diff --git a/README.md b/README.md
index 8d78490..8c55394 100644
--- a/README.md
+++ b/README.md
@@ -126,9 +126,9 @@ registerCheck(def)            ← checks/*.ts self-register on load
         ├─ Q0 recon (shared, run once per run)   (src/recon.ts)
         │     git state + source-file inventory → .pygienium/recon.json
         ├─ analysis sub-agent  (buildScanTask)    ← scanner/<check> agent
-        │     writes pygienium/checks/<name>/findings.md
+        │     writes .pygienium/checks/<name>/findings.md
         ├─ fix sub-agent       (buildFixTask)     ← fixer, only with --fix
-        │     writes pygienium/checks/<name>/changes.md
+        │     writes .pygienium/checks/<name>/changes.md
         ├─ verify gate         (re-runs check.gate)
         └─ cleanup             (drops transient scratch artifacts)
 ```
diff --git a/src/checks/comments.ts b/src/checks/comments.ts
index 63c8fea..9a735f1 100644
--- a/src/checks/comments.ts
+++ b/src/checks/comments.ts
@@ -13,7 +13,7 @@
  *   - "why" comments that explain intent, rationale, or gotchas → KEEP
  *   - code self-explanatory with no comment → no comment needed (don't add one)
  *
- * Artifacts (under `<cwd>/pygienium/checks/comments/`):
+ * Artifacts (under `<cwd>/.pygienium/checks/comments/`):
  *   - `findings.md` — per-file line refs for each smell
  *   - `changes.md`  — summary of edits + human-review items
  *
@@ -28,14 +28,14 @@ export const COMMENTS_PHASE_ID = "C1";
 
 /**
  * Directory where this check writes its `findings.md` and `changes.md`
- * artifacts: `<cwd>/pygienium/checks/comments/`. Based on `scope.cwd` (the
+ * artifacts: `<cwd>/.pygienium/checks/comments/`. Based on `scope.cwd` (the
  * project root, always a directory) so the path is valid whether the scan
  * target is a single file or a directory. Matches the spec's
- * `pygienium/checks/comments/findings.md` relative-path notation.
+ * `.pygienium/checks/comments/findings.md` relative-path notation.
  */
 export function commentsArtifactDir(scope: CheckScope): string {
 	const base = scope.cwd.replace(/\/+$/, "");
-	return `${base}/pygienium/checks/comments`;
+	return `${base}/.pygienium/checks/comments`;
 }
 
 /** Absolute path to the findings artifact for this check. */
@@ -71,7 +71,7 @@ Short + high value is the goal. Evaluate every comment in the target:
 /**
  * Build the analysis sub-agent task. Instructs the agent to read candidate
  * source files, identify comment smells per the rubric, and write per-file line
- * references to `pygienium/comments/findings.md`.
+ * references to `.pygienium/comments/findings.md`.
  */
 export function buildCommentsScanTask(_cwd: string, scope: CheckScope): string {
 	const outDir = commentsArtifactDir(scope);
@@ -119,7 +119,7 @@ Write the report under \`${outDir}\` (create directories as needed).
 /**
  * Build the fix sub-agent task from the scan findings. Instructs the agent to
  * apply safe removals/tightenings, leave "why" comments, and write a summary
- * of edits plus anything needing human review to `pygienium/comments/changes.md`.
+ * of edits plus anything needing human review to `.pygienium/comments/changes.md`.
  */
 export function buildCommentsFixTask(
 	_cwd: string,
diff --git a/src/checks/complexity.ts b/src/checks/complexity.ts
index fb94908..16af1d7 100644
--- a/src/checks/complexity.ts
+++ b/src/checks/complexity.ts
@@ -28,11 +28,11 @@ import { scopeRulesMarkdown } from "./scope.js";
 export const COMPLEXITY_PHASE_ID = "C4";
 
 /**
- * Artifact directory: `<cwd>/pygienium/checks/complexity/`.
+ * Artifact directory: `<cwd>/.pygienium/checks/complexity/`.
  */
 export function complexityArtifactDir(scope: CheckScope): string {
 	const base = scope.cwd.replace(/\/+$/, "");
-	return `${base}/pygienium/checks/complexity`;
+	return `${base}/.pygienium/checks/complexity`;
 }
 
 /** Absolute path to findings artifact. */
@@ -84,13 +84,12 @@ count decision points (if/else if/for/while/case/&&/||/catch) per function.
  * Build the analysis sub-agent task. Instructs the agent to:
  * 1. Compute cyclomatic complexity per function
  * 2. Identify structural complexity smells
- * 3. Write findings to pygienium/checks/complexity/findings.md
+ * 3. Write findings to .pygienium/checks/complexity/findings.md
  */
 export function buildComplexityScanTask(
 	_cwd: string,
 	scope: CheckScope,
 ): string {
-	const outDir = complexityArtifactDir(scope);
 	const findingsFile = findingsPath(scope);
 	return `# Task: excessive complexity scan
 
@@ -173,7 +172,7 @@ Always create findings.md so the run has an artifact.
