feat(catalog): added supportsHashlineEdits helper and exclude step-3.7-flash models

- Added supportsHashlineEdits catalog function and Step 3.7 Flash SKU recognition.
- Updated coding agent edit resolution to utilize the centralized catalog function.
- Updated write snapshot generation to record empty seen-line provenance.

packages/catalog/src/identity/family.ts

@@ -119,6 +119,11 @@ export const isMimoModelIdOrName = memo((value: string): boolean => {
 	return value.toLowerCase().includes("mimo");
 });
 
+/** StepFun Step 3.7 Flash SKU in any namespace form (`kilo/stepfun/step-3.7-flash:free`). */
+export const isStep37FlashModelId = memo((modelId: string): boolean => {
+	return modelId.toLowerCase().includes("step-3.7-flash");
+});
+
 /** Gemini family ids in any namespace form (`gemini-*`, `google/gemini-*`, `openrouter/google/gemini-…`). */
 export const isGeminiModelId = memo((modelId: string): boolean => {
 	return /(^|\/)gemini[-.]?/i.test(modelId);
@@ -399,6 +404,22 @@ export const supportsMidConversationSystemMessages = memo((modelId: string): boo
 	return parsed !== null && isAnthropicAdaptiveGenAtLeast(parsed, "4.8");
 });
 
+/**
+ * Models that reliably follow the hashline line-anchored edit dialect
+ * (`[path#TAG]` headers plus 1-indexed anchors). Kimi, MiMo, DeepSeek V4
+ * Flash, and Step 3.7 Flash miscount anchors or drop the tag header often
+ * enough that hosts fall back to a literal search-replace edit format for
+ * them.
+ */
+export const supportsHashlineEdits = memo((modelId: string): boolean => {
+	return !(
+		isKimiModelId(modelId) ||
+		isMimoModelIdOrName(modelId) ||
+		isDeepseekV4FlashModelId(modelId) ||
+		isStep37FlashModelId(modelId)
+	);
+});
+
 export const isAnthropicFableOrMythosModel = memo((modelId: string): boolean => {
 	const parsed = parseAnthropicModel(bareModelId(modelId));
 	return parsed !== null && isFableOrMythos(parsed.kind);

packages/catalog/test/identity-family.test.ts

@@ -19,6 +19,7 @@ import {
 	modelFamilyToken,
 	parseAnthropicModel,
 	supportsAdaptiveThinkingDisplay,
+	supportsHashlineEdits,
 	supportsMidConversationSystemMessages,
 } from "@oh-my-pi/pi-catalog/identity";
 
@@ -31,6 +32,20 @@ describe("isKimiModelId", () => {
 	});
 });
 
+describe("supportsHashlineEdits", () => {
+	test("declines the families that miscount line anchors", () => {
+		expect(supportsHashlineEdits("openrouter/moonshotai/Kimi-K2-Instruct")).toBe(false);
+		expect(supportsHashlineEdits("xiaomi/MiMo-V2.5-Pro")).toBe(false);
+		expect(supportsHashlineEdits("tensormesh/deepseek-ai/DeepSeek-V4-Flash")).toBe(false);
+		expect(supportsHashlineEdits("kilo/stepfun/step-3.7-flash:free")).toBe(false);
+	});
+	test("vouches for structured-edit-capable models", () => {
+		expect(supportsHashlineEdits("google/gemini-3.5-flash")).toBe(true);
+		expect(supportsHashlineEdits("claude-fable-5")).toBe(true);
+		expect(supportsHashlineEdits("moonshot/moonshot-v1-128k")).toBe(true);
+	});
+});
+
 describe("isQwen38PlusTemplateEffortModelId", () => {
 	test("matches Qwen 3.8+ open-weight ids across id shapes and versions", () => {
 		expect(isQwen38PlusTemplateEffortModelId("qwen3.8-27b")).toBe(true);

packages/coding-agent/src/tools/write.ts

@@ -360,12 +360,16 @@ function stripWriteContent(session: ToolSession, content: string): { text: strin
  * when the session is not in hashline mode so callers can no-op cheaply.
  *
  * Mirrors the post-commit snapshot recording the hashline patcher performs
- * after a successful edit: the model gets a tag without an extra `read`.
+ * after a successful edit — the model gets a tag without an extra `read` —
+ * but with EMPTY seen-line provenance: a write displays no numbered lines,
+ * so anchored edits against this tag must first see the anchor content (the
+ * patcher rejects them with an inline reveal). Authoring content is not
+ * knowing its line numbers.
  */
 function maybeWriteSnapshotHeader(session: ToolSession, absolutePath: string, content: string): string | undefined {
 	if (!resolveFileDisplayMode(session).hashLines) return undefined;
 	const normalized = normalizeToLF(content);
-	const tag = getFileSnapshotStore(session).record(canonicalSnapshotKey(absolutePath), normalized);
+	const tag = getFileSnapshotStore(session).record(canonicalSnapshotKey(absolutePath), normalized, []);
 	return formatHashlineHeader(formatPathRelativeToCwd(absolutePath, session.cwd), tag);
 }
 

packages/coding-agent/src/utils/edit-mode.ts

@@ -1,3 +1,4 @@
+import { supportsHashlineEdits } from "@oh-my-pi/pi-catalog/identity";
 import { $env, $flag } from "@oh-my-pi/pi-utils";
 
 export type EditMode = "replace" | "patch" | "hashline" | "apply_patch";
@@ -13,22 +14,6 @@ const EDIT_MODE_IDS = {
 
 export const EDIT_MODES = Object.keys(EDIT_MODE_IDS) as EditMode[];
 
-const HASHLINE_EXCLUDED_MODEL_MODES: Array<{ pattern: string; mode: EditMode }> = [
-	{ pattern: "kimi", mode: "replace" },
-	{ pattern: "mimo", mode: "replace" },
-	{ pattern: "deepseek-v4-flash", mode: "replace" },
-	{ pattern: "step-3.7-flash", mode: "replace" },
-];
-
-function resolveHashlineExcludedModelMode(model: string | undefined): EditMode | null {
-	if (!model) return null;
-	const modelLower = model.toLowerCase();
-	for (const entry of HASHLINE_EXCLUDED_MODEL_MODES) {
-		if (modelLower.includes(entry.pattern)) return entry.mode;
-	}
-	return null;
-}
-
 export function normalizeEditMode(mode?: string | null): EditMode | undefined {
 	if (!mode) return undefined;
 	return EDIT_MODE_IDS[mode as keyof typeof EDIT_MODE_IDS];
@@ -54,8 +39,8 @@ export function resolveEditMode(session: EditModeSessionLike): EditMode {
 
 	const settingsMode = normalizeEditMode(String(session.settings.get("edit.mode") ?? ""));
 	const mode = settingsMode ?? DEFAULT_EDIT_MODE;
-	if (mode === "hashline" && !$flag("PI_STRICT_EDIT_MODE")) {
-		return resolveHashlineExcludedModelMode(activeModel) ?? mode;
+	if (mode === "hashline" && !$flag("PI_STRICT_EDIT_MODE") && activeModel && !supportsHashlineEdits(activeModel)) {
+		return "replace";
 	}
 	return mode;
 }