* Studio: wire Anthropic web_fetch server-side tool
Studio's Anthropic passthrough only forwarded web_search and
code_execution when enabled_tools was set. Asking Claude through Studio
to fetch a URL produced no fetch (the tool was not in the outbound
tools array), so users had to fall back to web_search even when they
already had the exact URL they wanted.
This change opts in web_fetch_20250910 when enabled_tools contains
"web_fetch". The new tool entry is appended alongside any existing
web_search / code_execution entries:
{"type": "web_fetch_20250910", "name": "web_fetch", "max_uses": 5}
No anthropic-beta header is required (web_fetch is GA); the existing
code-execution-2025-08-25 flag continues to merge cleanly when both
tools are enabled in the same turn.
SSE translation mirrors the web_search path. A `server_tool_use` block
with name="web_fetch" emits a `tool_start` _toolEvent carrying the
URL the model asked to fetch; the matching `web_fetch_tool_result`
block emits a `tool_end` _toolEvent whose result string follows the
Title / URL / Snippet shape parseSourcesFromResult on the frontend
already expects, so the source pill renders identically. Error blocks
(`web_fetch_tool_error`) are surfaced as "Error: <error_code>" matching
the code_execution error path.
The final "Anthropic stream complete" log line picks up web_fetch_
requested / web_fetch_invocations / web_fetch_urls so support reports
of "the model did not fetch anything" can be triaged from the log.
Verified end to end against claude-haiku-4-5 with
`enabled_tools=["web_fetch"]`: the model emitted tool_start with
url=https://example.com and tool_end with the page Title + URL +
Snippet, plus the assistant message correctly read back "Example
Domain" as the title.
Tests:
- 5 new unit tests in test_anthropic_web_fetch.py covering tool
registration, the combined web_search + web_fetch + code_execution
request body, the pill-off case, and SSE translation for both
success and error paths.
- All 242 existing Anthropic + OpenAI provider tests still pass.
The enabled_tools field description in models/inference.py is updated
so OpenAPI consumers see the new option.
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* web_fetch: title fallback to URL, log parse failures, drop dead checks
Three review nits on the previous commit:
1. `_format_web_fetch_result` left `title` empty when Anthropic omitted
`document.title`. The frontend `parseSourcesFromResult` only emits
a source pill when both `Title:` and `URL:` lines are present, so
fetches against pages without an HTML title tag silently lost
their citation in the UI. Fall back to `title = title or url`,
matching the web_search formatter.
2. The broad `except Exception` around `json.loads(buffer)` for the
web_fetch input swallowed the failure with no trace. Log at debug
so a malformed partial_json buffer can be triaged from the server
log without changing behavior.
3. `inner` was already sanitised to a dict at the matching
content_block_start and `_format_web_fetch_result` always returns
a non-empty string (defaulting to "(fetch complete)"), so the
`isinstance(inner, dict) else {}` guard and the
`result_text or "(fetch complete)"` fallback at the emit site
were dead code. Removed.
Added a test exercising the titleless path so the fallback stays
covered.
* chat-adapter: emit source pills for web_fetch tool calls
`parseSourcesFromResult` was only wired up for tool calls where
`toolName === "web_search"`, so the Title / URL / Snippet block the
backend formatter emits for `web_fetch_tool_result` never reached the
source-pill renderer. Users saw the raw tool result in the tool card
but the dedicated source-pill row at the message tail stayed empty.
Both web_search and web_fetch ship the same text shape today, so the
fix is to broaden the gate.
* Address review: wire web_fetch from Search pill + fix pause_turn truncation
Two reviewer follow-ups on the Anthropic web_fetch PR:
1. The backend tool wiring landed but the frontend chat-adapter
never put `web_fetch` in `enabled_tools`, so toggling the Search
pill only ever attached `web_search` -- web_fetch was unreachable
from the UI. Added providerSupportsBuiltinWebFetch() (Anthropic
today) and paired the entry with the existing Search pill, since
the canonical workflow is "search returns URLs, fetch reads
them" and there is no separate UI toggle yet.
2. `pause_turn` from Anthropic's stop_reason vocabulary fell through
the finish_reason map's "stop" default, which the OpenAI-format
client renders as end-of-message and truncates the answer. Per
the docs pause_turn means "Claude paused a long server-tool
turn (web_search / web_fetch) and will resume". Mapped to None
and skipped the chunk emission so the SSE stream still ends with
[DONE] on message_stop but no terminal finish_reason lands on
the client. While there: added explicit mappings for `tool_use`
(-> tool_calls) and `refusal` (-> content_filter) which were
also falling through to "stop".
Tests added: pause_turn emits no finish_reason, end_turn still
emits "stop", refusal maps to "content_filter".
Sourcing: https://platform.claude.com/docs/en/api/messages#response-stop-reason
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