  * 1. Split 50+ complexity functions
  * 2. Refactor or justify 35–49 functions
  * 3. Apply safe refactors for structural smells
- * 4. Write changes summary to pygienium/checks/complexity/changes.md
+ * 4. Write changes summary to .pygienium/checks/complexity/changes.md
  */
 export function buildComplexityFixTask(
 	_cwd: string,
diff --git a/src/checks/dead-code.ts b/src/checks/dead-code.ts
index db24844..45f54bb 100644
--- a/src/checks/dead-code.ts
+++ b/src/checks/dead-code.ts
@@ -950,14 +950,14 @@ export async function applyDeadCodeFixes(
 // Artifact paths
 // ---------------------------------------------------------------------------
 
-const CHECK_DIRNAME = "pygienium/checks/dead-code";
+const CHECK_DIRNAME = ".pygienium/checks/dead-code";
 
-/** `<target>/pygienium/checks/dead-code/findings.md` */
+/** `<target>/.pygienium/checks/dead-code/findings.md` */
 export function findingsPath(target: string): string {
 	return join(target, CHECK_DIRNAME, "findings.md");
 }
 
-/** `<target>/pygienium/checks/dead-code/changes.md` */
+/** `<target>/.pygienium/checks/dead-code/changes.md` */
 export function changesPath(target: string): string {
 	return join(target, CHECK_DIRNAME, "changes.md");
 }
diff --git a/src/checks/deep-modules.ts b/src/checks/deep-modules.ts
index da40831..8271ebd 100644
--- a/src/checks/deep-modules.ts
+++ b/src/checks/deep-modules.ts
@@ -11,7 +11,7 @@
  *
  * Lifecycle:
  *   gate (need source files) → recon (shared) → scan sub-agent writes
- *   `<cwd>/pygienium/checks/deep-modules/findings.md` → [with --fix] fix
+ *   `<cwd>/.pygienium/checks/deep-modules/findings.md` → [with --fix] fix
  *   sub-agent writes `changes.md`, inlines safe pass-throughs, and lists
  *   risky consolidations (external importers / public API) for human review.
  *
@@ -32,7 +32,7 @@ import { isScopeSource, scopeRulesMarkdown } from "./scope.js";
 
 /** Output directory for this check's persistent reports. */
 export function deepModulesOutputDir(cwd: string): string {
-	return join(cwd, "pygienium", "checks", "deep-modules");
+	return join(cwd, ".pygienium", "checks", "deep-modules");
 }
 
 /** `findings.md` path for this check. */
diff --git a/src/checks/defensive-guards.ts b/src/checks/defensive-guards.ts
index ea63225..818ced2 100644
--- a/src/checks/defensive-guards.ts
+++ b/src/checks/defensive-guards.ts
@@ -30,7 +30,7 @@
  *
  * Lifecycle:
  *   gate (need source files) → recon (shared) → scan sub-agent writes
- *   `<cwd>/pygienium/checks/defensive-guards/findings.md` separating redundant
+ *   `<cwd>/.pygienium/checks/defensive-guards/findings.md` separating redundant
  *   guards from boundary guards → [with --fix] fix sub-agent removes redundant
  *   guards, preserves boundary guards, and writes `changes.md` distinguishing
  *   removed vs kept-with-reason.
@@ -52,7 +52,7 @@ import { isScopeSource, scopeRulesMarkdown } from "./scope.js";
 
 /** Output directory for this check's persistent reports. */
 export function defensiveGuardsOutputDir(cwd: string): string {
-	return join(cwd, "pygienium", "checks", "defensive-guards");
+	return join(cwd, ".pygienium", "checks", "defensive-guards");
 }
 
 /** `findings.md` path for this check. */
diff --git a/src/commands.ts b/src/commands.ts
index d2c494d..3db4aa6 100644
--- a/src/commands.ts
+++ b/src/commands.ts
@@ -60,12 +60,24 @@ function resolveCwd(args: string, ctxCwd: string): string {
 	return resolve(ctxCwd, tok);
 }
 
-/** Strip a leading flag token (`--fix`) from args, returning the remainder. */
-function splitFlags(args: string): { fix: boolean; rest: string } {
+/**
+ * Strip leading flag tokens (`--fix`, `--fresh`, `--no-gitignore`) from args,
+ * returning the remainder (the positional `[path]`).
