merge: absorb next into fix/1256-fleet-pane-path-node — bring image pin (cb9a0d1) and 4 days of base drift; no functional change to branch content

Co-authored-by: Ghost <>

.woodpecker/ci.yml

@@ -21,11 +21,19 @@ variables:
   - &enable_pnpm 'corepack enable'
 
 when:
-  # PR + manual CI run on any branch — the pull_request pipeline is the merge gate.
+  # PR + manual CI run on any branch: the pull_request pipeline is the merge
-  # push CI is restricted to protected branches (main) so a feature-branch push no
+  # gate (next is protected and the default branch since 2026-08-19).
-  # longer fires a redundant SECOND pipeline alongside its PR pipeline. This ~halves
+  # Push CI runs on main only. next deliberately runs NO push ci: post-merge
-  # CI load on the storage-constrained runner with zero loss of gating (branch
+  # verification on next is carried by publish.yml's `verify` step
-  # protection requires no push/ci status context; main still gets full push CI).
+  # (pnpm verify:release), which mirrors this pipeline's complete mandatory
+  # set step-for-step, enforced by scripts/verify-release.test.mjs. PR CI
+  # tests the PR HEAD tree (refs/pull/N/head, measured 2026-08-19), not a
+  # merge ref, so if next advances before a merge the landed tree differs
+  # from the tested one; publish verify re-runs the full set on the landed
+  # tree (PGlite path). Measured 2026-08-19: the 21 most recent push events
+  # on next each ran exactly one pipeline (publish), zero ci.
+  # Keeping push ci off next also avoids a redundant second full-suite run
+  # per merge on the storage-constrained runner.
   - event: [pull_request, manual]
   - event: push
     branch: main

