g. RUNNER~1) to long paths
+		// so execFileSync can locate the file correctly.
+		let resolved = isAbsolute(resolvedHookPath)
+			? resolvedHookPath
+			: join(sourceDir, resolvedHookPath);
+		if (!existsSync(resolved)) {
+			errors.push(`Worktree post-create hook not found: ${resolved}`);
+		} else {
+			if (process.platform === "win32") {
+				try {
+					resolved = realpathSync.native(resolved);
+				} catch (err) {
+					/* keep original */
+					logWarning(
+						"worktree",
+						`realpath failed: ${err instanceof Error ? err.message : String(err)}`,
+					);
+				}
+			}
+			try {
+				// .bat/.cmd files on Windows require shell mode — execFileSync cannot
+				// spawn them directly (EINVAL).
+				const needsShell =
+					process.platform === "win32" && /\.(bat|cmd)$/i.test(resolved);
+				execFileSync(resolved, [], {
+					cwd: worktreeDir,
+					env: {
+						...process.env,
+						SOURCE_DIR: sourceDir,
+						WORKTREE_DIR: worktreeDir,
+					},
+					stdio: ["ignore", "pipe", "pipe"],
+					encoding: "utf-8",
+					timeout: 30_000,
+					shell: needsShell,
+				});
+			} catch (err) {
+				const msg = err instanceof Error ? err.message : String(err);
+				errors.push(`Worktree post-create hook failed: ${msg}`);
+			}
 		}
 	}
 
-	try {
-		// .bat/.cmd files on Windows require shell mode — execFileSync cannot
-		// spawn them directly (EINVAL).
-		const needsShell =
-			process.platform === "win32" && /\.(bat|cmd)$/i.test(resolved);
-		execFileSync(resolved, [], {
-			cwd: worktreeDir,
-			env: {
-				...process.env,
-				SOURCE_DIR: sourceDir,
-				WORKTREE_DIR: worktreeDir,
-			},
-			stdio: ["ignore", "pipe", "pipe"],
-			encoding: "utf-8",
-			timeout: 30_000, // 30 second timeout
-			shell: needsShell,
-		});
-		return null;
-	} catch (err) {
-		const msg = err instanceof Error ? err.message : String(err);
-		return `Worktree post-create hook failed: ${msg}`;
+	// ── Inline script hook (workspace.after_create) ───────────────────────────
+	// Only read from prefs when hookPath was not passed explicitly (testing path).
+	if (hookPath === undefined) {
+		const afterCreate =
+			loadEffectiveSFPreferences()?.preferences?.workspace?.after_create;
+		if (afterCreate) {
+			try {
+				execFileSync("sh", ["-c", afterCreate], {
+					cwd: worktreeDir,
+					env: {
+						...process.env,
+						SOURCE_DIR: sourceDir,
+						WORKTREE_DIR: worktreeDir,
+					},
+					stdio: ["ignore", "pipe", "pipe"],
+					encoding: "utf-8",
+					timeout: 60_000,
+				});
+			} catch (err) {
+				const msg = err instanceof Error ? err.message : String(err);
+				errors.push(`workspace.after_create hook failed: ${msg}`);
+			}
+		}
 	}
+
+	return errors.length > 0 ? errors.join("; ") : null;
 }
 
 // ─── Auto-Worktree Branch Naming ───────────────────────────────────────────
diff --git a/src/resources/extensions/sf/auto/phases.ts b/src/resources/extensions/sf/auto/phases.ts
index b54f8597d..34ad1ace0 100644
--- a/src/resources/extensions/sf/auto/phases.ts
+++ b/src/resources/extensions/sf/auto/phases.ts
@@ -43,7 +43,11 @@ import { debugLog } from "../debug-logger.js";
 import { PROJECT_FILES } from "../detection.js";
 import { MergeConflictError } from "../git-service.js";
 import { recordLearnedOutcome } from "../learning/runtime.js";
-import { sfRoot } from "../paths.js";
+import {
+	resolveMilestoneFile,
+	resolveSliceFile,
+	sfRoot,
+} from "../paths.js";
 import { resolvePersistModelChanges } from "../preferences.js";
 import {
 	approveProductionMutationWithLlmPolicy,
@@ -667,6 +671,7 @@ export async function runPreDispatch(
 					const result = await startSliceParallel(s.basePath, mid, eligible, {
 						maxWorkers: prefs.slice_parallel.max_workers ?? 2,
 						useExecutionGraph: uokFlags.executionGraph,
+						shellWrapper: prefs.shell_wrapper,
 					});
 					if (result.started.length > 0) {
 						ctx.ui.notify(
@@ -1354,6 +1359,67 @@ export async function runDispatch(
 		return { action: "break", reason: "prior-slice-blocker" };
 	}
 