+ */
+function splitFlags(args: string): {
+	fix: boolean;
+	fresh: boolean;
+	rest: string;
+	noGitignore: boolean;
+} {
 	const tokens = args.trim().length > 0 ? args.trim().split(/\s+/) : [];
 	const fix = tokens.includes("--fix");
-	const rest = tokens.filter((t) => t !== "--fix").join(" ");
-	return { fix, rest };
+	const fresh = tokens.includes("--fresh");
+	const noGitignore = tokens.includes("--no-gitignore");
+	const rest = tokens
+		.filter((t) => t !== "--fix" && t !== "--fresh" && t !== "--no-gitignore")
+		.join(" ");
+	return { fix, fresh, rest, noGitignore };
 }
 
 /**
@@ -76,12 +88,13 @@ function splitFlags(args: string): { fix: boolean; rest: string } {
 function parseResumeArgs(
 	args: string,
 	ctxCwd: string,
-): { cwd: string; fresh: boolean } {
+): { cwd: string; fresh: boolean; gitignore: boolean } {
 	const tokens = args.trim().length > 0 ? args.trim().split(/\s+/) : [];
 	const fresh = tokens.includes("--fresh");
+	const gitignore = !tokens.includes("--no-gitignore");
 	const positional = tokens.find((t) => !t.startsWith("--"));
 	const cwd = positional ? resolve(ctxCwd, positional) : ctxCwd;
-	return { cwd, fresh };
+	return { cwd, fresh, gitignore };
 }
 
 /** `/pygienium-help` */
@@ -116,9 +129,12 @@ export async function handleCheckCommand(
 		hasUI: ctx.hasUI,
 	});
 
+	const giNote = outcome.gitignoreAppended
+		? " · .pygienium/ added to .gitignore"
+		: "";
 	print(
 		ctx,
-		`pygienium ${check.label}: ${outcome.status}${outcome.error ? ` — ${outcome.error}` : ""}`,
+		`pygienium ${check.label}: ${outcome.status}${outcome.error ? ` — ${outcome.error}` : ""}${giNote}`,
 	);
 }
 
@@ -142,13 +158,17 @@ export async function handleAllCommand(
 		target: parsed.target,
 		fix: parsed.fix,
 		fresh: parsed.fresh,
+		gitignore: parsed.gitignore,
 		only: parsed.only,
 		ui: ctx.ui,
 		hasUI: ctx.hasUI,
 	});
+	const giNote = outcome.gitignoreAppended
+		? " · .pygienium/ added to .gitignore"
+		: "";
 	print(
 		ctx,
-		`pygienium: all-run ${outcome.status} — ${outcome.ran.length} ran, ${outcome.skipped.length} skipped; summary → ${allSummaryPath(ctx.cwd)} (${runStatePath(ctx.cwd)})`,
+		`pygienium: all-run ${outcome.status} — ${outcome.ran.length} ran, ${outcome.skipped.length} skipped; summary → ${allSummaryPath(ctx.cwd)} (${runStatePath(ctx.cwd)})${giNote}`,
 	);
 }
 
@@ -178,7 +198,7 @@ export async function handleResumeCommand(
 	args: string,
 	ctx: PygieniumCtx,
 ): Promise<void> {
-	const { cwd, fresh } = parseResumeArgs(args, ctx.cwd);
+	const { cwd, fresh, gitignore } = parseResumeArgs(args, ctx.cwd);
 	let state = await loadRunState(cwd);
 	if (!state) {
 		print(ctx, "pygienium: no run state to resume.");
@@ -202,6 +222,7 @@ export async function handleResumeCommand(
 	// unless --fresh.
 	let ran = 0;
 	let skipped = 0;
+	let giAppended = false;
 	for (const entry of Object.values(state.checks)) {
 		const def = getCheck(entry.name);
 		if (!def) {
@@ -258,7 +279,7 @@ export async function handleExportCommand(
 	if (result.entries.length === 0) {
 		print(
 			ctx,
-			`pygienium: nothing to export (no findings.md/changes.md under ${cwd}/pygienium/checks/).`,
+			`pygienium: nothing to export (no findings.md/changes.md under ${cwd}/.pygienium/checks/).`,
 		);
 		return;
 	}
diff --git a/src/export.ts b/src/export.ts
index 3f8e8b5..eed4954 100644
--- a/src/export.ts
+++ b/src/export.ts
@@ -3,9 +3,9 @@
  *
  * `/pygienium-export` walks each check's artifact directory (where
  * `findings.md` and `changes.md` live), applies `--check=` / `--status=`
- * filters, and writes a single bundle to `pygienium/export.{md|json}`.
+ * filters, and writes a single bundle to `.pygienium/export.{md|json}`.
  *
- * Artifact root: `<cwd>/pygienium/checks/<name>/` — the single canonical
+ * Artifact root: `<cwd>/.pygienium/checks/<name>/` — the single canonical
  * location every shipped check writes to.
  *
  * Statuses for `--status=` filtering come from the run-state; a check dir
@@ -21,23 +21,23 @@ import type { RunState } from "./run-state.js";
 export type ExportFormat = "md" | "json";
 
 /** Directory name (relative to cwd) that holds `checks/` and `export.md`. */
-export const PYGIENIUM_ARTIFACT_DIR = "pygienium";
+export const PYGIENIUM_ARTIFACT_DIR = ".pygienium";
 /** Subdirectory holding per-check `findings.md`/`changes.md`. */
 export const CHECKS_SUBDIR = "checks";
 /** Base filename for the bundle (`export.md` / `export.json`). */
 export const EXPORT_FILENAME_BASE = "export";
 
-/** Resolve `<cwd>/pygienium/` (the artifact root). */
+/** Resolve `<cwd>/.pygienium/` (the artifact root). */
 export function pygieniumArtifactDir(cwd: string): string {
 	return join(cwd, PYGIENIUM_ARTIFACT_DIR);
 }
 
-/** Resolve `<cwd>/pygienium/checks/`. */
+/** Resolve `<cwd>/.pygienium/checks/`. */
 export function canonicalChecksRoot(cwd: string): string {
 	return join(pygieniumArtifactDir(cwd), CHECKS_SUBDIR);
 }
 
-/** Resolve `<cwd>/pygienium/export.<format>`. */
+/** Resolve `<cwd>/.pygienium/export.<format>`. */
 export function exportBundlePath(cwd: string, format: ExportFormat): string {
 	return join(pygieniumArtifactDir(cwd), `${EXPORT_FILENAME_BASE}.${format}`);
 }
@@ -153,7 +153,7 @@ async function gatherFromRoot(
 }
 
 /**
- * Gather artifact entries from the canonical `<cwd>/pygienium/checks/` root,
+ * Gather artifact entries from the canonical `<cwd>/.pygienium/checks/` root,
  * one entry per check directory. Entries are sorted alphabetically. Marks an
  * entry `unknown` when its check is absent from `state`.
