diff --git a/docs/tools/edit.md b/docs/tools/edit.md
index a831d5d60..cb3831bc8 100644
--- a/docs/tools/edit.md
+++ b/docs/tools/edit.md
@@ -8,7 +8,7 @@
 - Key collaborators:
   - `packages/coding-agent/src/utils/edit-mode.ts` — selects active edit mode
   - `packages/hashline/src/grammar.lark` — canonical constrained-decoding grammar
-  - `packages/hashline/src/format.ts` — sigils and header constants (`[`, `]`, `#`, `+`, `XCHG`, `DEL`, `INS`)
+  - `packages/hashline/src/format.ts` — sigils and header constants (`[`, `]`, `#`, `+`, `SWAP`, `DEL`, `INS`)
   - `packages/hashline/src/input.ts` — parses `[PATH#TAG]` sections
   - `packages/hashline/src/tokenizer.ts` / `packages/hashline/src/parser.ts` — tokenizes and parses ops
   - `packages/hashline/src/apply.ts` — applies parsed edits to file text
@@ -28,10 +28,10 @@ Patch language inside `input`:
 
 - **File header**: `[PATH#TAG]`. `TAG` is four uppercase-hex chars — a content-derived hash of the whole normalized file (`computeFileHash()`), recorded in the session snapshot store.
 - **Operations**:
-  - `XCHG N..M:` — replace original lines N..M with the body rows below.
-  - `XCHG.BLK N:` — replace the whole tree-sitter block beginning on line N (its header line through its closing line) with the body rows. The line span is resolved at apply time from the file's parse tree; point N at the line that opens the construct. The resolved span is exactly the node that begins on line N — a leading decorator, attribute, or doc-comment is a separate node and is not included; point N at the first decorator line (Python wraps `@dec` + `def` as one block) or fall back to `XCHG N..M:` to take a leading line-comment that parses as its own node (e.g. Rust `///`). On success the result echoes the matched span (`XCHG.BLK N → resolved lines A-B`). Errors (and steers to `XCHG N..M:`) when the language is unsupported, line N is blank or a closing delimiter, no node begins there, or the resolved block has a syntax error.
+  - `SWAP N..M:` — replace original lines N..M with the body rows below.
+  - `SWAP.BLK N:` — replace the whole tree-sitter block beginning on line N (its header line through its closing line) with the body rows. The line span is resolved at apply time from the file's parse tree; point N at the line that opens the construct. The resolved span is exactly the node that begins on line N — a leading decorator, attribute, or doc-comment is a separate node and is not included; point N at the first decorator line (Python wraps `@dec` + `def` as one block) or fall back to `SWAP N..M:` to take a leading line-comment that parses as its own node (e.g. Rust `///`). On success the result echoes the matched span (`SWAP.BLK N → resolved lines A-B`). Errors (and steers to `SWAP N..M:`) when the language is unsupported, line N is blank or a closing delimiter, no node begins there, or the resolved block has a syntax error.
   - `DEL N..M` — delete original lines N..M. No body.
-  - `DEL.BLK N` — delete the whole tree-sitter block beginning on line N (resolved like `XCHG.BLK N`, with the same decorator/comment caveat). No body. On success the result echoes the matched span (`DEL.BLK N → resolved lines A-B`). Same resolution failure modes and `DEL N..M` fallback.
+  - `DEL.BLK N` — delete the whole tree-sitter block beginning on line N (resolved like `SWAP.BLK N`, with the same decorator/comment caveat). No body. On success the result echoes the matched span (`DEL.BLK N → resolved lines A-B`). Same resolution failure modes and `DEL N..M` fallback.
   - `INS.PRE N:` — insert body rows immediately before line N.
   - `INS.POST N:` — insert body rows immediately after line N.
   - `INS.BLK.POST N:` — insert body rows after the last line of the tree-sitter block beginning on line N. Point N at the line that opens the construct, never its closing delimiter / last visible line; if you can see the last line already, use plain `INS.POST M:`. Same resolution failure modes and `INS.POST M:` fallback.
@@ -50,25 +50,25 @@ Anchors come from `read`/`search` output. `read` emits a `[PATH#TAG]` header fro
 
 The canonical grammar is strict, but the hand parser accepts a few non-dangerous variants:
 
-- `XCHG N:` — accepted as `XCHG N..N:`.
+- `SWAP N:` — accepted as `SWAP N..N:`.
 - `DEL N` — accepted as single-line delete.
-- Missing trailing colon on `XCHG` or `INS` — accepted.
-- `XCHG N-M:`, `XCHG N…M:`, and `XCHG N M:` — accepted as `XCHG N..M:`.
+- Missing trailing colon on `SWAP` or `INS` — accepted.
+- `SWAP N-M:`, `SWAP N…M:`, and `SWAP N M:` — accepted as `SWAP N..M:`.
 - Bare body rows with no `+` prefix are auto-prepended with `+` and a `BARE_BODY_AUTO_PIPED_WARNING` is appended.
 - `*** Begin Patch` / `*** End Patch` envelopes are silently consumed. `*** Abort` terminates parsing silently — ops parsed before the marker still apply, no warning surfaced.
 - Some malformed bracketed headers are recovered after stripping apply-patch path noise such as `Update File:` / `Add File:` and extra `***`, but the recovered header still needs a valid four-hex tag for the patcher to apply it.
 - `*** Update File:` / `*** Add File:` / `*** Delete File:` / `*** Move to:` apply_patch sentinels inside the diff body throw an `apply_patch sentinel … is not valid in hashline` error.
 - `@@`-bracketed hunk headers are rejected with guidance to write a verb header.
-- Bare `N` and bare `N M` / `N..M` headers are rejected with guidance to write `XCHG` or `DEL`.
+- Bare `N` and bare `N M` / `N..M` headers are rejected with guidance to write `SWAP` or `DEL`.
 - `DEL N..M:` and any body rows under `DEL` / `DEL.BLK` are rejected.
-- Empty `XCHG` / `INS` / `XCHG.BLK` hunks are rejected.
+- Empty `SWAP` / `INS` / `SWAP.BLK` hunks are rejected.
 - `-` body rows are rejected with `MINUS_ROW_REJECTED`.
-- `XCHG.BLK N:` / `DEL.BLK N` / `INS.BLK.POST N:` require a wired tree-sitter resolver; `XCHG.BLK` and `INS.BLK.POST` additionally need at least one `+TEXT` body row, while `DEL.BLK` takes none. An unresolvable block (unsupported language, blank/closing-delimiter line, no node beginning on N, or a syntax error in the resolved block) is rejected on the apply/final-preview path; the streaming preview silently drops it instead. Exception: `INS.BLK.POST N:` anchored on a pure closing-delimiter line is lowered to plain `INS.POST N:` with a warning — line N is the end of a block, and inserting after that end is exactly what the plain form does.
+- `SWAP.BLK N:` / `DEL.BLK N` / `INS.BLK.POST N:` require a wired tree-sitter resolver; `SWAP.BLK` and `INS.BLK.POST` additionally need at least one `+TEXT` body row, while `DEL.BLK` takes none. An unresolvable block (unsupported language, blank/closing-delimiter line, no node beginning on N, or a syntax error in the resolved block) is rejected on the apply/final-preview path; the streaming preview silently drops it instead. Exception: `INS.BLK.POST N:` anchored on a pure closing-delimiter line is lowered to plain `INS.POST N:` with a warning — line N is the end of a block, and inserting after that end is exactly what the plain form does.
 
 ## Outputs
 - Single-shot tool result; hashline mode does not use a `resolve` preview/apply handshake.
 - `content` contains one text block per call. For a successful single-file edit it is the post-edit `[path#TAG]` section header (a fresh snapshot tag for the written content), followed by a compact diff preview from `packages/hashline/src/diff-preview.ts` when one is emitted.
-- When the patch used `XCHG.BLK`/`DEL.BLK`/`INS.BLK.POST` ops (and the apply matched the tagged content), one `XCHG.BLK N → resolved lines A-B (K lines)` line per block op (single-line spans render `resolved line A (1 line)`; INS.BLK.POST appends `; body lands after line B`) is inserted between the `[PATH#TAG]` header and the diff preview, so the caller can confirm tree-sitter resolved the construct it intended.
+- When the patch used `SWAP.BLK`/`DEL.BLK`/`INS.BLK.POST` ops (and the apply matched the tagged content), one `SWAP.BLK N → resolved lines A-B (K lines)` line per block op (single-line spans render `resolved line A (1 line)`; INS.BLK.POST appends `; body lands after line B`) is inserted between the `[PATH#TAG]` header and the diff preview, so the caller can confirm tree-sitter resolved the construct it intended.
 - Parse, apply, or recovery warnings are appended as:
 
 ```text
@@ -103,7 +103,7 @@ Replace line 1 with two lines:
 
 ```text
 [a.ts#0A3B]
-XCHG 1..1:
+SWAP 1..1:
 +const X = "b";
 +export const Y = X;
 ```
@@ -144,7 +144,7 @@ INS.TAIL:
 Multi-file:
 ```text
 [src/a.ts#0A3B]
-XCHG 4..4:
+SWAP 4..4:
 +const enabled = true;
 [src/b.ts#1F7C]
 DEL 20
@@ -154,7 +154,7 @@ DEL 20
 - File snapshot tags are exactly four uppercase-hex chars — content-derived hashes (`computeFileHash()`) recorded in the per-session snapshot store.
 - The visible mismatch report shows 2 lines of context on each side (`MISMATCH_CONTEXT`) in `packages/hashline/src/messages.ts`.
 - Stale-anchor recovery uses `fuzzFactor: 0` in `packages/hashline/src/recovery.ts`.
-- `HL_FILE_PREFIX` is `[`, `HL_FILE_SUFFIX` is `]`, `HL_PAYLOAD_REPLACE` is `+`, `HL_RANGE_SEP` is `..`, `HL_FILE_HASH_SEP` is `#`, and hunk keyword constants are `XCHG` / `DEL` / `INS` (`packages/hashline/src/format.ts`).
+- `HL_FILE_PREFIX` is `[`, `HL_FILE_SUFFIX` is `]`, `HL_PAYLOAD_REPLACE` is `+`, `HL_RANGE_SEP` is `..`, `HL_FILE_HASH_SEP` is `#`, and hunk keyword constants are `SWAP` / `DEL` / `INS` (`packages/hashline/src/format.ts`).
 
 ## Errors
 - Missing section header:
@@ -162,29 +162,29 @@ DEL 20
 - Missing tag for any section:
   - `Missing hashline snapshot tag for edit to <path>; use \`[<path>#tag]\` from your latest read/search output. To create a new file, use the write tool.`
 - Stray payload line:
-  - `line N: payload line has no preceding hunk header. Use \`XCHG N..M:\`, \`DEL N..M\`, or \`INS.PRE|POST|HEAD|TAIL:\` above the body. Got "...".`
+  - `line N: payload line has no preceding hunk header. Use \`SWAP N..M:\`, \`DEL N..M\`, or \`INS.PRE|POST|HEAD|TAIL:\` above the body. Got "...".`
 - Minus row:
   - ``line N: `-` rows are not valid; hashline ranges already name the lines being changed. To insert a literal line starting with `-`, write `+-…`.``
 - Empty body-bearing hunk:
-  - `line N: \`XCHG N..M:\` needs at least one \`+TEXT\` body row. To delete lines, use \`DEL N..M\`.`
+  - `line N: \`SWAP N..M:\` needs at least one \`+TEXT\` body row. To delete lines, use \`DEL N..M\`.`
   - `line N: \`INS\` needs at least one \`+TEXT\` body row.`
-  - `line N: \`XCHG.BLK N:\` needs at least one \`+TEXT\` body row. To delete a block, use \`DEL.BLK N\`.`
+  - `line N: \`SWAP.BLK N:\` needs at least one \`+TEXT\` body row. To delete a block, use \`DEL.BLK N\`.`
 - Unresolvable block anchor (apply / final-preview path only):
-  - `line N: \`XCHG.BLK X:\` could not resolve a syntactic block beginning on line X. The language may be unsupported, the line may be blank or a closing delimiter, or the block may not parse. Use \`XCHG X..M:\` with the block's explicit end line instead.` — followed by a blank line and numbered `*`-marked context rows around line X (same shape as the mismatch preview).
+  - `line N: \`SWAP.BLK X:\` could not resolve a syntactic block beginning on line X. The language may be unsupported, the line may be blank or a closing delimiter, or the block may not parse. Use \`SWAP X..M:\` with the block's explicit end line instead.` — followed by a blank line and numbered `*`-marked context rows around line X (same shape as the mismatch preview).
   - `line N: \`INS.BLK.POST X:\` could not resolve a syntactic block beginning on line X. The language may be unsupported, the line may be blank or a closing delimiter, or the block may not parse. Use \`INS.POST M:\` with the block's explicit last line instead.` — same context preview.
 - Delete with body:
-  - `line N: \`DEL N..M\` does not take body rows. Remove the body, or use \`XCHG N..M:\`.`
-  - `line N: \`DEL.BLK N\` does not take body rows. Remove the body, or use \`XCHG.BLK N:\` to replace the block.`
+  - `line N: \`DEL N..M\` does not take body rows. Remove the body, or use \`SWAP N..M:\`.`
+  - `line N: \`DEL.BLK N\` does not take body rows. Remove the body, or use \`SWAP.BLK N:\` to replace the block.`
 - Range out of order:
   - `line N: range A..B ends before it starts.`
 - Overlapping hunks on the same anchor:
   - `line N: anchor line X is already targeted by another hunk on line Y. Issue ONE hunk per range; payload is only the final desired content, never a before/after pair.`
 - apply_patch / unified-diff contamination:
-  - `line N: apply_patch sentinel "*** …" is not valid in hashline. File sections start with \`[path#HASH]\` (no \`Update File:\` / \`Add File:\` keyword). Use \`XCHG N..M:\`, \`DEL N..M\`, or \`INS.PRE|POST|HEAD|TAIL:\` ops.`
-  - `line N: unified-diff hunk header (\`@@ -N,M +N,M @@\`) is not valid in hashline. Use \`XCHG N..M:\`, \`DEL N..M\`, or \`INS.PRE|POST|HEAD|TAIL:\` ops.`
-  - `line N: \`@@\`-bracketed hunk header "@@ …" is not valid in hashline. Drop the \`@@ ... @@\` brackets and write a verb header such as \`XCHG N..M:\`.`
-  - `line N: hunk headers need a verb. Use \`XCHG N..N:\` to replace, or \`DEL N\` to delete.`
-  - `line N: bare range hunk header "N M" is not valid. Hunk headers need a verb: write \`XCHG ${bareRange[1]}..${bareRange[2]}:\` or \`DEL ${bareRange[1]}..${bareRange[2]}\`.`
+  - `line N: apply_patch sentinel "*** …" is not valid in hashline. File sections start with \`[path#HASH]\` (no \`Update File:\` / \`Add File:\` keyword). Use \`SWAP N..M:\`, \`DEL N..M\`, or \`INS.PRE|POST|HEAD|TAIL:\` ops.`
+  - `line N: unified-diff hunk header (\`@@ -N,M +N,M @@\`) is not valid in hashline. Use \`SWAP N..M:\`, \`DEL N..M\`, or \`INS.PRE|POST|HEAD|TAIL:\` ops.`
+  - `line N: \`@@\`-bracketed hunk header "@@ …" is not valid in hashline. Drop the \`@@ ... @@\` brackets and write a verb header such as \`SWAP N..M:\`.`
+  - `line N: hunk headers need a verb. Use \`SWAP N..N:\` to replace, or \`DEL N\` to delete.`
+  - `line N: bare range hunk header "N M" is not valid. Hunk headers need a verb: write \`SWAP ${bareRange[1]}..${bareRange[2]}:\` or \`DEL ${bareRange[1]}..${bareRange[2]}\`.`
 - Out-of-range anchor:
   - `Line N does not exist (file has M lines)`
 - Stale snapshot tag: the `Patcher` first attempts snapshot-based recovery. When recovery cannot prove a valid result it throws `MismatchError`, which distinguishes recognized-but-drifted hashes from never-recorded hashes. The error includes the current file hash plus context around each anchor.
diff --git a/packages/ai/test/inband-tools.test.ts b/packages/ai/test/inband-tools.test.ts
index c621dc623..6819f5e47 100644
--- a/packages/ai/test/inband-tools.test.ts
+++ b/packages/ai/test/inband-tools.test.ts
@@ -167,7 +167,7 @@ describe("in-band tool grammars", () => {
 			assistant([
 				{
 					type: "text",
-					text: '<invoke name="read"><parameter name="path">rubygems.ts:85-93</parameter></invoke>\n<function_results>\n<result>\n<tool_name>read</tool_name>\n<stdout>[rubygems.ts#A1B2]</stdout>\n</result>\n</function_results>\n<invoke name="edit"><parameter name="input">[rubygems.ts#A1B2]\nXCHG 89..89:\n+ fake</parameter></invoke>',
+					text: '<invoke name="read"><parameter name="path">rubygems.ts:85-93</parameter></invoke>\n<function_results>\n<result>\n<tool_name>read</tool_name>\n<stdout>[rubygems.ts#A1B2]</stdout>\n</result>\n</function_results>\n<invoke name="edit"><parameter name="input">[rubygems.ts#A1B2]\nSWAP 89..89:\n+ fake</parameter></invoke>',
 				},
 			]),
 			"anthropic",
diff --git a/packages/coding-agent/src/edit/hashline/execute.ts b/packages/coding-agent/src/edit/hashline/execute.ts
index 0bdf4699f..3eac7d257 100644
--- a/packages/coding-agent/src/edit/hashline/execute.ts
+++ b/packages/coding-agent/src/edit/hashline/execute.ts
@@ -98,7 +98,7 @@ interface RenderedSection {
 }
 
