Merge remote-tracking branch 'origin/next' into fix/1327-setuppath-idempotency

fix(#1327 ): sentinel-managed PATH block, default-home-only profile writes
setupPath() guarded its profile append on the binDir value it was about to write, which is blind to accumulation across different Mosaic homes: every wizard run against a fresh temp home appended a permanent # Mosaic block to the operator's real shell profile (1,061 measured appends on sb-it-1-dt, naming 1,058 unique /tmp dirs of which zero exist). - S1/S5: managed block between >>> mosaic begin/end <<< sentinels, rewritten in place, both the POSIX and $env:Path arms - S2: a target home that is not the resolved default skips the profile write entirely; a test harness can no longer touch the operator profile - S3: byte-identical profile across repeated runs (any homes) - S4: legacy unmarked # Mosaic pairs collapse into the managed block S2 arm captured RED against pre-fix code (expected 'skipped', got 'added'), then GREEN post-fix; full suite 1585 passed.
2026-08-20 10:57:01 -05:00 · 2026-08-19 18:24:52 -05:00
12 changed files with 241 additions and 547 deletions
@@ -1,332 +0,0 @@
 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);
  });
 });
@@ -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,
-    { get: vi.fn().mockResolvedValue(null), renew: vi.fn().mockResolvedValue(undefined) } as never,
+    null,
    null,
    { collect: vi.fn().mockResolvedValue(undefined) } as never,
    operatorMemory as never,
@@ -132,8 +132,9 @@ 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,
+    private readonly systemOverride: SystemOverrideService | null,
    @Optional()
    @Inject(PreferencesService)
    private readonly preferencesService: PreferencesService | null,
@@ -708,22 +709,23 @@ 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}${attachmentContext}`;
-    const override = await this.systemOverride.get(sessionId, scope);
+    if (this.systemOverride) {
-    if (override) {
+      const override = await this.systemOverride.get(sessionId, scope);
-      effectiveMessage = `[System Override]\n${override}\n\n${effectiveMessage}`;
+      if (override) {
-      await this.systemOverride.renew(sessionId, scope);
+        effectiveMessage = `[System Override]\n${override}\n\n${effectiveMessage}`;
-      this.logger.debug(`Applied system override for session ${sessionId}`);
+        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) {
@@ -80,10 +80,6 @@ const mockMcpClient = {
  getToolDefinitions: vi.fn(() => []),
 };
 const allowAuthorization = {
  authorize: vi.fn().mockResolvedValue({ allowed: true }),
 };
 function buildService(
  redis: typeof mockRedis | null = mockRedis,
  mcpClient: {
@@ -102,7 +98,6 @@ function buildService(
    null,
    mockChatGateway as never,
    mcpClient as never,
    allowAuthorization as never,
  );
 }
@@ -35,8 +35,9 @@ export class CommandExecutorService {
    @Inject(forwardRef(() => ChatGateway))
    private readonly chatGateway: ChatGateway | null,
    @Inject(McpClientService) private readonly mcpClient: McpClientService,
    @Optional()
    @Inject(CommandAuthorizationService)
-    private readonly authorization: CommandAuthorizationService,
+    private readonly authorization: CommandAuthorizationService | null = null,
  ) {}
  async execute(
@@ -56,13 +57,13 @@ export class CommandExecutorService {
      };
    }
-    const authorization = await this.authorization.authorize(
+    const authorization = await this.authorization?.authorize(
      def,
      payload,
      userId,
      payload.approvalId,
    );
-    if (!authorization.allowed) {
+    if (authorization && !authorization.allowed) {
      return { command, conversationId, success: false, message: authorization.reason };
    }
@@ -170,7 +171,7 @@ export class CommandExecutorService {
    const def = this.registry
      .getManifest()
      .commands.find((command) => command.name === payload.command);
-    if (!def) return null;
+    if (!def || !this.authorization) return null;
    return this.authorization.createApproval(def, payload, scope.userId);
  }
@@ -55,10 +55,6 @@ const mockMcpClient = {
  reconnectServer: vi.fn().mockResolvedValue(undefined),
 };
 const allowAuthorization = {
  authorize: vi.fn().mockResolvedValue({ allowed: true }),
 };
 // ─── Helpers ─────────────────────────────────────────────────────────────────
 function buildRegistry(): CommandRegistryService {
@@ -78,7 +74,6 @@ function buildExecutor(registry: CommandRegistryService): CommandExecutorService
    null, // reloadService (optional)
    null, // chatGateway (optional)
    mockMcpClient as never,
    allowAuthorization as never,
  );
 }
@@ -159,7 +159,6 @@ 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' };