  */
diff --git a/src/help.ts b/src/help.ts
index d8dcb2b..41541f4 100644
--- a/src/help.ts
+++ b/src/help.ts
@@ -62,6 +62,12 @@ export const CLI_FLAGS: HelpFlag[] = [
 		scope: "all",
 		description: "Comma-separated check names to run (subset of the registry).",
 	},
+	{
+		name: "--no-gitignore",
+		scope: "<check>, all, resume",
+		description:
+			"Don't add `.pygienium/` to the target repo's .gitignore (added by default so runs never stage their own output).",
+	},
 	{
 		name: "--check=",
 		scope: "export",
@@ -118,7 +124,7 @@ export const COMMANDS: HelpCommand[] = [
 	{
 		usage: "pygienium-export [path] [--check=] [--status=] [--out=md|json]",
 		description:
-			"Bundle every check's findings.md + changes.md into pygienium/export.{md|json}.",
+			"Bundle every check's findings.md + changes.md into .pygienium/export.{md|json}.",
 		example: "/pygienium-export --out=json",
 	},
 ];
diff --git a/src/modes/all.ts b/src/modes/all.ts
index 0e4f74a..9e28855 100644
--- a/src/modes/all.ts
+++ b/src/modes/all.ts
@@ -10,7 +10,7 @@
  *   init single run (mode "all") → run shared recon once →
  *   for each registered check (in registry order): call `runCheck` with the
  *   SHARED run-state record (not a fresh one per check) → reconcile run
- *   status → write `pygienium/all-summary.md`.
+ *   status → write `.pygienium/all-summary.md`.
  *
  * Resumability: terminal checks (`complete`/`skipped`) are skipped on resume;
  * `in_progress`/`failed`/`pending` checks re-run. `--fresh` resets every check
@@ -29,6 +29,7 @@ import { createPhaseStrip } from "../phases.js";
 import { runRecon } from "../recon.js";
 import {
 	applyPhaseStatus,
+	ensureRunStateIgnored,
 	initRunState,
 	loadRunState,
 	markRunStatus,
@@ -42,11 +43,11 @@ import {
 } from "../run-state.js";
 
 /** Artifact directory name (relative to cwd) that holds `all-summary.md`. */
-export const ALL_ARTIFACT_DIR = "pygienium";
+export const ALL_ARTIFACT_DIR = ".pygienium";
 /** Filename for the unified per-check summary report. */
 export const ALL_SUMMARY_FILENAME = "all-summary.md";
 
-/** Resolve `<cwd>/pygienium/all-summary.md`. */
+/** Resolve `<cwd>/.pygienium/all-summary.md`. */
 export function allSummaryPath(cwd: string): string {
 	return join(cwd, ALL_ARTIFACT_DIR, ALL_SUMMARY_FILENAME);
 }
@@ -62,10 +63,17 @@ export interface AllRunOptions {
 	only?: string[];
 	/** Reset and re-run every check, ignoring prior terminal state (`--fresh`). */
 	fresh?: boolean;
+	/**
+	 * Ensure `<cwd>/.gitignore` excludes `.pygienium/` before this run writes
+	 * state/artifacts (default true). Set false with `--no-gitignore`.
+	 */
+	gitignore?: boolean;
 	/** UI context (optional; null in print mode). */
 	ui?: ExtensionUIContext;
 	/** Whether dialog-capable UI is available. */
 	hasUI?: boolean;
+	/** Optional callback to post completion messages into the chat. */
+	sendChatMessage?: SendChatMessage;
 }
 
 /** Outcome of {@link runAllChecks}. */
@@ -80,6 +88,8 @@ export interface AllRunOutcome {
 	ran: string[];
 	/** Checks skipped because they were already terminal. */
 	skipped: string[];
+	/** True when this run appended `.pygienium/` to the repo's .gitignore. */
+	gitignoreAppended?: boolean;
 }
 
 /**
@@ -104,11 +114,13 @@ export function parseAllArgs(
 	target: string;
 	fix: boolean;
 	fresh: boolean;
+	gitignore: boolean;
 	only: string[];
 } {
 	const tokens = args.trim().length > 0 ? args.trim().split(/\s+/) : [];
 	let fix = false;
 	let fresh = false;
+	let gitignore = true;
 	let target = cwd;
 	const only: string[] = [];
 	for (const tok of tokens) {
@@ -116,6 +128,8 @@ export function parseAllArgs(
 			fix = true;
 		} else if (tok === "--fresh") {
 			fresh = true;
+		} else if (tok === "--no-gitignore") {
+			gitignore = false;
 		} else if (tok.startsWith("--only=")) {
 			for (const name of tok.slice("--only=".length).split(",")) {
 				const trimmed = name.trim();
@@ -125,7 +139,7 @@ export function parseAllArgs(
 			target = tok;
 		}
 	}
-	return { target: resolve(cwd, target), fix, fresh, only };
+	return { target: resolve(cwd, target), fix, fresh, gitignore, only };
 }
 
 /** Count non-empty lines in captured findings/changes text. */
@@ -219,6 +233,11 @@ export async function runAllChecks(
 	const fresh = opts.fresh ?? false;
 	const hasUI = opts.hasUI ?? false;
 
+	// Keep pygienium's own output out of the scanned repo's git index unless
+	// the caller opted out with --no-gitignore.