+	// ── UOK Plan-gate ──────────────────────────────────────────────────────────
+	// Structural validation before execute-task units: confirms the plan files
+	// exist. FailureClass "input" → 0 retries (broken plan needs human fix, not
+	// an LLM retry). Only fires when uok.gates.enabled is true.
+	const uokFlagsDispatch = resolveUokFlags(prefs);
+	if (uokFlagsDispatch.gates && unitType === "execute-task") {
+		let planGateOutcome: "pass" | "fail" = "pass";
+		let planGateRationale = "";
+
+		if (!mid) {
+			planGateOutcome = "fail";
+			planGateRationale = "No active milestone for execute-task dispatch";
+		} else {
+			const roadmapPath = resolveMilestoneFile(s.basePath, mid, "ROADMAP");
+			if (!roadmapPath || !existsSync(roadmapPath)) {
+				planGateOutcome = "fail";
+				planGateRationale = `Milestone roadmap not found for ${mid}`;
+			} else if (state.activeSlice?.id) {
+				const slicePlanPath = resolveSliceFile(
+					s.basePath,
+					mid,
+					state.activeSlice.id,
+					"PLAN",
+				);
+				if (!slicePlanPath || !existsSync(slicePlanPath)) {
+					planGateOutcome = "fail";
+					planGateRationale = `Slice plan not found for ${mid}/${state.activeSlice.id}`;
+				}
+			}
+		}
+
+		const planGateRunner = new UokGateRunner();
+		planGateRunner.register({
+			id: "plan-gate",
+			type: "policy",
+			execute: async () => ({
+				outcome: planGateOutcome,
+				failureClass: planGateOutcome === "pass" ? "none" : "input",
+				rationale: planGateRationale || "Plan files verified",
+			}),
+		});
+		const planGateResult = await planGateRunner.run("plan-gate", {
+			basePath: s.basePath,
+			traceId: `dispatch:${ic.flowId}`,
+			turnId: `iter-${ic.iteration}`,
+			milestoneId: mid ?? undefined,
+			sliceId: state.activeSlice?.id ?? undefined,
+			unitType,
+			unitId,
+		});
+		if (planGateResult.outcome !== "pass") {
+			ctx.ui.notify(
+				`Plan gate: ${planGateResult.rationale ?? "plan validation failed"} — pausing.`,
+				"warning",
+			);
+			await deps.pauseAuto(ctx, pi);
+			debugLog("autoLoop", { phase: "exit", reason: "plan-gate-failed" });
+			return { action: "break", reason: "plan-gate-failed" };
+		}
+	}
+
 	return {
 		action: "next",
 		data: {
@@ -2647,6 +2713,34 @@ export async function runFinalize(
 	// Hook sidecar items skip verification entirely.
 	// Non-hook sidecar items run verification but skip retries (just continue).
 	const skipVerification = sidecarItem?.kind === "hook";
+	const uokFlagsFinalize = resolveUokFlags(ic.prefs);
+	const runVerifyGate =
+		uokFlagsFinalize.gates &&
+		iterData.unitType === "execute-task" &&
+		!skipVerification;
+
+	async function emitVerificationGate(
+		outcome: "pass" | "fail",
+		failureClass: "none" | "verification" | "manual-attention",
+		rationale: string,
+	): Promise<void> {
+		if (!runVerifyGate) return;
+		const vgRunner = new UokGateRunner();
+		vgRunner.register({
+			id: "unit-verification-gate",
+			type: "verification",
+			execute: async () => ({ outcome, failureClass, rationale }),
+		});
+		await vgRunner.run("unit-verification-gate", {
+			basePath: s.basePath,
+			traceId: `finalize:${ic.flowId}`,
+			turnId: `iter-${ic.iteration}`,
+			milestoneId: iterData.mid ?? undefined,
+			unitType: iterData.unitType,
+			unitId: iterData.unitId,
+		});
+	}
+
 	if (!skipVerification) {
 		const verificationResult = await deps.runPostUnitVerification(
 			{ s, ctx, pi },
@@ -2664,6 +2758,11 @@ export async function runFinalize(
 					verificationPassed: false,
 				},
 			);
+			await emitVerificationGate(
+				"fail",
+				"manual-attention",
+				"Post-unit verification paused — requires human attention",
+			);
 			debugLog("autoLoop", { phase: "exit", reason: "verification-pause" });
 			return { action: "break", reason: "verification-pause" };
 		}
@@ -2679,6 +2778,11 @@ export async function runFinalize(
 					verificationPassed: false,
 				},
 			);
+			await emitVerificationGate(
+				"fail",
+				"verification",
+				"Post-unit verification failed — retrying unit",
+			);
 			if (sidecarItem) {
 				// Sidecar verification retries are skipped — just continue
 				debugLog("autoLoop", {
@@ -2695,6 +2799,9 @@ export async function runFinalize(
 				return { action: "continue" };
 			}
 		}
+
+		// Verification passed — record gate pass for audit/db
+		await emitVerificationGate("pass", "none", "Post-unit verification passed");
 	}
 
