refactor(execenv): scope MUST-stdin mandate back to Codex-only

Followup to #2247: roll back the over-spread of #1795 / #1851. Both PRs
were intended to fix Codex's habit of emitting literal `\n` inside
`--content "..."` (MUL-1467), but the implementation landed strong
"MUST pipe via stdin" / `--description-stdin` directives in the
all-provider Available Commands section AND in the provider-agnostic
`BuildCommentReplyInstructions` helper. That global mandate then broke
non-ASCII bytes for every provider on Windows shells (#2198 / #2236),
because PowerShell 5.1 / cmd.exe re-encode piped HEREDOC bytes through
the active console codepage and silently drop non-representable bytes
as `?`.

Three concrete changes:

- `runtime_config.go` Available Commands: replace the platform-branched
  "MUST pipe via stdin" block with a neutral three-line description of
  the three input modes (`--content`, `--content-stdin`,
  `--content-file`). Same text on every host, no GOOS branch. The
  `--content-file` line still flags the Windows-shell-codepage caveat
  in passing so an agent that picks stdin and lands on Win11 has a
  pointer to file as the safe fallback, but no provider gets a "MUST"
  here anymore.

- `BuildCommentReplyInstructions`: add a `provider` parameter. Codex
  keeps the platform-aware mandate (Windows → file, non-Windows →
  stdin/HEREDOC) — the original MUL-1467 fix lives where it belongs.
  Every other provider gets the lightweight pre-#1795 inline template
  (`--content "..."` with a pointer to stdin/file for richer
  formatting); the CLI's `util.UnescapeBackslashEscapes` still decodes
  `\n` server-side so multi-line inline works on every platform, and
  argv goes through CreateProcessW UTF-16 on Windows so non-ASCII
  survives.

- Plumbing: thread `provider` through `BuildPrompt` →
  `buildCommentPrompt` → `execenv.BuildCommentReplyInstructions`. Sole
  caller is `daemon.runTask`, where `provider` is already in scope.

Test rework:

- `TestInjectRuntimeConfigDirectsMultiLineWritesToStdin` is replaced by
  `TestInjectRuntimeConfigAvailableCommandsIsNeutral`, which sweeps every
  non-Codex provider × every host OS and pins (a) the three-mode menu is
  present, (b) the over-spread substrings (`MUST pipe via stdin`,
  `Agent-authored comments should always pipe content via stdin`,
  `use --description-stdin and pipe a HEREDOC`) are GONE.
- `TestInjectRuntimeConfigWindowsRecommendsContentFile` becomes
  `TestInjectRuntimeConfigCodexWindowsRecommendsContentFile`, scoped to
  the Codex section. Linux Codex still pins `always use --content-stdin
  with a HEREDOC` so the original MUL-1467 protection isn't dropped.
- `TestBuildCommentReplyInstructionsIncludesTriggerID` becomes
  `TestBuildCommentReplyInstructionsCodexLinux` (codex/linux still gets
  stdin) plus a new
  `TestBuildCommentReplyInstructionsNonCodexUsesInline` that sweeps
  claude / opencode / openclaw / hermes / kimi / kiro / cursor / gemini
  on linux / darwin / windows and pins the inline template, with a ban
  on the codex-specific stdin/file substrings.
- `TestBuildCommentReplyInstructionsCodexWindowsUsesContentFile` and
  `TestInjectRuntimeConfigCodexWindowsCommentTriggerHasNoStdin` keep
  the Windows file-first end-to-end pin for codex.
- `BuildPrompt` callers in daemon_test.go updated for the new
  `provider` arg.

Net effect: Windows non-Codex agents (Claude / Opencode / Hermes /
etc.) on Win11 stop getting steered at the broken stdin path entirely;
Codex on Windows stays on `--content-file`; Codex on Linux/macOS keeps
its MUL-1467 protection; every other provider's CLAUDE.md / AGENTS.md
loses the "MUST stdin" mandate it never needed.

Co-authored-by: multica-agent <github@multica.ai>

server/internal/daemon/daemon.go

@@ -1621,7 +1621,7 @@ func (d *Daemon) runTask(ctx context.Context, task Task, provider string, slot i
 	// the same (agent, issue) pair. The work_dir path is stored in DB on
 	// task completion and passed back via PriorWorkDir on the next claim.
 
-	prompt := BuildPrompt(task)
+	prompt := BuildPrompt(task, provider)
 
 	// Pass the daemon's auth credentials and context so the spawned agent CLI
 	// can call the Multica API and the local daemon (e.g. `multica repo checkout`).

server/internal/daemon/daemon_test.go

@@ -101,7 +101,7 @@ func TestBuildPromptContainsIssueID(t *testing.T) {
 				{Name: "Concise", Content: "Be concise."},
 			},
 		},
-	})
+	}, "claude")
 
 	// Prompt should contain the issue ID and CLI hint.
 	for _, want := range []string{
@@ -127,7 +127,7 @@ func TestBuildPromptNoIssueDetails(t *testing.T) {
 	prompt := BuildPrompt(Task{
 		IssueID: "test-id",
 		Agent:   &AgentData{Name: "Test"},
-	})
+	}, "claude")
 
 	// Prompt should not contain issue title/description (agent fetches via CLI).
 	for _, absent := range []string{"**Issue:**", "**Summary:**"} {
@@ -146,7 +146,7 @@ func TestBuildPromptAutopilotRunOnly(t *testing.T) {
 		AutopilotTitle:       "Daily dependency check",
 		AutopilotDescription: "Check dependencies and report outdated packages.",
 		AutopilotSource:      "manual",
-	})
+	}, "claude")
 
 	for _, want := range []string{
 		"run-only mode",
@@ -178,7 +178,7 @@ func TestBuildPromptCommentTriggered(t *testing.T) {
 		TriggerCommentID:      commentID,
 		TriggerCommentContent: commentContent,
 		Agent:                 &AgentData{Name: "Test"},
-	})
+	}, "claude")
 