+	const gitignoreAppended =
+		opts.gitignore === false ? false : await ensureRunStateIgnored(cwd);
+
 	const selected = selectChecks(opts.only);
 	if (selected.length === 0) {
 		// `--only` selected nothing (or no checks registered). Still produce a
@@ -227,7 +246,14 @@ export async function runAllChecks(
 		markRunStatus(state, reconcileRunStatus(state));
 		await saveRunState(state);
 		const summaryPath = await writeAllSummary(state, []);
-		return { status: state.status, state, summaryPath, ran: [], skipped: [] };
+		return {
+			status: state.status,
+			state,
+			summaryPath,
+			ran: [],
+			skipped: [],
+			gitignoreAppended,
+		};
 	}
 
 	// --- Init / resume the single shared run-state --------------------------
@@ -312,6 +338,7 @@ export async function runAllChecks(
 			ui: opts.ui,
 			hasUI,
 			existingState: state,
+			gitignore: opts.gitignore,
 		});
 		state = outcome.state;
 		ran.push(check.name);
diff --git a/src/modes/check-runner.ts b/src/modes/check-runner.ts
index 56b9388..9424cfa 100644
--- a/src/modes/check-runner.ts
+++ b/src/modes/check-runner.ts
@@ -82,12 +82,14 @@ export interface RunCheckOptions {
 	hasUI?: boolean;
 	/** Pre-existing run state to update (for `/pygienium-all` and resume). */
 	existingState?: RunState;
+	gitignore?: boolean;
 }
 
 /** Outcome of a single check run. */
 export interface CheckRunOutcome {
 	/** Final check status. */
 	status: "complete" | "failed" | "skipped";
+	gitignoreAppended?: boolean;
 	/** Findings text from the analysis phase. */
 	findings?: string;
 	/** Changes text from the fix phase (when run with --fix). */
diff --git a/src/run-state.ts b/src/run-state.ts
index fbb5a2f..65c34cb 100644
--- a/src/run-state.ts
+++ b/src/run-state.ts
@@ -9,8 +9,8 @@
  * @module pygienium/run-state
  */
 
-import { mkdir, readFile, writeFile } from "node:fs/promises";
-import { dirname, join } from "node:path";
+import { appendFile, mkdir, readFile, stat, writeFile } from "node:fs/promises";
+import { join } from "node:path";
 
 export const RUN_STATE_DIRNAME = ".pygienium";
 export const RUN_STATE_FILENAME = "run-state.json";
@@ -152,6 +152,46 @@ export async function saveRunState(state: RunState): Promise<void> {
 	);
 }
 
+/**
+ * Memo of cwds whose `.gitignore` was already ensured this process, so the
+ * check runs at most once per target per session.
+ */
+const gitIgnoreMemo = new Set<string>();
+
+/**
+ * Make sure `<cwd>/.gitignore` excludes `.pygienium/` (run-state + artifacts)
+ * so a run never stages its own output into the scanned repo's git index.
+ * Best-effort and idempotent: no-op outside a git work tree or when the entry
+ * already exists. Returns true when it appended the entry (or created the file).
+ */
+export async function ensureRunStateIgnored(cwd: string): Promise<boolean> {
+	if (gitIgnoreMemo.has(cwd)) return false;
+	gitIgnoreMemo.add(cwd);
+	try {
+		// Only act inside a git work tree (works for worktrees too: .git is a file).