 function formatBlockResolution(resolution: BlockResolution): string {
-	const op = resolution.op === "delete" ? "DEL.BLK" : resolution.op === "insert_after" ? "INS.BLK.POST" : "XCHG.BLK";
+	const op = resolution.op === "delete" ? "DEL.BLK" : resolution.op === "insert_after" ? "INS.BLK.POST" : "SWAP.BLK";
 	const lines = resolution.end - resolution.start + 1;
 	const span =
 		resolution.start === resolution.end ? `line ${resolution.start}` : `lines ${resolution.start}-${resolution.end}`;
diff --git a/packages/coding-agent/test/core/block-replace.test.ts b/packages/coding-agent/test/core/block-replace.test.ts
index 2524074b8..9379fa9dc 100644
--- a/packages/coding-agent/test/core/block-replace.test.ts
+++ b/packages/coding-agent/test/core/block-replace.test.ts
@@ -63,12 +63,12 @@ async function seedFile(
 
 const TS_SOURCE = "function x() {\n  if (y) {\n  }\n}\n";
 
-describe("XCHG.BLK — native tree-sitter resolution end-to-end", () => {
+describe("SWAP.BLK — native tree-sitter resolution end-to-end", () => {
 	it("resolves the inner `if` block (line 2) and replaces its full span", async () => {
 		await withTempDir(async tempDir => {
 			const session = makeSession(tempDir);
 			const { filePath, header } = await seedFile(tempDir, session, "x.ts", TS_SOURCE);
-			const input = `${header}\nXCHG.BLK 2:\n+  if (y || z) {\n+  }`;
+			const input = `${header}\nSWAP.BLK 2:\n+  if (y || z) {\n+  }`;
 
 			await executeHashlineSingle(executeOptions(tempDir, input, session));
 
@@ -80,7 +80,7 @@ describe("XCHG.BLK — native tree-sitter resolution end-to-end", () => {
 		await withTempDir(async tempDir => {
 			const session = makeSession(tempDir);
 			const { filePath, header } = await seedFile(tempDir, session, "x.ts", TS_SOURCE);
-			const input = `${header}\nXCHG.BLK 1:\n+function x() {\n+  return 42;\n+}`;
+			const input = `${header}\nSWAP.BLK 1:\n+function x() {\n+  return 42;\n+}`;
 
 			await executeHashlineSingle(executeOptions(tempDir, input, session));
 
@@ -104,7 +104,7 @@ describe("XCHG.BLK — native tree-sitter resolution end-to-end", () => {
 		await withTempDir(async tempDir => {
 			const session = makeSession(tempDir);
 			const { header } = await seedFile(tempDir, session, "x.ts", TS_SOURCE);
-			const input = `${header}\nXCHG.BLK 2:\n+  if (y || z) {\n+  }`;
+			const input = `${header}\nSWAP.BLK 2:\n+  if (y || z) {\n+  }`;
 
 			const result = await executeHashlineSingle(executeOptions(tempDir, input, session));
 
@@ -113,17 +113,17 @@ describe("XCHG.BLK — native tree-sitter resolution end-to-end", () => {
 		});
 	});
 
-	it("echoes the resolved span in the result text for XCHG.BLK", async () => {
+	it("echoes the resolved span in the result text for SWAP.BLK", async () => {
 		await withTempDir(async tempDir => {
 			const session = makeSession(tempDir);
 			const { header } = await seedFile(tempDir, session, "x.ts", TS_SOURCE);
-			const input = `${header}\nXCHG.BLK 1:\n+function x() {\n+  return 42;\n+}`;
+			const input = `${header}\nSWAP.BLK 1:\n+function x() {\n+  return 42;\n+}`;
 
 			const result = await executeHashlineSingle(executeOptions(tempDir, input, session));
 			const text = result.content.map(part => (part.type === "text" ? part.text : "")).join("\n");
 
 			// `function x() {` opens on line 1; tree-sitter resolves the whole body (lines 1-4).
-			expect(text).toContain("XCHG.BLK 1 → resolved lines 1-4 (4 lines)");
+			expect(text).toContain("SWAP.BLK 1 → resolved lines 1-4 (4 lines)");
 		});
 	});
 
@@ -141,16 +141,16 @@ describe("XCHG.BLK — native tree-sitter resolution end-to-end", () => {
 		});
 	});
 
-	it("rejects a lone closing delimiter (no block begins there) and steers to `XCHG N..M:`", async () => {
+	it("rejects a lone closing delimiter (no block begins there) and steers to `SWAP N..M:`", async () => {
 		await withTempDir(async tempDir => {
 			const session = makeSession(tempDir);
 			const { filePath, header } = await seedFile(tempDir, session, "x.ts", TS_SOURCE);
 			// Line 3 is `  }` — a closing delimiter, not a block opener.
-			const input = `${header}\nXCHG.BLK 3:\n+  }`;
+			const input = `${header}\nSWAP.BLK 3:\n+  }`;
 
 			// Steers to the concrete form and previews the file around the anchor (`*`-marked).
 			await expect(executeHashlineSingle(executeOptions(tempDir, input, session))).rejects.toThrow(
-				/could not resolve a syntactic block beginning on line 3.*XCHG 3\.\.M:.*^ 1:function x\(\) \{$.*^\*3: {2}\}$/ms,
+				/could not resolve a syntactic block beginning on line 3.*SWAP 3\.\.M:.*^ 1:function x\(\) \{$.*^\*3: {2}\}$/ms,
 			);
 			// Disk untouched — refusal never leaves a partial write.
 			expect(await Bun.file(filePath).text()).toBe(TS_SOURCE);
@@ -162,7 +162,7 @@ describe("XCHG.BLK — native tree-sitter resolution end-to-end", () => {
 			const session = makeSession(tempDir);
 			const source = "alpha\nbeta\ngamma\n";
 			const { filePath, header } = await seedFile(tempDir, session, "data.unknownext", source);
-			const input = `${header}\nXCHG.BLK 1:\n+ALPHA`;
+			const input = `${header}\nSWAP.BLK 1:\n+ALPHA`;
 
 			await expect(executeHashlineSingle(executeOptions(tempDir, input, session))).rejects.toThrow(
 				/could not resolve a syntactic block/,
diff --git a/packages/coding-agent/test/core/hashline-loop-guard.test.ts b/packages/coding-agent/test/core/hashline-loop-guard.test.ts
index e00f93fdf..c0dcc4866 100644
--- a/packages/coding-agent/test/core/hashline-loop-guard.test.ts
+++ b/packages/coding-agent/test/core/hashline-loop-guard.test.ts
@@ -54,7 +54,7 @@ async function withTempDir(fn: (tempDir: string) => Promise<void>): Promise<void
 function buildNoopInput(filePath: string, displayPath: string, session: ToolSession): string {
 	const source = "aaa\nbbb\nccc\n";
 	const tag = getFileReadCache(session).record(filePath, source);
-	return `${formatHashlineHeader(displayPath, tag)}\nreplace 2..2:\n+bbb\n`;
+	return `${formatHashlineHeader(displayPath, tag)}\nSWAP 2..2:\n+bbb\n`;
 }
 
 describe("hashline noop loop guard", () => {
@@ -144,7 +144,7 @@ describe("hashline noop loop guard", () => {
 			// from the model's perspective.
 			const source = "aaa\nbbb\nccc\n";
 			const tag = getFileReadCache(session).record(filePath, source);
-			const realEdit = `${formatHashlineHeader("a.ts", tag)}\nreplace 2..2:\n+BBB\n`;
+			const realEdit = `${formatHashlineHeader("a.ts", tag)}\nSWAP 2..2:\n+BBB\n`;
 			const editResult = await executeHashlineSingle(execOptions(realEdit, session));
 			expect(editResult.content[0]?.type === "text" ? editResult.content[0].text : "").not.toContain(
 				"byte-identical to the file",
@@ -156,7 +156,7 @@ describe("hashline noop loop guard", () => {
 			// soft-hint regime.
 			const newSource = "aaa\nBBB\nccc\n";
 			const newTag = getFileReadCache(session).record(filePath, newSource);
-			const newNoop = `${formatHashlineHeader("a.ts", newTag)}\nreplace 2..2:\n+BBB\n`;
+			const newNoop = `${formatHashlineHeader("a.ts", newTag)}\nSWAP 2..2:\n+BBB\n`;
 			const result = await executeHashlineSingle(execOptions(newNoop, session));
 			expect(result.content[0]?.type === "text" ? result.content[0].text : "").toContain(
 				"byte-identical to the file",
diff --git a/packages/coding-agent/test/core/hashline.test.ts b/packages/coding-agent/test/core/hashline.test.ts
index 89f44889d..28474ba1b 100644
--- a/packages/coding-agent/test/core/hashline.test.ts
+++ b/packages/coding-agent/test/core/hashline.test.ts
@@ -45,7 +45,7 @@ function header(filePath: string, tag: string): string {
 }
 
 function sameLineRange(anchor: string): string {
-	return `replace ${anchor}..${anchor}:`;
+	return `SWAP ${anchor}..${anchor}:`;
 }
 
 async function withTempDir(fn: (tempDir: string) => Promise<void>): Promise<void> {
@@ -85,7 +85,7 @@ function hashlineExecuteOptions(
 describe("hashline executor", () => {
 	it("rejects file creation and directs to the write tool", async () => {
 		await withTempDir(async tempDir => {
-			const input = `[new.ts]\ninsert head:\n${repl("export const x = 1;")}\n`;
+			const input = `[new.ts]\nINS.HEAD:\n${repl("export const x = 1;")}\n`;
 			await expect(executeHashlineSingle(hashlineExecuteOptions(tempDir, input))).rejects.toThrow(/write tool/);
 			expect(await Bun.file(path.join(tempDir, "new.ts")).exists()).toBe(false);
 		});
@@ -98,7 +98,7 @@ describe("hashline executor", () => {
 
 			await Bun.write(filePath, source);
 			const sourceTag = recordFullSnapshot(getFileReadCache(session), filePath, source);
-			const input = `${header("a.ts", sourceTag)}\ninsert tail:\n${repl("bbb")}\n${repl("ccc")}\n${repl("NEW")}\n`;
+			const input = `${header("a.ts", sourceTag)}\nINS.TAIL:\n${repl("bbb")}\n${repl("ccc")}\n${repl("NEW")}\n`;
 			const result = await executeHashlineSingle(hashlineExecuteOptions(tempDir, input, undefined, session));
 			const text = result.content[0]?.type === "text" ? result.content[0].text : "";
 
@@ -203,7 +203,7 @@ describe("hashline executor", () => {
 				repl("L2h"),
 				repl("L2i"),
 				header("a.ts", originalTag),
-				`insert after ${tag(8, "L8")}:`,
+				`INS.POST ${tag(8, "L8")}:`,
 				repl("INSERTED"),
 			].join("\n");
 
@@ -250,14 +250,14 @@ describe("hashlineEditParamsSchema — payload shape", () => {
 
 	it("tolerates provider extra fields without declaring `path`", () => {
 		expect(
-			hashlineEditParamsSchema.safeParse({ path: "x.ts", input: `[x.ts]\ninsert head:\n${repl("x")}` }).success,
+			hashlineEditParamsSchema.safeParse({ path: "x.ts", input: `[x.ts]\nINS.HEAD:\n${repl("x")}` }).success,
 		).toBe(true);
 	});
 
 	it("accepts `_input` as a provider-emitted alias for `input`", () => {
-		const parsed = hashlineEditParamsSchema.safeParse({ _input: `[x.ts]\ninsert head:\n${repl("x")}` });
+		const parsed = hashlineEditParamsSchema.safeParse({ _input: `[x.ts]\nINS.HEAD:\n${repl("x")}` });
 		expect(parsed.success).toBe(true);
-		if (parsed.success) expect(parsed.data.input).toBe(`[x.ts]\ninsert head:\n${repl("x")}`);
+		if (parsed.success) expect(parsed.data.input).toBe(`[x.ts]\nINS.HEAD:\n${repl("x")}`);
 	});
 
 	it("still requires `input`", () => {
diff --git a/packages/coding-agent/test/edit-diff.test.ts b/packages/coding-agent/test/edit-diff.test.ts
index e82fa3ac4..d5739d27c 100644
--- a/packages/coding-agent/test/edit-diff.test.ts
+++ b/packages/coding-agent/test/edit-diff.test.ts
@@ -236,12 +236,12 @@ describe("computeHashlineDiff", () => {
 		const line = "unchanged content";
 		await Bun.write(sourcePath, `${line}\n`);
 
-		// `replace 1..1:` with the same line in the body is a true no-op: the edit
+		// `SWAP 1..1:` with the same line in the body is a true no-op: the edit
 		// fires through computeHashlineDiff but produces identical content.
 		const text = `${line}\n`;
 		const snapshotStore = new InMemorySnapshotStore();
 		const tag = snapshotStore.record(sourcePath, text);
-		const input = `${formatHashlineHeader(sourcePath, tag)}\nreplace 1..1:\n+${line}\n`;
+		const input = `${formatHashlineHeader(sourcePath, tag)}\nSWAP 1..1:\n+${line}\n`;
 		const result = await computeHashlineDiff({ input }, tempDir, snapshotStore);
 		expect("error" in result).toBe(true);
 		if ("error" in result) {
@@ -257,7 +257,7 @@ describe("computeHashlineDiff", () => {
 		const snapshotStore = new InMemorySnapshotStore();
 		const tag = snapshotStore.record(sourcePath, text);
 		const result = await computeHashlineDiff(
-			{ input: `${formatHashlineHeader(sourcePath, tag)}\ninsert tail:\n+second` },
+			{ input: `${formatHashlineHeader(sourcePath, tag)}\nINS.TAIL:\n+second` },
 			tempDir,
 			snapshotStore,
 		);
@@ -271,12 +271,12 @@ describe("computeHashlineDiff", () => {
 		const relativePath = "source.txt";
 		await Bun.write(path.join(tempDir, relativePath), "first\n");
 
