diff --git a/.changeset/msgskill-cross-session.md b/.changeset/msgskill-cross-session.md
index 0937cc3f..fb1d099b 100644
--- a/.changeset/msgskill-cross-session.md
+++ b/.changeset/msgskill-cross-session.md
@@ -2,4 +2,6 @@
 "aicodeman": minor
 ---
 
-Codeman agent skill: cross-session messaging integration. The skill now teaches agents to drive claude workers over Claude Code's cross-session messaging (`ListAgents`/`SendMessage`, CLI v2.1.224+) where available: map `ListAgents` rows to Codeman sessions via the `tmux codeman-<id8>` column, deliver multi-line exactly-once task messages (including mid-turn steering of a busy worker), collect results as latched replies instead of polling, and fall back to the HTTP recipes whenever the feature is absent (version, feature flag, telemetry-disabling env vars, Docker/remote cases, non-claude modes). Adds `reference/messaging.md` (ships automatically, the skill installer enumerates `reference/*.md`), fan-out Flow 5 in `reference/recipes.md`, new troubleshooting rows in `reference/endpoints.md`, and safety rules for the shared peer namespace (message only workers you created, no permission laundering in either direction). All mechanics verified live against claude-cli 2.1.226.
+Cross-session messaging integration, two halves. **Workers now carry their Codeman session names as messaging peer names**: local claude spawns pass `--name <session name>` when the installed CLI is 2.1.224+ (the cross-session-messaging release). The gate is fail-closed, since an older claude aborts startup on an unknown option: an unknown or older version yields a spawn command byte-identical to before, the value is allowlist-sanitized before shell interpolation, and docker/remote spawns never carry the flag (their CLI is not the probed binary). Verified end to end on an isolated instance: the worker lists as its session name in `ListAgents`, and its replies arrive tagged `from-name="<session name>"`.
+
+**The Codeman agent skill teaches cross-session messaging**: drive claude workers over `ListAgents`/`SendMessage` where available, map rows to Codeman sessions via the `tmux codeman-<id8>` column, deliver multi-line exactly-once task messages (including mid-turn steering), collect results as latched replies instead of polling, and fall back to the HTTP recipes whenever the feature is absent (version, feature flag, telemetry-disabling env vars, Docker/remote cases, non-claude modes). Adds `reference/messaging.md` (ships automatically, the installer enumerates `reference/*.md`), fan-out Flow 5 in `reference/recipes.md`, troubleshooting rows in `reference/endpoints.md`, and safety rules for the shared peer namespace (message only workers you created, no permission laundering in either direction). All mechanics verified live against claude-cli 2.1.226.
diff --git a/docs/agent-control-plan.md b/docs/agent-control-plan.md
index 8eff78d7..164f2fe5 100644
--- a/docs/agent-control-plan.md
+++ b/docs/agent-control-plan.md
@@ -738,7 +738,22 @@ Verified live (claude-cli 2.1.226, Linux):
   expires unattended (upstream default 5 min), which on a headless worker means the
   message silently dies. The skill's backstop covers it.
 
-Deliberately NOT done: passing `claude --name <sessionName>` at spawn so peers carry
-Codeman session names. The flag exists in 2.1.226, but gating it against older CLIs
-risks the worst regression class (sessions failing to spawn on an unknown flag), so
-it stays a follow-up behind a version/flag probe.
+Follow-up, landed in the same PR: local claude spawns now pass
+`--name <session name>` so peers carry Codeman session names. The gate is
+`buildNameCliArgs()` (session-cli-builder.ts), fail-closed at
+`CLAUDE_NAME_FLAG_MIN_VERSION = 2.1.224`: that is the messaging release, the flag's
+presence there was verified against the installed 2.1.224 binary, and the version
+comes from `getClaudeCliVersion()` (null on probe failure and under vitest), so an
+older or unknown CLI gets a command byte-identical to before. That matters because
+claude aborts startup on an unknown option, which would kill every session spawn.