+		await stat(join(cwd, ".git"));
+		const ignorePath = join(cwd, ".gitignore");
+		const marker = ".pygienium/";
+		let content: string;
+		try {
+			content = await readFile(ignorePath, "utf8");
+		} catch {
+			await writeFile(ignorePath, `${marker}\n`, "utf8");
+			return true;
+		}
+		if (content.split(/\r?\n/).some((l) => l.trim() === marker)) return false;
+		const prefix = content.endsWith("\n") ? "" : "\n";
+		await appendFile(
+			ignorePath,
+			`${prefix}# pygienium run-state and check artifacts\n${marker}\n`,
+			"utf8",
+		);
+		return true;
+	} catch {
+		return false; // not a git work tree, or a best-effort write failed
+	}
+}
+
 /** Mark a phase's status (and optionally an error message). */
 export function applyPhaseStatus(
 	state: RunState,
diff --git a/tests/all-integration.test.ts b/tests/all-integration.test.ts
index 5d1abce..e54999d 100644
--- a/tests/all-integration.test.ts
+++ b/tests/all-integration.test.ts
@@ -35,9 +35,9 @@ function fakeCheck(name: string): CheckDefinition {
 		fixAgentName: "fixer",
 		phaseId: "scan",
 		buildScanTask: (_cwd, scope) =>
-			`!write pygienium/checks/${name}/findings.md # ${name} findings\nscan-target:${scope.target}\n!echo ${name}-scan`,
+			`!write .pygienium/checks/${name}/findings.md # ${name} findings\nscan-target:${scope.target}\n!echo ${name}-scan`,
 		buildFixTask: (_cwd, _scope, findings) =>
-			`!write pygienium/checks/${name}/changes.md # ${name} changes\nbased-on:${findings.split("\n")[0] ?? ""}\n!echo ${name}-fix`,
+			`!write .pygienium/checks/${name}/changes.md # ${name} changes\nbased-on:${findings.split("\n")[0] ?? ""}\n!echo ${name}-fix`,
 		gate: () => undefined,
 	};
 }
diff --git a/tests/all.test.ts b/tests/all.test.ts
index 8879849..3eb5ebe 100644
--- a/tests/all.test.ts
+++ b/tests/all.test.ts
@@ -4,7 +4,7 @@
  * Mirrors the spec scenario: run `/pygienium-all` on a small repo and assert:
  *   - every registered check runs exactly once in registry order;
  *   - run-state shows all checks complete and the overall run complete;
- *   - `pygienium/all-summary.md` is present and lists per-check outcomes;
+ *   - `.pygienium/all-summary.md` is present and lists per-check outcomes;
  *   - `--only=alpha,gamma` narrows the candidate set preserving order;
  *   - interrupted/resumed runs re-dispatch non-terminal checks while skipping
  *     terminal ones, unless `--fresh` resets everything.
@@ -57,9 +57,9 @@ function fakeCheck(name: string): CheckDefinition {
 		fixAgentName: "fixer",
 		phaseId: "scan",
 		buildScanTask: (_cwd, scope) =>
-			`!write pygienium/checks/${name}/findings.md # ${name} findings\nscan-target:${scope.target}\n!echo ${name}-scan`,
+			`!write .pygienium/checks/${name}/findings.md # ${name} findings\nscan-target:${scope.target}\n!echo ${name}-scan`,
 		buildFixTask: (_cwd, _scope, findings) =>
-			`!write pygienium/checks/${name}/changes.md # ${name} changes\nbased-on:${findings.split("\n")[0] ?? ""}\n!echo ${name}-fix`,
+			`!write .pygienium/checks/${name}/changes.md # ${name} changes\nbased-on:${findings.split("\n")[0] ?? ""}\n!echo ${name}-fix`,
 		gate: () => undefined,
 	};
 }
@@ -132,12 +132,16 @@ describe("/pygienium-all orchestrator (task 12)", () => {
 		await rm(cwd, { recursive: true, force: true });
 	});
 
-	it("parseAllArgs parses path, --fix, --fresh, and --only", () => {
+	it("parseAllArgs parses path, --fix, --fresh, --no-gitignore, and --only", () => {
 		const p = parseAllArgs("subdir --fix --only=alpha,beta --fresh", cwd);
 		expect(p.target).toBe(join(cwd, "subdir"));
 		expect(p.fix).toBe(true);
 		expect(p.fresh).toBe(true);
+		expect(p.gitignore).toBe(true); // default: keep the .gitignore guard on
 		expect(p.only).toEqual(["alpha", "beta"]);
+		const noGi = parseAllArgs("--no-gitignore", cwd);
+		expect(noGi.gitignore).toBe(false);
+		expect(noGi.target).toBe(cwd);
 	});
 
 	it("selectChecks preserves registry order for the --only subset", () => {
@@ -176,7 +180,7 @@ describe("/pygienium-all orchestrator (task 12)", () => {
 		expect(state?.recon.complete).toBe(true);
 	});
 
-	it("writes pygienium/all-summary.md listing per-check outcomes", async () => {
+	it("writes .pygienium/all-summary.md listing per-check outcomes", async () => {
 		registerCheck(fakeCheck("alpha"));
 		registerCheck(fakeCheck("beta"));
 
@@ -193,7 +197,7 @@ describe("/pygienium-all orchestrator (task 12)", () => {
 		expect(summary).toContain("changes:");
 		// Artifacts actually exist on disk.
