diff --git a/crates/tools/src/checkout.rs b/crates/tools/src/checkout.rs
index 622dd1b3d..8a697a67d 100644
--- a/crates/tools/src/checkout.rs
+++ b/crates/tools/src/checkout.rs
@@ -404,8 +404,8 @@ fn check_pattern(pattern: &str) -> Result<(), ToolError> {
 #[path = "checkout_tests.rs"]
 mod tests;
 
-/// Read a bounded native text window through the same checked target and attachment tracker.
-/// Search callers do not establish the prior-Read precondition for mutations.
+/// Read a bounded native text window through the same checked target.
+/// The returned one-shot action records prior-Read only after the caller's presentation succeeds.
 #[allow(clippy::too_many_arguments)]
 pub async fn read_checkout_text(
     router: Arc<WorkdirSessionRouter>,
@@ -417,8 +417,7 @@ pub async fn read_checkout_text(
     offset: usize,
     limit: usize,
     max_bytes: usize,
-    record_read: bool,
-) -> Result<(workdir::ReadResult, Option<Vec<u8>>), ToolError> {
+) -> Result<(workdir::ReadResult, Option<Vec<u8>>, impl FnOnce()), ToolError> {
     let selected =
         crate::routing::resolve_session(&router, Some(alias), WorkdirSessionCapability::Read)?;
     if selected.generation != generation {
@@ -431,10 +430,11 @@ pub async fn read_checkout_text(
         validator: Some(validator),
     };
     let (result, validator) = target.read(offset, limit, max_bytes).await?;
-    if record_read {
-        tracker.record_workdir_observation(&path, result.content_hash.clone(), result.total_lines);
-    }
-    Ok((result, validator))
+    let hash = result.content_hash.clone();
+    let total_lines = result.total_lines;
+    Ok((result, validator, move || {
+        tracker.record_workdir_observation(&path, hash, total_lines);
+    }))
 }
 
 /// Binary-safe checked byte window. This does not establish a text prior-Read observation.
diff --git a/crates/worker/src/checkout.rs b/crates/worker/src/checkout.rs
index 74666982a..b57415103 100644
--- a/crates/worker/src/checkout.rs
+++ b/crates/worker/src/checkout.rs
@@ -625,7 +625,6 @@ impl WipOperationHandler for FileHandler {
                     offset,
                     limit,
                     crate::file_operation::MAX_BYTES,
-                    operation == "read_lines",
                 ),
             )
             .await
@@ -636,7 +635,7 @@ impl WipOperationHandler for FileHandler {
                 )
             })?
             .map_err(map_tool_error)?;
-            let (read, validator) = result;
+            let (read, validator, record_read) = result;
             self.check_connection()?;
             let text = String::from_utf8_lossy(&read.bytes);
             let value = crate::file_operation::page_result(
@@ -646,6 +645,11 @@ impl WipOperationHandler for FileHandler {
                 offset,
                 read.truncated,
             )?;
+            // Only a successfully rendered Read can establish mutation authority.
+            // Search and failed result budgets must leave prior-Read history unchanged.
+            if operation == "read_lines" {
+                record_read();
+            }
             return Ok(match validator {
                 Some(raw) => WipOperationOutput::native_with_validator(
                     value,
diff --git a/crates/worker/src/checkout_http_tests.rs b/crates/worker/src/checkout_http_tests.rs
index a7871239b..7436dc525 100644
--- a/crates/worker/src/checkout_http_tests.rs
+++ b/crates/worker/src/checkout_http_tests.rs
@@ -841,3 +841,41 @@ async fn remote_checked_byte_read_uses_common_contract_and_keeps_binary_boundari
         source.bytes
     );
 }
+
+#[tokio::test]
+async fn http_failed_text_read_does_not_authorize_mutations() {
+    for operation in ["write", "edit"] {
+        for oversized in ["\"".repeat(50_000), "x".repeat(65_530)] {
+            let fixture = HttpFixture::new(WorkdirSessionCapabilities::READ_WRITE).await;
+            let remote = fixture.open(TOKEN).await.unwrap();
+            checkout_wip_tests::failed_text_read_cannot_authorize_mutation(
+                Arc::new(remote),
+                &fixture.dir.path().join("text"),
+                &oversized,
+                operation,
+            )
+            .await;
+            let mutations = fixture
+                .state
+                .operations
+                .lock()
+                .unwrap()
+                .iter()
+                .filter(|op| {
+                    matches!(
+                        op,
+                        WorkdirSessionOperation::CheckoutExecute(CheckoutRequest {
+                            operation: CheckoutOperation::Write { .. }
+                                | CheckoutOperation::Edit { .. },
+                            ..
