diff --git a/specs/port/trios/crates/trios-bridge/src/server.t27 b/specs/port/trios/crates/trios-bridge/src/server.t27
new file mode 100644
index 0000000000..05bce968e2
--- /dev/null
+++ b/specs/port/trios/crates/trios-bridge/src/server.t27
@@ -0,0 +1,203 @@
+// WebSocket server for the Trinity Agent Bridge.
+// Port of gHashTag/trios:crates/trios-bridge/src/server.rs
+// (at 8b229e9489ee, 165 lines) — Roadmap Stage 6, goal #4548, target
+// t27c gen-rust.
+//
+// The original runs the agent-bridge WebSocket server: a new server
+// carries its agent router, a broadcast channel with room for 1024
+// queued messages, the GitHub repo and the optional GitHub token; the
+// getters read them back (the token optional, so an absent token
+// answers none); subscribe joins the broadcast; broadcast_message
+// serializes a bridge message and fans it to every subscriber; serve
+// accepts connections, forwarding broadcasts out and dispatching
+// incoming text through handle_message (a Close frame or a stream
+// error ends the read loop, the handshake failure only logs); and
+// handle_message routes by message type — a SendCommand for an agent
+// that is not registered and not the broadcast target answers the
+// agent_not_found error to everyone, otherwise the message forwards;
+// ClaimIssue and UpdateStatus apply to the router and then broadcast
+// the fresh board state; ListAgents answers the board state; anything
+// else forwards unchanged.
+//
+// The WebSocket accept loop, the serialization and the router state
+// are plumbing; the decisions — the 1024-deep broadcast capacity, the
+// token's optionality, the dispatch table with its agent_not_found
+// gate and the three board-refreshing variants — are ported here as
+// pure functions and tested (issue #9121, "Port the decision, not
+// the plumbing").
+
+module port::trios_bridge_server;
+
+// ---------------------------------------------------------------------------
+// Original lines 25-33: `pub fn new(github_repo, github_token)` — the
+// server carries the router, a 1024-slot broadcast channel, the repo
+// and the optional token.
+// ---------------------------------------------------------------------------
+
+pub struct BridgeServerPlan {
+    broadcast_capacity: usize,
+    token_present: bool,
+    repo: str,
+}
+
+pub fn BridgeServer_new(github_repo: str, github_token_present: bool) -> BridgeServerPlan {
+    return BridgeServerPlan {
+        broadcast_capacity: 1024,
+        token_present: github_token_present,
+        repo: github_repo,
+    };
+}
+
+pub fn broadcast_channel_capacity() -> usize {
+    return 1024;
+}
+
+// ---------------------------------------------------------------------------
+// Original lines 36-53: the getters — router, repo, and the optional
+// token answering none when absent; subscribe joins the broadcast.
+// ---------------------------------------------------------------------------
+
+pub fn BridgeServer_router() -> bool {
+    return true;
+}
+
+pub fn BridgeServer_github_repo(plan: BridgeServerPlan) -> str {
+    return plan.repo;
+}
+
+pub fn BridgeServer_github_token(token_present: bool) -> bool {
+    return token_present;
+}
+
+pub fn BridgeServer_subscribe() -> bool {
+    return true;
+}
+
+// ---------------------------------------------------------------------------
+// Original lines 56-60: `broadcast_message` — serialize then fan out;
+// a failed send is tolerated (the `let _`), so the broadcast answers
+// Ok regardless.
+// ---------------------------------------------------------------------------
+
+pub fn BridgeServer_broadcast_message(send_failed: bool) -> bool {
+    return true;
+}
+
+// ---------------------------------------------------------------------------
+// Original lines 63-119: `serve` — the accept loop. The read loop
+// continues on text frames, ends on a Close frame or a stream error,
+// ignores other frame kinds, and a failed handshake only logs (the
+// server keeps accepting).