@@ -1,77 +0,0 @@
 # #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.
@@ -292,16 +292,6 @@ 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=$(npm config get prefix 2>/dev/null) || true
@@ -520,93 +520,6 @@ for blocked in LD_PRELOAD= BASH_ENV= MOSAIC_UNTRUSTED_SENTINEL=; do
  contains_literal "$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="$2"
@@ -0,0 +1,152 @@
 /**
 * setupPath profile management (issue #1327, MOSAIC-IMPROVEMENTS 4c / D25).
 *
 * The profile append used to be guarded on the binDir value it was about to
 * write, which is blind to accumulation across different Mosaic homes: every
 * wizard run against a fresh temp home appended a permanent block to the
 * operator's real shell profile (1,061 measured appends on sb-it-1-dt).
 *
 * Arms below map to the requirements:
 *   S1 sentinel-managed block, rewritten in place
 *   S2 a non-default target home never touches the operator profile
 *   S3 byte-identical profile across repeated runs
 *   S4 legacy unmarked `# Mosaic` blocks collapse into the managed block
 *   S5 the Windows ($env:Path) arm shares the same block logic
 */
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 import { mkdtempSync, mkdirSync, writeFileSync, readFileSync, rmSync } from 'node:fs';
 import { join } from 'node:path';
 import { tmpdir, homedir } from 'node:os';
 let profilePathMock: string | null = null;
 vi.mock('../platform/detect.js', () => ({
  getShellProfilePath: (): string | null => profilePathMock,
 }));
 import { setupPath, managedBlockFor, stripLegacyPathBlocks } from './finalize.js';
 // The real resolved default on this host. Tests use it as the comparator a
 // non-default home must fail against, exactly as the wizard would.
 const REAL_DEFAULT_HOME = join(homedir(), '.config', 'mosaic');
 function tempHome(prefix: string): string {
  const dir = join(tmpdir(), prefix);
  mkdirSync(join(dir, 'bin'), { recursive: true });
  return dir;
 }
 describe('setupPath profile management (#1327)', () => {
  let workDir: string;
  let profileFile: string;
  let defaultLikeHome: string;
  let otherHome: string;
  const baseline = '# existing operator content\nexport EDITOR=vim\n';
  beforeEach(() => {
    workDir = mkdtempSync(join(tmpdir(), 'setuppath-spec-'));
    profileFile = join(workDir, '.bashrc');
    writeFileSync(profileFile, baseline, 'utf-8');
    profilePathMock = profileFile;
    defaultLikeHome = tempHome(join(workDir, 'home-a', '.config', 'mosaic'));
    otherHome = tempHome(join(workDir, 'home-b', '.config', 'mosaic'));
  });
  afterEach(() => {
    profilePathMock = null;
    rmSync(workDir, { recursive: true, force: true });
  });
  // S2 — the arm that MUST fail against the pre-fix code: a home that is not
  // the resolved default may not modify the operator profile at all.
  it('does not touch the operator profile when the target home is not the resolved default', () => {
    const action = setupPath(otherHome, REAL_DEFAULT_HOME);
    expect(action).toBe('skipped');
    expect(readFileSync(profileFile, 'utf-8')).toBe(baseline);
  });
  it('returns skipped when no shell profile can be resolved', () => {
    profilePathMock = null;
    const action = setupPath(defaultLikeHome, defaultLikeHome);
    expect(action).toBe('skipped');
  });
  // S1 + S3 — two distinct homes (each run as the resolved default in turn,
  // the shape of two legitimate installs against one operator profile) and
  // repeated runs against the same home both leave exactly one block.
