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fix: account for base64 encoding overhead in image size limit

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The Anthropic API has a 5MB limit on base64-encoded images, not raw file
size. Base64 encoding increases size by ~33% (4/3 ratio), so a 4MB raw
image becomes ~5.3MB encoded, exceeding the limit.

Changed MAX_IMAGE_SIZE from 5MB to ~3.75MB (5MB * 3/4) to trigger
resizing before the base64-encoded result exceeds the API limit.

Also updated target resize size to 3.6MB to leave margin.
This commit is contained in:
Dhanji R. Prasanna
2026-01-16 21:29:05 +05:30
parent 1003386f7f
commit c7984fd4c2
1 changed files with 8 additions and 4 deletions
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12
crates/g3-core/src/tools/file_ops.rs
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@@ -13,8 +13,11 @@ use crate::ToolCall;
use super::executor::ToolContext; use super::executor::ToolContext;
/// Maximum image size in bytes (5MB) - images larger than this will be resized /// Maximum base64-encoded image size in bytes (5MB) - Anthropic API limit
const MAX_IMAGE_SIZE: usize = 5 * 1024 * 1024; const MAX_BASE64_SIZE: usize = 5 * 1024 * 1024;
/// Maximum raw image size before base64 encoding (~3.75MB to stay under 5MB after encoding)
const MAX_IMAGE_SIZE: usize = (MAX_BASE64_SIZE * 3) / 4;
/// Bytes per token heuristic (conservative estimate for code/text mix) /// Bytes per token heuristic (conservative estimate for code/text mix)
const BYTES_PER_TOKEN: f32 = 3.5; const BYTES_PER_TOKEN: f32 = 3.5;
@@ -318,9 +321,10 @@ pub async fn execute_read_image<W: UiWriter>(
let original_size = bytes.len(); let original_size = bytes.len();
// Resize image if it's >= 5MB (target < 4.9MB to leave margin) // Resize image if it exceeds MAX_IMAGE_SIZE (~3.75MB raw = ~5MB base64)
// Target slightly smaller to leave margin for base64 overhead
let (bytes, was_resized) = if original_size >= MAX_IMAGE_SIZE { let (bytes, was_resized) = if original_size >= MAX_IMAGE_SIZE {
match resize_image_if_needed(&bytes, path, MAX_IMAGE_SIZE - 100 * 1024) { match resize_image_if_needed(&bytes, path, MAX_IMAGE_SIZE - 150 * 1024) {
Ok(resized) => { Ok(resized) => {
let resized_size = resized.len(); let resized_size = resized.len();
if resized_size < original_size { if resized_size < original_size {