+The value is allowlist-sanitized (Unicode letters/digits plus ` ._:-`, leading
+dashes stripped so it cannot parse as another option, 64-char cap, empty result =
+flag omitted) before the double-quoted interpolation in `buildSpawnCommand`, and
+only the LOCAL command carries it: the docker/remote builders never see it, since
+their CLI is not the binary the probe measured. E2E on an isolated instance
+(`CODEMAN_INSTANCE`): process cmdline `claude ... --name w9-msgtest`, registry
+`name: "w9-msgtest"`, `ListAgents` lists it under that name, a message round-trip
+works, and its replies arrive tagged `from-name="w9-msgtest"` (a derived-name
+worker's replies carry no `from-name`). A quick-start without `sessionName` has an
+empty Codeman name, so the peer name stays derived: agents should name their
+workers. Tests: `test/name-flag-injection.test.ts`.
diff --git a/skills/codeman/SKILL.md b/skills/codeman/SKILL.md
index 69303a21..c5496d7f 100644
--- a/skills/codeman/SKILL.md
+++ b/skills/codeman/SKILL.md
@@ -414,9 +414,11 @@ The shape, each step verified live (probes, failure modes and safety detail in
 
 1. Spawn + readiness over HTTP, unchanged (§3, Flow 1).
 2. `ListAgents`: find the worker's row by its `tmux codeman-<first 8 of session id>`
-   column; the row's `name [ref]` is the address. No row = messaging is off for that
-   worker (it is feature-flagged even on matching CLI versions, observed live): fall
-   back to the HTTP recipes without complaint.
+   column; the row's `name [ref]` is the address. On Codeman 1.16+ with claude
+   2.1.224+ a worker's peer name is its Codeman session name, so pass `sessionName`
+   in quick-start to pick it; older setups list a name derived from the case folder.
+   No row = messaging is off for that worker (it is feature-flagged even on matching
+   CLI versions, observed live): fall back to the HTTP recipes without complaint.
 3. `SendMessage` the task; first contact must use the `name [ref]` form copied from
    the listing (a bare name errors asking for the ref). End the task with a reply
    instruction: "when done, reply to the sender of this message with one line:
diff --git a/skills/codeman/reference/messaging.md b/skills/codeman/reference/messaging.md
index 3c2ac142..f6f4b35d 100644
--- a/skills/codeman/reference/messaging.md
+++ b/skills/codeman/reference/messaging.md
@@ -61,6 +61,17 @@ your quick-start's `sessionId`. The peer NAME (`msgtest-worker-cf`) is assigned
 Claude Code, derived from the case directory's folder name plus a suffix Codeman does
 not control: never guess it from the case name, read it from the listing.
 
+From Codeman 1.16 a LOCAL claude spawn passes `--name <session name>` when the local
+CLI is 2.1.224+, so a worker's peer name usually IS its Codeman session name
+(verified live: quick-start with `sessionName: "w9-msgtest"` listed as `w9-msgtest`,
+and its messages arrive tagged `from-name="w9-msgtest"`; a derived-name worker's
+messages carry no `from-name`). Name your workers: a quick-start WITHOUT
+`sessionName` leaves the Codeman name empty, so there is nothing to pass and the
+peer name stays derived. The flag is fail-closed (older/unknown CLI omits it) and
+allowlist-sanitized (a name of only unsafe characters is dropped), and docker/remote
+spawns never carry it, which is why the `tmux` column stays the canonical join key
+rather than the name.