-		// A tagless `insert tail:` carries no anchored edit, yet the apply path
+		// A tagless `INS.TAIL:` carries no anchored edit, yet the apply path
 		// (Patcher.prepare) rejects it for the missing mandatory tag. The
 		// preview/diff path MUST emit the SAME rejection so a successful preview
 		// never precedes a failing apply.
 		const result = await computeHashlineDiff(
-			{ input: `[${relativePath}]\ninsert tail:\n+second` },
+			{ input: `[${relativePath}]\nINS.TAIL:\n+second` },
 			tempDir,
 			new InMemorySnapshotStore(),
 		);
@@ -287,7 +287,7 @@ describe("computeHashlineDiff", () => {
 	});
 	test("returns a handled error when the source path is a local URL", async () => {
 		const result = await computeHashlineDiff(
-			{ input: "[local://PLAN.md]\ninsert tail:\n+x" },
+			{ input: "[local://PLAN.md]\nINS.TAIL:\n+x" },
 			tempDir,
 			new InMemorySnapshotStore(),
 		);
diff --git a/packages/coding-agent/test/edit-streaming-preview.test.ts b/packages/coding-agent/test/edit-streaming-preview.test.ts
index 8eb4c6795..9294c55b5 100644
--- a/packages/coding-agent/test/edit-streaming-preview.test.ts
+++ b/packages/coding-agent/test/edit-streaming-preview.test.ts
@@ -66,7 +66,7 @@ describe("hashline streaming preview (multi-section)", () => {
 	const ctx = (cwd: string) => ({ cwd, signal: new AbortController().signal, snapshots });
 
 	test("keeps section A's preview when section B's header just arrived", async () => {
-		const input = [headerA, "insert head:", "+// new", headerB].join("\n");
+		const input = [headerA, "INS.HEAD:", "+// new", headerB].join("\n");
 		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
 		expect(previews).not.toBeNull();
 		expect(previews).toHaveLength(1);
@@ -77,7 +77,7 @@ describe("hashline streaming preview (multi-section)", () => {
 
 	test("ignores parse errors from the trailing in-progress section", async () => {
 		// `7:bad` has invalid payload — the trailing section is still being typed.
-		const input = [headerA, "insert head:", "+// new", headerB, "7:bad"].join("\n");
+		const input = [headerA, "INS.HEAD:", "+// new", headerB, "7:bad"].join("\n");
 		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
 		expect(previews).not.toBeNull();
 		expect(previews).toHaveLength(1);
@@ -86,7 +86,7 @@ describe("hashline streaming preview (multi-section)", () => {
 	});
 
 	test("renders both sections once each has at least one valid op", async () => {
-		const input = [headerA, "insert head:", "+// new a", headerB, "insert head:", "+// new b"].join("\n");
+		const input = [headerA, "INS.HEAD:", "+// new a", headerB, "INS.HEAD:", "+// new b"].join("\n");
 		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
 		expect(previews).toHaveLength(2);
 		expect(previews?.map(p => p.path).sort()).toEqual(["a.ts", "b.ts"]);
@@ -128,7 +128,7 @@ describe("hashline streaming preview (single-op trailing payload)", () => {
 		// The `+` payload has no trailing newline — the common single-op case
 		// the trailing-line trim used to erase, collapsing the preview to a
 		// "No changes" error that rendered as a blank box for the whole stream.
-		const input = `${header}\nreplace 2..2:\n+const b = 22`;
+		const input = `${header}\nSWAP 2..2:\n+const b = 22`;
 		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
 		expect(previews).toHaveLength(1);
 		expect(previews?.[0]?.error).toBeUndefined();
@@ -136,7 +136,7 @@ describe("hashline streaming preview (single-op trailing payload)", () => {
 	});
 
 	test("does not surface stale hash errors while streaming", async () => {
-		const input = "[a.ts#FFFF]\nreplace 2..2:\n+const b = 22";
+		const input = "[a.ts#FFFF]\nSWAP 2..2:\n+const b = 22";
 		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
 		expect(previews).toHaveLength(1);
 		expect(previews?.[0]?.error).toBeUndefined();
@@ -145,7 +145,7 @@ describe("hashline streaming preview (single-op trailing payload)", () => {
 
 	test("final preview accepts a live content hash even when the snapshot store has no history", async () => {
 		const liveHeader = formatHashlineHeader("a.ts", computeFileHash(text));
-		const input = `${liveHeader}\nreplace 2..2:\n+const b = 22\n`;
+		const input = `${liveHeader}\nSWAP 2..2:\n+const b = 22\n`;
 		const previews = await strategy.computeDiffPreview(
 			{ input } as never,
 			{
@@ -162,7 +162,7 @@ describe("hashline streaming preview (single-op trailing payload)", () => {
 
 	test("final preview recovers a stale tag from snapshot history", async () => {
 		await Bun.write(file, `// external\n${text}`);
-		const input = `${header}\nreplace 2..2:\n+const b = 22\n`;
+		const input = `${header}\nSWAP 2..2:\n+const b = 22\n`;
 		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir, false) as never);
 		expect(previews).toHaveLength(1);
 		expect(previews?.[0]?.error).toBeUndefined();
@@ -170,7 +170,7 @@ describe("hashline streaming preview (single-op trailing payload)", () => {
 	});
 
 	test("surfaces stale hash errors once streaming is complete", async () => {
-		const input = "[a.ts#FFFF]\nreplace 2..2:\n+const b = 22\n";
+		const input = "[a.ts#FFFF]\nSWAP 2..2:\n+const b = 22\n";
 		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir, false) as never);
 		expect(previews).toHaveLength(1);
 		expect(previews?.[0]?.error).toContain("not from this session");
@@ -180,7 +180,7 @@ describe("hashline streaming preview (single-op trailing payload)", () => {
 		// Op header typed, payload still empty: applyPartialTo drops the
 		// payload-less op so nothing changes yet. The preview must report null
 		// (preserving any prior frame), never a 'No changes' error that wipes it.
-		const input = `${header}\nreplace 2..2:\n`;
+		const input = `${header}\nSWAP 2..2:\n`;
 		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
 		expect(previews).toBeNull();
 	});
@@ -217,7 +217,7 @@ describe("hashline streaming preview (monotonic growth)", () => {
 	const ctx = (cwd: string) => ({ cwd, signal: new AbortController().signal, snapshots, isStreaming: true });
 	// Replace the 20-line body (lines 2..21) with the first `n` payload rows.
 	const buildInput = (n: number) =>
-		`${header}\nreplace 2..21:\n${payload
+		`${header}\nSWAP 2..21:\n${payload
 			.slice(0, n)
 			.map(l => `+${l}`)
 			.join("\n")}`;
@@ -304,12 +304,12 @@ describe("apply_patch streaming preview (trailing partial line)", () => {
 
 describe("matcherDigest", () => {
 	test("hashline: digests stripped `+` body rows only, never headers or op lines", () => {
-		const input = ["[a.ts#AB12]", "replace 1..2:", "+const x = 1;", "+const y = 2;", "delete 5", ""].join("\n");
+		const input = ["[a.ts#AB12]", "SWAP 1..2:", "+const x = 1;", "+const y = 2;", "DEL 5", ""].join("\n");
 		expect(EDIT_MODE_STRATEGIES.hashline.matcherDigest({ input })).toBe("const x = 1;\nconst y = 2;");
 	});
 
 	test("hashline: grammar-only payload digests to empty, missing input to undefined", () => {
-		expect(EDIT_MODE_STRATEGIES.hashline.matcherDigest({ input: "[a.ts#AB12]\ndelete 3\n" })).toBe("");
+		expect(EDIT_MODE_STRATEGIES.hashline.matcherDigest({ input: "[a.ts#AB12]\nDEL 3\n" })).toBe("");
 		expect(EDIT_MODE_STRATEGIES.hashline.matcherDigest({})).toBeUndefined();
 	});
 
diff --git a/packages/coding-agent/test/edit/seen-line-guard.test.ts b/packages/coding-agent/test/edit/seen-line-guard.test.ts
index 7c192658f..e5f345d46 100644
--- a/packages/coding-agent/test/edit/seen-line-guard.test.ts
+++ b/packages/coding-agent/test/edit/seen-line-guard.test.ts
@@ -93,7 +93,7 @@ describe("read → edit seen-line guard", () => {
 		const tag = tagFromOutput(resultText(read));
 
 		await expect(
-			executeHashlineSingle(execOptions(`[notes.txt#${tag}]\nreplace 12..12:\n+EDITED`, session)),
+			executeHashlineSingle(execOptions(`[notes.txt#${tag}]\nSWAP 12..12:\n+EDITED`, session)),
 		).rejects.toThrow(/were not shown in the read\/search output/);
 		// The reject left the file untouched.
 		expect(await Bun.file(file).text()).toBe(CONTENT);
@@ -107,7 +107,7 @@ describe("read → edit seen-line guard", () => {
 		const read = await new ReadTool(session).execute("r1", { path: `${file}:1-3` });
 		const tag = tagFromOutput(resultText(read));
 
-		await executeHashlineSingle(execOptions(`[notes.txt#${tag}]\nreplace 2..2:\n+EDITED`, session));
+		await executeHashlineSingle(execOptions(`[notes.txt#${tag}]\nSWAP 2..2:\n+EDITED`, session));
 		expect(await Bun.file(file).text()).toContain("EDITED");
 	});
 });
@@ -154,7 +154,7 @@ describe("search → edit seen-line guard", () => {
 		expect(seen?.has(8)).toBe(false);
 
 		// The matched line is in the seen set, so editing it applies.
-		await executeHashlineSingle(execOptions(`[code.txt#${tag}]\nreplace 4..4:\n+NEEDLE edited`, session));
+		await executeHashlineSingle(execOptions(`[code.txt#${tag}]\nSWAP 4..4:\n+NEEDLE edited`, session));
 		expect(await Bun.file(file).text()).toContain("NEEDLE edited");
 	});
 
@@ -167,7 +167,7 @@ describe("search → edit seen-line guard", () => {
 		const search = await new SearchTool(session).execute("s1", { pattern: "NEEDLE", paths: [file] });
 		const tag = tagFromOutput(resultText(search));
 
-		await expect(executeHashlineSingle(execOptions(`[code.txt#${tag}]\nreplace 8..8:\n+X`, session))).rejects.toThrow(
+		await expect(executeHashlineSingle(execOptions(`[code.txt#${tag}]\nSWAP 8..8:\n+X`, session))).rejects.toThrow(
 			/were not shown in the read\/search output/,
 		);
 		expect(await Bun.file(file).text()).toBe(`${lines.join("\n")}\n`);
diff --git a/packages/coding-agent/test/read-column-truncation-snapshot.test.ts b/packages/coding-agent/test/read-column-truncation-snapshot.test.ts
index e98c22091..a5f973390 100644
--- a/packages/coding-agent/test/read-column-truncation-snapshot.test.ts
+++ b/packages/coding-agent/test/read-column-truncation-snapshot.test.ts
@@ -175,7 +175,7 @@ describe("read tool column truncation vs hashline snapshot", () => {
 			tmpDir,
 			filePath,
 			header,
-			patchBody: "replace 3..3:\n+epilogue\n",
+			patchBody: "SWAP 3..3:\n+epilogue\n",
 		});
 
 		const after = await fs.readFile(filePath, "utf8");
diff --git a/packages/coding-agent/test/tools/edit-renderer.test.ts b/packages/coding-agent/test/tools/edit-renderer.test.ts
index 23f4207c0..12e20cdfc 100644
--- a/packages/coding-agent/test/tools/edit-renderer.test.ts
+++ b/packages/coding-agent/test/tools/edit-renderer.test.ts
@@ -87,7 +87,7 @@ describe("editToolRenderer", () => {
 		const uiTheme = await getUiTheme();
 		const component = editToolRenderer.renderCall(
 			{
-				input: "[packages/coding-agent/src/edit/renderer.ts]\ninsert tail:\n+// preview",
+				input: "[packages/coding-agent/src/edit/renderer.ts]\nINS.TAIL:\n+// preview",
 			},
 			{ expanded: false, isPartial: true, spinnerFrame: 0, renderContext: { editMode: "hashline" } },
 			uiTheme,
@@ -108,7 +108,7 @@ describe("editToolRenderer", () => {
 				input: [
 					"*** Begin Patch",
 					"[crates/pi-natives/src/shell.rs]",
-					"insert tail:",
+					"INS.TAIL:",
 					"+pub fn streaming_preview() {",
 				].join("\n"),
 			},
@@ -119,7 +119,7 @@ describe("editToolRenderer", () => {
 
 		const rendered = Bun.stripANSI(component.render(160).join("\n"));
 		expect(rendered).toContain("crates/pi-natives/src/shell.rs");
-		expect(rendered).not.toContain("insert tail:");
+		expect(rendered).not.toContain("INS.TAIL:");
 		expect(rendered).not.toContain("+pub fn streaming_preview() {");
 		expect(rendered).not.toContain("*** Begin Patch");
 	});
@@ -128,7 +128,7 @@ describe("editToolRenderer", () => {
 		const uiTheme = await getUiTheme();
 		const compactComponent = editToolRenderer.renderCall(
 			{
-				input: "[foo bar.ts]\ninsert head:\n+// preview",
+				input: "[foo bar.ts]\nINS.HEAD:\n+// preview",
 			},
 			{ expanded: true, isPartial: true, spinnerFrame: 0, renderContext: { editMode: "hashline" } },
 			uiTheme,
@@ -136,7 +136,7 @@ describe("editToolRenderer", () => {
 
 		const quotedComponent = editToolRenderer.renderCall(
 			{
-				input: "['baz qux.ts']\ninsert head:\n+// preview",
+				input: "['baz qux.ts']\nINS.HEAD:\n+// preview",
 			},
 			{ expanded: false, isPartial: true, spinnerFrame: 0, renderContext: { editMode: "hashline" } },
 			uiTheme,
@@ -155,7 +155,7 @@ describe("editToolRenderer", () => {
 		// renderer keeps the title clean.
 		const canonical = editToolRenderer.renderCall(
 			{
-				input: "[packages/coding-agent/src/slash-commands/builtin-registry.ts]\ninsert head:\n+// preview",
+				input: "[packages/coding-agent/src/slash-commands/builtin-registry.ts]\nINS.HEAD:\n+// preview",
 			},
 			{ expanded: true, isPartial: true, spinnerFrame: 0, renderContext: { editMode: "hashline" } },
 			uiTheme,
@@ -163,7 +163,7 @@ describe("editToolRenderer", () => {
 
 		// While streaming, the closing bracket may not have arrived yet.
 		const partial = editToolRenderer.renderCall(
-			{ input: "[a/b/c.ts\ninsert head:\n+// preview" },
+			{ input: "[a/b/c.ts\nINS.HEAD:\n+// preview" },
 			{ expanded: true, isPartial: true, spinnerFrame: 0, renderContext: { editMode: "hashline" } },
 			uiTheme,
 		);
@@ -190,7 +190,7 @@ describe("editToolRenderer", () => {
 			{ expanded: false, isPartial: false, renderContext: { editMode: "hashline" } },
 			uiTheme,
 			{
-				input: "[packages/coding-agent/src/edit/renderer.ts]\ninsert tail:\n+// preview",
+				input: "[packages/coding-agent/src/edit/renderer.ts]\nINS.TAIL:\n+// preview",
 			},
 		);
 
