Every model change that would have broken your app

Providers ship silent snapshot updates. We watch malformed-response rates per model and publish a proxy rule the same day, so the fix lands upstream of your code.

1. 2026-07-28OpenAIRegression

   Markdown fences reappeared around JSON responses

   gpt-4o (2026-07-24 snapshot)

   What we detected

   Malformed-JSON rate on structured output rose from 0.4% to 3.6% across 100k proxied requests within 6 hours of the snapshot rollout.

   How the proxy patched it

   Proxy rule fence-strip-v3 now unwraps ```json blocks before validation, so applications received clean objects with zero code changes.

2. 2026-07-09AnthropicBreaking

   Tool-use blocks emitted before text blocks

   claude-3.7-sonnet

   What we detected

   Clients reading content[0].text began throwing on 12% of tool calls as block ordering changed.

   How the proxy patched it

   Response normaliser reorders content blocks to the documented shape and exposes tool calls under a stable tool_calls alias.

3. 2026-06-22GeminiRegression

   Enum fields returned title-cased values

   gemini-2.5-pro

   What we detected

   Classification pipelines saw a 5.1% spike in schema violations where 'Billing' was returned instead of 'billing'.

   How the proxy patched it

   Enum coercion rule matches case-insensitively against the declared enum and repairs the value, logging each repair as a drift event.

4. 2026-06-03OpenAIAdvisory

   Silent context window truncation on long prompts

   gpt-4o-mini

   What we detected

   Requests above 118k input tokens were truncated without an error, producing confidently wrong summaries.

   How the proxy patched it

   Pre-flight token accounting rejects or prunes oversized prompts and surfaces a x-driftwatch-truncation-risk header.

5. 2026-05-14AnthropicRegression

   Trailing commas in nested JSON objects

   claude-3.5-haiku

   What we detected

   0.9% of extraction responses failed strict JSON.parse, concentrated in payloads with more than 4 nesting levels.

   How the proxy patched it

   Tolerant JSON repair pass fixes trailing commas and unescaped newlines, then re-validates against your schema before responding.

6. 2026-04-30GeminiBreaking

   Function-call arguments delivered as a string

   gemini-2.0-flash

   What we detected

   Argument objects arrived JSON-encoded inside a string, breaking every downstream tool router on first deploy.

   How the proxy patched it

   Proxy parses stringified argument payloads into objects and normalises them to the OpenAI tool-call shape.