 	// Prompt should contain the comment content, the trigger comment id, and
 	// the full reply command with --parent. Re-emitting --parent on every turn
@@ -223,7 +223,7 @@ func TestBuildPromptCommentTriggeredByAgent(t *testing.T) {
 		TriggerAuthorType:     "agent",
 		TriggerAuthorName:     "Atlas",
 		Agent:                 &AgentData{Name: "Test"},
-	})
+	}, "claude")
 
 	for _, want := range []string{
 		"Another agent (Atlas)",
@@ -249,7 +249,7 @@ func TestBuildPromptCommentTriggeredByMember(t *testing.T) {
 		TriggerAuthorType:     "member",
 		TriggerAuthorName:     "Alice",
 		Agent:                 &AgentData{Name: "Test"},
-	})
+	}, "claude")
 
 	if !strings.Contains(prompt, "A user just left a new comment") {
 		t.Fatalf("member-triggered prompt should label the author as a user\n---\n%s", prompt)
@@ -278,7 +278,7 @@ func TestBuildPromptCommentTriggeredNoContent(t *testing.T) {
 		IssueID:          "test-id",
 		TriggerCommentID: "comment-id",
 		Agent:            &AgentData{Name: "Test"},
-	})
+	}, "claude")
 
 	if !strings.Contains(prompt, "multica issue get") {
 		t.Fatal("prompt missing CLI hint")

server/internal/daemon/execenv/execenv_test.go

@@ -982,59 +982,96 @@ func TestInjectRuntimeConfigRequiresExplicitCommentPost(t *testing.T) {
 	}
 }
 
-// TestInjectRuntimeConfigDirectsMultiLineWritesToStdin pins the guidance that
-// any multi-line content for `multica issue comment add` must go through
-// `--content-stdin` + a HEREDOC. Agents that reached for the inline
-// `--content "...\n\n..."` form ended up with literal 4-char `\n` sequences
-// in stored comments because bash does not expand backslash escapes inside
-// double quotes; see MUL-1467. This test prevents the multi-line guidance
-// from silently regressing back into a "for special characters" footnote.
+// TestInjectRuntimeConfigAvailableCommandsIsNeutral pins that the global
+// Available Commands section lists the three input modes neutrally for
+// every provider, with no "MUST pipe via stdin" mandate.
+//
+// Background: #1795 / #1851 introduced "MUST pipe via stdin" /
+// `--description-stdin` directives in the global section to fix Codex's
+// habit of emitting literal `\n` inside `--content "..."` (MUL-1467).
+// That mandate landed in the all-provider section and ended up steering
+// every provider at stdin — which then broke non-ASCII bytes on Windows
+// shells (#2198 / #2236). This rollback keeps the strong Codex-specific
+// mandate in the Codex-Specific section (pinned by
+// TestInjectRuntimeConfigCodexEmphasizesStdinForFormattedComments) and
+// leaves the global section neutral. Pinning the neutrality here so a
+// future refactor can't accidentally re-introduce the over-spread.
 //
-// Pins runtimeGOOS to "linux" so the test is deterministic regardless of
-// the host OS the test runner is on; the Windows branch has a separate
-// file-first contract pinned by TestInjectRuntimeConfigWindowsRecommendsContentFile.
 // Not parallel: mutates the package-level runtimeGOOS.
-func TestInjectRuntimeConfigDirectsMultiLineWritesToStdin(t *testing.T) {
+func TestInjectRuntimeConfigAvailableCommandsIsNeutral(t *testing.T) {
 	saved := runtimeGOOS
 	t.Cleanup(func() { runtimeGOOS = saved })
-	runtimeGOOS = "linux"
 
-	dir := t.TempDir()
-	if err := InjectRuntimeConfig(dir, "claude", TaskContextForEnv{IssueID: "issue-1"}); err != nil {
-		t.Fatalf("InjectRuntimeConfig failed: %v", err)
-	}
-	data, err := os.ReadFile(filepath.Join(dir, "CLAUDE.md"))
-	if err != nil {
-		t.Fatalf("read CLAUDE.md: %v", err)
-	}
-	s := string(data)
+	for _, host := range []string{"linux", "darwin", "windows"} {
+		for _, provider := range []string{"claude", "opencode", "openclaw", "hermes", "kimi", "kiro", "cursor", "gemini"} {
+			t.Run(provider+"/"+host, func(t *testing.T) {
+				runtimeGOOS = host
+				dir := t.TempDir()
+				if err := InjectRuntimeConfig(dir, provider, TaskContextForEnv{IssueID: "issue-1"}); err != nil {
+					t.Fatalf("InjectRuntimeConfig failed: %v", err)
+				}
 
-	for _, want := range []string{
-		"multi-line content",
-		"MUST pipe via stdin",
-		"--content-stdin",
-		"<<'COMMENT'",
-		"`--description`",
-		"--description-stdin",
-	} {
-		if !strings.Contains(s, want) {
-			t.Errorf("CLAUDE.md missing multi-line guidance %q\n---\n%s", want, s)
+				configFile := "CLAUDE.md"
+				if provider != "claude" {
+					configFile = "AGENTS.md"
+				}
+				if provider == "gemini" {
+					configFile = "GEMINI.md"
+				}
+				data, err := os.ReadFile(filepath.Join(dir, configFile))
+				if err != nil {
+					t.Fatalf("read %s: %v", configFile, err)
+				}
+				s := string(data)
+
+				// Available Commands lists all three input modes as fact.
+				for _, want := range []string{
+					"`--content \"...\"`",
+					"`--content-stdin`",
+					"`--content-file <path>`",
+					"`--description-stdin`",
+					"`--description-file <path>`",
+				} {
+					if !strings.Contains(s, want) {
+						t.Errorf("%s missing flag mention %q\n---\n%s", configFile, want, s)
+					}
+				}
+
+				// "MUST pipe via stdin" must NOT appear in any non-Codex
+				// provider's runtime config: it was the over-spread of
+				// the Codex-specific fix.
+				for _, banned := range []string{
+					"MUST pipe via stdin",
+					"Agent-authored comments should always pipe content via stdin",
+					"use `--description-stdin` and pipe a HEREDOC",
+				} {
+					if strings.Contains(s, banned) {
+						t.Errorf("%s carries over-spread Codex mandate %q for non-Codex provider %s\n---\n%s", configFile, banned, provider, s)
+					}
+				}
+			})
 		}
 	}
 }
 