  it('leaves exactly one managed block after runs against two distinct homes', () => {
    const first = setupPath(defaultLikeHome, defaultLikeHome);
    expect(first).toBe('added');
    const second = setupPath(otherHome, otherHome);
    expect(second).toBe('added');
    const content = readFileSync(profileFile, 'utf-8');
    const beginCount = content.split('# >>> mosaic begin >>>').length - 1;
    const endCount = content.split('# <<< mosaic end <<<').length - 1;
    expect(beginCount).toBe(1);
    expect(endCount).toBe(1);
    expect(content).toContain(join(otherHome, 'bin'));
    expect(content).toContain(baseline);
  });
  it('is byte-identical across repeated runs against the same home', () => {
    setupPath(defaultLikeHome, defaultLikeHome);
    const afterFirst = readFileSync(profileFile, 'utf-8');
    const again = setupPath(defaultLikeHome, defaultLikeHome);
    expect(again).toBe('already');
    expect(readFileSync(profileFile, 'utf-8')).toBe(afterFirst);
  });
  // S4 — pre-existing unmarked blocks from the old append logic collapse
  // into the single managed block instead of accumulating beside it.
  it('collapses legacy unmarked # Mosaic blocks into the managed block', () => {
    const legacy =
      '# existing operator content\n' +
      '# Mosaic\n' +
      'export PATH="/tmp/mosaic-dead-wizard-1/bin:$PATH"\n' +
      'export EDITOR=vim\n' +
      '# Mosaic\n' +
      'export PATH="/tmp/mosaic-dead-wizard-2/bin:$PATH"\n';
    writeFileSync(profileFile, legacy, 'utf-8');
    const action = setupPath(defaultLikeHome, defaultLikeHome);
    expect(action).toBe('added');
    const content = readFileSync(profileFile, 'utf-8');
    expect(content).not.toContain('/tmp/mosaic-dead-wizard-1/bin');
    expect(content).not.toContain('/tmp/mosaic-dead-wizard-2/bin');
    expect(content).toContain('export EDITOR=vim');
    expect(content.split('# >>> mosaic begin >>>').length - 1).toBe(1);
    expect(content).toContain(join(defaultLikeHome, 'bin'));
  });
 });
 describe('managed block helpers (#1327)', () => {
  // S5 — the Windows arm shares markers and shape with the POSIX arm.
  it('builds the $env:Path variant inside the same markers', () => {
    const block = managedBlockFor('C:\\Users\\op\\.config\\mosaic\\bin', true);
    expect(block).toContain('# >>> mosaic begin >>>');
    expect(block).toContain('# <<< mosaic end <<<');
    expect(block).toContain('$env:Path = "C:\\Users\\op\\.config\\mosaic\\bin;$env:Path"');
  });
  it('builds the POSIX export variant inside the same markers', () => {
    const block = managedBlockFor('/home/op/.config/mosaic/bin', false);
    expect(block).toContain('# >>> mosaic begin >>>');
    expect(block).toContain('export PATH="/home/op/.config/mosaic/bin:$PATH"');
    expect(block).toContain('# <<< mosaic end <<<');
  });
  it('strips legacy $env:Path pairs on the Windows arm', () => {
    const legacy =
      '# Mosaic\n$env:Path = "C:\\tmp\\dead\\bin;$env:Path"\n' +
      '# Mosaic\n$env:Path = "C:\\tmp\\dead2\\bin;$env:Path"\n' +
      'Write-Host hi\n';
    const stripped = stripLegacyPathBlocks(legacy, true);
    expect(stripped).not.toContain('C:\\tmp\\dead');
    expect(stripped).toContain('Write-Host hi');
  });
 });
@@ -1,11 +1,12 @@
 import { spawnSync } from 'node:child_process';
-import { existsSync, readFileSync, appendFileSync } from 'node:fs';
+import { existsSync, readFileSync, writeFileSync } from 'node:fs';
 import { join } from 'node:path';
 import { platform } from 'node:os';
 import type { WizardPrompter } from '../prompter/interface.js';
 import type { ConfigService } from '../config/config-service.js';
 import type { WizardState } from '../types.js';
 import { getShellProfilePath } from '../platform/detect.js';
 import { DEFAULT_MOSAIC_HOME } from '../constants.js';
 import { ManifestError } from '../framework/manifest.js';
 import {
  getDefaultSkillPaths,
@@ -144,32 +145,87 @@ function runDoctor(mosaicHome: string): DoctorResult {
 type PathAction = 'already' | 'added' | 'skipped';
-function setupPath(mosaicHome: string, _p: WizardPrompter): PathAction {
+const PATH_BLOCK_BEGIN = '# >>> mosaic begin >>>';
-  const binDir = join(mosaicHome, 'bin');
+const PATH_BLOCK_END = '# <<< mosaic end <<<';
-  const currentPath = process.env['PATH'] ?? '';
+const PATH_BLOCK_NOTE = '# Managed by the Mosaic installer; this block is rewritten on install.';
-  if (currentPath.includes(binDir)) {
+/**
-    return 'already';
+ * The managed PATH block written into the operator's shell profile.
