poteat · Sep 24, 2026 · Sep 18, 2026 · Sep 18, 2026 · Sep 20, 2026
diff --git a/mods/diff/hooks/register.ts b/mods/diff/hooks/register.ts
@@ -927,9 +927,7 @@ export function register(on: On) {
       result.deny === undefined &&
       result.isError !== true
 
-    const hasLanded = isEdit
-      ? hasEdited
-      : result === undefined || result.deny === undefined
+    const hasLanded = isEdit ? hasEdited : Tools.mayHaveWritten(result)
 
     if (hasLanded) {
       landed += 1

diff --git a/mods/diff/hooks/tools/index.ts b/mods/diff/hooks/tools/index.ts
@@ -1,4 +1,5 @@
 export * from './editing-tools.js'
+export * from './may-have-written.js'
 export * from './shell-tools.js'
 export * from './todo-tool.js'
 

diff --git a/mods/diff/hooks/tools/may-have-written.ts b/mods/diff/hooks/tools/may-have-written.ts
@@ -0,0 +1,23 @@
+import type { ResultOf } from 'claude-code'
+
+/**
+ * Whether a shell tool's outcome may have changed the working tree, as the
+ * built-in gates its refresh: a throw or an answer, unless the engine says
+ * the tool held the call read-only (`ls`, `git status`); never a deny.
+ *
+ * `isReadOnly` is read through a type that may lack it, ahead of the
+ * declarations that name it; absent, the call counts as a write.
+ *
+ * @param result what `next` resolved to, or undefined when it threw
+ * @returns true when a refresh is due
+ */
+export function mayHaveWritten(
+  result: ResultOf['tool.call'] | undefined,
+): boolean {
+  const settled: { deny?: string; isReadOnly?: boolean } | undefined = result
+
+  return (
+    settled === undefined ||
+    (settled.deny === undefined && settled.isReadOnly !== true)
+  )
+}
diff --git a/mods/diff/tests/fixtures/index.ts b/mods/diff/tests/fixtures/index.ts
@@ -40,6 +40,7 @@ export * from './pane.js'
 export * from './pane-view'
 export * from './parse-file-diff'
 export * from './poll-word.js'
+export * from './read-only-answer.js'
 export * from './renamed.js'
 export * from './repository.js'
 export * from './repository-of'

diff --git a/mods/diff/tests/fixtures/read-only-answer.ts b/mods/diff/tests/fixtures/read-only-answer.ts
@@ -0,0 +1,13 @@
+import type { ResultOf } from 'claude-code'
+
+/**
+ * A shell tool's answer as the engine gives it for a command the tool holds
+ * read-only (`ls`, `git status`): the result, and `isReadOnly` beside it.
+ *
+ * Built through Object.assign, since the declarations may not name the
+ * field yet; the plugin reads it through a type that may lack it too.
+ */
+export const READ_ONLY_ANSWER: ResultOf['tool.call'] = Object.assign(
+  { result: 'listed' },
+  { isReadOnly: true as const },
+)
diff --git a/mods/diff/tests/register.test.ts b/mods/diff/tests/register.test.ts
@@ -121,6 +121,41 @@ describe('register', () => {
     )
   })
 
+  test('a shell command the tool held read-only fetches nothing', async ($, on) => {
+    const world = Fixtures.inRepository(on)
+
+    const fetchesSince = (read: number) =>
+      world.runs.slice(read).filter(run => run.argv.includes('--numstat'))
+        .length
+
+    on('tool.call', ($, e) =>
+      e.tool === 'Bash' && e.command === 'ls'
+        ? Fixtures.READ_ONLY_ANSWER
+        : { result: 'done' },
+    )
+
+    await $.session.start(Fixtures.SESSION)
+    await $.command.run(Fixtures.DIFF)
+    await world.clock.advance(Fixtures.SETTLE_MS)
+
+    const opened = world.runs.length
+
+    await $.tool.call({ tool: 'Bash', command: 'ls' })
+    await world.clock.advance(Fixtures.SETTLE_MS)
+
+    expect(
+      fetchesSince(opened),
+      "read-only, the pane open: nothing, as the built-in's touch is gated",
+    ).toBe(0)
+
+    const listed = world.runs.length
+
+    await $.tool.call({ tool: 'Bash', command: 'make' })
+    await world.clock.advance(Fixtures.SETTLE_MS)
+
+    expect(fetchesSince(listed), 'a command that may write: one fetch').toBe(1)
+  })
+
   test('/diff whose probe never answers probes once more', async ($, on) => {
     const probes: (readonly string[])[] = []
     const clock = Fixtures.startsSession(on)