fix(translation): rewrite colliding anthropic tool-call ids (#502)

crates/switchyard-translation/src/codecs/anthropic/buffered.rs

@@ -23,9 +23,9 @@ use crate::llm::{
 };
 use crate::policy::{DeterministicIdPolicy, TranslationPolicy};
 use crate::util::{
-    capture_request_preservation, capture_response_preservation, desanitize_anthropic_tool_use_id,
-    embed_preservation, exact_preserved_request, exact_preserved_response,
-    sanitize_anthropic_tool_use_id,
+    AnthropicToolIdRewriter, attach_seen_tool_ids, capture_request_preservation,
+    capture_response_preservation, desanitize_anthropic_tool_use_id, embed_preservation,
+    exact_preserved_request, exact_preserved_response, sanitize_anthropic_tool_use_id,
 };
 use crate::util::{
     json_string, push_lossy, reject_responses_builtin_tool_item, stable_id, string_value,
@@ -178,6 +178,7 @@ impl FormatCodec for AnthropicMessagesCodec {
             .extensions
             .fields
             .insert(ANTHROPIC_REQUEST_KEY.to_string(), Value::Bool(true));
+        attach_seen_tool_ids(&mut request.extensions.fields, &request.messages);
 
         Ok(DecodedRequest {
             request,
@@ -311,7 +312,12 @@ impl FormatCodec for AnthropicMessagesCodec {
             output_config.insert("format".to_string(), format);
         }
 
-        let body = embed_preservation(Value::Object(body), &request.preservation, policy);
+        // Anthropic rejects repeated tool IDs, so a conversation that already
+        // carries a repeat (for example from a backend that reuses IDs) must
+        // reach the provider with one distinct ID per call and its result.
+        let mut body = Value::Object(body);
+        AnthropicToolIdRewriter::default().rewrite_body(&mut body);
+        let body = embed_preservation(body, &request.preservation, policy);
         Ok(EncodedRequest { body, diagnostics })
     }
 

crates/switchyard-translation/src/engine.rs

@@ -21,6 +21,7 @@ use crate::error::{Result, TranslationError};
 use crate::format::FormatId;
 use crate::llm::{AggLlmResponse, LlmRequest, ProviderExtensions};
 use crate::policy::TranslationPolicy;
+use crate::util::{AnthropicToolIdRewriter, seen_tool_ids};
 
 /// Encoded translation result with any diagnostics emitted along the way.
 #[derive(Debug)]
@@ -221,6 +222,10 @@ impl TranslationEngine {
             &mut output.body,
             &crate::codex_custom_tools::custom_tool_names(request_extensions),
         );
+        // A single response knows nothing about earlier turns, so the IDs the
+        // conversation already used seed the rewrite of this turn's calls.
+        let mut tool_ids = AnthropicToolIdRewriter::new(seen_tool_ids(request_extensions));
+        tool_ids.rewrite_body(&mut output.body);
         Ok(output)
     }
 

crates/switchyard-translation/src/helpers.rs

@@ -127,6 +127,10 @@ pub fn encode_stream_with_extensions(
     let origins = crate::codex_namespaces::qualified_tool_origins(request_extensions);
     let custom_tools = crate::codex_custom_tools::custom_tool_names(request_extensions);
     let mut custom_state = crate::codex_custom_tools::CustomToolCallStreamState::default();
+    // One response knows nothing about earlier turns, so the IDs the conversation
+    // already used seed the rewrite of tool IDs across all of this stream's events.
+    let mut tool_ids =
+        crate::util::AnthropicToolIdRewriter::new(crate::util::seen_tool_ids(request_extensions));
     let target_format: FormatId = target.into();
     // The target is always a built-in wire format, so this lookup cannot fail; a
     // failure returns as an `Err` rather than a panic.
@@ -153,6 +157,7 @@ pub fn encode_stream_with_extensions(
             for value in &mut encoded {
                 stamp_streamed_response_model(value, target, served_model_for_events.as_deref());
                 crate::codex_namespaces::restore_qualified_tool_names(value, &origins);
+                tool_ids.rewrite_body(value);
             }
             // Argument deltas for a freeform tool cannot be expressed on the wire; the
             // rewritten completed item carries the input instead.
@@ -187,6 +192,7 @@ pub fn encode_stream_with_extensions(
                 served_model_for_events.as_deref(),
             );
             crate::codex_namespaces::restore_qualified_tool_names(&mut value, &origins);
+            tool_ids.rewrite_body(&mut value);
             if crate::codex_custom_tools::restore_custom_tool_calls_in_event(
                 &mut value,
                 &custom_tools,

crates/switchyard-translation/src/lib.rs

@@ -34,6 +34,6 @@ pub use llm::*;
 pub use policy::*;
 pub use stream::*;
 pub use util::{
-    PRESERVATION_METADATA_KEY, normalize_anthropic_tool_use_ids, prepare_request_for_target,
-    sanitize_anthropic_tool_use_id,
+    AnthropicToolIdRewriter, PRESERVATION_METADATA_KEY, SEEN_TOOL_IDS_KEY,
+    prepare_request_for_target, sanitize_anthropic_tool_use_id,
 };