Update Package

Update a local Nix package in packages/ to a new version, automatically resolving the new hash.

Parameter Handling

If parameters are missing from $ARGUMENTS, use mcp_question to gather them:

mcp_question({
  questions: [
    {
      question: "Which package do you want to update?",
      header: "Package",
      options: [
        { label: "Enter package name...", description: "e.g., forgejo-mcp, weaviate-cli" }
      ]
    },
    {
      question: "What version should it be updated to?",
      header: "Version",
      options: [
        { label: "Enter version...", description: "e.g., 2.6.0, v3.3.0" }
      ]
    }
  ]
})

Expected $ARGUMENTS format: <packagename> <newversion>

• Example: forgejo-mcp 2.6.0
• Example: weaviate-cli v3.3.0

Steps

1. Read the current package definition

cat packages/<package-name>/default.nix

Identify:

• Current version value
• Hash field location (hash, sha256, vendorHash, cargoHash)
• Fetch method (fetchFromGitHub, fetchurl, fetchzip, fetchgit)

2. Update the version

Edit packages/<package-name>/default.nix:

• Update version = "X.Y.Z"; to the new version
• If version has v prefix in tag but not in version string, strip it

3. Replace hash(es) with placeholder

Replace the existing hash with lib.fakeHash or the placeholder string:

# For sha256/hash fields:
hash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";

# Or use lib.fakeHash:
hash = pkgs.lib.fakeHash;

Common hash fields to update:

• hash or sha256 - Source archive hash
• vendorHash - Go module dependencies (buildGoModule)
• cargoHash - Rust dependencies (buildRustPackage)

4. Run test build to get correct hash

nix build .#<package-name> 2>&1 | grep -E "(got:|hash mismatch)" | head -5

The output will contain the correct hash:

error: hash mismatch in fixed-output derivation
  got:    sha256-CORRECT_HASH_HERE=

5. Update with correct hash

Replace the placeholder with the actual hash from the error output.

6. Handle vendorHash/cargoHash (if applicable)

For Go packages (buildGoModule):

# After fixing source hash, build again to get vendorHash
nix build .#<package-name> 2>&1 | grep "got:"

For Rust packages (buildRustPackage):

# After fixing source hash, build again to get cargoHash
nix build .#<package-name> 2>&1 | grep "got:"

7. Final verification build

nix build .#<package-name>

Ensure build completes successfully.

8. Test the built package

./result/bin/<program> --version
# or
./result/bin/<program> --help

Hash Placeholder Reference

Example: Updating forgejo-mcp

/update-package forgejo-mcp 2.6.0

Before:

version = "2.5.0";
src = pkgs.fetchurl {
  url = "https://codeberg.org/goern/forgejo-mcp/archive/v${version}.tar.gz";
  hash = "sha256-oT2AYvMv0L6CBRNYi0ph6NaQQOMsROqQ8BPTDL8okcI=";
};
vendorHash = "sha256-tOTRbc735TrIZ7fL9EywKLLlePKWMMCeuhbQJGHUuk4=";

Step 1 - Update version and placeholder:

version = "2.6.0";
src = pkgs.fetchurl {
  url = "https://codeberg.org/goern/forgejo-mcp/archive/v${version}.tar.gz";
  hash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
};
vendorHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";

Step 2 - Build, extract source hash:

nix build .#forgejo-mcp 2>&1 | grep "got:"
# got: sha256-NEW_SOURCE_HASH=

Step 3 - Update source hash, build again for vendorHash:

nix build .#forgejo-mcp 2>&1 | grep "got:"
# got: sha256-NEW_VENDOR_HASH=

Step 4 - Update vendorHash, final build:

nix build .#forgejo-mcp
./result/bin/forgejo-mcp --version

Example: Updating Python package

/update-package weaviate-cli 3.3.0

Python packages typically only have one hash (source):

version = "3.3.0";
src = pkgs.fetchFromGitHub {
  owner = "weaviate";
  repo = "weaviate-cli";
  rev = "v${version}";
  hash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
};

Common Fetch Methods

Troubleshooting

Build fails after hash update

• Check if version tag format changed (e.g., v2.0.0 vs 2.0.0)
• Verify URL is still valid for new version
• Check if build system changed (e.g., switched to pyproject.toml)

Multiple hash errors

• Update hashes one at a time
• Source hash first, then vendorHash/cargoHash

Package renamed or moved

• Check upstream for new URL patterns
• Update owner, repo, or URL template as needed

Post-Update Checklist

• Version updated in default.nix
• All hashes updated (source, vendor/cargo if applicable)
• Final build succeeds: nix build .#<package>
• Binary/program works: ./result/bin/<program> --version
• Update README.md if version is mentioned
• Update packages/README.md if needed