+                        })
+                    )
+                })
+                .count();
+            assert_eq!(
+                mutations, 1,
+                "only the mutation after a successful Read may reach the provider"
+            );
+        }
+    }
+}
diff --git a/crates/worker/src/checkout_wip_tests.rs b/crates/worker/src/checkout_wip_tests.rs
index 9460924f1..199b2b32d 100644
--- a/crates/worker/src/checkout_wip_tests.rs
+++ b/crates/worker/src/checkout_wip_tests.rs
@@ -1536,3 +1536,82 @@ fn common_contract_registration_rejects_descriptor_redefinition_and_domain_opera
         Err(WipMountError::InterfaceCollision { .. })
     ));
 }
+
+pub(super) async fn failed_text_read_cannot_authorize_mutation(
+    source: WorkdirSessionHandle,
+    disk_file: &std::path::Path,
+    oversized: &str,
+    operation: &str,
+) {
+    let original = format!("{oversized}\nknown\n");
+    std::fs::write(disk_file, &original).unwrap();
+    let router = Arc::new(WorkdirSessionRouter::new());
+    router
+        .attach(WorkdirAttachmentAlias::new("main").unwrap(), source)
+        .unwrap();
+    let r = Arc::new(runtime(router, None));
+    let inspected = model_inspect(r.clone(), "/checkouts/main/text").await;
+    let arguments = if operation == "write" {
+        json!({"content":"changed"})
+    } else {
+        json!({"old_string":"known","new_string":"changed"})
+    };
+    let failure = model_invoke(r.clone(), &inspected, "read", json!({"limit":1}))
+        .await
+        .unwrap_err();
+    assert!(
+        failure.to_string().contains("ResourceLimitExceeded"),
+        "{failure}"
+    );
+    let denied = model_invoke(r.clone(), &inspected, operation, arguments.clone()).await;
+    assert!(denied.is_err(), "failed read authorized {operation}");
+    let denied = denied.unwrap_err();
+    assert!(denied.to_string().contains("InvalidArguments"), "{denied}");
+    assert_eq!(std::fs::read_to_string(disk_file).unwrap(), original);
+    model_invoke(r.clone(), &inspected, "read", json!({"offset":1,"limit":1}))
+        .await
+        .unwrap();
+    // A failed read must neither grant new authority nor erase an earlier successful Read.
+    assert!(
+        model_invoke(r.clone(), &inspected, "read", json!({"limit":1}))
+            .await
+            .is_err()
+    );
+    model_invoke(r, &inspected, operation, arguments)
+        .await
+        .unwrap();
+    let expected = if operation == "write" {
+        "changed".to_string()
+    } else {
+        original.replace("known", "changed")
+    };
+    assert_eq!(std::fs::read_to_string(disk_file).unwrap(), expected);
+}
+
+#[tokio::test]
+async fn failed_text_read_does_not_authorize_write() {
+    for oversized in ["\"".repeat(50_000), "x".repeat(65_530)] {
+        let dir = TempDir::new().unwrap();
+        failed_text_read_cannot_authorize_mutation(
+            session(&dir, false),
+            &dir.path().join("text"),
+            &oversized,
+            "write",
+        )
+        .await;
+    }
+}
+
+#[tokio::test]
+async fn failed_text_read_does_not_authorize_edit() {
+    for oversized in ["\"".repeat(50_000), "x".repeat(65_530)] {
+        let dir = TempDir::new().unwrap();
+        failed_text_read_cannot_authorize_mutation(
+            session(&dir, false),
+            &dir.path().join("text"),
+            &oversized,
+            "edit",
+        )
+        .await;
+    }
+}