-// TestInjectRuntimeConfigWindowsRecommendsContentFile pins the Windows-specific
-// rewrite added after issues #2198 / #2236: agent-authored comments arrive
-// as `?` because Windows PowerShell 5.1 and cmd.exe re-encode piped HEREDOC
-// bytes through the active console codepage, dropping non-ASCII bytes
-// before they reach `multica`. The Windows comment/description block is
-// rewritten file-first — there is no preceding "MUST pipe via stdin" /
-// `--description-stdin` directive that could override it.
-func TestInjectRuntimeConfigWindowsRecommendsContentFile(t *testing.T) {
+// TestInjectRuntimeConfigCodexWindowsRecommendsContentFile pins the
+// Windows-specific Codex carve-out: on Windows the Codex-Specific section
+// directs the agent at `--content-file` instead of `--content-stdin`,
+// because Windows PowerShell 5.1 / cmd.exe re-encode piped HEREDOC bytes
+// through the active console codepage and silently drop non-ASCII as `?`
+// before reaching `multica.exe` (#2198 / #2236). On non-Windows hosts the
+// Codex section keeps the canonical stdin/HEREDOC mandate.
+//
+// The Available Commands section is provider-neutral and lists all three
+// input modes regardless of host — its neutrality is pinned separately by
+// TestInjectRuntimeConfigAvailableCommandsIsNeutral.
+//
+// Not parallel: mutates the package-level runtimeGOOS.
+func TestInjectRuntimeConfigCodexWindowsRecommendsContentFile(t *testing.T) {
 	saved := runtimeGOOS
 	t.Cleanup(func() { runtimeGOOS = saved })
 
-	t.Run("windows host emits the file-first block", func(t *testing.T) {
+	t.Run("codex/windows points at --content-file", func(t *testing.T) {
 		runtimeGOOS = "windows"
 		dir := t.TempDir()
 		if err := InjectRuntimeConfig(dir, "codex", TaskContextForEnv{IssueID: "issue-1"}); err != nil {
@@ -1046,39 +1083,31 @@ func TestInjectRuntimeConfigWindowsRecommendsContentFile(t *testing.T) {
 		}
 		s := string(data)
 		for _, want := range []string{
-			"On this Windows host",
+			"On Windows, **always write the comment body to a UTF-8 file",
 			"console codepage",
 			"--content-file",
-			"--description-file",
 			"silently drop non-ASCII characters as `?`",
 		} {
 			if !strings.Contains(s, want) {
-				t.Errorf("AGENTS.md missing Windows file-first guidance %q\n---\n%s", want, s)
+				t.Errorf("AGENTS.md missing Codex/Windows file-first guidance %q\n---\n%s", want, s)
 			}
 		}
 
-		// The Windows block must NOT carry over any prescriptive
-		// "use stdin" / "pipe a HEREDOC" directive: GPT-Boy's review noted
-		// that even a Windows caveat appended after MUST-stdin lines sets
-		// up a conflicting instruction the agent can latch onto. The
-		// Windows branch is now file-first; stdin appears only in
-		// anti-prescriptive prose like "do NOT pipe via `--content-stdin`",
-		// so the assertions below pin the prescriptive phrasings, not the
-		// bare flag names.
+		// On Windows the Codex section must NOT prescribe stdin — that's
+		// the exact path the Windows console codepage mangles. Pin the
+		// prescriptive phrasings (sentence-level), not bare flag names,
+		// so anti-prescriptive prose like "do NOT pipe via
+		// `--content-stdin`" doesn't trip the ban.
 		for _, banned := range []string{
-			"MUST pipe via stdin",
-			"use `--description-stdin` and pipe a HEREDOC",
-			"<<'COMMENT'",
-			"Agent-authored comments should always pipe content via stdin",
-			"always use `--content-stdin`",
+			"always use `--content-stdin` with a HEREDOC, even for short single-line replies",
 		} {
 			if strings.Contains(s, banned) {
-				t.Errorf("AGENTS.md still carries non-Windows stdin directive %q on Windows\n---\n%s", banned, s)
+				t.Errorf("AGENTS.md still carries Codex stdin mandate %q on Windows\n---\n%s", banned, s)
 			}
 		}
 	})
 
-	t.Run("non-windows host keeps the stdin-first block", func(t *testing.T) {
+	t.Run("codex/linux keeps the stdin-first Codex section", func(t *testing.T) {
 		runtimeGOOS = "linux"
 		dir := t.TempDir()
 		if err := InjectRuntimeConfig(dir, "codex", TaskContextForEnv{IssueID: "issue-1"}); err != nil {
@@ -1089,21 +1118,20 @@ func TestInjectRuntimeConfigWindowsRecommendsContentFile(t *testing.T) {
 			t.Fatalf("read AGENTS.md: %v", err)
 		}
 		s := string(data)
-		if strings.Contains(s, "On this Windows host") {
-			t.Errorf("AGENTS.md should not surface Windows guidance when host is %s", runtimeGOOS)
-		}
-		// On Linux the stdin/HEREDOC contract is the canonical multi-line
-		// guidance — pin that it is still present so we can't accidentally
-		// kill it for non-Windows hosts in a future refactor.
+		// On Linux the Codex section keeps the canonical stdin/HEREDOC
+		// mandate — pin it so a future refactor can't accidentally drop
+		// the protection that originally fixed MUL-1467.
 		for _, want := range []string{
-			"MUST pipe via stdin",
-			"--content-stdin",
-			"--description-stdin",
+			"always use `--content-stdin` with a HEREDOC",
+			"Never use inline `--content` for agent-authored comments",
 		} {
 			if !strings.Contains(s, want) {
-				t.Errorf("AGENTS.md missing Linux stdin guidance %q\n---\n%s", want, s)
+				t.Errorf("AGENTS.md missing Codex/Linux stdin mandate %q\n---\n%s", want, s)
 			}
 		}
+		if strings.Contains(s, "On Windows, **always write the comment body to a UTF-8 file") {
+			t.Errorf("AGENTS.md should not surface Windows codex guidance on linux host\n---\n%s", s)
+		}
 	})
 }
 

