diff --git a/apps/cli/src/commands/orchestrator/attach.ts b/apps/cli/src/commands/orchestrator/attach.ts
index 88db341c..5d8ccc30 100644
--- a/apps/cli/src/commands/orchestrator/attach.ts
+++ b/apps/cli/src/commands/orchestrator/attach.ts
@@ -23,6 +23,7 @@ import {
   tildifyPath,
   type UnifiedSession,
 } from '../../lib/session/renderer.js'
+import { formatAvailableSessions } from '../../lib/orchestrator/format.js'
 
 /**
  * Detect the terminal emulator from environment variables.
@@ -137,6 +138,25 @@ export default class OrchestratorAttach extends PromptCommand {
           s.agentName.toLowerCase().includes(needle) ||
           s.sessionId.toLowerCase().includes(needle),
       )
+
+      // Named session not found — surface available sessions instead of a generic "not running"
+      if (filteredOrchestrators.length === 0 && allOrchestrators.length > 0) {
+        const available = formatAvailableSessions(allOrchestrators)
+        const message = `No orchestrator session matches --name "${flags.name}". Available: ${available}`
+        if (jsonMode) {
+          outputErrorAsJson(
+            'NAME_NOT_FOUND',
+            message,
+            createMetadata('orchestrator attach', flags),
+          )
+          return
+        }
+        this.log('')
+        this.log(styles.warning(`No orchestrator session matches --name "${flags.name}".`))
+        this.log(styles.muted(`Available: ${available}`))
+        this.log('')
+        return
+      }
     }
 
     // Group sessions by HQ for scope filtering
diff --git a/apps/cli/src/commands/orchestrator/stop.ts b/apps/cli/src/commands/orchestrator/stop.ts
index 7119a535..2e339c6f 100644
--- a/apps/cli/src/commands/orchestrator/stop.ts
+++ b/apps/cli/src/commands/orchestrator/stop.ts
@@ -22,6 +22,7 @@ import {
   tildifyPath,
   type UnifiedSession,
 } from '../../lib/session/renderer.js'
+import { formatAvailableSessions } from '../../lib/orchestrator/format.js'
 
 export default class OrchestratorStop extends PromptCommand {
   static description = 'Stop the running orchestrator'
@@ -67,13 +68,14 @@ export default class OrchestratorStop extends PromptCommand {
     }
 
     // Always query machine-wide for orchestrators.
-    let orchestrators = collectAllSessions({
+    const allOrchestrators = collectAllSessions({
       hqPathFilter,
       roleFilter: 'orchestrator',
       includeAll: false,
     })
 
     // Optional --name filter
+    let orchestrators = allOrchestrators
     if (flags.name) {
       const needle = flags.name.toLowerCase()
       orchestrators = orchestrators.filter(
@@ -82,6 +84,24 @@ export default class OrchestratorStop extends PromptCommand {
           s.agentName.toLowerCase().includes(needle) ||
           s.sessionId.toLowerCase().includes(needle),
       )
+
+      // Named session not found — surface available sessions
+      if (orchestrators.length === 0 && allOrchestrators.length > 0) {
+        const available = formatAvailableSessions(allOrchestrators)
+        if (jsonMode) {
+          outputErrorAsJson(
+            'NAME_NOT_FOUND',
+            `No orchestrator session matches --name "${flags.name}". Available: ${available}`,
+            createMetadata('orchestrator stop', flags),
+          )
+          return
+        }
+        this.log('')
+        this.log(styles.warning(`No orchestrator session matches --name "${flags.name}".`))
+        this.log(styles.muted(`Available: ${available}`))
+        this.log('')
+        return
+      }
     }
 