@@ -277,7 +277,7 @@ describe("editToolRenderer", () => {
 			// The trailing payload line carries no newline — the common shape for a
 			// single-line edit. The streaming pass trims that in-flight line, so the
 			// preview only becomes computable once args are marked complete.
-			const input = `[memory.ts#${tag}]\nreplace 2..2:\n+export const b = 22;`;
+			const input = `[memory.ts#${tag}]\nSWAP 2..2:\n+export const b = 22;`;
 			const component = new ToolExecutionComponent("edit", { input }, { snapshots }, hashlineTool, uiStub, tmpDir);
 
 			component.setArgsComplete();
@@ -304,7 +304,7 @@ describe("editToolRenderer", () => {
 
 			const snapshots = new InMemorySnapshotStore();
 			const tag = snapshots.record(filePath, content);
-			const input = `[memory.ts#${tag}]\nreplace 2..2:\n+export const b = 22;\n`;
+			const input = `[memory.ts#${tag}]\nSWAP 2..2:\n+export const b = 22;\n`;
 			const component = new ToolExecutionComponent(
 				"edit",
 				{ __partialJson: input },
diff --git a/packages/coding-agent/test/tools/eval-timeout.test.ts b/packages/coding-agent/test/tools/eval-timeout.test.ts
index 2f3dd7fcc..3f215bc82 100644
--- a/packages/coding-agent/test/tools/eval-timeout.test.ts
+++ b/packages/coding-agent/test/tools/eval-timeout.test.ts
@@ -31,7 +31,7 @@ describe("EvalTool timeout semantics", () => {
 		// 1s budget; the cell idles for 5s and emits no status, so nothing extends
 		// the budget — it must be cut off at the wall-clock limit.
 		const result = await tool.execute("call-compute-timeout", {
-			cells: [{ language: "js", code: "await Bun.sleep(5000); return 'never';", timeout: 1 }],
+			cells: [{ language: "js", code: "await Bun.sleep(2000); return 'never';", timeout: 1 }],
 		});
 
 		const text = result.content
diff --git a/packages/coding-agent/test/write-hashline-header.test.ts b/packages/coding-agent/test/write-hashline-header.test.ts
index ea8f0e362..7774c230f 100644
--- a/packages/coding-agent/test/write-hashline-header.test.ts
+++ b/packages/coding-agent/test/write-hashline-header.test.ts
@@ -82,7 +82,7 @@ describe("write tool hashline header", () => {
 
 		// Apply a hashline patch immediately, using only the tag the write tool
 		// returned — no intervening `read`.
-		const patchInput = `${headerLine}\nreplace 1..1:\n+export const enabled = true;\n`;
+		const patchInput = `${headerLine}\nSWAP 1..1:\n+export const enabled = true;\n`;
 		const patch = Patch.parse(patchInput, { cwd: tmpDir });
 		expect(patch.sections).toHaveLength(1);
 
diff --git a/packages/hashline/CHANGELOG.md b/packages/hashline/CHANGELOG.md
index db4d032ce..b65566cab 100644
--- a/packages/hashline/CHANGELOG.md
+++ b/packages/hashline/CHANGELOG.md
@@ -5,10 +5,10 @@
 ### Breaking Changes
 
 - Renamed all hashline DSL operators to concise abbreviated keywords:
-  - `replace` -> `XCHG`
+  - `replace` -> `SWAP`
   - `delete` -> `DEL`
   - `insert before`/`after`/`head`/`tail` -> `INS.PRE`/`POST`/`HEAD`/`TAIL`
-  - `replace_block` -> `XCHG.BLK`
+  - `replace_block` -> `SWAP.BLK`
   - `delete_block` -> `DEL.BLK`
   - `insert_after_block` -> `INS.BLK.POST`
 
diff --git a/packages/hashline/README.md b/packages/hashline/README.md
index 537eafecd..cf0e8e952 100644
--- a/packages/hashline/README.md
+++ b/packages/hashline/README.md
@@ -26,7 +26,7 @@ await fs.writeText("hello.ts", before);
 const tag = snapshots.record("hello.ts", before);
 const patcher = new Patcher({ fs, snapshots });
 const patch = Patch.parse(String.raw`[hello.ts#${tag}]
-XCHG 1..1:
+SWAP 1..1:
 +const greeting = "hello";`);
 const result = await patcher.apply(patch);
 
@@ -47,8 +47,8 @@ still matches the recorded content hash, and refusing or attempting
 session-aware recovery on mismatch.
 
 Inside a section:
-- `XCHG A..B:` — replace lines A..B with following `+TEXT` body rows.
-- `XCHG.BLK A:` — replace the syntactic block beginning on line A.
+- `SWAP A..B:` — replace lines A..B with following `+TEXT` body rows.
+- `SWAP.BLK A:` — replace the syntactic block beginning on line A.
 - `DEL A..B` / `DEL.BLK A` — delete concrete lines or a resolved block.
 - `INS.PRE A:` / `INS.POST A:` / `INS.HEAD:` / `INS.TAIL:` — insert following body rows.
 - `INS.BLK.POST A:` — insert following body rows after the resolved block's last line.
diff --git a/packages/hashline/src/format.ts b/packages/hashline/src/format.ts
index 315c2a4ef..a1a5c2571 100644
--- a/packages/hashline/src/format.ts
+++ b/packages/hashline/src/format.ts
@@ -14,7 +14,7 @@ export const HL_FILE_SUFFIX = "]";
 export const HL_PAYLOAD_REPLACE = "+";
 
 /** Hunk-header keyword for concrete line replacement. */
-export const HL_REPLACE_KEYWORD = "XCHG";
+export const HL_REPLACE_KEYWORD = "SWAP";
 /** Hunk-header keyword for concrete line deletion. */
 export const HL_DELETE_KEYWORD = "DEL";
 /** Hunk-header keyword for insertion operations. */
@@ -27,8 +27,8 @@ export const HL_INSERT_AFTER = "POST";
 export const HL_INSERT_HEAD = "HEAD";
 /** Insert position keyword for inserting at the end of the file. */
 export const HL_INSERT_TAIL = "TAIL";
-/** Hunk-header keyword: `XCHG.BLK N:` resolves N to a tree-sitter block range and replaces its span. */
-export const HL_REPLACE_BLOCK_KEYWORD = "XCHG.BLK";
+/** Hunk-header keyword: `SWAP.BLK N:` resolves N to a tree-sitter block range and replaces its span. */
+export const HL_REPLACE_BLOCK_KEYWORD = "SWAP.BLK";
 /** Hunk-header keyword: `DEL.BLK N` resolves N to a tree-sitter block range and deletes its span. */
 export const HL_DELETE_BLOCK_KEYWORD = "DEL.BLK";
 /** Hunk-header keyword: `INS.BLK.POST N:` inserts after the last line of the tree-sitter block at N. */
diff --git a/packages/hashline/src/grammar.lark b/packages/hashline/src/grammar.lark
index ae19f7b1f..772acdd71 100644
--- a/packages/hashline/src/grammar.lark
+++ b/packages/hashline/src/grammar.lark
@@ -14,8 +14,8 @@ insert_hunk: insert_anchor LF emit_op+
 insert_block_hunk: insert_block_anchor LF emit_op+
 delete_hunk: "DEL " header_range LF
 delete_block_hunk: "DEL.BLK " LID LF
-replace_anchor: "XCHG " header_range ":"
-replace_block_anchor: "XCHG.BLK " LID ":"
+replace_anchor: "SWAP " header_range ":"
+replace_block_anchor: "SWAP.BLK " LID ":"
 insert_anchor:  "INS." insert_pos ":"
 insert_block_anchor: "INS.BLK.POST " LID ":"
 insert_pos: "PRE " LID | "POST " LID | "HEAD" | "TAIL"
diff --git a/packages/hashline/src/messages.ts b/packages/hashline/src/messages.ts
index 69e37554f..b8e37b191 100644
--- a/packages/hashline/src/messages.ts
+++ b/packages/hashline/src/messages.ts
@@ -44,10 +44,10 @@ export const ABORT_MARKER = "*** Abort";
 
 /** Two consecutive hunks targeted the exact same concrete range. */
 export const REPLACE_PAIR_COALESCED_WARNING =
-	"Two hunks targeted the same range; kept only the second. One `XCHG N..M:` hunk per range — the body is the final content, never old+new.";
+	"Two hunks targeted the same range; kept only the second. One `SWAP N..M:` hunk per range — the body is the final content, never old+new.";
 
 /** Bare bodyless hunk followed by an overlapping concrete hunk. */
-("Dropped a bare hunk overlapped by the concrete hunk after it. One `XCHG N..M:` hunk per range — the body is the final content, never old+new.");
+("Dropped a bare hunk overlapped by the concrete hunk after it. One `SWAP N..M:` hunk per range — the body is the final content, never old+new.");
 
 /** Bare body rows auto-converted to literal `+` rows. */
 export const BARE_BODY_AUTO_PIPED_WARNING =
@@ -58,10 +58,10 @@ export const MINUS_ROW_REJECTED =
 	"`-` rows are not valid; the range already names the lines being changed. For a literal `-` line, write `+-…`.";
 
 /** Replace hunk with no body. */
-export const EMPTY_REPLACE = "`XCHG N..M:` needs at least one `+TEXT` body row. To delete lines, use `DEL N..M`.";
+export const EMPTY_REPLACE = "`SWAP N..M:` needs at least one `+TEXT` body row. To delete lines, use `DEL N..M`.";
 
 /** `replace_block N:` hunk with no body. */
-export const EMPTY_BLOCK = "`XCHG.BLK N:` needs at least one `+TEXT` body row. To delete a block, use `DEL.BLK N`.";
+export const EMPTY_BLOCK = "`SWAP.BLK N:` needs at least one `+TEXT` body row. To delete a block, use `DEL.BLK N`.";
 
 /**
  * Block-anchored replace/delete could not resolve to a syntactic block
@@ -76,8 +76,8 @@ export function blockUnresolvedMessage(
 	op: "replace" | "delete" = "replace",
 	fileLines?: readonly string[],
 ): string {
-	const phrase = op === "delete" ? `DEL.BLK ${line}` : `XCHG.BLK ${line}:`;
-	const fallback = op === "delete" ? `DEL ${line}..M` : `XCHG ${line}..M:`;
+	const phrase = op === "delete" ? `DEL.BLK ${line}` : `SWAP.BLK ${line}:`;
+	const fallback = op === "delete" ? `DEL ${line}..M` : `SWAP ${line}..M:`;
 	let message =
 		`\`${phrase}\` could not resolve a syntactic block beginning on line ${line} ` +
 		`(unsupported language, blank/closer line, or parse error). Use \`${fallback}\` with explicit lines.`;
@@ -90,7 +90,7 @@ export function blockUnresolvedMessage(
 
 /** Block-anchored edit reached a path with no {@link BlockResolver} wired in — a host-configuration bug. */
 export const BLOCK_RESOLVER_UNAVAILABLE =
-	"`XCHG.BLK`/`DEL.BLK`/`INS.BLK.POST` are not available here (no block resolver configured). Use a concrete line range.";
+	"`SWAP.BLK`/`DEL.BLK`/`INS.BLK.POST` are not available here (no block resolver configured). Use a concrete line range.";
 
 /**
  * `insert_after_block N:` anchored on a closing-delimiter line, lowered to
@@ -115,13 +115,13 @@ export function insertAfterBlockUnresolvedLoweredWarning(line: number): string {
  * edit; `resolveBlockEdits` must run first. Wiring bug, not authored input.
  */
 export const UNRESOLVED_BLOCK_INTERNAL =
-	"internal error: unresolved `XCHG.BLK` edit reached the applier (resolveBlockEdits was not run).";
+	"internal error: unresolved `SWAP.BLK` edit reached the applier (resolveBlockEdits was not run).";
 
 /** Delete hunk received a body row. */
-export const DELETE_TAKES_NO_BODY = "`DEL N..M` does not take body rows. Remove the body, or use `XCHG N..M:`.";
+export const DELETE_TAKES_NO_BODY = "`DEL N..M` does not take body rows. Remove the body, or use `SWAP N..M:`.";
 
 /** `delete_block N` hunk received a body row. */
-export const DELETE_BLOCK_TAKES_NO_BODY = "`DEL.BLK N` does not take body rows. Remove the body, or use `XCHG.BLK N:`.";
+export const DELETE_BLOCK_TAKES_NO_BODY = "`DEL.BLK N` does not take body rows. Remove the body, or use `SWAP.BLK N:`.";
 
 /** Insert hunk with no body. */
 export const EMPTY_INSERT = "`INS` needs at least one `+TEXT` body row.";
@@ -224,9 +224,9 @@ export type BlockOp = "replace" | "delete" | "insert_after";
  * see. Reject and point at both fixes.
  */
 export function blockSingleLineMessage(line: number, op: BlockOp): string {
-	const blockForm = op === "insert_after" ? "INS.BLK.POST" : op === "delete" ? "DEL.BLK" : "XCHG.BLK";
+	const blockForm = op === "insert_after" ? "INS.BLK.POST" : op === "delete" ? "DEL.BLK" : "SWAP.BLK";
 	const plainForm =
-		op === "insert_after" ? `INS.POST ${line}:` : op === "delete" ? `DEL ${line}` : `XCHG ${line}..${line}:`;
+		op === "insert_after" ? `INS.POST ${line}:` : op === "delete" ? `DEL ${line}` : `SWAP ${line}..${line}:`;
 	return (
 		`\`${blockForm} ${line}\` resolved a single-line block — line ${line} is a bare statement, not the opening line ` +
 		`of a multi-line construct. For that one line use \`${plainForm}\`; to act on an enclosing construct, anchor ${blockForm} ` +
diff --git a/packages/hashline/src/parser.ts b/packages/hashline/src/parser.ts
index bccf4bd24..c7dcc444d 100644
--- a/packages/hashline/src/parser.ts
+++ b/packages/hashline/src/parser.ts
@@ -52,33 +52,33 @@ function detectApplyPatchContamination(text: string, _hasPending: boolean): stri
 		return (
 			`apply_patch sentinel ${JSON.stringify(preview)} is not valid in hashline. ` +
 			"File sections start with `[path#HASH]` (no `Update File:` / `Add File:` keyword). " +
-			"Use `XCHG N..M:`, `DEL N..M`, or `INS.PRE|POST|HEAD|TAIL:` ops."
+			"Use `SWAP N..M:`, `DEL N..M`, or `INS.PRE|POST|HEAD|TAIL:` ops."
 		);
 	}
 	if (/^@@\s+[-+]?\d+,\d+\s+[-+]?\d+,\d+\s+@@/.test(trimmed)) {
 		return (
 			"unified-diff hunk header (`@@ -N,M +N,M @@`) is not valid in hashline. " +
-			"Use `XCHG N..M:`, `DEL N..M`, or `INS.PRE|POST|HEAD|TAIL:` ops."
+			"Use `SWAP N..M:`, `DEL N..M`, or `INS.PRE|POST|HEAD|TAIL:` ops."
 		);
 	}
 	if (trimmed.startsWith("@@")) {
 		const preview = trimmed.length > 48 ? `${trimmed.slice(0, 48)}…` : trimmed;
 		return (
 			`\`@@\`-bracketed hunk header ${JSON.stringify(preview)} is not valid in hashline. ` +
-			"Drop the `@@ ... @@` brackets and write a verb header such as `XCHG N..M:`."
+			"Drop the `@@ ... @@` brackets and write a verb header such as `SWAP N..M:`."
 		);
 	}
 	if (/^DEL\s+[1-9]\d*(?:\s*(?:\.\.|-|…|\s)\s*[1-9]\d*)?\s*:/.test(trimmed)) {
 		return "`DEL N..M` has no colon and no body. Remove the colon and body rows.";
 	}
 	if (/^[1-9]\d*\s*$/.test(trimmed)) {
-		return `hunk headers need a verb. Use \`XCHG ${trimmed}..${trimmed}:\` to replace, or \`DEL ${trimmed}\` to delete.`;
+		return `hunk headers need a verb. Use \`SWAP ${trimmed}..${trimmed}:\` to replace, or \`DEL ${trimmed}\` to delete.`;
 	}
 	const bareRange = /^([1-9]\d*)\s*[-. …]+\s*([1-9]\d*)\s*:?$/.exec(trimmed);
 	if (bareRange !== null) {
 		return (
 			`bare range hunk header ${JSON.stringify(trimmed)} is not valid. ` +
-			`Hunk headers need a verb: write \`XCHG ${bareRange[1]}..${bareRange[2]}:\` or \`DEL ${bareRange[1]}..${bareRange[2]}\`.`
+			`Hunk headers need a verb: write \`SWAP ${bareRange[1]}..${bareRange[2]}:\` or \`DEL ${bareRange[1]}..${bareRange[2]}\`.`
 		);
 	}
 	return null;
@@ -253,7 +253,7 @@ export class Executor {
 		if (text.trim().length === 0) return;
 		throw new Error(
 			`line ${lineNum}: payload line has no preceding hunk header. ` +
-				`Use \`XCHG N..M:\`, \`DEL N..M\`, or \`INS.PRE|POST|HEAD|TAIL:\` above the body. Got ${JSON.stringify(text)}.`,
+				`Use \`SWAP N..M:\`, \`DEL N..M\`, or \`INS.PRE|POST|HEAD|TAIL:\` above the body. Got ${JSON.stringify(text)}.`,
 		);
 	}
 
diff --git a/packages/hashline/src/prompt.md b/packages/hashline/src/prompt.md
index 166bbe5ea..a4cf6a4c0 100644
--- a/packages/hashline/src/prompt.md
+++ b/packages/hashline/src/prompt.md
@@ -5,8 +5,8 @@ Every file section starts with `[PATH#TAG]`. `TAG` is the 4-hex snapshot tag fro
 </headers>
 