+
 Scriptable probe + name lookup, against the registry Claude Code maintains (one JSON
 object per process in `~/.claude/sessions/<pid>.json`):
 
diff --git a/src/mux-interface.ts b/src/mux-interface.ts
index 75f44a63..769705ab 100644
--- a/src/mux-interface.ts
+++ b/src/mux-interface.ts
@@ -97,6 +97,8 @@ export interface RespawnPaneOptions {
   sessionId: string;
   workingDir: string;
   mode: SessionMode;
+  /** Session display name; a respawned claude keeps its `--name` peer name (version-gated, local only). */
+  name?: string;
   niceConfig?: NiceConfig;
   model?: string;
   claudeMode?: ClaudeMode;
diff --git a/src/session-cli-builder.ts b/src/session-cli-builder.ts
index 2461c841..d3fcc3aa 100644
--- a/src/session-cli-builder.ts
+++ b/src/session-cli-builder.ts
@@ -11,6 +11,7 @@
 import type { ClaudeMode, EffortLevel } from './types.js';
 import { isEffortLevel } from './types.js';
 import { getAugmentedPath } from './utils/index.js';
+import { compareVersions } from './utils/dependency-checker.js';
 import { dataPath } from './config/instance.js';
 
 /**
@@ -52,6 +53,53 @@ export function buildEffortCliArgs(effort?: EffortLevel): string[] {
   return effort === 'ultracode' ? ['--settings', '{"ultracode":true}'] : ['--effort', effort];
 }
 
+/**
+ * Minimum Claude CLI version for passing `--name` at spawn. 2.1.224 is the release
+ * that ships cross-session messaging (the feature that makes the peer name matter),
+ * and the flag's presence at exactly this version was verified against the installed
+ * binary (`2.1.224 --help` lists `-n, --name`). The gate MUST stay fail-closed: an
+ * older or unknown CLI aborts startup on an unknown flag ("error: unknown option"),
+ * which would kill every session spawn — so no version means no flag, and the
+ * command line stays byte-identical to the pre-`--name` one.
+ */
+export const CLAUDE_NAME_FLAG_MIN_VERSION = '2.1.224';
+
+/**
+ * Reduce a Codeman session name to a string safe to pass as the Claude CLI
+ * `--name` value. Allowlist, not escaping: keeps Unicode letters/digits (CJK
+ * session names survive) plus ` . _ : -`, which excludes every character that is
+ * special inside the double-quoted shell interpolation buildSpawnCommand uses
+ * (`"`, `$`, backslash, backtick) as well as newlines. Leading dashes/punctuation
+ * are stripped so the value can never be parsed as another CLI option, and the
+ * result is capped at 64 chars. Returns undefined when nothing safe remains —
+ * callers must then omit the flag entirely (never send `--name ""`).
+ */
+export function sanitizeCliSessionName(name?: string): string | undefined {
+  if (!name) return undefined;
+  const cleaned = name
+    .replace(/[^\p{L}\p{N} ._:-]/gu, '')
+    .replace(/\s+/g, ' ')
+    .replace(/^[\s._:-]+/, '')
+    .trim()
+    .slice(0, 64)
+    .trim();
+  return cleaned.length > 0 ? cleaned : undefined;
+}
+
+/**
+ * Build the `--name <session name>` args pair, version-gated and fail-closed.
+ * Returns [] unless the CLI version is KNOWN to support the flag (>= 2.1.224):
+ * a null/undefined version (probe failed, or running under vitest where
+ * getClaudeCliVersion() is hermetically null) yields [], keeping the spawn
+ * command identical to a Codeman without this feature. The name itself is a
+ * SOFT default, exactly like model and effort: `/rename` in-session still works.
+ */
+export function buildNameCliArgs(sessionName: string | undefined, cliVersion: string | null | undefined): string[] {
+  if (!cliVersion || compareVersions(cliVersion, CLAUDE_NAME_FLAG_MIN_VERSION) < 0) return [];
+  const name = sanitizeCliSessionName(sessionName);
+  return name ? ['--name', name] : [];
+}
+
 /**
  * Build args for an interactive Claude CLI session (direct PTY, non-mux fallback).