apps/gateway/src/__tests__/required-security-wiring.test.ts

@@ -0,0 +1,332 @@
+import { type Type } from '@nestjs/common';
+import { Test, type TestingModule } from '@nestjs/testing';
+import type { SlashCommandPayload } from '@mosaicstack/types';
+import { describe, expect, it, vi } from 'vitest';
+import { AgentService, type AgentSession } from '../agent/agent.service.js';
+import { ProviderService } from '../agent/provider.service.js';
+import { AppModule } from '../app.module.js';
+import { CommandAuthorizationService } from '../commands/command-authorization.service.js';
+import { CommandExecutorService } from '../commands/command-executor.service.js';
+import { CommandsModule } from '../commands/commands.module.js';
+import { CommandRuntimeApprovalVerifier } from '../commands/runtime-approval-verifier.js';
+import { PreferencesModule } from '../preferences/preferences.module.js';
+import { SystemOverrideService } from '../preferences/system-override.service.js';
+
+const fakeDb = {
+  $client: { exec: async (): Promise<void> => {} },
+  execute: async (): Promise<{ rows: unknown[] }> => ({ rows: [] }),
+  select: () => ({
+    from: () => ({
+      where: async (): Promise<Array<{ count: number }>> => [{ count: 1 }],
+    }),
+  }),
+  insert: () => ({ values: async (): Promise<void> => {} }),
+};
+
+const fakeProviderService = {
+  onModuleInit: async (): Promise<void> => {},
+  onModuleDestroy: (): void => {},
+  getRegistry: () => ({ getAvailable: () => [], getAll: () => [], find: () => undefined }),
+  getDefaultModel: () => undefined,
+  listAvailableModels: () => [],
+  listProviders: () => [],
+  getAdapter: () => undefined,
+  getProvidersHealth: () => [],
+};
+
+function compileRealAppGraph(): Promise<TestingModule> {
+  return Test.createTestingModule({ imports: [AppModule] })
+    .overrideProvider('DB_HANDLE')
+    .useValue({ db: fakeDb, close: async (): Promise<void> => {} })
+    .overrideProvider('DB')
+    .useValue(fakeDb)
+    .overrideProvider('STORAGE_ADAPTER')
+    .useValue({
+      name: 'required-security-wiring-test',
+      migrate: async (): Promise<void> => {},
+      close: async (): Promise<void> => {},
+    })
+    .overrideProvider('AUTH')
+    .useValue({})
+    .overrideProvider('BRAIN')
+    .useValue({ conversations: {}, agents: {} })
+    .overrideProvider('LOG_SERVICE')
+    .useValue({})
+    .overrideProvider('MEMORY')
+    .useValue({})
+    .overrideProvider('MEMORY_ADAPTER')
+    .useValue({})
+    .overrideProvider(ProviderService)
+    .useValue(fakeProviderService)
+    .compile();
+}
+
+function providerToken(provider: unknown): unknown {
+  return typeof provider === 'function' ? provider : (provider as { provide?: unknown })?.provide;
+}
+
+interface MaskingConsumer {
+  moduleType: Type<unknown>;
+  token: Type<unknown>;
+  useValue: object;
+}
+
+async function compileWithoutProvider(
+  moduleType: Type<unknown>,
+  missingToken: Type<unknown>,
+  maskingConsumer: MaskingConsumer,
+): Promise<{ error: unknown; moduleRef: TestingModule | undefined }> {
+  const touchedModules = new Set([moduleType, maskingConsumer.moduleType]);
+  const originals = Array.from(touchedModules, (touchedModule: Type<unknown>) => ({
+    moduleType: touchedModule,
+    providers: (Reflect.getMetadata('providers', touchedModule) ?? []) as unknown[],
+    exports: (Reflect.getMetadata('exports', touchedModule) ?? []) as unknown[],
+  }));
+
+  for (const original of originals) {
+    const providers = original.providers.flatMap((provider: unknown): unknown[] => {
+      const token = providerToken(provider);
+      if (original.moduleType === moduleType && token === missingToken) return [];
+      if (original.moduleType === maskingConsumer.moduleType && token === maskingConsumer.token) {
+        return [{ provide: maskingConsumer.token, useValue: maskingConsumer.useValue }];
+      }
+      return [provider];
+    });
+    const exports = original.exports.filter(
+      (exported: unknown): boolean =>
+        original.moduleType !== moduleType || providerToken(exported) !== missingToken,
+    );
+    Reflect.defineMetadata('providers', providers, original.moduleType);
+    Reflect.defineMetadata('exports', exports, original.moduleType);
+  }
+
+  let moduleRef: TestingModule | undefined;
+  let error: unknown;
+  try {
+    moduleRef = await compileRealAppGraph();
+  } catch (caught: unknown) {
+    error = caught;
+  } finally {
+    for (const original of originals) {
+      Reflect.defineMetadata('providers', original.providers, original.moduleType);
+      Reflect.defineMetadata('exports', original.exports, original.moduleType);
+    }
+  }
+  return { error, moduleRef };
+}
+
+async function closeIfCompiled(moduleRef: TestingModule | undefined): Promise<void> {
+  if (moduleRef) await moduleRef.close();
+}
+
+describe('required security wiring — real AppModule startup refusal', () => {
+  it('FL-01 positive control: the real graph compiles when CommandAuthorizationService is bound', async () => {
+    const moduleRef = await compileRealAppGraph();
+    try {
+      expect(moduleRef.get(CommandAuthorizationService, { strict: false })).toBeInstanceOf(
+        CommandAuthorizationService,
+      );
+    } finally {
+      await moduleRef.close();
+    }
+  });
+
+  it('FL-01 negative control: absence read as permission is refused at module compilation', async () => {
+    const { error, moduleRef } = await compileWithoutProvider(
+      CommandsModule,
+      CommandAuthorizationService,
+      {
+        moduleType: CommandsModule,
+        token: CommandRuntimeApprovalVerifier,
+        useValue: {},
+      },
+    );
+    await closeIfCompiled(moduleRef);
+
+    expect(
+      error,
+      'absence read as permission: AppModule compilation accepted a missing CommandAuthorizationService binding',
