npm install failed with EPERM in the cache — diagnosis

Agent diagnostic brief

Exact symptom

npm install failed with EPERM in the cache

Where it has been observed

npm; dependency installation.

Likely distinct causes

The package lock or dependency graph was corrupt.
The shared default cache had incompatible ownership or permissions.

How to distinguish them

The locked dependency install succeeds with only the npm cache location changed, leaving source and lockfile unchanged.
Check literal EPERM failure against the same bounded execution window.
Check successful install with writable cache against the same bounded execution window.
Check subsequent project verification against the same bounded execution window.

Current approaches

Retry the locked install with a task-scoped writable npm cache (solution-npm-root-owned-cache-eperm, revision 1).

Known obsolete approaches

Do not copy a historical workaround across versions without checking current product behavior.
Do not bypass permissions, security controls, or ownership boundaries merely to suppress the symptom.

Versions and freshness

Observed 2026-09-01; npm cache configuration docs rechecked 2026-09-11
Editorial and primary-source review date: 2026-09-11.

What remains unknown

Behavior outside the stated products, versions, and environments remains unknown.
Independent reproduction by a different operator has not been established.

Deeper evidence

Problem

npm install fails on an unwritable shared cache

Observed symptom

A clean dependency install failed because the default npm cache contained files the current user could not modify, while the repository itself was not the cause.
The historical observation is same-operator evidence and does not establish general prevalence.

Operator goal

Complete install dependencies in isolated worktree without mistaking process success for product acceptance.

Current understanding

A clean dependency install failed because the default npm cache contained files the current user could not modify, while the repository itself was not the cause.
Current primary material was reviewed on 2026-09-11; historical behavior remains bounded to Observed 2026-09-01; npm cache configuration docs rechecked 2026-09-11.

Known limitations

The observed result applies to one sanitized same-operator execution and the stated version boundary, not every environment.
Recheck product documentation and preserve the variable changed before generalizing the diagnosis.

Known negative results

No same-operator execution in this release counts as an independent reproduction.

Primary and recurrence sources

npm cache command documentation
Primary · Primary documentation · Date not supplied · Reviewed 2026-09-11 · Rights: allowed_to_summarize
Current primary material reviewed for Historical Corpus 1: npm cache command documentation.
npm cache configuration
Primary · Primary documentation · Date not supplied · Reviewed 2026-09-11 · Rights: allowed_to_summarize
Current primary material reviewed for Historical Corpus 1: npm cache configuration.

Rights and provenance

Origin

Based on a real operator execution; identifying project details removed.

Rights

State: allowed_to_summarize
Review basis: Owner-authorized factual synthesis of the operator's own execution, independently written from reviewed current primary sources; no transcript expression is published.

Editorial review date

2026-09-11

Known approaches

solution · Revision 1

Retry the locked install with a task-scoped writable npm cache

Production corpus importer · 2026-09-11T10:30:00.000Z
Operator Knowledge for Agents editorial · Historical operator record · Digital source: trainedAlgorithmicMedia · Rights: owned

## Candidate action - Retry the locked install with a task-scoped writable npm cache. Start by capturing the exact failed stage, current product version, and a bounded before-state. Apply only the smallest evidence-backed change, then repeat the original operation and verify its output independently. This is a candidate procedure supported by one same-operator execution, not a universal fix. ## Applicability - Use when the observed signature is: npm install failed with EPERM in the cache. - Observed scope: npm; dependency installation. - Stop if the first failed stage or product boundary differs. ## Procedure - The locked dependency install succeeds with only the npm cache location changed, leaving source and lockfile unchanged. - Retry the same lockfile installation with a fresh task-scoped writable cache. Verify: Installation succeeded without changing home-directory ownership or the lockfile. - Compare the post-change result with the captured before-state and preserve exact readback evidence. ## Limitations - One same-operator execution does not establish cross-operator support. - The procedure does not establish behavior for unreviewed versions, environments, or concurrent state changes. ## Obsolete approaches - Do not reuse a version-specific command or workaround without current documentation review. - Do not infer product completion from a lower-layer command exit alone. ## Negative results - No external or same-operator report was promoted to independent reproduction credit. ## Evidence boundary - Grounded in current primary source records src-npm-cache-config-v11, src-npm-cache-command-v11. - Historical Grade A observation date: 2026-09-01; identifying details removed. - Only immutable manifest executions count as Knowledge for Agents Attempts or Outcomes. ## What remains unknown - Whether the same approach works outside the stated environment remains unknown. - Independent reproduction and universal applicability are not established.

Applicability

State

partial

Text

Applies only when the failed stage matches npm install failed with EPERM in the cache.

Facts

Component: cache directory
Operation: install dependencies in isolated worktree
Protocol: filesystem

Historical date

2026-09-01

Verification grade

Operator relationship

same_operator

Independent reproduction

false

Provenance disclosure

Based on a real operator execution; identifying project details removed.

Pack

Candidate action: Retry the locked install with a task-scoped writable npm cache. Start by capturing the exact failed stage, current product version, and a bounded before-state. Apply only the smallest evidence-backed change, then repeat the original operation and verify its output independently. This is a candidate procedure supported by one same-operator execution, not a universal fix.
Applicability: Use when the observed signature is: npm install failed with EPERM in the cache.
Observed scope: npm; dependency installation.
Stop if the first failed stage or product boundary differs.
Steps: The locked dependency install succeeds with only the npm cache location changed, leaving source and lockfile unchanged.
Retry the same lockfile installation with a fresh task-scoped writable cache. Verify: Installation succeeded without changing home-directory ownership or the lockfile.
Compare the post-change result with the captured before-state and preserve exact readback evidence.
Limitations: One same-operator execution does not establish cross-operator support.
The procedure does not establish behavior for unreviewed versions, environments, or concurrent state changes.
Obsolete approaches: Do not reuse a version-specific command or workaround without current documentation review.
Do not infer product completion from a lower-layer command exit alone.
Negative results: No external or same-operator report was promoted to independent reproduction credit.
Evidence boundary: Grounded in current primary source records src-npm-cache-config-v11, src-npm-cache-command-v11.
Historical Grade A observation date: 2026-09-01; identifying details removed.
Only immutable manifest executions count as Knowledge for Agents Attempts or Outcomes.
What remains unknown: Whether the same approach works outside the stated environment remains unknown.
Independent reproduction and universal applicability are not established.

Rights

State: allowed_to_summarize
Review basis: Original diagnostic procedure synthesized from owner-authorized execution facts and linked current primary sources; no private source code, logs, or transcript expression is published.

Source ids

src-npm-cache-config-v11
src-npm-cache-command-v11