  *
@@ -60,6 +108,8 @@ export function buildEffortCliArgs(effort?: EffortLevel): string[] {
  * @param model - Optional model override (e.g., 'opus', 'sonnet')
  * @param allowedTools - Optional comma-separated allowed tools list
  * @param effort - Optional effort level, injected via --settings (overridable in-session)
+ * @param sessionName - Optional Codeman session name, passed as `--name` (version-gated)
+ * @param cliVersion - Installed Claude CLI version for the `--name` gate (null = omit the flag)
  * @returns Array of CLI arguments
  */
 export function buildInteractiveArgs(
@@ -67,11 +117,14 @@ export function buildInteractiveArgs(
   claudeMode: ClaudeMode,
   model?: string,
   allowedTools?: string,
-  effort?: EffortLevel
+  effort?: EffortLevel,
+  sessionName?: string,
+  cliVersion?: string | null
 ): string[] {
   const args = [...buildPermissionArgs(claudeMode, allowedTools), '--session-id', sessionId];
   if (model) args.push('--model', model);
   args.push(...buildEffortCliArgs(effort));
+  args.push(...buildNameCliArgs(sessionName, cliVersion));
   return args;
 }
 
diff --git a/src/session.ts b/src/session.ts
index d8658e22..985e74b2 100644
--- a/src/session.ts
+++ b/src/session.ts
@@ -1406,6 +1406,7 @@ export class Session extends EventEmitter {
       sessionId: this.id,
       workingDir: this.workingDir,
       mode: this.mode,
+      name: this._name,
       niceConfig: this._niceConfig,
       model: this._model,
       claudeMode: this._claudeMode,
@@ -1710,7 +1711,15 @@ export class Session extends EventEmitter {
       try {
         // Pass --session-id to use the SAME ID as the Codeman session
         // This ensures subagents can be directly matched to the correct tab
-        const args = buildInteractiveArgs(this.id, this._claudeMode, this._model, this._allowedTools, this._effort);
+        const args = buildInteractiveArgs(
+          this.id,
+          this._claudeMode,
+          this._model,
+          this._allowedTools,
+          this._effort,
+          this._name,
+          getClaudeCliVersion()
+        );
         this.ptyProcess = spawnPtyWithHelperRepair(() =>
           pty.spawn(getClaudeBinaryPath(), args, {
             name: 'xterm-256color',
diff --git a/src/tmux-manager.ts b/src/tmux-manager.ts
index 90b50156..288f55fa 100644
--- a/src/tmux-manager.ts
+++ b/src/tmux-manager.ts
@@ -49,7 +49,7 @@ import {
   type SessionDocker,
   type DockerCommandMode,
 } from './types.js';
-import { buildEffortCliArgs } from './session-cli-builder.js';
+import { buildEffortCliArgs, buildNameCliArgs } from './session-cli-builder.js';
 import {
   buildSshConnectionArgs,
   defaultRemoteCommandForMode,
@@ -73,6 +73,7 @@ import {
   wrapWithNice,
   SAFE_PATH_PATTERN,
   findClaudeDir,
+  getClaudeCliVersion,
   resolveOpenCodeDir,
   resolveCodexDir,
   resolveGeminiDir,
@@ -752,6 +753,20 @@ function buildEffortSettingsFlag(effort?: EffortLevel): string {
   return flag && value ? ` ${flag} '${value}'` : '';
 }
 
+/**
+ * Build the ` --name "<session name>"` shell fragment, or '' when it must be
+ * omitted. Version-gated FAIL-CLOSED in buildNameCliArgs (an older/unknown CLI
+ * aborts startup on an unknown flag, which would kill every claude spawn), and
+ * the value is allowlist-sanitized there, so it contains none of the characters
+ * that are special inside this double-quoted interpolation. The peer name is a
+ * soft default (in-session /rename still wins), which is why this rides the
+ * spawn command rather than any persisted config.
+ */
+function buildClaudeNameFlag(sessionName: string | undefined, cliVersion: string | null): string {
+  const [flag, value] = buildNameCliArgs(sessionName, cliVersion);
+  return flag && value ? ` ${flag} "${value}"` : '';
+}
+
 export function buildSpawnCommand(options: {
   mode: SessionMode;
   sessionId: string;
@@ -764,12 +779,25 @@ export function buildSpawnCommand(options: {
   antigravityConfig?: AntigravityConfig;
   resumeSessionId?: string;
   effort?: EffortLevel;
+  /** Codeman session name, passed to claude as `--name` (version-gated, sanitized; local spawns only). */
+  sessionName?: string;
+  /**
+   * Claude CLI version for the `--name` gate. Omitted = probe the local CLI
+   * (getClaudeCliVersion; null under vitest). Tests inject a value here; the
+   * docker/remote paths never see this builder's output, which is what keeps the
+   * gate measuring the RIGHT binary — the local one.