 <ops>
-`XCHG N..M:` — replace original lines N..M with the body rows below. INCLUSIVE — line M is consumed too.
-`XCHG.BLK N:` — replace the whole syntactic block that BEGINS on line N; tree-sitter resolves the closing line. Body rows below.
+`SWAP N..M:` — replace original lines N..M with the body rows below. INCLUSIVE — line M is consumed too.
+`SWAP.BLK N:` — replace the whole syntactic block that BEGINS on line N; tree-sitter resolves the closing line. Body rows below.
 `DEL N..M` — delete original lines N..M. No body.
 `DEL.BLK N` — delete the whole syntactic block that BEGINS on line N.
 `INS.PRE N:` — insert the body rows immediately before line N.
@@ -14,7 +14,7 @@ Every file section starts with `[PATH#TAG]`. `TAG` is the 4-hex snapshot tag fro
 `INS.BLK.POST N:` — insert the body rows after the END of the block that BEGINS on line N — outside it, at sibling depth. To append inside a block, use `INS.POST`.
 `INS.HEAD:` — insert the body rows at the very start of the file.
 `INS.TAIL:` — insert the body rows at the very end of the file.
-Single line: `XCHG N..N:` / `DEL N`. The range is the ORIGINAL lines you touch; body length is irrelevant (replacing 1 line with 10 is still `XCHG N..N:`).
+Single line: `SWAP N..N:` / `DEL N`. The range is the ORIGINAL lines you touch; body length is irrelevant (replacing 1 line with 10 is still `SWAP N..N:`).
 </ops>
 
 <body-rows>
@@ -34,11 +34,11 @@ There is NO other body row kind. NEVER write `-old` or a bare/context line. To k
 - On a stale-tag rejection or any surprising result: STOP and re-`read` before further edits.
 - One hunk per range; the body is the final content, never an old/new pair.
 - Ranges cover ONLY lines whose content changes. Never widen over unchanged lines — a stale wide range shreds everything it spans.
-- Whole construct → `XCHG.BLK N` (tree-sitter resolves the end); lines inside it → `XCHG N..M`.
-- `XCHG.BLK N` resolves EXACTLY the node at N. Leading decorators/attributes/doc-comments are separate nodes: point N at the FIRST decorator to sweep both; standalone line-comments are never swept — use `XCHG N..M`.
-- Block ops (`XCHG.BLK`/`DEL.BLK`/`INS.BLK.POST`) anchor the OPENING line of a MULTI-LINE construct — never its closer, its last line, or a bare statement inside it. Anchoring a single statement resolves to ONE line and is REJECTED: use the plain op (`XCHG N..N` / `DEL N` / `INS.POST N`) for one line, or point N at the real opener. Saw the closer? Use plain `INS.POST M:`.
+- Whole construct → `SWAP.BLK N` (tree-sitter resolves the end); lines inside it → `SWAP N..M`.
+- `SWAP.BLK N` resolves EXACTLY the node at N. Leading decorators/attributes/doc-comments are separate nodes: point N at the FIRST decorator to sweep both; standalone line-comments are never swept — use `SWAP N..M`.
+- Block ops (`SWAP.BLK`/`DEL.BLK`/`INS.BLK.POST`) anchor the OPENING line of a MULTI-LINE construct — never its closer, its last line, or a bare statement inside it. Anchoring a single statement resolves to ONE line and is REJECTED: use the plain op (`SWAP N..N` / `DEL N` / `INS.POST N`) for one line, or point N at the real opener. Saw the closer? Use plain `INS.POST M:`.
 - Non-adjacent changes = separate hunks; untouched lines stay out of every range.
-- Pure additions use `INS.PRE` / `INS.POST` / `INS.HEAD` / `INS.TAIL`, never a widened `XCHG` — retyped keepers are exactly what gets dropped. A multi-line `XCHG` whose body restates the line just outside the range is auto-dropped as an off-by-one keeper (with a warning), but issue the payload as the final content for the range only and never lean on the repair.
+- Pure additions use `INS.PRE` / `INS.POST` / `INS.HEAD` / `INS.TAIL`, never a widened `SWAP` — retyped keepers are exactly what gets dropped. A multi-line `SWAP` whose body restates the line just outside the range is auto-dropped as an off-by-one keeper (with a warning), but issue the payload as the final content for the range only and never lean on the repair.
 - NEVER format/restyle code with this tool; run the project formatter instead.
 </rules>
 
@@ -62,7 +62,7 @@ INS.POST 1:
 Replace line 2 with two lines:
 ```
 [greet.py#A1B2]
-XCHG 2..2:
+SWAP 2..2:
 +    greeting = "Hi"
 +    msg = f"{greeting}, {name}"
 ```
@@ -82,18 +82,18 @@ INS.TAIL:
 +greet("everyone")
 ```
 
-Replace the whole `greet` function block — `XCHG.BLK 1:` resolves lines 1–3 (the `def` header through `print(msg)`); line 4 is a separate statement and stays:
+Replace the whole `greet` function block — `SWAP.BLK 1:` resolves lines 1–3 (the `def` header through `print(msg)`); line 4 is a separate statement and stays:
 ```
 [greet.py#A1B2]
-XCHG.BLK 1:
+SWAP.BLK 1:
 +def greet(name):
 +    print(f"Hello, {name}")
 ```
 
-A decorator or doc-comment is a SEPARATE block — `XCHG.BLK` on the `def`/`fn` line keeps it. Point N at the decorator to take both; here line 1 is `@cache`, so anchoring on the `def` (line 2) would resolve only the function and orphan `@cache`:
+A decorator or doc-comment is a SEPARATE block — `SWAP.BLK` on the `def`/`fn` line keeps it. Point N at the decorator to take both; here line 1 is `@cache`, so anchoring on the `def` (line 2) would resolve only the function and orphan `@cache`:
 ```
 [svc.py#C3D4]
-XCHG.BLK 1:
+SWAP.BLK 1:
 +@cache
 +def load(key):
 +    return store[key]
@@ -101,25 +101,25 @@ XCHG.BLK 1:
 </example>
 
 <anti-patterns>
-# WRONG — empty `XCHG` to delete. RIGHT: DEL 4
-XCHG 4..4:
+# WRONG — empty `SWAP` to delete. RIGHT: DEL 4
+SWAP 4..4:
 
-# WRONG — range describes post-edit size. RIGHT: XCHG 1..1: (body length is irrelevant)
-XCHG 1..2:
+# WRONG — range describes post-edit size. RIGHT: SWAP 1..1: (body length is irrelevant)
+SWAP 1..2:
 +def greet(name):
 
 # WRONG — `-` rows / bare context lines do not exist. The range deletes; the body is only the new content.
-XCHG 3..3:
+SWAP 3..3:
     msg = "Hello, " + name
 -   print(msg)
 +   return msg
 # RIGHT
-XCHG 3..3:
+SWAP 3..3:
 +   return msg
 
-# WRONG — a pure insertion done as a widened `XCHG`: you only want to add one line after 2,
+# WRONG — a pure insertion done as a widened `SWAP`: you only want to add one line after 2,
 # but you replace 2..4, retype the keepers in the body, and drop one (here line 4, `greet("world")`).
-XCHG 2..4:
+SWAP 2..4:
 +    msg = "Hello, " + name
 +    extra = compute(name)
 +    print(msg)
@@ -138,6 +138,6 @@ INS.POST 3:
 <critical>
 If you remember nothing else:
 1. RE-GROUND AFTER EVERY EDIT. Every apply mints a fresh `#TAG` and renumbers — take the next edit's numbers from the edit response or a fresh `read`. Stale tag or surprise? STOP, re-`read`.
-2. RANGES ARE TIGHT. Cover only lines that change; a stale wide range shreds everything it spans. Whole construct → `XCHG.BLK N`.
+2. RANGES ARE TIGHT. Cover only lines that change; a stale wide range shreds everything it spans. Whole construct → `SWAP.BLK N`.
 3. THE BODY IS THE FINAL CONTENT. Only `+TEXT` rows; never `-old`/context lines. The range does the deleting.
 </critical>
diff --git a/packages/hashline/test/block.test.ts b/packages/hashline/test/block.test.ts
index 497907399..a6eec72f3 100644
--- a/packages/hashline/test/block.test.ts
+++ b/packages/hashline/test/block.test.ts
@@ -31,9 +31,9 @@ function normalizeEdits(edits: readonly Edit[]): unknown[] {
 	});
 }
 
-describe("XCHG.BLK parsing", () => {
-	it("parses `XCHG.BLK N:` into a single deferred block edit", () => {
-		const { edits } = parsePatch("XCHG.BLK 2:\n+A\n+B");
+describe("SWAP.BLK parsing", () => {
+	it("parses `SWAP.BLK N:` into a single deferred block edit", () => {
+		const { edits } = parsePatch("SWAP.BLK 2:\n+A\n+B");
 
 		expect(edits).toHaveLength(1);
 		const edit = edits[0];
@@ -43,52 +43,52 @@ describe("XCHG.BLK parsing", () => {
 		expect(edit.payloads).toEqual(["A", "B"]);
 	});
 
-	it("still parses a literal `XCHG N..M:` range (distinct from `XCHG.BLK`)", () => {
-		const { edits } = parsePatch("XCHG 2..3:\n+A");
+	it("still parses a literal `SWAP N..M:` range (distinct from `SWAP.BLK`)", () => {
+		const { edits } = parsePatch("SWAP 2..3:\n+A");
 		expect(edits.some(edit => edit.kind === "block")).toBe(false);
 		expect(edits.some(edit => edit.kind === "delete")).toBe(true);
 	});
 
-	it("rejects a `XCHG.BLK N:` hunk with no body row", () => {
-		expect(() => parsePatch("XCHG.BLK 2:")).toThrow("`XCHG.BLK N:` needs at least one");
+	it("rejects a `SWAP.BLK N:` hunk with no body row", () => {
+		expect(() => parsePatch("SWAP.BLK 2:")).toThrow("`SWAP.BLK N:` needs at least one");
 	});
 });
 
 describe("resolveBlockEdits", () => {
-	it("expands a block edit exactly like the equivalent `XCHG start..end:`", () => {
-		const blockEdits = parsePatch("XCHG.BLK 2:\n+A\n+B").edits;
+	it("expands a block edit exactly like the equivalent `SWAP start..end:`", () => {
+		const blockEdits = parsePatch("SWAP.BLK 2:\n+A\n+B").edits;
 		const resolved = resolveBlockEdits(blockEdits, "ignored", PATH, stubResolver);
-		const replaceEdits = parsePatch("XCHG 2..3:\n+A\n+B").edits;
+		const replaceEdits = parsePatch("SWAP 2..3:\n+A\n+B").edits;
 
 		expect(resolved.some(edit => edit.kind === "block")).toBe(false);
 		expect(normalizeEdits(resolved)).toEqual(normalizeEdits(replaceEdits));
 	});
 
 	it("returns the input untouched when there are no block edits (fast path)", () => {
-		const edits = parsePatch("XCHG 1..1:\n+X").edits;
+		const edits = parsePatch("SWAP 1..1:\n+X").edits;
 		expect(resolveBlockEdits(edits, "ignored", PATH, stubResolver)).toBe(edits);
 	});
 
 	it("throws (default) when no resolver is wired", () => {
-		const edits = parsePatch("XCHG.BLK 2:\n+X").edits;
+		const edits = parsePatch("SWAP.BLK 2:\n+X").edits;
 		expect(() => resolveBlockEdits(edits, "ignored", PATH, undefined)).toThrow("not available here");
 	});
 
 	it("drops an unresolvable block edit in `drop` mode", () => {
-		const edits = parsePatch("XCHG.BLK 2:\n+X").edits;
+		const edits = parsePatch("SWAP.BLK 2:\n+X").edits;
 		const resolved = resolveBlockEdits(edits, "ignored", PATH, () => null, { onUnresolved: "drop" });
 		expect(resolved).toHaveLength(0);
 	});
 
 	it("throws a block-unresolved error in `throw` mode when the resolver returns null", () => {
-		const edits = parsePatch("XCHG.BLK 7:\n+X").edits;
+		const edits = parsePatch("SWAP.BLK 7:\n+X").edits;
 		expect(() => resolveBlockEdits(edits, "ignored", PATH, () => null)).toThrow(
 			"could not resolve a syntactic block beginning on line 7",
 		);
 	});
 
 	it("includes a nearby-context preview in the block-unresolved error", () => {
-		const edits = parsePatch("XCHG.BLK 3:\n+X").edits;
+		const edits = parsePatch("SWAP.BLK 3:\n+X").edits;
 		const text = "alpha\nbravo\ncharlie\ndelta\necho\nfoxtrot";
 		let error: Error | undefined;
 		try {
@@ -105,7 +105,7 @@ describe("resolveBlockEdits", () => {
 	});
 
 	it("omits the context preview when the anchor line is out of range", () => {
-		const edits = parsePatch("XCHG.BLK 9:\n+X").edits;
+		const edits = parsePatch("SWAP.BLK 9:\n+X").edits;
 		let error: Error | undefined;
 		try {
 			resolveBlockEdits(edits, "only\ntwo", PATH, () => null);
@@ -119,7 +119,7 @@ describe("resolveBlockEdits", () => {
 	it("fires onResolved with the resolved span for replace and delete blocks", () => {
 		const seen: BlockResolution[] = [];
 		// stubResolver maps line N → span [N, N+1].
-		resolveBlockEdits(parsePatch("XCHG.BLK 2:\n+A\n+B").edits, "ignored", PATH, stubResolver, {
+		resolveBlockEdits(parsePatch("SWAP.BLK 2:\n+A\n+B").edits, "ignored", PATH, stubResolver, {
 			onResolved: resolution => seen.push(resolution),
 		});
 		resolveBlockEdits(parsePatch("DEL.BLK 5").edits, "ignored", PATH, stubResolver, {
@@ -134,7 +134,7 @@ describe("resolveBlockEdits", () => {
 
 	it("does not fire onResolved for a dropped unresolvable block", () => {
 		const seen: BlockResolution[] = [];
-		resolveBlockEdits(parsePatch("XCHG.BLK 2:\n+X").edits, "ignored", PATH, () => null, {
+		resolveBlockEdits(parsePatch("SWAP.BLK 2:\n+X").edits, "ignored", PATH, () => null, {
 			onUnresolved: "drop",
 			onResolved: resolution => seen.push(resolution),
 		});
@@ -147,8 +147,8 @@ describe("resolveBlockEdits", () => {
 	// plain form rather than silently landing a body in the wrong scope.
 	const singleLineResolver: BlockResolver = ({ line }): BlockSpan => ({ start: line, end: line });
 