server/internal/daemon/execenv/reply_instructions.go

@@ -12,42 +12,68 @@ import "fmt"
 // because resumed Claude sessions keep prior turns' tool calls in context
 // and will otherwise copy the old --parent UUID forward.
 //
-// On Windows the template switches to `--content-file` because piping a
-// HEREDOC through PowerShell 5.1 / cmd.exe re-encodes the bytes via the
-// active console codepage, dropping non-ASCII characters as `?` before they
-// reach `multica.exe` — see issues #2198 / #2236. Reading the body off disk
-// preserves UTF-8 verbatim.
-func BuildCommentReplyInstructions(issueID, triggerCommentID string) string {
+// The template is provider-aware. The strong "use stdin / use file" mandate
+// originated from #1795 / #1851 to fix Codex's habit of emitting literal
+// `\n` escapes inside `--content "..."`. Other providers handle inline
+// escaping correctly (the CLI's `util.UnescapeBackslashEscapes` decodes
+// `\n` server-side anyway), so they get the original lightweight inline
+// template that worked on every platform — including Windows non-ASCII,
+// where argv goes through CreateProcessW UTF-16 and bytes survive intact.
+//
+// Codex on Windows must use `--content-file` because piping a HEREDOC
+// through PowerShell 5.1 / cmd.exe re-encodes bytes via the active console
+// codepage and drops non-ASCII as `?` before reaching `multica.exe` —
+// see issues #2198 / #2236.
+func BuildCommentReplyInstructions(provider, issueID, triggerCommentID string) string {
 	if triggerCommentID == "" {
 		return ""
 	}
-	if runtimeGOOS == "windows" {
+	if provider == "codex" {
+		if runtimeGOOS == "windows" {
+			return fmt.Sprintf(
+				"If you decide to reply, post it as a comment — always use the trigger comment ID below, "+
+					"do NOT reuse --parent values from previous turns in this session.\n\n"+
+					"On Windows, write the reply body to a UTF-8 file with your file-write tool, then post it with `--content-file`. "+
+					"Do NOT pipe via `--content-stdin` — Windows PowerShell 5.1 and cmd.exe re-encode piped bytes through the active console codepage and silently drop non-ASCII characters as `?`. "+
+					"Do NOT use inline `--content`; it is easy to lose formatting or accidentally compress a structured reply into one line.\n\n"+
+					"Use this form, preserving the same issue ID and --parent value:\n\n"+
+					"    # 1. Write the reply body to a UTF-8 file (e.g. reply.md) with your file-write tool.\n"+
+					"    # 2. Then run:\n"+
+					"    multica issue comment add %s --parent %s --content-file ./reply.md\n\n"+
+					"Do NOT write literal `\\n` escapes to simulate line breaks; the file preserves real newlines.\n",
+				issueID, triggerCommentID,
+			)
+		}
 		return fmt.Sprintf(
 			"If you decide to reply, post it as a comment — always use the trigger comment ID below, "+
 				"do NOT reuse --parent values from previous turns in this session.\n\n"+
-				"On Windows, write the reply body to a UTF-8 file with your file-write tool, then post it with `--content-file`. "+
-				"Do NOT pipe via `--content-stdin` — Windows PowerShell 5.1 and cmd.exe re-encode piped bytes through the active console codepage and silently drop non-ASCII characters as `?`. "+
+				"Always use `--content-stdin` with a HEREDOC for agent-authored issue comments, even when the reply is a single line. "+
 				"Do NOT use inline `--content`; it is easy to lose formatting or accidentally compress a structured reply into one line.\n\n"+
 				"Use this form, preserving the same issue ID and --parent value:\n\n"+
-				"    # 1. Write the reply body to a UTF-8 file (e.g. reply.md) with your file-write tool.\n"+
-				"    # 2. Then run:\n"+
-				"    multica issue comment add %s --parent %s --content-file ./reply.md\n\n"+
-				"Do NOT write literal `\\n` escapes to simulate line breaks; the file preserves real newlines.\n",
+				"    cat <<'COMMENT' | multica issue comment add %s --parent %s --content-stdin\n"+
+				"    First paragraph.\n"+
+				"\n"+
+				"    Second paragraph.\n"+
+				"    COMMENT\n\n"+
+				"Do NOT write literal `\\n` escapes to simulate line breaks; the HEREDOC preserves real newlines.\n",
 			issueID, triggerCommentID,
 		)
 	}
+	// Non-Codex providers: lightweight inline template, no platform branch.
+	// Pre-#1795 default, restored after we found that #1795 / #1851 had
+	// expanded a Codex-specific fix into a global mandate that broke
+	// Windows non-ASCII for every provider. The CLI decodes `\n` etc.
+	// server-side, so escaped multi-line is fine; for richer formatting
+	// the agent can still reach for `--content-stdin` (works on Linux /
+	// macOS) or `--content-file <path>` (works on every platform), both
+	// listed in Available Commands above.
 	return fmt.Sprintf(
 		"If you decide to reply, post it as a comment — always use the trigger comment ID below, "+
 			"do NOT reuse --parent values from previous turns in this session.\n\n"+
-			"Always use `--content-stdin` with a HEREDOC for agent-authored issue comments, even when the reply is a single line. "+
-			"Do NOT use inline `--content`; it is easy to lose formatting or accidentally compress a structured reply into one line.\n\n"+
 			"Use this form, preserving the same issue ID and --parent value:\n\n"+
-			"    cat <<'COMMENT' | multica issue comment add %s --parent %s --content-stdin\n"+
-			"    First paragraph.\n"+
-			"\n"+
-			"    Second paragraph.\n"+
-			"    COMMENT\n\n"+
-			"Do NOT write literal `\\n` escapes to simulate line breaks; the HEREDOC preserves real newlines.\n",
+			"    multica issue comment add %s --parent %s --content \"...\"\n\n"+
+			"For multi-line bodies, code blocks, or content with quotes/backticks, prefer `--content-stdin` "+
+			"(pipe a HEREDOC) or `--content-file <path>` (read a UTF-8 file). See Available Commands above for the full menu.\n",
 		issueID, triggerCommentID,
 	)
 }

server/internal/daemon/execenv/reply_instructions_test.go

@@ -7,10 +7,14 @@ import (
 	"testing"
 )
 
