Sanitize tool-call IDs on the Anthropic Messages wire

[jcheng5]

Problem

The Anthropic Messages API validates tool_use.id / tool_result.tool_use_id against ^[a-zA-Z0-9_-]+$. Other wires accept arbitrary IDs — e.g. Kimi K3 emits <toolName>:<counter> like ls:0, with the counter resetting per turn so duplicates across history are the norm. When a conversation containing such IDs is replayed to an Anthropic-wire model (model switch mid-conversation, /compact summarizing with Claude Haiku), the API rejects the request:

Error making request (HTTP 400): messages.1.content.1.tool_use.id: String should match pattern '^[a-zA-Z0-9_-]+$'

Fixes posit-dev/assistant#2016.

Fix

The constraint is a property of the target wire, so Anthropic-wire clients now sanitize outbound IDs unconditionally via a new sanitizeToolCallIdsForAnthropic helper (tool-call-ids.ts):

• Base: deterministic character replacement ([^a-zA-Z0-9_-] → -); empty IDs fall back to call.
• Uniqueness: rewritten ID = <base>-<i> where i is the message index in the outbound array. Pairing is positional: a tool-result in a tool message at j uses j-1; a provider-executed result in an assistant message uses its own index. Deterministic and prompt-cache-stable because history is append-only.
• Conforming duplicates (same ID used by a call in an earlier message) are index-suffixed via first-occurrence tracking on tool-calls — results mirror their paired call. (A naive seen-set over all parts would break pairing, since results legitimately repeat their call's ID.)
• No-op fast path: conforming first-use IDs pass through untouched; pure-Claude histories get the input array back by reference.
• Observability: warns on non-conforming IDs, same-message base collisions, and orphan tool-result parts.

Wiring goes through a shared streamTextAnthropicWire() choke point so future Anthropic-wire clients get sanitization by default: AnthropicClient, PositAiClient (anthropic-messages branch), and SnowflakeClient (chatAnthropic) use the wrapper; BedrockClient and GoogleVertexClient sanitize conditionally on their Anthropic routes since those streamText call sites are shared across protocols.

Tests

• 11 sanitizer unit tests: deterministic rewrite, positional pairing (both result kinds), cross-turn duplicates (ls:0 in two turns), same-turn parallel calls, conforming-duplicate suffixing, empty-ID fallback, no-op passthrough, collision/orphan warnings.
• Wire-level regression test through PositAiClient with the observed Kimi ls:0 format repeated across two turns, asserting the serialized request body contains only pattern-conforming, unique, paired IDs. Verified to fail on the unfixed code.

Full bridge suite (286 tests) and monorepo check-types pass.