+    ).toBeInstanceOf(Error);
+    if (!(error instanceof Error)) return;
+    expect(error.message).toContain('CommandExecutorService');
+    expect(error.message).toContain('CommandAuthorizationService');
+  });
+
+  it('FL-11 positive control: the real graph compiles when SystemOverrideService is bound', async () => {
+    const moduleRef = await compileRealAppGraph();
+    try {
+      expect(moduleRef.get(SystemOverrideService, { strict: false })).toBeInstanceOf(
+        SystemOverrideService,
+      );
+    } finally {
+      await moduleRef.close();
+    }
+  });
+
+  it('FL-11 negative control: absence read as permission is refused at module compilation', async () => {
+    const { error, moduleRef } = await compileWithoutProvider(
+      PreferencesModule,
+      SystemOverrideService,
+      {
+        moduleType: CommandsModule,
+        token: CommandExecutorService,
+        useValue: {},
+      },
+    );
+    await closeIfCompiled(moduleRef);
+
+    expect(
+      error,
+      'absence read as permission: AppModule compilation accepted a missing SystemOverrideService binding',
+    ).toBeInstanceOf(Error);
+    if (!(error instanceof Error)) return;
+    expect(error.message).toContain('AgentService');
+    expect(error.message).toContain('SystemOverrideService');
+  });
+});
+
+const actorScope = { userId: 'security-user', tenantId: 'security-tenant' };
+const conversationId = 'security-conversation';
+
+function directExecutorWithoutAuthorization(systemOverrideSet: ReturnType<typeof vi.fn>) {
+  const registry = {
+    getManifest: vi.fn(() => ({
+      version: 1,
+      commands: [
+        {
+          name: 'system',
+          aliases: [],
+          description: 'Set instruction authority',
+          scope: 'agent' as const,
+          execution: 'socket' as const,
+          available: true,
+        },
+      ],
+      skills: [],
+    })),
+  };
+  return new CommandExecutorService(
+    registry as never,
+    { getSession: vi.fn() } as never,
+    { set: systemOverrideSet, clear: vi.fn() } as never,
+    { collect: vi.fn() } as never,
+    null,
+    { agents: {} } as never,
+    null,
+    null,
+    { getServerStatuses: vi.fn(() => []), getToolDefinitions: vi.fn(() => []) } as never,
+    undefined as never,
+  );
+}
+
+function directAgentWithoutSystemOverride(piPrompt: ReturnType<typeof vi.fn>): {
+  service: AgentService;
+  session: AgentSession;
+} {
+  const service = new AgentService(
+    {
+      getDefaultModel: vi.fn(() => null),
+      getRegistry: vi.fn(() => ({})),
+      findModel: vi.fn(),
+      listAvailableModels: vi.fn(() => []),
+    } as never,
+    {} as never,
+    {} as never,
+    { available: false } as never,
+    {} as never,
+    { getToolDefinitions: vi.fn(() => []) } as never,
+    { loadForSession: vi.fn(async () => ({ metaTools: [], promptAdditions: [] })) } as never,
+    undefined as never,
+    null,
+    { collect: vi.fn().mockResolvedValue(undefined) } as never,
+    null,
+  );
+  const session = {
+    id: conversationId,
+    provider: 'test-provider',
+    modelId: 'test-model',
+    piSession: { prompt: piPrompt },
+    listeners: new Set(),
+    unsubscribe: vi.fn(),
+    createdAt: Date.now(),
+    promptCount: 0,
+    channels: new Set(),
+    skillPromptAdditions: [],
+    sandboxDir: process.cwd(),
+    allowedTools: null,
+    userId: actorScope.userId,
+    tenantId: actorScope.tenantId,
+    metrics: {
+      tokens: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+      modelSwitches: 0,
+      messageCount: 0,
+      lastActivityAt: new Date(0).toISOString(),
+    },
+  } as unknown as AgentSession;
+  const internals = service as unknown as { sessions: Map<string, AgentSession> };
+  internals.sessions.set(conversationId, session);
+  return { service, session };
+}
+
+describe('required security wiring — malformed direct absence has zero effects', () => {
+  it('FL-01 refuses command execution before any command effect when authorization is absent', async () => {
+    const systemOverrideSet = vi.fn().mockResolvedValue(undefined);
+    const executor = directExecutorWithoutAuthorization(systemOverrideSet);
+    const payload: SlashCommandPayload = {
+      command: 'system',
+      args: 'authority that must not be stored',
+      conversationId,
+    };
+    let error: unknown;
+
+    try {
+      await executor.execute(payload, actorScope);
+    } catch (caught: unknown) {
+      error = caught;
+    }
+
+    expect
+      .soft(
+        error,
+        'absence read as permission: direct executor accepted missing command authorization',
+      )
+      .toBeInstanceOf(Error);
+    expect
+      .soft(
+        systemOverrideSet,
+        'absence read as permission: command effect occurred without command authorization',
+      )
+      .not.toHaveBeenCalled();
+  });
+
+  it('FL-11 refuses prompt execution before any provider or session effect when system override authority is absent', async () => {
+    const piPrompt = vi.fn().mockResolvedValue(undefined);
+    const { service, session } = directAgentWithoutSystemOverride(piPrompt);
+    let error: unknown;
+
+    try {
+      await service.prompt(conversationId, 'must not reach provider', actorScope);
+    } catch (caught: unknown) {
+      error = caught;
+    }
+
+    expect
+      .soft(
+        error,
+        'absence read as permission: direct session accepted missing system override authority',
+      )
+      .toBeInstanceOf(Error);
+    expect
+      .soft(
+        piPrompt,
+        'absence read as permission: provider prompt occurred without system override authority',
+      )
+      .not.toHaveBeenCalled();
+    expect
+      .soft(
+        session.promptCount,
+        'absence read as permission: session state changed without system override authority',
+      )
+      .toBe(0);
+  });
+});