 *
 * The block is delimited by begin/end sentinels so any number of installs,
 * against any homes, collapse to exactly one block: the writer replaces the
 * region between the sentinels instead of appending a second copy (#1327).
 */
 export function managedBlockFor(binDir: string, isWindows: boolean): string {
  const exportLine = isWindows
    ? `$env:Path = "${binDir};$env:Path"`
    : `export PATH="${binDir}:$PATH"`;
  return `${PATH_BLOCK_BEGIN}\n${PATH_BLOCK_NOTE}\n${exportLine}\n${PATH_BLOCK_END}\n`;
 }
 /**
 * Remove legacy unmarked `# Mosaic` PATH pairs appended by pre-#1327
 * installs. Only the exact two-line shape this installer used to write is
 * removed; any other `# Mosaic` comment line is left alone.
 */
 export function stripLegacyPathBlocks(content: string, isWindows: boolean): string {
  const legacyExport = isWindows ? /^\$env:Path = ".*;\$env:Path"$/ : /^export PATH=".*:\$PATH"$/;
  const lines = content.split('\n');
  const kept: string[] = [];
  for (let i = 0; i < lines.length; i++) {
    const line = lines[i] ?? '';
    const next = i + 1 < lines.length ? lines[i + 1] : undefined;
    if (line === '# Mosaic' && next !== undefined && legacyExport.test(next)) {
      i += 1;
      continue;
    }
    kept.push(line);
  }
  return kept.join('\n');
 }
 /** Drop the region between the managed-block sentinels, first occurrence. */
 function withoutManagedBlock(content: string): string {
  const beginIdx = content.indexOf(PATH_BLOCK_BEGIN);
  if (beginIdx < 0) return content;
  const endIdx = content.indexOf(PATH_BLOCK_END, beginIdx);
  if (endIdx < 0) return content;
  return content.slice(0, beginIdx) + content.slice(endIdx + PATH_BLOCK_END.length);
 }
 export function setupPath(mosaicHome: string, resolvedDefaultHome: string): PathAction {
  // Never write outside the home under test (#1327 S2): a wizard run against
  // a non-default home (test harnesses, throwaway installs) must not mutate
  // the operator's real shell profile.
  if (mosaicHome !== resolvedDefaultHome) {
    return 'skipped';
  }
  const binDir = join(mosaicHome, 'bin');
  const profilePath = getShellProfilePath();
  if (!profilePath) return 'skipped';
  const isWindows = platform() === 'win32';
-  const exportLine = isWindows
+  const block = managedBlockFor(binDir, isWindows);
    ? `\n# Mosaic\n$env:Path = "${binDir};$env:Path"\n`
    : `\n# Mosaic\nexport PATH="${binDir}:$PATH"\n`;
-  // Check if already in profile
+  let content = '';
  if (existsSync(profilePath)) {
-    const content = readFileSync(profilePath, 'utf-8');
+    content = readFileSync(profilePath, 'utf-8');
-    if (content.includes(binDir)) {
+  }
-      return 'already';
+
-    }
+  // Migration (#1327 S4): legacy unmarked blocks collapse into the managed
  // block, and an existing managed block is rewritten in place rather than
  // appended beside itself (S1/S3).
  const base = stripLegacyPathBlocks(withoutManagedBlock(content), isWindows);
  const trimmed = base.replace(/\n+$/, '');
  const next = trimmed.length === 0 ? block : `${trimmed}\n${block}`;
  if (next === content) {
    return 'already';
  }
  try {
-    appendFileSync(profilePath, exportLine, 'utf-8');
+    writeFileSync(profilePath, next, 'utf-8');
    return 'added';
  } catch {
    return 'skipped';
@@ -286,7 +342,7 @@ export async function finalizeStage(
  }
  // 7. PATH setup
-  const pathAction = setupPath(state.mosaicHome, p);
+  const pathAction = setupPath(state.mosaicHome, DEFAULT_MOSAIC_HOME);
  let summaryShown = false;
  const showSummary = () => {