-// Pins runtimeGOOS to "linux": the Windows reply template has its own
-// dedicated test (TestBuildCommentReplyInstructionsWindowsUsesContentFile).
+// TestBuildCommentReplyInstructionsCodexLinux pins that the strong
+// "MUST use --content-stdin + HEREDOC" mandate is alive for Codex on
+// non-Windows hosts. Codex's habit of emitting literal `\n` inside
+// `--content "..."` is the original reason this mandate exists
+// (#1795 / #1851); on Linux/macOS stdin is the right answer.
+//
 // Not parallel: mutates the package-level runtimeGOOS.
-func TestBuildCommentReplyInstructionsIncludesTriggerID(t *testing.T) {
+func TestBuildCommentReplyInstructionsCodexLinux(t *testing.T) {
 	saved := runtimeGOOS
 	t.Cleanup(func() { runtimeGOOS = saved })
 	runtimeGOOS = "linux"
@@ -18,37 +22,93 @@ func TestBuildCommentReplyInstructionsIncludesTriggerID(t *testing.T) {
 	issueID := "11111111-1111-1111-1111-111111111111"
 	triggerID := "22222222-2222-2222-2222-222222222222"
 
-	got := BuildCommentReplyInstructions(issueID, triggerID)
+	got := BuildCommentReplyInstructions("codex", issueID, triggerID)
 
 	for _, want := range []string{
-		"multica issue comment add " + issueID + " --parent " + triggerID,
+		"multica issue comment add " + issueID + " --parent " + triggerID + " --content-stdin",
 		"Always use `--content-stdin`",
 		"even when the reply is a single line",
-		"--content-stdin",
 		"<<'COMMENT'",
 		"Do NOT write literal `\\n` escapes to simulate line breaks",
 		"do NOT reuse --parent values from previous turns",
 	} {
 		if !strings.Contains(got, want) {
-			t.Fatalf("reply instructions missing %q\n---\n%s", want, got)
+			t.Fatalf("codex/linux reply instructions missing %q\n---\n%s", want, got)
 		}
 	}
 
 	if strings.Contains(got, "--content \"...\"") {
-		t.Fatalf("reply instructions should not offer inline --content form\n---\n%s", got)
+		t.Fatalf("codex reply instructions should not offer inline --content form\n---\n%s", got)
+	}
+}
+
+// TestBuildCommentReplyInstructionsNonCodexUsesInline pins that every
+// non-Codex provider gets the lightweight pre-#1795 inline template,
+// regardless of host OS. The "MUST stdin" mandate was originally a
+// Codex-specific fix that #1795 / #1851 accidentally spread to every
+// provider — and on Windows that spread broke non-ASCII bytes via the
+// console codepage (#2198 / #2236). Non-Codex providers handle inline
+// escaping correctly and the CLI server-decodes `\n` etc., so the
+// inline template works on every platform including Windows non-ASCII
+// (argv goes through CreateProcessW UTF-16).
+//
+// Not parallel: mutates the package-level runtimeGOOS.
+func TestBuildCommentReplyInstructionsNonCodexUsesInline(t *testing.T) {
+	saved := runtimeGOOS
+	t.Cleanup(func() { runtimeGOOS = saved })
+
+	issueID := "11111111-1111-1111-1111-111111111111"
+	triggerID := "22222222-2222-2222-2222-222222222222"
+
+	for _, host := range []string{"linux", "darwin", "windows"} {
+		for _, provider := range []string{"claude", "opencode", "openclaw", "hermes", "kimi", "kiro", "cursor", "gemini"} {
+			name := provider + "/" + host
+			t.Run(name, func(t *testing.T) {
+				runtimeGOOS = host
+				got := BuildCommentReplyInstructions(provider, issueID, triggerID)
+
+				for _, want := range []string{
+					"multica issue comment add " + issueID + " --parent " + triggerID + " --content \"...\"",
+					"do NOT reuse --parent values from previous turns",
+					"If you decide to reply",
+				} {
+					if !strings.Contains(got, want) {
+						t.Errorf("%s reply instructions missing %q\n---\n%s", name, want, got)
+					}
+				}
+
+				// Non-Codex providers must NOT receive the Codex-specific
+				// "MUST stdin" mandate or its HEREDOC template, even on
+				// Linux/macOS — that was the over-spread of #1795 / #1851.
+				for _, banned := range []string{
+					"Always use `--content-stdin`",
+					"<<'COMMENT'",
+					"--parent " + triggerID + " --content-stdin",
+					"--parent " + triggerID + " --content-file",
+				} {
+					if strings.Contains(got, banned) {
+						t.Errorf("%s reply instructions still steers at codex template: %q\n---\n%s", name, banned, got)
+					}
+				}
+			})
+		}
 	}
 }
 
 func TestBuildCommentReplyInstructionsEmptyWhenNoTrigger(t *testing.T) {
 	t.Parallel()
 
-	if got := BuildCommentReplyInstructions("issue-id", ""); got != "" {
+	if got := BuildCommentReplyInstructions("codex", "issue-id", ""); got != "" {
+		t.Fatalf("expected empty string when triggerCommentID is empty, got %q", got)
+	}
+	if got := BuildCommentReplyInstructions("claude", "issue-id", ""); got != "" {
 		t.Fatalf("expected empty string when triggerCommentID is empty, got %q", got)
 	}
 }
 
 // Pins runtimeGOOS to "linux" so the helper output is deterministic.
-// Not parallel: mutates the package-level runtimeGOOS.
+// Provider is "claude" — exercises the non-codex inline path through
+// InjectRuntimeConfig end-to-end. Not parallel: mutates runtimeGOOS.
 func TestInjectRuntimeConfigCommentTriggerUsesHelper(t *testing.T) {
 	saved := runtimeGOOS
 	t.Cleanup(func() { runtimeGOOS = saved })
@@ -84,73 +144,55 @@ func TestInjectRuntimeConfigCommentTriggerUsesHelper(t *testing.T) {
 	}
 }
 