 	// Post-verification processing (DB dual-write, hooks, triage, quick-tasks)
diff --git a/src/resources/extensions/sf/guided-flow.ts b/src/resources/extensions/sf/guided-flow.ts
index 874387acb..968307ea1 100644
--- a/src/resources/extensions/sf/guided-flow.ts
+++ b/src/resources/extensions/sf/guided-flow.ts
@@ -84,6 +84,7 @@ import {
 	listUnitRuntimeRecords,
 } from "./unit-runtime.js";
 import { resolveUokFlags } from "./uok/flags.js";
+import { UokGateRunner } from "./uok/gate-runner.js";
 import { ensurePlanV2Graph as ensurePlanningFlowGraph } from "./uok/plan-v2.js";
 import { validateDirectory } from "./validate-directory.js";
 import {
@@ -172,23 +173,58 @@ function needsPlanningFlowGate(state: SFState): boolean {
 	);
 }
 
-function runPlanningFlowGate(
+async function runPlanningFlowGate(
 	ctx: ExtensionContext,
 	basePath: string,
 	state: SFState,
-): boolean {
+): Promise<boolean> {
 	const prefs = loadEffectiveSFPreferences()?.preferences;
 	const uokFlags = resolveUokFlags(prefs);
 	if (!uokFlags.planningFlow || !needsPlanningFlowGate(state)) return true;
 	const compiled = ensurePlanningFlowGraph(basePath, state);
+
+	const milestoneId = state.activeMilestone?.id ?? undefined;
+	const traceId = `guided-flow:${milestoneId ?? "unknown"}`;
+	const turnId = `guided-${Date.now()}`;
+
+	const persistGate = async (
+		outcome: "pass" | "manual-attention",
+		failureClass: "none" | "manual-attention",
+		rationale: string,
+		findings = "",
+	): Promise<void> => {
+		if (!uokFlags.gates) return;
+		const gateRunner = new UokGateRunner();
+		gateRunner.register({
+			id: "planning-flow-gate",
+			type: "policy",
+			execute: async () => ({ outcome, failureClass, rationale, findings }),
+		});
+		await gateRunner.run("planning-flow-gate", {
+			basePath,
+			traceId,
+			turnId,
+			milestoneId,
+			unitType: "pre-dispatch",
+			unitId: "guided-flow",
+		});
+	};
+
 	if (!compiled.ok) {
 		const reason = compiled.reason ?? "planning-flow compilation failed";
+		await persistGate(
+			"manual-attention",
+			"manual-attention",
+			"planning flow compile gate failed",
+			reason,
+		);
 		ctx.ui.notify(
 			`Plan gate failed-closed: ${reason}. Complete plan/discuss artifacts before execution.`,
 			"error",
 		);
 		return false;
 	}
+	await persistGate("pass", "none", "planning flow compile gate passed");
 	return true;
 }
 
@@ -1862,7 +1898,7 @@ export async function showWorkflowEntry(
 		logWarning("guided", `STATE.md rebuild failed: ${(err as Error).message}`);
 	}
 
-	if (!runPlanningFlowGate(ctx, basePath, state)) return;
+	if (!(await runPlanningFlowGate(ctx, basePath, state))) return;
 
 	if (!state.activeMilestone?.id) {
 		// Guard: if a discuss session is already in flight, don't re-inject the prompt.
diff --git a/src/resources/extensions/sf/parallel-orchestrator.ts b/src/resources/extensions/sf/parallel-orchestrator.ts
index 2c02dc360..cd07e671c 100644
--- a/src/resources/extensions/sf/parallel-orchestrator.ts
+++ b/src/resources/extensions/sf/parallel-orchestrator.ts
@@ -668,7 +668,22 @@ export function spawnWorker(basePath: string, milestoneId: string): boolean {
 			workerEnv.SF_WORKER_MODEL = state.config.worker_model;
 		}
 
-		child = spawn(process.execPath, [binPath, "headless", "--json", "auto"], {
+		const shellWrapper = state.config.shell_wrapper ?? [];
+		const [spawnCmd, spawnArgs] =
+			shellWrapper.length > 0
+				? [
+						shellWrapper[0],
+						[
+							...shellWrapper.slice(1),
+							process.execPath,
+							binPath,
+							"headless",
+							"--json",
+							"auto",
+						],
+					]
+				: [process.execPath, [binPath, "headless", "--json", "auto"]];
+		child = spawn(spawnCmd, spawnArgs, {
 			cwd: worker.worktreePath,
 			env: workerEnv,
 			stdio: ["ignore", "pipe", "pipe"],
diff --git a/src/resources/extensions/sf/preferences-types.ts b/src/resources/extensions/sf/preferences-types.ts
index 2417afddc..0402a2279 100644
--- a/src/resources/extensions/sf/preferences-types.ts
+++ b/src/resources/extensions/sf/preferences-types.ts
@@ -148,6 +148,8 @@ export const KNOWN_PREFERENCE_KEYS = new Set<string>([
 	"discuss_web_research",
 	"discuss_depth",
 	"flat_rate_providers",
+	"shell_wrapper",
+	"workspace",
 ]);
 
