fix(chunk): auto-accepted stale batch CRCs for previously-touched chunks

- Removed error on stale CRC when a chunk was already modified by an earlier batch op; the model can only know the pre-batch checksum.
- `ensure_batch_operation_target_current` now returns `Ok(true)` to signal auto-accept, skipping redundant CRC validation.
- Updated prompt to clarify batched line-scoped edits are supported and to require fully qualified chunk paths.

crates/pi-natives/src/chunk/edit.rs

@@ -261,9 +261,12 @@ fn apply_replace(
 		}
 	});
 	let requires_checksum = operation.sel.is_some() || default_crc.is_some();
-	ensure_batch_operation_target_current(state, scheduled, crc, touched_paths)?;
+	let batch_auto_accepted =
+		ensure_batch_operation_target_current(scheduled, crc, touched_paths)?;
 	let resolved = resolve_chunk_with_crc(state, anchor_selector, crc, warnings)?;
-	validate_batch_crc(resolved.chunk, resolved.crc.as_deref(), requires_checksum)?;
+	if !batch_auto_accepted {
+		validate_batch_crc(resolved.chunk, resolved.crc.as_deref(), requires_checksum)?;
+	}
 	let anchor = resolved.chunk.clone();
 
 	if let Some(line) = operation.line {
@@ -352,9 +355,12 @@ fn apply_delete(
 		}
 	});
 	let requires_checksum = operation.sel.is_some() || default_crc.is_some();
-	ensure_batch_operation_target_current(state, scheduled, crc, touched_paths)?;
+	let batch_auto_accepted =
+		ensure_batch_operation_target_current(scheduled, crc, touched_paths)?;
 	let resolved = resolve_chunk_with_crc(state, anchor_selector, crc, warnings)?;
-	validate_batch_crc(resolved.chunk, resolved.crc.as_deref(), requires_checksum)?;
+	if !batch_auto_accepted {
+		validate_batch_crc(resolved.chunk, resolved.crc.as_deref(), requires_checksum)?;
+	}
 	let anchor = resolved.chunk.clone();
 
 	let offsets = line_offsets(&state.source);
@@ -384,9 +390,12 @@ fn apply_insert(
 			None
 		}
 	});
-	ensure_batch_operation_target_current(state, scheduled, crc, touched_paths)?;
+	let batch_auto_accepted =
+		ensure_batch_operation_target_current(scheduled, crc, touched_paths)?;
 	let resolved = resolve_chunk_with_crc(state, anchor_selector, crc, warnings)?;
-	validate_batch_crc(resolved.chunk, resolved.crc.as_deref(), resolved.crc.is_some())?;
+	if !batch_auto_accepted {
+		validate_batch_crc(resolved.chunk, resolved.crc.as_deref(), resolved.crc.is_some())?;
+	}
 	let anchor = resolved.chunk.clone();
 
 	let pos = match operation.op {
@@ -601,45 +610,29 @@ fn touches_chunk_path(touched_paths: &[String], selector: &str) -> bool {
 	})
 }
 
+/// Returns `Ok(true)` when the CRC was auto-accepted (chunk was touched by an
+/// earlier batch op and the model supplied the pre-batch CRC). The caller should
+/// skip CRC validation in that case.
 fn ensure_batch_operation_target_current(
-	state: &ChunkStateInner,
 	scheduled: &ScheduledEditOperation,
 	crc: Option<&str>,
 	touched_paths: &[String],
-) -> Result<(), String> {
+) -> Result<bool, String> {
 	let Some(selector) = scheduled.requested_selector.as_deref() else {
-		return Ok(());
+		return Ok(false);
 	};
 	let Some(initial_chunk) = scheduled.initial_chunk.as_ref() else {
-		return Ok(());
+		return Ok(false);
 	};
 	let Some(cleaned_crc) = sanitize_crc(crc) else {
-		return Ok(());
+		return Ok(false);
 	};
 	if !touches_chunk_path(touched_paths, selector) || cleaned_crc != initial_chunk.checksum {
-		return Ok(());
+		return Ok(false);
 	}
-
-	let mut warnings = Vec::new();
-	let current_chunk =
-		resolve_chunk_selector(state, Some(selector), &mut warnings).map_err(|_| {
-			format!(
-				"Chunk path \"{selector}\" was changed by an earlier batch operation. Re-read after \
-				 the earlier edit and retry with the updated selector and checksum."
-			)
-		})?;
-	if current_chunk.checksum != initial_chunk.checksum {
-		return Err(format!(
-			"Chunk \"{selector}\" was changed by an earlier batch operation: checksum \"{}\" is \
-			 stale; current checksum is \"{}\" and the current file span is {}-{}. Later operations \
-			 in the same batch must use the post-edit checksum and updated line span.",
-			initial_chunk.checksum,
-			current_chunk.checksum,
-			current_chunk.start_line,
-			current_chunk.end_line
-		));
-	}
-	Ok(())
+	// The chunk was touched by an earlier operation in this batch, and the model
+	// supplied the pre-batch CRC (which is all it could know). Auto-accept.
+	Ok(true)
 }
 
 fn describe_scheduled_operation(scheduled: &ScheduledEditOperation) -> String {

packages/coding-agent/src/prompts/tools/chunk-edit.md

@@ -126,8 +126,8 @@ All examples reference this `read` output:
 - **MUST** include a `#CRC` suffix in `target` for every replace or delete edit.
 - **MUST** use updated chunk output from the edit response for follow-up edits.
 - **MUST** use the smallest correct target; do not rewrite siblings unnecessarily.
-- **MUST NOT** invent chunk paths. Copy them from `read` output including `fn_*` prefixes. Nesting uses `.`.
+- **MUST** use the **fully qualified** chunk path. Copy the complete path shown in read output — e.g. `fn_handleTerraform.try.if_2`, never just `if_2`. Short/leaf names are ambiguous.
 - For line-scoped replace edits, use file line numbers from the `read` gutter.
-- Do NOT batch multiple line-scoped replace edits on the same chunk. Combine them into one wider range or use separate calls.
+- Multiple line-scoped edits on the same chunk in one batch are fine — the engine auto-updates the checksum between operations.
 </critical>
 </output>