-// TestBuildCommentReplyInstructionsWindowsUsesContentFile pins that on Windows
-// hosts every per-turn reply prompt — and the workflow block in CLAUDE.md /
-// AGENTS.md — points agents at `--content-file` instead of `--content-stdin`.
-// Without this, the Windows console codepage re-encodes piped HEREDOC bytes
-// and silently drops non-ASCII characters as `?` before they reach
-// `multica.exe` (issues #2198, #2236).
+// TestBuildCommentReplyInstructionsCodexWindowsUsesContentFile pins that on
+// Windows hosts the Codex per-turn reply template points at
+// `--content-file` instead of `--content-stdin`. PowerShell 5.1 / cmd.exe
+// re-encode piped HEREDOC bytes through the active console codepage and
+// silently drop non-ASCII characters as `?` before they reach
+// `multica.exe` (issues #2198 / #2236).
 //
-// Not parallel: mutates the package-level `runtimeGOOS`. Restores it via
-// t.Cleanup so any subsequent `t.Parallel()` tests see the original value.
-func TestBuildCommentReplyInstructionsWindowsUsesContentFile(t *testing.T) {
+// Not parallel: mutates the package-level runtimeGOOS.
+func TestBuildCommentReplyInstructionsCodexWindowsUsesContentFile(t *testing.T) {
 	saved := runtimeGOOS
 	t.Cleanup(func() { runtimeGOOS = saved })
 
 	issueID := "11111111-1111-1111-1111-111111111111"
 	triggerID := "22222222-2222-2222-2222-222222222222"
 
-	t.Run("windows host points at --content-file", func(t *testing.T) {
+	t.Run("codex/windows points at --content-file", func(t *testing.T) {
 		runtimeGOOS = "windows"
-		got := BuildCommentReplyInstructions(issueID, triggerID)
+		got := BuildCommentReplyInstructions("codex", issueID, triggerID)
 		for _, want := range []string{
 			"multica issue comment add " + issueID + " --parent " + triggerID + " --content-file",
-			"--content-file",
 			"On Windows, write the reply body to a UTF-8 file",
 			"Do NOT pipe via `--content-stdin`",
 			"silently drop non-ASCII characters as `?`",
 		} {
 			if !strings.Contains(got, want) {
-				t.Errorf("Windows reply instructions missing %q\n---\n%s", want, got)
+				t.Errorf("codex/windows reply instructions missing %q\n---\n%s", want, got)
 			}
 		}
 		for _, banned := range []string{
 			"<<'COMMENT'",
-			"--content-stdin\n",
+			"--parent " + triggerID + " --content-stdin",
 			"cat <<",
 		} {
 			if strings.Contains(got, banned) {
-				t.Errorf("Windows reply instructions should not contain %q\n---\n%s", banned, got)
+				t.Errorf("codex/windows reply instructions should not contain %q\n---\n%s", banned, got)
 			}
 		}
 	})
-
-	t.Run("non-windows host keeps --content-stdin HEREDOC", func(t *testing.T) {
-		runtimeGOOS = "linux"
-		got := BuildCommentReplyInstructions(issueID, triggerID)
-		for _, want := range []string{
-			"multica issue comment add " + issueID + " --parent " + triggerID + " --content-stdin",
-			"<<'COMMENT'",
-		} {
-			if !strings.Contains(got, want) {
-				t.Errorf("Linux reply instructions missing %q\n---\n%s", want, got)
-			}
-		}
-		if strings.Contains(got, "--content-file") {
-			t.Errorf("Linux reply instructions should not push --content-file\n---\n%s", got)
-		}
-	})
 }
 
-// TestInjectRuntimeConfigWindowsCommentTriggerHasNoStdin asserts the
-// end-to-end CLAUDE.md / AGENTS.md surface for a comment-triggered task on a
-// Windows daemon: the Available Commands section, the Codex-specific
-// paragraph, AND the per-turn reply template all line up on `--content-file`,
-// with no remaining `--content-stdin` directive that would override the
-// Windows fallback. Pins the bug GPT-Boy flagged on PR #2247: the original
-// fix only patched Available Commands, leaving the Codex section and per-turn
-// prompt still mandating stdin.
-func TestInjectRuntimeConfigWindowsCommentTriggerHasNoStdin(t *testing.T) {
+// TestInjectRuntimeConfigCodexWindowsCommentTriggerHasNoStdin asserts the
+// end-to-end AGENTS.md surface for a Codex comment-triggered task on a
+// Windows daemon: the Codex-Specific paragraph + the per-turn reply
+// template are file-first, with no remaining `--content-stdin` directive
+// that would override the Windows file mandate. The Available Commands
+// section is now neutral on every platform (post-rollback of #1795 /
+// #1851), so it is allowed to mention `--content-stdin` as one of the
+// three input modes.
+func TestInjectRuntimeConfigCodexWindowsCommentTriggerHasNoStdin(t *testing.T) {
 	saved := runtimeGOOS
 	t.Cleanup(func() { runtimeGOOS = saved })
 	runtimeGOOS = "windows"
@@ -162,56 +204,36 @@ func TestInjectRuntimeConfigWindowsCommentTriggerHasNoStdin(t *testing.T) {
 		TriggerCommentID: triggerID,
 	}
 
-	for _, provider := range []string{"claude", "codex"} {
-		t.Run(provider, func(t *testing.T) {
-			dir := t.TempDir()
-			if err := InjectRuntimeConfig(dir, provider, ctx); err != nil {
-				t.Fatalf("InjectRuntimeConfig failed: %v", err)
-			}
-			fileName := "CLAUDE.md"
-			if provider != "claude" {
-				fileName = "AGENTS.md"
-			}
-			data, err := os.ReadFile(filepath.Join(dir, fileName))
-			if err != nil {
-				t.Fatalf("read %s: %v", fileName, err)
-			}
-			s := string(data)
+	dir := t.TempDir()
+	if err := InjectRuntimeConfig(dir, "codex", ctx); err != nil {
+		t.Fatalf("InjectRuntimeConfig failed: %v", err)
+	}
+	data, err := os.ReadFile(filepath.Join(dir, "AGENTS.md"))
+	if err != nil {
+		t.Fatalf("read AGENTS.md: %v", err)
+	}
+	s := string(data)
 