 /** Canonical list of all dispatch unit types. */
@@ -614,6 +616,39 @@ export interface SFPreferences {
 	 * `provider_model_allow`.
 	 */
 	provider_model_block?: Record<string, string[]>;
+
+	/**
+	 * Shell wrapper prepended when SF spawns sub-processes (parallel milestone
+	 * workers, slice workers). Useful for projects that require a specific shell
+	 * environment such as a Nix development shell.
+	 *
+	 * Each element is a separate argument. The worker is launched as:
+	 *   shell_wrapper[0] [...shell_wrapper.slice(1)] <node> <sf-loader> headless ...
+	 *
+	 * Example for NixOS projects:
+	 *   shell_wrapper:
+	 *     - nix
+	 *     - develop
+	 *     - --command
+	 */
+	shell_wrapper?: string[];
+
+	/**
+	 * Workspace lifecycle hooks. Shell scripts run at key points in the
+	 * worktree lifecycle (inspired by Symphony's hooks model).
+	 *
+	 * Scripts run via `sh -c` in the worktree directory. Failures are logged;
+	 * `after_create` failure is fatal to worktree creation, `after_run` is
+	 * best-effort.
+	 */
+	workspace?: {
+		/** Runs once when a new worktree is first created. Failure aborts creation. */
+		after_create?: string;
+		/** Runs before each task dispatch inside the worktree. Failure aborts the task. */
+		before_run?: string;
+		/** Runs after each task completes (success or failure). Best-effort. */
+		after_run?: string;
+	};
 }
 
 export interface LoadedSFPreferences {
diff --git a/src/resources/extensions/sf/preferences-validation.ts b/src/resources/extensions/sf/preferences-validation.ts
index c0278dc1a..b7c75a627 100644
--- a/src/resources/extensions/sf/preferences-validation.ts
+++ b/src/resources/extensions/sf/preferences-validation.ts
@@ -700,6 +700,41 @@ export function validatePreferences(preferences: SFPreferences): {
 		}
 	}
 
+	// ─── Shell Wrapper ───────────────────────────────────────────────────
+	if (preferences.shell_wrapper !== undefined) {
+		if (
+			Array.isArray(preferences.shell_wrapper) &&
+			preferences.shell_wrapper.every((s) => typeof s === "string" && s.length > 0)
+		) {
+			validated.shell_wrapper = preferences.shell_wrapper as string[];
+		} else {
+			errors.push("shell_wrapper must be an array of non-empty strings");
+		}
+	}
+
+	// ─── Workspace Lifecycle Hooks ───────────────────────────────────────
+	if (preferences.workspace !== undefined) {
+		if (
+			typeof preferences.workspace === "object" &&
+			preferences.workspace !== null
+		) {
+			const ws = preferences.workspace as Record<string, unknown>;
+			const validatedWs: NonNullable<typeof validated.workspace> = {};
+			for (const key of ["after_create", "before_run", "after_run"] as const) {
+				if (ws[key] !== undefined) {
+					if (typeof ws[key] === "string") {
+						validatedWs[key] = ws[key] as string;
+					} else {
+						errors.push(`workspace.${key} must be a string`);
+					}
+				}
+			}
+			validated.workspace = validatedWs;
+		} else {
+			errors.push("workspace must be an object");
+		}
+	}
+
 	// ─── Phase Skip Preferences ─────────────────────────────────────────
 	if (preferences.phases !== undefined) {
 		if (typeof preferences.phases === "object" && preferences.phases !== null) {
diff --git a/src/resources/extensions/sf/preferences.ts b/src/resources/extensions/sf/preferences.ts
index d68334ae8..99dd43f5a 100644
--- a/src/resources/extensions/sf/preferences.ts
+++ b/src/resources/extensions/sf/preferences.ts
@@ -862,5 +862,6 @@ export function resolveParallelConfig(
 		auto_merge: prefs?.parallel?.auto_merge ?? "confirm",
 		worker_model: prefs?.parallel?.worker_model,
 		worker_timeout_minutes: prefs?.parallel?.worker_timeout_minutes,
+		shell_wrapper: prefs?.shell_wrapper,
 	};
 }
diff --git a/src/resources/extensions/sf/slice-parallel-orchestrator.ts b/src/resources/extensions/sf/slice-parallel-orchestrator.ts
index 56e125ed2..052b7e113 100644
--- a/src/resources/extensions/sf/slice-parallel-orchestrator.ts
+++ b/src/resources/extensions/sf/slice-parallel-orchestrator.ts
@@ -17,6 +17,7 @@ import { type ChildProcess, spawn } from "node:child_process";
 import { appendFileSync, existsSync, mkdirSync } from "node:fs";
 import { dirname, join } from "node:path";
 import { fileURLToPath } from "node:url";
+import { runWorktreePostCreateHook } from "./auto-worktree.js";
 import { getErrorMessage } from "./error-utils.js";
 import { sfRoot } from "./paths.js";
 import { writeSessionStatus } from "./session-status-io.js";
@@ -52,12 +53,14 @@ export interface SliceOrchestratorState {
 	maxWorkers: number;
 	startedAt: number;
 	basePath: string;
+	shellWrapper?: string[];
 }
 