+// ---------------------------------------------------------------------------
+
+pub fn BridgeServer_serve(handshake_failed: bool) -> bool {
+    return true;
+}
+
+pub fn read_loop_continues(frame_kind: str) -> bool {
+    if (frame_kind == "text") {
+        return true;
+    }
+    if (frame_kind == "close") {
+        return false;
+    }
+    if (frame_kind == "error") {
+        return false;
+    }
+    return true;
+}
+
+// ---------------------------------------------------------------------------
+// Original lines 122-165: `handle_message` — the dispatch table. The
+// SendCommand gate: a target that is neither the broadcast literal nor
+// a registered agent answers the agent_not_found error broadcast;
+// otherwise the message forwards. ClaimIssue and UpdateStatus apply
+// and refresh the board state for everyone; ListAgents answers the
+// board state; anything else forwards unchanged.
+// ---------------------------------------------------------------------------
+
+pub const BROADCAST_TARGET: str = "broadcast";
+
+pub fn BridgeServer_handle_message(msg_kind: str, target: str, target_registered: bool) -> str {
+    if (msg_kind == "send_command") {
+        if (target != BROADCAST_TARGET and !target_registered) {
+            return "agent_not_found";
+        }
+        return "forward";
+    }
+    if (msg_kind == "claim_issue") {
+        return "apply_and_board";
+    }
+    if (msg_kind == "update_status") {
+        return "apply_and_board";
+    }
+    if (msg_kind == "list_agents") {
+        return "board_state";
+    }
+    return "forward";
+}
+
+pub fn agent_not_found_error_code() -> str {
+    return "agent_not_found";
+}
+
+// ---------------------------------------------------------------------------
+// Tests: every decision above asserted against values read from the
+// original.
+// ---------------------------------------------------------------------------
+
+test new_carries_capacity_repo_and_token {
+    const with_token = BridgeServer_new("gHashTag/trios", true);
+    assert(with_token.broadcast_capacity == 1024);
+    assert(with_token.token_present);
+    assert(with_token.repo == "gHashTag/trios");
+    const without_token = BridgeServer_new("gHashTag/t27", false);
+    assert(!without_token.token_present);
+    assert(broadcast_channel_capacity() == 1024);
+}
+
+test getters_read_back {
+    const plan = BridgeServer_new("gHashTag/trios", false);
+    assert(BridgeServer_router());
+    assert(BridgeServer_github_repo(plan) == "gHashTag/trios");
+    assert(!BridgeServer_github_token(false));
+    assert(BridgeServer_github_token(true));
+    assert(BridgeServer_subscribe());
+}
+
+test broadcast_tolerates_failed_sends {
+    assert(BridgeServer_broadcast_message(false));
+    assert(BridgeServer_broadcast_message(true));
+}
+
+test serve_accepts_past_failures {
+    assert(BridgeServer_serve(true));
+    assert(BridgeServer_serve(false));
+}
+
+test read_loop_frame_rules {
+    assert(read_loop_continues("text"));
+    assert(!read_loop_continues("close"));
+    assert(!read_loop_continues("error"));
+    assert(read_loop_continues("ping"));
+}
+
+test broadcast_target_literal {
+    assert(BROADCAST_TARGET == "broadcast");
+}
+
+test send_command_gate {
+    assert(BridgeServer_handle_message("send_command", "broadcast", false) == "forward");
+    assert(BridgeServer_handle_message("send_command", "agent-7", true) == "forward");
+    assert(BridgeServer_handle_message("send_command", "agent-7", false) == "agent_not_found");
+    assert(BridgeServer_handle_message("send_command", "broadcast", true) == "forward");
+    assert(agent_not_found_error_code() == "agent_not_found");
+}
+
+test dispatch_table_variants {
+    assert(BridgeServer_handle_message("claim_issue", "", true) == "apply_and_board");
+    assert(BridgeServer_handle_message("update_status", "", true) == "apply_and_board");
+    assert(BridgeServer_handle_message("list_agents", "", true) == "board_state");
+    assert(BridgeServer_handle_message("unknown_kind", "", true) == "forward");
+    assert(BridgeServer_handle_message("board_state", "", true) == "forward");
+}