apps/gateway/src/agent/__tests__/agent-service-ownership.test.ts

@@ -26,7 +26,7 @@ function makeService(operatorMemory: unknown = null): AgentService {
     {} as never,
     { getToolDefinitions: vi.fn(() => []) } as never,
     { loadForSession: vi.fn(async () => ({ metaTools: [], promptAdditions: [] })) } as never,
-    null,
+    { get: vi.fn().mockResolvedValue(null), renew: vi.fn().mockResolvedValue(undefined) } as never,
     null,
     { collect: vi.fn().mockResolvedValue(undefined) } as never,
     operatorMemory as never,

apps/gateway/src/agent/agent.service.ts

@@ -132,9 +132,8 @@ export class AgentService implements OnModuleDestroy {
     @Inject(CoordService) private readonly coordService: CoordService,
     @Inject(McpClientService) private readonly mcpClientService: McpClientService,
     @Inject(SkillLoaderService) private readonly skillLoaderService: SkillLoaderService,
-    @Optional()
     @Inject(SystemOverrideService)
-    private readonly systemOverride: SystemOverrideService | null,
+    private readonly systemOverride: SystemOverrideService,
     @Optional()
     @Inject(PreferencesService)
     private readonly preferencesService: PreferencesService | null,
@@ -709,23 +708,22 @@ export class AgentService implements OnModuleDestroy {
       throw new Error(`No agent session found: ${sessionId}`);
     }
     this.assertSessionScope(session, scope);
-    session.promptCount += 1;
 
     // Channel attachments are untrusted URI references. Preserve exact,
     // authenticated metadata for the agent without treating it as authority.
     const attachmentContext = this.attachmentContext(attachments);
 
-    // Prepend session-scoped system override if present (renew TTL on each turn)
+    // Prepend session-scoped system override if present (renew TTL on each turn).
+    // Required instruction-authority wiring is consulted before session/provider effects.
     let effectiveMessage = `${message}${attachmentContext}`;
-    if (this.systemOverride) {
     const override = await this.systemOverride.get(sessionId, scope);
     if (override) {
       effectiveMessage = `[System Override]\n${override}\n\n${effectiveMessage}`;
       await this.systemOverride.renew(sessionId, scope);
       this.logger.debug(`Applied system override for session ${sessionId}`);
     }
-    }
 
+    session.promptCount += 1;
     try {
       await session.piSession.prompt(effectiveMessage);
     } catch (err) {

apps/gateway/src/commands/command-executor-p8012.spec.ts

@@ -80,6 +80,10 @@ const mockMcpClient = {
   getToolDefinitions: vi.fn(() => []),
 };
 
+const allowAuthorization = {
+  authorize: vi.fn().mockResolvedValue({ allowed: true }),
+};
+
 function buildService(
   redis: typeof mockRedis | null = mockRedis,
   mcpClient: {
@@ -98,6 +102,7 @@ function buildService(
     null,
     mockChatGateway as never,
     mcpClient as never,
+    allowAuthorization as never,
   );
 }
 

apps/gateway/src/commands/command-executor.service.ts

@@ -35,9 +35,8 @@ export class CommandExecutorService {
     @Inject(forwardRef(() => ChatGateway))
     private readonly chatGateway: ChatGateway | null,
     @Inject(McpClientService) private readonly mcpClient: McpClientService,
-    @Optional()
     @Inject(CommandAuthorizationService)
-    private readonly authorization: CommandAuthorizationService | null = null,
+    private readonly authorization: CommandAuthorizationService,
   ) {}
 
   async execute(
@@ -57,13 +56,13 @@ export class CommandExecutorService {
       };
     }
 