 export interface StartSliceParallelOpts {
 	maxWorkers?: number;
 	budgetCeiling?: number;
 	useExecutionGraph?: boolean;
+	shellWrapper?: string[];
 }
 
 // ─── Module State ──────────────────────────────────────────────────────────
@@ -120,6 +123,7 @@ export async function startSliceParallel(
 		maxWorkers,
 		startedAt: Date.now(),
 		basePath,
+		shellWrapper: opts.shellWrapper,
 	};
 
 	const started: string[] = [];
@@ -145,6 +149,10 @@ export async function startSliceParallel(
 
 			if (!existsSync(wtPath)) {
 				createWorktree(basePath, wtName, { branch: wtBranch });
+				const hookError = runWorktreePostCreateHook(basePath, wtPath);
+				if (hookError) {
+					logWarning("parallel", hookError, { worktree: wtName });
+				}
 			}
 
 			// Create worker info
@@ -346,22 +354,27 @@ function spawnSliceWorker(
 
 	let child: ChildProcess;
 	try {
-		child = spawn(
-			process.execPath,
-			[binPath, "--mode", "json", "--print", "/sf autonomous"],
-			{
-				cwd: worker.worktreePath,
-				env: {
-					...process.env,
-					SF_SLICE_LOCK: sliceId,
-					SF_MILESTONE_LOCK: milestoneId,
-					SF_PROJECT_ROOT: basePath,
-					SF_PARALLEL_WORKER: "1",
-				},
-				stdio: ["ignore", "pipe", "pipe"],
-				detached: false,
+		const shellWrapper = sliceState.shellWrapper ?? [];
+		const workerArgs = [binPath, "--mode", "json", "--print", "/sf autonomous"];
+		const [spawnCmd, spawnArgs] =
+			shellWrapper.length > 0
+				? [
+						shellWrapper[0],
+						[...shellWrapper.slice(1), process.execPath, ...workerArgs],
+					]
+				: [process.execPath, workerArgs];
+		child = spawn(spawnCmd, spawnArgs, {
+			cwd: worker.worktreePath,
+			env: {
+				...process.env,
+				SF_SLICE_LOCK: sliceId,
+				SF_MILESTONE_LOCK: milestoneId,
+				SF_PROJECT_ROOT: basePath,
+				SF_PARALLEL_WORKER: "1",
 			},
-		);
+			stdio: ["ignore", "pipe", "pipe"],
+			detached: false,
+		});
 	} catch (e) {
 		logWarning(
 			"parallel",
diff --git a/src/resources/extensions/sf/types.ts b/src/resources/extensions/sf/types.ts
index bb3bb59be..0e63737d9 100644
--- a/src/resources/extensions/sf/types.ts
+++ b/src/resources/extensions/sf/types.ts
@@ -469,6 +469,12 @@ export interface ParallelConfig {
 	worker_model?: string;
 	/** Minutes before a running worker is killed as hung. Default: 120. */
 	worker_timeout_minutes?: number;
+	/**
+	 * Shell wrapper prepended to sub-process spawns. When set, each worker
+	 * process is launched as: shell_wrapper[0] [...shell_wrapper.slice(1)] node sf ...
+	 * Example: ["nix", "develop", "--command"] for NixOS projects.
+	 */
+	shell_wrapper?: string[];
 }
 
 // ─── Reactive Task Execution Types ───────────────────────────────────────
diff --git a/src/resources/extensions/sf/uok/contracts.ts b/src/resources/extensions/sf/uok/contracts.ts
index 9c1b1197c..16b074d2f 100644
--- a/src/resources/extensions/sf/uok/contracts.ts
+++ b/src/resources/extensions/sf/uok/contracts.ts
@@ -113,7 +113,8 @@ export type UokNodeKind =
 	| "subagent"
 	| "team-worker"
 	| "verification"
-	| "reprocess";
+	| "reprocess"
+	| "refine";
 
 export interface UokGraphNode {
 	id: string;
@@ -124,6 +125,71 @@ export interface UokGraphNode {
 	metadata?: Record<string, unknown>;
 }
 