-			for _, want := range []string{
-				"multica issue comment add " + issueID + " --parent " + triggerID + " --content-file",
-				"--content-file",
-				"--description-file",
-				"On this Windows host",
-			} {
-				if !strings.Contains(s, want) {
-					t.Errorf("%s missing %q\n---\n%s", fileName, want, s)
-				}
-			}
+	for _, want := range []string{
+		"multica issue comment add " + issueID + " --parent " + triggerID + " --content-file",
+		"--content-file",
+		"--description-file",
+	} {
+		if !strings.Contains(s, want) {
+			t.Errorf("AGENTS.md missing %q\n---\n%s", want, s)
+		}
+	}
 
-			// The Available Commands section, the Codex paragraph, and the
-			// per-turn reply template must NOT end up prescriptively
-			// directing the agent at stdin — that is the exact pattern
-			// Windows shells mangle. Covers GPT-Boy's second blocker on
-			// PR #2247: the original Windows-only fallback was appended
-			// *after* unconditional "MUST pipe via stdin" /
-			// `--description-stdin` lines, leaving agents with
-			// conflicting instructions. We pin the prescriptive
-			// phrasings (not bare flag names) so anti-prescriptive prose
-			// like "do NOT pipe via `--content-stdin`" doesn't trip the
-			// ban.
-			for _, banned := range []string{
-				"--parent " + triggerID + " --content-stdin",
-				"always use `--content-stdin` with a HEREDOC, even for short single-line replies",
-				"MUST pipe via stdin",
-				"use `--description-stdin` and pipe a HEREDOC",
-				"<<'COMMENT'",
-				"Agent-authored comments should always pipe content via stdin",
-			} {
-				if strings.Contains(s, banned) {
-					t.Errorf("%s still steers agent at stdin: %q\n---\n%s", fileName, banned, s)
-				}
-			}
-		})
+	// The per-turn reply template and the Codex-specific paragraph must
+	// not direct the agent at stdin on Windows. Pin prescriptive
+	// substrings rather than bare flag names so anti-prescriptive prose
+	// like "do NOT pipe via `--content-stdin`" doesn't trip the ban.
+	for _, banned := range []string{
+		"--parent " + triggerID + " --content-stdin",
+		"always use `--content-stdin` with a HEREDOC, even for short single-line replies",
+	} {
+		if strings.Contains(s, banned) {
+			t.Errorf("AGENTS.md still steers codex at stdin on Windows: %q\n---\n%s", banned, s)
+		}
 	}
 }