+   */
+  claudeCliVersion?: string | null;
 }): string {
   if (options.mode === 'claude') {
     // Validate model to prevent command injection
     const safeModel = options.model && /^[a-zA-Z0-9._\-[\]]+$/.test(options.model) ? options.model : undefined;
     const modelFlag = safeModel ? ` --model "${safeModel}"` : '';
     const effortFlag = buildEffortSettingsFlag(options.effort);
+    const nameFlag = buildClaudeNameFlag(
+      options.sessionName,
+      options.claudeCliVersion !== undefined ? options.claudeCliVersion : getClaudeCliVersion()
+    );
     // Use --resume to restore a previous conversation, otherwise --session-id for new sessions.
     // Wrap --resume in a fallback: if it exits non-zero (session not found, corrupt, etc.),
     // fall back to a new session with --session-id so the pane doesn't die.
@@ -777,11 +805,11 @@ export function buildSpawnCommand(options: {
       options.resumeSessionId && /^[a-f0-9-]+$/.test(options.resumeSessionId) ? options.resumeSessionId : undefined;
     const permFlags = buildClaudePermissionFlags(options.claudeMode, options.allowedTools);
     if (safeResumeId) {
-      const resumeCmd = `claude${permFlags} --resume "${safeResumeId}"${modelFlag}${effortFlag}`;
-      const fallbackCmd = `claude${permFlags} --session-id "${options.sessionId}"${modelFlag}${effortFlag}`;
+      const resumeCmd = `claude${permFlags} --resume "${safeResumeId}"${modelFlag}${effortFlag}${nameFlag}`;
+      const fallbackCmd = `claude${permFlags} --session-id "${options.sessionId}"${modelFlag}${effortFlag}${nameFlag}`;
       return `${resumeCmd} || ${fallbackCmd}`;
     }
-    return `claude${permFlags} --session-id "${options.sessionId}"${modelFlag}${effortFlag}`;
+    return `claude${permFlags} --session-id "${options.sessionId}"${modelFlag}${effortFlag}${nameFlag}`;
   }
   if (options.mode === 'opencode') {
     return buildOpenCodeCommand(options.openCodeConfig);
@@ -1789,6 +1817,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       antigravityConfig,
       resumeSessionId,
       effort,
+      sessionName: name,
     });
 
     const config = niceConfig || DEFAULT_NICE_CONFIG;
@@ -2016,6 +2045,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       historyLimit = DEFAULT_TMUX_HISTORY_LIMIT,
       remote,
       docker,
+      name,
     } = options;
     const session = this.sessions.get(sessionId);
     if (!session) return null;
@@ -2050,6 +2080,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       antigravityConfig,
       resumeSessionId,
       effort,
+      sessionName: name,
     });
     const config = niceConfig || DEFAULT_NICE_CONFIG;
     const cmd = wrapWithNice(baseCmd, config);
diff --git a/test/name-flag-injection.test.ts b/test/name-flag-injection.test.ts
new file mode 100644
index 00000000..c0b7dc4e
--- /dev/null
+++ b/test/name-flag-injection.test.ts
@@ -0,0 +1,177 @@
+/**
+ * @fileoverview Tests for the version-gated `--name <session name>` claude spawn flag.
+ *
+ * The flag makes a Codeman claude worker's cross-session-messaging peer name equal
+ * its Codeman session name. The gate MUST be fail-closed: a claude CLI older than
+ * 2.1.224 aborts startup on an unknown option, which would kill every session spawn,
+ * so an unknown/absent version must produce a command byte-identical to the
+ * pre-`--name` one. Covers both spawn paths (buildInteractiveArgs for the direct
+ * PTY fallback, buildSpawnCommand for the tmux pane command) plus the allowlist
+ * sanitizer that keeps the double-quoted shell interpolation injection-free.