-    const authorization = await this.authorization?.authorize(
+    const authorization = await this.authorization.authorize(
       def,
       payload,
       userId,
       payload.approvalId,
     );
-    if (authorization && !authorization.allowed) {
+    if (!authorization.allowed) {
       return { command, conversationId, success: false, message: authorization.reason };
     }
 
@@ -171,7 +170,7 @@ export class CommandExecutorService {
     const def = this.registry
       .getManifest()
       .commands.find((command) => command.name === payload.command);
-    if (!def || !this.authorization) return null;
+    if (!def) return null;
     return this.authorization.createApproval(def, payload, scope.userId);
   }
 

apps/gateway/src/commands/commands.integration.spec.ts

@@ -55,6 +55,10 @@ const mockMcpClient = {
   reconnectServer: vi.fn().mockResolvedValue(undefined),
 };
 
+const allowAuthorization = {
+  authorize: vi.fn().mockResolvedValue({ allowed: true }),
+};
+
 // ─── Helpers ─────────────────────────────────────────────────────────────────
 
 function buildRegistry(): CommandRegistryService {
@@ -74,6 +78,7 @@ function buildExecutor(registry: CommandRegistryService): CommandExecutorService
     null, // reloadService (optional)
     null, // chatGateway (optional)
     mockMcpClient as never,
+    allowAuthorization as never,
   );
 }
 

apps/gateway/src/reload/reload.service.spec.ts

@@ -159,6 +159,7 @@ describe('ReloadService — /reload command sanitizes plugin errors', () => {
       reloadService,
       mockChatGateway as never,
       mockMcpClient as never,
+      { authorize: vi.fn().mockResolvedValue({ allowed: true }) } as never,
     );
 
     const payload: SlashCommandPayload = { command: 'reload', conversationId: 'conv-1' };

docs/scratchpads/1179-required-security-di.md

@@ -0,0 +1,77 @@
+# #1179 — Required security DI wiring
+
+## Objective
+
+Eliminate the shared fail-open defect class **absence read as permission**:
+
+- FL-01: missing `CommandAuthorizationService` must refuse Nest startup and must not permit command effects.
+- FL-11: missing `SystemOverrideService` must refuse Nest startup and must not omit stored instruction authority while allowing provider/session effects.
+
+## Tracking
+
+- Issue: #1179, child of #1156
+- Branch: `fix/1179-required-security-di`
+- Base: `origin/next` at `216cd72226cd9ee17eea461cfe7cd0e010a22f02`
+
+## Plan
+
+1. RED: compile the real `AppModule` graph with each required provider independently removed, with a positive control for each intact binding.
+2. RED: directly exercise each malformed absence path and assert zero command/provider/session effects.
+3. Stop and report RED to the coordinator before production implementation.
+4. After authorization, make both constructor injections required, remove absence-as-permission branches, and update explicit legitimate optional test seams.
+5. Run focused Gateway tests, typecheck, lint, format, build, independent exact-head verification, and focused security review.
+
+## Immutable path fence
+
+Production changes are confined to:
+
+- `apps/gateway/src/commands/command-executor.service.ts`
+- `apps/gateway/src/agent/agent.service.ts`
+
+Tests and task evidence are confined to:
+
+- `apps/gateway/src/__tests__/required-security-wiring.test.ts`
+- existing direct-constructor specs that require explicit required arguments
+- `docs/scratchpads/1179-required-security-di.md`
+
+No files in #1178, #1072, #1080, or #1054 lanes are in scope. `docs/TASKS.md` is orchestrator-owned and will not be modified.
+
+## Budget
+
+No explicit token ceiling was provided. Working assumption: one narrow Gateway security packet; split and stop if either arm requires unrelated module rewiring.
+
+## Progress
+
+- Intake read from #1179 and parent #1156.
+- Base independently resolved from the issue's pre-native-stage ordering and repository `origin/next` ref; branch HEAD verified byte-for-byte against the remote ref.
+- Real consumers and direct constructors inventoried.
+
+## Tests
+
+### RED
+
+- `required-security-wiring.test.ts`: 4 failed, 2 passed before implementation.
+- Both real-graph negative controls showed module compilation accepted the missing target binding.
+- Direct FL-01 showed one unauthorized command effect; direct FL-11 showed one provider prompt and one session counter mutation.
+
+### GREEN
+
+- `required-security-wiring.test.ts`: 6/6 passed.
+- FL-01-only production revert: exactly the two FL-01 test cases failed; all four other cases, including FL-11, passed.
+- FL-11-only production revert: exactly the two FL-11 test cases failed; all four other cases, including FL-01, passed.
+- Full Gateway suite: 74 files passed, 7 skipped; 831 tests passed, 17 skipped.
+- Gateway typecheck: passed.
+- Gateway lint: passed.
+- Gateway build: passed.
+- Changed-file Prettier check: passed.
+
+### Review
+
+- Codex code review: APPROVE, 0 findings.
+- Codex focused security review: risk `none`, 0 findings.
+- Independent exact-head review remains assigned to Scrappy through the coordinator.
+
+## Risks / blockers
+
+- `AgentModule` / `CommandsModule` / `ChatModule` contain a production cycle; the module test therefore uses the real top-level `AppModule` and replaces only storage/network leaves, preserving the target service in each arm while isolating the separate required consumer that would otherwise mask that arm's defect.
+- No broad module rewrite was required.