server/internal/daemon/execenv/runtime_config.go

@@ -139,38 +139,22 @@ func buildMetaSkillContent(provider string, ctx TaskContextForEnv) string {
 	b.WriteString("- `multica issue label remove <issue-id> <label-id>` — Detach a label from an issue\n")
 	b.WriteString("- `multica issue subscriber add <issue-id> [--user <name>|--user-id <uuid>]` — Subscribe a member or agent to issue updates (defaults to the caller when neither flag is set; the two flags are mutually exclusive)\n")
 	b.WriteString("- `multica issue subscriber remove <issue-id> [--user <name>|--user-id <uuid>]` — Unsubscribe a member or agent\n")
-	if runtimeGOOS == "windows" {
-		// Windows shells (PowerShell 5.1, cmd.exe) re-encode piped HEREDOC
-		// bytes through the active console codepage before they reach
-		// `multica.exe`, silently replacing characters the codepage cannot
-		// represent with `?`. Steer the agent at `--content-file` /
-		// `--description-file` from the start so there is no contradicting
-		// "MUST pipe via stdin" line for the agent to latch onto. See
-		// issues #2198 / #2236.
-		b.WriteString("- `multica issue comment add <issue-id> --content-file <path> [--parent <comment-id>] [--attachment <path>]` — Post a comment. **On this Windows host, write the body to a UTF-8 file with your file-write tool first, then pass the path via `--content-file` — do NOT pipe via `--content-stdin`.** PowerShell 5.1 and `cmd.exe` re-encode piped bytes through the active console codepage and silently drop non-ASCII characters as `?`, so `中文` arrives as `??`. Use `--parent` to reply to a specific comment; `--attachment` may be repeated.\n")
-		b.WriteString("  - **For comment content, write a UTF-8 file then pass `--content-file <path>`; this preserves multi-line content and non-ASCII bytes (Chinese, Japanese, accents, emoji) verbatim.** Do not use inline `--content` and do not write `\\n` escapes. Example:\n")
-		b.WriteString("\n")
-		b.WriteString("    ```\n")
-		b.WriteString("    # 1. Write the comment body to a UTF-8 file using your file-write tool.\n")
-		b.WriteString("    # 2. Then run:\n")
-		b.WriteString("    multica issue comment add <issue-id> --content-file ./comment.md\n")
-		b.WriteString("    ```\n")
-		b.WriteString("\n")
-		b.WriteString("  - The same rule applies to `--description` on `multica issue create` and `multica issue update` — write the body to a UTF-8 file with your file-write tool and pass `--description-file <path>`. The inline `--description \"...\"` form is acceptable only for ASCII-only single-line text. Do NOT use `--description-stdin` on this host.\n")
-	} else {
-		b.WriteString("- `multica issue comment add <issue-id> --content-stdin [--parent <comment-id>] [--attachment <path>]` — Post a comment. Agent-authored comments should always pipe content via stdin, even for short single-line replies. Use `--parent` to reply to a specific comment; `--attachment` may be repeated.\n")
-		b.WriteString("  - **For comment content, you MUST pipe via stdin; this is mandatory for multi-line content (anything with line breaks, paragraphs, code blocks, backticks, or quotes).** Do not use inline `--content` and do not write `\\n` escapes. Use a HEREDOC instead:\n")
-		b.WriteString("\n")
-		b.WriteString("    ```\n")
-		b.WriteString("    cat <<'COMMENT' | multica issue comment add <issue-id> --content-stdin\n")
-		b.WriteString("    First paragraph.\n")
-		b.WriteString("\n")
-		b.WriteString("    Second paragraph with `code` and \"quotes\".\n")
-		b.WriteString("    COMMENT\n")
-		b.WriteString("    ```\n")
-		b.WriteString("\n")
-		b.WriteString("  - The same rule applies to `--description` on `multica issue create` and `multica issue update` — use `--description-stdin` and pipe a HEREDOC for any multi-line description; the inline `--description \"...\"` form is for short single-line text only.\n")
-	}
+	// Available Commands lists `multica issue comment add` and the
+	// description flags neutrally — three input modes, pick what fits.
+	// The previous "MUST pipe via stdin" mandate (#1795 / #1851) was
+	// originally a Codex-specific fix for codex emitting literal `\n`
+	// escapes inside `--content "..."`, but it landed in this global
+	// section and ended up steering every provider at stdin, which then
+	// burned non-ASCII bytes on Windows shells (issues #2198 / #2236).
+	// Strong "MUST" wording lives in the Codex-Specific section below
+	// where it actually belongs; non-Codex providers handle inline
+	// escaping correctly and can pick whichever flag suits their content.
+	b.WriteString("- `multica issue comment add <issue-id> [--content \"...\" | --content-stdin | --content-file <path>] [--parent <comment-id>] [--attachment <path>]` — Post a comment. Three input modes, pick whichever fits the content:\n")
+	b.WriteString("  - `--content \"...\"` for short single-line text. The CLI decodes `\\n`, `\\r`, `\\t`, `\\\\` so escaped multi-line is OK; do not embed raw newlines in the argument.\n")
+	b.WriteString("  - `--content-stdin` to pipe the body via HEREDOC. Preserves multi-line and special characters verbatim. Cleanest in `bash` / `zsh`.\n")
+	b.WriteString("  - `--content-file <path>` to read a UTF-8 file off disk. Preserves bytes verbatim regardless of the shell — use this on Windows when stdin would re-encode non-ASCII (Chinese, Japanese, accents, emoji) through the console codepage and drop them as `?`.\n")
+	b.WriteString("  - Use `--parent` to reply to a specific comment; `--attachment` may be repeated.\n")
+	b.WriteString("- `multica issue create` / `multica issue update` accept the same three modes for `--description`: `--description \"...\"`, `--description-stdin`, or `--description-file <path>`.\n")
 	b.WriteString("- `multica issue comment delete <comment-id>` — Delete a comment\n")
 	b.WriteString("- `multica label create --name \"...\" --color \"#hex\"` — Define a new workspace label (use this only when the label you need does not exist yet; reuse existing labels via `multica label list` first)\n")
 	b.WriteString("- `multica autopilot create --title \"...\" --agent <name> --mode create_issue [--description \"...\"]` — Create an autopilot\n")
@@ -285,7 +269,7 @@ func buildMetaSkillContent(provider string, ctx TaskContextForEnv) string {
 		b.WriteString("4. **Decide whether a reply is warranted.** If you produced actual work this turn (investigated, fixed, answered a real question), post the result via step 6 — that is a normal reply, not a noise comment. If the triggering comment was a pure acknowledgment / thanks / sign-off from another agent AND you produced no work this turn, do NOT post a reply — and do NOT post a comment saying 'No reply needed' or similar. Simply exit with no output. Silence is a valid and preferred way to end agent-to-agent conversations.\n")
 		b.WriteString("5. If a reply IS warranted: do any requested work first, then **decide whether to include any `@mention` link.** The default is NO mention. Only mention when you are escalating to a human owner who is not yet involved, delegating a concrete new sub-task to another agent for the first time, or the user explicitly asked you to loop someone in. Never @mention the agent you are replying to as a thank-you or sign-off.\n")
 		b.WriteString("6. **If you reply, post it as a comment — this step is mandatory when you reply.** Text in your terminal or run logs is NOT delivered to the user. ")
-		b.WriteString(BuildCommentReplyInstructions(ctx.IssueID, ctx.TriggerCommentID))
+		b.WriteString(BuildCommentReplyInstructions(provider, ctx.IssueID, ctx.TriggerCommentID))
 		b.WriteString("7. Do NOT change the issue status unless the comment explicitly asks for it\n\n")
 	} else {
 		// Assignment-triggered: defer to agent Skills for workflow specifics.

server/internal/daemon/prompt.go

@@ -9,13 +9,16 @@ import (
 
 // BuildPrompt constructs the task prompt for an agent CLI.
 // Keep this minimal — detailed instructions live in CLAUDE.md / AGENTS.md
-// injected by execenv.InjectRuntimeConfig.
-func BuildPrompt(task Task) string {
+// injected by execenv.InjectRuntimeConfig. The provider string is used by
+// comment-triggered tasks: Codex's per-turn reply template needs the
+// platform-aware "stdin or file" variant, every other provider gets a
+// lightweight inline template.
+func BuildPrompt(task Task, provider string) string {
 	if task.ChatSessionID != "" {
 		return buildChatPrompt(task)
 	}
 	if task.TriggerCommentID != "" {
-		return buildCommentPrompt(task)
+		return buildCommentPrompt(task, provider)
 	}
 	if task.AutopilotRunID != "" {
 		return buildAutopilotPrompt(task)
@@ -96,7 +99,7 @@ func buildQuickCreatePrompt(task Task) string {
 // The reply instructions (including the current TriggerCommentID as --parent)
 // are re-emitted on every turn so resumed sessions cannot carry forward a
 // previous turn's --parent UUID.
-func buildCommentPrompt(task Task) string {
+func buildCommentPrompt(task Task, provider string) string {
 	var b strings.Builder
 	b.WriteString("You are running as a local coding agent for a Multica workspace.\n\n")
 	fmt.Fprintf(&b, "Your assigned issue ID is: %s\n\n", task.IssueID)
@@ -117,7 +120,7 @@ func buildCommentPrompt(task Task) string {
 	}
 	fmt.Fprintf(&b, "Start by running `multica issue get %s --output json` to understand your task, then decide how to proceed.\n\n", task.IssueID)
 	fmt.Fprintf(&b, "If you need comment history, `multica issue comment list %s` returns the latest 50 by default — pass --limit or --since to scope older windows. Long issues can have thousands of comments; do not fetch everything blindly.\n\n", task.IssueID)
-	b.WriteString(execenv.BuildCommentReplyInstructions(task.IssueID, task.TriggerCommentID))
+	b.WriteString(execenv.BuildCommentReplyInstructions(provider, task.IssueID, task.TriggerCommentID))
 	return b.String()
 }