docs: update Mantle setup to reflect automatic shim detection

README.md

@@ -89,30 +89,35 @@ model_capabilities:
   vision: false
   context_window: 200000
   max_output_tokens: 32000
-  mantle: false               # optional — see "Mantle override" below
 ```
 
 Capabilities are published in the registry and used to register unknown models
 with fast-agent's `ModelDatabase`.
 
-### Mantle override (`model_capabilities.mantle: true`)
+### AWS Bedrock Mantle — automatic shims
 
-Set this when the `anthropic.base_url` points at the AWS Bedrock **Mantle**
-endpoint (`https://bedrock-mantle.{region}.api.aws/anthropic`). Pallas then
-installs a provider-specific override for `(Provider.ANTHROPIC, model_name)`
-in fast-agent's `ModelDatabase._PROVIDER_MODEL_OVERRIDES` that clones the
-model's base parameters but strips the features Mantle rejects:
+When `anthropic.base_url` points at a Bedrock Mantle endpoint
+(`https://bedrock-mantle.{region}.api.aws/anthropic`), Pallas auto-detects it
+at startup and installs two compatibility shims via `pallas.mantle_shims`.
+No config flag is required.
 
-- `anthropic_required_betas` — no `anthropic-beta: ...` header
-- `reasoning` / `reasoning_effort_spec` — no extended-thinking request
-- `anthropic_task_budget_supported` — no task budget
-- `anthropic_web_fetch_version` / `anthropic_web_search_version` — no web tools
-- `cache_ttl` — prompt caching disabled
+**Shim 1 — wire-name prefix.** Mantle requires the full `anthropic.<name>`
+wire id (e.g. `anthropic.claude-opus-4-7`). Fast-agent's model-spec parser
+would otherwise strip the `anthropic.` prefix, causing a misleading
+`404 "The model '...' does not exist"`. The shim registers the prefixed
+forms in `ModelDatabase._PROVIDER_WIRE_MODEL_NAMES`.
 
-Without this flag, fast-agent sends its default beta headers and `thinking`
-parameters for modern Claude models (e.g. Opus 4.7, Sonnet 4.6) which Mantle
-rejects with a misleading `404 "The model '...' does not exist"`. See
-`docs/bedrock.md` for the full configuration walkthrough.
+**Shim 2 — strip `caller: null` from replayed `tool_use` blocks.** Anthropic
+SDK 0.100.x leaks `caller: null` onto serialised `BetaToolUseBlock` params
+([upstream issue #1454](https://github.com/anthropics/anthropic-sdk-python/issues/1454)).
+`api.anthropic.com` silently tolerates the extra field; Mantle rejects it
+with `tool_use.caller: Input should be a valid dictionary or object`, which
+breaks the MCP tool-use loop on the second turn. The shim monkeypatches
+`AnthropicConverter._deserialize_assistant_raw_blocks` and
+`_append_server_tool_channel_blocks` to pop the field before history is
+re-sent.
+
+See `docs/bedrock.md` for the full configuration walkthrough.
 
 
 ---