-	it("rejects a `XCHG.BLK` that resolves to a single line", () => {
-		const edits = parsePatch("XCHG.BLK 2:\n+X").edits;
+	it("rejects a `SWAP.BLK` that resolves to a single line", () => {
+		const edits = parsePatch("SWAP.BLK 2:\n+X").edits;
 		expect(() => resolveBlockEdits(edits, "a\nb\nc", PATH, singleLineResolver)).toThrow(
 			/resolved a single-line block/,
 		);
@@ -160,7 +160,7 @@ describe("resolveBlockEdits", () => {
 	});
 
 	it("drops a single-line block resolution on the lenient preview path", () => {
-		const edits = parsePatch("XCHG.BLK 2:\n+X").edits;
+		const edits = parsePatch("SWAP.BLK 2:\n+X").edits;
 		const resolved = resolveBlockEdits(edits, "a\nb\nc", PATH, singleLineResolver, { onUnresolved: "drop" });
 		expect(resolved).toHaveLength(0);
 	});
@@ -170,8 +170,8 @@ describe("PatchSection.applyTo / applyPartialTo with block edits", () => {
 	const text = "function x() {\n  if (y) {\n  }\n}\n";
 
 	it("applyTo resolves a block edit and matches the equivalent `replace`", () => {
-		const blockSection = Patch.parseSingle(`[${PATH}#1A2B]\nXCHG.BLK 2:\n+  if (y || z) {\n+  }`);
-		const replaceSection = Patch.parseSingle(`[${PATH}#1A2B]\nXCHG 2..3:\n+  if (y || z) {\n+  }`);
+		const blockSection = Patch.parseSingle(`[${PATH}#1A2B]\nSWAP.BLK 2:\n+  if (y || z) {\n+  }`);
+		const replaceSection = Patch.parseSingle(`[${PATH}#1A2B]\nSWAP 2..3:\n+  if (y || z) {\n+  }`);
 
 		const blockResult = blockSection.applyTo(text, stubResolver);
 		const replaceResult = replaceSection.applyTo(text);
@@ -181,12 +181,12 @@ describe("PatchSection.applyTo / applyPartialTo with block edits", () => {
 	});
 
 	it("applyTo throws when a block edit has no resolver", () => {
-		const section = Patch.parseSingle(`[${PATH}#1A2B]\nXCHG.BLK 2:\n+X`);
+		const section = Patch.parseSingle(`[${PATH}#1A2B]\nSWAP.BLK 2:\n+X`);
 		expect(() => section.applyTo(text)).toThrow("no block resolver configured");
 	});
 
 	it("applyPartialTo drops an unresolvable block edit instead of throwing", () => {
-		const section = Patch.parseSingle(`[${PATH}#1A2B]\nXCHG.BLK 2:\n+X`);
+		const section = Patch.parseSingle(`[${PATH}#1A2B]\nSWAP.BLK 2:\n+X`);
 		// No resolver → drop. The lone block edit vanishes, so the text is unchanged.
 		const result = section.applyPartialTo(text);
 		expect(result.text).toBe(text);
@@ -202,7 +202,7 @@ describe("Patcher with a block resolver", () => {
 		const tag = snapshots.record(PATH, text);
 		const patcher = new Patcher({ fs, snapshots, blockResolver: stubResolver });
 
-		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG.BLK 2:\n+  if (y || z) {\n+  }`));
+		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP.BLK 2:\n+  if (y || z) {\n+  }`));
 
 		expect(result.sections[0]?.op).toBe("update");
 		expect(fs.get(PATH)).toBe("function x() {\n  if (y || z) {\n  }\n}\n");
@@ -214,7 +214,7 @@ describe("Patcher with a block resolver", () => {
 		const tag = snapshots.record(PATH, text);
 		const patcher = new Patcher({ fs, snapshots, blockResolver: stubResolver });
 
-		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG.BLK 2:\n+  if (y || z) {\n+  }`));
+		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP.BLK 2:\n+  if (y || z) {\n+  }`));
 
 		expect(result.sections[0]?.blockResolutions).toEqual([{ anchorLine: 2, start: 2, end: 3, op: "replace" }]);
 	});
@@ -230,7 +230,7 @@ describe("Patcher with a block resolver", () => {
 
 		// `block 2` resolves against the SNAPSHOT → span [2,3] → replace
 		// "line1","line2"; recovery 3-way-merges the change onto the live file.
-		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG.BLK 2:\n+NEW`));
+		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP.BLK 2:\n+NEW`));
 
 		expect(result.sections[0]?.op).toBe("update");
 		expect(fs.get(PATH)).toBe("line0\nNEW\nline3\nline4\nline5\n");
@@ -248,7 +248,7 @@ describe("Patcher with a block resolver", () => {
 		const bogus = live === "FFFF" ? "0000" : "FFFF";
 		const patcher = new Patcher({ fs, snapshots, blockResolver: stubResolver });
 
-		await expect(patcher.apply(Patch.parse(`[${PATH}#${bogus}]\nXCHG.BLK 2:\n+NEW`))).rejects.toBeInstanceOf(
+		await expect(patcher.apply(Patch.parse(`[${PATH}#${bogus}]\nSWAP.BLK 2:\n+NEW`))).rejects.toBeInstanceOf(
 			MismatchError,
 		);
 		expect(fs.get(PATH)).toBe(liveText);
@@ -260,7 +260,7 @@ describe("Patcher with a block resolver", () => {
 		const tag = snapshots.record(PATH, text);
 		const patcher = new Patcher({ fs, snapshots, blockResolver: () => null });
 
-		await expect(patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG.BLK 2:\n+X`))).rejects.toThrow(
+		await expect(patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP.BLK 2:\n+X`))).rejects.toThrow(
 			"could not resolve a syntactic block",
 		);
 		expect(fs.get(PATH)).toBe(text);
diff --git a/packages/hashline/test/boundary-repair.test.ts b/packages/hashline/test/boundary-repair.test.ts
index 8a50b8c68..c29c6be0a 100644
--- a/packages/hashline/test/boundary-repair.test.ts
+++ b/packages/hashline/test/boundary-repair.test.ts
@@ -35,7 +35,7 @@ describe("boundary-balance repair", () => {
 		// Range 7..16 = `const …` through the first `/>`; payload restates the
 		// `</>` + `);` that survive at lines 17-18.
 		const diff = [
-			"XCHG 7..16:",
+			"SWAP 7..16:",
 			"+\treturn (",
 			"+\t\t<>",
 			"+\t\t\t<Composition",
@@ -62,7 +62,7 @@ describe("boundary-balance repair", () => {
 		const file = ["it('a', () => {", "\tsetup();", "\trun();", "});", "after();"].join("\n");
 		// `replace 2..3:` replaces the two body lines but the payload also restates the
 		// `});` at line 4, which survives — a duplicate close.
-		const diff = ["XCHG 2..3:", "+\tsetup2();", "+\trun2();", "+});"].join("\n");
+		const diff = ["SWAP 2..3:", "+\tsetup2();", "+\trun2();", "+});"].join("\n");
 		const { text, warnings } = apply(file, diff);
 		expect(text).toBe(["it('a', () => {", "\tsetup2();", "\trun2();", "});", "after();"].join("\n"));
 		expect(warnings.some(w => /delimiter-balance/.test(w))).toBe(true);
@@ -86,7 +86,7 @@ describe("boundary-balance repair", () => {
 		// `replace 4..6:` covers the params + return-type line, but the payload also
 		// restates the `planRender(` at line 3, which survives — a duplicate open.
 		const diff = [
-			"XCHG 4..6:",
+			"SWAP 4..6:",
 			"+\tplanRender(",
 			"+\t\ta: string[],",
 			"+\t\tb: boolean,",
@@ -117,7 +117,7 @@ describe("boundary-balance repair", () => {
 		const file = ["if (a) {", "\tfoo();", "}", "bar();"].join("\n");
 		// Payload duplicates `if (a) {` but is net +2 braces; dropping the one
 		// opener cannot zero the delta, so nothing is repaired.
-		const diff = ["XCHG 2..2:", "+if (a) {", "+\tif (b) {", "+\t\tfoo();"].join("\n");
+		const diff = ["SWAP 2..2:", "+if (a) {", "+\tif (b) {", "+\t\tfoo();"].join("\n");
 		const { text, warnings } = apply(file, diff);
 		expect(text).toBe(["if (a) {", "if (a) {", "\tif (b) {", "\t\tfoo();", "}", "bar();"].join("\n"));
 		expect(warnings).toHaveLength(0);
@@ -128,7 +128,7 @@ describe("boundary-balance repair", () => {
 		const file = ["const handlers = {", "\ta() {", "\t\treturn 1;", "\t},", "};"].join("\n");
 		// `replace 5..5:` is the final `};`. Model inserts a new method but forgets to
 		// restate `};`; sparing it keeps the object literal balanced.
-		const diff = ["XCHG 5..5:", "+\tb() {", "+\t\treturn 2;", "+\t},"].join("\n");
+		const diff = ["SWAP 5..5:", "+\tb() {", "+\t\treturn 2;", "+\t},"].join("\n");
 		const { text, warnings } = apply(file, diff);
 		expect(text).toBe(
 			["const handlers = {", "\ta() {", "\t\treturn 1;", "\t},", "\tb() {", "\t\treturn 2;", "\t},", "};"].join(
@@ -143,7 +143,7 @@ describe("boundary-balance repair", () => {
 	// keeping the deleted suffix would duplicate the closer outside the payload.
 	it("does not spare a deleted closing line that the payload already restates", () => {
 		const file = ["class Foo {", "\tok();", "\t}", "}"].join("\n");
-		const diff = ["XCHG 1..4:", "+class Foo {", "+\tok();", "+}"].join("\n");
+		const diff = ["SWAP 1..4:", "+class Foo {", "+\tok();", "+}"].join("\n");
 		const { text, warnings } = apply(file, diff);
 
 		expect(text).toBe(["class Foo {", "\tok();", "}"].join("\n"));
@@ -159,7 +159,7 @@ describe("boundary-balance repair", () => {
 			"\tprint_status()",
 		].join("\n");
 		const diff = [
-			"XCHG 2..3:",
+			"SWAP 2..3:",
 			"+func _cmd_travel_homeworld():",
 			"+\tvar destination = find_homeworld()",
 			"+\ttravel_to(destination)",
@@ -183,7 +183,7 @@ describe("boundary-balance repair", () => {
 
 	it("preserves payloads where multi-line boundary echoes cover every line", () => {
 		const file = ["A", "B", "old", "C", "D"].join("\n");
-		const diff = ["XCHG 3..3:", "+A", "+B", "+C", "+D"].join("\n");
+		const diff = ["SWAP 3..3:", "+A", "+B", "+C", "+D"].join("\n");
 
 		const { text, warnings } = apply(file, diff);
 
@@ -193,7 +193,7 @@ describe("boundary-balance repair", () => {
 
 	it("preserves payloads made only of lines matching both replacement neighbors", () => {
 		const file = ["a", "old", "c"].join("\n");
-		const diff = ["XCHG 2..2:", "+a", "+c"].join("\n");
+		const diff = ["SWAP 2..2:", "+a", "+c"].join("\n");
 
 		const { text, warnings } = apply(file, diff);
 
@@ -209,7 +209,7 @@ describe("boundary-balance repair", () => {
 		// Payload deliberately opens with the same bare `}` that sits above the
 		// range and closes with the same `}` that sits below it; the payload is
 		// internally balanced (delta 0) while the dropped edges sum to -2 braces.
-		const diff = ["XCHG 2..2:", "+}", "+if (a) {", "+if (b) {", "+x();", "+}"].join("\n");
+		const diff = ["SWAP 2..2:", "+}", "+if (a) {", "+if (b) {", "+x();", "+}"].join("\n");
 
 		const { text, warnings } = apply(file, diff);
 
@@ -221,7 +221,7 @@ describe("boundary-balance repair", () => {
 	// (opener + closer) that duplicate the surviving neighbors are dropped.
 	it("still drops a balance-neutral wrapper echo", () => {
 		const file = ["function f() {", "old();", "}"].join("\n");
-		const diff = ["XCHG 2..2:", "+function f() {", "+fresh();", "+}"].join("\n");
+		const diff = ["SWAP 2..2:", "+function f() {", "+fresh();", "+}"].join("\n");
 
 		const { text, warnings } = apply(file, diff);
 
@@ -235,7 +235,7 @@ describe("boundary-balance repair", () => {
 		const file = ["foo();", "bar();", "bar();", "baz();"].join("\n");
 		// Replace line 2 with two balanced statements; the tail `bar();` equals
 		// the surviving line 3 but the payload is balanced — must NOT be dropped.
-		const diff = ["XCHG 2..2:", "+qux();", "+bar();"].join("\n");
+		const diff = ["SWAP 2..2:", "+qux();", "+bar();"].join("\n");
 		const { text, warnings } = apply(file, diff);
 		expect(text).toBe(["foo();", "qux();", "bar();", "bar();", "baz();"].join("\n"));
 		expect(warnings).toHaveLength(0);
@@ -245,7 +245,7 @@ describe("boundary-balance repair", () => {
 	// could discard intended content, and it does not break syntax.
 	it("does not drop a balance-neutral duplicated statement", () => {
 		const file = ["a = 1;", "b = 2;", "c = 3;"].join("\n");
-		const diff = ["XCHG 1..1:", "+a = 1;", "+b = 2;"].join("\n");
+		const diff = ["SWAP 1..1:", "+a = 1;", "+b = 2;"].join("\n");
 		const { text, warnings } = apply(file, diff);
 		expect(text).toBe(["a = 1;", "b = 2;", "b = 2;", "c = 3;"].join("\n"));
 		expect(warnings).toHaveLength(0);
@@ -254,7 +254,7 @@ describe("boundary-balance repair", () => {
 	// Brackets inside strings must not trigger a spurious balance mismatch.
 	it("ignores brackets inside string literals", () => {
 		const file = ['const a = "}";', 'const b = "x";', 'const c = "y";'].join("\n");
-		const diff = ["XCHG 2..2:", '+const b = "}}}";'].join("\n");
+		const diff = ["SWAP 2..2:", '+const b = "}}}";'].join("\n");
 		const { text, warnings } = apply(file, diff);
 		expect(text).toBe(['const a = "}";', 'const b = "}}}";', 'const c = "y";'].join("\n"));
 		expect(warnings).toHaveLength(0);
@@ -265,7 +265,7 @@ describe("boundary-balance repair", () => {
 	// the range was one line short of the `const changedFiles` it retyped.
 	it("drops a one-sided trailing keeper echo in a multi-line rewrite", () => {
 		const file = ["function f() {", "  a();", "  b();", "  const out = [];", "  return out;", "}"].join("\n");
-		const diff = ["XCHG 2..3:", "+  a2();", "+  b2();", "+  const out = [];"].join("\n");
+		const diff = ["SWAP 2..3:", "+  a2();", "+  b2();", "+  const out = [];"].join("\n");
 		const { text, warnings } = apply(file, diff);
 		expect(text).toBe(["function f() {", "  a2();", "  b2();", "  const out = [];", "  return out;", "}"].join("\n"));
 		expect(warnings.some(warning => /boundary echo/.test(warning))).toBe(true);
@@ -275,7 +275,7 @@ describe("boundary-balance repair", () => {
 	// the multi-line range (range one line low instead of one short).
 	it("drops a one-sided leading keeper echo in a multi-line rewrite", () => {
 		const file = ["setup();", "a();", "b();", "c();"].join("\n");
-		const diff = ["XCHG 3..4:", "+a();", "+B();", "+C();"].join("\n");
+		const diff = ["SWAP 3..4:", "+a();", "+B();", "+C();"].join("\n");
 		const { text, warnings } = apply(file, diff);
 		expect(text).toBe(["setup();", "a();", "B();", "C();"].join("\n"));
 		expect(warnings.some(warning => /boundary echo/.test(warning))).toBe(true);
@@ -317,7 +317,7 @@ describe("boundary-balance repair through stale-snapshot recovery", () => {
 