+export type DispatchReasonCode =
+	| "policy"
+	| "state"
+	| "recovery"
+	| "manual"
+	| "dependency"
+	| "conflict"
+	| "retry";
+
+export interface DispatchExplanation {
+	reasonCode: DispatchReasonCode;
+	summary: string;
+	evidence?: Record<string, unknown>;
+	blockedBy?: Array<{
+		kind: "gate" | "state" | "dependency" | "conflict" | "policy" | "manual";
+		id: string;
+		detail?: string;
+	}>;
+}
+
+export interface UokDispatchEnvelope {
+	action: "dispatch" | "stop" | "skip";
+	nodeKind?: UokNodeKind;
+	unitType?: string;
+	unitId?: string;
+	prompt?: string;
+	reason: DispatchExplanation;
+	gateVerdict?: GateResult;
+	constraints?: {
+		reads?: string[];
+		writes?: string[];
+		dependsOn?: string[];
+		maxWorkers?: number;
+	};
+	trace?: {
+		traceId?: string;
+		turnId?: string;
+		causedBy?: string;
+	};
+}
+
+export interface WriterToken {
+	tokenId: string;
+	traceId: string;
+	turnId: string;
+	acquiredAt: string;
+	owner: "uok" | "legacy-compat" | "manual";
+}
+
+export interface WriteSequence {
+	traceId: string;
+	turnId: string;
+	sequence: number;
+}
+
+export interface WriteRecord {
+	writerToken: WriterToken;
+	sequence: WriteSequence;
+	category: "state" | "audit" | "gitops" | "gate" | "artifact" | "other";
+	path?: string;
+	operation: "append" | "replace" | "insert" | "update" | "delete" | "noop";
+	ts: string;
+	metadata?: Record<string, unknown>;
+}
+
 export interface UokTurnObserver {
 	onTurnStart(contract: TurnContract): void;
 	onPhaseResult(
diff --git a/src/resources/extensions/sf/uok/dispatch-envelope.ts b/src/resources/extensions/sf/uok/dispatch-envelope.ts
new file mode 100644
index 000000000..8ef50f207
--- /dev/null
+++ b/src/resources/extensions/sf/uok/dispatch-envelope.ts
@@ -0,0 +1,58 @@
+import type {
+	DispatchExplanation,
+	DispatchReasonCode,
+	GateResult,
+	UokDispatchEnvelope,
+	UokGraphNode,
+} from "./contracts.js";
+
+export interface BuildDispatchEnvelopeInput {
+	action: UokDispatchEnvelope["action"];
+	node?: Pick<UokGraphNode, "kind" | "reads" | "writes" | "dependsOn">;
+	unitType?: string;
+	unitId?: string;
+	prompt?: string;
+	reasonCode: DispatchReasonCode;
+	summary: string;
+	evidence?: Record<string, unknown>;
+	blockedBy?: DispatchExplanation["blockedBy"];
+	gateVerdict?: GateResult;
+	trace?: UokDispatchEnvelope["trace"];
+}
+
+export function buildDispatchEnvelope(input: BuildDispatchEnvelopeInput): UokDispatchEnvelope {
+	return {
+		action: input.action,
+		nodeKind: input.node?.kind,
+		unitType: input.unitType,
+		unitId: input.unitId,
+		prompt: input.prompt,
+		reason: {
+			reasonCode: input.reasonCode,
+			summary: input.summary,
+			evidence: input.evidence,
+			blockedBy: input.blockedBy,
+		},
+		gateVerdict: input.gateVerdict,
+		constraints: input.node
+			? {
+					reads: input.node.reads,
+					writes: input.node.writes,
+					dependsOn: input.node.dependsOn,
+				}
+			: undefined,
+		trace: input.trace,
+	};
+}
+
+export function explainDispatch(envelope: UokDispatchEnvelope): string {
+	const subject =
+		envelope.unitType && envelope.unitId
+			? `${envelope.unitType} ${envelope.unitId}`
+			: envelope.nodeKind ?? envelope.action;
+	const blocked =
+		envelope.reason.blockedBy && envelope.reason.blockedBy.length > 0
+			? ` Blocked by: ${envelope.reason.blockedBy.map((b: { kind: string; id: string }) => `${b.kind}:${b.id}`).join(", ")}.`
+			: "";
+	return `[${envelope.reason.reasonCode}] ${subject}: ${envelope.reason.summary}.${blocked}`;
+}
diff --git a/src/resources/extensions/sf/uok/flags.ts b/src/resources/extensions/sf/uok/flags.ts
index c19def413..9ec90e73d 100644
--- a/src/resources/extensions/sf/uok/flags.ts
+++ b/src/resources/extensions/sf/uok/flags.ts
@@ -35,17 +35,18 @@ export function resolveUokFlags(prefs: SFPreferences | undefined): UokFlags {
 	return {
 		enabled: enabledByPreference && !legacyFallback,
 		legacyFallback,
-		gates: uok?.gates?.enabled === true,
-		modelPolicy: uok?.model_policy?.enabled === true,
-		executionGraph: uok?.execution_graph?.enabled === true,
-		gitops: uok?.gitops?.enabled === true,
+		gates: uok?.gates?.enabled ?? true,
+		modelPolicy: uok?.model_policy?.enabled ?? true,
+		executionGraph: uok?.execution_graph?.enabled ?? true,
+		gitops: uok?.gitops?.enabled ?? true,
 		gitopsTurnAction: uok?.gitops?.turn_action ?? "status-only",
 		gitopsTurnPush: uok?.gitops?.turn_push === true,
 		auditEnvelope:
-			uok?.audit_envelope?.enabled === true ||
-			uok?.audit_unified?.enabled === true,
+			(uok?.audit_envelope?.enabled ?? true) ||
+			(uok?.audit_unified?.enabled ?? true),
 		planningFlow:
-			uok?.planning_flow?.enabled === true || uok?.plan_v2?.enabled === true,
+			(uok?.planning_flow?.enabled ?? true) ||
+			(uok?.plan_v2?.enabled ?? true),
 	};
 }
 
