diff --git a/crates/load-cargo/src/lib.rs b/crates/load-cargo/src/lib.rs
index 33468a5003c3..8342492a33a4 100644
--- a/crates/load-cargo/src/lib.rs
+++ b/crates/load-cargo/src/lib.rs
@@ -553,6 +553,7 @@ impl ProcMacroExpander for Expander {
 
                 Ok(SubResponse::LocalFilePathResult { name })
             }
+            // Not incremental: requires full file text.
             SubRequest::SourceText { file_id, ast_id, start, end } => {
                 let range = resolve_sub_span(
                     db,
@@ -567,6 +568,7 @@ impl ProcMacroExpander for Expander {
 
                 Ok(SubResponse::SourceTextResult { text })
             }
+            // Not incremental: requires building line index.
             SubRequest::LineColumn { file_id, ast_id, offset } => {
                 let range =
                     resolve_sub_span(db, file_id, ast_id, TextRange::empty(TextSize::from(offset)));
@@ -591,6 +593,17 @@ impl ProcMacroExpander for Expander {
 
                 Ok(SubResponse::FilePathResult { name })
             }
+            // Not incremental: requires global span resolution.
+            SubRequest::ByteRange { file_id, ast_id, start, end } => {
+                let range = resolve_sub_span(
+                    db,
+                    file_id,
+                    ast_id,
+                    TextRange::new(TextSize::from(start), TextSize::from(end)),
+                );
+
+                Ok(SubResponse::ByteRangeResult { range: range.range.into() })
+            }
         };
         match self.0.expand(
             subtree.view(),
diff --git a/crates/proc-macro-api/src/bidirectional_protocol/msg.rs b/crates/proc-macro-api/src/bidirectional_protocol/msg.rs
index 0e3b700dcc5a..57e7b1ee8f68 100644
--- a/crates/proc-macro-api/src/bidirectional_protocol/msg.rs
+++ b/crates/proc-macro-api/src/bidirectional_protocol/msg.rs
@@ -1,5 +1,7 @@
 //! Bidirectional protocol messages
 
+use std::ops::Range;
+
 use paths::Utf8PathBuf;
 use serde::{Deserialize, Serialize};
 
@@ -14,6 +16,7 @@ pub enum SubRequest {
     SourceText { file_id: u32, ast_id: u32, start: u32, end: u32 },
     LocalFilePath { file_id: u32 },
     LineColumn { file_id: u32, ast_id: u32, offset: u32 },
+    ByteRange { file_id: u32, ast_id: u32, start: u32, end: u32 },
 }
 
 #[derive(Debug, Serialize, Deserialize)]
@@ -32,6 +35,9 @@ pub enum SubResponse {
         line: u32,
         column: u32,
     },
+    ByteRangeResult {
+        range: Range<usize>,
+    },
 }
 
 #[derive(Debug, Serialize, Deserialize)]
diff --git a/crates/proc-macro-srv-cli/src/main_loop.rs b/crates/proc-macro-srv-cli/src/main_loop.rs
index 0c651d22b41b..3beaeb0697ec 100644
--- a/crates/proc-macro-srv-cli/src/main_loop.rs
+++ b/crates/proc-macro-srv-cli/src/main_loop.rs
@@ -6,7 +6,10 @@ use proc_macro_api::{
     transport::codec::{json::JsonProtocol, postcard::PostcardProtocol},
     version::CURRENT_API_VERSION,
 };
-use std::io::{self, BufRead, Write};
+use std::{
+    io::{self, BufRead, Write},
+    ops::Range,
+};
 
 use legacy::Message;
 
@@ -240,6 +243,23 @@ impl<C: Codec> proc_macro_srv::ProcMacroClientInterface for ProcMacroClientHandl
             _ => None,
         }
     }
+
+    fn byte_range(
+        &mut self,
+        proc_macro_srv::span::Span { range, anchor, ctx: _ }: proc_macro_srv::span::Span,
+    ) -> Range<usize> {
+        match self.roundtrip(bidirectional::SubRequest::ByteRange {
+            file_id: anchor.file_id.as_u32(),
+            ast_id: anchor.ast_id.into_raw(),
+            start: range.start().into(),
+            end: range.end().into(),
+        }) {
+            Some(bidirectional::BidirectionalMessage::SubResponse(
+                bidirectional::SubResponse::ByteRangeResult { range },
+            )) => range,
+            _ => Range { start: range.start().into(), end: range.end().into() },
+        }
+    }
 }
 
 fn handle_expand_ra<C: Codec>(
diff --git a/crates/proc-macro-srv/src/lib.rs b/crates/proc-macro-srv/src/lib.rs
index c1ef49a7176b..ac9f89352c2b 100644
--- a/crates/proc-macro-srv/src/lib.rs
+++ b/crates/proc-macro-srv/src/lib.rs
@@ -41,6 +41,7 @@ use std::{
     env,
     ffi::OsString,
     fs,
+    ops::Range,
     path::{Path, PathBuf},
     sync::{Arc, Mutex, PoisonError},
     thread,
@@ -100,6 +101,8 @@ pub trait ProcMacroClientInterface {
     fn local_file(&mut self, file_id: span::FileId) -> Option<String>;
     /// Line and column are 1-based.
     fn line_column(&mut self, span: Span) -> Option<(u32, u32)>;
+
+    fn byte_range(&mut self, span: Span) -> Range<usize>;
 }
 
 const EXPANDER_STACK_SIZE: usize = 8 * 1024 * 1024;
diff --git a/crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs b/crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs
index 3a25391b573b..9946608247c3 100644
--- a/crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs
+++ b/crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs
@@ -162,7 +162,10 @@ impl server::Span for RaSpanServer<'_> {
         span
     }
     fn byte_range(&mut self, span: Self::Span) -> Range<usize> {
-        // FIXME requires db to resolve the ast id, THIS IS NOT INCREMENTAL
+        if let Some(cb) = self.callback.as_mut() {
+            return cb.byte_range(span);
+        }
+
         Range { start: span.range.start().into(), end: span.range.end().into() }
     }
     fn join(&mut self, first: Self::Span, second: Self::Span) -> Option<Self::Span> {
diff --git a/crates/proc-macro-srv/src/tests/utils.rs b/crates/proc-macro-srv/src/tests/utils.rs
index 81ff1965d68b..b7c5c4fdd21f 100644
--- a/crates/proc-macro-srv/src/tests/utils.rs
+++ b/crates/proc-macro-srv/src/tests/utils.rs
@@ -4,6 +4,7 @@ use expect_test::Expect;
 use span::{
     EditionedFileId, FileId, ROOT_ERASED_FILE_AST_ID, Span, SpanAnchor, SyntaxContext, TextRange,
 };
+use std::ops::Range;
 
 use crate::{
     EnvSnapshot, ProcMacroClientInterface, ProcMacroSrv, SpanId, dylib, proc_macro_test_dylib_path,
@@ -137,6 +138,10 @@ impl ProcMacroClientInterface for MockCallback<'_> {
         // proc_macro uses 1-based line/column
         Some((line_col.line as u32 + 1, line_col.col as u32 + 1))
     }
+
+    fn byte_range(&mut self, span: Span) -> Range<usize> {
+        Range { start: span.range.start().into(), end: span.range.end().into() }
+    }
 }
 
 pub fn assert_expand_with_callback(