diff --git a/docs/ai-coder/agents/chat-search-syntax.md b/docs/ai-coder/agents/chat-search-syntax.md
index 4551c2fd253..bd4f046b489 100644
--- a/docs/ai-coder/agents/chat-search-syntax.md
+++ b/docs/ai-coder/agents/chat-search-syntax.md
@@ -2,22 +2,46 @@
 
 The chat list endpoint accepts a `q` query parameter for filtering
 conversations. All filters use `key:value` syntax. Bare search terms
-are rejected; use `title:` for title filtering.
+are rejected; use `title:` for title filtering or `search:` for
+full-text search.
 
 ## Filters
 
-| Key          | Values                              | Description                                                                                        |
-|--------------|-------------------------------------|----------------------------------------------------------------------------------------------------|
-| `title`      | substring                           | Case-insensitive substring match. Quote multi-word values.                                         |
-| `archived`   | `true`, `false`                     | Filter by archived state. Default: `false`.                                                        |
-| `has_unread` | `true`, `false`                     | Conversations with unread assistant messages.                                                      |
-| `pr_status`  | `draft`, `open`, `merged`, `closed` | Linked pull request state. Comma-separated for OR.                                                 |
-| `diff_url`   | URL                                 | Match by associated diff URL. Quote values containing colons.                                      |
-| `pr`         | positive integer                    | Exact PR number match.                                                                             |
-| `repo`       | substring                           | Case-insensitive substring match against git remote origin or URL. Quote values containing colons. |
-| `pr_title`   | substring                           | Case-insensitive PR title substring match. Quote multi-word values.                                |
-
-Multiple filters in one query combine with AND logic.
+| Key          | Values                              | Description                                                                                               |
+|--------------|-------------------------------------|-----------------------------------------------------------------------------------------------------------|
+| `title`      | substring                           | Case-insensitive substring match. Quote multi-word values.                                                |
+| `archived`   | `true`, `false`                     | Filter by archived state. Default: `false`.                                                               |
+| `has_unread` | `true`, `false`                     | Conversations with unread assistant messages.                                                             |
+| `pr_status`  | `draft`, `open`, `merged`, `closed` | Linked pull request state. Comma-separated for OR.                                                        |
+| `diff_url`   | URL                                 | Match by associated diff URL. Quote values containing colons.                                             |
+| `pr`         | positive integer                    | Exact PR number match.                                                                                    |
+| `repo`       | substring                           | Case-insensitive substring match against git remote origin or URL. Quote values containing colons.        |
+| `pr_title`   | substring                           | Case-insensitive PR title substring match. Quote multi-word values.                                       |
+| `search`     | text                                | Full-text search across chat titles, PR titles, PR numbers, and message content. Quote multi-word values. |
+
+Multiple filters in one query combine with AND logic. `search:` cannot
+be combined with `title:`, `pr_title:`, or `pr:`.
+
+## Full-text search
+
+`search:` uses token-based PostgreSQL full-text search:
+
+- Case-insensitive whole-word matching with AND semantics. Quoted
+  phrases, `OR`, and `-` negation follow
+  [`websearch_to_tsquery`](https://www.postgresql.org/docs/current/textsearch-controls.html#TEXTSEARCH-PARSING-QUERIES)
+  rules.
+- Message content matches English word stems (`refactor` matches
+  `refactoring`) and ignores English stopwords. Titles and PR titles
+  do not stem.
+- No fuzzy, semantic, or prefix matching.
+- Whole-number values also match exact PR numbers.
+- A value with no searchable words (punctuation only) returns an empty
+  list; an empty value returns HTTP 400.
+- Results use the standard chat list ordering (pinned first, then most
+  recently updated) and pagination, without match snippets.
+- Message content becomes searchable shortly after it is written
+  (background indexing, usually within 10 minutes). Titles and PR
+  titles are searchable immediately.
 
 ## Examples
 
@@ -48,6 +72,12 @@ Multiple filters in one query combine with AND logic.
 
 # Conversations with a specific PR title
 ?q=pr_title:"fix auth bug"
+
+# Full-text search across titles, PR titles, and messages
+?q=search:"kubernetes restart"
+
+# Combine full-text search with other filters
+?q=search:refactor+pr_status:open
 ```
 
 ## Notes
@@ -56,4 +86,4 @@ Multiple filters in one query combine with AND logic.
 - `pr_status:draft` means the PR is open **and** marked as a draft.
   `pr_status:open` means the PR is open and not a draft.
 - Conversations without a linked diff status are excluded when `pr_status`, `pr`, `repo`, or `pr_title` is set. The `repo:` filter also matches chats tracking a branch with no PR.
-- Unrecognized keys or bare terms return HTTP 400 with a validation error.
+- Unrecognized keys, bare terms, or combining `search:` with `title:`, `pr_title:`, or `pr:` return HTTP 400 with a validation error.