+ */
+
+import { describe, it, expect } from 'vitest';
+import {
+  buildInteractiveArgs,
+  buildNameCliArgs,
+  sanitizeCliSessionName,
+  CLAUDE_NAME_FLAG_MIN_VERSION,
+} from '../src/session-cli-builder.js';
+import { buildSpawnCommand } from '../src/tmux-manager.js';
+
+describe('sanitizeCliSessionName', () => {
+  it('passes ordinary Codeman session names through', () => {
+    expect(sanitizeCliSessionName('w1-msgtest-worker')).toBe('w1-msgtest-worker');
+    expect(sanitizeCliSessionName('w18-claudeman: pi')).toBe('w18-claudeman: pi');
+  });
+
+  it('keeps Unicode letters (CJK session names survive)', () => {
+    expect(sanitizeCliSessionName('会话-测试 w2')).toBe('会话-测试 w2');
+  });
+
+  it('strips every character that is special inside double quotes', () => {
+    const cleaned = sanitizeCliSessionName('w1"; $(rm -rf /) `boom` \\ $HOME');
+    expect(cleaned).toBeDefined();
+    // The double-quote interpolation in buildSpawnCommand is only safe because
+    // none of these can survive: " $ ` \ and newlines.
+    expect(cleaned).not.toMatch(/["$`\\\n\r]/);
+    expect(cleaned).not.toMatch(/[();/]/);
+  });
+
+  it('strips leading dashes so the value cannot parse as another CLI option', () => {
+    expect(sanitizeCliSessionName('--resume')).toBe('resume');
+    expect(sanitizeCliSessionName('-x')).toBe('x');
+  });
+
+  it('collapses whitespace and caps length at 64', () => {
+    expect(sanitizeCliSessionName('a   b\t c')).toBe('a b c');
+    const long = 'x'.repeat(200);
+    expect(sanitizeCliSessionName(long)).toHaveLength(64);
+  });
+
+  it('returns undefined when nothing safe remains (flag must be omitted, never --name "")', () => {
+    expect(sanitizeCliSessionName(undefined)).toBeUndefined();
+    expect(sanitizeCliSessionName('')).toBeUndefined();
+    expect(sanitizeCliSessionName('"$`\\')).toBeUndefined();
+    expect(sanitizeCliSessionName('---')).toBeUndefined();
+  });
+});
+
+describe('buildNameCliArgs version gate', () => {
+  it('emits the flag from the minimum version up', () => {
+    // 2.1.224 ships cross-session messaging AND is verified (locally, --help)
+    // to accept --name; the constant must never drift below it.
+    expect(CLAUDE_NAME_FLAG_MIN_VERSION).toBe('2.1.224');
+    expect(buildNameCliArgs('w1-a', '2.1.224')).toEqual(['--name', 'w1-a']);
+    expect(buildNameCliArgs('w1-a', '2.1.226')).toEqual(['--name', 'w1-a']);
+    expect(buildNameCliArgs('w1-a', '2.2.0')).toEqual(['--name', 'w1-a']);
+    expect(buildNameCliArgs('w1-a', '3.0.0')).toEqual(['--name', 'w1-a']);
+  });
+
+  it('FAILS CLOSED below the minimum and on unknown versions', () => {
+    // An older CLI aborts startup on an unknown flag: [] here is what keeps
+    // every spawn alive on old installs.