 		const alphaFindings = await readFile(
-			join(cwd, "pygienium", "checks", "alpha", "findings.md"),
+			join(cwd, ".pygienium", "checks", "alpha", "findings.md"),
 			"utf8",
 		);
 		expect(alphaFindings).toContain("alpha findings");
@@ -233,7 +237,7 @@ describe("/pygienium-all orchestrator (task 12)", () => {
 		await captureStdout(() => handleAllCommand("--fix", stubCtx(cwd)));
 		expect(track.dispatched.length).toBe(4); // 2 checks × 2 phases
 		const firstAlphaFix = await readFile(
-			join(cwd, "pygienium", "checks", "alpha", "changes.md"),
+			join(cwd, ".pygienium", "checks", "alpha", "changes.md"),
 			"utf8",
 		);
 
@@ -255,7 +259,7 @@ describe("/pygienium-all orchestrator (task 12)", () => {
 		expect(state3?.status).toBe("complete");
 		// The fresh re-run overwrote alpha's changes.md (still valid content).
 		const alphaFix2 = await readFile(
-			join(cwd, "pygienium", "checks", "alpha", "changes.md"),
+			join(cwd, ".pygienium", "checks", "alpha", "changes.md"),
 			"utf8",
 		);
 		expect(alphaFix2).toContain("alpha changes");
@@ -278,7 +282,7 @@ describe("/pygienium-all orchestrator (task 12)", () => {
 			finishedAt: Date.now(),
 		};
 		// Pre-create alpha's on-disk artifacts so its completed entry has artifacts.
-		const alphaDir = join(cwd, "pygienium", "checks", "alpha");
+		const alphaDir = join(cwd, ".pygienium", "checks", "alpha");
 		await mkdir(alphaDir, { recursive: true });
 		await writeFile(
 			join(alphaDir, "findings.md"),
diff --git a/tests/deep-modules.test.ts b/tests/deep-modules.test.ts
index 2a54131..ae34688 100644
--- a/tests/deep-modules.test.ts
+++ b/tests/deep-modules.test.ts
@@ -145,15 +145,15 @@ describe("deep-modules check", () => {
 		expect(state?.checks["deep-modules"]?.status).toBe("complete");
 	});
 
-	it("findings.md and changes.md live under pygienium/checks/deep-modules/", async () => {
+	it("findings.md and changes.md live under .pygienium/checks/deep-modules/", async () => {
 		await seedPassThrough(cwd);
 		const check = getCheck("deep-modules")!;
 		await handleCheckCommand(check, "--fix", stubCtx(cwd));
 		expect(findingsPath(cwd)).toBe(
-			join(cwd, "pygienium", "checks", "deep-modules", "findings.md"),
+			join(cwd, ".pygienium", "checks", "deep-modules", "findings.md"),
 		);
 		expect(changesPath(cwd)).toBe(
-			join(cwd, "pygienium", "checks", "deep-modules", "changes.md"),
+			join(cwd, ".pygienium", "checks", "deep-modules", "changes.md"),
 		);
 	});
 
diff --git a/tests/defensive-guards.test.ts b/tests/defensive-guards.test.ts
index 7fa54d6..f8b2529 100644
--- a/tests/defensive-guards.test.ts
+++ b/tests/defensive-guards.test.ts
@@ -208,16 +208,16 @@ describe("defensive-guards check", () => {
 		expect(state?.checks["defensive-guards"]?.status).toBe("complete");
 	});
 
-	it("findings.md and changes.md live under pygienium/checks/defensive-guards/", async () => {
+	it("findings.md and changes.md live under .pygienium/checks/defensive-guards/", async () => {
 		await seedNoise(cwd);
 		await seedBoundary(cwd);
 		const check = getCheck("defensive-guards")!;
 		await handleCheckCommand(check, "--fix", stubCtx(cwd));
 		expect(findingsPath(cwd)).toBe(
-			join(cwd, "pygienium", "checks", "defensive-guards", "findings.md"),
+			join(cwd, ".pygienium", "checks", "defensive-guards", "findings.md"),
 		);
 		expect(changesPath(cwd)).toBe(
-			join(cwd, "pygienium", "checks", "defensive-guards", "changes.md"),
+			join(cwd, ".pygienium", "checks", "defensive-guards", "changes.md"),
 		);
 	});
 
diff --git a/tests/status-resume-export.test.ts b/tests/status-resume-export.test.ts
index 763d00d..0eff4bd 100644
--- a/tests/status-resume-export.test.ts
+++ b/tests/status-resume-export.test.ts
@@ -71,9 +71,9 @@ function fakeCheck(name: string): CheckDefinition {
 		fixAgentName: "fixer",
 		phaseId: "scan",
 		buildScanTask: (_cwd, scope) =>
-			`!write pygienium/checks/${name}/findings.md # ${name} findings\nscan-target:${scope.target}\n!echo ${name}-scan`,
+			`!write .pygienium/checks/${name}/findings.md # ${name} findings\nscan-target:${scope.target}\n!echo ${name}-scan`,
 		buildFixTask: (_cwd, _scope, findings) =>
-			`!write pygienium/checks/${name}/changes.md # ${name} changes\nbased-on:${findings.split("\n")[0] ?? ""}\n!echo ${name}-fix`,
+			`!write .pygienium/checks/${name}/changes.md # ${name} changes\nbased-on:${findings.split("\n")[0] ?? ""}\n!echo ${name}-fix`,
 		gate: () => undefined,
 	};
 }
@@ -86,7 +86,7 @@ function stubCtx(cwd: string): PygieniumCtx {
 function trackingRunner(): { runner: AgentRunner; dispatched: string[] } {
 	const dispatched: string[] = [];
 	const runner: AgentRunner = async (opts) => {
-		// Tag by check name from the task text (`!write pygienium/checks/<name>/`).
