fix(cli): enforce /v1/completions stop sequences host side for qairt

cli/server/handler/completion.go

@@ -160,9 +160,17 @@ func Completions(c *gin.Context) {
 		return
 	}
 
+	// qairt rejects any generate call that carries stop sequences at all
+	// (sdk/plugins/qairt/src/llm.cpp:219: "--stop / --stop-file (stop
+	// sequences) is not supported by the qairt plugin"). Enforce them host
+	// side instead of forwarding them: withhold Stop from the plugin config
+	// and match the generated text against the requested stop strings as it
+	// comes in, via a stopMatcher.
+	stopSequences := completionStop(req.Stop)
+	hostStop := paths.RuntimeID == geniex_sdk.RuntimeQairt && len(stopSequences) > 0
+
 	genConfig := &geniex_sdk.GenerationConfig{
 		MaxTokens: int32(req.MaxTokens.Value),
-		Stop:      completionStop(req.Stop),
 		SamplerConfig: &geniex_sdk.SamplerConfig{
 			Temperature:       float32(req.Temperature.Value),
 			TopP:              float32(req.TopP.Value),
@@ -174,6 +182,9 @@ func Completions(c *gin.Context) {
 			Seed:              int32(req.Seed.Value),
 		},
 	}
+	if !hostStop {
+		genConfig.Stop = stopSequences
+	}
 	echo := ""
 	if req.Echo.Valid() && req.Echo.Value {
 		echo = prompt
@@ -191,6 +202,11 @@ func Completions(c *gin.Context) {
 			wg      sync.WaitGroup
 		)
 
+		var matcher *stopMatcher
+		if hostStop {
+			matcher = newStopMatcher(stopSequences)
+		}
+
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
@@ -200,8 +216,15 @@ func Completions(c *gin.Context) {
 					if stopGen.Load() {
 						return false
 					}
-					dataCh <- token
-					return true
+					if matcher == nil {
+						dataCh <- token
+						return true
+					}
+					safe, stopped := matcher.feed(token)
+					if safe != "" {
+						dataCh <- safe
+					}
+					return !stopped
 				},
 				Config: genConfig,
 			})
@@ -220,10 +243,23 @@ func Completions(c *gin.Context) {
 		}
 	} else {
 		// blocking
-		out, err := p.Generate(geniex_sdk.LlmGenerateInput{
+		input := geniex_sdk.LlmGenerateInput{
 			PromptUTF8: prompt,
 			Config:     genConfig,
-		})
+		}
+		var text string
+		if hostStop {
+			// No streaming consumer to feed here — the matcher's only job is
+			// to spot the stop sequence and cancel generation early via the
+			// OnToken return value, same as the streaming path.
+			matcher := newStopMatcher(stopSequences)
+			input.OnToken = func(token string) bool {
+				safe, stopped := matcher.feed(token)
+				text += safe
+				return !stopped
+			}
+		}
+		out, err := p.Generate(input)
 		// A prompt that never fit is a client error (400). A window exhausted
 		// mid-generation is a normal truncated completion (finish_reason=length),
 		// so it falls through to the regular response below.
@@ -235,7 +271,10 @@ func Completions(c *gin.Context) {
 			c.JSON(http.StatusInternalServerError, map[string]any{"error": err.Error(), "code": geniex_sdk.SDKErrorCode(err)})
 			return
 		}
-		writeCompletionResponse(c, echo+out.FullText, out.ProfileData)
+		if !hostStop {
+			text = out.FullText
+		}
+		writeCompletionResponse(c, echo+text, out.ProfileData)
 	}
 }
 

