diff --git a/rust/README.md b/rust/README.md
index 53ebfc744e..8fa9882a83 100644
--- a/rust/README.md
+++ b/rust/README.md
@@ -110,13 +110,30 @@ Primary artifacts:
 
 ## Model Aliases
 
-Short names resolve to the latest model versions:
-
-| Alias | Resolves To |
-|-------|------------|
-| `opus` | `claude-opus-4-7` |
-| `sonnet` | `claude-sonnet-4-6` |
-| `haiku` | `claude-haiku-4-5-20251213` |
+Short model aliases resolve to canonical model IDs. Because the router selects a
+provider from the resolved model, an alias also determines which backend and
+credentials are used — choose the alias for the provider you have an API key for.
+Alias resolution is case-insensitive (`OPUS` behaves the same as `opus`). Aliases
+are the bare short names listed below: a prefixed form such as `anthropic/opus`
+is not an alias, and is passed through as-is rather than expanded to
+`claude-opus-4-7`.
+
+| Alias | Resolves To | Provider | Auth env var |
+|-------|-------------|----------|--------------|
+| `opus` | `claude-opus-4-7` | Anthropic | `ANTHROPIC_API_KEY` |
+| `sonnet` | `claude-sonnet-4-6` | Anthropic | `ANTHROPIC_API_KEY` |
+| `haiku` | `claude-haiku-4-5-20251213` | Anthropic | `ANTHROPIC_API_KEY` |
+| `grok`, `grok-3` | `grok-3` | xAI | `XAI_API_KEY` |
+| `grok-mini`, `grok-3-mini` | `grok-3-mini` | xAI | `XAI_API_KEY` |
+| `grok-2` | `grok-2` | xAI | `XAI_API_KEY` |
+| `kimi` | `kimi-k2.5` | DashScope (OpenAI-compatible) | `DASHSCOPE_API_KEY` |
+
+Anthropic aliases track the latest published model versions. xAI models honor
+`XAI_BASE_URL` and Kimi honors `DASHSCOPE_BASE_URL` for base-URL overrides. Alias
+resolution is implemented in `resolve_model_alias`
+([`crates/api/src/providers/mod.rs`](./crates/api/src/providers/mod.rs)); for
+provider-specific request handling see
+[`../docs/MODEL_COMPATIBILITY.md`](../docs/MODEL_COMPATIBILITY.md).
 
 ## CLI Flags and Commands
 
diff --git a/rust/crates/api/src/providers/mod.rs b/rust/crates/api/src/providers/mod.rs
index 2524e5520a..b571f9ee0c 100644
--- a/rust/crates/api/src/providers/mod.rs
+++ b/rust/crates/api/src/providers/mod.rs
@@ -902,6 +902,135 @@ mod tests {
         assert_eq!(resolve_model_alias("grok-2"), "grok-2");
     }
 