+		// Tag by check name from the task text (`!write .pygienium/checks/<name>/`).
 		const m = /pygienium\/checks\/([^/]+)\//.exec(opts.task);
 		if (m) dispatched.push(m[1] as string);
 		return fakeAgentRunner(opts);
@@ -297,7 +297,7 @@ describe("status / resume / export (task 13)", () => {
 		void state;
 
 		await captureStdout(() => handleExportCommand("", stubCtx(cwd)));
-		const bundle = await readFile(join(cwd, "pygienium", "export.md"), "utf8");
+		const bundle = await readFile(join(cwd, ".pygienium", "export.md"), "utf8");
 		expect(bundle).toContain("# Pygienium export");
 		expect(bundle).toContain("## alpha (complete)");
 		expect(bundle).toContain("## beta (complete)");
@@ -314,7 +314,7 @@ describe("status / resume / export (task 13)", () => {
 		await captureStdout(() =>
 			handleExportCommand("--check=beta", stubCtx(cwd)),
 		);
-		const bundle = await readFile(join(cwd, "pygienium", "export.md"), "utf8");
+		const bundle = await readFile(join(cwd, ".pygienium", "export.md"), "utf8");
 		expect(bundle).toContain("## beta (complete)");
 		expect(bundle).not.toContain("## alpha");
 	});
@@ -330,7 +330,7 @@ describe("status / resume / export (task 13)", () => {
 		await captureStdout(() =>
 			handleExportCommand("--status=failed", stubCtx(cwd)),
 		);
-		const bundle = await readFile(join(cwd, "pygienium", "export.md"), "utf8");
+		const bundle = await readFile(join(cwd, ".pygienium", "export.md"), "utf8");
 		expect(bundle).toContain("## alpha (failed)");
 		expect(bundle).not.toContain("## beta");
 	});
@@ -345,7 +345,7 @@ describe("status / resume / export (task 13)", () => {
 			handleExportCommand("--out=json", stubCtx(cwd)),
 		);
 		expect(out.join("\n")).toContain("export.json");
-		const raw = await readFile(join(cwd, "pygienium", "export.json"), "utf8");
+		const raw = await readFile(join(cwd, ".pygienium", "export.json"), "utf8");
 		const parsed = JSON.parse(raw) as {
 			checks: Array<{ name: string; status: string; findings: string }>;
 		};
@@ -370,20 +370,22 @@ describe("status / resume / export (task 13)", () => {
 		expect(f.out).toBe("json");
 	});
 
-	it("gatherExportEntries reads only the canonical pygienium/checks/ root", async () => {
-		await mkdir(join(cwd, "pygienium", "checks", "alpha"), { recursive: true });
-		await writeFile(
-			join(cwd, "pygienium", "checks", "alpha", "findings.md"),
-			"# alpha findings\n",
-			"utf8",
-		);
-		// A stray .pygienium/checks/ dir (the removed legacy root) is ignored now
-		// that all checks write to the single canonical `pygienium/checks/` root.
-		await mkdir(join(cwd, ".pygienium", "checks", "ghost"), {
+	it("gatherExportEntries reads only the canonical .pygienium/checks/ root", async () => {
+		await mkdir(join(cwd, ".pygienium", "checks", "alpha"), {
 			recursive: true,
 		});
 		await writeFile(
-			join(cwd, ".pygienium", "checks", "ghost", "findings.md"),
+			join(cwd, ".pygienium", "checks", "alpha", "findings.md"),
+			"# alpha findings\n",
+			"utf8",
+		);
+		// A stray pygienium/checks/ dir (the old non-hidden root) is ignored now
+		// that all checks write to the single canonical `.pygienium/checks/` root.
+		await mkdir(join(cwd, "pygienium", "checks", "ghost"), {
+			recursive: true,
+		});
+		await writeFile(
+			join(cwd, "pygienium", "checks", "ghost", "findings.md"),
 			"# ghost findings\n",
 			"utf8",
 		);
@@ -393,7 +395,7 @@ describe("status / resume / export (task 13)", () => {
 		expect(alpha?.findings).toContain("alpha findings");
 		expect(alpha?.status).toBe("unknown");
 		expect(alpha?.findingsPath).toBe(
-			join(cwd, "pygienium", "checks", "alpha", "findings.md"),
+			join(cwd, ".pygienium", "checks", "alpha", "findings.md"),
 		);
 		expect(entries.find((e) => e.name === "ghost")).toBeUndefined();
 	});
@@ -415,6 +417,6 @@ describe("status / resume / export (task 13)", () => {
 	it("exportRun writes nothing useful and reports zero entries cleanly", async () => {
 		const result = await exportRun(cwd, undefined, {});
 		expect(result.entries).toHaveLength(0);
-		expect(relative(cwd, result.path)).toBe(join("pygienium", "export.md"));
+		expect(relative(cwd, result.path)).toBe(join(".pygienium", "export.md"));
 	});
 });