+    expect(buildNameCliArgs('w1-a', '2.1.223')).toEqual([]);
+    expect(buildNameCliArgs('w1-a', '2.0.999')).toEqual([]);
+    expect(buildNameCliArgs('w1-a', '1.0.128')).toEqual([]);
+    expect(buildNameCliArgs('w1-a', null)).toEqual([]);
+    expect(buildNameCliArgs('w1-a', undefined)).toEqual([]);
+  });
+
+  it('omits the flag entirely when the name sanitizes away or is absent', () => {
+    expect(buildNameCliArgs(undefined, '2.1.226')).toEqual([]);
+    expect(buildNameCliArgs('"$`', '2.1.226')).toEqual([]);
+  });
+});
+
+describe('buildInteractiveArgs with a session name (direct PTY path)', () => {
+  it('appends --name when the version supports it', () => {
+    const args = buildInteractiveArgs(
+      'sid-1',
+      'dangerously-skip-permissions',
+      undefined,
+      undefined,
+      undefined,
+      'w1-a',
+      '2.1.226'
+    );
+    const idx = args.indexOf('--name');
+    expect(idx).toBeGreaterThan(-1);
+    expect(args[idx + 1]).toBe('w1-a');
+  });
+
+  it('omits --name on an old or unknown version', () => {
+    expect(
+      buildInteractiveArgs('sid-1', 'dangerously-skip-permissions', undefined, undefined, undefined, 'w1-a', '2.1.223')
+    ).not.toContain('--name');
+    expect(
+      buildInteractiveArgs('sid-1', 'dangerously-skip-permissions', undefined, undefined, undefined, 'w1-a', null)
+    ).not.toContain('--name');
+    // Version parameter omitted entirely = same fail-closed omission
+    expect(
+      buildInteractiveArgs('sid-1', 'dangerously-skip-permissions', undefined, undefined, undefined, 'w1-a')
+    ).not.toContain('--name');
+  });
+});
+
+describe('buildSpawnCommand with a session name (tmux path)', () => {
+  const base = {
+    mode: 'claude' as const,
+    sessionId: 'aaaabbbb-cccc-dddd-eeee-ffff00001111',
+    claudeMode: 'dangerously-skip-permissions' as const,
+  };
+
+  it('appends a quoted --name when the injected version supports it', () => {
+    const cmd = buildSpawnCommand({ ...base, sessionName: 'w1-msgtest-worker', claudeCliVersion: '2.1.226' });
+    expect(cmd).toContain(' --name "w1-msgtest-worker"');
+  });
+
+  it('stays byte-identical to the flagless command on an old version', () => {
+    const withOld = buildSpawnCommand({ ...base, sessionName: 'w1-a', claudeCliVersion: '2.1.223' });
+    const without = buildSpawnCommand({ ...base, claudeCliVersion: '2.1.223' });
+    expect(withOld).toBe(without);
+    expect(withOld).not.toContain('--name');
+  });
+
+  it('stays byte-identical when the version probe failed (null)', () => {
+    const cmd = buildSpawnCommand({ ...base, sessionName: 'w1-a', claudeCliVersion: null });
+    expect(cmd).toBe(buildSpawnCommand({ ...base, claudeCliVersion: null }));
+  });
+
+  it('defaults fail-closed when no version is injected (vitest probe is hermetically null)', () => {
+    // In production the omitted field resolves through getClaudeCliVersion();
+    // under vitest that is null by design, which doubles as the fail-closed pin.
+    const cmd = buildSpawnCommand({ ...base, sessionName: 'w1-a' });
+    expect(cmd).not.toContain('--name');
+  });
+
+  it('carries the flag in BOTH branches of the resume fallback chain', () => {
+    const cmd = buildSpawnCommand({
+      ...base,
+      sessionName: 'w1-a',
+      claudeCliVersion: '2.1.226',
+      resumeSessionId: 'aaaabbbb-cccc-dddd-eeee-ffff00001111',
+    });
+    const occurrences = cmd.split(' --name "w1-a"').length - 1;
+    expect(cmd).toContain(' || ');
+    expect(occurrences).toBe(2);
+  });
+
+  it('sanitizes a hostile name before interpolation', () => {
+    const cmd = buildSpawnCommand({
+      ...base,
+      sessionName: 'w1"; rm -rf /; echo "',
+      claudeCliVersion: '2.1.226',
+    });
+    const m = cmd.match(/ --name "([^"]*)"/);
+    expect(m).not.toBeNull();
+    // Whatever remains inside the quotes must be inert: no quote/dollar/backtick/
+    // backslash can survive the allowlist, so the shell sees one literal argv.
+    expect(m![1]).not.toMatch(/["$`\\;/]/);
+  });
+
+  it('never adds --name to non-claude modes', () => {
+    const cmd = buildSpawnCommand({ mode: 'shell', sessionId: base.sessionId, sessionName: 'w1-a' });
+    expect(cmd).not.toContain('--name');
+  });
+});