+    /// Collects every non-empty backtick-delimited span in a markdown cell.
+    fn backticked(cell: &str) -> Vec<&str> {
+        let mut spans = Vec::new();
+        let mut rest = cell;
+        while let Some(start) = rest.find('`') {
+            let after_open = &rest[start + 1..];
+            let Some(end) = after_open.find('`') else {
+                break;
+            };
+            spans.push(&after_open[..end]);
+            rest = &after_open[end + 1..];
+        }
+        spans
+    }
+
+    // Locks the `## Model Aliases` table in `rust/README.md` to the resolver.
+    //
+    // The table and the alias set must agree in *both* directions: no alias may
+    // resolve without being documented, and none may be documented without
+    // resolving. The table previously listed only the three Anthropic aliases
+    // while the resolver had grown xAI and Kimi entries, so an alias could work
+    // undocumented — exactly the drift a parity test catches and a hand-written
+    // `assert_eq!` per alias does not.
+    #[test]
+    fn readme_alias_table_matches_resolver() {
+        // `rust/crates/api/src/providers/mod.rs` -> `rust/README.md`.
+        const README: &str = include_str!("../../../../README.md");
+
+        let section = README
+            .split("## Model Aliases")
+            .nth(1)
+            .expect("rust/README.md must keep a `## Model Aliases` section");
+        let section = section.split("\n## ").next().unwrap_or(section);
+
+        // (alias, documented canonical id, documented auth env var)
+        let mut documented: Vec<(String, String, String)> = Vec::new();
+        for line in section.lines() {
+            let line = line.trim();
+            let Some(row) = line.strip_prefix('|') else {
+                continue;
+            };
+            let cells: Vec<&str> = row
+                .trim_end_matches('|')
+                .split('|')
+                .map(str::trim)
+                .collect();
+            if cells.len() < 4 {
+                continue;
+            }
+            let aliases = backticked(cells[0]);
+            if aliases.is_empty() {
+                // Header and `|---|---|` separator rows carry no aliases.
+                continue;
+            }
+            let canonicals = backticked(cells[1]);
+            assert_eq!(
+                canonicals.len(),
+                1,
+                "`{line}` must document exactly one canonical model id"
+            );
+            let auth_envs = backticked(cells[3]);
+            assert_eq!(
+                auth_envs.len(),
+                1,
+                "`{line}` must document exactly one auth env var"
+            );
+            for alias in aliases {
+                documented.push((
+                    alias.to_string(),
+                    canonicals[0].to_string(),
+                    auth_envs[0].to_string(),
+                ));
+            }
+        }
+
+        assert!(
+            !documented.is_empty(),
+            "parsed no alias rows out of the `## Model Aliases` table in rust/README.md"
+        );
+
+        for (alias, canonical, auth_env) in &documented {
+            let resolved = resolve_model_alias(alias);
+            assert_eq!(
+                resolved.as_str(),
+                canonical.as_str(),
+                "rust/README.md documents `{alias}` -> `{canonical}`, but resolve_model_alias returns `{resolved}`"
+            );
+            assert_eq!(
+                resolve_model_alias(&alias.to_ascii_uppercase()).as_str(),
+                resolved.as_str(),
+                "rust/README.md claims alias resolution is case-insensitive, but `{}` disagrees with `{alias}`",
+                alias.to_ascii_uppercase()
+            );
+            let metadata = super::metadata_for_model(&resolved).unwrap_or_else(|| {
+                panic!("no provider metadata for documented model `{canonical}`")
+            });
+            assert_eq!(
+                metadata.auth_env,
+                auth_env.as_str(),
+                "rust/README.md documents `{alias}` as needing `{auth_env}`, but `{canonical}` resolves to provider metadata with auth env `{}`",
+                metadata.auth_env
+            );
+        }
+
+        let documented_aliases: std::collections::BTreeSet<&str> = documented
+            .iter()
+            .map(|(alias, _, _)| alias.as_str())
+            .collect();
+        let resolver_aliases: std::collections::BTreeSet<&str> = super::MODEL_REGISTRY
+            .iter()
+            .map(|(alias, _)| *alias)
+            .collect();
+        assert_eq!(
+            documented_aliases, resolver_aliases,
+            "rust/README.md's `## Model Aliases` table and MODEL_REGISTRY have drifted apart"
+        );
+    }
+
+    // The table documents bare short names only, so the provider-prefixed form
+    // is deliberately *not* an alias. This pins that distinction, since the
+    // prefix is handled later (at request-build time) and a future refactor
+    // could easily fold it into alias resolution.
+    #[test]
+    fn provider_prefixed_alias_is_not_an_alias() {
+        assert_eq!(resolve_model_alias("opus"), "claude-opus-4-7");
+        assert_eq!(resolve_model_alias("anthropic/opus"), "anthropic/opus");
+        assert_eq!(resolve_model_alias("xai/grok"), "xai/grok");
+    }
+
     #[test]
     fn detects_provider_from_model_name_first() {
         assert_eq!(detect_provider_kind("grok"), ProviderKind::Xai);