packages/mosaic/framework/tools/fleet/start-agent-session.sh

@@ -292,6 +292,16 @@ esac
 _build_runtime_bin_prefix() {
   local candidates=()
   if [ -n "$MOSAIC_RUNTIME_BIN" ]; then candidates+=("$MOSAIC_RUNTIME_BIN"); fi
+  # A host with no system Node gets one bootstrapped here by tools/install.sh, which
+  # records it in ~/.profile. The fleet unit runs `env -i ... bash --noprofile --norc`
+  # by design, so ~/.profile is never read and the directory has to be named here.
+  # The npm probe below cannot cover this: it reports a package prefix
+  # (~/.npm-global), never a Node runtime directory. It sits ahead of the npm probe so
+  # the bootstrapped runtime wins on a host that has both — that is the one the installer
+  # verified — while an explicit MOSAIC_RUNTIME_BIN still outranks it.
+  # Runtime binaries are `#!/usr/bin/env node`, so without this the pane resolves the
+  # binary and then dies on `env: 'node': No such file or directory`.
+  candidates+=("$PANE_HOME/.mosaic/node/current/bin")
   if command -v npm >/dev/null 2>&1; then
     local npm_prefix
     npm_prefix=$(npm config get prefix 2>/dev/null) || true

packages/mosaic/framework/tools/fleet/test-start-agent-session.sh

@@ -520,6 +520,93 @@ for blocked in LD_PRELOAD= BASH_ENV= MOSAIC_UNTRUSTED_SENTINEL=; do
   contains_literal "$pane_environment" "$blocked" && fail "runtime pane received $blocked"
 done
 