diff --git a/src/resources/extensions/sf/uok/parity-report.ts b/src/resources/extensions/sf/uok/parity-report.ts
new file mode 100644
index 000000000..1131c4ea6
--- /dev/null
+++ b/src/resources/extensions/sf/uok/parity-report.ts
@@ -0,0 +1,87 @@
+import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+
+import { sfRoot } from "../paths.js";
+
+export interface UokParityEvent {
+	ts?: string;
+	path?: string;
+	phase?: string;
+	status?: string;
+	error?: string;
+	flags?: Record<string, unknown>;
+}
+
+export interface UokParityReport {
+	generatedAt: string;
+	sourcePath: string;
+	totalEvents: number;
+	paths: Record<string, number>;
+	statuses: Record<string, number>;
+	criticalMismatches: string[];
+	fallbackInvocations: number;
+}
+
+function parityLogPath(basePath: string): string {
+	return join(sfRoot(basePath), "runtime", "uok-parity.jsonl");
+}
+
+function reportPath(basePath: string): string {
+	return join(sfRoot(basePath), "runtime", "uok-parity-report.json");
+}
+
+function increment(bucket: Record<string, number>, key: string | undefined): void {
+	const normalized = key && key.trim().length > 0 ? key : "unknown";
+	bucket[normalized] = (bucket[normalized] ?? 0) + 1;
+}
+
+export function parseParityEvents(raw: string): UokParityEvent[] {
+	return raw
+		.split("\n")
+		.filter(Boolean)
+		.map((line) => {
+			try {
+				return JSON.parse(line) as UokParityEvent;
+			} catch {
+				return { status: "error", error: "invalid parity json line" };
+			}
+		});
+}
+
+export function buildParityReport(
+	events: readonly UokParityEvent[],
+	sourcePath: string,
+): UokParityReport {
+	const paths: Record<string, number> = {};
+	const statuses: Record<string, number> = {};
+	const criticalMismatches: string[] = [];
+	let fallbackInvocations = 0;
+
+	for (const event of events) {
+		increment(paths, event.path);
+		increment(statuses, event.status);
+		if (event.path === "legacy-fallback") fallbackInvocations += 1;
+		if (event.status === "error") {
+			criticalMismatches.push(event.error ?? "parity event reported error");
+		}
+	}
+
+	return {
+		generatedAt: new Date().toISOString(),
+		sourcePath,
+		totalEvents: events.length,
+		paths,
+		statuses,
+		criticalMismatches,
+		fallbackInvocations,
+	};
+}
+
+export function writeParityReport(basePath: string): UokParityReport {
+	const sourcePath = parityLogPath(basePath);
+	const raw = existsSync(sourcePath) ? readFileSync(sourcePath, "utf-8") : "";
+	const report = buildParityReport(parseParityEvents(raw), sourcePath);
+	mkdirSync(join(sfRoot(basePath), "runtime"), { recursive: true });
+	writeFileSync(reportPath(basePath), JSON.stringify(report, null, 2) + "\n", "utf-8");
+	return report;
+}
diff --git a/src/resources/extensions/sf/uok/writer.ts b/src/resources/extensions/sf/uok/writer.ts
new file mode 100644
index 000000000..75470a2ac
--- /dev/null
+++ b/src/resources/extensions/sf/uok/writer.ts
@@ -0,0 +1,114 @@
+import { existsSync, readFileSync } from "node:fs";
+import { join } from "node:path";
+import { randomUUID } from "node:crypto";
+
+import { atomicWriteSync } from "../atomic-write.js";
+import { sfRoot } from "../paths.js";
+import type { WriteRecord, WriterToken } from "./contracts.js";
+
+interface SequenceState {
+	lastSequence: number;
+	updatedAt: string;
+}
+
+const activeTokens = new Map<string, WriterToken>();
+
+function tokenKey(basePath: string, turnId: string): string {
+	return `${basePath}:${turnId}`;