 		// `replace 4..5:` replaces the body lines but the payload also restates the `});`
 		// that survives at line 6 — the duplicate-closer mistake.
-		const { edits } = parsePatch(["XCHG 4..5:", "+\tsetup2();", "+\trun2();", "+});"].join("\n"));
+		const { edits } = parsePatch(["SWAP 4..5:", "+\tsetup2();", "+\trun2();", "+});"].join("\n"));
 		const recovered = new Recovery(store).tryRecover({ path: PATH, currentText, fileHash, edits });
 
 		expect(recovered).not.toBeNull();
diff --git a/packages/hashline/test/core-contracts.test.ts b/packages/hashline/test/core-contracts.test.ts
index 14be3810f..22b090049 100644
--- a/packages/hashline/test/core-contracts.test.ts
+++ b/packages/hashline/test/core-contracts.test.ts
@@ -21,7 +21,7 @@ function tag(line: number): string {
 }
 
 function sameLineRange(anchor: string): string {
-	return `XCHG ${anchor}..${anchor}:`;
+	return `SWAP ${anchor}..${anchor}:`;
 }
 
 function applyDiff(content: string, diff: string): string {
@@ -123,14 +123,14 @@ describe("hashline parser — range-anchor contracts", () => {
 	});
 
 	it("strips copied read-output prefixes only inside pasted bare body rows", () => {
-		const diff = `XCHG ${tag(2)}..${tag(4)}:\n${repl("line one")}\n${tag(3)}:line two`;
+		const diff = `SWAP ${tag(2)}..${tag(4)}:\n${repl("line one")}\n${tag(3)}:line two`;
 		const { edits, warnings } = parsePatch(diff);
 		expect(applyEdits("aaa\nbbb\nccc\nddd\neee", edits).text).toBe("aaa\nline one\nline two\neee");
 		expect(warnings.some(w => /Auto-prefixed bare body row/.test(w))).toBe(true);
 	});
 
 	it("rejects overlapping replacement ranges", () => {
-		const diff = `XCHG ${tag(2)}..${tag(4)}:\n${repl("NEW1")}\nXCHG ${tag(3)}..${tag(5)}:\n${repl("NEW2")}`;
+		const diff = `SWAP ${tag(2)}..${tag(4)}:\n${repl("NEW1")}\nSWAP ${tag(3)}..${tag(5)}:\n${repl("NEW2")}`;
 		expect(() => parsePatch(diff).edits).toThrow(/anchor line 3 is already targeted by another hunk on line 1/);
 	});
 
@@ -247,7 +247,7 @@ describe("Recovery", () => {
 			path: filePath,
 			currentText,
 			tag: v0Tag,
-			edits: parsePatch(`XCHG 10..10:\n${repl("L10-EDITED")}`).edits,
+			edits: parsePatch(`SWAP 10..10:\n${repl("L10-EDITED")}`).edits,
 		});
 
 		expect(recovered).not.toBeNull();
@@ -289,7 +289,7 @@ describe("hashline parser — delete and blank payload semantics", () => {
 		expect(applyDiff("line1\nline2\nline3\nline4\n", splitHashlineInput("[a.ts]\nDEL 2..3\n").diff)).toBe(
 			"line1\nline4\n",
 		);
-		expect(applyDiff("line1\nline2\nline3\n", splitHashlineInput("[a.ts]\nXCHG 2..2:\n").diff)).toBe(
+		expect(applyDiff("line1\nline2\nline3\n", splitHashlineInput("[a.ts]\nSWAP 2..2:\n").diff)).toBe(
 			"line1\nline3\n",
 		);
 	});
@@ -301,10 +301,10 @@ describe("hashline parser — delete and blank payload semantics", () => {
 
 	it("preserves explicit blank replacement rows", () => {
 		const text = "a\nb\nc\nd\ne\n";
-		const ops = `[a.ts]\nXCHG 2..2:\n${repl("")}\n${repl("")}\nXCHG 4..4:\n${repl("D")}\n`;
+		const ops = `[a.ts]\nSWAP 2..2:\n${repl("")}\n${repl("")}\nSWAP 4..4:\n${repl("D")}\n`;
 		expect(applyDiff(text, splitHashlineInput(ops).diff)).toBe("a\n\n\nc\nD\ne\n");
 
-		const embedded = `[a.ts]\nXCHG 2..2:\n${repl("first")}\n${repl("")}\n${repl("second")}\n`;
+		const embedded = `[a.ts]\nSWAP 2..2:\n${repl("first")}\n${repl("")}\n${repl("second")}\n`;
 		expect(applyDiff("a\nb\nc\n", splitHashlineInput(embedded).diff)).toBe("a\nfirst\n\nsecond\nc\n");
 	});
 });
diff --git a/packages/hashline/test/format-v2.test.ts b/packages/hashline/test/format-v2.test.ts
index 4e87b8c33..b541e85ba 100644
--- a/packages/hashline/test/format-v2.test.ts
+++ b/packages/hashline/test/format-v2.test.ts
@@ -8,7 +8,7 @@ function applyPatch(text: string, diff: string): string {
 describe("hashline format v4", () => {
 	it("replaces a concrete range with literal body rows in textual order", () => {
 		const text = "a\nb\nc";
-		const diff = ["XCHG 2..2:", "+before", "+after"].join("\n");
+		const diff = ["SWAP 2..2:", "+before", "+after"].join("\n");
 
 		expect(applyPatch(text, diff)).toBe("a\nbefore\nafter\nc");
 	});
@@ -37,7 +37,7 @@ describe("hashline format v4", () => {
 
 	it("treats an empty replace hunk as a delete and still rejects empty inserts", () => {
 		const text = "a\nb\nc";
-		expect(applyPatch(text, "XCHG 2..2:")).toBe("a\nc");
+		expect(applyPatch(text, "SWAP 2..2:")).toBe("a\nc");
 		expect(() => parsePatch("INS.HEAD:")).toThrow(/needs at least one/);
 	});
 
@@ -47,8 +47,8 @@ describe("hashline format v4", () => {
 
 	it("auto-pipes bare body rows as literal text", () => {
 		const text = "a\nb\nc";
-		expect(applyPatch(text, "XCHG 2..2:\nraw")).toBe("a\nraw\nc");
-		const { warnings } = parsePatch("XCHG 2..2:\nraw");
+		expect(applyPatch(text, "SWAP 2..2:\nraw")).toBe("a\nraw\nc");
+		const { warnings } = parsePatch("SWAP 2..2:\nraw");
 		expect(warnings.some(w => /Auto-prefixed bare body row/.test(w))).toBe(true);
 	});
 
@@ -56,7 +56,7 @@ describe("hashline format v4", () => {
 		const text = "a\nb\nc";
 		// Without this fix, "3:text" becomes literal "3:text" in the file.
 		// With the fix, the "3:" prefix is stripped, yielding just "text".
-		const { edits, warnings } = parsePatch("XCHG 2..2:\n3:replaced");
+		const { edits, warnings } = parsePatch("SWAP 2..2:\n3:replaced");
 		expect(applyEdits(text, edits).text).toBe("a\nreplaced\nc");
 		expect(warnings.some(w => /Auto-prefixed bare body row/.test(w))).toBe(true);
 	});
@@ -78,7 +78,7 @@ describe("hashline format v4", () => {
 	});
 
 	it("treats a replace range ending at the trailing sentinel as ending at the last real line", () => {
-		const edits = parsePatch("XCHG 2..3:\n+B").edits;
+		const edits = parsePatch("SWAP 2..3:\n+B").edits;
 		expect(applyEdits("a\nb\n", edits).text).toBe("a\nB\n");
 	});
 
@@ -94,12 +94,12 @@ describe("hashline format v4", () => {
 	});
 
 	it("does not flush a trailing streaming pending empty replace hunk", () => {
-		const result = parsePatchStreaming("XCHG 5..5:\n");
+		const result = parsePatchStreaming("SWAP 5..5:\n");
 		expect(result.edits).toEqual([]);
 	});
 
 	it("flushes a streaming empty replace hunk when another hunk starts", () => {
-		const result = parsePatchStreaming("XCHG 2..2:\nINS.TAIL:\n");
+		const result = parsePatchStreaming("SWAP 2..2:\nINS.TAIL:\n");
 		expect(result.edits).toEqual([{ kind: "delete", anchor: { line: 2 }, lineNum: 1, index: 0 }]);
 	});
 });
diff --git a/packages/hashline/test/landing-shift.test.ts b/packages/hashline/test/landing-shift.test.ts
index 496f893be..b1f9eb287 100644
--- a/packages/hashline/test/landing-shift.test.ts
+++ b/packages/hashline/test/landing-shift.test.ts
@@ -207,7 +207,7 @@ describe("insert-after-block inward landing shift", () => {
 	it("refuses to cross a closer targeted by another hunk", () => {
 		const resolver: BlockResolver = (): BlockSpan => ({ start: 1, end: 5 });
 		const text = ["foo(() => {", "    bar(() => {", "        x();", "    });", "});", ""].join("\n");
-		const section = Patch.parseSingle("[x.ts#1A2B]\nXCHG 4..4:\n+    }); // bar\nINS.BLK.POST 1:\n+        y();");
+		const section = Patch.parseSingle("[x.ts#1A2B]\nSWAP 4..4:\n+    }); // bar\nINS.BLK.POST 1:\n+        y();");
 
 		const result = section.applyTo(text, resolver);
 
diff --git a/packages/hashline/test/leniency.test.ts b/packages/hashline/test/leniency.test.ts
index 7360551d4..fde068fc7 100644
--- a/packages/hashline/test/leniency.test.ts
+++ b/packages/hashline/test/leniency.test.ts
@@ -9,7 +9,7 @@ const FILE = "a\nb\nc\nd\ne";
 
 describe("hashline section headers", () => {
 	it("accepts paths with spaces in anchored section headers", () => {
-		const section = Patch.parseSingle("[dir with spaces/file.ts#1a2b]\nXCHG 1..1:\n+after");
+		const section = Patch.parseSingle("[dir with spaces/file.ts#1a2b]\nSWAP 1..1:\n+after");
 
 		expect(section.path).toBe("dir with spaces/file.ts");
 		expect(section.fileHash).toBe("1A2B");
@@ -17,7 +17,7 @@ describe("hashline section headers", () => {
 	});
 
 	it("recovers apply_patch-contaminated headers whose paths contain spaces", () => {
-		const section = Patch.parseSingle("[*** Update File: dir with spaces/file.ts#1A2B]\nXCHG 1..1:\n+after");
+		const section = Patch.parseSingle("[*** Update File: dir with spaces/file.ts#1A2B]\nSWAP 1..1:\n+after");
 
 		expect(section.path).toBe("dir with spaces/file.ts");
 		expect(section.fileHash).toBe("1A2B");
@@ -25,25 +25,25 @@ describe("hashline section headers", () => {
 	});
 
 	it("rejects trailing junk after a snapshot tag", () => {
-		expect(() => Patch.parse("[src/a.ts#1A2B copied from read]\nXCHG 1..1:\n+after")).toThrow(/Input header must be/);
-		expect(() => Patch.parse("[src/a.ts#1A2B:812]\nXCHG 1..1:\n+after")).toThrow(/Input header must be/);
+		expect(() => Patch.parse("[src/a.ts#1A2B copied from read]\nSWAP 1..1:\n+after")).toThrow(/Input header must be/);
+		expect(() => Patch.parse("[src/a.ts#1A2B:812]\nSWAP 1..1:\n+after")).toThrow(/Input header must be/);
 	});
 
 	it("rejects trailing junk after a snapshot tag even with apply_patch noise", () => {
-		expect(() => Patch.parse("[Update File: src/a.ts#1A2B copied from read]\nXCHG 1..1:\n+after")).toThrow(
+		expect(() => Patch.parse("[Update File: src/a.ts#1A2B copied from read]\nSWAP 1..1:\n+after")).toThrow(
 			/Input header must be/,
 		);
-		expect(() => Patch.parse("[Update File: src/a.ts#1A2B:812]\nXCHG 1..1:\n+after")).toThrow(/Input header must be/);
+		expect(() => Patch.parse("[Update File: src/a.ts#1A2B:812]\nSWAP 1..1:\n+after")).toThrow(/Input header must be/);
 	});
 
 	it("rejects malformed snapshot tags", () => {
-		expect(() => Patch.parse("[src/a.ts#1A2]\nXCHG 1..1:\n+after")).toThrow(/Input header must be/);
-		expect(() => Patch.parse("[src/a.ts#1A2G]\nXCHG 1..1:\n+after")).toThrow(/Input header must be/);
-		expect(() => Patch.parse("[src/a.ts#1A2B5]\nXCHG 1..1:\n+after")).toThrow(/Input header must be/);
+		expect(() => Patch.parse("[src/a.ts#1A2]\nSWAP 1..1:\n+after")).toThrow(/Input header must be/);
+		expect(() => Patch.parse("[src/a.ts#1A2G]\nSWAP 1..1:\n+after")).toThrow(/Input header must be/);
+		expect(() => Patch.parse("[src/a.ts#1A2B5]\nSWAP 1..1:\n+after")).toThrow(/Input header must be/);
 	});
 
 	it("rejects malformed snapshot tags even with apply_patch noise", () => {
-		expect(() => Patch.parse("[Update File: src/a.ts#1A2G]\nXCHG 1..1:\n+after")).toThrow(/Input header must be/);
+		expect(() => Patch.parse("[Update File: src/a.ts#1A2G]\nSWAP 1..1:\n+after")).toThrow(/Input header must be/);
 	});
 
 	it("reports bracket syntax with a 4-hex example when the header is missing", () => {
@@ -69,7 +69,7 @@ describe("hashline core — verb header forms", () => {
 	});
 
 	it("accepts canonical replace/delete/insert forms", () => {
-		expect(applyPatch(FILE, "XCHG 2..3:\n+X")).toBe("a\nX\nd\ne");
+		expect(applyPatch(FILE, "SWAP 2..3:\n+X")).toBe("a\nX\nd\ne");
 		expect(applyPatch(FILE, "DEL 2..3")).toBe("a\nd\ne");
 		expect(applyPatch(FILE, "INS.PRE 2:\n+X")).toBe("a\nX\nb\nc\nd\ne");
 		expect(applyPatch(FILE, "INS.POST 2:\n+X")).toBe("a\nb\nX\nc\nd\ne");
@@ -78,15 +78,15 @@ describe("hashline core — verb header forms", () => {
 	});
 
 	it("accepts single-number replace and delete shorthand", () => {
-		expect(applyPatch(FILE, "XCHG 2:\n+X")).toBe("a\nX\nc\nd\ne");
+		expect(applyPatch(FILE, "SWAP 2:\n+X")).toBe("a\nX\nc\nd\ne");
 		expect(applyPatch(FILE, "DEL 2")).toBe("a\nc\nd\ne");
 	});
 