+# #1256. On a host with no system Node, tools/install.sh bootstraps one into
+# ~/.mosaic/node/ and writes that directory to ~/.profile. The fleet unit runs
+# `env -i ... bash --noprofile --norc`, so ~/.profile is never read — correctly, by
+# design — and _build_runtime_bin_prefix does not list the bootstrap directory. Its
+# `npm config get prefix` branch cannot cover the gap either: the installer points
+# npm's prefix at ~/.npm-global, so that branch contributes the npm-global directory
+# and never the Node one, however it resolves.
+#
+# The property under test is not "the string is in PATH". It is that the pane can
+# EXECUTE a Node-shebang runtime binary — which is what `mosaic` is
+# (`#!/usr/bin/env node`) and what actually failed: measured on a greenfield VM as
+# `env: 'node': No such file or directory` after a clean install that reported success.
+#
+# So this case runs the pane for real and requires it to have run. A PATH-substring
+# assertion would pass on a fix that put the directory in the wrong position, and it
+# would keep passing if the pane later stopped running for some unrelated reason.
+: > "$TMUX_CALLS"
+HOME_NODE="$ROOT/bootstrap-node/.config/mosaic"
+write_generated "$HOME_NODE" "coder-node"
+NODE_PANE_HOME="${HOME_NODE%/.config/mosaic}"
+NODE_BOOTSTRAP_BIN="$NODE_PANE_HOME/.mosaic/node/current/bin"
+mkdir -p "$NODE_BOOTSTRAP_BIN"
+
+# The bootstrapped runtime. It records that it ran, which is the evidence this case
+# turns on: no node reachable from the pane means no marker.
+cat > "$NODE_BOOTSTRAP_BIN/node" <<'SHIM'
+#!/usr/bin/env bash
+set -euo pipefail
+env -0 > "${MOSAIC_HOME:?}/fleet/pane-environment"
+SHIM
+chmod +x "$NODE_BOOTSTRAP_BIN/node"
+
+# write_generated plants its symlinks under the MOSAIC_HOME it is given; here the
+# pane's HOME is the trusted parent, so the pane's view of "installed" is this
+# directory instead. `pi` is what #1241 resolves against PANE_PATH; `mosaic` is what
+# the pane then executes, and it is a Node script — not a bash script that would run
+# anywhere and quietly hide the defect.
+mkdir -p "$NODE_PANE_HOME/.npm-global/bin"
+ln -sf "$FAKE_BIN/pi" "$NODE_PANE_HOME/.npm-global/bin/pi"
+printf '#!/usr/bin/env node\n' > "$NODE_PANE_HOME/.npm-global/bin/mosaic"
+chmod +x "$NODE_PANE_HOME/.npm-global/bin/mosaic"
+
+# The npm branch is modelled ALIVE and still cannot close the gap, which is the
+# stronger statement. An earlier draft of this case tried to model npm as absent —
+# true on a real bootstrap host, where npm lives only in the Node directory — and it
+# refused to run anywhere npm is in the system path, i.e. most machines. It was also
+# the weaker claim: it would have proven only that a dead branch supplies nothing.
+#
+# On a bootstrap host the installer sets npm's prefix to ~/.npm-global. So even with
+# `command -v npm` true and the branch executing, `npm config get prefix` yields the
+# npm-global directory and never the Node one. The gap does not depend on whether
+# that branch runs.
+NODE_LAUNCHER_BIN="$ROOT/bootstrap-node-launcher-bin"
+mkdir -p "$NODE_LAUNCHER_BIN"
+ln -sf "$FAKE_BIN/tmux" "$NODE_LAUNCHER_BIN/tmux"
+ln -sf "$FAKE_BIN/npm" "$NODE_LAUNCHER_BIN/npm"
+
+/usr/bin/env -i \
+  "HOME=$NODE_PANE_HOME" \
+  "PATH=$NODE_LAUNCHER_BIN:/usr/bin:/bin" \
+  "MOSAIC_HOME=$HOME_NODE" \
+  "MOSAIC_TEST_TMUX_CALLS=$TMUX_CALLS" \
+  "MOSAIC_TEST_HOME=$NODE_PANE_HOME" \
+  "MOSAIC_TEST_NPM_PREFIX=$NODE_PANE_HOME/.npm-global" \
+  MOSAIC_TEST_FLEET_OWNER=123e4567-e89b-12d3-a456-426614174000 \
+  MOSAIC_TEST_EXECUTE_PANE=1 \
+  "MOSAIC_TEST_PANE_PID=$$" \
+  "$START" coder-node
+
+[ -f "$HOME_NODE/fleet/pane-environment" ] || \
+  fail "pane could not execute a Node-shebang runtime: $NODE_BOOTSTRAP_BIN is absent from PANE_PATH (#1256)"
+node_pane_environment=$(tr '\0' '\n' < "$HOME_NODE/fleet/pane-environment")
+# Colon-pad and match a whole element. A regex with `(^|:)` after `.*` looks like it
+# does this and does not: an anchor cannot match mid-pattern, so it silently requires
+# a leading colon and rejects the directory in FIRST position — which is where THIS
+# FIXTURE puts it: it runs under `env -i` with no MOSAIC_RUNTIME_BIN, so the bootstrap
+# directory leads. That is a property of the fixture, not of the fix — in general the
+# directory sits second, after MOSAIC_RUNTIME_BIN. The colon padding makes the
+# assertion position-independent either way, which is why it is written this way and
+# not with an anchor. That produced a failure reading "pane ran but PANE_PATH does not
+# carry <dir>" against a PATH whose first element was that dir.
+node_pane_path=":$(printf '%s\n' "$node_pane_environment" | sed -n 's/^PATH=//p' | head -1):"
+case "$node_pane_path" in
+  *":$NODE_BOOTSTRAP_BIN:"*) ;;
+  *) fail "pane ran but PANE_PATH does not carry $NODE_BOOTSTRAP_BIN (PATH=$node_pane_path)" ;;
+esac
+
 write_interaction_generated() {
   local home="$1"
   local agent="$2"