     if (orchestrators.length === 0) {
diff --git a/apps/cli/src/lib/orchestrator/format.ts b/apps/cli/src/lib/orchestrator/format.ts
new file mode 100644
index 00000000..099f3682
--- /dev/null
+++ b/apps/cli/src/lib/orchestrator/format.ts
@@ -0,0 +1,18 @@
+import { tildifyPath, type UnifiedSession } from '../session/renderer.js'
+
+/**
+ * Render a one-line summary of available orchestrator sessions for use in
+ * "name not found" error messages.
+ *
+ * Each entry is "<agentName> (<hqPath-or-host>)" joined by ", ".
+ */
+export function formatAvailableSessions(sessions: UnifiedSession[]): string {
+  if (sessions.length === 0) return '(none)'
+  return sessions
+    .map(s => {
+      const location = s.hqPath ? tildifyPath(s.hqPath) : 'host'
+      const tag = s.environment === 'container' ? ', Docker' : ''
+      return `${s.agentName} (${location}${tag})`
+    })
+    .join(', ')
+}
diff --git a/apps/cli/test/unit/orchestrator-format.test.ts b/apps/cli/test/unit/orchestrator-format.test.ts
new file mode 100644
index 00000000..44f09b8f
--- /dev/null
+++ b/apps/cli/test/unit/orchestrator-format.test.ts
@@ -0,0 +1,81 @@
+import { expect } from 'chai'
+import * as os from 'node:os'
+import * as path from 'node:path'
+import { formatAvailableSessions } from '../../src/lib/orchestrator/format.js'
+import type { UnifiedSession } from '../../src/lib/session/renderer.js'
+
+/**
+ * Tests for the formatAvailableSessions helper used by `prlt orchestrator
+ * attach` and `prlt orchestrator stop` to produce a useful "name not found"
+ * error message when --name does not match any running session (PRLT-1271).
+ */
+describe('formatAvailableSessions (PRLT-1271)', () => {
+  const fakeOrchestrator = (overrides: Partial<UnifiedSession>): UnifiedSession => ({
+    id: overrides.id ?? 'orch-1',
+    sessionId: overrides.sessionId ?? 'prlt-orchestrator-hq-main',
+    ticketId: 'orchestrator',
+    agentName: overrides.agentName ?? 'main',
+    status: 'running',
+    role: 'orchestrator',
+    environment: overrides.environment ?? 'host',
+    exists: true,
+    source: overrides.source ?? 'discovered',
+    hqPath: overrides.hqPath,
+    hqName: overrides.hqName,
+    repoPath: overrides.repoPath,
+    startedAt: overrides.startedAt,
+    containerId: overrides.containerId,
+  })
+
+  it('returns "(none)" for an empty session list', () => {
+    expect(formatAvailableSessions([])).to.equal('(none)')
+  })
+
+  it('formats a session with an HQ path using ~ expansion', () => {
+    const home = os.homedir()
+    const hq = path.join(home, 'Projects', 'backend')
+    const out = formatAvailableSessions([
+      fakeOrchestrator({ agentName: 'main', hqPath: hq }),
+    ])
+    expect(out).to.equal('main (~/Projects/backend)')
+  })
+
+  it('marks sessions with no HQ as host', () => {
+    const out = formatAvailableSessions([
+      fakeOrchestrator({ agentName: 'reviewer', hqPath: undefined }),
+    ])
+    expect(out).to.equal('reviewer (host)')
+  })
+
+  it('annotates Docker sessions', () => {
+    const out = formatAvailableSessions([
+      fakeOrchestrator({
+        agentName: 'backend',
+        hqPath: undefined,
+        environment: 'container',
+      }),
+    ])
+    expect(out).to.equal('backend (host, Docker)')
+  })
+
+  it('joins multiple sessions with ", "', () => {
+    const home = os.homedir()
+    const out = formatAvailableSessions([
+      fakeOrchestrator({
+        agentName: 'main',
+        hqPath: path.join(home, 'Projects', 'backend'),
+      }),
+      fakeOrchestrator({
+        agentName: 'backend',
+        hqPath: path.join(home, 'Projects', 'proletariat-hq'),
+      }),
+      fakeOrchestrator({
+        agentName: 'reviewer',
+        hqPath: undefined,
+      }),
+    ])
+    expect(out).to.equal(
+      'main (~/Projects/backend), backend (~/Projects/proletariat-hq), reviewer (host)',
+    )
+  })
+})