cli/server/handler/stop_match.go

@@ -0,0 +1,79 @@
+// Copyright (c) 2026 Qualcomm Technologies, Inc. and/or its subsidiaries.
+// SPDX-License-Identifier: BSD-3-Clause
+
+package handler
+
+import "strings"
+
+// stopMatcher enforces OpenAI-style stop sequences host side, for plugins
+// (qairt) that reject the parameter outright. It buffers just enough of the
+// generated tail to catch a stop sequence split across two token
+// boundaries, without holding back more text than necessary.
+type stopMatcher struct {
+	stops []string
+	buf   string
+}
+
+func newStopMatcher(stops []string) *stopMatcher {
+	return &stopMatcher{stops: stops}
+}
+
+// feed appends token to the internal buffer and returns the portion that is
+// now safe to emit to the client, plus whether a stop sequence has fully
+// matched. Once stopped is true, the caller must cancel generation and stop
+// calling feed — the match itself (and anything after it) is dropped.
+func (m *stopMatcher) feed(token string) (safe string, stopped bool) {
+	m.buf += token
+
+	if idx := firstStopIndex(m.buf, m.stops); idx >= 0 {
+		safe = m.buf[:idx]
+		m.buf = ""
+		return safe, true
+	}
+
+	// Hold back a suffix that could still grow into a stop sequence on the
+	// next token; only the rest is guaranteed clean of any stop sequence.
+	hold := longestStopPrefixSuffixLen(m.buf, m.stops)
+	safe, m.buf = m.buf[:len(m.buf)-hold], m.buf[len(m.buf)-hold:]
+	return safe, false
+}
+
+// firstStopIndex returns the earliest byte offset in buf where a stop
+// sequence starts, or -1 if none has fully matched yet.
+func firstStopIndex(buf string, stops []string) int {
+	idx := -1
+	for _, s := range stops {
+		if s == "" {
+			continue
+		}
+		if i := strings.Index(buf, s); i >= 0 && (idx == -1 || i < idx) {
+			idx = i
+		}
+	}
+	return idx
+}
+
+// longestStopPrefixSuffixLen returns the length of the longest suffix of buf
+// that is also a strict prefix of some stop sequence — the part that must be
+// held back because the next token could still complete a match.
+func longestStopPrefixSuffixLen(buf string, stops []string) int {
+	longest := 0
+	for _, s := range stops {
+		if s == "" {
+			continue
+		}
+		limit := len(s) - 1
+		if limit > len(buf) {
+			limit = len(buf)
+		}
+		for l := limit; l > 0; l-- {
+			if strings.HasSuffix(buf, s[:l]) {
+				if l > longest {
+					longest = l
+				}
+				break
+			}
+		}
+	}
+	return longest
+}

cli/server/handler/stop_match_test.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2026 Qualcomm Technologies, Inc. and/or its subsidiaries.
+// SPDX-License-Identifier: BSD-3-Clause
+
+package handler
+
+import (
+	"strings"
+	"testing"
+)
+
+// feedAll drives a stopMatcher token by token and returns the concatenated
+// safe text plus whether a stop sequence matched, stopping early (as a real
+// caller would) once feed reports a match.
+func feedAll(m *stopMatcher, tokens []string) (string, bool) {
+	var out strings.Builder
+	for _, tok := range tokens {
+		safe, stopped := m.feed(tok)
+		out.WriteString(safe)
+		if stopped {
+			return out.String(), true
+		}
+	}
+	return out.String(), false
+}
+
+func TestStopMatcher(t *testing.T) {
+	tests := []struct {
+		name     string
+		stops    []string
+		tokens   []string
+		wantText string
+		wantStop bool
+	}{
+		{"no stops configured", nil, []string{"hello", " world"}, "hello world", false},
+		{"no match", []string{"STOP"}, []string{"hello", " world"}, "hello world", false},
+		{"match within a single token", []string{"STOP"}, []string{"abc", "defSTOPghi"}, "abcdef", true},
+		{
+			// The FIM repro from #1341: an editor's stop list, split across
+			// streamed token boundaries the way real generation delivers it.
+			"stop sequence split across tokens",
+			[]string{"<fim_prefix>", "<fim_suffix>", "<fim_middle>", "<|endoftext|>"},
+			[]string{"def main():\n    print(", "<fim", "_suffix", ">", ")\n"},
+			"def main():\n    print(",
+			true,
+		},
+		{"earliest of several stops wins", []string{"<fim_suffix>", "<fim_prefix>"}, []string{"abc<fim_prefix>def<fim_suffix>ghi"}, "abc", true},
+		{"empty stop string is ignored", []string{""}, []string{"hello"}, "hello", false},
+		{"match at the very first token", []string{"STOP"}, []string{"STOPtrailing"}, "", true},
+		{"partial match that never completes is still flushed", []string{"<fim_prefix>"}, []string{"abc<fim", "_notit"}, "abc<fim_notit", false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, stopped := feedAll(newStopMatcher(tt.stops), tt.tokens)
+			if got != tt.wantText || stopped != tt.wantStop {
+				t.Errorf("feedAll() = (%q, %v), want (%q, %v)", got, stopped, tt.wantText, tt.wantStop)
+			}
+		})
+	}
+}
+
+func TestStopMatcherHoldsBackAmbiguousSuffix(t *testing.T) {
+	// After a token ending in a proper prefix of the stop sequence, that
+	// prefix must not be emitted yet — the next token could complete it.
+	m := newStopMatcher([]string{"<fim_prefix>"})
+	safe, stopped := m.feed("abc<fim")
+	if safe != "abc" || stopped {
+		t.Fatalf("feed() = (%q, %v), want (\"abc\", false)", safe, stopped)
+	}
+}