+}
+
+function sequencePath(basePath: string): string {
+	return join(sfRoot(basePath), "runtime", "uok-writer-sequence.json");
+}
+
+function readSequenceState(basePath: string): SequenceState {
+	const path = sequencePath(basePath);
+	if (!existsSync(path)) {
+		return { lastSequence: 0, updatedAt: new Date(0).toISOString() };
+	}
+	try {
+		const parsed = JSON.parse(readFileSync(path, "utf-8")) as Partial<SequenceState>;
+		return {
+			lastSequence: Number.isInteger(parsed.lastSequence) ? Number(parsed.lastSequence) : 0,
+			updatedAt:
+				typeof parsed.updatedAt === "string" ? parsed.updatedAt : new Date(0).toISOString(),
+		};
+	} catch {
+		return { lastSequence: 0, updatedAt: new Date(0).toISOString() };
+	}
+}
+
+function writeSequenceState(basePath: string, state: SequenceState): void {
+	atomicWriteSync(sequencePath(basePath), JSON.stringify(state, null, 2) + "\n", "utf-8");
+}
+
+export function acquireWriterToken(args: {
+	basePath: string;
+	traceId: string;
+	turnId: string;
+	owner?: WriterToken["owner"];
+}): WriterToken {
+	const key = tokenKey(args.basePath, args.turnId);
+	const existing = activeTokens.get(key);
+	if (existing) {
+		throw new Error(`Writer token already active for turn ${args.turnId}`);
+	}
+
+	const token: WriterToken = {
+		tokenId: randomUUID(),
+		traceId: args.traceId,
+		turnId: args.turnId,
+		acquiredAt: new Date().toISOString(),
+		owner: args.owner ?? "uok",
+	};
+	activeTokens.set(key, token);
+	return token;
+}
+
+export function releaseWriterToken(basePath: string, token: WriterToken): void {
+	const key = tokenKey(basePath, token.turnId);
+	const current = activeTokens.get(key);
+	if (current?.tokenId === token.tokenId) {
+		activeTokens.delete(key);
+	}
+}
+
+export function hasActiveWriterToken(basePath: string, turnId: string): boolean {
+	return activeTokens.has(tokenKey(basePath, turnId));
+}
+
+export function nextWriteRecord(args: {
+	basePath: string;
+	token: WriterToken;
+	category: WriteRecord["category"];
+	operation: WriteRecord["operation"];
+	path?: string;
+	metadata?: Record<string, unknown>;
+}): WriteRecord {
+	if (!hasActiveWriterToken(args.basePath, args.token.turnId)) {
+		throw new Error(`Writer token is not active for turn ${args.token.turnId}`);
+	}
+
+	const state = readSequenceState(args.basePath);
+	const sequence = state.lastSequence + 1;
+	const updatedAt = new Date().toISOString();
+	writeSequenceState(args.basePath, { lastSequence: sequence, updatedAt });
+
+	return {
+		writerToken: args.token,
+		sequence: {
+			traceId: args.token.traceId,
+			turnId: args.token.turnId,
+			sequence,
+		},
+		category: args.category,
+		operation: args.operation,
+		path: args.path,
+		ts: updatedAt,
+		metadata: args.metadata,
+	};
+}
+
+export function resetWriterTokensForTests(): void {
+	activeTokens.clear();
+}
diff --git a/src/resources/extensions/sf/workflow-logger.ts b/src/resources/extensions/sf/workflow-logger.ts
index b45d59349..8e9cf6185 100644
--- a/src/resources/extensions/sf/workflow-logger.ts
+++ b/src/resources/extensions/sf/workflow-logger.ts
@@ -62,6 +62,7 @@ export type LogComponent =
 	| "registry" // Rule registry hook state
 	| "renderer" // Markdown renderer and projections
 	| "safety" // LLM safety harness
+	| "scaffold" // Scaffold versioning, manifest, and drift detection (ADR-021)
 	| "ecosystem"; // Third-party .sf/extensions/ plugins
 
 export interface LogEntry {