 	it("accepts alternate replace range separators and missing colon", () => {
-		expect(applyPatch(FILE, "XCHG 2-3:\n+X")).toBe("a\nX\nd\ne");
-		expect(applyPatch(FILE, "XCHG 2\u20263:\n+X")).toBe("a\nX\nd\ne");
-		expect(applyPatch(FILE, "XCHG 2 3:\n+X")).toBe("a\nX\nd\ne");
-		expect(applyPatch(FILE, "XCHG 2..3\n+X")).toBe("a\nX\nd\ne");
+		expect(applyPatch(FILE, "SWAP 2-3:\n+X")).toBe("a\nX\nd\ne");
+		expect(applyPatch(FILE, "SWAP 2\u20263:\n+X")).toBe("a\nX\nd\ne");
+		expect(applyPatch(FILE, "SWAP 2 3:\n+X")).toBe("a\nX\nd\ne");
+		expect(applyPatch(FILE, "SWAP 2..3\n+X")).toBe("a\nX\nd\ne");
 	});
 
 	it("accepts missing colon on insert headers", () => {
@@ -97,69 +97,69 @@ describe("hashline core — verb header forms", () => {
 
 describe("hashline body contracts", () => {
 	it("auto-pipes a bare body row while warning", () => {
-		const result = parsePatch("XCHG 2..2:\n  hello");
+		const result = parsePatch("SWAP 2..2:\n  hello");
 		expect(applyEdits(FILE, result.edits).text).toBe("a\n  hello\nc\nd\ne");
 		expect(result.warnings.some(w => /Auto-prefixed bare body row/.test(w))).toBe(true);
 	});
 
 	it("strips read-output line number prefix from auto-piped bare body rows", () => {
-		const result = parsePatch("XCHG 2..2:\n2:hello");
+		const result = parsePatch("SWAP 2..2:\n2:hello");
 		expect(applyEdits(FILE, result.edits).text).toBe("a\nhello\nc\nd\ne");
 		expect(result.warnings.some(w => /Auto-prefixed bare body row/.test(w))).toBe(true);
 	});
 	it("preserves `+N:` literal payloads without stripping", () => {
-		const result = parsePatch("XCHG 2..2:\n+3:keep");
+		const result = parsePatch("SWAP 2..2:\n+3:keep");
 		expect(applyEdits(FILE, result.edits).text).toBe("a\n3:keep\nc\nd\ne");
 		expect(result.warnings.some(w => /Auto-prefixed/.test(w))).toBe(false);
 	});
 	it("strips only one N: prefix from bare body rows (preserves nested digits:colon)", () => {
 		// "2:42:hello" → should yield "42:hello", NOT "hello" (recursive would over-strip)
-		const result = parsePatch("XCHG 2..2:\n2:42:hello");
+		const result = parsePatch("SWAP 2..2:\n2:42:hello");
 		expect(applyEdits(FILE, result.edits).text).toBe("a\n42:hello\nc\nd\ne");
 	});
 
 	it("strips N: prefixes only when every bare body row carries one", () => {
-		const result = parsePatch("XCHG 2..3:\n2:foo\n3:bar");
+		const result = parsePatch("SWAP 2..3:\n2:foo\n3:bar");
 		expect(applyEdits(FILE, result.edits).text).toBe("a\nfoo\nbar\nd\ne");
 	});
 
 	it("leaves bare body rows untouched when only some carry an N: prefix", () => {
 		// "3:keep" looks like a snapshot prefix but "plain" does not, so the body
 		// is genuine content (not a pasted snapshot) — strip nothing.
-		const result = parsePatch("XCHG 2..3:\n3:keep\nplain");
+		const result = parsePatch("SWAP 2..3:\n3:keep\nplain");
 		expect(applyEdits(FILE, result.edits).text).toBe("a\n3:keep\nplain\nd\ne");
 	});
 
 	it("keeps interior blank rows in a bare replace body", () => {
-		const result = parsePatch("XCHG 2..3:\nfoo\n\nbar");
+		const result = parsePatch("SWAP 2..3:\nfoo\n\nbar");
 		expect(applyEdits(FILE, result.edits).text).toBe("a\nfoo\n\nbar\nd\ne");
 	});
 
 	it("drops trailing blank rows between a bare body and the next hunk", () => {
-		const result = parsePatch("XCHG 2..2:\nfoo\n\nXCHG 4..4:\nbaz");
+		const result = parsePatch("SWAP 2..2:\nfoo\n\nSWAP 4..4:\nbaz");
 		expect(applyEdits(FILE, result.edits).text).toBe("a\nfoo\nc\nbaz\ne");
 	});
 
 	it("skips blank rows when checking N: prefix uniformity", () => {
-		const result = parsePatch("XCHG 2..3:\n2:foo\n\n3:bar");
+		const result = parsePatch("SWAP 2..3:\n2:foo\n\n3:bar");
 		expect(applyEdits(FILE, result.edits).text).toBe("a\nfoo\n\nbar\nd\ne");
 	});
 
 	it("leaves numeric-keyed literal bodies untouched (dict/YAML shape)", () => {
-		const result = parsePatch('XCHG 2..3:\n1: "one",\n2: "two",');
+		const result = parsePatch('SWAP 2..3:\n1: "one",\n2: "two",');
 		expect(applyEdits(FILE, result.edits).text).toBe('a\n1: "one",\n2: "two",\nd\ne');
 	});
 
 	it("rejects `-` body rows with a teaching error", () => {
-		expect(() => parsePatch("XCHG 2..2:\n-old\n+new")).toThrow(/`-` rows are not valid/);
+		expect(() => parsePatch("SWAP 2..2:\n-old\n+new")).toThrow(/`-` rows are not valid/);
 	});
 
 	it("allows literal text that begins with `-` or `+` when prefixed with `+`", () => {
-		expect(applyPatch(FILE, "XCHG 2..2:\n+-literal\n++plus")).toBe("a\n-literal\n+plus\nc\nd\ne");
+		expect(applyPatch(FILE, "SWAP 2..2:\n+-literal\n++plus")).toBe("a\n-literal\n+plus\nc\nd\ne");
 	});
 
 	it("treats empty replace as delete and still rejects empty insert", () => {
-		expect(applyPatch(FILE, "XCHG 2..2:")).toBe("a\nc\nd\ne");
+		expect(applyPatch(FILE, "SWAP 2..2:")).toBe("a\nc\nd\ne");
 		expect(() => parsePatch("INS.TAIL:")).toThrow(/`INS` needs/);
 	});
 
@@ -174,23 +174,23 @@ describe("hashline body contracts", () => {
 
 describe("hashline — apply_patch / unified-diff contamination", () => {
 	it("rejects apply_patch sentinels as contamination", () => {
-		expect(() => parsePatch("*** Update File: a.ts\nXCHG 2..2:\n+X")).toThrow(/apply_patch sentinel/);
-		expect(() => parsePatch("*** Add File: a.ts\nXCHG 2..2:\n+X")).toThrow(/apply_patch sentinel/);
+		expect(() => parsePatch("*** Update File: a.ts\nSWAP 2..2:\n+X")).toThrow(/apply_patch sentinel/);
+		expect(() => parsePatch("*** Add File: a.ts\nSWAP 2..2:\n+X")).toThrow(/apply_patch sentinel/);
 	});
 
 	it("rejects unified-diff hunk headers as contamination", () => {
-		expect(() => parsePatch("@@ -1,3 +1,3 @@\nXCHG 2..2:\n+X")).toThrow(/unified-diff hunk header/);
+		expect(() => parsePatch("@@ -1,3 +1,3 @@\nSWAP 2..2:\n+X")).toThrow(/unified-diff hunk header/);
 	});
 
 	it("treats top-level `+TEXT` as an orphan literal payload", () => {
-		expect(() => parsePatch("+const X = 1;\nXCHG 2..2:")).toThrow(/payload line has no preceding hunk header/);
+		expect(() => parsePatch("+const X = 1;\nSWAP 2..2:")).toThrow(/payload line has no preceding hunk header/);
 	});
 });
 
 describe("hashline apply — duplicate boundary payloads", () => {
 	it("keeps replacement boundary echoes literal unless balance repair applies", () => {
 		const text = ["// one", "// two", "old();"].join("\n");
-		const diff = "XCHG 3..3:\n+// one\n+// two\n+new();";
+		const diff = "SWAP 3..3:\n+// one\n+// two\n+new();";
 		expect(applyPatch(text, diff)).toBe(["// one", "// two", "// one", "// two", "new();"].join("\n"));
 	});
 
diff --git a/packages/hashline/test/patcher.test.ts b/packages/hashline/test/patcher.test.ts
index 6ca5dffb2..4a2ddc8e7 100644
--- a/packages/hashline/test/patcher.test.ts
+++ b/packages/hashline/test/patcher.test.ts
@@ -25,7 +25,7 @@ describe("Patcher snapshot tag integrity", () => {
 		const tag = snapshots.record(PATH, "before\n");
 		const patcher = new Patcher({ fs, snapshots });
 
-		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG 1..1:\n+after`));
+		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP 1..1:\n+after`));
 
 		expect(result.sections[0]?.op).toBe("update");
 		expect(result.sections[0]?.fileHash).toMatch(/^[0-9A-F]{4}$/);
@@ -45,14 +45,14 @@ describe("Patcher snapshot tag integrity", () => {
 		expect(snapshots.byHash(PATH, tag)).toBeNull();
 		const patcher = new Patcher({ fs, snapshots });
 
-		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG 3..3:\n+L3`));
+		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP 3..3:\n+L3`));
 
 		expect(result.sections[0]?.op).toBe("update");
 		expect(fs.get(PATH)).toBe("l1\nl2\nL3\nl4\nl5\n");
 	});
 
 	it("normalizes lowercase section tags while parsing", () => {
-		const section = Patch.parseSingle(`[${PATH}#1a2b]\nXCHG 1..1:\n+after`);
+		const section = Patch.parseSingle(`[${PATH}#1a2b]\nSWAP 1..1:\n+after`);
 
 		expect(section.fileHash).toBe("1A2B");
 	});
@@ -65,7 +65,7 @@ describe("Patcher snapshot tag integrity", () => {
 		const patcher = new Patcher({ fs, snapshots });
 
 		try {
-			await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG 1..1:\n+after`));
+			await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP 1..1:\n+after`));
 			throw new Error("expected MismatchError");
 		} catch (error) {
 			expect(error).toBeInstanceOf(MismatchError);
@@ -89,7 +89,7 @@ describe("Patcher snapshot tag integrity", () => {
 		const bogus = live === "FFFF" ? "0000" : "FFFF";
 
 		try {
-			await patcher.apply(Patch.parse(`[${PATH}#${bogus}]\nXCHG 1..1:\n+after`));
+			await patcher.apply(Patch.parse(`[${PATH}#${bogus}]\nSWAP 1..1:\n+after`));
 			throw new Error("expected MismatchError");
 		} catch (error) {
 			expect(error).toBeInstanceOf(MismatchError);
@@ -120,7 +120,7 @@ describe("Patcher mandatory snapshot tag policy", () => {
 		const snapshots = new InMemorySnapshotStore();
 		const patcher = new Patcher({ fs, snapshots });
 
-		await expect(patcher.apply(Patch.parse(`[${PATH}]\nXCHG 1..1:\n+X`))).rejects.toThrow(
+		await expect(patcher.apply(Patch.parse(`[${PATH}]\nSWAP 1..1:\n+X`))).rejects.toThrow(
 			/Missing hashline snapshot tag/,
 		);
 	});
@@ -176,7 +176,7 @@ describe("Patcher seen-line provenance", () => {
 		const tag = snapshots.record(PATH, CONTENT, [1, 2]);
 		const patcher = new Patcher({ fs, snapshots });
 
-		await expect(patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG 4..4:\n+L4`))).rejects.toThrow(
+		await expect(patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP 4..4:\n+L4`))).rejects.toThrow(
 			/were not shown in the read\/search output/,
 		);
 		expect(fs.get(PATH)).toBe(CONTENT);
@@ -188,7 +188,7 @@ describe("Patcher seen-line provenance", () => {
 		const tag = snapshots.record(PATH, CONTENT, [1, 2]);
 		const patcher = new Patcher({ fs, snapshots });
 
-		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG 2..2:\n+L2`));
+		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP 2..2:\n+L2`));
 
 		expect(result.sections[0]?.op).toBe("update");
 		expect(fs.get(PATH)).toBe("l1\nL2\nl3\nl4\nl5\n");
@@ -202,7 +202,7 @@ describe("Patcher seen-line provenance", () => {
 		snapshots.record(PATH, CONTENT, [4, 5]);
 		const patcher = new Patcher({ fs, snapshots });
 
-		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG 4..4:\n+L4`));
+		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP 4..4:\n+L4`));
 
 		expect(result.sections[0]?.op).toBe("update");
 		expect(fs.get(PATH)).toBe("l1\nl2\nl3\nL4\nl5\n");
@@ -214,7 +214,7 @@ describe("Patcher seen-line provenance", () => {
 		const tag = snapshots.record(PATH, CONTENT);
 		const patcher = new Patcher({ fs, snapshots });
 
-		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nXCHG 4..4:\n+L4`));
+		const result = await patcher.apply(Patch.parse(`[${PATH}#${tag}]\nSWAP 4..4:\n+L4`));
 
 		expect(result.sections[0]?.op).toBe("update");
 	});
diff --git a/packages/hashline/test/recovery-session-chain.test.ts b/packages/hashline/test/recovery-session-chain.test.ts
index 3193a8dbe..1c1930357 100644
--- a/packages/hashline/test/recovery-session-chain.test.ts
+++ b/packages/hashline/test/recovery-session-chain.test.ts
@@ -33,7 +33,7 @@ describe("Recovery — session-chain replay anchor-content gate", () => {
 		// rewrote. Replaying onto current would overwrite "L5-CHANGED" with
 		// payload the model authored against the stale "L5". That is
 		// corruption, not recovery.
-		const { edits } = parsePatch("XCHG 5..5:\n|L5-MODEL");
+		const { edits } = parsePatch("SWAP 5..5:\n|L5-MODEL");
 
 		const recovered = new Recovery(store).tryRecover({
 			path: PATH,
@@ -51,7 +51,7 @@ describe("Recovery — session-chain replay anchor-content gate", () => {
 		// merge fails (patch context includes the rewritten line 5), but the
 		// replay fallback is safe because the model's anchor still names the
 		// same logical content.
-		const { edits } = parsePatch("XCHG 3..3:\n|L3-MODEL");
+		const { edits } = parsePatch("SWAP 3..3:\n|L3-MODEL");
 
 		const recovered = new Recovery(store).tryRecover({
 			path: PATH,
diff --git a/scripts/session-stats/analyze.py b/scripts/session-stats/analyze.py
index 10e468a95..55a5a08a1 100644
--- a/scripts/session-stats/analyze.py
+++ b/scripts/session-stats/analyze.py
@@ -375,7 +375,7 @@ _ANCHOR_BARE = re.compile(r"^[a-zA-Z]?[0-9]+[a-z]{2}$")
 
 
 _HASHLINE_OP = re.compile(
-    r"^(XCHG\.BLK|XCHG|DEL\.BLK|DEL|INS\.PRE|INS\.POST|INS\.HEAD|INS\.TAIL|"
+    r"^(SWAP\.BLK|SWAP|XCHG\.BLK|XCHG|DEL\.BLK|DEL|INS\.PRE|INS\.POST|INS\.HEAD|INS\.TAIL|"
     r"replace_block|replace block|replace|delete_block|delete block|delete|"
     r"insert_after_block|insert after block|insert before|insert after|insert head|insert tail)\b",
     re.I,
@@ -383,9 +383,11 @@ _HASHLINE_OP = re.compile(
 
 
 _HASHLINE_OP_ALIASES = {
-    "replace block": "XCHG.BLK",
-    "replace_block": "XCHG.BLK",
-    "replace": "XCHG",
+    "replace block": "SWAP.BLK",
+    "replace_block": "SWAP.BLK",
+    "replace": "SWAP",
+    "xchg.blk": "SWAP.BLK",
+    "xchg": "SWAP",
     "delete block": "DEL.BLK",
     "delete_block": "DEL.BLK",
     "delete": "DEL",